MIRD Pamphlet No. 17: The Dosimetry of Nonuniform Activity Distributions—Radionuclide S Values at the Voxel Level

Abstract

The availability of quantitative three-dimensional in vivo data on radionuclide distributions within the body makes it possible to calculate the corresponding nonuniform distribution of radiation absorbed dose in body organs and tissues. This pamphlet empha sizes the utility of the MIRD schema for such calculations through the use of radionuclide S values defined at the voxel level. The use of both dose point-kernels and Monte Carlo simulation methods is also discussed. PET and SPECT imaging can provide quantitative activity data in voxels of several millimeters on edge. For smaller voxel sizes, accurate data cannot be obtained using present imag ing technology. For submillimeter dimensions, autoradiographic methods may be used when tissues are obtained through biopsy or autopsy. Sample S value tabulations for five radionuclides within cubical voxels of 3 mm and 6 mm on edge are given in the appendices to this pamphlet. These S values may be used to