Adverse effects of increased body weight on quantitative measures of mammographic image quality

OBJECTIVE. The purpose of our study was to show that compressed breast thic kness on mammograms in overweight and obese women exceeds the thickness in normal-weight women and that increased thickness results in image degradati on. SUBJECTS AND METHODS. Three hundred consecutive routine mammograms were rev iewed. Patients were categorized according to body mass index. Compression thickness, compressive force, kilovoltage, and milliampere-seconds were rec orded. Geometric unsharpness and contrast degradation were calculated for e ach body mass index category. RESULTS. Body mass index categories were lean (3%), normal (36%), overweigh t (36%), and obese (25%). Body mass index was directly correlated with comp ressed thickness. In the mediolateral oblique view, the mean thickness of t he obese category exceeded normal thickness by 18 mm (p < 0.01), correspond ing to a 32% increase in geometric unsharpness. Mean obese thickness exceed ed lean thickness by 33 mm (p < 0.01), corresponding to a 79% increase in u nsharpness. Similar trends were observed for the craniocaudal view. In the mediolateral oblique projection, there was an increase of 1.0 kVp (p < 0.01 ) for obese compared with normal and 1.7 kVp (p < 0.01) between lean and ob ese, corresponding, respectively, to a 16% and a 25% decrease in image cont rast because of scatter and kilovoltage changes. Milliampere-seconds increa sed by 47% on the mediolateral oblique images in the obese category compare d with normal body mass index. CONCLUSION. An increased body mass index was associated with greater compre ssed breast thickness, resulting in increased geometric unsharpness, decrea sed image contrast, and greater potential for motion unsharpness.