Skeletal Scintigraphy: General Considerations

Abstract

Skeletal scintigraphy provides a functional image of bone. It is a highly sensitive method that depicts early changes in bone flow and turnover. Because of this high sensitivity, skeletal scintigraphy allows early diagnosis of disease often days or weeks before disease can be visualized on anatomic imaging. Therefore, skeletal scintigraphy assists in establishing early treatment and hopefully achieving better patient outcomes. However, as with other nuclear medicine imaging procedures, this high sensitivity is generally accompanied by a low level of specificity. Information about early changes in blood flow and bone turnover cannot be obtained, or not easily obtained, by other imaging methods. Although the spatial resolution of bone scintigraphy is relatively low compared to anatomic imaging, one can say that its functional resolution is very high. Skeletal development and remodeling are integral parts of the physiology of bone. As the patient grows and develops, bone undergoes constant remodeling. Immature bone (woven bone) is replaced by mature lamellar bone. A skeletal scintigram can be considered not just as a static image but also as a “snapshot” of an ongoing dynamic process. As such, the bone scan can be thought of as a “slow dynamic” study. Approximately 10 % of the entire adult skeleton is replaced every year. Remodeling is a functional adaptation of bone to the forces or stresses of daily life. When interpreting pediatric skeletal scintigraphy, it is important to keep in mind the characteristic patterns of pediatric skeletal growth and development and learn to recognize these patterns so they can be distinguished from actual lesions. The distribution of bone-seeking radiopharmaceuticals varies with age and with the activity of growth centers.