Lutesyum-177 PSMA tedavisinde kantitatif SPECT/CT ile hastaya özgü dozimetri

ABSTRACT Çelik, G. Patient- Specific Internal Dosimetry with Quantitative SPECT/CT in Lutetıum-177 PSMA Treatment. Yeditepe University, Institute of Health Science, Department of Medical Physics, MSc Thesis, İstanbul. In present times, treating prostate cancer resistant to castration with modalities of nuclear medicine such as Lutetium-177 (Lu-177) marked PSMA (prostate-specific membrane antigen) has become more prevalent. Lu-177 with PSMA is administered intravenous, spreading radioactivity through the body of the patient. The agent, reaching the cancerous prostate cells and metastasis, shows its effect by the ionizing beta rays. PSMA also affects healthy tissues such as the kidney, salivary glands, and lacrimal glands, meaning that also healthy tissue is affected by the radiation. In order to avoid toxicity within the kidneys, administration of lower kidney doses are recommended. Hence, dosimetric calculations must be conducted before treating patients with Lu-177 PSMA. While the beta rays of Lu-177 treats the tumor, gamma rays and the SPECT system aids in visualizing the process, which is crucial when analyzing critical organs such as the kidney and their bio-breakdown progress over time of due to Lu-177. With this observational measurement (this information) and the MIRD (Medical Internal Radiation Dosimetry), the radiation level critical organs are exposed to can be calculated individually for each patient. In this study, we aim to plan an individual dosimetry for each patient undergoing Lu-177 PSMA treatment. In order to quantitatively visualize Lu-177 in the SPECT/CT system of the Yeditepe University Hospital Nuclear Medicine department, the necessary imaging and reconstruction parameters are determined. Furthermore, count-activity calibration is defined whereas the obtained data is conducted to determine specific dosimetry calculation for each patient individually. Currently, patient-specific dosimetry studies are being done by either SPECT systems used for visualization. Methods of visualization must be calibrated during the adjusting of the visualization parameters. In this thesis, the calibration and parameter are designated in order to plan patient-specific dosimetry studies. This scientific study will also aid another study currently conducted at the Yeditepe University Hospital Nuclear Medicine Department on DOTATATE, a different peptide connected to Lu-177, used for neuroendocrine tumor treatment, by also allowing for the calculation of patient-specific dosimetries. Additionally, this study will lead to the safe treatment of patients as well as new studies focusing on dose-reaction relationships at tumors in similar treatment modalities. Key words: Prostate Cancer, Nuclear Medicine Treatment, Dosımetry, Quantitative, Lutetıum