Mathematical phantoms representing children of various ages for use in estimates of internal dose

Abstract

In the mid-1960's, Fisher and Snyder developed a mathematical phantom of an adult human for use in internal dose estimations in conjunction with a Monte Carlo transport code for photons. Simple equations defining the boundaries of the body and the principal organs were given for this phantom. To estimate dose in children, Snyder and co-workers employed phantoms that were transformations of the adult phantom. Equations for major body sections were given explicitly, with the internal organs defined implicitly through similitude transformation equations. The major shortcoming of these derivative phantoms was that the organ sizes and bone marrow distributions were not always realistic. To overcome this shortcoming, a series of distinct phantoms representing children of ages 0, 1, 5, 10, and 15 years has been developed. All equations for boundaries of organs are explicitly defined with realistic sizes. In addition, the regional distributions of hematopoietically active bone marrow and inactive fatty marrow have been assigned for each phantom, using the method of Cristy. Because detailed anatomical data for organ shapes and locations are not available for children, the ''Similitude Rule'' was used to determine the shape and the location of most of the organs. This rule is consistent with drawings depicting developmental trends of organs in the trunk. Known exceptions to the rule were adjusted appropriately. The organ volumes were assigned such that organ masses at the various ages conform closely with the data presented in International Commission on Radiological Protection Publication 23. 41 refs., 33 figs.

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