Accuracy of Monte Carlo simulations compared to in-vivo MDCT dosimetry

Purpose: The purpose of this study was to assess the accuracy of a Monte Carlo simulation-basedmethod for estimating radiation dose from multidetector computed tomography (MDCT) by comparingsimulated doses in ten patients to in-vivo dose measurements.Methods: MD Anderson Cancer Center Institutional Review Board approved the acquisition ofin-vivo rectal dose measurements in a pilot study of ten patients undergoing virtual colonoscopy. Thedose measurements were obtained by affixing TLD capsules to the inner lumen of rectal catheters.Voxelized patient models were generated from the MDCT images of the ten patients, and the doseto the TLD for all exposures was estimated using Monte Carlo based simulations. The Monte Carlosimulation results were compared to the in-vivo dose measurements to determine accuracy.Results: The calculated mean percent difference between TLD measurements and Monte Carlosimulations was ?4.9% with standard deviation of 8.7% and a range of ?22.7% to 5.7%.Conclusions: The results of this study demonstrate very good agreement between simulated andmeasured doses in-vivo. Taken together with previous validation efforts, this work demonstratesthat the Monte Carlo simulation methods can provide accurate estimates of radiation dose inpatients undergoing CT examinations.