Dosimetric calculations in 90Y microsphere treatment

The aim of this study is to compare the mean absorbed doses of tumor, irradiated healthy parenchyma and whole liver obtained by 99mTc¬-MAA SPECT / CT and 90Y PET / CT images before and after treatment in patients receiving 90Y microsphere treatment. Patients with lung shunt fractions> 0.2 are excluded from the treatment. In total of 14 patients (8 females, 6 males, age: 35-76 years, totally 18 tumors) who underwent 90Y microsphere treatment at Yeditepe University Hospital between May 2018 and February 2019 participated in the study. SPECT images are obtained by injecting an average of 185 MBq 99mTc¬-MAA during angiography. The required administered activities for SPECT images were calculated based on VOIs (Volume of Interests) for tumor, irradiated healthy parenchyma and whole liver using the partition method. After 90Y treatment, PET / CT scan is performed and the absorbed dose was calculated with reference to 99mTc-MAA SPECT / CT images, areas for tumor, irradiated healthy parenchyma and whole liver using the same method as 99mTc¬-MAA SPECT. As a results; The absorbed dose of tumor, irradiated healthy parenchyma and whole liver calculated from PET / CT and SPECT counts were compared using Bland Altmann method and 87.5% of the values were found to be within the confidence interval. In this study, it can be said that activity planning based on 99mTc-MAA SPECT is related to 90Y microsphere PET / CT dosimetry calculated based on 99mTc-MAA SPECT areas. The 90Y microsphere PET / CT-based post-treatment dosimetry, based on the 99mTc-MAA SPECT areas, is an effective method for predicting treatment efficacy.