Normal and abnormal extraosseous uptake of 99Tcm-MDP on bone scintigraphy

The kidney, ureter, bladder and mammary gland are the extraosseous soft tissues that are normally visible on bone scintigraphy. If abnormal soft tissue activities are observed on bone scintigraphy, the possibility that such abnormal activities are caused by the human factor or the quality problem of the skeletal imaging agent should first be precluded. Enhancing the quality control of the skeletal imaging agent and specifying the technical procedure of bone scintigraphy are the important means for reducing and avoiding technical artifacts. If an abnormal concentration of the skeletal imaging agent in soft tissues and organs is caused by the pathologic factor of a patient himself, it may be concerned with a malignant disease in most cases. The malignant tumor of liver, lung and mammary gland is the most frequent pathologic reason for soft tissue accumulation on bone scintigraphy. However, soft tissue accumulation can also be seen in other tumors occasionally. On the other hand, the diffuse abnormal activity in intracavity may be concerned with malignant injury in the pleura of chest and abdomen, and pleural and ascitic fluids. Extraosseous tracer uptake can also be found in benign lesions such as benign tumor, pus, inflammation, wounds, calcification, radiation damage and amyloidosis. Because the abnormal tracer agent concentration in the soft tissue can often provide valuable clinical information, the film must be read with care in conjunction with clinical data and other examinations. (authors)