| Περίληψη: | Neuroendocrine tumors (NETs) are a heterogeneous group of malignant neoplasms originating from the diffuse neuroendocrine system. Peptide receptor radionuclide therapy (PRRT) with radiolabeled somatostatin analogs has been studied in NETs for several years. It has proven to be a promising approach in managing patients with unresectable or metastatic NETs. Lutathera® (177Lu-DOTATATE) is an EMA and FDA approved radiopharmaceutical for PPRT in NETs. This treatment consists of 4 cycles with an 8-week interval between them. Dosimetry is essential to track the absorbed dose in lesions and organs at risk to optimize treatment and avoid radiation-related toxicity.
The aim of this thesis is the comparative evaluation of the commercial dosimetric software Planet® Onco (DOSIsoft SA, Cachan, France) and the open-source toolkit GATE, which is a well-validated and reliable tool adapted by the scientific community for the absorbed dose calculation.
The dosimetry was based on clinical data such as CT images to create attenuation maps and SPECT images to compute the biodistribution maps of 177Lu in the patient. For the dose calculation with Planet®, we need imaging data (SPECT/CT images) from multiple time points. After the registration of all the time points to T0, the liver, the spleen and the right and left kidneys were segmented. The pharmacokinetics computation was performed next, generating time-activity curves, and the dose was finally calculated using the desired fitting method. In this study we used both bi- and tri-exponential fitting for the dose calculation.
The mean absorbed dose values calculated with GATE, Planet®(bi-exp) and Planet®(tri-exp) were in concordance with the literature. The results of the bi-exponential fitting were similar to the GATE, while the tri-exponential fitting had higher relative differences.
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