The segmentation of the liver from the surrounding soft tissues between the ribs on a non-enhanced, arterial or delayed phase computed tomography image complicated, as the muscle and many other soft tissues have very similar X-ray attenuation to the liver, thus they manifest as similar intensity and similar pattern domains on the computed tomography images. However, if the anatomical setup of the human body and the location of the bones, that have much higher attenuation are taken into account, a sufficiently smooth and precise borderline can be drawn between the ribcage and the liver, that can be developed into a liver contour by successive erosion and active contour methods.