M.S.: Accurate Dosimetry in 131I Radionuclide Therapy Using Patient-Specific,3-Dimensional Methods for SPECT Reconstruction and Absorbed Dose Calculation

131I radionuclide therapy studies have not shown a strong rela-tionship between tumor absorbed dose and response, possibly due to inaccuracies in activity quantification and dose estima-tion. The goal of this work was to establish the accuracy of 131I activity quantification and absorbed dose estimation when pa-tient-specific, 3-dimensional (3D) methods are used for SPECT reconstruction and for absorbed dose calculation. Methods: Clinically realistic voxel-phantom simulations were used in the evaluation of activity quantification and dosimetry. SPECT re-construction was performed using an ordered-subsets expec-tation maximization (OSEM) algorithm with compensation for scatter, attenuation, and 3D detector response. Based on the SPECT image and a patient-specific density map derived from CT, 3D dosimetry was performed using a newly implemented Monte Carlo code. Dosimetry was evaluated by comparin