The Crescent Pattern of Increased Radioactivity in Brain Scanning

Several reports have appeared recently concerning the application of brain scans in the evaluation of non-neoplastic cranial or intracranial disease (1–4). One of the patterns of abnormal radionuclide distribution considered specific for subdural hematoma was a crescent-shaped area of increased activity seen along the outer margin of the scan in either the anterior or posterior projection, less well denned in the lateral view (5, 6). As our experience in brain scanning increased, we found this pattern in a variety of pathophysiologic conditions other than subdural hematoma. This communication reports our experience to date with the crescent pattern of increased radioactivity in brain scanning. Material and Methods Since September 1964 we have employed pertechnetate 99m for brain scanning in a dose of 65 µCi per pound (7, 8). Nuclear Chicago Pho-Dot radioisotope scanners with a 3 × 2-in. sodium iodide (thallium-activated) crystal, operated at scanning speeds of 90 to 190 cm per minute, line spacing of 0.5 ...