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Background: Platelet-Derived Growth Factor Receptor β (PDGFRβ) plays an important role in multiple diseases including cancer and fibrotic diseases. Conventional detecting method is using biopsy, which is an invasive method and false-negative would be taken place. An alternative method is using radio molecular imaging, for example Positron emission tomography (PET) imaging. It is non-invasive and could detect the changes on the molecular level. Previous have reported two tracers, which are 68Ga-DOTA-Z09591 (PET) and 111In-DOTA-Z09591 (SPECT) respectively, that performed a high affinity and biodistribution contrast. In this thesis, four additional analogues of Z09591 were investigated: 18F-RESCA-Z09591, 68Ga-NOTA-Z09591, 18F-Tetrazine (Tz)-AMIDE-Z09591 and 18F- Tz-ESTER-Z09591. In in-vitro binding specificity and in-vivo biodistribution was compared to previous tracer 68Ga-DOTA-Z09591.

Methods: For in-vitro binding studies, the autoradiography of frozen U-87 glioma cells sections was employed. For in-vivo biodistribution study, U-87 MG glioma cells were xenografted in immunodeficient mice. After tumor was observed, the tracers were tail intravenous injected into mice and then be euthanized. Then radioactivity of each organ was measured by well counter.

Results: For in-vitro study, 18F-RESCA-Z09591 showed the best binding specificity (with molar density 29.05±1.121fmol/mm3) compared to 68Ga-NOTA-Z09591 (with molar density 16.66±0.8351fmol/mm3), 68Ga-DOTA-Z09591 (with molar density 5.24±0.3916fmol/mm3), 18F-Tz-AMIDE-Z09591 (with molar density 15.2±2.635fmol/mm3), 18F-Tz-ESTER-Z09591 (with molar density 6.41±0.227fmol/mm3). For in-vivo study, although the organ biodistribution of 18F-RESCA-Z09591 was lower than other groups, the tumor to organ ratio of 18F-RESCA-Z09591 was higher than other groups, including 68Ga-NOTA-Z09591, 68Ga-DOTA-Z09591, 18F-Tz-AMIDE-Z09591 and 18F-Tz-ESTER-Z09591.

Conclusion: 18F-RESCA-Z09591 is a new analogue PET tracer targeted to PDGFRβ and it has showed improved in-vitro binding specificity, contrast and in-vivo sensitivity than other tracers, especially in liver. It is therefore a candidate for imaging of liver fibrosis.