Nuclear medicine studies in metabolic bone disease.

The principal application of nuclear medicine in metabolic bone disease is the isotope bone scan. Often, it is not a diagnostic tool but can be useful in clarifying the nature of a clinical problem. The best-established role for the bone scan in metabolic bone disease is in Paget's disease, in which it is diagnostic, provides definition of the extent of disease, and probably reflects disease activity. The isotope bone scan is also important in osteoporosis, for which it is not diagnostic but may often provide useful information to confirm that fracture has occurred, determine the age of the fracture, identify unsuspected fractures, and identify other causes for pain, for example, facet joint disease. The bone scan is less useful in other metabolic bone diseases, for example, renal osteodystrophy and osteomalacia, but will often have a characteristic appearance, with several metabolic features. The degree of positivity of the scan generally relates to the severity of the hyperparathyroidism. In patients with metabolic bone disease, other specific clinical problems may arise, such as osteomyelitis or avascular necrosis, and the bone scan may be diagnostic in these conditions. Nuclear medicine techniques are also of value in hyperparathyroidism and to localize the site of the adenoma where surgical treatment is being considered; the use of technetium Tc 99m sestamibi is now routine. More recently, positron emission tomography (PET) scanning has been found to be helpful in the more difficult cases.