Dissertations / Theses on the topic 'PET/SPECT imaging'

Positron emission tomography (PET) and single photon emission tomography (SPECT) are two nuclear emission-imaging modalities that rely on the detection of high-energy photons emitted from radiotracers administered to the subject. The majority of these photons are attenuated (absorbed or scattered) in the body, resulting in count losses or deviations from true detection, which in turn degrades the accuracy of images. In clinical emission tomography, sophisticated correction methods are often required employing additional x-ray CT or radionuclide transmission scans. Having proven their potential in both clinical and research areas, both PET and SPECT are being adapted for small animal imaging. However, despite the growing interest in small animal emission tomography, little scientific information exists about the accuracy of these correction methods on smaller size objects, and what level of correction is required. The purpose of this work is to determine the role of attenuation and scatter corrections as a function of object size through simulations. The simulations were performed using Interactive Data Language (IDL) and a Monte Carlo based package, Geant4 application for emission tomography (GATE). In IDL simulations, PET and SPECT data acquisition were modeled in the presence of attenuation. A mathematical emission and attenuation phantom approximating a thorax slice and slices from real PET/CT data were scaled to 5 different sizes (i.e., human, dog, rabbit, rat and mouse). The simulated emission data collected from these objects were reconstructed. The reconstructed images, with and without attenuation correction, were compared to the ideal (i.e., non-attenuated) reconstruction. Next, using GATE, scatter fraction values (the ratio of the scatter counts to the total counts) of PET and SPECT scanners were measured for various sizes of NEMA (cylindrical phantoms representing small animals and human), MOBY (realistic mouse/rat model) and XCAT (realistic human model) digital phantoms. In addition, PET projection files for different sizes of MOBY phantoms were reconstructed in 6 different conditions including attenuation and scatter corrections. Selected regions were analyzed for these different reconstruction conditions and object sizes. Finally, real mouse data from the real version of the same small animal PET scanner we modeled in our simulations were analyzed for similar reconstruction conditions. Both our IDL and GATE simulations showed that, for small animal PET and SPECT, even the smallest size objects (~2 cm diameter) showed ~15% error when both attenuation and scatter were not corrected. However, a simple attenuation correction using a uniform attenuation map and object boundary obtained from emission data significantly reduces this error (~1% for smallest size and ~6% for largest size, in non-lung regions). In addition, we did not observe any significant improvement between the uses of uniform or actual attenuation map (e.g., only ~0.5% for largest size in PET studies). The scatter correction was not significant for smaller size objects, but became increasingly important for larger sizes objects. These results suggest that for all mouse sizes and most rat sizes, uniform attenuation correction can be performed using emission data only. For smaller sizes up to ~ 4 cm, scatter correction is not required even in lung regions. For larger sizes if accurate quantization needed, additional transmission scan may be required to estimate an accurate attenuation map for both attenuation and scatter corrections.

Uma grande variedade de moléculas já foi identificada por apresentar alta afinidade por receptores superexpressos em células tumorais, e a radiomarcação dessas moléculas oferece a possibilidade de novos compostos com aplicações diagnósticas e terapêuticas em medicina nuclear. Dentre essas moléculas, a bombesina (BBN) é uma das que despertam maior interesse, uma vez que um de seus receptores BB2 são superexpressos em células de tumores de próstata, mama, cólon, pâncreas e pulmão, além de glioblastomas e neuroblastomas. Derivados da bombesina, agonistas e antagonistas dos receptores BB2 já foram propostos para essa finalidade e apresentaram resultados promissores em estudos pré-clínicos. Entretanto, a maioria deles apresenta o incoveniente da alta captação em tecidos sadios, como pâncreas e intestino, o que pode prejudicar a eficiência diagnóstica e causar efeitos adversos na terapia. Nesse contexto, o objetivo deste trabalho foi estudar a marcação de uma nova série de derivados da bombesina com índio-111 (111In) e gálio-68 (68Ga), de modo a avaliar seu potencial para diagnóstico de tumores que superexpressam BB2 por tomografia computadorizada por emissão de fóton único (SPECT) ou por emissão de pósitrons (PET). Os peptídeos estudados apresentam estrutura genérica YGn-BBN(6-14)-Q, em que Q é o grupamento quelante, n é o número de aminoácidos glicina do espaçador YGn e BBN(6-14) é a sequência original de aminoácidos da BBN do aminoácido 6 ao 14. Estudou-se também o derivado em que a metionina (Met) terminal da sequência da bombesina foi substituída pela norleucina (Nle). A avaliação experimental dos derivados da bombesina foi dividida em quatro etapas: estudos computacionais, marcadores moleculares para SPECT, marcadores moleculares para PET e estudos toxicológicos. Os estudos computacionais consistiram na determinação dos coeficientes de partição (log P) e distribuição (log D) teóricos dos derivados da bombesina conjugados ao quelante DTPA (ácido dietileno-triamino-pentacético e DOTA (1,4,7,10-tetraazaciclododecano-tetracético). No desenvolvimento de marcadores moleculares para SPECT os derivados da bombesina de diferentes espaçadores conjugados ao DTPA e radiomarcados com 111In foram avaliados para determinação do melhor espaçador para aplicação in vivo, considerando não apenas as propriedades in vivo, mas também a estabilidade. Uma vez definido o espaçador, o derivado escolhido conjugado ao quelante DTPA ou DOTA foi submetido a estudos comparativos in vitro e in vivo utilizando linhagens tumorais que expressam os receptores BB2 em níveis variados, de modo a determinar o agente quelante mais adequado para aplicação in vivo. Nessa fase experimental, alguns estudos foram realizados também com um derivado da BBN BZH3, amplamente descrito pela literatura. No desenvolvimento de marcadores moleculares para PET, o derivado composto pelo espaçador e quelante escolhido foi radiomarcado com 68Ga e submetido a estudos de biodistribuição in vivo. Por fim, estudos toxicológicos em ratos foram realizados por meio da administração de um excesso dos derivados da BBN, a fim de avaliar a segurança para futura aplicação em estudos clínicos. Todos os derivados conjugados ao DTPA foram radiomarcados com 111In com alta pureza radioquímica e alta atividade específica (174 GBq/μmol). Os marcadores moleculares obtidos apresentaram alta estabilidade frente à reação de marcação e baixa estabilidade à temperatura ambiente, a qual foi aumentada com a adição de agentes estabilizantes. A análise em soro humano indicou degradação tempo-dependente dos marcadores moleculares pelas enzimas do soro e aumento da estabilidade com o acréscimo de aminoácidos glicina no espaçador, bem como pela substituição da Met terminal pela Nle. Os estudos em CLAE e de log P confirmaram os resultados de log P teórico e indicaram que os marcadores moleculares apresentam baixa lipofilicidade, a qual decresce com o aumento do espaçador e aumenta com a substituição do aminoácido terminal. Os estudos in vivo demonstraram que os marcadores moleculares de DTPA-111In apresentam rápido clareamento sanguíneo, excreção primariamente renal e baixo acúmulo abdominal. O marcador molecular que apresentou maior captação tumoral foi aquele com a Nle terminal (YG5N), e esse foi submetido à análise comparativa entre os quelantes bifuncionais DTPA e DOTA. O YG5N-DOTA foi radiomarcado com 111In com alta atividade específica (100 GBq/μmol). Ensaios de saturação em células de tumor de próstata (PC-3 e LNCaP) e mama (T-47D) in vitro demonstraram afinidade semelhante para o peptídeo conjugado a ambos quelantes, mas o YG5N-DOTA-111In se ligou mais às células de tumor de próstata, mas não às células de tumor de mama. Esse marcador molecular também foi mais internalizado pelas células PC-3. Os estudos in vivo indicaram maior estabilidade do marcador molecular conjugado ao DOTA em soro de camundongo, mas captação dos dois peptídeos semelhante pelo tumor de células PC-3 e LNCaP, embora esse último tenha demonstrado uma concentração duas vezes menor do receptor BB2. A imagem SPECT/CT dos tumores foi possível com os dois peptídeos. Em comparação com o derivado BZH3-111In, os marcadores moleculares apresentaram captação tumoral semelhante, mas as imagens foram mais favoráveis devido à menor captação abdominal. O YG5N-DOTA foi então radiomarcado com 68Ga, obtendo-se alta pureza radioquímica, e seu perfil de distribuição foi semelhante ao do derivado radiomarcado com 111In, com significativa captação pelo tumor de células PC-3. Os ensaios de tolerância toxicológica demonstraram que os derivados da bombesina são seguros até a concentração administrada, não apresentando toxicidade hematológica, hepática ou renal. O derivado da BBN YG5N conjugado ao DTPA ou DOTA é uma ferramenta promissora e segura para o diagnóstico de tumores que superexpressam os receptores BB2 por SPECT e PET.
A high number of molecules have already been identified to have high affinity to some receptors overexpressed on tumour cells and the radiolabelling of those molecules offers the possibility of new compounds for tumour diagnosis and therapy by nuclear medicine. Among of those molecules, bombesin (BBN) has become focus of interest, as its BB2 receptors are known to be overexpressed in prostate, breast, colon, pancreatic and lung tumour, as long as glioblastomas and neuroblastomas. BBN agonists and antagonists have already been described for this purpose and promising results were obtained in preclinical studies. However, most of them exhibited high abdominal accumulation, especially in pancreas and intestines, which can compromise diagnosis accuracy and cause serious adverse effects in therapy. In this context, the goal of the present work to radiolabel new BBN derivatives with 111In and 68Ga and to evaluate their potential for BB2 positive tumors diagnosis by single photon emission tomography (SPECT) and positron emission tomography (PET). The structure of studied peptides was Q-YGn-BBN(6-14), where Q is the chelator, n is the number of glycine aminoacids in the spacer YGn and BBN(6-14) is the original bombesin sequence from the aminoacid 6 to 14. The derivative in which the last aminoacid (methionine, Met) was replaced by norleucine (Nle) was also evaluated. The experimental evaluation of the bombesin derivatives was divided into four steps: computational studies, molecular markers for SPECT, molecular markers for PET and toxicological studies. The teorical partition (log P) and distribution (log D) coefficients were calculated for all bombesin derivatives conjugated to DTPA (diethylenetriaminepentaacetic acid) and DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) chelators applying computational programmes. Bombesin derivatives for SPECT were developed by radiolabelling DTPA-conjugated bombesin derivatives with 111In to determine the best spacer for in vivo applications, regarding the stability and in vivo properties. The derivative with the most favorable properties and conjugated to DTPA or DOTA was evaluated in comparative in vitro and in vivo studies in different BB2 expressing tumour cells, in order to determine the best chelator to be used in vivo. Some comparative studies were also performed with the BBN analogue BZH3, which was described by the literature. The molecular marker for PET was developed by radiolabelling the derivative chosen with 68Ga and evaluating the biodistribution profile in healthy and tumour mice. Finally, toxicological studies were performed by injecting an excess of cold bombesin derivatives in rats to determine their safety for clinical querries. All derivatives conjugated to DTPA were radiolabelled with 111In at high radiochemical purity and high specific activity (174 GBq/μmol). The molecular markers presented high stability during radiolabelling and low stability at room temperature and this stability was increased after the addition of stabilizer agents. Stability in human serum analysis suggested time-course degradation by human serum enzymes and the increase on glycine aminoacids in the spacer improved the molecular markers stability, as long as the replacement of terminal Met by Nle. HPLC and log P results confirmed the teorical log P data which showed that the BBN derivatives present low lipophilicity, which decreases with the increase on glycine aminoacids in the spacer and the replacement of terminal Met by Nle. In vivo studies demonstrated that 111In-DTPA-BBN analogues present fast blood clearance, excretion by renal pathway and low abdominal accumulation. Highest tumour uptake was observed with the Nle-terminal derivative (YG5N), which was used for the comparison between the DTPA and DOTA chelators. DOTA-YG5N was also radiolabeled with 111In at high specific activity (100 GBq/μmol), but this was lower than for the DTPA derivatives. Saturation binding assays on prostate (PC-3 e LNCaP) and breast (T-47D) tumour cells showed similar affinity for the radiopeptide conjugated to DTPA and DOTA, higher binding of DOTA-peptide to PC-3 and LNCap cells was observed, but not for T-47D cells. This molecular marker was also more internalized by PC-3 cells. In vivo studies showed higher stability for 111In-DOTA-YG5N in mice serum, and the uptake of DTPA and DOTA peptide was similar by PC-3 and LNCaP tumour, although this last tumour has shown 2-fold less BB2 receptors than PC-3. SPECT/CT imaging of PC-3 and LNCaP was possible with both radiopeptides. When compared to 111In-BZH3, the molecular markers present similar tumour uptake, but with more favorable images, because of their lower abdominal uptake. DOTA-YG5N was radiolabeled with 68Ga with high radiochemical purity and the biodistribution profile was similar to the peptide labeled with 111In, with significative PC-3 tumour uptake. Toxicological studies showed the bombesin derivatives are safe up to concentration administered and did not present hematological, hepatic or renal toxicity. The BBN derivative YG5N conjugated to DTPA or DOTA is a promising and safe tool for BB2 expressing tumour diagnosis by SPECT and PET.

During the course of this PhD, a number of potential PET and SPECT imaging agents were synthesised for particular in vivo targets. The first targets were monocarboxylate transporters 1 and 2 (MCT 1 and 2) which are responsible for the transport of moncarboxylates such as lactate and pyruvate across plasma membranes. The generation of imaging agents which bind to these MCTs could lead to the effective molecular imaging of epileptogenic regions of the brain. A potent and selective inhibitor of MCT 1 and 2 was previously synthesised by AstraZeneca (AR-C155858). In this project, a library of analogues of this compound was synthesised, containing potential sites for radiolabelling. A group of these compounds underwent preliminary biological evaluation to determine the inhibitory effect on lactate uptake against MCT 1, 2 and 4 (the most active being thienopyrimidine 73). The second target was poly(ADP-ribose) polymerase-1 (PARP-1), an enzyme used in the repair of DNA. Targeting PARP-1 with radiotracers could aid the diagnosis and monitoring of various tumours. A small library of potential PET imaging agents, which have the potential to undergo facile radiofluorination, were synthesised based on the PARP-1 inhibitor olaparib. This series of compounds were subject to a PARP-1 immunofluorescence assay and the most potent compound in the series was found to be phthalazinone 147. The second part of this thesis describes the development of novel radioiododeboronation methods using both gold(I) and potassium acetate catalysis. These methods were used in the radiosynthesis of a number of aromatic iodides, giving the radiolabelled products in high radiochemical yields. SPECT imaging agents [125I]MIBG and a PARP-1 tracer were also generated under these conditions.

Positron emission tomography/computed tomography (PET/CT) is a method that quantitatively visualizes physiological processes. The most common indications for PET brain are early diagnosis of various dementia types with 18F-Fludeoxyglucose (18F-FDG). The hospital in Jonkoping installed a new PET/CT and brain examinations have not yet been performed. The aim of the study was to map how hospitals in Sweden performed seven selected brain examinations with PET/CT focusing on modality structure, examination method and reconstruction method, with a comparison of radiation dose between PET/CT and single photon emission computed tomography/CT (SPECT)/CT. Out of the nine university hospitals selected, two were excluded. The method was prospective with quantitative approach and data was collected through a protocol. Compilation was made on Excel and the statistics were processed using the Wilcoxon Signed Ranks Test. The result showed similarities, for example reconstruction method and differences, for example fasting time. Effective dose was higher on SPECT than PET in examination of Parkinson's disease, however no significant difference (p = 0,059) was detected. Higher effective doses on SPECT was due to longer half-lives and greater dosages of Ioflupane (123I-Datscan) than 18F-FDG. For further studies, more hospitals and parameters in the protocol can be included.

The growing understanding of tumor biology and the identification of tumor specificgenetic and molecular alterations, such as the overexpression of human epidermal growthfactor receptor 2 (HER2), opens up for personalization of patient management using targeted therapies. However, this puts stringent demands on the diagnostic tools usedto identify patients that are likely to respond to a particular treatment. Radionuclide molecular imaging is a promising non-invasive method to visualize and characterize the expression of such targets. This thesis, based on five papers, is focused on the development of radiolabeled Affibody molecules for imaging of HER2-expression in malignant tumors. Affibody molecules, which represent a rather novel class of affinity proteins developed by combinatorial protein engineering of the protein A derived Z-domain, display manyfeatures that make them promising tracers for molecular imaging applications. The aim of the work presented here was to further develop the tracer format for improved in vivo properties and flexibility in the choice of radionuclide. In paper I, the development of an assay that enables quantitative studies of the internalization rate and cellular processing of high affinity Affibody molecules is described. The assay was applied to a HER2-binding Affibody variant that was efficiently retained by HER2-expressing cells, although characterized by a slow internalization rate. This may have implications for the choice of label for Affibody molecules since high affinity to the target may be equally, or more, important for good imaging quality than residualizing properties of the radiolabel. In paper II, a HER2-binding Affibody molecule and the monoclonal antibody trastuzumab were labeled with positron emitting 124I, for a head-to-head in vivocomparison of the two tracer formats. The effects of tracer size and presence of an Fc region on the biodistribution profile were investigated. In paper III, a HER2-binding Affibody molecule was site-specifically labeled with radiocobalt and evaluated in vitro and in vivo.A head-to-head in vivo comparison with the well-studied 111In-labeled counterpart was performed, revealing promising potential for the cobalt-labeled molecule as a PET-tracerfor visualization of HER2. Paper IV describes the in vitro and in vivo evaluation of a panel of Affibody molecules with different C-terminal peptide-based chelators for the coordination of 99mTc. Even small changes in the C-terminal sequence had appreciable impact on the biodistribution of the Affibody molecules and by optimizing the design of the chelator, the kidney uptake of 99mTc could be significantly reduced. Finally, in paper V we describe the development of a HER2-targeting Affibody variant equipped with a Sel-tag for site-specific labeling with the short-lived positron emitter 11C. This novel Affibody tracer could be used to image HER2-expressing tumors in vivo within one hour after injection. Taken together, Affibody molecules show great promise as targeting tracers for radionuclide molecular imaging of HER2. Careful design and optimization of the tracer protein is important and can be used to improve the biodistribution and targeting properties of Affibody molecules.
QC 20110922

A baixa seletividade dos métodos convencionais para diagnóstico e terapia de neoplasias, bem como o fato de nem sempre alcançarem o sucesso terapêutico desejado, configuram dificuldades para a prática oncológica. Diante disso, os anticorpos monoclonais (AcMs) radiomarcados, aplicados em técnicas diagnósticas, têm se destacado, visto que permitem a entrega seletiva da radiação ao alvo de interesse. A metodologia Radioimunodiagnóstico (RID), utilizando AcM anti-EGFR radiomarcado, possibilita triagem prévia, avaliando a resistência ao tratamento e estratificando pacientes que possam apresentar benefícios à imunoterapia com cetuximabe. Além disso, permite monitorar a progressão da terapia, visando tratamento mais efetivo e direcionado, promulgando a abordagem da medicina personalizada. No Brasil, ainda não há radioimunoconjugado disponível para diagnóstico e seguimento do câncer. Nesse contexto, o objetivo com este trabalho foi o de desenvolver uma formulação farmacêutica para padronizar uma rotina de produção dos radiofármacos para radioimunodiagnóstico de câncer de cabeça e pescoço e de câncer colorretal: cetuximabe-DTPA-111In e cetuximabe-DFO-89Zr. Em adição, corroborar na elucidação dos mecanismos de resistência das células tumorais à terapia com o cetuximabe, através da realização de estudos de ligação do radioimunoconjugado à receptores celulares. Em relação aos radiofármacos estudados, destaca-se que os processos de conjugação do cetuximabe com os quelantes DTPA, na razão molar 1:20, e com o DFO, 1:5, foram bem-sucedidos e otimizados, demonstrando boa reprodutibilidade. Os imunoconjugados apresentaram preservação da imunorreatividade e alta estabilidade quando armazenados a -20°C por até seis meses. Esses imunoconjugados, quando radiomarcado com 111In e 89Zr, exibiram pureza radioquímica superior a 95%, sem necessidade de purificação pós-marcação, e estabilidade por tempo que possibilita seu transporte às clínicas distantes do centro produtor. As análises in vitro do cetuximabe-DTPA-111In em células FaDu-C10 (linhagem resistente) demonstraram percentual inexpressivo de ligação e internalização do radioimunoconjugado, congruindo na explanação do modelo de resistência conferido à linhagem. O estudo de corpo inteiro em MicroPET/TC revelou redução no perfil de captação no grupo de bloqueio, com excesso de cetuximabe não marcado, e intensa captação do cetuximabe-DFO-89Zr pelo tumor de células escamosas no grupo sem bloqueador, confirmando a especificidade in vivo do radioimunoconjugado. Os estudos de biodistribuição dos radiofármacos foram compatíveis com os descritos em literatura e validaram os resultados obtidos por imagens em MicroSPECT/TC e MicroPET/TC, além de apresentarem apreciável captação tumoral, considerando os tempos analisados. A estabilidade alta in vivo e a eficácia da marcação foram confirmadas pela baixa captação óssea e em tecidos não alvos. O melhor intervalo pós-injeção do radiofármaco para avaliação in vivo foi após cinco dias da administração. Conclui-se, portanto, que os radioimunoconjugados para imuno-SPECT e imuno-PET, cetuximabe-DTPA-111In e cetuximabe-DFO-89Zr, são ferramentas promissoras para diagnóstico e monitoramento de câncer receptor específico (EGFR) e para estratificação de pacientes à terapia anti-EGFR, encorajando a continuidade deste projeto para futuros estudos clínicos.
The low selectivity of conventional methods for cancer diagnosis and therapy, as well as the fact that these methods could not achieve the desired therapeutic success, constitute difficulties for the oncological practice. In this regard, radiolabeled monoclonal antibodies (mAbs) applied in diagnostic techniques have been highlighted, since they allow the selective delivery of the radiation to the specific target. The radioimmunodiagnosis methodology (RID), using radiolabeled anti-EGFR mAbs, enables previous screening, evaluating resistance to treatment and stratifying patients who may present benefits to cetuximab immunotherapy. In addition, it allows monitoring the progression of the therapy, aiming for a more effective and directed treatment, leading the personalized medicine approach. A radioimmunoconjugate is not yet available for diagnosis and management of cancer in Brazil. In this context, this research was carried out to develop a pharmaceutical formulation to standardize a routine production of radiopharmaceuticals for diagnosis and monitoring head and neck cancer and colorectal carcinoma: 111In-DTPA-cetuximab and 89Zr-DFO-cetuximab. In addition, corroborate in the elucidation of the tumor cells resistance mechanisms to EGFR-targeted therapy, through in vitro and in vivo radioimmunoconjugate binding studies to cellular receptors. Regarding to the radiopharmaceuticals studied, cetuximab was conjugated to DTPA chelator at 1:20 molar ratio and to DFO at 1: 5, and these processes were successful and optimized, showing good reproducibility. Immunoconjugates showed preservation of immunoreactivity and high stability when stored at -20 °C for up to 6 months. These immunoconjugates when radiolabeled with 111In and 89Zr have exhibited radiochemical purity above 95%, without any post-labeling purification, and the radioimmunoconjugates have demonstrated stability for a time that allows them to be transported to clinics far from the producer center. 111In-DTPA-cetuximab in vitro analyzes in FaDu-C10 cells (resistant cell line) has presented an inexpressive percentage of binding and internalization of the radioimmunoconjugate, ensuring the resistance model conferred to this cell line. The MicroPET/CT imaging study has revealed a reduction in uptake profile for \"Blocking\" group, with an excess of unlabeling cetuximab, and an intense 89Zr-DFO-cetuximab uptake in squamous cell tumor for \"Non-blocking\" group, that evidenced the in vivo radioimmunoconjugate specificity. The biodistribution studies of the radiopharmaceuticals were well-matched with those described in the literature and they validated the results obtained through the MicroSPECT/CT and MicroPET/ CT images. In addition, these studies in vivo have displayed a substantial tumor uptake, according with the analyzed time points. The radioimmunoconjugate showed high in vivo stability and labeling procedures efficiency, which were confirmed by low bone and non-target tissues uptake. The best post-injection interval for in vivo evaluation is after 5 days of radioimmunoconjugate administration. In conclusion, the radioimmunoconjugates for immuno-SPECT and immuno-PET, 111In-DTPA-cetuximab and 89Zr-DFO-cetuximab, are promising tools for diagnosis and monitoring of specific receptor cancer (EGFR), as well as for stratification of patients to anti-EGFR therapy, and thus encourages the continuity of this project for future clinical trials.

Introduction: The HER2 receptor overexpression is normally associated to aggressive and infiltrating breast cancer (BC) phenotype with propensity to spread into metastases. Nowadays, the detection of HER2 in primary tumor lesions and in their metastases is based on invasive methods as well therapy clinical outcomes are not satisfactory yet. Recent advances in nanotechnology have led to the development of nanoparticles able to host various functionalities for specific targeting and to be loaded with therapeutic molecules, making possible the simultaneous diagnosis and treatment of human cancers (theranostic). In the present Thesis study, was evaluated the potential use of targeted silica nanoparticles (SiNPs) as theranostic agent for HER2+ breast cancer. Methods: SiNPs were engineered with anti-HER2 monoclonal antibody Trastuzumab, in the form of half-chain (Hc-TZ), and radiolabeled employing 99mTc for in vivo SPECT imaging detection of HER2+ BC lesions. Subsequently, SiNPs were loaded with doxorubicin (DOX) for treatment evaluation. Experimental design was divided in three main tasks. First, we evaluated the contribution offered by active targeting (Hc-TZ) to the selective distribution of SiNPs in solid HER2 positive BC lesions. To this aim, both Hc-TZ conjugated (SiNP-TZ) and non-conjugated (SiNP) nanosilica shells were radiolabeled with 99mTc-Tricarbonyl complex, through nitrilotriacetic acid (NTA) linker procedure, and their distribution kinetics evaluated in vitro and ex vivo in ad hoc cancer models. Nanoparticles were simultaneous filled with a fluorescent dye and their uptake were also assessed by FACS analysis and fluorescence microscopy. In the second experimental step, nanoparticles were also engineered with several amount of Hc-TZ (SiNPs to Hc-TZ ratio, 1:2 and 1:8 respectively), and were 99mTc-labeled at histidine residues of the antibody chain for ex vivo/in vivo biodistribution evaluation. Finally, SiNP-TZ were loaded with DOX and in vitro/in vivo DOX distribution in HER2 positive models was evaluated using confocal microscopy and Optical Imaging, in comparison to liposomal doxorubicin (Caelyx). The treatment efficacy of DOX-SiNP-TZ (1:8 Hc-TZ) versus Caelyx was evaluated in vivo for six weeks of treatment, also using PET molecular imaging ([18F]FDG) approach. Results: In vitro assays showed a higher fluorescence signal (FICT) in SK-BR-3 compared to MDA-MB-468 cells, exclusively for targeted SiNP-NTA-TZ/SiNP-TZ with an increase over time. Ex vivo biodistribution of 99mTc-labelled nanoparticles via NTA, at 4 h post-injection of SiNP-NTA-TZ and/or non-targeted (SiNP-NTA), exhibited values of 3.53 and 1.69 in tumor (tumor to muscle ratio) respectively, with a rapid reduction over time for targeted nanoparticles. These results indicated the presence of an antibody-receptor mediated tumor uptake of SiNP-NTA-TZ, with a faster washout of nanoparticles radiolabeled shell. In the second set of experiments, performed with 99mTc-SiNP-TZ labelled on TZ half chain, uptake was confirmed at 4 h p.i. for SiNP-TZ (1:8 Hc-TZ) with similar results to SiNP-TZ (1:2 Hc-TZ). Instead, was showed a progressive retention of radioactivity until 24 h p.i., confirming the presence of radiolabeled Hc-TZ to the tumor also at latter times, with improved results for SiNP-TZ (1:8 Hc-TZ), also in terms of radiochemical yield. Doxorubicin loaded SiNP-TZ (1:8 Hc-TZ) showed in vivo similar delivery results in comparison to Caelyx at 6 h p.i., meanwhile at the end of treatment tumor volume reduction resulted significant improved by targeted nanoparticles administration. Conclusion: Results of this Thesis study, demonstrated a promising specificity and treatment efficacy of the silica nanoparticles-based system SiNP-TZ, encouraging its potential use as theranostic agent for HER2+ breast cancer lesions.

Affibody molecules have lately shown great potential as tools for in vivo molecular imaging. These small, 3-helical bundles, with their highly stable protein scaffold, are well suited for the often harsh conditions of radiolabeling. Their small size allows for rapid clearance from the blood circulation which permits the collection of images already within hours after injection. This thesis includes four papers aimed at engineering different variants of a HER2-binding Affibody molecule to enable effective  and  flexible  radiolabeling  and  enhancing  the  molecular  imaging  in  terms  of  imaging contrast and resolution. In paper I an Affibody molecule was engineered to function as a multifunctional platform for site-specific labeling with different nuclides for radionuclide imaging. This was done using only natural amino  acids,  thereby  allowing  for  both  synthetic  and  recombinant  production.  By  grafting  the amino acid sequence -GSECG to the C-terminal of our model-protein, a HER2-binding Affibody molecule, we enabled site specific labeling with both trivalent radiometals and with  99m Tc. Maleim-ide-DOTA was conjugated to the cysteine residue for labeling with  111 In, while the peptide sequence was able to chelate  99m Tc directly. This approach can also be used for site-specific labeling with other probes available for thiol-chemistry, and is applicable also to other protein scaffolds. In paper II we investigated the impact of size and affinity of radiolabeled Affibody molecules on tumor targeting and image contrast. Two HER2-targeting Affibody molecules, a two-helix (~5 kDa) and a three-helix (~7 kDa) counterpart, were synthetically produced, labeled with  111 In via chelation by  DOTA  and  directly  compared  in  terms  of  biodistribution  and  targeting  properties.  Results showed  that  the  smaller  variant  can  provide  higher  contrast  images,  at  the  cost  of  lower  tumor uptake,  in  high-expressing  HER2-tumors.  However,  neither  the  tumor  uptake  nor  the  contrast of the two-helix variant is sufficient to compete with the three-helix molecule in tumors with low expression of HER2. In paper III and IV we were aiming to find methods to improve the labeling of Affibody molecules with  18 F for PET imaging. Current methods are either complex, time-consuming or generate heavily lipophilic conjugates. This results in low yields of radiolabeled tracer, low specific activity left for imaging, undesirable biodistribution or a combination thereof. In paper III we demonstrate a swift and efficient 2-step, 1-pot method for labeling HER2-binding Affibody molecules by the formation of aluminum  18 F-fluoride (Al 18 F) and its chelation by NOTA, all in 30 min. The results show that the  18 F-NOTA-approach is a very promising method of labeling Affibody molecules with  18 F and further investigation of this scheme is highly motivated. In the last paper we pursued the possibility of decreasing the high kidney retention that is common among small radiotracers with residual-izing radiometabolites. In this work  18 F-4-fluorobenzaldehyde (FBA) was conjugated to a synthetic HER2-targeting Affibody molecule via oxime ligation. However, to avoid elevated liver retention, as seen in previous studies with this kind of label, a hydrophilic triglutamyl spacer between the aminooxy moiety and the N-terminal was introduced. A comparison of the two constructs (with and without the triglutamyl spacer) showed a clear reduction of retention in both kidney and liver in NMRI mice at 2 h p.i. when the spacer was included. In the light of these promising results, further studies including tumor-bearing mice, are in preparation.

QC 20130203

Ce travail de thèse réalisé à l'Institut de Chimie Moléculaire de l'Université de Bourgogne porte dans un premier temps sur la synthèse d'agents chélatants bifonctionnels adaptés à la chélation de radiométaux trivalents, notamment l'indium-111. La plus grande partie de ce travail a ensuite consisté à réaliser le greffage d'un agent chélatant bifonctionnel dérivé du DOTA sur différents anticorps ou fragments d'anticorps monoclonaux : le trastuzumab (anti HER2, traitement de cancers du sein), le cétuximab (anti EGFR, traitement de nombreux cancers, dont le cancer colorectal) et l'abciximab (antiagrégant plaquettaire). Une attention particulière a été apportée à la caractérisation des différents immunoconjugués. La dernière étape de ce travail de thèse porte sur le radiomarquage à l'indium-111 de deux immunoconjugués préparés : le trastuzumab et le cétuximab. Ces étapes de radiomarquage nous ont permis de déterminer la fraction immunoréactive et l'affinité de chaque radiotraceur. Nous avons ainsi pu étudier la biodistribution in vivo de ces radiotraceurs chez la souris par imagerie SPECT-CT. Nous avons également développé une méthode de greffage originale pour le marquage d'un fragment d'anticorps de type Fab, l'abciximab, dans le but de suivre la biodistribution de cet antiagrégant plaquettaire. Enfin, nous avons également validé le concept d'imagerie multimodale à travers le greffage et le radiomarquage d'un agent bimodal pour l'imagerie optique et la SPECT sur des lipopolysaccharides bactériens. Les travaux réalisés nous ont permis d'acquérir un savoir faire en matière de greffage d'anticorps et de radiomarquage. Les résultats obtenus permettent d'envisager le greffage d'autres anticorps ou biomolécules, ainsi que l'utilisation d'autres radionucléides pour l'imagerie PET ou la radioimmunothérapie

Radionuclide molecular imaging is an emerging multidisciplinary technique that is used in modern medicine to visualise diseases at cellular and molecular levels. This thesis is based on five papers (I-V) and focuses on the development of site-specific radiolabelled recombinant anti-HER2 Affibody molecules and preclinical evaluations in vitro and in vivo of the labelled conjugates. This work is part of a preclinical development of an Affibody molecule-based tracer for molecular imaging of HER2 expressing tumours. Papers I and II report the evaluation of the Affibody molecule ZHER2:2395-C, site-specifically labelled with the radiometals 111In (for SPECT) and 57Co (as a surrogate for 55Co, suitable for PET applications) using a thiol reactive DOTA derivative as a chelator. Both conjugates demonstrated very suitable biodistribution properties, enabling high contrast imaging just a few hours after injection. Papers III and IV report the development and optimization of a technique for site-specific labelling of ZHER2:2395-C with 99mTc using an N3S chelating peptide sequence. 99mTc-ZHER2:2395-C demonstrated high and specific tumour uptake and rapid clearance of non-bound tracer from the blood, resulting in high tumour-to-non-tumour ratios shortly after injection, enabling high contrast imaging. In addition, in the study described in paper IV, freeze-dried kits previously developed for 99mTc-labelling were optimised, resulting in the development of a kit in which all the reagents and protein needed for labelling of ZHER2:2395-C with 99mTc were contained in a single vial. Paper V reports the evaluation of an anti-HER2 Affibody molecule, ABY-025, with a fundamentally re-engineered scaffold. Despite the profound re-engineering, the biodistribution pattern of 111In-ABY-025 was very similar to that of two variants of the parental molecule. It seems reasonable to believe that these results will also be applicable to Affibody molecules towards other targets. Hopefully, this work will also be helpful in the development of other small proteinaceous tracers.

L’imagerie préclinique se pratique majoritairement sur des modèles animaux murins principalement des souris (61%), elle représente une étape indispensable en recherche préclinique car elle suit les deux premières recommandations de la règle des 3R (réduction, raffinement et remplacement). Pour donner une signification biologique aux mesures extraites des images acquises in vivo chez la souris, il est nécessaire d’évaluer les performances des instruments utilisés mais également des procédures expérimentales en jeu. La qualification des appareils nécessite l’usage de fantômes spécifiques, et l’évaluation des méthodes impose de tester les procédures sur des individus non pathologiques, avant le passage aux expérimentations proprement dites. L’objectif de ce travail a été de développer des outils et des méthodes permettant de qualifier les instruments d’imagerie et certaines procédures in vivo. La nécessité de quantification, à partir d’images réalisées chez le petit animal, nous amène à considérer les instruments d’imagerie préclinique comme des outils métrologiques ; ce qui amène à intégrer le principe d’incertitude de mesure dans l’expression des résultats
Preclinical imaging is mostly performed on mouse animal models (61%). It is a necessary step in preclinical research, in compliance the first two recommendations of the 3Rs rules (reduction, refinement and replacement). In order to give a biological significance to measurements extracted from in vivo-acquired mouse images, it is necessary to evaluate instruments performances but also experimental procedures involved. The qualification of apparatuses requires the use of specific phantoms while the evaluation of methods requires procedures tests on non-pathological animals before experimentations. The scope of this work was to develop tools and methods to qualify imaging instruments and in vivo procedures. The need for quantification in small animal imaging, leads us to consider preclinical imaging instruments as metrological tools; which means integrating measurement uncertainty into

Graphics processing units (GPUs) are used today in a wide range of applications, mainly because they can dramatically accelerate parallel computing, are affordable and energy efficient. In the field of medical imaging, GPUs are in some cases crucial for enabling practical use of computationally demanding algorithms. This review presents the past and present work on GPU accelerated medical image processing, and is meant to serve as an overview and introduction to existing GPU implementations. The review covers GPU acceleration of basic image processing operations (filtering, interpolation, histogram estimation and distance transforms), the most commonly used algorithms in medical imaging (image registration, image segmentation and image denoising) and algorithms that are specific to individual modalities (CT, PET, SPECT, MRI, fMRI, DTI, ultrasound, optical imaging and microscopy). The review ends by highlighting some future possibilities and challenges.

A tomografia por emissão de pósitrons (\"Positron Emission Tomography\" - PET) é uma técnica para obtenção de imagens tomográficas em Medicina Nuclear que permite o estudo da função e do metabolismo do corpo humano em diversos problemas clínicos, através do uso de fármacos marcados por radionuclídeos emissores de pósitrons. As aplicações mais frequentes ocorrem em oncologia, neurologia e cardiologia, através da análise qualitativa e quantitativa dessas imagens. Atualmente, a PET é realizada de duas maneiras: através de sistemas constituídos por anéis formados por alguns milhares de detectores operando em coincidência, chamados de sistemas dedicados; ou com o uso de câmaras PET /SPECT, formadas por dois detectores de cintilação em coincidência, que também servem para estudos com radionuclídeos emissores de fóton único (\"Single Photon Emission Computed Tomography\" - SPECT). O desenvolvimento desses sistemas PET /SPECT tornou viáveis os estudos com a fluor-deoxiglicose, [18 ANTPOT. F]-FDG, um fármaco marcado com 18 ANTIPOT. F (emissor de pósitrons com 109 minutos de meia-vida física), para um número grande de clínicas e hospitais, principalmente por estes serem de uma tecnologia economicamente mais acessível que os realizados com a PET dedicada. Neste presente trabalho, desenvolveu-se uma metodologia para caracterizar e avaliar um sistema PET /SPECT com dois detectores de cintilação e dispositivo com duas fontes pontuais de Cs-137, destinado à obtenção das imagens de transmissão para a correção de atenuação dos fótons. Ela se baseia em adaptações dos testes convencionais de câmaras SPECT, descritos no IAEA TecDoc - 602 - 1991 (\"lnternational Atomic Energy Agency\" - IAEA), e de sistemas PET dedicados, publicados no NEMA NU 2- 1994 (\"National Electrical Manufacturers Association\"NEMA). O resultado foi organizado em forma de roteiros que foram testados em uma câmara da ADAC Laboratories/Philips, a VertexlM - Plus EPIClMJMCDlM - AC, instalada no Serviço de Radioisótopos do lnCor - HCFMUSP (Instituto do Coração - Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo). Esta câmara foi a primeira instalada no Brasil e está sendo utilizada, predominantemente, para estudos oncológicos e de viabilidade miocárdica. O radiofármaco utilizado na obtenção das imagens foi a [18F]-FDG, fornecida regularmente pelo IPEN/CNEN-SP (Instituto de Pesquisas Energéticas e Nucleares/Comissão Nacional de Energia Nuclear - São Paulo), e a reconstrução tomográfica foi realizada com o software próprio do sistema, utilizando-se os parâmetros padrão dos protocolos clínicos. Foram utilizadas fontes pontuais suspensas no ar para as medidas de resolução espacial transversal e lineares imersas na água para as de fração de espalhamento e sensibilidade. Na avaliação da sensibilidade, uniformidade, taxa de eventos verdadeiros, taxa de eventos aleatórios e tempo morto do sistema eletrônico, foram feitas imagens de um simulador físico construído especialmente para o presente trabalho, a partir das instruções da publicação NEMA NU 2 - 1994 para sistemas PET dedicados. A acurácia da correção de atenuação foi verificada através das imagens do simulador físico citado com a inserção de três cilindros de densidades diferentes: água, ar e Teflon. Os roteiros deste trabalho poderão servir de guia para Programas de Controle e Garantia de Qualidade e avaliação da performance de sistemas PET /SPECT com dois detectores de cintilação em coincidência. A implantação destes roteiros pelos centros clínicos que utilizam este tipo de equipamento aumentará a qualidade e a confiabilidade nas imagens resultantes, assim como na sua quantificação.
Positron emission tomography, PET, is a Nuclear Medicine technique that allows the study of human body\'s function and metabolism in many clinical problems, with the help of pharmaceuticals labeled with positron emitters. The most frequent applications occur in oncology, neurology and cardiology, through qualitative and quantitative analysis of these images. Currently, PET is performed in two manners: by using dedicated systems, consisted of rings of thousands of detectors operating in coincidence; or with the use of PET /SPECT cameras, formed by two scintillation detectors in coincidence, which are also used in SPECT studies (single photon emission tomography). The development of PET /SPECT systems made possible the studies with fluor-deoxiglucose, [18F]-FDG, a pharmaceutical labeled with 18F (positron emitter with 109 minutes physical half-life), for a large number of clinics and hospitals, mainly due to their economical accessibility when compared to the dedicated PET studies. In this present work, a method was developed for characterizing and evaluating a PET /SPECT system with two scintillation detectors and device with two point sources of 137Cs, designed to obtain the transmission images for the photon attenuation correction. lt is based on adaptations of the conventional tests of SPECT cameras, described in IAEA TecDoc - 602 - 1991 (\"international Atomic Energy Agency \" - IAEA), and those for dedicated PET systems, published in NEMA NU 2 - 1994 (\"National Electrical Manufacturers Association \" - NEMA). The results were organized in a set of testing protocols and tested in the ADAC Laboratories/Philips camera, the VertexlM - Plus EPIClM/MCDlM - AC, installed in the Radioisotopes Service of lnCor - HCFMUSP (Instituto do Coração - Hospital das clínicas da Faculdade de Medicina da Universidade de São Paulo). This camera was the first one installed in Brazil and is being used, predominantly, for oncological studies and miocardial viability. The radiopharmaceutical used was [18F]-FDG, supplied regularly by IPEN/CNEN-SP (Instituto de Pesquisas Energéticas e Nucleares I Comissão Nacional de Energia Nuclear - São Paulo), and the tomographic reconstruction was performed with the system software, using the standard parameters of the clinical protocols. Point sources suspended in air were used in the measurements of spatial resolution and linear sources immersed in water for scattering fraction and sensitivity measurements. In the evaluation of sensitivity, uniformity, true events, random events and dead time of the electronic system, a phantom was constructed specifically for the present work, from the instructions of NEMA NU 2 - 1994 for dedicated PET systems. The accuracy of the attenuation correction was verified from the images of the phantom with three inserts of different densities: water, air and Teflon. The resultant protocols can serve as a guideline for Programs of Quality Control and Assurance, as well as for the evaluation of the performance of PET /SPECT systems with two scintillation detectors in coincidence. lf implemented by clinical centers that use this type of equipment, it will enhance the quality and confidence of the resulting images, as well as their quantification.

Les accidents vasculaires cérébraux (AVC) représentent l’une des premières causes de morbi-mortalité dans les pays industrialisés et sont en constante augmentation. Pour l’heure, aucune autre thérapie que la thrombolyse intraveineuse n’est validée, or moins de 10% des patients y sont éligibles.Les premiers essais de thérapie régénérative par greffe de progéniteurs endothéliaux ont montré leur efficacité au niveau préclinique sur la récupération fonctionnelle, mais très peu de cellules parviennent jusqu’au site de la lésion pour y exercer leurs effets. De précédents travaux ont montré que l’érythropoïétine (EPO) augmentait la mobilisation et la prolifération de progéniteurs endothéliaux depuis la moelle osseuse, ainsi que leur adressage vers les sites ischémiés in vivo.Nous avons formulé l’hypothèse que l’EPO pouvait permettre aux progéniteurs endothéliaux vrais (ECFCs) d’atteindre le site ischémié en plus grand nombre pour y exercer un effet plus important, plus rapidement. Nous avons donc décidé d’évaluer trois stratégies d’optimisation : coadministration d’ECFCs et d’EPO, administration d’ECFCs prétraités à l’EPO, et enfin coadministration d’ECFCs et d’un dérivé de l’EPO dénué d’effet hématopoïétique. Pour nos derniers travaux, nous nous sommes aidés de l’imagerie isotopique µSPECT/CT pour quantifier l’adressage au niveau de la lésion des ECFCs avec ou sans optimisation pharmacologique à l’EPO, et évaluer longitudinalement leurs effets bénéfiques sur la rupture de la barrière hémato-encéphalique, l’apoptose cérébrale et le débit sanguin cérébral résiduel, en complément des techniques référentes et de l’évaluation clinique neurofonctionnelle
Stroke represents a leading cause of morbidity and mortality in industrialized countries and prevalence steadily increases. For now, no other therapy that intravenous thrombolysis is validated, still, less than 10% of patients are eligible.The first preclinical regenerative therapy trials using endothelial progenitor cells engraftment gave evidence of their efficacy on functional recovery, although very few cells reached the site of injury to exert their effects are. Previous works showed that erythropoietin (EPO) increased mobilization and proliferation of endothelial progenitor cells from bone marrow, as well as their homing to the ischemic sites in vivo.We hypothesized that EPO could enable true endothelial progenitor cells (ECFCs) to reach the ischemic site in larger quantity, faster, to exercise a greater effect. We decided to evaluate three optimization strategies: coadministration of ECFCs and EPO, administration of EPO-pretreated ECFCs, and finally coadministration of ECFCs and an EPO derivative devoid of hematopoietic effect.In this work, we used μSPECT/CT imaging to quantify the ECFCs homing to the ischemic site with or without EPO optimization after cerebral ischemia, and longitudinally assessed their beneficial effects on blood-brain barrier disruption, cerebral apoptosis and residual cerebral blood flow, complementary to the referent techniques and neurofunctional clinical evaluation

碩士
國立清華大學
生醫工程與環境科學系
102
Abstract Nuclear medicine image can achieve the ultra-high resolution level through the design of detector and pinhole collimator. According to desired resolution and center field of view (CFOV), micro-SPECT is supplied with a lot of specification of collimators. Although adequate collimator allows micro-SPECT fully demonstrated its performance, it often needs high cost. On the other hand, dual tracer imaging with SPECT/PET imaging has active developed in recent years. The procedure is to inject dual tracer (ex: 99mTc and 18F) in body and perform SPECT and PET imaging simultaneously. The process is called “Dual Isotope Simultaneous Acquisition, DISA”. DISA has great advantage in both pre-clinical and clinical applications, it can evaluate the functional imaging of different tracers under identical condition, increase physiological assessment accuracy and reduce errors of separate scans. However, DISA would produce cross-talk scatter contamination to degrade the image quality. As a result, a robust cross-talk scatter correction is essential for classical DISA imaging with SPECT/PET. This study propose a novel Beam Stopper (BS) imaging technique based on PET scanner that enables SPECT/PET dual modality imaging. Instead of the insert of pinhole collimator inside SPECT, the BS insert inside PET scanner can achieve SPECT and PET imaging without the contamination of cross-talk scatter. BS device can be regarded as the opposite of pinhole collimator system, it uses high attenuated material to replace the part of pinhole aperture and remove the other part of pinhole collimator. Using the difference between complete projection data (scan w/o BS) and the BS-scanning projection data, we can obtain a projection data similar to the pinhole imaging. This BS device consisted of four tungsten BS rod with 0.8 mm diameter and forty one discs septa with 0.5-mm-thickness. BS device inserted into Inveon preclinical PET system can acquired full SPECT projection data sets via rotations of BS device, while obtaining PET images with normal PET acquisitions. The feasibility of the study is validated with extensive Monte Carlo simulations. The experiment is divided into two steps. In the first step, we evaluate the performance of BS-SPECT system. Next, we put the BS device inside Inveon preclinical PET to assess the feasibility of dual tracer imaging using BS technique. For BS-SPECT studies, high resolution (~1.2mm), uniformity (CV=6.49%) and 152.85 cps/Bq∙cm2 of volume sensitivity were obtained. For contrast phantom studies, CRC in hot area and cold area can achieve 94.90% and 90.35%, respectively. For DISA studies, the cross-talk scatters can be removed naturally during the subtraction of the sinograms with and w/o BS. SPECT/PET dual modality imaging can maintain the same image quality compared with single modality scan. This study has proposed a novel beam stopper imaging technique that opens the new way for high resolution molecular imaging. Comparing to other micro SPECT, BS has the advantages of low cost and more flexibility and enable the SPECT/PET dual modality imaging while eliminating the cross-talk scatter contaminations.

碩士
國立清華大學
生醫工程與環境科學系
103
The capability of SPECT imaging developed on an preclinical PET scanner can provide a combined PET/SPECT dual modality imaging environment, potentially opening the opportunity for many new clinical and preclinical applications, However, an obstacle to the implementation of the protocol is the interference of signal between two isotope, particularly in the down-scatter from high energy gamma-ray into low energy window. In this work, we developed a new down-scatter correction method for simultaneous dual isotopes PET/SPECT imaging. A Siemens Inveon preclinical PET with a slit-slat collimator insert was modeled using the GATE/MPHG Monte Carlo simulation software developed by our laboratory. For dual imaging capability, dual energy window settings at 120-160 keV and 350-650keV were used to acquired SPECT and PET imaging, respectively. The procedure of the proposed method includes two steps: (1) A 18F uniform phantom needs to be acquired for establishing a transform function and a scaling factor between the two energy windows beforehand. (2) During dual isotopes simultaneous acquisition (DISA), the down-scatter distribution can be estimated by multiplying the acquired projections at 350-650keV with the transform function, and then the absolute scatter amount can be finally obtained by scaling the resulting scatter distribution using the scaling factor. Various phantoms were conducted to compare the image quality using the proposed method and triple energy window method, which is common used for scatter correction in DISA. The results indicated that image generated by our method is close to pure 99mTc isotope imaging, and the proposed method always outperforms the conventional triple energy window (TEW) method in terms of coefficient of variation (15.08% vs. 21.04%) and contrast recovery coefficient (0.848 vs. 0.58). In conclusion, we have developed a novel down-scatter correction method for DISA imaging. It is expected that the method can also be applied to dual isotopes SPECT imaging with high energy peaks that down-scattered to low photopeak data, such as Tc-99m/Tl-201

碩士
長庚大學
醫學影像暨放射科學系
98
18F-AV-133 is a novel PET tracer for imaging the vesicular monoamine transporter 2 (VMAT2) in dopaminergic neuron degeneration of Parkinson diseases (PD) and is expected with more diagnosis power as compared to conventional SPECT tracer for DAT（dopamine transporter, DAT） imaging including 99mTc-TRODAT. Before the wide application in clinical trials, the optimization of scanning protocol and data quantitation for 18F-AV-133 is necessary to guarantee optimal diagnosis power in differentiation of PD from normal controls. This thesis is aimed to study the optimal scanning time, as well as compare the diagnosis power with that of 99mTc-TRODAT. The study included 4 normal controls (NCs) and 9 Parkinson diseases patients. The imaging time window was optimized by using a simple semi-quantitative SUVR (standardized uptake value ratio) and its correlation to a quantitative analysis from DVR (distribution volume ratio), as well as discriminating capability of PD from NCs. After ideal time window was obtained, 18F-AV-133 PET images were correlated with clinical data, and compare to 99mTc-TRODAT SPECT images in same subjects. As the results indicated, at 90-100 min time window, SUVRs were strongly correlated with DVR, and showed good differentiation between NCs and PD patients. Therefore, 90-100 min was considered as the optimal time window. 18F-AV-133 imaging showed better discrimination between NCs and PD patients, and better correlation with clinical characteristics than 99mTc-TRODAT imaging. In these regards, 18F-AV-133 PET is promising for clinical use of detecting monoaminergic terminal reduction in PD patients.

PhD Thesis in Sciences Specialization in Chemistry
The work developed aimed at the design, synthesis and characterization of new Gd(III) and Ga(III) chelates with potential application as imaging probes. The initial part of the work is focused on the synthesis of new DOTA-based bifunctional ligands. The chelator DOTA-AHA (1,4,7,10-tetraazacyclododecane-1-[(6-amino)hexanoic]- 4,7,10-triacetic acid) was successfully synthesized and characterized. This ligand was the starting point for the development of three sets of molecular constructs, which include dimeric ligands, PEGylated chelators and c(RGDWK) peptide bioconjugates. The Gd(III) chelates of DOTA-AHA, dimeric ligands and DOTA-AHA PEGylated ligands were obtained. All Gd(III) chelates were studied by variable temperature 1H NMRD (nuclear magnetic relaxation dispersion) and 17O NMR (nuclear magnetic resonance) spectroscopy in order to measure the relaxivity and the parameters that govern it. Gd(DOTA-AHA) and the binuclear chelates form weakly bound aggregates and even if the aggregates contain only 10 to 15% of the total amount of Gd(III) ions a marked increase in relaxivity between 30 and 100 MHz is observed. PEGylation did not show to be a very efficient process for relaxivity improvement. Despite the moderate water exchange rates of the PEGylated Gd(III) chelates and the high global rotational correlation times, these chelates present lower relaxivity values than the binuclear chelates. The distance between the two Gd(III) centers in the binuclear compounds has been determined by double electron-electron resonance (DEER) experiments and by molecular modelling studies giving comparable distances. 1H NMR spectra of paramagnetic lanthanide chelates of DOTA-A(PEG750)HA were recorded at different temperatures. The data obtained gave information on the structure and dynamics of the chelates in solution. In vitro studies with 67Ga-radiolabeled DOTA-AHA and DOTA-A(PEG750)HA showed that both chelates are extremely hydrophilic. The lack of biospecificity of 67Ga(DOTA-AHA) and [67Ga(DOTA-A(PEG750)HA)]- is revealed by their biodistribution profiles, which show that both radiolabeled chelates have significant uptake in major tissues.
O trabalho desenvolvido teve como objectivo o desenho, síntese e caracterização de novos quelatos de Gd(III) e Ga(III) com potencial aplicação como agentes de imagem. A parte inicial do trabalho focou-se na síntese de novos ligandos funcionais do tipo DOTA. O ligando DOTA-AHA (ácido 1,4,7,10-tetraazaciclododecano-1-[(6- amino)hexanóico]-4,7,10-triacético) foi sintetizado e caracterizado com sucesso. Este ligando foi o ponto de partida para o desenvolvimento de ligandos diméricos, ligandos PEGuilados e bioconjugados com o péptido c(RGDWK). Preparam-se os quelatos de Gd(III) do ligando DOTA-AHA, dos ligandos diméricos e dos ligandos PEGuilados. Todos os quelatos de Gd(III) foram estudados por DRMN (dispersão de relaxação magnética nuclear) e RMN (ressonância magnética nuclear) de 17O, de modo a obter os valores de relaxividade e os parâmetros que a afectam. O quelato Gd(DOTA-AHA) e os quelatos binucleares formam agregados fracamente ligados e apesar de os agregados só conterem 10 a 15% da quantidade total de iões Gd(III) verifica-se um aumento acentuado na relaxividade para frequências entre 30 e 100 MHz. A PEGuilação mostrou ser um processo pouco eficiente para melhorar a relaxividade. Apesar das constantes de troca de água dos respectivos complexos de Gd(III) se mostrarem consideráveis e dos seus elevados tempos de correlação rotacional globais, estes quelatos apresentam valores de relaxividade inferiores à dos quelatos binucleares. A distância entre os dois centros de Gd(III) nos compostos binucleares foi determinada por ressonância dupla electrão-electrão (RDEE) e por estudos de modelação molecular, tendo sido obtidos resultados comparáveis. Estudos de 1H RMN dos quelatos de DOTA-A(PEG750)HA com lantanídeos paramagnéticos foram efectuados a diferentes temperaturas. Os dados recolhidos forneceram informação sobre a estrutura e dinâmica destes quelatos em solução. Estudos in vitro com os ligandos DOTA-AHA e DOTA-A(PEG750)HA marcados com 67Ga mostraram que ambos os quelatos são extremamente hidrofílicos. A falta de bioespecificidade de 67Ga(DOTA-AHA) e [67Ga(DOTA-A(PEG750)HA)]- é evidenciada através dos perfis de biodistribuição destes radiocomplexos.
Fundação para a Ciência e Tecnologia PhD grant SFRH /BD/63676/2009.

Medical imaging is a technique that allows us to visualize non surgically the internal structure of the human body in order to diagnose or treat medical conditions. It permits also monitoring of physical processes or functions of different organs inside the body. The medical imaging encompasses wide range of techniques based on different physical prin- ciples, including techniques using ionizing radiation. The quality of the images depends significantly on the quality of the used imaging detectors. There are many types of the detectors, from old analog devices (e.g. films) to fully digital detectors such as flat panels, that are the most widely used today. The newer technology is being developed and the techniques such as photon counting explored. However, the state of the art technology is the single photon counting, where the experimental detectors such as Medipix are able to count and process each individual photon. This works studies the properties, features and applications of the newest detector from the Medipix family Timepix3 in different imaging modalities. Firstly, a design of a new hardware readout interface for Timepix3 is presented together with data acquisition software and new analysis and calibration algorithms. Then, different applications of Timepix3 detector were explored: very...

For all medical imaging systems using X-rays or γ-rays, radiation detector development in general and scintillator development in particular are in full progress. There is a strong interest in the introduction of new dense, high-atomic-number inorganic scintillation crystals with a high light yield and a fast response, especially for PET and SPECT. Powder scintillators are of interest for projection X-ray imaging. For PET, research is focused on CeP3+P doped scintillators, employing the 5d → 4f transitions. A high light yield is expected in the visible region. The time response in PET/CT applications will be in the 25–100 ns range. Improved energy resolution will also be a point of interest. For CT, time response requirements are at the microsecond level for decay time and the afterglow should be well below 10P−4Ps. For X-ray screens light spreading should be kept under control, e.g. by denser material like LSO:Ce, or columnar phosphors (CsI:TI) and by shorter luminescence emission wavelength which shows higher light attenuation of laterally directed photons. In this study we examine, both in powder and in crystal form, the detection efficiency of LuB2BSiOB5B:Ce, the absolute luminescence efficiency, the X-ray to luminescence efficiency, the spectral compatibility and the effective efficiency using various optical detectors. All these measurements were conducted in the X-ray energy range from 22 to 140 kVp used in medical X-ray imaging. In conclusion the X-ray quantum detection efficiency and the X-ray energy absorption efficiency of a LSO:Ce powder scintillator screen of 25 mg/cmP2 Pcoating thickness were found higher than currently employed materials (e.g. GdB2BOB2BS: Tb and CsI:Tl) for detection of X-rays used in mammographic applications. The absolute luminescence efficiency of this screen maintains high values, within the mammographic energy range and the intrinsic conversion efficiency was found close to that of CsI:Tl but lower than that of GdB2BOB2BS:Tb. In ragiographic energy range the screen of 172.5 mg/cmP2P exchibit the higher values of ALE and XLE. The emission spectrum of LSO:Ce screens showed excellent spectral compatibility with currently used digital detectors and taking also into account its very fast response it could be considered for applications in digital X-ray imaging systems. The LSO:Ce scintillator crystal shows higher absolute luminescence efficiency values (17,86 at 140kVp) than the corresponding of BGO crystal (3,40 at 140 kVp). LSO:Ce X-ray luminescence efficiency was found higher than the corresponding of BGO crystal in the whole range of energies used in our study. The higher value of DOG, 2430 gain units, showed at 140 kVp X-ray tube voltage for the LSO:Ce scintillator when the corresponding value at the same energy of the BGO is 1670 units. In the mammographic energy range the difference between the above measured values was smaller than the ones obtained in the radiographic energy region. This lead us to the assumption that LSO:Ce crystal can be efficiently used for X-ray energy imaging (under 100 kVp) as those used in CT applications. The intrinsic conversion efficiency was estimated to be significantly higher for LSO:Ce, which in addition is higher than more of the currently employed scintillators. The light emission spectrum of the LSO:Ce scintillator, peaking at about 420 nm, was found compatible to many currently employed optical photon detectors. Its very short scintillation decay time and its high detection efficiency, both in terms of QDE and EAE, they can be crucial for the applications of this scintillator in modern fast image producing X-ray computed tomography systems, especially those employed in combined PET/CT devices. 12/−−⋅⋅smRmWμ12/−−⋅⋅smRmWμ The comparison of the ALE and the XLE of the LSO:Ce single crystal scintillator with that of the efficient powder LSO:Ce scintillator shows that the LSO:Ce screens can be used: i) in modern scinti-mammography/ X-ray mammography systems in which one common fast scintillator in powder form may satisfy the requirements of both modalities and the strict requirements in spatial resolution and ii) in applications where single crystals have to be replaced by powder or ceramic scintillators in order to improve spatial resolution (eg. in ring type SPECT detectors and in combined SPECT/CT detectors). In addition, this comparison may be of interest since powder scintillators are of lower cost than the corresponding single crystals.
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碩士
國立陽明大學
生物醫學影像暨放射科學系暨研究所
98
Objectives: 90Y-SIR-Spheres® are currently used in the treatment of solid liver tumors. However, they cannot be clearly imaged in vivo post injection. Gamma imaging with 99mTc-MAA is currently adopted to predict the distribution of 90Y-SIR-Spheres® in vivo. This study aims to develop a novel 68Ga/111In-SIR-Spheres® as PET/SPECT imaging surrogate for distribution assessment and radiation dose estimation of 90Y-SIR-Spheres®. The distribution pattern of 68Ga-SIR-Spheres® and 99mTc-MAA was also evaluated. Methods: 68Ga/111In-SIR-Spheres® were prepared with high radiochemical yield and radiochemical purity (both >95%) after incubating 90Y-SIR-Spheres® with 68GaCl3 or 111InCl3. The in-vivo stability of 68Ga/111In-SIR-Spheres® was assessed based on the small animal PET/gamma imaging of normal SD rats after i.v. injection of radiotracers. The biodistribution study and PET/SPECT/CT imaging were performed in N1S1 hepatoma-bearing SD rats after intra-hepatic artery (i.a.) co-injection of 68Ga-SIR-Spheres® and 99mTc-MAA. Results: 68Ga- and 111In-SIR-Spheres® has the same size distribution (30.1±6.0 μm), similar to that of 90Y-SIR-Spheres® (30.1±9.1μm), and both showed good in vivo stability (> 90% at 1 h and 80% at 78 h, respectively). The tumor-to-liver ratios determined in biodistribution studies of 68Ga-SIR-Spheres® and 99mTc-MAA showed only weak correlation (r2=0.35, n=8). Similar results were found for the tumor-to-lung ratio (r2=0.31, n=8) after i.a. co-injection of 68Ga-SIR-Spheres® and 99mTc-MAA. However, co-injection of 68Ga-SIR-Spheres® and 111In-SIR-Spheres® resulted in highly correlated particle distribution in tumor and liver with a r2 of 0.997 (tumor-to-liver ratio). Conclusion: Significantly different distribution pattern between 68Ga-SIR-Spheres® and 99mTc-MAA (size distribution 26.6±18.2 μm) were observed, probably due to the difference in the size and the shape between radiolabeled SIR-Spheres® and 99mTc-MAA. Our study clearly indicated that 99mTc-MAA is not an ideal imaging surrogate of 90Y-SIR-Spheres® in the orthotopic hepatoma animal model.

Tese de mestrado em Engenharia Biomédica e Biofísica, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2012
Este relatório pretende ser um documento reflexivo e representativo dos conhecimentos adquiridos e das actividades desenvolvidas ao longo do Estágio Profissional em Aplicações Clínicas de Medicina Nuclear na Philips S.A. Deste modo, após uma contextualização teórica sobre a Medicina Nuclear que serviu de ponto de partida para o meu percurso nesta área, serão apresentadas as ferramentas de trabalho, ou seja, os equipamentos de Medicina Nuclear da Philips, a Câmara Gama e o sistema PET-CT, bem como os softwares de aquisição e processamento de imagem destes dois sistemas. A utilidade da imagem de medicina nuclear para diagnóstico clínico depende da forma como esta é adquirida e do processamento que sofre após a sua reconstrução. Como tal, o especialista de aplicações tem um papel determinante na optimização e personalização dos protocolos de aquisição de imagem dos clientes e na exploração dos métodos de processamento e quantificação de estudos de medicina nuclear junto dos prestadores de cuidados de saúde. Neste sentido, este trabalho apresentará alguns dos protocolos de aquisição e processamento de imagem que foram desenvolvidos com a minha colaboração, no serviço de Medicina Nuclear da Fundação Champalimaud. Os estudos apresentados têm como objectivo ser um exemplo ilustrativo do meu trabalho como Especialista de Aplicações de Medicina Nuclear e podem ser utilizados como referência para os utilizadores da Câmara Gama e da unidade PET-CT da Philips. Assim, estes doze meses de estágio representaram uma das maiores experiências da minha formação, pois nela foram desenvolvidas competências profissionais, pessoais e sociais que serão um trunfo no percurso como Engenheira Biomédica e Biofísica e que se encontram aqui afiguradas através dos conhecimentos teóricos e casos práticos relatados e pelo entusiasmo como são descritos.
This document is a reflection and an illustration of the knowledge and the activities developed during my clinical applications trainee in Nuclear Medicine at Philips S.A. Initially, I did an overview about Nuclear Medicine and after that I described my working tools, in other words, the Nuclear Medicine Devices of Philips: Gama Camera and PET-CT System, as well as the acquisition and processing software of both systems. The utility of Nuclear Medicine image in medical diagnostic depends on how the image is acquired and processed after its reconstruction. Thus, the Application Specialist plays a crucial role in the optimization and customization of image acquisition protocols of the customer. In addition, the Application Specialist should help the customer to acquire new studies that will allow the development of image processing and quantification strategies. Therefore, this document will present some of the acquisition and processing protocols developed with my collaboration in Nuclear Medicine Department of Champalimaud Foundation, in Lisbon. The purpose of the described studies is to be an illustrative example of my work as an Application Specialist of Nuclear Medicine and also be used as a reference to the Philips Gamma Camera and PET-CT users. In conclusion, I think that these twelve months of trainee have been one of the greatest experiences of my training, because they allowed me to develop my professional, personal and social skills which will help me grow as Biophysics and Biomedical Engineer. The acquired skills are presented throughout on this document with the knowledge and the study cases as well as the enthusiasm of how they are described.