Segmentation and Feature Extraction Techniques, with Applications to MRI Head Studies

To obtain a three‐dimensional reconstruction of the hippocampus from a volumetric MRI head study, it is necessary to separate that structure not only from the surrounding white matter, but also from contiguous areas of gray matter–the amygdala and cerebral cortex. At present it is necessary for a physician to manually segment the hippocampus on each slice of the volume to obtain such a reconstruction. This process is time consuming, and is subject to inter‐ and intra‐operator variation as well as large discontinuities between slices. We propose a novel technique, making use of a combination of gray scale and edge‐detection algorithms and some a priori knowledge, by which a computer may make an unsupervised identification of a given structure through a series of contiguous images. This technique is applicable even if the structure includes so‐called false contours or missing contours. Applications include three‐dimensional reconstruction of difficult‐to‐segment regions of the brain, and volumetric measurements of structures from series of two‐dimensional images.