Diagnostic Reference Levels (DRLs) and Image Quality Evaluation for Digital Mammography in a Nigerian Facility

Abstract

Diagnostic Reference Levels (DRLs) for digital mammography and image quality evaluation are important optimization tools in medical imaging. High quality mammograms are essential to the successful early detection of breast cancer. The objective of the study is to establish DRLs for digital mammography and to assess image quality of the mammograms for optimization. DRLs were established using thermoluminescent dosimeter (TLD) chips to estimate the mean glandular dose for both cranio-caudal and medio-lateral oblique projections. The TLD chips were calibrated. The DRLs were set at the 75th percentile of the distribution of the median value of mean glandular dose. Image quality was assessed using European Commission guideline for mammographic image quality assessment. Results for DRLs were 0.53 mGy for cranio-caudal and also 0.53 mGy for medio-lateral oblique. Image quality evaluation showed criteria scores for cranio-caudal and medio-lateral oblique projections as 76 % and 61.2 % respectively. The mammograms scored the highest and lowest score of 100 % and 44 % on criteria 2 and criteria 6 (absence of skin fold) respectively for cranio-caudal projections while for the mediolateral oblique projections, criteria 1 (all breast tissue clearly shown) and criteria 5 (inframammary angle clearly demonstrated) have the highest and lowest score of 96 % and 8 % respectively. The study showed that the DRLs in this study was lower than the established values in other regions of Nigeria and international established values. Image quality was within acceptable level. DRLs for digital mammography and image quality evaluation are important optimization tool that should be adopted by every radiology department with mammography unit.