Abstract
1277
Introduction: GATE (GEANT4 application for tomographic emission) is an open source Monte Carlo (MC) software allowing for the in-silico simulation of theranostic scenarios dedicated to imaging and therapeutic applications such as image-based dosimetry. Y-90 microsphere radioembolization has been widely utilized to manage the patients with hepatic cell carcinoma (HCC), but it remains unclear whether the radiation dose can be estimated by MC simulation. The purpose of the study is to compare the dose calculated by Monte Carlo simulation and conventional partition model (PM). Method: We collected a data group of 21 patients undergoing SPECT/CT imaging of intra-arterial hepatic 99mTc macroaggregated albumin (99mTc-MAA) scan before 90Y selective internal radiotherapy (90Y SIRT). 3D distribution of cumulated activity was generated from 99mTc-MAA SPECT data. Absorbed doses at the voxel scale were then obtained with the GATE software (MCdose). Besides, estimated absorbed doses at the voxel scale were also calculated according to partition model (PMdose), based on empirical tissue density (1 g/mL for tumor and non-tumor liver and 0.3 g/mL for lung) and the voxel value of SPECT. The volume of interests (VOIs) of organ at risk (OAR), including right lung, left lung, tumor and non-tumor liver, were drawn on CT images using ITK-SNAP software. For each patient, the linear relationship between MCdose and PMdose were obtained in lung and solid organ (including tumor and non-tumor liver) using Pearson correlation analysis. Result: There are strong linear relationships between MCdose and PMdose in solid organ, with the range of R-square between 0.989 and 0.999. However, the linear relationships between MCdose and PMdose in lung are widely variable, with the range of R-square between 0.614 and 0.928,and there exists a tendency of increasing error at the higher level of voxel value of SPECT, especially in the lungs. Conclusion: The MC simulation is a suitable approach to estimating absorbed doses of 90Ymicrosphere in patients with HCC. The results showed excellent agreement between two different models in solid organ; however, it might be underfitting the absorbed doses in lung.