Automatic algorithm for registering digital images of multiple skin lesions

Malignant melanoma rates are rising rapidly in white populations. Early detection, primarily through observation of new or changing pigmented skin lesions, is crucial for patient survival. Unfortunately these changes are difficult to detect on high-risk patients who have large number of lesions. Photographic records could be invaluable in these cases, but images must first be "registered" to remove distortions introduced by varying camera angles and subject postures. This paper describes a computer algorithm for registering pairs of digital images of multiple skin lesions automatically. The algorithm comprises four steps: (1) locate and label the lesions within each image; (2) identify matching lesions based on local spatial relationships; (3) test and refine lesion matches based on global spatial relationships; and (4) transform one image. Results are presented of the algorithm's performance on images of both simulated and actual skin lesions. The findings demonstrate that registration is successful under realistic imaging conditions. Keywords: image registration, skin lesions, melanoma, matching, point pattern