bonescan

Bone scan, or bone scintigraphy, is a nuclear medicine imaging technique used to evaluate the metabolism and turnover of bone. A radiopharmaceutical, typically technetium-99m labeled diphosphonate such as MDP, is injected intravenously. The tracer distributes according to regional blood flow and osteoblastic activity, accumulating in areas of increased bone remodeling. After injection, images are usually obtained several hours later to allow blood pool clearance and tracer uptake. A whole-body scan is commonly followed by targeted views or single-photon emission computed tomography (SPECT) or SPECT/CT to localize abnormalities.

Indications include detection of skeletal metastases, occult or stress fractures, osteomyelitis or infection, inflammatory or degenerative arthritides, prosthetic loosening, evaluation of fever of unknown origin, metabolic bone disease, and assessment of treatment response.

Interpretation relies on identifying focal “hot” or “cold” areas relative to the surrounding bone. Increased uptake is not specific and may reflect malignancy, fracture healing, infection, arthritis, or other conditions; decreased uptake can occur in areas of poor blood flow or extensive sclerosis. Imaging findings are interpreted in conjunction with clinical history and other radiologic studies.

Advantages include high sensitivity for skeletal pathology and the ability to survey the entire skeleton in a single study. Limitations include relatively low specificity and exposure to ionizing radiation. The study may be inconclusive and may require follow-up imaging with MRI, CT, or PET/CT for anatomic localization and characterization. Pregnancy is a precaution; tracer use is generally avoided in pregnant patients.

Preparation typically involves hydration and voiding prior to scanning; there is usually no need to fast. After the exam, patients may resume normal activities.