A superscan is an imaging appearance on a Tc-99m diphosphonate bone scan which occurs as a result of a high ratio of bone to soft tissue tracer accumulation. Intense osteoblastic activity in the bones causes diminished renal and background soft tissue uptake.
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Pathology
Etiology
This appearance can result from a range of causes:
- diffuse metastatic disease
- prostatic carcinoma
- breast cancer
- transitional cell carcinoma (TCC)
- multiple myeloma (some difference in opinion)
-
lymphoma
- patchy uptake nonetheless: look at skull and ribs
- tends to somewhat spare the distal skeleton
- metabolic bone diseases
- renal osteodystrophy
- hyperparathyroidism 1 (often secondary hyperparathyroidism)
-
osteomalacia
- will involve distal skeleton
- smoother uptake
- myelofibrosis/myelosclerosis
- mastocytosis
- widespread Paget disease
Radiographic appearance
A metastatic superscan tends to have uptake throughout the axial skeleton and proximal appendicular skeleton, often somewhat heterogeneous. In contrast, a metabolic superscan tends to be more uniform and involve both the axial and more peripheral skeleton, including the distal extremities, calvarium, and mandible.
Little/no activity is seen within the urinary tract or soft tissues, as most of the tracer is concentrated within the bones.