Monte Carlo simulation studies of backscatter factors in mammography.

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Abstract
Experimentally determined backscatter factors in mammography can contain significant systematic errors due to the energy response, dimensions and location of the dosimeter used. In this study, the Monte Carlo method was applied to simulate photon scattering in tissue-equivalent media and to determine backscatter factors without the interference of a detector. The physical processes of measuring backscatter factors with a lithium fluoride thermoluminescent dosimeter (TLD) and an ideal tissue-equivalent detector were also simulated. Computed results were compared with the true backscatter factors and with measured values reported by other investigators. The TLD method underestimated backscatter factors in mammography by as much as 10% at high energies with TLD-100 (3.2 .times. 3.2 .times. 0.89 mm3) crystals.