Realistic Phantom Series for OLINDA/EXM Version 2

DESCRIPTION (provided by applicant): The OLINDA/EXM code, which replaces the popular MIRDOSE code for calculating dose estimates in nuclear medicine applications, was given an exemption by the FDA on June 15, 2004 to be distributed as a medical device. The code will have a 3 year lifetime, and may be considered for re-release in June of 2007. The current code contains the traditional phantom types (Cristy/Eckerman), which are considered state-of-the-art in internal dosimetry today, but which many believe should be replaced with more realistic phantom types, as is being made possible by advanced medical imaging technologies and other approaches. More realistic representations of organ geometries and overlap provide better estimates of organ doses for use in diagnostic and therapeutic applications of radiopharmaceuticals in medicine, particularly in cancer therapy. The use of voxel-based Magnetic Resonance Imaging (MRI), Computed Tomography (CT), Single Photon Computed Tomography (SPECT) and Positron Emission Tomography (PET) imaging systems provide 3D representations of patient anatomy. Preliminary data comparing dose calculations from existing standard stylized (MIRD) models and those based on real human images have demonstrated some notable differences in calculated absorbed fractions and dose factors. Two standardized phantoms, one each representing the adult male and female, have been developed under the direction of the International Commission on Radiological Protection, and phantoms representing the newborn and pregnant woman at 7 months' gestation have also been designed. We propose extension of these works to develop a complete phantom library is needed to provide the user community with a full set of realistic phantoms for routine use in nuclear medicine. Other, more general radiation safety applications as well will benefit from these more realistic phantoms. Phase I of this project will entail review and testing of existing work, identification of specific phantoms necessary to complete the OLINDA/EXM library and gathering of candidate image data sets for segmentation. Phase II will entail the segmentation of the phantoms, modification of the phantoms to meet organ mass requirements, calculation of dose conversion factors for all organs, using Monte Carlo techniques, and implementation of results into the OLINDA/EXM code.