Abstract: A surgeon utilizes a brain scan image to locate a brain lesion and to plan the operation to treat it. Distance measurements representing the location of the lesion are derived from various views of a brain scan image. In the operating room, he transfers these distance measurements onto the patient's cranium in a “warped” or curvilinear Cartesian coordinate system defined by intersecting orthogonal lines extending along the surface of the patient's cranium. As a result, the lesion is localized and the surgeon may establish the appropriate location and orientation of a bone flap to be used to access the lesion.