In the research reported in this dissertation, the concept of classic conjugate imaging, a non-tomographic nuclear medicine technique, is modified such that activity of a radiopharmaceutical distribution in the striata can be estimated. A mathematical model is developed that extended the application of classic conjugate imaging to estimation of two distinct and aligned activity distributions. Error analysis of the mathematical model is performed to characterize the accuracy of the model and to benchmark the limitations of the model. Phantom experiments are performed to demonstrate the practical application of the model and to evaluate its accuracy. A Monte Carlo simulation model of conjugate imaging of activity uptake in the striata of a primate is developed to evaluate the accuracy of the modified conjugate imaging technique as applied in the use of a dedicate conjugate imaging system. In addition, the simulation model is used to determine and characterize the shielding design of the small field of view gamma cameras comprising the dedicated conjugate imaging system. The application of scatter correction is investigated to address the downscatter of high-energy photon emissions into the photopeak window and the inclusion of scattered primary photons in the photopeak window. In this dissertation, it is shown that the modified conjugate imaging technique developed can be used to estimate accurately activity uptake in each of two distinct and aligned activity distributions. The accuracy of the technique is shown to be comparable to that of clinical quantitative SPECT. The modified conjugate imaging technique used with the dedicated conjugate imaging system may, therefore, be a viable quantitative nuclear medicine technique for activity estimation of radiopharmaceutical uptake in the striata of Parkinsonian and schizophrenic patients. The portability and low cost relative to SPECT systems make a dedicated conjugate imaging system advantageous for clinics with Parkinsonian and schizophrenic patients, who are unable to travel due to physical or mental limitation.

Inom nuklearmedicin exponeras personal dagligen för joniserande strålning. Det kan vara både i form av en öppen strålkälla vid uppdrag av radiofarmaka och vid bildtagning där personalen hjälper och ger stöd till patienten som blivit injicerad. Vid uppdrag av radiofarmaka används strålskydd i form av sprutskydd och distansverktyg medan blyförkläde används vid kontakt med patienter. Dessa skydd är till för att minska skador som kan uppstå vid exponering. Den svenska strålsäkerhetsmyndigheten (SSM) har föreskrivit dosgränser som inte får överskridas för att minska risken för skador. Teknetium-99m (99mTc) är den vanligaste radionukliden inom den nuklearmedicinska verksamheten. Syftet med denna studie var att kartlägga strålningsexponeringen för personal som jobbar med 99mTc och på så sätt visa behovet av olika typer av strålskydd för att reducera stråldosen. I denna studie utfördes fingerdosmätningar vid uppdrag av 99mTc med hjälp av termoluminiscenta dosimetrar som placerades på de tre mest utsatta fingrarna, digitus I-III, bilateralt. Mätningarna genomfördes vid uppdrag utan strålskydd, med en pincett och med fullt strålskydd (sprutskydd samt två pincetter). Studien innefattar även stråldosmätningar med och utan blyförkläde för myokardscintigrafi, skelettscintigrafi och lungscintigrafi. Dessa mätningar utfördes med en direktavläsande personal electronic dosimeter (PED) där den effektiva dosen registrerades. Resultaten för fingerdosmätningarna visar en signifikant skillnad i stråldos beroende på om och vilket strålskydd som används. Högst dos fick de som drog upp helt utan strålskydd och vänster långfinger fick den högsta ekvivalenta dosen. För stråldosmätningarna med och utan blyförkläde utfördes ett Mann-Whitney U-test som visade ett p-värde på <0,05 vilket tyder på att det finns en statistisk signifikant skillnad. Högst effektiv dos uppmättes vid lungscintigrafi för personal som inte använde blyförkläde. / Personnel working with radiopharmaceuticals in the nuclear medicine department are exposed to radiation on the daily basis. The source of radiation can both be open as in the withdrawal procedure and external as when the patient has been injected and ready for imaging. There are different types of radiation protection depending on which task that is performed. Syringe shielding and distance tools are used during the withdrawal and lead aprons are used when positioning the patient under the camera. The Swedish radiation safety authority (SSM) prescribe dose limits to reduce any risk of injury connected to radiation. These limits must not be exceeded. Technetium-99m (99mTc) is the most common radiopharmaceutical in the nuclear medicine department. The purpose of this study was to study the radiation exposure to personnel working with 99mTc and evaluate the need for radiation protection to reduce the radiation dose. This study includes measurement of the equivalent dose to the three most exposed fingers, digitus I-III bilateral, during the withdrawal of 99mTc. Thermoluminiscent dosimeters was used to detect radiation and was placed on top of the finger. The measurements were performed without radiation shielding, with only one tweezer as distance tool and with full radiation shielding (syringe shielding and two tweezers as distance tools). It also includes measurement of the effective dose during myocardial scintigraphy, bone scan and lung scintigraphy with or without lead apron. For these measurements a personal electronic dosimeter was used to detect radiation. The result of the finger doses showed a significant difference in radiation dose depending on which protection was used. The highest dose was recovered from not using any protection at all and the highest equivalent dose was obtained by left middle finger. For the measurement regarding the effective dose with or without lead apron a Mann-Whitney U-test was performed and showed a p-value of <0,05 which indicates a statistical significant difference. The highest effective dose was recovered from lung scintigraphy when the personnel was not wearing a lead apron.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第19175号 / 医博第4017号 / 新制||医||1010(附属図書館) / 32167 / 京都大学大学院医学研究科医学専攻 / (主査)教授 渡邊 直樹, 教授 松原 和夫, 教授 横出 正之 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Technetium-99m (99mTc) radiopharmaceuticals are widely used for diagnostic imaging of heart, kidney, and liver disease, and cancer. Evolution from perfusion type tracers to targeted agents however has proven difficult. 99mTc labeled antibodies for imaging specific disease biomarkers would be of great interest, however the disparity between the isotopes half-life (6 hours) and the long circulation time of most antibodies (multiple days) has been a significant barrier. Furthermore, the conjugation of bifunctional 99mTc-chelate complexes to small molecules often has a detrimental impact on targeting. The use of bioorthogonal chemistry derived from tetrazines and trans-cyclooctene derivatives, along with pretargeting has the potential to overcome these issues and create a new generation of targeted 99mTc radiopharmaceuticals. Initially, the synthesis of three generations of imidazole based tridentate chelates linked to a tetrazine was completed. These new ligands were labeled with 99mTc under mild conditions (60 °C, 20 min, pH 3.5) with modest to good radiochemical yields ranging from 31 to 83%. Biodistribution studies revealed that compound 14, which contains a polyethylene glycol 5 (PEG5) linker had the best clearance from non-target tissues. Compound 14 was also used successfully in a pretargeting strategy along with a transcyclooctene (TCO) derivative of the bone targeting bisphosphonate, alendronate (ALN). One hour following the administration of TCO-ALN to BALB/c mice, compound 14 was injected intravenously where uptake at sites of high calcium turn over (i.e. the joints) was observed. At 6 hours post injection, for example, uptake reached as high as 20.1 ± 4.91 and 16.1 ± 4.84 %ID/g in the knee and shoulder, respectively. Pretargeted imaging studies were performed subsequently with a TCO-functionalized huA33 antibody in mice bearing SW122 xenografts. The TCO-huA33 antibody was injected 24 hours before the administration of two radiolabeled tetrazines at high and low specific activities. At 6 hours post injection tumour uptake was minimal, with tumour: blood ratios <1 in all cases. Blood clearance studies determined that the tetrazines were being cleared rapidly, with a blood residence half-life of 1.3-2.1 minutes. The hypothesis is that the low concentration of the antibody (owing to its high molecular weight), combined with the rapid clearance of the tetrazine and significant off-target uptake resulted in unfavorable kinetics and low tumor binding. Studies of the clearance pathway of 14 were investigated with clinically approved hepatobiliary transport inhibitors to help understand the mechanism of clearance, which could in turn be used to optimize the pharmacokinetics of the tetrazine ligands. A range of different inhibitors of key clearance pathways were evaluated with limited success. However, co-administration of 14 with ALN resulted in a 75% decrease in gall bladder uptake of 14 (216 ± 75.9 to 33.6 ± 3.93 %ID/g). Pretargeting studies of 14 with TCO-ALN in the presence of excess ALN revealed that ALN did not hinder the uptake of TCO-ALN in the bone, with all organs and tissues having the same uptake with TCO-ALN or TCO-ALN + ALN (knee: 20.1 ± 4.91 and 14.9 ± 2.43 %ID/g, respectively). There was also a concomitant decrease in gall bladder uptake (91.5 ± 17.1 to 28.8 ± 2.63 %ID/g). Further work on improving the distribution of the tetrazine ligands involved investigating the effect of the chelate. The core chelate found in 14 without the tetrazine moiety (compound 11a) was labeled with 99mTc to produce 11b in a 31% radiochemical yield. Biodistribution studies of 11b and 14 at 6 hours post injection demonstrated that the imidazole-based 99mTc-chelate was a major factor in the rapid and significant uptake and retention in the liver and gallbladder. A new triazole based chelate with optimal clearance from Kluba and coworkers was synthesized in 45% yield and successfully labeled with 99mTc (compound 23a). Biodistribution studies were performed where at 6 hours post injection, 23a had five times lower uptake in all non-target organs compared to 11b. The synthesis of a tetrazine derivative of 23a (compound 32) unfortunately demonstrated high hepatobiliary uptake compared to the original triazole chelate (gall bladder: 228 ± 251 and 8.77 ± 0.73 %ID/g, large intestine: 85.5 ± 83.5 and 6.88 ± 0.30 %ID/g, respectively). This particular derivative had a lipophilic linker as a result of the synthetic challenges faced during the preparation of a more hydrophilic triazole-tetrazine derivative. In addition to pretargeting applications, the 99mTc-tetrazine was used as a reagent to create multimodal imaging agents. Nanoscale gas vesicle (GV) ultrasound contrast agents were functionalized with TCO via an amide coupling to lysine residues. TCO-GVs were then radiolabeled by adding compound 6 where the desired product, a new multimodal probe, was obtained in 59% radiochemical yield. SPECT imaging and biodistribution studies in mice were completed where the labeled GV’s showed uptake in the gall bladder (120 ± 29.1 %ID/g), liver (16.8 ± 7.50 %ID/g), lungs (3.26 ± 1.53 %ID/g), small intestines (14.5 ± 5.30 %ID/g), and spleen (5.47 ± 2.71 %ID/g) at 120 min post injection. In addition to radiolabelling, the TCO-GVs were also functionalized with a near IR-tetrazine dye to produce a multimodal ultrasound/photoacoustic (US/PA) imaging agent in a 68% yield. / Thesis / Doctor of Philosophy (PhD)

Hintergrund: Ein sehr häufig in der nuklearmedizinischen Diagnostik genutztes Radionuklid ist 99mTc. Es emittiert Gammastrahlung mit einer relativ niedrigen Energie (140 keV) und hat eine kurze Halbwertszeit von 6 h. Zusätzlich zur Gammastrahlung entstehen bei jedem Zerfall von 99mTc Auger-Elektronen. Diese niederenergetischen Elektronen, sehr kurzer Reichweite verfügen über einen hohen LET und erzeugen somit eine ausreichende Energiedeposition, um direkte DSB zu erzeugen. Bei Untersuchungen zu Chemotoxizität und Radiotoxizität mit Zellexperimenten gilt es eine Vielzahl an verschiedenen Schutzmechanismen, Reparaturmechanismen und Signalkaskaden in Zellen zu beachten, welche häufig noch nicht vollständig erforscht sind. Um das schädigende Potential von unterschiedlichen Substanzen und Strahlenqualitäten auf die DNA zu untersuchen, wurde ein zellfreies System gewählt. Ziel dieser Arbeit war es, neben den Strahlenqualitäten der Alpha-, Beta, Gamma- und Röntgenstrahlung die Auger-Elektronen des 99mTc auf ihr Potential zur Induktion von DNA-Strangbrüchen zu untersuchen. Hierfür stand die Substanz 99mTc-HYNIC-DAPI zur Verfügung, welche 99mTc an das Plasmid binden und somit in direkte DNA-Nähe bringen kann. Material und Methode: Alle Versuche wurden mit dem Plasmid pUC 19, einem künstlich hergestellten, bakteriellen Plasmid mit 2686 Basenpaaren, welches als nackte DNA ohne Proteine vorliegt, durchgeführt. Der Vergleich zwischen bestrahltem Plasmid in Ab- und Anwesenheit des Radikalfängers DMSO gibt Hinweise darauf, ob Strangbrüche direkt induziert oder nach Radikalbildung indirekt erzeugt werden. Bei radikalvermittelter Wirkung verhindert DMSO DNA-Strangbrüche und die ungeschädigte Supercoiled-Plasmid-Konformation bleibt erhalten. Nach Bestrahlung des Plasmids erfolgte der Nachweis von Strangbrüchen mittels Agarose-Gelelektrophorese. Bekommt ein Plasmid Einzel- oder Doppelstrangbrüche, so verändert sich seine Konformation zu einem ringförmigen/open circle (ESB) oder einem linearen Plasmid (DSB). Durch veränderte Laufeigenschaften im Agarosegel sind die verschiedenen Konformationen voneinander trennbar. Nach Anfärben der DNA mit dem Fluoreszenzfarbstoff Ethidiumbromid konnte das fluoreszierende Plasmid fotografiert und die Intensität der Konformationsbanden quantifiziert werden. Ergebnisse: Zuerst wurde die Reproduzierbarkeit der Methodik überprüft und festgestellt, dass eine Korrelation zwischen Plasmidmasse und Fluoreszenzintensität besteht. Anschließend wurde in Vorversuchen gezeigt, dass die Inkubationstemperaturen, pH-Werte und der Radikalfänger DMSO keinen Einfluss auf die Plasmidintegrität haben. Bei Bestrahlung mit Röntgenstrahlung, dem Beta-Strahler 188Re und dem nicht DNA-gebundenen Gamma-Strahler und Auger-Emitter 99mTc konnte mit steigender Dosis eine Zunahme an ESB festgestellt werden. Vergleichsproben mit DMSO zeigten keinen Anstieg von ESB, was auf eine radikalvermittelte 67 DNA-Schädigung mittels Reaktiver Sauerstoffspezies (ROS) hinweist. Ab einer Energiedosis von ca. 80 Gy konnten nach Bestrahlung mit 188Re und 99mTc zusätzlich zu den ESB auch DSB nachgewiesen werden. DMSO konnte in den Vergleichsproben sowohl die ESB als auch die DSB erfolgreich verhindern. Bei einer sehr hohen Dosis ≥ 600 Gy zeigte DMSO Kapazitätsgrenzen und es konnten nicht mehr alle Strangbrüche verhindert werden. Die Bestrahlung mit dem Alpha-Strahler (hoher LET) 223Ra fügte, im Vergleich zu Strahlung mit niedrigem LET, dem Plasmid überproportional viele DSB zu. Einige dieser DSB konnten nicht durch DMSO verhindert werden, was auf einen direkten DNA-Schaden bzw. eine zu hohe Radikaldichte hinweist. Ein noch stärkerer direkter Effekt konnte beobachtet werden, wenn 99mTc über die Substanz 99mTc-HYNIC-DAPI an DNA gebunden wurde. Dabei konnten schon ab einer Energiedosis von 4 Gy DSB erzeugt werden, welche trotz Radikalfänger nicht verhindert werden konnten. Schlussfolgerung: Dieser bei 99mTc-HYNIC-DAPI beobachtete Effekt wird den Auger-Elektronen zugeschrieben. Aufgrund ihrer kurzen Reichweite und ihres hohen LET sind sie in der Lage direkte DSB zu erzeugen, wenn sie DNA-gebunden sind oder sich in geringem Abstand zur DNA befinden. Die Ergebnisse der Experimente weisen auf ein therapeutisches Potential von 99mTc hin. Weitere Untersuchungen müssen zeigen, ob eine Adressierung von 99mTc an die DNA im Zellkern einer intakten Zelle zu verwirklichen ist und ob DNA-gebundenes 99mTc durch die Energie der Auger-Elektronen den Zelltod herbeiführen kann. Im nächsten Schritt sollte die Erforschung von Trägersubstanzen erfolgen, welche es ermöglichen Auger-Emitter spezifisch an die DNA von Tumorzellen zu koppeln. / Introduction and aim of the study: A radionuclide commonly used in diagnostic nuclear medicine is 99mTc. It emits gamma rays with a relatively low energy (140 keV) and has a short half-time (6h). In addition to gamma rays, 99mTc radiates so called Auger-electrons with low energy, low range and high linear energy transfer. Due to the high-LET Auger-electrons have a sufficient energy deposition to induce direct double-strand breaks to the DNA. In these experiments we used plasmid DNA to evaluate damage induced to biological systems by different chemotoxical substances and radionuclides as well as external radiation. By using plasmids instead of cell cultures we avoid lots of unexplored signal pathways in cells and it is possible to quantify chemotoxical and radiation damage to the DNA. Materials and methods: The double-stranded plasmid pUC 19 with 2686 bp is used in all experiments. It is a synthetically produced bacterial plasmid without any proteins. To distinguish between directly and indirectly (radical induced) induced damage we used the radical scavenger DMSO. Indirectly induced damage via reactive oxygen species (ROS) can be prevented by DMSO. The quantification of supercoiled forms, single strand breaks (SSB) and double strand breaks (DSB) was measured by the method of agarose gel electrophoresis. After the electrophoresis, agarose gels are dyed in ethidium bromide and imaged with a ccd-camera using ultraviolet transillumination. The bands of the different plasmid forms were quantified through the FIJI computer program. Results: First of all a correlation between plasmid mass and fluorescence intensity was shown. In a pretrial no damaging effect to the plasmid from incubation temperature, pH-value and radical scavenger DMSO appeared. Afterwards we examined chemotoxical SnCl2, external x-rays, the alpha emitter 223Ra, the beta emitter 188Re, gamma- and Auger-emitter 99mTc and the DNA-bound 99mTc-HYNIC-DAPI. The radical scavenger DMSO was used to differentiate between indirect (radical induced) and direct DNA-damage. All different radiation qualities showed an increasing DNA-damage with increasing energy dose. For the low-LET radiation qualities like chemotoxical SnCl2, external x-rays, the beta emitter 188Re and not DNA-bound 99mTc, DMSO showed the quality to prevent the damage. After the deposition of an energy dose ≥ 600 Gy DMSO showed a limitation in his scavenger capacity. During radiation with high-LET beams like 223Ra or DNA-bound 99mTc-HYNIC-DAPI DMSO showed less or nearly no ability to prevent DNA-damage. A 4 Gy dose of 99mTc-HYNIC-DAPI was able to induce DSB into the plasmid. These DSB could not be prevented by DMSO. The lower ESB:DSB ratio for high-LET beams also displays that direct damage is more likely to create DSB than indirect damage. Conclusion: In conclusion we can say that DNA-bound 99mTc-HYNIC-DAPI was most appropriate to induce DSB via a direct effect. It was impossible to prevent this damage due to adding the 69 radical scavenger DMSO. We attribute this to low range, low-LET Auger-electrons and suppose that it may be possible to use DNA-bound 99mTc for therapeutic purpose. Further research has to show if 99mTc can be targeted to the DNA of intact cells and if suitable tracers can be found to safely target and kill tumor cells.

A imagem molecular oferece a perspectiva de detectar doenças bem antes de os sintomas surgirem. A vasculatura tumoral é vital no crescimento do tumor e na disseminação de metástases, sendo assim alguns radiofármacos são dirigidos para a angiogênese. O glioma, tumor cerebral de baixa incidência porém alta mortalidade, requer um diagnóstico precoce para favorecimento da abordagem terapêutica. O objetivo desse estudo foi o desenvolvimento de novo radiofármaco para diagnóstico por imagem de glioma, baseado em peptídeos angiogênicos (GX1 e GX1-RGD) marcados com o radioisótopo tecnécio-99m. O desempenho dos conjugados peptídicos mostraram-se bastante parecidos em diversas avaliações. Eles foram radiomarcados com alta pureza radioquímica (>96%) e estáveis em soro até pelo menos 4h. Ambos são hidrofílicos e com baixa ligação às proteínas plasmáticas. A biodistribuição em animais sadios demonstrou alta excreção renal e depuração sanguínea rápida para ambos os radiotraçadores. Nos estudos in vitro, o 99mTc-HYNIC-PEG4-c(GX1) apresentou picos de ligação aos 60 min e o 99mTc-HYNIC-E-[c(RGDfk)-c(GX1)]) aos 120 min, nas células endoteliais HUVEC, usadas como controle, e nas células tumorais das linhagens U87MG e T98G. A captação tumoral nos animais foi mais acentuada para células U87MG, especialmente para o 99mTc-HYNIC-E-[c(RGDfk)-c(GX1)]) (2,87 ± 0,53% DI/g) aos 60 min p.i., com boa visualização em imagens adquiridas por gama-câmara e micro-SPECT/CT. Estudos realizados com os peptídeos conjugados à nanopartículas magnéticas para visualização em ressonância magnética também demonstraram especificidade dos produtos em tecidos tumorais. O desempenho do 99mTc-HYNIC-E-[c(RGDfk)-c(GX1)]) foi superior que o do traçador GX1, quanto à captação no glioma humano, podendo ser considerado como um promissor radiofármaco para diagnóstico de gliomas. / Molecular imaging offers the prospect of detecting diseases well before the symptoms appear. The tumor vasculature is vital in the tumor growth and dissemination of metastasis, thus some radiopharmaceuticals are directed to angiogenesis. The glioma, a brain tumor of low incidence but high mortality, requires an early diagnosis for favoring therapeutic approaches. The aim of this study was the development of a new radiopharmaceutical for imaging diagnosis of glioma, based in angiogenic peptides (GX1 and RGD-GX1) radiolabeled with technetium-99m radioisotope. The peptidic conjugates showed very similar performance in several evaluation. They were radiolabeled with high radiochemical purity (>96%) and are stable in the blood serum at least for four hours. Both are hydrofilic and had minimal binding to plasma protein. The biodistribution in healthy mice at many times, showed high renal excretion and fast blood clearance for both radiotracers. At in vitro studies, the 99mTc-HYNIC-PEG4-c(GX1) exhibit binding peaks at 60 min and the 99mTc-HYNIC-E-[c(RGDfk)-c(GX1)]) at 120 min, at HUVEC endotelial cells, used as control, and at tumor cell lines U87MG and T98G. The animal tumor uptake was more pronounced for U87MG cells, specially for 99mTc-HYNIC-E-[c(RGDfk)-c(GX1)]) (2.87 ± 0.53% DI/g) at 60 min p.i., with good visualization in images acquired with gama-camara and micro-SPECT/CT. Studies performed with peptides conjugate to magnetonanoparticles for MRI visualization also demonstred the peptides specificity in tumor tissue.The 99mTc-HYNIC-E-[c(RGDfk)-c(GX1)]) performance was superior to the GX1 tracer, regarding the glioma uptake, and may be consider as a promisser radiopharmaceutical for glioma diagnosis.

A imagem molecular oferece a perspectiva de detectar doenças bem antes de os sintomas surgirem. A vasculatura tumoral é vital no crescimento do tumor e na disseminação de metástases, sendo assim alguns radiofármacos são dirigidos para a angiogênese. O glioma, tumor cerebral de baixa incidência porém alta mortalidade, requer um diagnóstico precoce para favorecimento da abordagem terapêutica. O objetivo desse estudo foi o desenvolvimento de novo radiofármaco para diagnóstico por imagem de glioma, baseado em peptídeos angiogênicos (GX1 e GX1-RGD) marcados com o radioisótopo tecnécio-99m. O desempenho dos conjugados peptídicos mostraram-se bastante parecidos em diversas avaliações. Eles foram radiomarcados com alta pureza radioquímica (>96%) e estáveis em soro até pelo menos 4h. Ambos são hidrofílicos e com baixa ligação às proteínas plasmáticas. A biodistribuição em animais sadios demonstrou alta excreção renal e depuração sanguínea rápida para ambos os radiotraçadores. Nos estudos in vitro, o 99mTc-HYNIC-PEG4-c(GX1) apresentou picos de ligação aos 60 min e o 99mTc-HYNIC-E-[c(RGDfk)-c(GX1)]) aos 120 min, nas células endoteliais HUVEC, usadas como controle, e nas células tumorais das linhagens U87MG e T98G. A captação tumoral nos animais foi mais acentuada para células U87MG, especialmente para o 99mTc-HYNIC-E-[c(RGDfk)-c(GX1)]) (2,87 ± 0,53% DI/g) aos 60 min p.i., com boa visualização em imagens adquiridas por gama-câmara e micro-SPECT/CT. Estudos realizados com os peptídeos conjugados à nanopartículas magnéticas para visualização em ressonância magnética também demonstraram especificidade dos produtos em tecidos tumorais. O desempenho do 99mTc-HYNIC-E-[c(RGDfk)-c(GX1)]) foi superior que o do traçador GX1, quanto à captação no glioma humano, podendo ser considerado como um promissor radiofármaco para diagnóstico de gliomas. / Molecular imaging offers the prospect of detecting diseases well before the symptoms appear. The tumor vasculature is vital in the tumor growth and dissemination of metastasis, thus some radiopharmaceuticals are directed to angiogenesis. The glioma, a brain tumor of low incidence but high mortality, requires an early diagnosis for favoring therapeutic approaches. The aim of this study was the development of a new radiopharmaceutical for imaging diagnosis of glioma, based in angiogenic peptides (GX1 and RGD-GX1) radiolabeled with technetium-99m radioisotope. The peptidic conjugates showed very similar performance in several evaluation. They were radiolabeled with high radiochemical purity (>96%) and are stable in the blood serum at least for four hours. Both are hydrofilic and had minimal binding to plasma protein. The biodistribution in healthy mice at many times, showed high renal excretion and fast blood clearance for both radiotracers. At in vitro studies, the 99mTc-HYNIC-PEG4-c(GX1) exhibit binding peaks at 60 min and the 99mTc-HYNIC-E-[c(RGDfk)-c(GX1)]) at 120 min, at HUVEC endotelial cells, used as control, and at tumor cell lines U87MG and T98G. The animal tumor uptake was more pronounced for U87MG cells, specially for 99mTc-HYNIC-E-[c(RGDfk)-c(GX1)]) (2.87 ± 0.53% DI/g) at 60 min p.i., with good visualization in images acquired with gama-camara and micro-SPECT/CT. Studies performed with peptides conjugate to magnetonanoparticles for MRI visualization also demonstred the peptides specificity in tumor tissue.The 99mTc-HYNIC-E-[c(RGDfk)-c(GX1)]) performance was superior to the GX1 tracer, regarding the glioma uptake, and may be consider as a promisser radiopharmaceutical for glioma diagnosis.

No description available.

<p> Cell therapy for Parkinson's disease will greatly benefit from progress in methods aimed at visualizing the dopamine system and cell replacement techniques. Currently, cell therapy has been met with varied success, in part due to differences in cell sources, transplantation procedures, and our lack of understanding of cell fate post-transplantation. The standardization of transplantation procedures will enhance our ability to draw comparisons between studies and improve cell therapy outcomes. We developed a method to label neural stem/progenitor cells (NSPCs) with technetium-99m and then visualize the cells with single photon emission computed tomography (SPECT) subsequent to grafting in the brain. This labeling method permitted a high uptake of the tracer into the cells without causing damage to the DNA or altering cell viability. The labeling caused a significant decrease (75%) in the proliferative capacity of the SPCs and caused a trend towards an increase in neuronal differentiation. Using this technique paves the way to standardize the location of the transplant and quantify the number transplanted cells while increasing the production of neurons.</p> <p> Experiments were performed to visualize the dopamine system with [(123)I]altropane at pre-and post-transplant time points in the 6-0HDA rat model of Parkinson's disease. [(123)I]altropane binding correlated with the content of dopamine in the stria tum. However, [(123)I]altropane binding was not correlated with dopamine content in the substantia nigra and did not show a correlation with the amphetamine rotations. However, there was a significant correlation with the cylinder test and the postural instability test. When the data was assessed using linear regression, the r^2 value of the linear relationship was low indicating that [(123)I]altropane SPECT is not a good predictor of behavioural outcome due to a weak linear relationship. Our data indicates that [(123)I]altropane predicts the integrity of the striatal dopamine nerve terminals, but does not predict the integrity of the nigrostriatal system. The results are discussed in relation to the use of [(123)I]altropane in comparison to other dopamine SPECT and PET agents. </p> / Thesis / Doctor of Philosophy (PhD)

No description available.