Bone scintigraphy in Paget's disease treated with combined calcitonin and diphosphonate (EHDP)

Bone scintigraphy in metabolic bone disease

The bone scan has well-recognized appearances in metabolic bone diseases, with its main clinical value found in focal conditions or the focal complications of disease. In clinical practice, the bone scan is most widely used to detect fractures in osteoporosis and pseudofractures in osteomalacia and to evaluate Paget's disease.

Radionuclide imaging in metabolic and systemic skeletal diseases

Radionuclide imaging with Tc-99m diphosphonates is not an effective method for detecting or ruling out most osteoporotic diseases including senile osteoporosis or accelerated postmenopausal osteoporosis, and the slow loss of bone tissue generally remains undetected by this modality. Nonetheless, it frequently surpasses or supplements radiographic findings in evaluating the focal complications of metabolic bone disease, including fractures, microfractures, stress fractures, vertebral compressions, Milkman-Looser zones, aseptic necrosis, and acute infarction. In contrast to its secondary role in osteoporosis, bone imaging is of prime importance in investigating hypercalcemia, because the major cause of this abnormality is skeletal metastatic malignancy. In defective bone mineralization due to hyperparathyroidism or osteomalacia, a general increase in diphosphonate skeletal uptake is detected more frequently than radiographic abnormalities. However, normal skeletal images do not rule out metabolic bone disease. Biochemical testing is more reliable in detecting primary hyperparathyroidism. On the other hand, in renal osteodystrophy, biochemical abnormalities are variable and bone imaging is helpful in assessing the severity of skeletal involvement, but not its etiology. Many methods of quantitating the kinetics of Tc-99m diphosphonates have been explored, such as plasma clearance, bone-to-soft-tissue ratios, 24-hour total body retention and 24-hour urinary excretion. None of these have been widely accepted. The value of bone imaging is established in other systemic diseases, most notably in Paget's disease, hypertrophic pulmonary osteoarthropathy, sickle cell disease, fibrous dysplasia, and sympathetic dystrophy.

Radiological demonstration of healing in Paget's disease of bone treated with APD

Twenty-three patients with Paget's disease received the bisphosphonate APD and were examined radiologically every 6 months. Because routine roentgenographic procedures were followed, a number of the X rays were not fit for comparison. The radiographic technique, as well as the positioning of the patients, is critical since both could lead to artefacts. All patients reached normal biochemical levels, usually within 6 months. Out of the 23 patients 11 showed definite radiological improvement in one or more lesions; probable improvement was seen in another three. Of the 65 individual lesions, with films that were comparable, 30% definitely and 20% probably improved; 50% did not change but deterioration was never encountered. Osteolytic lesions in the long bones are most suitable for the evaluation of radiological changes and follow-up of these lesions during treatment should be most rewarding.

Observations on the natural history of Paget's disease

Whole-body skeletal scintigraphy was performed in 4700 adult patients from south-east Scotland. In 3831 with proven or suspected malignant disease the prevalence of osteitis deformans in males is 0.006 in those aged 15-54 years, 0.026 in the age group 55-84 years and 0.24 over the age of 84 years. The corresponding figures in females are 0.002, 0.021 and 0.15. Previous estimates of prevalence should be increased by at least 25% to take account of peripheral and monostotic disease, which is more common than hitherto recognised. The increase in prevalence with age may not be linear. Possible associations with environmental and genetic factors which would account for such a distribution are considered. It is suggested that the conventional distinction between 'active' and 'burned out' Paget's disease may be incorrect.

Correlation of skeletal uptake of 99mTc-diphosphonate and alkaline phosphatase before and after oral diphosphonate therapy in Paget's disease

In Paget's disease of bone, quantitation of skeletal uptake of radiolabeled diphosphonate has been proposed as a means of monitoring response to therapy. However, the validity of such techniques has been questioned during oral diphosphonate therapy because of possible interaction between oral and radiolabeled diphosphonate. In the present study 18 patients with Paget's disease received a 6 month course of oral diphosphonate therapy. Measurements of 24 h whole body retention (WBR) of 99mTc-labeled hydroxyethylidene diphosphonate (HEDP), serum alkaline phosphatase (SAP), and urinary hydroxyproline excretion were obtained before, during, and after treatment. WBR correlated well with SAP and urinary hydroxyproline throughout the course of therapy. In addition, the relationship between WBR and SAP was maintained after cessation of oral diphosphonate. It would thus appear that in Paget's disease 24 h WBR of HEDP, a quantitative measure of skeletal uptake of diphosphonate, will reflect disease activity even in the presence of an oral diphosphonate load.