Calibration of In-Vivo Measurement Systems and Evaluation of Lung Measurement Uncertainties Using a Mathematical Voxel Phantom

Abstract

A voxel phantom has been developed to simulate <it>in vivo</it> measurement systems for calibration purposes. The calibration method presented here employs a mathematical phantom, produced in the form of volume elements (voxels), obtained through magnetic resonance images of the human body. The calibration method uses the Monte Carlo technique to simulate the tissue contamination, to transport the photons through the tissues and to simulate the detection of the radiation. The program simulates the transport and detection of photons between 0.035 and 2 MeV and uses, for the body representation, a voxel phantom with a format of 871 'slices' each of 277 x 148 picture elements. The Monte Carlo code is applied to the calibration of <it>in vivo</it> systems and to estimate differences in counting efficiencies between homogeneous and non-homogeneous radionuclide distributions in the lung. Calculations show a factor of 20 between deposition of 241Am at the back compared with the front of the lung.