Early detection of cancerous changes by mammogram comparison

This paper describes an approach to mammogram analysis which detects cancerous signs by comparing newly acquired mammograms with previous screenings of the same patient. The comparison is carried out regionally between appropriate mammograms in three sequential steps: (1) mammogram registration, (2) mammogram partitioning, and (3) analysis and comparison of regional intensity statistics. The registration is established pairwise between the new mammogram and the corresponding one acquired in the previous screening. The objective of registration is to allow interpretation of the newly acquired mammograms in terms of the earlier screenings. The newly acquired mammogram is partitioned by using the hierarchical region growing technique that models relationships between pixels by the fuzzy membership function. By changing parameters of the function obtained regions are split further (when needed) to allow analysis of smaller regions. Region splitting is required in order to achieve higher sensitivity to small changes such as appearance of microcalcifications. The intensity statistics of a region in the newly acquired mammogram is compared to the intensity statistics of the corresponding region in the previous mammogram. The comparison is carried out by assuming that intensity differences in the case of cancerous changes are primarily related to higher intensities. The approach was tested on twelve cases represented by 96 mammograms. In all cases the approach performed satisfactorily.