Digital Mammography Breast Dosimetry Using Copper-Doped Lithium Fluoride (LiF:MCP) Thermoluminescent Dosimeters (TLDs)

摘要

The determination of mean glandular dose (MGD) to the breast is an essential aspect of mammography equipment evaluations and exposure controls. The American College of Radiology (ACR) Quality Control Manual outlines the procedure for MGD determination in screen-film mammography based upon conversions of entrance skin exposures (ESEs) measured with an ionization chamber (IC). The use of digital mammography has increased because of the need for improved object resolution and tissue contrast. Digital mammography incorporates a different image receptor (solid-state detector), which may lead to different MGDs compared to screen-film mammography. Therefore, evaluating and verifying the applicability of the ACRs MGD methodology to digital mammography is essential in determining the carcinogenic risk associated with digital mammograms. This research measured the applicability and accuracy of the ACRs MGD methodology to digital mammography. MGD measurements were determined using the light output from TLD-100H (LiF:MCP) TLDs and conversions of ESEs measured with an IC (ACR methodology). The statistical evaluation of the MGD data revealed the ACR s MGD methodology is not applicable to the imaging modality of digital mammography (all P values <0.05). The comparison of the TLD and IC MGD calculations resulted in a measured MGD differential no greater than 0.12 mGy. Additionally, a more rigorous method of MGD was calculated by averaging the thermoluminescent (TL) absorbed dose at various depths throughout a breast phantom. This more through method of calculating MGD resulted in a MGD of 1.34 mGy 0.07 +/- mGy as compared to the ACR s methodology MGD of 1.34 mGy +/- 0.001 mGy.