Measurement of Absorbed Fractions for Photon Sources Distributed Uniformly in Various Organs of a Heterogeneous Phantom

A physical representation of the Snyder-Fisher heterogeneous mathematical phantom has been designed and constructed. The physical phantom contains skeletal components, lungs and soft-tissue regions similar to the mathematical Snyder-Fisher phantom. The phantom is suitable for studies of radiation dose distributions involving both internally and externally applied radiation fields. A description of the phantom and its composition is given. Dose distributions were measured within the phantom resulting from photon emitters distributed uniformly in selected organs. These distributions were used to calculate absorbed fractions for the mathematically defined phantom organs. These absorbed fractions are given and compared with the absorbed fraction estimates by Snyder et al. In general, estimates of the absorbed fractions, obtained experimentally, fall within the range of twice the standard deviation of the calculated value.