VisMed: A visual vocabulary approach for medical image indexing and retrieval

Voluminous medical images are generated daily. They are critical assets for medical diagnosis, research, and teaching. To facilitate automatic indexing and retrieval of large medical image databases, we propose a structured framework for designing and learning vocabularies of meaningful medical terms associated with visual appearance from image samples. These VisMed terms span a new feature space to represent medical image contents. After a multi-scale detection process, a medical image is indexed as compact spatial distributions of VisMed terms. A flexible tiling (FlexiTile) matching scheme is proposed to compare the similarity between two medical images of arbitrary aspect ratios. We evaluate the VisMed approach on the medical retrieval task of the ImageCLEF 2004 benchmark. Based on 2% of the 8725 CasImage collection, we cropped 1170 image regions to train and validate 40 VisMed terms using support vector machines. The Mean Average Precision (MAP) over 26 query topics is 0.4156, an improvement over all the automatic runs in ImageCLEF 2004.