Objective and subjective assessment of mammographic positioning quality

Early detection of breast cancer through mammographic screening can only be achieved with high quality mammograms. In this study an experienced radiologist and radiographer scored 127 mammographic screening exams with MLO and CC views of left and right breasts using 18 different positioning quality criteria. This subjective evaluation of the positioning quality was compared to the objective and automatic assessment by Volpara TruPGMI (Volpara Health, New Zealand). The quality criteria on missed tissue at medial or lateral side of the breast were in agreement with the software for the radiographer but was scored differently by the radiologist. The criterion on the nipple in profile showed good agreement between the readers and the software. The important criterion on the number of images that had to be repeated showed that even though the same amount of cases was rated to be repeated, the majority of the cases were discordant between radiologist and software, the agreement with the radiographer was better. The presence of folds in the pectoral muscle, the adequate depiction of the pectoral muscle and inframammary angle on MLO view showed an acceptable agreement between the readers and software. Finally, the overall positioning quality was rated as Perfect, Good, Moderate or Inadequate. The extreme ratings of Perfect and Inadequate showed high agreement between readers and software. However the number of intermediate ratings “Moderate” and “Good” were very different. For the readers the majority of the images was “Good” whereas the software scored most often “Moderate”. Subjective positioning quality monitoring is prone to high reader variability; this can be overcome via the use of automatic measurements with software. Nevertheless, prior to the use of automatic quality monitoring software in clinical practice, a careful evaluation and validation is needed.