The problems of certainty and naming; general principles of diagnosis and diagnostic imaging; concise descriptions and comparisons of the modalities; the radiation risk question; risks in diagnostic imaging; imaging by chief complaint, signs, symptoms, or conditions; imaging by abnormal laboratory findings; further imaging strategy given an abnormal imaging study; cancer diagnosis and the metastatic "Work-Up"; imaging in HIV/AIDS; imaging in patients with poor prognoses, nursing home patients, and the terminally ill; reprise and reflections on the methods and purposes of medical diagnosis.