Computer-based collection of mammographic exposure data for quality assurance and dosimetry

PURPOSE: There is potentially more. to quality assurance in mammography tha n the MQSA mandated tests. In this paper we describe a method of capturing individual mammogram technical parameters and the creation of new measures. These include the numbers of images required for each screening examinatio n by technologist, median compression by technologist, and the radiation do se of the examination to the general population of patients. METHOD/MATERIA LS: With this method we describe a semiautomated method of the collection o f technical data from mammography exposures. The data that are automaticall y created by the mammography unit are saved on a computer for later analysi s. The method was used on 2738 consecutive screening mammography examinatio ns and 13621 exposures from one machine. Data were obtained from November 1 998 through December 1999. RESULTS: Using standard methods, the mean glandu lar dose (MGD) per exposure was 2.62 mGy (SD 1.2). The mean dose per bilate ral screening examination was 6.53 mGy (SD 3.07), the median dose was 6.11 mGy, and the dose range was 1.13-34.23 mGy. Rhodium filtration was used for 18% of the exposures. The average and median breast thickness was 4.9 cm. The ACR phantom MGD for this machine was 2.44 mGy at 25 kVp, and 1.97 mGy a t 26 kVp. The mean number of exposures for a bilateral mammogram was 4.9, a nd varied by a technologist from 4.7 to 5.2. The mean compression pressure varied by technologist from 13 to 30 lbs (58-134 N). CONCLUSIONS: The mean dose per mammogram is slightly greater than the ACR phantom dose at 25 kVp. Almost five exposures were necessary for a standard bilateral examination, and this varied by technologist. The compression used also varied by techn ologist. The semiautomated collection of technical data can aid in maintain ing an effective mammography QA program. (C) 2001 American Association of P hysicists in Medicine.