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Tesi sul tema "Ultrasound"
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Boulos, Paul. "Ultrasound imaging of the ultrasound thrombolysis". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1251/document.
Testo completoAbstract (sommario):
Les techniques de thérapie par ultrasons sont apparues très récemment avec la découverte des ultrasons de haute intensité focalisée. La thrombolyse ultrasonore extracorporelle en fait partie et se base sur la destruction mécanique du thrombus causée par la cavitation acoustique. Cependant, c'est un phénomène mal contrôlé. Ainsi, un meilleur contrôle de l'activité de cavitation et sa localisation pendant la thérapie est essentiel pour considérer le développement d'un dispositif thérapeutique. Un prototype a déjà été conçu et amélioré avec une boucle de rétroaction en temps réel afin de contrôler l'activité de puissance de cavitation. Cependant, pour surveiller le traitement en temps réel, un système d'imagerie ultrasonore doit être incorporé dans le dispositif thérapeutique. Il doit être capable de localiser le thrombus, de positionner la focale du transducteur thérapeutique, de contrôler la destruction complète du thrombus et d'évaluer en temps réel l'activité de cavitation. Le travail actuel se focalise principalement sur le développement de techniques d'imagerie ultrasonore passive utilisées pour reconstituer les cartographies d'activité de cavitation. Différents algorithmes de formation de voies ont été examinés et validés par des simulations de sources ponctuelles, des expériences in vitro sur fil et des expériences de cavitation dans une cuve d'eau. Il a été démontré que l'algorithme de formation de voie le plus précis pour la localisation du point focale de cavitation est la technique de cartographie passive acoustique pondérée avec le facteur de cohérence de phase (PAM-PCF). En outre, des tests in vivo sur un modèle animal d'ischémie des membres aigus ont été évalués. Enfin, certaines optimisations du système d'imagerie développé précédemment ont été réalisées comme l'imagerie 3D, l'implémentation en temps réel et l'imagerie hybride combinant l'imagerie active anatomique avec les cartographies de cavitation passiveUltrasound therapy techniques emerged very recently with the discovery of high intensity focused ultrasound (HIFU) technology. Extracorporeal ultrasound thrombolysis is one of these promising innovative low-invasive treatment based on the mechanical destruction of thrombus caused by acoustic cavitation mechanisms. Yet, it is a poorly controlled phenomenon and therefore raises problems of reproducibility that could damage vessel walls. Thus, better control of cavitation activity during the ultrasonic treatment and especially its localization during the therapy is an essential approach to consider the development of a therapeutic device. A prototype has already been designed and improved with a real-time feedback loop in order to control the cavitation power activity. However, to monitor the treatment in real-time, an ultrasound imaging system needs to be incorporated into the therapeutic device. It should be able to first spot the blood clot, to position the focal point of the therapy transducer, control the proper destruction of the thrombus, and evaluate in real-time the cavitation activity. Present work focusses mainly on the development of passive ultrasound techniques used to reconstruct cavitation activity maps. Different beamforming algorithms were investigated and validated through point source simulations, in vitro experiments on a wire, and cavitation experiments in a water tank. It was demonstrated that an accurate beamforming algorithm for focal cavitation point localization is the passive acoustic mapping weighted with the phase coherence factor (PAM-PCF). Additionally, in vivo testing on an animal model of acute limb ischemia was assessed. Finally, some optimizations of the previous developed imaging system were carried out as 3D imaging, real-time implementation, and hybrid imaging combining active anatomical imaging with passive cavitation mapping
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Poggenpoel, Elizabeth J. "Primary obstetric ultrasound : comparing a detail ultrasound only protocol with a booking ultrasound protocol". Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4326.
Testo completo
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Mulic-Lutvica, Ajlana. "Postpartum Ultrasound". Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7830.
Testo completo
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Mercier, Laurence. "Review of ultrasound probe calibration techniques for 3D ultrasound". Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81555.
Testo completoAbstract (sommario):
Three-dimensional (3D) ultrasound is an emerging new technology with numerous clinical applications like measuring the volume of the prostate, monitoring fetal development, or evaluating brain shift during neurosurgery. Ultrasound probe calibration is an obligatory step in order to build 3D volumes from 2D images acquired in a freehand ultrasound system. The role of calibration is to find the transformation that relates the image plane to a sensor attached on the probe. This thesis is a comprehensive review of what has been published in the field of ultrasound probe calibration for 3D ultrasound. The thesis covers the topics of tracking technologies, ultrasound image acquisition, phantom design, speed of sound issues, feature extraction, least-squares minimization, temporal calibration, calibration evaluation techniques and phantom comparisons. The calibration phantoms and methods have also been classified in tables to give a better overview of the existing methods.
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Curra, Francesco Pasquale. "Medical ultrasound algorithm for noninvasive high intensity ultrasound applications /". Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/8006.
Testo completo
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Zhang, Xin. "Etude du vieillissement thermique de revêtements de peinture sur plaque par réflectométrie ultrasonore". Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20234.
Testo completoAbstract (sommario):
La recherche de critères de vieillissement des revêtements de protection sur le long terme est nécessaire dans de nombreuses configurations industrielles. Ce travail présente l'étude de l'évolution de l'élasticité de revêtements de peinture sur plaque métallique par réflectométrie ultrasonore pour détecter de façon non destructive l'endommagement induit lors de tests de vieillissement thermique accéléré. La modélisation du pouvoir réflecteur permet d'identifier, dans une certaine gamme de fréquence, un mode particulier dont la valeur de l'angle critique est préférentiellement sensible à la rigidité de la couche en bon accord avec les tests réalisés sur des revêtements de 100µm de peinture sur plaque d'acier. Cette méthode est appliquée sur des échantillons étuvés à 80°C et 110°C durant 4000 heures. En fonction de la température, la mesure quotidienne de la position de cet angle critique permet de suivre le temps nécessaire au séchage complet des revêtements suite à l'évaporation du solvant. Au-delà, les variations de cette position angulaire indiquent, pour les modules élastiques de la peinture, une légère augmentation de moins de 2%. L'altération de la structure chimique détectée par mesures de température de transition vitreuse et de concentration de certains marqueurs (FTIR) se traduit donc par des modifications faibles d'élasticité nécessitant une résolution angulaire inférieure à 0,1°. Pour mieux différencier la rigidité de ces échantillons suite au vieillissement thermique, la sensibilité nécessaire est obtenue en réalisant une excursion en température autour de l'ambiante de quelques °C durant les mesures de réflectométrieThe determination of paint coating's ageing criteria after long term service is necessary in many industrial configurations. In this work, we have studied by ultrasonic reflectometry the evolution of the elasticity of paint coated on a metallic plate in order to detect in a non destructive way the damage induced by thermal accelerated ageing tests. The simulation of the reflection coefficient identifies a particular mode whose critical angle is preferentially sensitive to the elasticity of the paint layer in a particular range of frequency. This result is in agreement with experimental tests performed on 100 µm thick paint coated on a steel plate. These samples are heated at 80°C and 110°C during 4000 hours. The everyday measurement of the evolution of the critical angle allows the identification of the time necessary to reach the complete drying of the paint coating. This parameter depends on the heating temperature. The total variations of these critical angular positions indicate a small increase less than 2% of the paint's elasticity moduli. In parallel, the change of the chemical structure is detected by the measurement of the glass transition temperature and the concentration of some markers identified by FTIR. This chemical change is linked to a small variation of elasticity implying an angular resolution less than 0.1°. For an easier differentiation of the rigidity of these thermally aged coatings, an enhanced sensibility is obtained by changing the temperature during the reflectometry measurements
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Eggebø, Torbjørn Moe. "Ultrasound and labour". Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for laboratoriemedisin, barne- og kvinnesykdommer, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-11984.
Testo completoAbstract (sommario):
2.1 Innledning Alle kvinner ønsker seg en ukomplisert fødsel, men komplikasjoner kan oppstå plutselig og uventet. I følge Verdens Helseorganisasjon trenger 15% av de gravide kyndig hjelp under svangerskap eller fødsel. Før fødselen starter er det viktig å vite hvordan fosteret er orientert i forhold til mor. Leiet vurderes som lengdeleie, tverrleie eller skråleie. Posisjonen beskriver hvordan fosteret er orientert fram, bak, til høyre eller venstre inne i livmoren, og presentasjon beskriver den delen av fosteret som er dypest i fødselskanalen. Nakken til fosteret kan være bøyd (flektert) eller strukket (ekstendert). Fødselskanalen hos mennesket har en bøyd og uregelmessig form, og fosteret må derfor rotere for å kunne passere. De fire kardinalbevegelsene hos et foster med bakhodepresentasjon er fleksjon av hodet, rotasjon gjennom kanalen, ekstensjon i utskjæringen og rotasjon i det skuldrene passerer utgangen. Ved slutten av svangerskapet blir livmorhalsen kortere, og under fødselen blir den avflatet før den åpner seg. Fosterets nivå i fødselskanalen relateres vanligvis til prosessus spinosus. Fødselshjelperne bruker tradisjonelt hendene til å vurdere forholdet mellom foster og mor, men studier har vist stor variasjon mellom ulike undersøkere. Galileo Galilei har sagt: «Mål det som er målbart, og prøv å gjøre målbart det som ennå ikke er det.» Hensikten med denne avhandlingen er å vurdere nytten av ultralydmålinger like før fødselen starter. 2.2 Materiale og metode Vi undersøkte to grupper gravide kvinner. Først undersøkte vi 152 kvinner med ett foster i hodeleie, ingen tidligere keisersnitt og vannavgang etter svangerskapsuke 37 (studie 1 og 2). Vi vurderte fosterhodets posisjon og grad av fleksjon i nakken med transabdominal ultralydundersøkelse. Deretter utførte vi en transperineal ultralydundersøkelse og målte avstanden til indre mormunn og lengden av livmorhalsen i sagittalplan. Vi brukte den korteste avstanden fra fosterhodet til perineum i frontalplan som et mål på fosterhodets nivå i fødselskanalen. Andre gruppe bestod av kvinner som kom til fødselsinduksjon (studie 3 og 4). Inklusjonskriterier var ett foster i hodeleie, ingen tidligere keisersnitt og svangerskapslengde over 37 uker. 710 kvinner hadde indusert fødsel i studieperioden, og 275 ble inkludert i undersøkelsen. Fosterhodets posisjon og nivå ble vurdert på samme måte som beskrevet ovenfor. Vi målte livmorhalsens lengde og vinkel ved vaginal undersøkelse. En fødselshjelper som ikke kjente resultatene av ultralydundersøkelsene, utførte Bishop scoringen. 2.3 Studie 1 Occiput posterior posisjon under fødselen er forbundet med økt risiko for stans i fødselsforløpet, operative forløsninger og rifter. Det diskuteres om occiput posterior posisjon ved fødselen skyldes occiput posterior før start av fødselen eller en unormal rotasjon gjennom fødselskanalen. Hensikten med studien var å vurdere nytten av en transabdominal ultralydundersøkelse før start av fødselen hos kvinner med vannavgang etter uke 37. 40 av 152 foster hadde occiput posterior posisjon før fødselen, og hos 34 (85%) av disse roterte hodet til occiput anterior innstilling i løpet av fødselen. Fosterhodets posisjon før fødselen kunne predikere occiput posterior posisjon ved fødselen med sensitivitet 60%; 95% CI 26-88, falsk positiv rate 24%; 95% CI 17-32, positiv prediktiv verdi 15%; 95% CI 6-30, negativ prediktiv verdi 96%; 95% CI 91-99 og likelihood ratio (LR) 2,5. 11 gravide hadde foster med ekstendert nakke før start av fødselen. Av disse fødte sju spontant, tre kvinner med keisersnitt og én ble forløst med vakuum. Det var ingen signifikant sammenheng mellom fosterhodets posisjon eller grad av nakkefleksjon før start av fødselen og utfallet av fødselen. Vi konkluderte med at en transabdominal ultralydundersøkelse hos kvinner med vannavgang har liten nytteverdi. 2.4 Studie 2 Transperineal ultralydundersøkelse er en lite brukt undersøkelsesmetode. Vi brukte utgangen av fødselskanalen som referanselinje for å vurdere fosterhodets nivå. Så vidt vi vet har ikke denne metoden vært evaluert tidligere. Hensikten med studien var å undersøke om resultatene av en transperineal ultralydundersøkelse kan predikere tid fra vannavgang til fødsel, og predikere sannsynligheten for en operativ forløsning. Undersøkelse av livmorhalsens lengde i sagittalplanet var teknisk mislykket hos 16% av kvinnene og var derfor lite hensiktsmessig. Undersøkelse av fosterhodets nivå i frontalplanet var vellykket hos alle. Kvinner med kort avstand (< 45 mm) fra fosterhodet til perineum, hadde signifikant færre keisersnitt, mindre bruk av epiduralanalgesi, kortere tid fra vannavgang til fødsel og kortere tid i aktiv fødsel enn de med lang avstand fra fosterhodet til perineum. Lang avstand predikerte operativ forløsning (keisersnitt eller operativ vaginalforløsning) med sensitivitet på 83%; 95% CI 67-94, falsk positiv rate 59%; 95% CI 49-68, positiv prediktiv verdi 31%; 95% CI 22-41, negativ prediktiv verdi 89%; 95% CI 77-96 og LR 1,4. Ultralydmåling av fosterhodets nivå kan være nyttig for å vurdere om kvinner med vannavgang bør vente på spontan fødsel eller tilbys tidlig induksjon. 2.5 Studie 3 Hensikten med denne studien var å evaluere fosterhodets nivå, målt med ultralyd, som en prediktiv faktor for fødselsforløpet ved induserte fødsler. Vi sammenlignet målingen med paritet, BMI, Bishop score og ultralydundersøkelse av fosterhodets posisjon, livmorhalsens lengde og vinkel. 13% ble forløst med keisersnitt. Paritet var den beste faktoren for å predikere fødselsmåte. Den korteste avstanden fra fosterhodet til perineum predikerte vaginal fødsel med 62%; 95% CI 52-71% (p = 0,03) av arealet under kurven i en ROC (receiver-operating characteristics) kurve. Lengden av livmorhalsen predikerte vaginal fødsel med 61%; 95% CI 51-71% (p = 0,03), vinkelen til livmorhalsen med 63%; 95% CI 52-74% (p = 0,02) og Bishop score med 61%; 95% CI 52-70% (p = 0,03) av arealet under kurven. Best resultat fikk vi for cut-off verdiene: hode-perineum avstand ≤ 40 mm, lengde av livmorhalsen ≤ 25 mm og bakre vinkel av livmorhalsen > 90 grader. De samme faktorene hadde også signifikant betydning for sannsynligheten for å føde innen 24 timer etter induksjon. Fosterhodets posisjon hadde ingen prediktiv verdi for fødselsforløpet. 2.6 Studie 4 Bishop score består av faktorene lengde, åpning, posisjon og konsistens av livmorhalsen, og fosterhodets nivå i fødselskanalen. I denne studien sammenlignet vi enkeltfaktorene i Bishop score med tilsvarende ultralydmålinger, og hvordan man kan kombinere ultralydmålinger og palpasjonsfunn. Vi fant moderat korrelasjon mellom palpasjon og ultralyd til å vurdere lengden av livmorhalsen (r = 0,54), svak korrelasjon i vurdering av fosterhodets nivå i fødselskanalen (r = 0,23) og ingen korrelasjon i vurdering av livmorhalsens vinkel eller posisjon (r = 0,03). Fosterhodets nivå og livmorhalsens lengde og åpning var de tre viktigste faktorene for å predikere fødselsforløpet. I klinisk praksis er det vanlig å kombinere faktorer i et scoringssystem. Bishop score er et subjektivt og komplisert system med score fra 0 til 13, og vi foreslår å bruke et nytt scoringssystem fra 0 til 3 der fosterhodets nivå og livmorhalsens lengde måles med ultralyd og åpningen vurderes med palpasjon. Faktorer kan også kombineres ved hjelp av Bayes teorem. A priori sannsynlighet for vaginal fødsel etter induksjon er 88%. LR for vaginal fødsel var 3,5 hvis avstanden fra fosterhodet til perineum var ≤ 40 mm. A posteriori sannsynlighet for vaginal fødsel blir dermed 96%. Vi anbefaler å evaluere kombinasjon av prediktive faktorer i nye studier. 2.7 Tanker om framtida I moderne medisinske forskning har metananalyser av randomiserte kontrollerte studier størst betydning. Humanistisk vitenskapsteori prioriterer erfaringskunnskap høyere. Erfaringskunnskap har lang tradisjon innenfor faget fødselshjelp, og det er viktig å ta vare på denne tradisjonen. Gammel og ny kunnskap må sammenlignes og evalueres. Pasientverdier har fått større betydning i moderne medisin. Klinikere kan ikke lenger bestemme for pasientene, men heller være rådgivere . God kunnskap er viktig for å kunne informere de fødende om sannsynlig forløp av fødselen. Filosofen William of Ockham (1285-1349) har uttalt: «Bruk alltid den enkleste av likeverdige metoder.» Ressursene i helsevesenet er begrenset, og leger får ofte et etisk dilemma om de skal prioritere den enkelte pasient eller sykehusets økonomi. Det vil derfor bli viktig å finne undersøkelsesmetoder som er enkle å bruke, nyttige for pasientene og som samtidig er kostnadseffektive. Ultralydundersøkelser har en sentral rolle i svangerskapsomsorgen. I denne avhandlingen har vi vurdert nytteverdien av ultralydmålinger like før fødselen starter. De samme undersøkelsesmetoder kan også brukes under fødselen. På dette området er det behov for mer forskning. Redaktøren i Ultrasound in Obstetrics and Gynecology har uttalt: «We will move from obstetric ultrasound to ultrasonographic obstetrics.» Kanskje vil ultralydundersøkelser i forbindelse med fødselen bli like viktige som de i dag er i svangerskapsomsorgen.
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Mawhinney, Ian Nicholas. "Bone and ultrasound". Thesis, Queen's University Belfast, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335942.
Testo completo
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Dhawale, Paritosh Jayant. "Volumetric intracoronary ultrasound". Case Western Reserve University School of Graduate Studies / OhioLINK, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=case1057677172.
Testo completo
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Jeon, Minjee. "Ultrasound—Re:viewing Bodies". VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5434.
Testo completoAbstract (sommario):
A medical evaluation of physical impairment imposes the additional burden of “labeling” the patient with the condition. The binary nature of the normal versus abnormal label emphasizes difference and can lead to trauma. Understanding differences, however, can lead to the generation of new forms and thus, more sensitive differentiation and representation. Tension is created by exploring different bodily forms—a dialectic between form and essence. I am designing a space that visualizes and illuminates difference as a source of trauma and amplifying the tension by comparing figures that represent varying degrees of normalcy. This forms a critique of idealized form and creates a context for people unaffected by this type of trauma to reflect on possible realities outside of their assumptions of normality.
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Vadalma, Anthony. "Smartphone ultrasound imaging". Thesis, Queensland University of Technology, 2020. https://eprints.qut.edu.au/204111/1/Anthony_Vadalma_Thesis.pdf.
Testo completoAbstract (sommario):
This research project titled 'Smartphone Ultrasound Imaging' aimed to develop an affordable, portable and single handed ultrasound-imaging device to be used in hospitals, developing world nations as well as rural and remote Australia. This study examined the feasibility of combining a conventional smartphone with an ultrasound probe into one single device. All necessary ultrasound signal processing components were built and smartphone applications were developed to successfully transmit data either via Bluetooth or Wi-Fi from the ultrasound to the smartphone.
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Boissenot, Tanguy. "Nanocapsules théranostiques pour l’imagerie par IRM-19F et la libération contrôlée par ultrasons". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS078.
Testo completoAbstract (sommario):
Nous avons développé des nanocapsules théranostiques combinant à la fois une fonction diagnostic d’amélioration de la détection tumorale et une fonction thérapeutique pour les traiter. Ces nanocapsules sont composées d'une enveloppe de polymère de PLGA-PEG et d'un noyau de bromure de perfluorooctyle, un liquide perfluoré, permettant la détection par IRM-19F. Nous avons encapsulé à l’intérieur de ces nanocapsules du paclitaxel, un anticancéreux de la classe des taxanes. L’encapsulation permet de s’affranchir de l’utilisation de Cremophor®, un tensioactif utilisé dans la formulation commerciale de Taxol® qui peut entrainer des effets indésirables graves pouvant aller jusqu’au choc anaphylactique. L’encapsulation a été optimisée en faisant varier les paramètres de formulation pour empêcher la recristallisation du paclitaxel et l'agrégation des nanocapsules. La formulation optimisée a été testée in vitro sur des cellules de cancer du côlon CT-26 et a montré une cytotoxicité équivalente à celle du Taxol®. La pharmacocinétique et la biodistribution ont été évaluées chez des souris nudes porteuse de tumeurs CT-26 en comparaison au Taxol®. Pour les nanocapsules, les paramètres pharmacocinétiques sont améliorés : on observe une circulation prolongée et une meilleure accumulation au niveau des tumeurs, telles que confirmées par IRM-19F. L’efficacité antitumorale des nanocapsules est améliorée par rapport au PBS et Taxol®. L’influence d’ultrasons a aussi été étudié et a permis d’améliorer le ciblage et de ralentir la croissance tumorale. Des études in vitro ont montré que ce ralentissement est lié à l'hyperthermie modérée induite qui favorise la perfusion tumorale et l’extravasation vasculaire et améliore l’accumulation du principe actif à l'intérieur de la tumeurWe have developed theranostic nanocapsules combining a diagnostic moiety to improve tumor detection and a therapeutic moiety to treat them. These nanocapsules are composed of a polymer shell of PLGA-PEG and a core of a perfluorocarbon, namely perfluorooctyl bromide, detectable by 19F-MRI. Paclitaxel, a cytotoxic drug, was encapsulated in an attempt to reduce side-effects associated with excipients such as Cremophor® used in the commercial formulation (Taxol®). We optimized encapsulation of paclitaxel into nanocapsules by varying formulation parameters to prevent or limit paclitaxel recrystallization and nanocapsule aggregation. The optimized formulation was tested in vitro on CT-26 colon cancer cells and showed similar cytotoxicity as compared with Taxol®. Paclitaxel pharmacokinetics and biodistribution were evaluated in nude mice bearing CT-26 tumors comparing nanocapsules with Taxol®. For nanocapsules, pharmacokinetic parameters are improved leading to a longer circulation and resulting in an enhanced accumulation in tumors, as confirmed by 19F-MRI. In terms of efficacy, this enhanced passive targeting allows a slower tumor growth in animals treated with paclitaxel-loaded nanocapsules compared to PBS and Taxol®. Ultrasound were also used to further improve tumor targeting. We showed that when applying a safe ultrasound sequence, tumor growth was slower on our tumor model. In vitro studies showed that this decreased growth is due to mild hyperthermia favoring tumor perfusion and vascular extravasation leading in an enhance accumulation of drugs inside the tumor
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Zheng, Hairong. "Ultrasound contrast agents and their applications for novel ultrasound imaging techniques". Diss., Connect to online resource, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3207695.
Testo completo
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Al-Mejrad, Ali Saleh Khalid. "Medical ultrasound : a study of real-time three dimensional ultrasound imaging". Thesis, University of Edinburgh, 1996. http://hdl.handle.net/1842/21190.
Testo completoAbstract (sommario):
Ultrasonic techniques are very widely applied in medicine. Real-time two dimensional imaging is a technology which is extremely well-suited to medical applications since it enables moving structures to be observed and rapid searching through tissue structures to be performed. Three-dimensional (3D) ultrasonic imaging techniques have been developed but to date there has been very limited success in the development of real-time versions. The aim of this thesis is to study the feasibility of real-time 3D ultrasonic imaging to see if ways can be found to overcome the fundamental problem of sparcity of echo line data when a volume is scanned in real-time. The fundamental problem arises because conventional ultrasonic scanners have an upper limit of rate of generation of scan lines of around 10 KHz. The number of scan lines in each scanned volume is therefore low e.g. 2000 for a volume scan rate of 5 volumes per second. The aim of this thesis is to investigate whether or not modern electronic and image processing techniques can overcome this fundamental problem. During the first phase of our study, a microcomputer based C-scan test-rig system including hardware and software has been constructed to investigate the effectiveness of real-time image processing in compensating for the fundamental sparcity of echo data. This was investigated initially since C-scans suffer from the same sparcity of echo data as 3D scans. After the promising results obtained from this system using a number of image processing techniques, a hand-held 3D ultrasound system including hardware and software based on one of the commercial scanners (Dynamic Imaging C2000) has been constructed to extend our study to 3D. A number of test objects in addition to volunteers were scanned to investigate the feasibility of real-time 3D ultrasound imaging. Finally, a specification for real-time ultrasound imaging is discussed.
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Saavedra, Bazán Ana Cecilia. "Characterization of healthy skin with high-frequency ultrasound using quantitative ultrasound". Master's thesis, Pontificia Universidad Católica del Perú, 2018. http://tesis.pucp.edu.pe/repositorio/handle/123456789/12471.
Testo completoAbstract (sommario):
The skin is the largest organ of the body that protects it from the external environment. High- frequency ultra sound (HF-US) has been used to visualize the skin in depth and to diagnose some pathologies in dermatological applications. Quantitative ultrasound (QUS) includes several techniques that provide values of particular physical properties. In this thesis work, three QUS parameters are explained and used to characterize healthy skin through HF-US: attenuation coefficient slope (ACS), backscatter coefficient (BSC) and shear wave speed (SWS). They were estimated with the regularized spectral-log difference (RSLD) method, the reference phan- tom method, and the crawling wave sonoelastography method, respectively. All the three parameters were assessed in phantoms, ex vivo and in vivo skin. In calibrated phantoms, RSLD showed a reduc- tion of up to 93% of the standard deviation concerning the estimation with SLD, and BSC showed an agreement with the Faran’s theoretical curve. In gelatin-based phantoms, surface acoustic waves (SAWs) were estimated in two interfaces: solid-water and solid-US gel, which all owed corroborating SAWs presence and finding an empirical compensation factor when the coupling interface is US gel. A correction factor of 0:97 for SAW-to-shear was found to avoid underestimation in phantoms. Porcine thigh was calculated in the range from 8 to 27 MHz, where the ACS was 4:08 _+_0:43 dB cm -1 MHz-1 and BSC was in the range from 10 1 to 10° sr-1 _cm-1. Crawling wave sonoelastography method was applied for the vibration frequencies between 200 Hz and 800 Hz, where SWS was in the range from 4:6 m/sto9:1 m/s. In vivo ACS and BSC were assessed in the healthy forearm and thigh, whereas SWS only in the thigh. The average ACS in the forearm dermis was 2.07dB cm-1 _MHz-1, which is in close agreement with the literature. A significant difference (p < 0.05) was found between the ACS in the forearm dermis and the thigh dermis (average ACS of 2.54dB cm-1 _MHz-1). The BSC of the forearm and thigh dermis were in the range from 10 -1 to 10° sr-1 _cm-1, and in the range from 10-1 to 10° sr-1 _cm-1, respectively. The SWS in the thigh dermis was 2:4 _+_0:38 m/s for a vibration frequency of 200Hz, with an increasing trend as frequency increases. Results suggest that these QUS parameters have the potential to be used as a tool for in vivo skin characterization and show potential for future application in skin lesions.Tesis
16
Lafond, Maxime. "Confocal Ultrasound for the Potentiation of Chemotherapy by Ultrasonic Cavitation without External Nucleation Agents". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1243/document.
Testo completoAbstract (sommario):
Le cancer est reconnu comme l'un des principaux enjeux de santé actuels. Même si de grands progrès ont été réalisés dans ce domaine, les effets systémiques des chimiothérapies et le caractère invasif des procédures actuelles de potentialisation (agents physiques) sont autant d'éléments limitants. Les ultrasons se démarquent néanmoins par leur faible morbidité. Appliqués de façon extracorporelle, ils peuvent pénétrer en profondeur dans les tissus et y induire effets thermiques et mécaniques, incluant entre autres la cavitation. La cavitation peut se définir comme la formation et l'oscillation de bulles dans le milieu de propagation. Il a été montré de potentiels bénéfices de ce mécanisme dans la potentialisation d'agents thérapeutiques. Bien que la génération de cavitation puisse être aidée par l'ajout d'agents de nucléation extérieurs, le travail présenté ici s'en affranchit afin de rendre la procédure plus versatile. Des simulations ont montré qu'un dispositif ultrasonore basé sur deux faisceaux confocaux permettait des conditions favorables à l'obtention de cavitation dans ces conditions. De plus, études in vivo ont montré l'innocuité du phénomène en regard de la stabilité de la doxorubicine, des effets histologiques sur tissus sains ainsi que sur l'éventuelle diffusion métastatique. L'efficacité du traitement combiné n'a en revanche pas pu être démontrée. Pour investiguer la combinaison de chimiothérapie avec de la cavitation stable, une stratégie de régulation est mise en place. Bien que la synergie ait pu être démontrée in vitro, l'étude préclinique ne permet pas de conclure sur l'effet in vivo. Dans l'hypothèse d'un défaut de localisation du nuage de cavitation, une méthode de localisation spatiale est mise en place et validéeCancer is recognized as one of the major health issues of this beginning century. Even if great achievements have been performed, chemotherapies induce systemic toxicity and combinable physical agents are invasive. Ultrasound has shown a great potential as an external physical agent. Applied extracorporeally, it can penetrate in depth in tissue and induce various biological effects, mechanical of thermal. Notably, cavitation, which is the formation and oscillatory motion of bubbles in a media, has effects providing the possibility to enhance the delivery of chemotherapeutic agents. This effect can be induced in biological tissues by using external nucleation agents such as ultrasound contrast agents. However, to avoid diffusion issues, this work focuses on cavitation without external nucleation agents. For this purpose, a particular setup based on two confocal transducers was designed. Simulations showed its advantages for cavitation applications. A developed preclinical device demonstrated the safety of using unseeded inertial cavitation for the potentiation of doxorubicin (DOX) regarding the drug stability, the effect on healthy tissues and the metastatic spreading. Unfortunately, no effect of combining inertial cavitation with DOX in could have been demonstrated in vivo. To investigate stable cavitation phenomenon, a control process was developed. It permitted to evidence in vitro the synergistic interaction between DOX and stable cavitation. Again, preclinical studies were not able to prove this synergy in vivo. To assess the correct tissue exposures to stable cavitation, a localization method was developed and validated
17
Cuxac, Pascal. "Propagation et atténuation des ondes ultrasoniques dans des roches fissurées et anisotropes". Vandoeuvre-les-Nancy, INPL, 1991. http://docnum.univ-lorraine.fr/public/INPL_T_1991_CUXAC_P.pdf.
Testo completoAbstract (sommario):
Les recherches présentées dans ce mémoire concernent l'application de la propagation d'ondes ultrasoniques à l'étude de roches fissurées et/ou anisotropes. Ce travail peut être décomposé en quatre grandes parties : la première étape est basée sur l'étude des célérités des ondes compressionnelles et cisaillantes. Celles-ci permettent la détermination des anisotropies des roches aboutissant à une classification selon le degré de symétrie. Cette symétrie impose les directions de propagation et de polarisation nécessaires à la détermination des modules élastiques dynamiques. Un montage dans une cellule triaxiale nous a permis d'étudier l'influence de la contrainte. Celle-ci se traduit par une augmentation des vitesses du fait de la fermeture de fissures. Cependant l'étude complète de l'évolution des paramètres élastiques avec la pression reste impossible dans le cas de roches anisotropes. La deuxième partie aborde la détermination de l'atténuation d'une onde compressionnelle à partir de la méthode du rapport de spectres. Ces mesures réalisées sur roches fortement anisotropes montrent la nécessité de travailler en milieu confiné afin d'avoir un signal de bonne qualité. Le calcul d'atténuation est ensuite appliqué à la caractérisation d'un milieu isotrope fissuré. Un calcul de densité de fissuration relative est tout d'abord proposé à partir des célérités des ondes. Ensuite, à partir de nos essais, nous discutons des diverses théories existantes. Il apparait que nos résultats font intervenir un grand nombre de mécanismes qui ne peuvent être pris en considération par les différents modèles. En milieu anisotrope, ces mesures sont rendues très difficiles par l'apparition de fissures dans le plan d'anisotropie rendant la roche beaucoup trop atténuante. Enfin, l'étude de la propagation d'ultrasons durant un essai de traction directe permet de constater un endommagement précoce du grès étudié. Le calcul des modules élastiques statiques à partir d'essais de compression constitue la troisième partie. L'influence de la pression de confinement et de l'orientation de l'anisotropie est mise en évidence. Dans la dernière partie, nous comparons les modules élastiques obtenus par les deux méthodes. On constate une bonne corrélation des paramètres sauf lorsque la présence de fissures influe sur la mesure ; les modules dynamiques apparaissent alors supérieures aux modules statiques
18
Thomas, Gilles. "Design, Optimization and Evaluation of an Extracorporeal Piezoelectric Lithotripter". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1021/document.
Testo completoAbstract (sommario):
Les lithiases urinaires peuvent affecter le rein, l'uretère ou la vessie, et affectent en moyenne, au moins une fois durant leur vie, 1 personne sur 11 aux Etats-Unis. La lithotritie extracorporelle est une technique largement répandue dans le monde qui consiste à focaliser des ondes de choc acoustiques de haute intensité sur les lithiases afin de les briser. Le travail présenté dans cette thèse porte sur l'optimisation de la lithotritie piézoélectrique, à la fois dans sa conception mais aussi dans son efficacité, tout en réduisant son coût de fabrication. Premièrement, une étude de l'état de l'art de la lithotritie a été réalisée, suivie par des expériences sur des lithotriteurs commerciaux et expérimentaux afin de déterminer les différents axes de recherche de la thèse. Ensuite, une optimisation des éléments piézoélectriques d'un lithotriteur a été réalisée afin d'obtenir un traitement plus performant. Finalement, des lithotriteurs composés de transducteurs piézoélectriques focalisés grâce à des lentilles optimisées ont été conçus et fabriqués. Leurs champs acoustiques, leurs effets sur la cavitation et leur efficacité à fragmenter des lithiases artificielles ont été évalués. Les lithotriteurs résultant ont montré des performances équivalentes à des lithotriteurs commerciaux existant, tout en permettant un traitement plus flexible que ces derniersKidney Stones can be found in the kidney, ureter, or in the bladder, and affect about 1 in 11 people at least once in a lifetime in the US. Extracorporeal shock wave lithotripsy is a widely used technique where high intensity acoustic pulses are focused toward kidney stones in order to break them. The work presented in this thesis focus on optimizing piezoelectric lithotripter, both in design and efficiency, in order to have more efficient treatment while also being less costly. First, a study of the current state of lithotripsy was made, followed by experiments on commercial and experimental lithotripters in order to define properly the different parameters to be worked on. From this, it was decided to optimize the current piezoelectric elements in the lithotripter to obtain a more efficient treatment. Then, a lithotripter using optimized lens focused piezoelectric transducers set in confocal setups was designed and manufactured. Its acoustic characterization, effect on cavitation and model stone fragmentation efficiency were evaluated. The resulting lithotripter showed performances equivalent to existing commercial lithotripter, while allowing more flexible treatment than traditional lithotripter
19
Suomi, Visa. "The feasibility of ultrasound elastography in monitoring high-intensity focused ultrasound therapy". Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:1b18e435-43b2-4487-9637-5f8ec79c4aef.
Testo completoAbstract (sommario):
High-intensity focused ultrasound (HIFU) therapy is a non-invasive therapy method for the treatment of solid tumours. One of the main barriers to wider clinical adoption of HIFU is the lack of reliable and cost-efficient therapy monitoring. One promising technique is acoustic radiation force (ARF) ultrasound elastography, which relies on the temperature dependence of tissue properties to affect displacement amplitudes. An extensive literature review of tissue acoustic, thermal and mechanical properties identified an absence of data on the temperature dependence of the viscoelastic properties. Experiments were carried out in ex vivo liver to determine these properties over the range of temperatures and frequencies relevant to ARF. ARF induced displacements were quantified experimentally in a tissue-mimicking phantom. The comparison of sine and square modulated ARF excitation showed that square modulation results in higher peak amplitudes and smaller second harmonic components in the frequency domain. A simulation model was developed, which accurately reproduced the observed displacements with different modulation frequencies and power levels. The effect of temperature on ARF displacements was measured experimentally during HIFU therapy in ex vivo liver. Simulations captured the same phenomena as observed in the experiments. ARF displacements during HIFU therapy were shown to initially depend on attenuation before ablation, but once the temperature exceeded the ablation threshold, viscoelastic properties dominated. A second barrier for HIFU is the need to reliably deliver acoustic energy to the target. Nonlinear acoustic simulations were conducted using patient derived computed tomography (CT) data to evaluate the HIFU therapy in the kidney. The simulations revealed that attenuation and refraction contributed roughly equally to intensity loss. Focal splitting associated with refraction was found to be the main effect reducing the heating efficacy, and a method to employ phase correction at the source was proposed to mitigate the effect.
20
Londeen, Marika. "Therapeutic Ultrasound: The Effectiveness of Ultrasound and the Importance of Parameter Settings". Thesis, North Dakota State University, 2013. https://hdl.handle.net/10365/27104.
Testo completoAbstract (sommario):
Therapeutic ultrasound can be an important modality for clinician's use to heat tissue. Previous research has concluded that therapeutic ultrasound treatments may be ineffective. There are several options for parameters depending on type of treatment and desired goal. The purpose of this study was to determine if specific parameters for a specific desired treatment goal were correct. The parameters included 1.0 and 3.0 megahertz frequencies of continuous ultrasound treatment on 20 subjects. Tissue temperature was measured with thermocouples in the calf. Data analysis consisted of running a one way repeated measures ANOVA to compare sample means as well as running t-test's for each change in temperature for each setting. Some subjects reached a temperature which could be considered therapeutic and only a few subjects reached the temperature goal. This is important for clinicians to note that every patient is different and that parameters will differ with each machine.
21
Griffin, Maura Bernadette. "Ultrasound and cardiovascular risk". Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404414.
Testo completo
22
Schwartz, Benjamin Matthew. "Biometric Navigation with Ultrasound". Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10431.
Testo completoAbstract (sommario):
We have designed and demonstrated a new class of medical navigation methods that use the fingerprint-like biometrically distinct ultrasound echo patterns produced by different locations in tissue. As an example of this new biometric navigation approach, we have constructed and tested a system that uses ultrasound data to achieve prospective motion compensation in MRI, especially for respiratory motion during interventional MRI procedures in moving organs such as the liver. The ultrasound measurements are collated with geometrical information from MRI during a training stage to form a mapping table that relates ultrasound measurements to positions. During prospective correction, the system makes frequent ultrasound measurements and uses the map to determine the corresponding position. Results in motorized linear motion phantoms and freely breathing animals indicate that the system performs well. Apparent motion is reduced by up to 97.8%, and motion artifacts are reduced or eliminated in 2D Spoiled Gradient-Echo images. The motion compensation is sufficient to permit MRI thermometry of focused ultrasound heating during respiratory-like motion, with results similar to those obtained in the absence of motion. This new technique may have applications for MRI thermometry and other dynamic imaging in the abdomen during free breathing. We have also extended this technique to situations in which external position information during training is unavailable or incomplete, by extending the concept of Simultaneous Localization and Mapping to include determining the topology of a dense motion path through a gaussian random field. In the course of these investigations, we have also developed modified forms of referenceless MRI thermometry and Kalman filtering, specially adapted to optimize accuracy under our experimental conditions.
23
Gerold, Bjoern. "Cavitation in focused ultrasound". Thesis, University of Dundee, 2013. https://discovery.dundee.ac.uk/en/studentTheses/f41bf6b9-ae59-4a41-ba29-d5873821418b.
Testo completoAbstract (sommario):
A novel experimental conguration is developed combining a highintensity focused ultrasound source and a pulsed-laser, for the study of cavitation in a eld typical of those used for therapeutic ultrasound. The sonoptic chamber is specically designed to avoid the formation of acoustic standing waves, known to have a critical in uence on cavitation behaviour. A new technique of laser-nucleated acous- tic cavitation is presented, whereby a laser-pulse of energy below the breakdown threshold for the host medium, acts to nucleate acoustic cavitation in a pre-established eld. This facilitates the incorporation of high-speed cameras for interrogation at unprecedented temporal and spatial resolution, combined with acoustic detection directly correlated to the observed cavitation activity. A number of cavitation phenomena are investigated, including bubble-ensemble oscillations at a very early stage of development, in response to the acoustic driving. The frequency of oscillation, which bifurcates with increasing intensity, is also detected in the acoustic emissions. The application of a single-bubble model predicts a source for the acoustic emissions of quiescent radius equivalent to the bubble-ensemble observed, for each intensity investigated. The physical translation of the ensemble, due to the radiation force imposed by the primary eld, is also analysed. For laser-pulses of energy above the breakdown threshold, applying focused ultrasound to the cavity promotes and actuates jet-formation. The characteristics of the so formed jets depend on the intensity and location of the cavity relative to the ultrasound focus.
24
Anaya, Demetrio Donald. "Ultrasound-Compatible Cardiac Simulator". Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:17417571.
Testo completoAbstract (sommario):
Devices are being developed so that robots can perform cardiac surgery. These robots will steer catheters through a beating heart using image guidance from ultrasound imaging. An appropriate ultrasound-compatible cardiac simulator has been developed in order to test these systems. This simulator mimics the geometry and the complex motion of a beating human heart. The left ventricle phantom is comprised of a soft echogenic material that mimics heart tissue in an ultrasound image. The cardiac simulator will be a useful tool for research and industry applications where testing on an ultrasound compatible phantom is desirable.Mechanical Engineering
25
Nam, Haewon. "Ultrasound-modulated optical tomography". Texas A&M University, 2002. http://hdl.handle.net/1969/448.
Testo completo
26
Bui, Minh Thanh. "Statistical modeling, level-set and ensemble learning for automatic segmentation of 3D high-frequency ultrasound data : towards expedited quantitative ultrasound in lymph nodes from cancer patients". Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066146/document.
Testo completoAbstract (sommario):
Afin d'accélérer et automatiser l'analyse par ultrasons quantitatifs de ganglions lymphatiques de patients atteints d'un cancer, plusieurs segmentations automatiques des trois milieux rencontrés (le parenchyme du ganglion, la graisse périnodale et le sérum physiologique) sont étudiées. Une analyse statistique du signal d'enveloppe a permis d'identifier la distribution gamma comme le meilleur compromis en termes de qualité de la modélisation, simplicité du modèle et rapidité de l'estimation des paramètres. Deux nouvelles méthodes de segmentation basées sur l'approche par ensemble de niveaux et la distribution gamma sont décrites. Des statistiques locales du signal d'enveloppe permettent de tenir compte des inhomogénéités du signal dues à l'atténuation et la focalisation des ultrasons. La méthode appelée LRGDF modélise les statistiques du speckle dans des régions dont la taille est contrôlable par une fonction lisse à support compact. La seconde, appelée STS-LS, considère des coupes transverses, perpendiculaires au faisceau, pour gagner en efficacité. Une troisième méthode basée sur la classification par forêt aléatoire a été conçue pour initialiser et accélérer les deux précédentes. Ces méthodes automatiques sont comparées à une segmentation manuelle effectuée par un expert. Elles fournissent des résultats satisfaisants aussi bien sur des données simulées que sur des données acquises sur des ganglions lymphatiques de patients atteints d'un cancer colorectal ou du sein. Les paramètres ultrasonores quantitatifs estimés après segmentation automatique ou après segmentation manuelle par un expert sont comparablesThis work investigates approaches to obtain automatic segmentation of three media (i.e., lymph node parenchyma, perinodal fat and normal saline) in lymph node (LN) envelope data to expedite quantitative ultrasound (QUS) in dissected LNs from cancer patients. A statistical modeling study identified a two-parameter gamma distribution as the best model for data from the three media based on its high fitting accuracy, its analytically less-complex probability density function (PDF), and closed-form expressions for its parameter estimation. Two novel level-set segmentation methods that made use of localized statistics of envelope data to handle data inhomogeneities caused by attenuation and focusing effects were developed. The first, local region-based gamma distribution fitting (LRGDF), employed the gamma PDFs to model speckle statistics of envelope data in local regions at a controllable scale using a smooth function with a compact support. The second, statistical transverse-slice-based level-set (STS-LS), used gamma PDFs to locally model speckle statistics in consecutive transverse slices. A novel method was then designed and evaluated to automatically initialize the LRGDF and STS-LS methods using random forest classification with new proposed features. Methods developed in this research provided accurate, automatic and efficient segmentation results on simulated envelope data and data acquired for LNs from colorectal- and breast-cancer patients as compared with manual expert segmentation. Results also demonstrated that accurate QUS estimates are maintained when automatic segmentation is applied to evaluate excised LN data
27
Sandoval, Niño Zulma. "Planning and guidance of ultrasound guided High Intensity Focused Ultrasound cardiac arrhythmia therapy". Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S044/document.
Testo completoAbstract (sommario):
L'objectif des travaux présentés dans ce document est de développer de nouvelles méthodes de traitement d'images pour améliorer la planification et le guidage d'une thérapie par voie transœsophagienne de la fibrillation auriculaire à l'aide d'Ultrason Focalisé Haute Intensité. Le document est divisé en deux parties : la planification du traitement et le guidage de la thérapie. Pour la planification de la thérapie, l'idée est d'exploiter l'information acquise au stade préopératoire par un scanner X ou IRM afin de retrouver l'anatomie spécifique du patient et à y définir le futur geste thérapeutique. Plus particulièrement, nos différentes contributions ont porté sur une approche multi-atlas de segmentation de l'oreillette gauche et des veines pulmonaires ; le tracé des lignes de lésions sur le volume initial ou segmenté ; et la reconstruction d'un volume adapté à la future navigation transœsophagienne. Pour le guidage de la thérapie, nous proposons une nouvelle approche de recalage qui permet d'aligner les images échographiques peropératoires 2D et l'information 3D CT préopératoire. Dans cette approche, dans un premier temps nous avons sélectionné la mesure de similarité la plus adaptée à notre problématique à l'aide d'une évaluation systématique puis nous avons tiré profit des contraintes imposées à la sonde transœsophagienne par l'anatomie du patient pour simplifier la procédure de recalage. Toutes ces méthodes ont été évaluées sur des fantômes numériques ou physiques et sur des données cliniquesThe work presented in this document aims at developing new image-processing methods to improve the planning and guidance of transesophageal HIFU atrial fibrillation therapy. This document is divided into two parts, namely therapy planning and therapy guidance. We first propose novel therapy planning methods that exploit high-resolution pre-operative CT or MRI information to extract patient-specific anatomical details and to define future therapeutic procedures. Our specific methodological contributions concern the following: an automatically-refined atlas-based segmentation approach to extract the left atrium and pulmonary veins; the delineation of the lesion lines on the original or segmented volume; and the reconstruction of a volume adapted to future intraoperative transesophageal navigation. Secondly, our proposal of a novel registration approach for use in therapy guidance aligns intraoperative 2D ultrasound with preoperative 3D CT information. This approach first carries out a systematic statistical evaluation to select the best similarity measure for our application and then takes advantage of the geometrical constraints of the transesophageal HIFU probe to simplify the registration process. Our proposed methods have been evaluated on digital and/or physical phantoms and on real clinical data
28
Lafond, Maxime. "Confocal Ultrasound for the Potentiation of Chemotherapy by Ultrasonic Cavitation without External Nucleation Agents". Electronic Thesis or Diss., Lyon, 2016. http://www.theses.fr/2016LYSE1243.
Testo completoAbstract (sommario):
Le cancer est reconnu comme l'un des principaux enjeux de santé actuels. Même si de grands progrès ont été réalisés dans ce domaine, les effets systémiques des chimiothérapies et le caractère invasif des procédures actuelles de potentialisation (agents physiques) sont autant d'éléments limitants. Les ultrasons se démarquent néanmoins par leur faible morbidité. Appliqués de façon extracorporelle, ils peuvent pénétrer en profondeur dans les tissus et y induire effets thermiques et mécaniques, incluant entre autres la cavitation. La cavitation peut se définir comme la formation et l'oscillation de bulles dans le milieu de propagation. Il a été montré de potentiels bénéfices de ce mécanisme dans la potentialisation d'agents thérapeutiques. Bien que la génération de cavitation puisse être aidée par l'ajout d'agents de nucléation extérieurs, le travail présenté ici s'en affranchit afin de rendre la procédure plus versatile. Des simulations ont montré qu'un dispositif ultrasonore basé sur deux faisceaux confocaux permettait des conditions favorables à l'obtention de cavitation dans ces conditions. De plus, études in vivo ont montré l'innocuité du phénomène en regard de la stabilité de la doxorubicine, des effets histologiques sur tissus sains ainsi que sur l'éventuelle diffusion métastatique. L'efficacité du traitement combiné n'a en revanche pas pu être démontrée. Pour investiguer la combinaison de chimiothérapie avec de la cavitation stable, une stratégie de régulation est mise en place. Bien que la synergie ait pu être démontrée in vitro, l'étude préclinique ne permet pas de conclure sur l'effet in vivo. Dans l'hypothèse d'un défaut de localisation du nuage de cavitation, une méthode de localisation spatiale est mise en place et validéeCancer is recognized as one of the major health issues of this beginning century. Even if great achievements have been performed, chemotherapies induce systemic toxicity and combinable physical agents are invasive. Ultrasound has shown a great potential as an external physical agent. Applied extracorporeally, it can penetrate in depth in tissue and induce various biological effects, mechanical of thermal. Notably, cavitation, which is the formation and oscillatory motion of bubbles in a media, has effects providing the possibility to enhance the delivery of chemotherapeutic agents. This effect can be induced in biological tissues by using external nucleation agents such as ultrasound contrast agents. However, to avoid diffusion issues, this work focuses on cavitation without external nucleation agents. For this purpose, a particular setup based on two confocal transducers was designed. Simulations showed its advantages for cavitation applications. A developed preclinical device demonstrated the safety of using unseeded inertial cavitation for the potentiation of doxorubicin (DOX) regarding the drug stability, the effect on healthy tissues and the metastatic spreading. Unfortunately, no effect of combining inertial cavitation with DOX in could have been demonstrated in vivo. To investigate stable cavitation phenomenon, a control process was developed. It permitted to evidence in vitro the synergistic interaction between DOX and stable cavitation. Again, preclinical studies were not able to prove this synergy in vivo. To assess the correct tissue exposures to stable cavitation, a localization method was developed and validated
29
Schöne, Martin. "Possibilities of Articular Cartilage Quantification Based on High-Frequency Ultrasound Scans and Ultrasound Palpation". Doctoral thesis, Humboldt-Universität zu Berlin, 2020. http://dx.doi.org/10.18452/21781.
Testo completoAbstract (sommario):
In der Diagnostik und Reparatur von hyalinem Gelenkknorpel sind neue Methoden zur Quantifizierung von Struktur und mechanischer Belastbarkeit gefragt, um die Behandlung von Knorpelschäden an Millionen von Patienten weltweit zu verbessern.
Mittels hochfrequentem, fokussierten Ultraschall werden Oberflächenparameter für Reflektivität und Rauheit an Gelenkknorpel bestimmt. Es wird gezeigt wie die Oberflächenneigung kontrolliert werden kann. Die Ergebnisse vermitteln ein besseres Verständnis über die Zusammensetzung der Ultraschallsignale aus reflektierten und gestreuten Komponenten.
3D Ultraschallscans von Knorpelregeneraten erlauben die Defektstellen volumetrisch zu Quantifizieren. Die Proben wurden zusätzlich nach etablierten Bewertungssystemen benotet, welche auf makroskopischer Beurteilungen, MRT-Scans und Histologie basieren. Die ultraschallbasierten Volumendaten zeigten dabei gute Korrelationen mit den Punktwertungen.
Die im Labor verwendeten Messaufbauten zur biomechanischen Charakterisierung von Gelenkknorpel können am Patienten nicht angewandt werden. Daher können Ärzte die Festigkeit von Knorpel bisher nur mittels manueller Palpation abschätzen. Diese Arbeit entwickelt eine Methode der Ultraschall-Palpation (USP), die es erlaubt, die während der manuellen Palpation erzeugte Kraft und Deformation, basierend auf Ultraschallechos, aufzunehmen. Es wurde einen Prototyp entwickelt womit gezeigt werden konnte, dass USP eine ausreichende Genauigkeit und Reproduzierbarkeit aufweist. Wiederholte Messungen können zusätzlich zeitabhängige biomechanische Parameter von Knorpel ableiten.
Zusammenfassend zeigt diese Arbeit verbesserte und neue Möglichkeiten zur strukturellen und biomechanischen Charakterisierung von hyalinem Gelenkknorpel bzw. den Ergebnissen von Knorpelreparatur basierend auf Ultraschalldaten. Diese Methoden haben das Potenzial die Diagnostik von Gelenkknorpel und die Quantifizierung von Knorpelreparatur zu verbessern.In the diagnostics and repair of hyaline articular cartilage, new methods to quantify structure and mechanical capacity are required to improve the treatment of cartilage defects for millions of patients worldwide. This thesis uses high frequency focused ultrasound to derive surface parameters for reflectivity and roughness from articular cartilage. It is shown how to control the inclination dependency to gain more reliable results. Furthermore, the results provided a better understanding of the composition of ultrasonic signals from reflected and scattered components. 3D ultrasound scans of cartilage repair tissue were performed to quantify defect sites after cartilage repair volumetrically. The samples were also graded according to established scoring systems based on macroscopic evaluation, MRI scans and histology. The ultrasound-based volumetric parameters showed good correlation with these scores. Complex biomechanical measurement setups used in laboratories cannot be applied to the patient. Therefore, currently physicians have to estimate the stiffness of cartilage by means of manual palpation. In the last part of this thesis, a method denoted as ultrasound palpation is developed, which allows for measuring the applied force and strain during manual palpation in real time, solely based on the evaluation of the time of flight of ultrasound pulses. A prototype was developed and its measurement accuracy and reproducibility were characterized. It could be shown that ultrasound palpation has sufficient accuracy and reproducibility. Additionally, by repeated measurements it was possible to derive time-dependent biomechanical parameters of cartilage. In summary, this work shows improved and new possibilities for structural and biomechanical characterization of hyaline articular cartilage and the outcomes of cartilage repair based on ultrasound data. The methods have the potential to improve the diagnostics of articular cartilage and quantification of its repair.
30
Helbert, Alexandre. "L'imagerie moléculaire de contraste ultrasonore en oncologie : Utilisation des microbulles BR55 ciblant le VEGFR2 dans la détection de l’angiogenèse tumorale, le guidage thérapeutique et l'évaluation de l'efficacité de traitements antiangiogéniques et cytotoxiques". Electronic Thesis or Diss., Lyon, 2022. http://www.theses.fr/2022LYSE1076.
Testo completoAbstract (sommario):
L’imagerie de contraste ultrasonore a connu un essor considérable ces dernières décennies. Plusieurs agents de contraste ultrasonores, des microbulles de gaz encapsulées, ont été mis sur le marché pour des applications telles que l’imagerie cardio-vasculaire et la radiologie. À la suite de la démonstration de leur efficacité, de nouvelles recherches ont été menées. Une nouvelle génération de microbulles a été développée : les microbulles ciblées. Leur particularité est de contenir, au sein de la membrane, un ligand pouvant se fixer sur des marqueurs vasculaires spécifiques d’une pathologie ; comme par exemple, de l’angiogenèse tumorale. À ce jour, un produit dit « de contraste moléculaire ultrasonore » a été testé chez l’homme pour la détection de tumeurs de la prostate, du sein et de l’ovaire : le BR55. L’objectif de ce travail a consisté à explorer les possibilités du BR55, au-delà du diagnostic. Le travail expérimental a été réalisé sur des modèles murins. Dans la première partie de ce travail, il a été nécessaire d’acquérir la maîtrise de l’utilisation de cette technologie particulière afin de garantir la robustesse des expériences réalisées et des résultats obtenus. Le BR55 a pour particularité de pouvoir se fixer sur un récepteur, le VEGFR2, surexprimé dans le processus d’angiogenèse tumorale. Les microbulles BR55 fixées sur ce récepteur permettent de visualiser la lésion par imagerie de contraste. La seconde partie de ce travail a été de suivre l’évolution de l’expression du VEGFR2 lors d’un traitement antiangiogénique agissant sur ce dernier. Nous avons pu démontrer la précocité avec laquelle le suivi de l’expression du VEGFR2 par le BR55 peut objectiver la réponse tumorale au traitement. Enfin, nous avons utilisé les microbulles BR55 pour réaliser le guidage d’une thérapie par ultrasons focalisés permettant de cibler la localisation du relargage de la doxorubicine, contenue dans des liposomes sonosensibles. Non seulement il a été possible de réaliser ce guidage par imagerie de contraste moléculaire ultrasonore, mais là encore l’utilisation du BR55 a permis de suivre la réponse au traitement. Les résultats présentés dans ce travail de thèse ouvrent la voie à de nouveaux usages potentiels du BR55 pour le suivi thérapeutique et le guidage de traitements par échographie de contraste ultrasonoreUltrasound contrast imaging has grown considerably in recent decades. Several intravascular ultrasound contrast agents, encapsulated gas microbubbles, have been marketed for applications such as cardiovascular imaging and radiology. Following the demonstration of their effectiveness, further research was conducted. A new generation of microbubbles has been developed : targeted microbubbles. Their particularity is to contain, on their shell, a ligand that can bind to specific vascular markers of a pathology such as markers of tumor angiogenesis. To date, only one molecular ultrasound contrast agent, the so-called BR55, has been tested in humans for the detection of tumors of the prostate, breast and ovary. The objective of this work was to explore the possibilities of BR55, beyond diagnosis. The experimental work was performed on rodent models. In the first part of this work, it was necessary to master the use of ultrasound molecular contrast imaging in order to guarantee the robustness of the experiments performed and of the results obtained. BR55 has the particularity of being able to bind to a receptor, VEGFR2, overexpressed in the process of tumor angiogenesis. The BR55 microbubbles attached to this receptor allow visualization of the lesion by contrast imaging. The second part of this work was to follow the evolution of VEGFR2 expression during an antiangiogenic treatment targeting this receptor. We were able to demonstrate the precocity with which the monitoring of VEGFR2 expression by BR55 can objectify the tumor response to treatment. Finally, we used BR55 microbubbles to guide a focused ultrasound therapy to target the localization of doxorubicin release from sonosensitive liposomes. Not only was it possible to perform the treatment guidance by ultrasound molecular contrast imaging, but again the use of BR55 allowed to follow the response to the treatment. The results presented in this thesis pave the way for potential new uses of BR55 for therapeutic monitoring and guidance of treatments by ultrasound molecular contrast imaging
31
Kabbani, Dania. "Ultrasound-assisted liquefaction of honey". Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/144664.
Testo completoAbstract (sommario):
Crystallization of honey is a common process of the honey industry. Liquid honey is preferred by most of the consumers and by food companies for ease of handling. Honey is commonly heated during pasteurization in order to liquefy it and inhibit any microbial growth. However, heating can degrade the main quality parameters of honey.
A better method compared to expensive and time-consuming heating is desirable to pasteurize, accelerate the liquefaction and retard the crystallization process in honey.
The present thesis documents the work done at investigating the effect of the ultrasounds (US) in honey liquefaction, quality alteration and honey decontamination.
Firstly, in Chapter 1, the effect of different combinations of US treatment (power, temperature and duration) on honey liquefaction were evaluated by studying the rheological properties of honey; viscosity behaviour, crystal content, tendency to re-crystallization and thermal properties. Secondly, in Chapter 2, the effects of US on the hydroxymethylfurfural concentration and diastase activities in honey were determined by chemical analysis and compared with that for standard heat-treated honey samples. Thirdly, in Chapter 3, US treatment was investigated for honey decontamination. In addition, the in vitro antimicrobial and antifungal activities of ultrasonicated honey against several types of microorganisms were evaluated.
The results obtained in this research point to a successful application of the ultrasound technology for the liquefaction of honey, as it speeds up its liquefaction, do not degrade the quality and the intrinsic biological activity of honey was neither affected.
32
Driveklepp, Anders. "Ultrasound Examination of Steel Pipes". Thesis, Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9575.
Testo completoAbstract (sommario):
Non-intrusive testing of pipelines has become a growing industry, and is expected to keep growing as the demands on quality control and safety keep increasing. In order to meet the oil industrys demands for pipe monitoring of sub sea pipelines, the SmartPipe project was initiated by SINTEF in Trondheim, Norway. One of the primary objectives of the SmartPipe project is develop a system for in-service monitoring of the pipelines that are placed on the seabed by the offshore oil industry. This thesis presents a very early step in the research required for the development of such a system. The purpose of the presented work was to carry out introductory experimental work in order to find out whether it is possible to develop relatively simple techniques for in-service testing of sub sea steel pipes. A so-called pitch-catch setup and various wedges was used in order to test the area between a pair of 5 MHz ultrasound transducers. Measuring over a distance of 1.00 m, rather than just single points on the pipe, could provide more general information about the condition of the pipe. Tests with over 4 m distance between transducers were also carried out. Measurement stability and mechanical coupling are of crucial importance in ultrasonic test systems, and useful knowledge on the subjects has been gained and are documented in this thesis. Results from measurements indicate that comprehensible results can be attained even with very simple measurement setups. Especially when using special wedges for introduction of Rayleigh waves, the received signals had high amplitudes and the signal envelope had a simple shape. The effect that the damage to the pipe had on the Rayleigh waves, was found to be equally simple and predictable. Shear waves and longitudinal waves that are less sensitive to the surrounding medium, were also shown to be applicable in flaw detection. Results and discussion include both time domain, frequency domain and energy considerations.
33
Walker, Andrew. "Testing of Doppler Ultrasound Systems". Doctoral thesis, Linköpings universitet, Fysiologisk mätteknik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-51213.
Testo completoAbstract (sommario):
Blood and tissue velocities are measured and analyzed in cardiac, vascular, and other applications of diagnostic ultrasound. Errors in system performance might give invalid measurements. We developed two moving string test targets and a rotating cylinder phantom (Doppler phantoms) to characterize Doppler ultrasound systems. These phantoms were initially used to measure such variables as sample volume dimensions, location of the sample volume, and the performance of the spectral analysis. Later, specific tests were designed and performed to detect errors in signal processing, causing time delays and inaccurate velocity estimation in all Doppler modes. In cardiac motion pattern even time delays as short as 30 ms may have clinical relevance. These delays can be obtained with echocardiography by using flow and tissue Doppler and M-mode techniques together with external signals (e.g., electrocardiography (ECG) and phonocardiography). If one or more of these signals are asynchronous in relation to the other signals, an incorrect definition of cardiac time intervals may occur. To determine if such time delays in signal processing are a serious problem, we tested four commercial ultrasound systems. We used the Doppler string phantom and the rotating cylinder phantom to obtain test signals. We found time delays of up to 90 ms in one system, whereas delays were mostly short in the other systems. Further, the time delays varied relative to system settings. In two-dimensional (2D) Doppler the delays were closely related to frame rate. To determine the accuracy in velocity calibration, we tested the same four ultrasound systems using the Doppler phantoms to obtain test signals for flow (PW) and tissue (T-PW) pulse Doppler and for continuous wave (CW) Doppler. The ultrasound systems were tested with settings and transducers commonly used in cardiac applications. In two systems, the observed errors were mostly close to zero, whereas one system systematically overestimated velocity by an average of 4.6%. The detected errors are mostly negliable in clinical practice but might be significant in certain cases and research applications.
34
Hergum, Torbjørn. "3D Ultrasound for Quantitative Echocardiography". Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for sirkulasjon og bildediagnostikk, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-5937.
Testo completoAbstract (sommario):
Medical ultrasound imaging is widely used to diagnose cardiacdiseases. The recent availability of real time 3D ultrasound posesseveral interesting challenges and opportunities, and the work of thisthesis is devoted to both challenges and opportunities. One of the key benefits of ultrasound imaging is that its images arereal time. This has been challenged with the recent introduction of 3Dimages, where the number of ultrasound beams is squared compared totraditional 2D images. One common way to alleviate this is byreceiving several closely spaced ultrasound beams from each pulsetransmission, which increases acquisition speed but affects the imagequality. Specifically, B-mode images are irregularly sampled and losespatial shift invariance while a bias in the Doppler velocityestimates causes a discontinuity in the velocity estimates in colorflow images. We have found that these artifacts can be reducedsignificantly by interpolation of the beamformed data from overlappingbeams, with the limitation of requiring at least twice the number ofbeamformers. We have also found that valvular regurgitation is one of thecardiac diseases that can benefit greatly from quantification ofseverity using 3D ultrasound. We have devised a modality that useshigh pulse repetition frequency 3D Doppler to isolate thebackscattered signal power from the vena contracta of a regurgitantjet. This measure is calibrated with a narrow reference beam insidethe jet to estimate the cross-sectional area of the vena contracta. Wehave validated this method with computer simulations, with an in vitrostudy and finally in vivo with 27 patients who had mitralregurgitation. We found that the cross-sectional area and regurgitantvolume of the vena contracta could be quantified without bias as long as the orifice was sufficiently large for a calibration beam tofit inside it. The severity of smaller regurgitations will beoverestimated, but this does not pose a clinical problem, as thesepatients can easily be identified by standard 2D Doppler examination and donot typically need further quantification. Finally, we have developed a new, fast 3D ultrasound simulation methodthat can incorporate anisotropic scattering from cardiac muscle cells. This approach is three orders of magnitudefaster than the most commonly used simulation methods, making it wellsuited for the simulation of dynamic 3D images for development and testingof quantitative diagnostic methods such as 3D speckle tracking andvolumetric measurements.
35
Carlson, Johan. "Multiphase flow measurements using ultrasound". Licentiate thesis, Luleå tekniska universitet, Signaler och system, 1999. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17175.
Testo completoAbstract (sommario):
In process industries such as for example the oil and gas industry, the paper pulp industry, and the mining industry, multiphase flows are common. It is often of interest to measure the mass fractions of the different phases. In for example the mining industry, iron ore powder is transported using water, and there is a need of measurement techniques to monitor the particle mass fraction. Most existing techniques are either invasive, inaccurate, or too slow to be used in an on-line manner. The long-term goal of this research project is to develop a method for measuring mass fractions and mass fraction velocities, using ultrasound. The first two papers in this thesis consider how scattering of sound can be measured, and how this can be used to measure mass fractions. The ideas are verified with experiments. The third paper is on optimal experimental design. The problem is selecting suitable experiments from a large candidate set. We present a new algorithm for generating optimal designs. The methods in the first two papers can be extended to incorporate more of the underlying physics, as well as using more sophisticated multi-dimensional signal processing techniques.Godkänd; 1999; 20070320 (ysko)
36
Abeysekera, Jeffrey Michael. "Three dimensional ultrasound elasticity imaging". Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/57462.
Testo completoAbstract (sommario):
Changes in tissue elasticity are correlated with certain pathological changes, such as localized stiffening of malignant tumours or diffuse stiffening of liver fibrosis or placenta dysfunction. Elastography is a field of medical imaging that characterizes the mechanical properties of tissue, such as elasticity and viscosity. The elastography process involves deforming the tissue, measuring the tissue motion using an imaging technique such as ultrasound or magnetic resonance imaging (MRI), and solving the equations of motion. Ultrasound is well suited for elastography, however, it presents challenges such as anisotropic measurement accuracy and providing two dimensional (2D) measurements rather than three dimensional (3D). This thesis focuses on overcoming some of these limitations by improving upon methods of imaging absolute elasticity using 3D ultrasound. In this thesis, techniques are developed for 3D ultrasound acquired from transducers fitted with a motor to sweep the image plane, however many of the techniques can be applied to other forms of 3D acquisition such as matrix arrays. First, a flexible framework for 3D ultrasound elastography system is developed. The system allows for comparison and in depth analysis of errors in current state of the art 3D ultrasound shear wave absolute vibro-elastography (SWAVE). The SWAVE system is then used to measure the viscoelastic properties of placentas, which could be clinically valuable in diagnosing preeclampsia and fetal growth restriction. A novel 3D ultrasound calibration technique is developed which estimates the transducer motor parameters for accurate determination of location and orientation of every data sample, as well as for enabling position tracking of a 3D ultrasound transducer so multiple volumes can be combined. Another calibration technique using assumed motor parameters is developed, and an improvement to an existing N-wire method is presented. The SWAVE research system is extended to measure shear wave motion vectors with a new acquisition scheme to create synchronous volumes of ultrasound data. Regularization based on tissue incompressibility is used to reduce noise in the motion measurements. Lastly, multiple ultrasound volumes from different angles are combined for measurement of the full motion vector, and demonstrating accurate reconstructions of elasticity are feasible using the techniques developed in this thesis.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
37
Pong, Mona Wrenn Steven Parker. "Ultrasound and model membrane interaction /". Philadelphia, Pa. : Drexel University, 2007. http://hdl.handle.net/1860/2520.
Testo completo
38
Abeysekera, Jeffrey Michael. "Dual-transducer ultrasound for elastography". Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/27812.
Testo completoAbstract (sommario):
Medical imaging techniques provide valuable information about the internal anatomy of the body. Commonly used techniques can render many properties of the anatomy and its function, but they are limited in their ability to measure tissue mechanical properties such as elasticity. Over the past two decades there has been growing interest in developing methods of noninvasively characterizing mechanical properties of tissues; a field commonly referred to as elastography. Tissues are known to exhibit changes in mechanical properties in response to pathology. As a result, elastography has the particular potential to help physicians diagnose and locate cancerous tumors and other malignancies.
The principle of operation of elastography systems is to apply an excitation to the tissue, such as a compression, and to measure the resulting tissue
motion as it deforms. The tissue elasticity can then be inferred from the motion estimates by solving the inverse problem. Tissue motion is typically measured with ultrasound because it is fast, safe, and relatively inexpensive.
The point spread function of an ultrasound beam is anisotropic, resulting in poorer quality motion estimates in two of the three spatial directions. This thesis investigates a new method of estimating tissue motion by employing two ultrasound transducers with different view angles. The goal of using these two transducers is to create a plane of high quality 2D motion estimates. Simulations and experimental results on tissue mimicking phantoms
show that the method outperforms other commonly used 2D motion estimation methods. For example, in a tissue deformation simulation, the dual transducer method produced lower root mean square measurement error by a factor of 10 compared to a single transducer technique, and a factor of 3
compared to a single transducer with angular compounding.
A simple wire-based method of aligning the transducers into a coincident scan plane is initially developed. Later, a novel wedge-based phantom is designed for aligning the two transducers. Calibration results demonstrate improved alignment with the wedge phantom. Manual alignment is found to be repeatable with mean alignment errors under 1 degree in rotation and 1 mm in translation for all degrees of freedom after six independent trials.
39
Ashab, Hussam Al-Deen. "Ultrasound guidance for epidural anesthesia". Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44306.
Testo completoAbstract (sommario):
We propose an augmented reality system to automatically identify lumbar vertebral levels and the lamina region in ultrasound-guided epidural anesthesia. Spinal needle insertion procedures require careful placement of a needle, both to ensure effective therapy delivery and to avoid damaging sensitive tissue such as the spinal cord. An important step in such procedures is the accurate identification of the vertebral levels, which is currently performed using manual palpation with a reported success rate of only 30%. In this thesis, we propose a system using a trinocular camera which tracks an ultrasound transducer during the acquisition of a sequence of B-mode images. The system generates a panorama ultrasound image of the lumbar spine, automatically identifies the lumbar levels in the panorama image, and overlays the identified levels on a live camera view of the patient’s back. Several experiments were performed to test the accuracy of vertebral height in panorama images, the accuracy of vertebral levels identification in panorama images, the accuracy of vertebral levels identification on the skin, and the impact on accuracy with spine arching. The results from 17 subjects demonstrate the feasibility of the approach and capability of achieving an error within a clinically acceptable range for epidural anesthesia. The overlaid marks on the screen are used to assist locating needle puncture site. Then, an automated slice selection algorithm is used to guide the operator positioning a 3D transducer such that the best view of the target anatomy is visible in a predefined re-slice of the 3D ultrasound volume. This re-slice is used to observe, in real time, the trajectory of a needle attached to the 3D transducer, towards the target. The method is based on Haar-like features and AdaBoost learning algorithm. We have evaluated the method on a set of 32 volumes acquired from volunteer subjects by placing the 3D transducer on L1-L2, L2-L3, L3-L4 and L4- L5 interspinous gaps on each side of the lumbar spine. Results show that the needle insertion plane can be identified with a root mean square error of 5.4 mm, accuracy of 99.6%, and precision of 78.7%.
40
Beadle, Brad Michael. "Fiber optic sensor for ultrasound". Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17869.
Testo completo
41
Beadle, Brad Michael. "Fiber optic sensor for ultrasound". Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/19173.
Testo completo
42
Mercier, Laurence. "Ultrasound-guided brain tumor resection". Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107629.
Testo completoAbstract (sommario):
Malignant gliomas are the most common type of primary brain tumors in adults. Contrarily to brain metastases that have clear borders, malignant gliomas are poorly circumscribed lesions because they diffusely infiltrate the brain parenchyma. When possible, standard treatment of gliomas includes surgical resection, though surgeons unintentionally leave behind some of the tumor more than 50% of the time. Two factors are mainly responsible for this situation. First, most current neuronavigation systems are based on preoperative images; these systems become less accurate as the surgery progresses and the brain goes through important changes and deformations. Second, glioma boundaries are often visually and haptically difficult to determine. This is an unfortunate situation since maximum safe resection of these tumors correlates with longer survival times in patients presenting either a low-grade or high-grade glioma. By providing real-time images, intraoperative imaging techniques aid neurosurgeons achieve more complete resections while also helping to prevent damage to normal brain. In this thesis, I have investigated the use of intraoperative ultrasound to guide glioma surgery. To achieve this, I have used the prototype neuronavigation system developed by our research group: the IBIS NeuroNav system.The aim of the first paper was to evaluate the precision and accuracy of IBIS NeuroNav. Four aspects of the system were characterized: 1) the ultrasound probe calibration, 2) the temporal calibration, 3) the patient-to-image registration and 4) the mean intial MRI-ultrasound misalignment. IBIS NeuroNav was found to have an accuracy similar to other comparable systems in the literature.The goal of the second paper was to present a new technique for the rigid registration of the preoperative MRI to the pre-resection intraoperative ultrasound. Initially these images generally have a slight misalignment. However, surgeons find ultrasound images easier to interpret when they are properly aligned with MRI. The results of our investigation showed that the proposed registration technique robustly improved the MRI–ultrasound alignment when compared with the initial alignment.The objective of the third paper was to test rigid and non-rigid registration techniques to better align the pre- and post-resection ultrasound images to facilitate interpretation of the latter. A simple correlation coefficient based nonlinear registration proved to significantly improve the alignment between the pre- and post-resection ultrasound images. One of the biggest challenges of many technical scientists in the field of medical imaging is to find clinical images on which to validate new image processing algorithms. To address this issue, the fourth paper presents an online database in which we share our acquired preoperative MRI and intraoperative ultrasound images with the medical imaging community. We hope that this work will make it easier for neurosurgeons to use intraoperative ultrasound to guide glioma surgery and will eventually lead to improved surgical accuracy and prolonged patient survival.Les gliomes malins sont les tumeurs primaires les plus répandues chez l'adulte. Contrairement aux métastases cérébrales qui ont des contours bien définis, les gliomes malins infiltre le cerveau environnant et ont souvent des contours plus indistincts. En présence d'un gliome, en général la résection chirurgicale est l'approche privilégiée. Par ailleurs, dans un cas sur deux les neurochirurgiens laissent involontairement une partie de la tumeur. Deux facteurs principaux sont responsables de cet état de fait. Premièrement, la plupart des systèmes de neuronavigation actuels sont basés sur des images préopératoires. Parce que le cerveau subit d'importants changements lors de la chirurgie, ces images perdent en précision au fil de l'opération. En second lieu, les limites d'un gliome sont souvent difficiles à déterminer de façon précise, à la fois avec le sens de la vue et du toucher. Cette situation est regrettable puisqu'une résection à la fois maximale et sécuritaire de ces tumeurs est corrélée avec une survie prolongée des patients présentant un gliome de bas ou de haut grade. L'imagerie peropératoire permet d'obtenir des images en temps réel, aidant ainsi le chirurgien à faire une résection plus complète, tout en protégeant les tissus sains. Dans cette thèse j'ai étudié l'usage de l'ultrason peropératoire afin de guider la résection d'un gliome. À cette fin, j'ai utilisé le prototype de système de neuronavigation développé dans notre groupe de recherche : le système IBIS NeuroNav. Le but du premier article était d'évaluer la précision d'IBIS NeuroNav. Quatre composants du système ont été considérés : 1) le calibrage de la sonde ultrason 2) le calibrage temporel 3) le recalage patient-image et 4) le recalage IRM-ultrason. Nous avons constaté qu'IBIS NeuroNav avait une précision similaire aux autres systèmes comparables présentés dans la littérature. Le but du deuxième article était de présenter une nouvelle technique de recalage rigide entre l'IRM préopératoire et l'ultrason pré-résection intraopératoire. Au départ, ces images sont généralement légèrement désalignées. Or, les chirurgiens trouvent l'interprétation des images ultrasons plus facile lorsqu'elles sont correctement alignées avec l'IRM. Nos résultats montrent que la nouvelle technique proposée améliore de façon significative l'alignement IRM-ultrason.Le but du troisième article était de tester des méthodes de recalage rigide et non-rigide pour améliorer l'alignement des images ultrasons pré- et post-opératoires, afin de faciliter l'interprétation des seconds. Nous avons trouvé qu'une méthode de recalage utilisant un simple coefficient de corrélation améliorait significativement cet alignement. Un des nombreux défis des scientifiques techniques du domaine de l'imagerie médicale est de trouver des images cliniques sur lesquelles valider leurs nouveaux algorithmes. L'objectif du quatrième papier était précisément de pallier à cette difficulté en partageant avec la communauté scientifique les images acquises pour les papiers précédents. Nous sommes confiants que les résultats présentés dans cette thèse faciliteront l'utilisation par les neurochirurgiens des ultrasons peropératoires. Une survie prolongée de trop nombreux patients en dépend!
43
Zayat, Ahmed Salem. "Confounding factors in musculoskeletal ultrasound". Thesis, University of Leeds, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.574628.
Testo completoAbstract (sommario):
Musculoskeletal ultrasound (US) is an imaging modality with the potential to revolutionise the way we practise rheumatology. Ultrasound has been shown to be more sensitive and valid when compared to conventional imaging methods and clinical examination in the assessment of inflammatory arthropathies (lA). However, major limitations to its widespread use have been its perceived poor reliability and unknown diagnostic discriminative ability. Image acquisition is a key point for improving reliability. A systematic literature review was performed and a survey of experts was obtained in order to understand the important confounding factors in image acquisition. The effect of two of these factors on synovitis detection was then examined. Non-steroidal anti-inflammatory drugs (NSAIDs) usage was found to significantly mask both grey scale (GS) and power Doppler (PD) signal and resultedinlower assessment of disease activity. Change in the joint position during scanning was found to significantly alter US findings in patients with lA. Scanning the hands in a flat position and the knees in a 30° position provided the highest GS and PD scores suggesting that they may be the optimal scanning positions. The ability of US to discriminate rheumatoid arthritis (RA) from other diseases by detecting bone erosions was explored by examining the specificity of US detected bone erosion. The overall presence of US detected erosions was not a specific fmding for RA. However, erosions in certain anatomical sites were specific for RA. In conclusion, this thesis has demonstrated that certain factors. including concurrent NSAID intake and joint position can affect US image acquisition. Ultrasound does / IV have the ability to discriminate RA from other diseases by specifically detecting bone erosions in target joints. Standardisation of the US confounding factors and better understanding of the specificity of common US findings may enhance the role of US in the assessment of IA.
44
Dance, C. R. "Computing models from 3D ultrasound". Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598263.
Testo completoAbstract (sommario):
The computation of geometric models is a central task in imaging science, but it has only been attempted recently for 3D ultrasound. This thesis considers the case of 3D free-hand ultrasound in which a position sensor is attached to a conventional 2D probe. This is an inexpensive, safe and portable technique. However, ultrasound images typically have lower resolutions than images obtained by other clinical modalities and they contain spatially correlated speckle noise. Furthermore, the position and orientation information available is non-ideal and image planes may be irregularly located. Model computation is decomposed into three stages: segmentation, in which the boundaries of organs are located on individual 2D images, registration, in which the boundaries from different scans are aligned to compensate for sensor imperfections and organ motions, and reconstruction, in which 2D boundaries are combined into 3D models. Segmentation is performed by active contours. These enable the use of prior information about the shape of an organ boundary and can therefore be made reliable for noisy images. The aim has been to generate a fast, repeatable and easy to use semi-automated segmentation system. This has been achieved by incorporating a novel method for the propagation of trial active contour shapes between frames of a 3D ultrasound sequence. An intuitive graphical user interface has also been an important part of the design. Segmentations of real scan sequences are discussed and the performance of the scheme is closely evaluated. Registration is achieved by matching points from contours obtained through segmentation. Each image plane is moved by a rigid body transform and all planes are moved simultaneously. This is more efficient than alignment directly from images since it considers few correspondences. It is also more accurate than iterative approaches which align each plane in turn with previously moved planes. Novel matching schemes and means of moving planes are proposed. Regularisation by a model of likely organ motions is necessary since the problem is ill-posed; without such a model, registered contours can less closely resemble the true organ than unregistered ones. Registrations of synthetic and real contours are analysed.
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Housden, R. J. "Clinically practical freehand 3D ultrasound". Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604263.
Testo completoAbstract (sommario):
In this thesis, various alternatives to standard sensor systems are developed, with particular emphasis on improving the practicality of freehand 3D ultrasound in a clinical environment. The novel algorithms presented here are able to position a sequence of image frames qualitatively correctly even when the direction of out-of-plane motion is allowed to vary, which was not previously possible. Existing work on the subject of six-degree-of-freedom sensorless reconstruction found that it is possible to take unbiased measurements from a sensorless reconstruction, provided it is constrained to have only elevational motion and has a large proportion of fully developed speckle data. Alternatively, freehand motion and data from real tissue can be allowed at the expense of some large-scale drift in the frame positions, biasing the measurements. The approach of this thesis allows fully freehand motion and scans on any type of tissue, but consequently is found to have a drift error in the length and tilt of the sequence which can result in length measurement errors of 20% or more. A hybrid approach reintroduces position sensors, in combination with the image-based techniques. This thesis considers two sensors for use in the hybrid system. One of these is the Xsens MT9-B, which uses Micro-Electro-Mechanical Systems (MEMS) magnetometers, accelerometers and rate gyroscopes to measure orientations. This was found to be particularly unobtrusive having almost no effect on the scanning setup and protocol. A hybrid reconstruction using the MT9-B has an estimated overall length error of 5% of the sequence length and an orientation error of no more than 1°. A hybrid system using the MT9-B represents a significant step towards the goal of accurate anatomical measurements with an easy-to-use scanning system.
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Hsu, P. W. "Freehand three- dimensional ultrasound calibration". Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604687.
Testo completoAbstract (sommario):
In this thesis, we investigate how to achieve an accurate reliable and rapid probe calibration. Our first step is to improve the reliability of an accurate calibration technique from the literature. The Cambridge phantom, a variant of plane-based calibration, has been shown to be one of the most accurate calibration techniques. Unfortunately, calibrations performed using plane-based techniques are often unreliable. We show how it is possible to provide feedback on the reliability of the calibration. This allows the user to rectify an unreliable calibration. Having achieved an accurate and reliable calibration, we now search for a fast and easy calibration technique. We study a class of two-dimensional alignment phantoms – the Z-fiducial phantom. Probe calibration using such a phantom only requires a single image of the phantom. However, calibration speed using this phantom is impeded by the necessity of segmenting isolated points on the phantom reliably, which requires human intervention. We solve this problem by mounting a thin rubber membrane on top of the phantom. The membrane is segmented automatically and the phantom features can be easily located. This enables us to segment isolated points automatically at the full PAL frame rate of 25Hz, enabling calibration to be completed in a few seconds. In addition, to improve the existing calibration techniques, we present two novel phantoms – the cone phantom and the Cambridge stylus. They are both simple in design, easy to use and produce accurate calibrations. The cone phantom produces calibrations with accuracies matching the Cambridge phantom. The Cambridge stylus is small in size and can be carried around conveniently. These phantoms offer alternatives to the Cambridge phantom and the Z-phantom, ensuring calibration reliability and simplicity, while producing accurate calibrations.
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Choi, Doowon. "Ultrasound propagation in various gases". Thesis, University of Warwick, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250087.
Testo completo
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Silva-Martinez, Susana. "Applications of ultrasound in electrochemistry". Thesis, University of Southampton, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242670.
Testo completo
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Gilbertson, Matthew Wright. "Handheld force-controlled ultrasound probe". Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/63232.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 129-131).
An hand-held force controlled ultrasound probe has been developed. The controller maintains a prescribed contact force between the probe and a patient's body. The device will enhance the diagnostic capability of free-hand elastography, swept-force compound imaging, and make it easier for a technician to acquire repeatable (i.e. directly comparable) images over time. The mechanical system consists of an ultrasound probe, ballscrew-driven linear actuator, and a force/torque sensor. The feedback controller commands the motor to rotate the ballscrew to translate the ultrasound probe in order to maintain a desired contact force. In preliminary user studies it was found that the control system maintained a constant contact force with 1.7 times less variation than human subjects who watched a force gauge. Users without a visual force display maintained a constant force with 20 times worse variation. The system was also used to determine the viscoelastic properties of soft tissue. In three mock ultrasound examinations one hour apart in which the goal was two obtain two consistent images at the same force, an unassisted operator obtained the second image at a 20% lower force, while the operator assisted by the controller obtained the same force to within <2%. The device enables users to gather more force-consistent images over time.
by Matthew Wright Gilbertson.
S.M.
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Koegelenberg, Coenraad Frederik Nicolaas. "Ultrasound-assisted transthoracic diagnostic techniques". Thesis, Stellenbosch : University of Stellenbosch, 2011. http://hdl.handle.net/10019.1/18054.
Testo completoAbstract (sommario):
Thesis (PhD)--University of Stellenbosch, 2011.ENGLISH ABSTRACT: Although transthoracic ultrasonography is a well established modality, it is still underutilised by chest physicians. The aim of this research project was to investigate the feasibility, diagnostic yield and safety of ultrasound(US)-assisted transthoracic biopsies performed by clinicians in various settings relevant to daily practice of respiratory medicine. We conducted four clinical trials which are summarised below: 1. In a prospective study on the feasibility of US-assisted transthoracic fine needle aspiration (TTFNA) of drowned lung secondary to a proximal mass lesion, a novel indication for US-assisted TTFNA was described. TTFNA passes >20mm from the visceral pleura had a sensitivity of 74.2% and were also more likely to contain malignant cells than more superficial passes. The surprisingly high yield and the fact that no serious complications were observed validated this approach, which may be an alternative to bronchoscopy. 2. In the largest single-centre study on US-assisted TTFNA with rapid on-site evaluation (ROSE) and cutting needle biopsy (CNB) in the setting of superior vena cava (SVC) syndrome ever reported, we were able to accurately diagnose 96% of all patients who presented with an associated mass lesion that abutted or infiltrated the chest wall. No pneumothoraces or major haemorrhage was caused. We also validated the single-session approach, and were able to conclude that US-assisted TTFNA (with ROSE) is the initial investigation of choice in suspected bronchogenic carcinoma, whereas both TTFNA and CNB need to be performed in all other cases. 3. We continued to validate the novel single-session sequential approach in a study on anterosuperior mediastinal masses. US-assisted TTFNA with ROSE was performed on 45 consecutive patients, immediately followed by CNB where a provisional diagnosis of epithelial carcinoma or probable tuberculosis (TB) could not be established. An accurate cytological diagnosis was made in 73.3%, and was more likely to be diagnostic in epithelial carcinoma and TB than all other pathology (p<0.001). CNB yielded a diagnosis in 88.2%. Overall 93.3% of patients were diagnosed by the single-session approach. No pneumothorax or major haemorrhage was observed. 4. In a prospective study, we compared US-assisted Abrams and Tru-Cut needle biopsies with regard to their yield for pleural TB. Pleural biopsy specimens obtained with Abrams needles contained pleural tissue in 91.0% of cases and were diagnostic in 81.8%, whereas Tru-Cut needle biopsy specimens only contained pleural tissue in 78.7% (p=0.015) and were diagnostic in 65.2% (p=0.022). In conclusion, we investigated the feasibility of US-assisted biopsies performed by respiratory physicians in various settings, and consistently found acceptable to very high diagnostic yields with minimal complications. Furthermore, we were able to validate a novel indication for US-assisted TTFNA (US-assisted TTFNA of drowned lung), validate the use of a single-session sequential approach (USassisted TTFNA with ROSE followed by CNB where indicated) in at least two clinical settings (SVC syndrome and anterosuperior mediastinal masses) and we were able to show that US-assisted Abrams needle biopsy is superior to Tru-Cut needles biopsy when histological confirmation of TB pleuritis is required.
AFRIKAANSE OPSOMMING: Alhoewel transtorakale ultrasonografie ‘n gevestigde modaliteit is, word dit onderbenut deur pulmonoloë. Die doel van hierdie navorsingsprojek was om die praktiese uitvoerbaarheid, diagnostiese opbrengs en veiligheid van sonargerigte transtorakale biopsies uitgevoer deur klinici in verskeie situasies relevant tot die alledaagse praktyk te ontleed. Ons het vier kliniese proewe uitgevoer wat hieronder opgesom word: 1. In ‘n prospektiewe studie oor die praktiese uitvoerbaarheid van sonargerigte transtorakale fyn naald aspirasie (TTFNA) van areas van obstruktiewe pneumonitis sekondêr tot proksimale massa letsels, is ‘n nuwe indikasie vir sonargerigte TTFNA beskryf. TTFNA aspirasies wat >20mm van die visserale pleura geneem is, het ‘n sensitiwiteit van 74.2% gehad en was meer geneig om maligne selle op te lewer as meer oppervlakkige aspirasies. Die verbasende hoë diagnostiese sensitiwiteit en afwesigheid van ernstige komplikasies het die praktiese waarde van hierdie benadering bevestig. 2. In die grootste studie nog oor sonargerigte TTFNA met spoedige in-teater evalusies (SITE) en sny-naald biopsie (SNB) in die teenwoordigheid van superior vena cava (SVC) sindroom, kon ons 96% van pasiënte wat presenteer het met ‘n geassosieerde massa letsel wat die borskaswand betrek, akkuraat diagnoseer. Geen pneumotoraks of major bloeding is waargeneem nie. Ons kon ook die praktiese uitvoerbaarheid van ‘n enkelsessie benadering bevestig en kon tot die gevolgtrekking kom dat sonargerigte TTFNA (met SITE) die aanvanklike ondersoek van keuse is waar bronguskarsinoom vermoed word, maar dat beide TTFNA en SNB noodsaaklik is in ander gevalle. 3. Ons het voortgegaan om die waarde van die nuwe enkel-sessie benadering te bevestig in ‘n studie oor antero-superior mediastinale massas. Sonargerigte TTFNA met SITE is uitgevoer op 45 pasiënte en in gevalle waar ‘n voorlopige diagnose van epiteliale karsinoom of waarskynlike tuberkulose (TB) nie bevestig kon word nie, is dit onmiddelik gevolg deur SNB. ‘n Akkurate sitologiese diagnose is gemaak in 73.3% van gevalle en meer algemeen in epiteliale karsinoom en TB as ander patologie (p<001). SNB was diagnosties in 88.2%. In 93.3% kon ‘n diagnose verkry word met die enkel-sessie benadering. Geen pneumotoraks of major bloeding is waargeneem nie. 4. In ‘n prospektiewe studie is sonargerigte Abrams naald en Tru-Cut naald biopsies se opbrengs vir pleurale TB met mekaar vergelyk. Pleurale biopsie monsters wat met ‘n Abrams naalde geneem is, het pleurale weefsel in 91.0% gevalle getoon en was diagnosties in 81.8%, vergeleke met Tru-Cut naalde wat slegs in 87.7% pleurale weefsel opgelewer het (p=0.015) en wat net in in 65.2% diagnosties was (p=0.022). Opsommend het ons die praktiese uitvoerbaarheid van sonargerigte biopsies uitgevoer deur pulmonoloë in veskeie kliniese situasies nagevors, en het deurlopend aanvaarbare tot hoë diagnostiese opbrengste gevind met minimale komplikasies. Verder kon ons ‘n nuwe indikasie vir sonargerigte TTFNA beskryf en evalueer (sonargerigte TTFNA van obstruktiewe pneumonitis); ‘n enkel-sessie sekwensiële benadering se waarde bevestig (sonargerigte TTFNA met SITE, gevolg deur SNB waar aangedui) in ten minste twee kliniese situasies (SVC sindroom en anterosuperior mediastinale massas); en was dit moontlik om te bewys dat UK-geleide Abrams naald biopsies superior tot Tru-cut naald biopsies is in die histologiese bevestiging van TB pleuritis.