Causal factors and potential clinical implications of variation in mammographic density assessment

The thesis explores various measures of MBD assessment in digital mammography (DM) and assesses inter-­‐reader variability using BI-­‐RADS® and RANZCR scales based on four studies. Methods: In studies 1 and 2, 40 images from 20 US women—acquired one year apart—were processed using Volpara®densityTM software. Observers (20 experts) assessed the images using BI-­‐RADS®. Study 1 used spearman’s correlation (ρ) to examine relationships between the systems for BI-­‐RADS®, VDG, and AvBD%. Study 2 examined inter-­‐observer agreement using BI-­‐RADS® 4-­‐point and binary scales. In study 3, 26 Australian radiologists assessed 40 images using RANZCR synoptic scales. Agreement on RANZCR scales between radiologists was expressed as Cohen’s Kappa (κ). Study 4 used a weighted Kappa (κw) statistic to test for agreement between MBD assessment schemes and pairs of observers based on BI-­‐RADS® scores from 20 ABR examiners, 24 UK practitioners, and RANZCR radiologists. Results: In study 1, both BI-­‐RADS® (ρ=0.904; p<0.001) and Volpara (ρ=0.978; p