A method of segmenting images receives an image (such as a medical image) and a segment in relation to the image, displays them to an observer, receives a modification to the segment from the observer, and generates a second segment in relation to a second image, responsive to the modification. An image segmentation system includes a learning scheme or model to take input from an observer feedback interface and to communicate with a means for drawing an image segment to permit adjustment of at least one image segmentation parameter (such as a threshold value). The learning scheme is provided with a knowledge base which may initially be created by processing offline images. The learning scheme may use any scheme such as a reinforcement learning agent, a fuzzy inference system or a neural network.