Quality Control Programme On Mammography Systems In The Republic Of Benin: Assessment Of Patients Dose Optimisation In Three Selected Facilities

ABSTRACT The Mean Glandular Dose (MGD) was estimated first using Polymethylmethacrylate (PMMA) slabs and secondly MGD was estimated per right craniocaudal (RCC) projection view and left craniocaudal (LCC) projection view. A number of 21 patients out of a total of 28 patients, undergoing breast examination in three (3) selected mammography facilities in the Republic of Benin were involved. Image quality was evaluated based on subjective analysis of images with Leeds Tests Objects and American College Radiology Mammography Accreditation Phantom (ACR MAP). Quality control (QC) tests were performed to verify if the mammography machines selected for the study were working within acceptable level of performance using International Atomic Energy Agency Human Health Series (IAEA HHS) No.2 and No.17 protocols. The QC tests showed that the mammography units were working within the acceptable performance level. For the phantom study MGD estimation for all selected mammography systems, the calculated MGD values were below the recommended values, under manual mode as well as the automatic exposure mode. From the comparison of MGD under automatic exposure control (AEC) mode and MGD under manual mode, it was observed that the difference was high. MGD under AEC mode was less than MGD under manual mode and the difference was 1.05 mGy and 1.31 mGy respectively from two (2) mammography units, namely CAR and CHUD/OP. Data collected from a total of 21 patients was used for MGD calculation. The estimated MGD of patient within the age range of [50 - 64] years with a compressed breast thickness (CBT) of 20 mm for RCC view and 18.7 mm for LCC view reported iii a dose of 1.10 mGy, which was slightly high compared to the recommended MGD value for CBT of 21 mm which was 1 mGy. All the remaining estimated MGD was within the recommended international levels of IAEA HHS No.17 protocol. The dose delivered by the selected mammography units were within the acceptable levels of IAEA HHS No.17 for both exposure modes. Thus the AEC mode is recommended because it delivers less MGD and this will help to achieve optimization of patient dose in mammography practices.