99mTc MIBI whole body scan in evaluating metabolic bone disease.

Objectives Metabolic bone disease due to hyperparathyroidism is characterized by increased bone resorption and new bone formation. 99mTc- hexakis-2-methoxyisobutylisonitrile (99mTc MIBI) accumulation is controlled by metabolic function and cell viability. Few case reports showed increased bone uptake in cases of hyperparathyroidism. The aim of this study was to investigate, for the first time, the potential of whole body 99mTc MIBI for detecting, visually and with the aid of quantitative analysis, bony changes associated with hyperparathyroidism.

Methods Eighty six patients with hyperparathyroidism, referred routinely for parathyroid localization, were included in this case-control prospective study. Each patient was injected with 20-25 mCi of 99mTc MIBI. Routine anterior cervico-thoracic, including the neck and upper two thirds of mediastinum up to the arch of aorta, images were obtained for the parathyroid localization. Two extra whole body images were acquired and assessed visually. Regions of interest over the mandible, sternum, femur, humuri, spine and the soft tissue adjacent to the bone were drawn. The ratios of bone to soft tissue were calculated and compared to ratios drawn in a control group routinely referred for cardiac imaging and injected with 99mTc MIBI, after confirming the absence of any bone disease.

Results The visual interpretation of the scans showed forty nine patients to have increased bone uptake in multiple skeletal areas. The quantitative assessment showed significant difference between the mean ratios of femurs, humuri, sternum and spine of the case and control groups. Kruskal-Wallis test showed significant agreement between the visual and quantitative ratios drawn from right and left femur and left humurus (P<0 .05).

Conclusions 99mTc MIBI whole body imaging is a potentially useful technique for assessing metabolic bone disease associated with hyperparathyroidism. Quantitative analysis can help confirm the visual scan findings