| One can distinguished three types of nuclear medicine dosimetry: the dosimetry associated with diagnostic procedures, with therapy procedures, and the special case of bone dosimetry. In this dissertation, these three distinct areas are discussed. First, for diagnostic nuclear medicine dosimetry, a new series of five pediatric head and brain dosimetric models are developed, which extend the new adult MIRD model to pediatric patients. The EGS4 Monte Carlo transport code is used to tabulate absorbed fractions of energy for both photon and electron sources, which are subsequently used in the tabulations of radionuclide S values.;The development of new three-dimensional transport models of electrons in trabecular and cortical bones, represents the second dosimetric area considered in this dissertation. These new models are used with the EGS4-PRESTA code to calculate absorbed fractions of energy, considering the trabecular marrow space, endosteum, and bone volume as source and target regions. These absorbed fractions are then used to calculate bone site-specific S values. Skeletal averaged S values based on the site-specific S values are subsequently derived. Differences seen with previously published bone S values are fully analyzed in this document. The skeletal averaged S values are then used to compare the dosimetric advantage of beta emitting radionuclides in their use for the palliation of bone pain from bone metastases. As a result of this comparison, 33P is found to have the best dosimetric characteristics for the alleviation of bone pain.;The final part of this dissertation involves the dosimetry of nonuniform activity distribution in nuclear medicine therapy. The use of the MIRD methodology of dose calculation is introduced. Three-dimensional cumulated activity derived from SPECT images can be convoluted with S values calculated for the same voxel arrangement to generate average dose to voxels within the SPECT images. Voxel S values are calculated using the EGS4 Monte Carlo transport code for 21 voxel sizes ranging from 0.05 cm to 1.0 cm, for both photon and electron sources. A specific absorbed fraction interpolation schema is then derived for other voxel sizes. Examples of the use of this dose calculation method are also provided. |
