The urgent need for computer-assisted detection of tumors and lesions in medical images becomes clear when one considers the state of affairs in X-ray film mammography for breast cancer screening. In the United States it is estimated that there are currently more than 50 million women over the age of 40 at risk of contracting breast cancer. If only one-half of these women are screened by mammographic examination each year—and given that in the United States each breast is viewed from two angles—then the number of X-ray films that must be read by radiologists reaches the staggering total of 100 million per annum
