Lesion detection in digital mammograms

Detection of mass lesions in mammograms is essentially limited by image variation due to normal patient structure, which has an average power-spectrum of the form `1/f3'. Image noise plays little role in limiting mass detection. The contrast-detail (CD) diagram for lesion detection in mammographic structure is novel, for both human and model observers. Contrast thresholds increase with increasing signal size for signals larger than about 1 mm, with CD slopes of about 0.3 for humans and 0.4 for model observers. Similar results were obtained in search experiments. The work was done using hybrid images, with of tumor masses (extracted from specimen radiographs) added to digitized mammographic backgrounds. We have been able to explain the results using a number of observer models. These results demonstrate that CD diagrams based on image noise-limited detection with simple phantoms are not useful for evaluation of mass detection in mammograms--so more realistic approaches are necessary in order to model mammographic imaging systems for optimization.