Computational models of human anatomy are mathematical representations of human anatomy designed to be used in dosimetry calculations. They have been used in dosimetry calculations for radiography, radiotherapy, nuclear medicine, radiation protection and to investigate the effects of low frequency electromagnetic fields. Tomographic medical imaging techniques have allowed the construction of digital three-dimensional computational models based on the actual anatomy of individual humans. These are called voxel models, tomographic models or phantoms. Their usefulness lies in their faithful representation of human anatomy and the flexibility they afford by being able to be scaled in size to match the required human dimensions. Segmenting medical images in order to make voxel models is very time-consuming so semi-automatic segmentation techniques are being developed. Some 21 whole or partial body models currently exist and more are being prepared. These models are listed and discussed.

Fifty-four consecutive CT scans have been used to construct a tomographic computational model of a 14-year-old female torso suitable for the determination of organ doses from CT. The model, known as ADELAIDE, is in the form of an input file compatible with user codes based on XYZDOS.MOR from the readily available EGS4 Monte Carlo radiation transport code. ADELAIDE's dimensions are close to the Australian averages for her age so the model is representative of a 14-year-old girl. The realistic anatomy in the model differs considerably from that in Cristy's 15-year-old mathematical computational model by having realistically shaped organs that are appropriately located within a real external contour. Average absorbed dose to organs from simulated CT examinations of the chest and abdomen have been calculated for ADELAIDE using EGS4 within a geometry specific to the General Electric Hi-Speed Advantage CT scanner and using an x-ray spectrum calculated using data from the scanner's x-ray tube. The simulations include the scanner's beam shaping filter and patient table. It is suggested that the resulting values have fewer possible sources of uncertainty than organ doses derived from dose coefficients calculated for a MIRD style model with mathematical anatomy and a spectrum that may not match that of the scanner. The organ doses were normalized using the scanner's CTDI measured free-in-air and an EGS4 simulation of the CTDI measurement. Effective dose to the torso from 26-slice chest and 24-slice abdomen examinations (at 120 kV, 200 mAs, 7 mm slices) is 4.6 +/- 0.1 mSv and 4.3 +/- 0.1 mSv respectively.

A number of computer codes, developed using semi-empirical models, are available to compute x-ray spectra from a tungsten target for different tube parameters. In this study x-ray spectra measured with a high-purity germanium detector are compared with those computed using the empirical models and previously published measured data. The computer codes used to generate the spectra are based on models proposed by Birch et al. and Tucker et al. The measured x-ray spectra agreed well with the computed x-ray spectra using the model of Tucker et al. whereas the model of Birch et al. produced a "harder" x-ray spectrum compared to the measured spectra. Our measured x-ray spectra compared well with the previously published measured spectral data of Fewell et al.