Academic literature on the topic 'MRI sequence parameters'
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Journal articles on the topic "MRI sequence parameters"
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Jarraya, Mohamed, Rafael Heiss, Jeffrey Duryea, Armin M. Nagel, John A. Lynch, Ali Guermazi, Marc-André Weber, et al. "Bone Structure Analysis of the Radius Using Ultrahigh Field (7T) MRI: Relevance of Technical Parameters and Comparison with 3T MRI and Radiography." Diagnostics 11, no. 1 (January 12, 2021): 110. http://dx.doi.org/10.3390/diagnostics11010110.
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Bone fractal signature analysis (FSA—also termed bone texture analysis) is a tool that assesses structural changes that may relate to clinical outcomes and functions. Our aim was to compare bone texture analysis of the distal radius in patients and volunteers using radiography and 3T and 7T magnetic resonance imaging (MRI)—a patient group (n = 25) and a volunteer group (n = 25) were included. Participants in the patient group had a history of chronic wrist pain with suspected or confirmed osteoarthritis and/or ligament instability. All participants had 3T and 7T MRI including T1-weighted turbo spin echo (TSE) sequences. The 7T MRI examination included an additional high-resolution (HR) T1 TSE sequence. Radiographs of the wrist were acquired for the patient group. When comparing patients and volunteers (unadjusted for gender and age), we found a statistically significant difference of horizontal and vertical fractal dimensions (FDs) using 7T T1 TSE-HR images in low-resolution mode (horizontal: p = 0.04, vertical: p = 0.01). When comparing radiography to the different MRI sequences, we found a statistically significant difference for low- and high-resolution horizontal FDs between radiography and 3T T1 TSE and 7T T1 TSE-HR. Vertical FDs were significantly different only between radiographs and 3T T1 TSE in the high-resolution mode; FSA measures obtained from 3T and 7T MRI are highly dependent on the sequence and reconstruction resolution used, and thus are not easily comparable between MRI systems and applied sequences.
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Held, Paul. "MRI of orofacial tumors and paragangliomas with 2D GE sequences: indications and optimal sequence parameters." European Journal of Radiology 18, no. 1 (February 1994): 38–44. http://dx.doi.org/10.1016/0720-048x(94)90364-6.
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Soltanian-Zadeh, H., R. Saigal, J. P. Windham, A. E. Yagle, and D. O. Hearshen. "Optimization of MRI protocols and pulse sequence parameters for eigenimage filtering." IEEE Transactions on Medical Imaging 13, no. 1 (March 1994): 161–75. http://dx.doi.org/10.1109/42.276155.
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Wilson, M., P. Morgan, and L. Blumhardt. "Quantitative diffusion characteristics of the human brain depend on MRI sequence parameters." Neuroradiology 44, no. 7 (July 2002): 586–91. http://dx.doi.org/10.1007/s00234-002-0797-8.
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Ford, John, Nesrin Dogan, Lori Young, and Fei Yang. "Quantitative Radiomics: Impact of Pulse Sequence Parameter Selection on MRI-Based Textural Features of the Brain." Contrast Media & Molecular Imaging 2018 (July 30, 2018): 1–9. http://dx.doi.org/10.1155/2018/1729071.
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Objectives. Radiomic features extracted from diverse MRI modalities have been investigated regarding their predictive and/or prognostic value in a variety of cancers. With the aid of a 3D realistic digital MRI phantom of the brain, the aim of this study was to examine the impact of pulse sequence parameter selection on MRI-based textural parameters of the brain. Methods. MR images of the employed digital phantom were realized with SimuBloch, a simulation package made for fast generation of image sequences based on the Bloch equations. Pulse sequences being investigated consisted of spin echo (SE), gradient echo (GRE), spoiled gradient echo (SP-GRE), inversion recovery spin echo (IR-SE), and inversion recovery gradient echo (IR-GRE). Twenty-nine radiomic textural features related, respectively, to gray-level intensity histograms (GLIH), cooccurrence matrices (GLCOM), zone size matrices (GLZSM), and neighborhood difference matrices (GLNDM) were evaluated for the obtained MR realizations, and differences were identified. Results. It was found that radiomic features vary considerably among images generated by the five different T1-weighted pulse sequences, and the deviations from those measured on the T1 map vary among features, from a few percent to over 100%. Radiomic features extracted from T1-weighted spin-echo images with TR varying from 360 ms to 620 ms and TE = 3.4 ms showed coefficients of variation (CV) up to 45%, while up to 70%, for T2-weighted spin-echo images with TE varying over the range 60–120 ms and TR = 6400 ms. Conclusion. Variability of radiologic textural appearance on MR realizations with respect to the choice of pulse sequence and imaging parameters is feature-dependent and can be substantial. It calls for caution in employing MRI-derived radiomic features especially when pooling imaging data from multiple institutions with intention of correlating with clinical endpoints.
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Shahi, Anamika, Satya Sundar Gajendra Mohapatra, and Supriya Mishra. "MRI evaluation of pediatric posterior fossa tumors and its correlation with histopathology: A prospective observational study." Journal of Associated Medical Sciences 56, no. 1 (January 3, 2023): 121–32. http://dx.doi.org/10.12982/jams.2023.015.
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Background: The commonest malignancy in the pediatric age group is leukemia, followed by brain tumors. Pediatric brain tumors are usually seen in children below 10 years. The incidence ranges from 1 to 3 per 100,000 cases. Primary intracranial tumors most commonly occur in the posterior fossa in children while infratentorial tumors are predominant in children over 4 years. Infratentorial tumors are more common overall, accounting for 45-60% of all cases. Physiologic characteristics of the pediatric posterior fossa tumors are well represented in advanced MRI techniques, which results in better pre-operative tumor evaluation, and often better results. Objectives: Primary intracranial tumors most commonly occur in the posterior fossa in children. Treatment and prognosis rely heavily on correct diagnosis. The most important modality for early diagnosis is MRI of the brain. This study aims to evaluate the role of MRI in pediatric posterior fossa tumors. Materials and methods: Thirty-three patients in the pediatric age group (<18 years) with a clinical suspicion of posterior fossa tumors, referred to the department of Radiology for undergoing MRI of the brain with contrast were included in the study. These patients underwent surgery followed by histopathological examination (HPE). Five parameters from conventional MRI were chosen and correlated with histopathology (gold standard). Statistical analysis was done subsequently. Results: Diffusion-weighted imaging (DWI) is the most accurate parameter (94%), followed by T2 weighted imaging (T2WI), gradient, and post-contrast sequence (91% each). Diffusion-weighted imaging and post-contrast sequence had the highest specificity (almost 96%) while DWI and T2WI had the highest sensitivity (90% each). All 5 parameters are useful in 85% of cases. Overall diagnostic accuracy of MRI was almost 94% compared to histopathology. Conclusion: DWI is the best parameter, followed by T2WI, gradient imaging, and post-contrast sequence. MRI is highly accurate in the evaluation of pediatric posterior fossa tumors. In centers where advanced MRI techniques cannot be performed, some parameters from conventional MRI can be selected that aid in diagnosis. Our study shows that judicious use of 5 parameters can increase sensitivity, specificity, and diagnostic accuracy of MRI for pediatric posterior fossa tumors.
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Patel, Daxa M., R. Shane Tubbs, Gigi Pate, James M. Johnston, and Jeffrey P. Blount. "Fast-sequence MRI studies for surveillance imaging in pediatric hydrocephalus." Journal of Neurosurgery: Pediatrics 13, no. 4 (April 2014): 440–47. http://dx.doi.org/10.3171/2014.1.peds13447.
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Object Surveillance imaging of the cerebral ventricles can be valuable in following up children with shunt-treated hydrocephalus. There also, however, has been recent increased awareness and concern over the potential risk associated with imaging-related radiation exposure in children. Magnetic resonance imaging represents an imaging alternative that does not use ionizing radiation; however, its practical utility has been limited due to the near-uniform requirement for sedation or general anesthesia in children. Magnetic resonance imaging without sedation is often futile because of the movement artifact produced by the nonsedated pediatric patient. Some studies have demonstrated the feasibility of using fast-sequence MRI (fsMRI), but the reported experiences are limited. The authors have incorporated fsMRI into their routine shunt surveillance imaging paradigms and report here a 5-year experience with this modality. Methods The authors initially started using fsMRI for routine surveillance in a single clinic in 2008 and have gradually increased their institutional utilization of this modality as experience has accumulated and protocols have been refined. Imaging sequences obtained for each child include an axial T2-weighted half-Fourier acquisition single-shot turbo spin-echo (HASTE), coronal T2-weighted HASTE, and sagittal T2-weighted HASTE images. The authors conducted a retrospective chart and imaging review. They rated each fsMR image according to 5 visibility parameters: 1) ventricle size, 2) ventricle configuration, 3) presence or absence of transependymal flow, 4) presence or absence of motion artifact, and 5) visualization of the ventricular catheter. Each parameter was graded as 1 (present) or 0 (absent). Thus, the maximum value assigned to each scan could be 5 and the minimum value assigned to each scan could be 0. Interrater reliability between pairs of observers was calculated using the Kendall's tau-b and intraclass coefficients. Results Two hundred patients underwent fsMRI. No child required sedation. The average duration of examinations was approximately 3.37 minutes, and mean age of the patients was 5.7 years. Clinically useful images were attained in all cases. Overall quality of the fsMRI studies based on the 5 different visibility parameters showed that 169 images (84.5%) included 4 or 5 parameters (score ≥ 4) and had statistically significant excellent quality. The Kendall's tau-b for the overall fsMRI ratings was 0.82 (p = 0.002) and the intraclass coefficient was 0.87 (p < 0.0001). Conclusions In the present cohort of 200 patients, fsMRI studies were shown to have an excellent overall quality and a statistically significant high degree of interrater reliability. Consequently, the authors propose that fsMRI is a sufficiently effective modality that eliminates the need for sedation and the use of ionizing radiation and that it should supplant CT for routine surveillance imaging in hydrocephalic patients.
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Chen, Wen-Chang, Yen-Hung Ho, Song-Shei Lin, Lan Zhang, I.-Tsang Chiang, and Wei-Ming Lin. "Sensitivity of Pre-Contrast Multiphase versus Conventional Liver MRI in Diagnosing Hepatic Hemangioma." Journal of Medical Imaging and Health Informatics 10, no. 11 (November 1, 2020): 2728–32. http://dx.doi.org/10.1166/jmihi.2020.3207.
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Hepatic hemangioma (HH) can be diagnosed noninvasively via dynamic contrast enhancement computed tomography, magnetic resonance imaging (MRI) or ultrasonography. Diagnosis HH is based on imaging features such as early arterial phase enhancement and persistence enhancement on portal or delayed phase. However, differentiating small or atypical hemangiomas from other hepatic masses using these imaging methods maybe be difficult, especially in patients with a medical history of malignant disease. Another challenge in clinical practice is when patients with acute or chronic renal insufficiency, use MRI contrast agent gadolinium (Gd) with the risk of nephrogenic systemic fibrosis. Differentiating hemangioma from its mimickers on preoperative imaging studies is of critical importance. Our study compared the diagnostic sensitivity of pre-contrast multiphase and conventional liver MRI. Total 80 patients with HH were participate to our study retrospectively. Imaging was performed using pre-contrast multiphase and conventional liver MRI methods. The size of the nodule/mass to be evaluated was ≥1 cm. All patients MRI images were obtained and classified into two groups based on the acquisition parameters. The first group with pre-contrast multiphase MRI sequences, and the second group of conventional liver MRI methods included pre-contrast multiphase MRI sequences, contrast-enhanced tri-phase sequences. The study was reviewed and analyzed by two independence gastrointestinal radiologists, who were blinded to the examination and follow-up study results. The diagnostic sensitivity was compared between pre-contrast multiphase MRI sequences only and conventional liver MRI sequences methods. Based on the observation of two gastrointestinal radiologists, our results showed mean sensitivity of 90.0% and 97.5% for pre-contrast multiphase MRI and conventional liver MRI, respectively. Pre-contrast multiphase MRI sequence methods may be reliably applied in the diagnosis of HH.
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Thieleking, Ronja, Rui Zhang, Maria Paerisch, Kerstin Wirkner, Alfred Anwander, Frauke Beyer, Arno Villringer, and A. Veronica Witte. "Same Brain, Different Look?—The Impact of Scanner, Sequence and Preprocessing on Diffusion Imaging Outcome Parameters." Journal of Clinical Medicine 10, no. 21 (October 27, 2021): 4987. http://dx.doi.org/10.3390/jcm10214987.
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In clinical diagnostics and longitudinal studies, the reproducibility of MRI assessments is of high importance in order to detect pathological changes, but developments in MRI hard- and software often outrun extended periods of data acquisition and analysis. This could potentially introduce artefactual changes or mask pathological alterations. However, if and how changes of MRI hardware, scanning protocols or preprocessing software affect complex neuroimaging outcomes from, e.g., diffusion weighted imaging (DWI) remains largely understudied. We therefore compared DWI outcomes and artefact severity of 121 healthy participants (age range 19–54 years) who underwent two matched DWI protocols (Siemens product and Center for Magnetic Resonance Research sequence) at two sites (Siemens 3T Magnetom Verio and Skyrafit). After different preprocessing steps, fractional anisotropy (FA) and mean diffusivity (MD) maps, obtained by tensor fitting, were processed with tract-based spatial statistics (TBSS). Inter-scanner and inter-sequence variability of skeletonised FA values reached up to 5% and differed largely in magnitude and direction across the brain. Skeletonised MD values differed up to 14% between scanners. We here demonstrate that DTI outcome measures strongly depend on imaging site and software, and that these biases vary between brain regions. These regionally inhomogeneous biases may exceed and considerably confound physiological effects such as ageing, highlighting the need to harmonise data acquisition and analysis. Future studies thus need to implement novel strategies to augment neuroimaging data reliability and replicability.
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Drake-Pérez, M., B. M. A. Delattre, J. Boto, A. Fitsiori, K. O. Lovblad, S. Boudabbous, and M. I. Vargas. "Normal Values of Magnetic Relaxation Parameters of Spine Components with the Synthetic MRI Sequence." American Journal of Neuroradiology 39, no. 4 (March 1, 2018): 788–95. http://dx.doi.org/10.3174/ajnr.a5566.
Full textDissertations / Theses on the topic "MRI sequence parameters"
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Kosková, Markéta. "Vliv MR pulsních sekvencí na teplotu měřeného objektu." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2016. http://www.nusl.cz/ntk/nusl-242059.
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This paper deals with the effect of the MR pulse sequences on the temperature of the measured object. The theoretical part is dedicated to basic principle of magnetic resonance, the selected pulse sequences and risks that are connected with MRI. There is also described the draft of the testing phantom and information about the measurement and record of temperature during MR measurement. In the experimental part the effect of RF coils, pulse sequences and parameters of pulse sequences are tested on drafted phantom with experimental MR device located at the Institut of Scientific Instruments of the AS CR in Brno. These findings are then tested on live laboratory mouse. All results are analyzed and used as default data for developed simulation program.
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Bhushan, Manav. "Motion correction and parameter estimation in DCE-MRI sequences : application to colorectal cancer." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:1793b0c1-7f2a-41cb-8427-c6927379056e.
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Cancer is one of the leading causes of premature deaths across the world today, and there is an urgent need for imaging techniques that can help in early diagnosis and treatment planning for cancer patients. In the last four decades, magnetic resonance imaging (MRI) has emerged as one of the leading modalities for non-invasive imaging of tumours. By using dynamic contrast-enhanced magnetic resonance imaging (DCEMRI), this modality can be used to acquire information about perfusion and vascularity of tumours, which can help in predicting response to treatment. There are many factors that complicate the analysis of DCE-MRI data, and make clinical predictions based on it unreliable. During data acquisition, there are many sources of uncertainties and errors, especially patient motion, which result in the same image position being representative of many different anatomical locations across time. Apart from motion, there are also other inherent uncertainties and noise associated with the measurement of DCE-MRI parameters, which contribute to the model-fitting error observed when trying to apply pharmacokinetic (PK) models to the data. In this thesis, a probabilistic, model-based registration and parameter estimation (MoRPE) framework for motion correction and PK-parameter estimation in DCE-MRI sequences is presented. The MoRPE framework is first compared with conventional motion correction methods on simulated data, and then applied to data from a clinical trial involving twenty colorectal cancer patients. On clinical data, the ability of MoRPE to discriminate between responders and non-responders to combined chemoand radiotherapy is tested, and found to be superior to other methods. The effect of incorporating different arterial input functions within MoRPE is also assessed. Following this, a quantitative analysis of the uncertainties associated with the different PK parameters is performed using a variational Bayes mathematical framework. This analysis provides a quantitative estimate of the extent to which motion correction affects the uncertainties associated with different parameters. Finally, the importance of estimating spatial heterogeneity of PK parameters within tumours is assessed. The efficacy of different measures of spatial heterogeneity, in predicting response to therapy based on the pre-therapy scan alone are compared, and the prognostic value of a new derived PK parameter the 'acceleration constant' is investigated. The integration of uncertainty estimates of different DCE-MRI parameters into the calculation of their heterogeneity measures is also shown to improve the prediction of response to therapy.
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Pereira, Cláudio. "MRI (1.5 and 3 Tesla) sequence optimization for use in Orthopaedics." Master's thesis, 2016. http://hdl.handle.net/10400.26/18224.
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Contexto: Existe, actualmente, uma incessante necessidade por exames imagiológicos melhores e mais rápidos no campo da Ressonância Magnética Imagiológica (RMI) clinica. Isto é particularmente verdade em RMI músculo-esquelética (MSK), na qual longas listas de espera são um problema constante. Para além disto, fundos para adquirir ou actualizar equipamentos imagiológicos encontram-se totalmente ou parcialmente cortados, devido à difícil situação financeira na qual a maioria dos Sistemas de Saúde se encontra. Este projecto pretende avaliar se e até que ponto a Optimização de Sequências de RMI pode ser uma resposta ao desafio de melhorar a qualidade de imagem (QI) e reduzir o Tempo de Aquisição (TA) sem recurso a investimento financeiro.
Metodologia: Foram criadas Sequências Optimizadas (SO), para scanners de 1,5 e 3 Tesla, que se focaram em obter a melhor relação QI/TA. As SO foram desenvolvidas pegando em sequências RMI genéricas, já disponibilizadas pelos fabricantes nos scanners, e depois manipulando os seus parâmetros RMI através de um processo iterativo, em conjunção com várias antenas RMI receptoras e fantomas de RMI biológicos e não biológicos. Após a melhor relação QI/TA ter sido estabelecida, para cada sequência, estas foram usadas para criar réplicas dos protocolos padrão do Departamento de RMI. A diferença em TA entre os protocolos velhos e os novos foi calculada para medir a redução de TA obtida. A mudança em QI foi avaliada através análise visual retrospectiva efectuada por avaliadores cegos, os quais tinham extensa experiência em RMI MSK. As respostas dos avaliadores foram registadas através de um questionário padrão que se focou na QI geral e em aspectos técnicos específicos (exemplo: Resolução Espacial, Contraste, Artefactos, etc.)
Resultados: A redução média no TA foi de 6 minutos e 48 segundos por exame. Esta redução intensificou-se em protocolos com um maior número de sequências. T1 foi a ponderação que demonstrou maior redução do TA. No geral os avaliadores consideraram que as imagens obtidas com SO tinham melhor ou muito melhor QI que as imagens obtidas com sequências não optimizadas. Esta tendência esteve também presente para todos os aspectos técnicos de QI avaliados (p <0.05), exceptuando: Relação Sinal-Ruído e Artefactos. T1 foi a ponderação na qual houve maior melhoria da QI. Foi notado que as SO produziam mais barulho e maior Taxa de Absorção Especifica que as sequências não optimizadas, embora os níveis de segurança tenham sido respeitados.
Conclusões: A Optimização de Sequências é um método útil para melhorar a QI e reduzir o TA, que não precisa de investimento monetário significativo. Naturalmente tem os seus limites mas, caso seja empregue correctamente por técnicos entendidos em RMI, é uma ferramenta versátil que pode fazer a diferença na qualidade de imagem e na carga de trabalho expedida pelo scanner.Background: There is currently a nonstop necessity for faster and improved imaging, in the field of clinical Magnetic Resonance Imaging (MRI). This is particularly true in Musculoskeletal (MSK) MRI, were long waiting lists are a constant problem. In addition, funds to acquire or upgrade imaging equipment have been fully or partially cut, due to the difficult financial situation that most Healthcare Systems find themselves in. The project developed aims to evaluate if and to what extent MRI Sequence Optimization can be an answer to the challenge of improving Image Quality (IQ) and decreasing scan time duration without financial investment. Methodology: Optimized Sequences (OS) were created, for both 1.5 and 3 Tesla MRI scanners, which focused on providing the best Image Quality (IQ)/Time of Acquisition (TA) relationship. OS were developed by taking generic MRI sequences, already available in the scanners by the manufacturer, and then manipulating their MRI parameters using an iterative process in conjunction with several receiving Coils, and both non-biological and biological MRI phantoms. After the best IQ/TA relation was establish, for each sequence, they were used to create replicas of the MRI Department’s standard MRI protocols. The difference in TA between the old and new MRI protocols was calculated to measure the reduction in TA obtained. IQ change was assessed through retrospective visual analysis by several blinded assessors, which had extensive experience in MSK MRI. The assessor’s answers were recorded using a standard questionnaire that focused on overall IQ and also on specific technical aspects (e.g. Spatial Resolution, Contrast, Artefacts, etc.) Results: The average reduction in TA measured was 6 minutes & 48 seconds per examination. TA reduction was more marked for protocols with a higher number of sequences. T1 was the weight type that showed a more marked TA reduction. Overall the assessors deemed that images produced from OS had either better or significantly better IQ than images produced with non-OS sequences. This trend was also present for all IQ’s technical aspect assessed (p<0.05), with exception on Signal-to-Noise Ratio and Artefacts. T1 was considered the weight type were the most IQ improvement was observed. It was also noted that OS sequences produced higher audio noise and Specific Absorption Rate compared to non-OS, but that the safety levels were respected. Conclusion: Sequence Optimization is indeed a useful method to improve IQ and reduce TA, without requiring any significant monetary investment. Obviously it has its limits but, if employed correctly by MRI knowledgeable technicians, it is a versatile tool that can make a significant improvement in scanner workload output and image quality.
Book chapters on the topic "MRI sequence parameters"
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Irrera, Pietro, Lorena Consolino, Walter Dastrù, Michael Pedersen, Frank G. Zöllner, and Dario Livio Longo. "Dynamic Contrast Enhanced (DCE) MRI-Derived Renal Perfusion and Filtration: Experimental Protocol." In Methods in Molecular Biology, 429–41. New York, NY: Springer US, 2021. http://dx.doi.org/10.1007/978-1-0716-0978-1_25.
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AbstractDynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) can provide a noninvasive way for assessing renal functional information following the administration of a small molecular weight gadolinium-based contrast agent. This method may be useful for investigating renal perfusion and glomerular filtration rates of rodents in vivo under various experimental (patho)physiological conditions. Here we describe a step-by-step protocol for DCE-MRI studies in small animals providing practical notes on acquisition parameters, sequences, T1 mapping approaches and procedures.This chapters is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol chapter is complemented by two separate chapters describing the basic concept and data analysis.
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Li, Lu-Ping, Bradley Hack, Erdmann Seeliger, and Pottumarthi V. Prasad. "MRI Mapping of the Blood Oxygenation Sensitive Parameter T2* in the Kidney: Basic Concept." In Methods in Molecular Biology, 171–85. New York, NY: Springer US, 2021. http://dx.doi.org/10.1007/978-1-0716-0978-1_10.
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AbstractThe role of hypoxia in renal disease and injury has long been suggested but much work still remains, especially as it relates to human translation. Invasive pO2 probes are feasible in animal models but not for human use. In addition, they only provide localized measurements. Histological methods can identify hypoxic tissue and provide a spatial distribution, but are invasive and allow only one-time point. Blood oxygenation level dependent (BOLD) MRI is a noninvasive method that can monitor relative oxygen availability across the kidney. It is based on the inherent differences in magnetic properties of oxygenated vs. deoxygenated hemoglobin. Presence of deoxyhemoglobin enhances the spin–spin relaxation rate measured using a gradient echo sequence, known as R2* (= 1/T2*). While the key interest of BOLD MRI is in the application to humans, use in preclinical models is necessary primarily to validate the measurement against invasive methods, to better understand physiology and pathophysiology, and to evaluate novel interventions. Application of MRI acquisitions in preclinical settings involves several challenges both in terms of logistics and data acquisition. This section will introduce the concept of BOLD MRI and provide some illustrative applications. The following sections will discuss the technical issues associated with data acquisition and analysis.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This introduction chapter is complemented by two separate chapters describing the experimental procedure and data analysis.
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Riederer, S. J., F. Farzaneh, and H. Z. Wang. "Two New Pulse Sequences for Efficient Determination of Tissue Parameters in MRI." In Tissue Characterization in MR Imaging, 48–53. Berlin, Heidelberg: Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-74993-3_8.
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"Scan Parameters for the Spin-Echo Imaging Sequence." In Fundamentals of MRI, 193–230. CRC Press, 2008. http://dx.doi.org/10.1201/b15767-14.
Full textConference papers on the topic "MRI sequence parameters"
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Magin, Richard L., and Dumitru Baleanu. "NMR Measurements of Anomalous Diffusion Reflect Fractional Order Dynamics." In ASME 2007 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/detc2007-34224.
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Diffusion weighted MRI is often used to detect and stage neurodegenerative, malignant and ischemic diseases. The correlation between developing pathology and localized diffusion measurements relies on the design of selective phase encoding pulses that alter the intensity of the acquired signal according to biophysical models of spin diffusion in tissue. The most common approach utilizes a bipolar or Stejskal-Tanner gradient pulse sequence to encode the apparent diffusion coefficient as an exponential, multi-exponential or stretched exponential function of experimentally-controlled parameters. Several studies have investigated the ability of the stretched exponential to provide an improved fit to diffusion-weighted imaging data. These results were recently analyzed by establishing a direct link between water diffusion, as measured using NMR, and fractal structural models of tissues. In this paper we suggest an alternative description for stretched exponential behavior that reflects fractional order dynamics of a generalized Bloch-Torrey equation in either space or time. Such generalizations are the basis for similar anomalous diffusion phenomena observed in optical spectroscopy, polymer dynamics and electrochemistry. Here we demonstrate a correspondence between the detected NMR signal and anomalous diffusional dynamics of water through the Riesz fractional order space derivative and the Caputo form of the fractional order Riemann-Liouville time derivative.
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Craciunescu, Oana I., Shiva K. Das, Terrence Z. Wong, and Thaddeus V. Samulski. "Fractal Reconstruction of Breast Perfusion Before and After Hyperthermia Treatments." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-33692.
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Thermal modeling for hyperthermia breast patients can provide relevant information to better understand the temperatures achieved during treatment. However, human breast is much perfused, making knowledge of the perfusion crucial to the accuracy of the temperature computations. It has been shown that the perfusion of blood in tumor tissue can be approximated using the relative perfusion index (RPI) determined from dynamic contrast-enhanced magnetic resonance imaging (DE-MRI). It was also concluded that the 3D reconstruction of tumor perfusion can be performed using fractal interpolation functions (FIF). The technique used was called piecewise hidden variable fractal interpolation (PHVFI). Changes in the protocol parameters for the dynamic MRI sequences in breast patients allowed us to be able to acquire more spatial slices, hence the possibility to actually verify the accuracy of the fractal interpolation. The interpolated slices were compared to the imaged slices in the original set. The accuracy of the interpolation was tested on post-hyperthermia treatment data set. The difference between the reconstruction and the original slice varied from 2 to 5%. Significantly, the fractal dimension of the interpolated slices is within 2–3% from the original images, thus preserving the fractality of the perfusion maps. The use of such a method becomes crucial when tumor size and imaging restrictions limits the number of spatial slices, requiring interpolation to fill the data between the slices.
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Marques, Lucas. "A chord distance metric based on the Tonal Pitch Space and a key-finding method for chord annotation sequences." In Simpósio Brasileiro de Computação Musical. Sociedade Brasileira de Computação - SBC, 2019. http://dx.doi.org/10.5753/sbcm.2019.10435.
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Music Information Retrieval (MIR) is a growing field of research concerned about recovering and generating useful information about music in general. One classic problem of MIR is key-finding, which could be described as the activity of finding the most stable tone and mode of a determined musical piece or a fragment of it. This problem, however, is usually modeled for audio as an input, sometimes MIDI, but little attention seems to be given to approaches considering musical notations and musictheory. This paper will present a method of key-finding that has chord annotations as its only input. A new metric is proposed for calculating distances between tonal pitch spaces and chords, which will be later used to create a key-finding method for chord annotations sequences. We achieve a success rate from 77.85% up to 88.75% for the whole database, depending on whether or not and how some parameters of approximation are configured. We argue that musical-theoretical approaches independent of audio could still bring progress to the MIR area and definitely could be used as complementary techniques.
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Majidaie, Saeed, Luky Hendraningrat, and M. Azri Bin Hanifah. "Practical Upscaling Process for Enhanced Water Alternating Gas : A Numerical Investigation." In SPE/IATMI Asia Pacific Oil & Gas Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/205685-ms.
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Abstract Water alternating gas (WAG) is a well-known strategy to improve the mobility issues during gas injection. However, WAG was identified still having some challenges during implementation at oilfield with high reservoir heterogeneity and high permeable zones in the reservoir and will cause unfavorable mobility ratio. Enproperties of the selected core samplehancement of WAG (EWAG) using foam and surfactant has been research to solve its issue and has success stories. This paper will describe the work process of EWAG to be Pilot at Malaysian oilfield, focusing on numerical investigation during upscaling process. Foam treatment has role for gas mobility control, delaying gas breakthrough and diverting gas to unswept zones. Meanwhile, the surfactant was utilized to reduce the IFT between gas and liquid to enable gas dispersion into liquid phase. An in-house foaming surfactant has been developed and used for coreflooding experiment at harsh environment. It was used to generate stable foam in contact with gas and it caused a mobility reduction which was suitable for mobilizing trapped oil and hence improving oil recovery. Coreflood experiment was performed on native core and all experimental results were consolidated and checked for the quality prior model calibration in the reservoir simulator. Once coreflood model was constructed, base case was run using default foam parameters. It aimed initially to test whether the model run smoothly and to observe the matching quality using the default values. Once satisfactory matchings were achieved, the process continued with foam parameters upscaling. During scale-up process the velocity of the fluids and pressure drop were conserved as laboratory data. The important scale-up parameters and the corresponding scale-up ratio were investigated. Mobility Reduction Factor (MRF) was calculated by dividing average DP for each foam cycle with base differential pressure (DP) in the prior gas injection. MRF values for both lower and higher rate show increasing MRF values. Regardless, these values are lower in lower flowrates sequences compared to ones for higher flowrates. This corresponds to MRF values calculated in the laboratory analysis. Therefore, stronger and more stabilized foam were generated using higher injection rates. Lower and higher flowrates had distinctive set of foam parameters. The acceptable matches for differential pressure, oil, water, and gas were achieved. for lower flowrate. Based on this study, model was able to capture production trends depicted in the laboratory analysis. The foam parameter set from higher flowrates have more potential for further upscaling and modeling in full-field scale.
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Brandão, André Iglesias, Luiz Paulo Bastos Vasconcelos, Carolina de Almeida e. Silva, Raul de Barros Valente, Danilo Jorge da Silva, Pedro Ivo Machado Campos de Araujo Costa, Matheus Henrique Freitas Silva, et al. "Brain Ischemia associated with COVID-19 and PFO - Case Report." In XIII Congresso Paulista de Neurologia. Zeppelini Editorial e Comunicação, 2021. http://dx.doi.org/10.5327/1516-3180.287.
Full textAbstract:
Context: COVID19 has better known respiratory impacts than cardiovascular1 and high D-dimer as the most significant coagulation parameter2 . Otherwise, paradoxical embolism due to Patent Foramen Ovale (PFO) and Ischaemic Cerebral Vascular Accident (iCVA) mechanisms associated are poorly documented3, 4 . We aimed to report an associated case of iCVA and PFO and highlight COVID19 hypercoagulability triggering thromboembolisms. Case report: CTT, 76y, female, hypertensive, former-smoker was hospitalized with right-hemiplegia, transcortical aphasia, dysarthria by iCVA and evolved with headache, odynophagia, fever, chills. RT-PCR-SARS-Cov2: positive; chestCT: 25% bilateral pulmonary involvement, ground-glass opacities. 8days later, was transferred to ICU-COVID-HU-UFJF; D-dimer=827. In 30days, went to ward with O2-dependent pulmonary sequelae; CT-angiography excluded Pulmonary Thromboembolism. Searched iCVA mechanism, ECO detected PFO=2.8mm and Interatrial Septum aneurysm. Prescribed anticoagulants. Subsequently, presented right-clonus, further previous RankinScale=5. Requested brain-MRI pointed lobar hemorrhage with mass effect in recent iCVA’s territory (left-Middle Cerebral Artery). After 10days, a head-CT evidenced partial resorption and reduced mass effect. Patient was discharged taking rivaroxabana. Conclusions: Retrospectively, we suspected that COVID19 hypercoagulability triggered Deep Vein Thrombosis and the consequent PFO paradoxical embolism, which caused iCVA. Therefore, vascular pathologies in COVID19 deserve further studies. Treatment for secondary prevention in iCVA by PFO is uncertain3 .
Reports on the topic "MRI sequence parameters"
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Estimation of Vehicle Miles Traveled Based on Improved Ant Colony Algorithm. SAE International, December 2020. http://dx.doi.org/10.4271/2020-01-5195.
Full textAbstract:
Vehicle miles traveled (VMT) statistics is a key parameter which has many applications, such as the assessment of vehicle quality, evaluation of driving behavior and oil consumption, and other applications in vehicle monitoring system. In the earlier studies, the calculation of VMT usually focused on improving the accuracy and frequency of vehicle GPS data, but the VMT estimation error due to them were getting smaller with the development of positioning technology. Nowadays in the practical application of internet of vehicles, errors due to the out-of-order location data which caused by communication mechanism have become increasingly obvious. In this paper, we propose a VMT estimate method based on improved ant colony algorithm and local search method which is suitable for dealing with timestamp chaotic location data sequence. To evaluate our method, we use real-world vehicle data gathered by China mobile’s vehicle fleet management products, the analysis result shows the MRE of proposed ant colony algorithm is usually less than 8%, at least 3 percentage points lower than that of uniform motion distance accumulation statistics, at least 7 percentage points lower than that of Euclid distance accumulation statistics.