Monte Carlo Calculation for Estimation of the High-Accuracy Average Glandular Dose in Mammography

Abstract

As the glandular tissues within the female breast carry the greatest risk of radiation damage, the high-accuracy average dose received by these tissues in X-ray examination should be estimated. Because it is difficult to measure the average glandular dose received by the breast directly, we calculated conversion factors to obtain the average glandular dose from exposure in air by the following procedures.
The method was useful in some specific applications, allowing calculation of the high-accuracy glandular dose. First, we measured X-ray energy spectra from a molybdenum target with a molybdenum filter and from a rhodium target with a rhodium filter at several tube voltages using a high-purity germanium semiconductor radiation detector. We then calculated the exposure per fluence using the X-ray energy spectrum data, and computed the average glandular dose per photon in a semi-elliptical cylindrical breast model using the Monte Carlo method. Finally, we calculated the conversion factors from these numerical data. It was possible to calculate the average glandular dose with exposure in air. We conclude that the X-ray energy spectrum is important for calculating the average glandular dose rather than the half-value layer.