Phantoms anthropomorphic

The principal data available to determine or E directly from ifpdO) are conversion coefficients which give the quotient of or E and /fp(lO) [i.e., He/[Hp(10)1 or /[ifp(10)]). The unit for each of the three quantities is Sv therefore, these conversion coefficients are dimensionless. Such conversion coefficients have been derived from calculations for a number of idealized conditions for irradiation by monoenergetic photons of mathematically described reference adult anthropomorphic phantoms. The conversion coefficients are a function of photon energy, photon beam direction, surface of the phantom on which the radiation is incident, and location where //p(lO) is being evaluated on the phantom. 

These analyses require that the 10) values for normal incidence be modified for irradiation geometries where the field is incident other than perpendicular to the surface of the personal monitor. The methods used in developing these modifications to fl pdO) for nonnormal incidence included extensive Monte Carlo calculations of photon interactions in anthropomorphic phantoms (Xu, 1994) or in PMMA and tissue slabs and the ICRU sphere (Grosswendt, 1991 Grosswendt and Hohlfeld, 1982), and thermoluminescent dosimeter measurements in water cubes (Lakshmanan et al., 1991). Some of these modifications for /fp(lO) are presented in ICRU (1992). 

Xu (1994) explored three photon energies (i.e., 80 keV, 300 keV and 1 MeV) and a number of irradiation geometries, including geometries with a large range of non-normal incidence. In particular, Xu (1994) provided (estimate) values for a variety of point sources at various locations and distances from the body. Xu (1994) computed the/fpdO) values in tissue-equivalent spheres located on the relevant surface of the anthropomorphic phantom. 

ICRU and ICRP have a joint effort underway to review and present values of E for Monte Carlo calculations in anthropomorphic phantoms, but that work is not yet published. When the data are published, a similar evaluation of the use of Hp(10) values determined from two personal monitors to estimate E will be possible. 

Wessling J, Fischbach R, Meier N et al. (2003) CT colonography protocol optimization with multi detector row CT - study in an anthropomorphic colon phantom. Radiology 228 753-759... 

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