Interactive Image Segmentation for Radiation Treatment Planning

COVIRA (COmputer VIsion in RAdiology) is a project in the European Community's Advanced Informatics in Medicine program. The goal is to improve the diagnosis and planning of treatment (radiotherapy) for patients with brain tumors and other diseases. The aim of radiotherapy is to provide a high dose of radiation to a tumor while sparing as much as possible of the surrounding healthy tissue. A necessary first step is defining the target volume and organs at risk by manually outlining the required contours on magnetic resonance or computed tomography scans. For a full three-dimensional plan this is time-consuming, as 40 or more scans are used. Computer image segmentation speeds up the process, and a method that combines information from edge and region detectors is described. Since this method is not able to completely meet the clinical requirements, an interactive image segmentation algorithm has been developed that enables the operator to employ clinical judgment. Probabilities are assigned to edges and regions and presented to the user as a hierarchy of segmentations. The approach is being subjected to extensive clinical evaluation, using pilot applications running on IBM RISC System/6000 workstations.