When a radiologist is presented with a medical image, be it a radiograph or the many hundreds of images generated from a computerized tomography (CT) or magnetic resonance imaging (MRI) [Page 120]scanner, he or she needs to make sense of the images, which are representations of the human body, and perceive pathology among the different ambiguous shapes, shades, and contours. Abnormalities are generally perceived quickly, as eye tracking has demonstrated, with pathology usually looked at within the first two or three fixations. It takes many cases and years of training to become proficient in interpreting medical images as perceptual discrimination is learned and acquired knowledge is converted into a variety of cognitive strategies and cognitive skills. This process is still not fully understood, but it ...