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Computational human phantom
Computational human phantoms are models of the human body used in computerized analysis. Since the 1960s, the radiological science community has developed and applied these models for ionizing radiation dosimetry studies. These models have become increasingly accurate with respect to the internal structure of the human body. As computing evolved, so did the phantoms. Graduating from phantoms based on simple quadratic equations to voxelized phantoms, which were based on actual medical images of the human body, was a major step. The newest models are based on more advanced mathematics, such as Non-uniform rational B-spline (NURBS) and polygon meshes, which allow for 4-D phantoms where simulations can take place not only 3-dimensional space but in time as well. Phantoms have been developed for a wide variety of humans, from children to adolescents to adults, male and female, as well as pregnant women. With such a variety of phantoms, many kinds of simulations can be run, from dose received from medical imaging procedures to nuclear medicine. Over the years, the results of these simulations have created an assortment of standards that have been adopted in the International Commission on Radiological Protection (ICRP) recommendations.〔Xu, X.G.; Eckerman, K.F. Handbook of Anatomical Models for Radiation Dosimetry. Taylor & Francis, 2010. ISBN 978-1-4200-5979-3.〕
==Stylized (first-generation) computational phantoms==
The very first generation computational phantoms were developed to address the need to better assess organ doses from internally deposited radioactive materials in workers and patients. Until the late 1950s, the ICRP still used very simple models.〔ICRP. Report of Committee II on Permissible Dose for Internal Radiation International Commission on
Radiological Protection (Oxford: Pergamon Press), 1959.〕 In these calculations, each organ of the body was assumed to be represented as a sphere with an "effective radius". The radionuclide of interest was assumed to be located at the center of the sphere and the "effective absorbed energy" was calculated for each organ. Phantoms such as the Shepp-Logan Phantom were used as models of a human head in the development and testing of image reconstruction algorithms. However, scientists attempted to model individual organs of the body and ultimately the entire human body in a realistic manner, the efforts of which led to stylized anthropomorphic phantoms that resemble the human anatomy.
In general, stylized computational phantom is a mathematical representation of the human body which, when coupled with a Monte Carlo radiation transport computer code, can be used to track the radiation interactions and energy deposition in the body. The feature of stylized computational phantom is finely tuned by adjusting individual parameters of the mathematical equations, which describes the volume, position, and shape of individual organs. Stylized computational phantom has a long history of development through the 1960s to 1980s.
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