1. A method of segmenting a target organ of the body in medical images, the method comprising: a) providing a probabilistic atlas with probabilities for a presence of the target organ at different locations relative to a bounding region of the target organ; b) providing one or more medical test images; c) for each of the one or more medical test images, identifying, at least provisionally, a location of a bounding region for the target organ in the test image; and d) for each of the one or more medical test images, using the probabilities from the probabilistic atlas to generate a segmentation mask of the target organ in the test image, with the generating being performed by a data processor.