Simple Radiography of the Soft Tissues

The radiologist should be aware of various normal or near-normal appearances caused by the soft tissues, which can give rise to diagnostic errors at simple radiography. Perhaps the best known of these is the crescentic shadow caused by thepinna on a lateral radiograph of the skull. Loose folds of skin are commonly present on the skulls of neonates and are readily seen on radiographs. Similarly,electrode jelly from electroencephalograms and sebaceous cysts (Fig. 22.1) on the skull may produce confusing shadows. Hair is sometimes visible but because of its unanatomical shape should rarely cause difficulty in diagnosis (Fig. 22.2). In the chest, nipple shadows are a common source of confusion as may be other skin nodules, such as neurofibromas. These may be readily confused with intrathoracic lesions. Confusing shadows may sometimes be caused by hair overhanging a lung apex and this may even simulate a cavity. In the abdomen, confusion may be caused by the shadow cast by a colostomy lip (Fig. 22.3) and in the pelvis the penis may cause confusion.