Advantages of SPECT in technetium-99m-sestamibi parathyroid scintigraphy.

Unlabelled: We demonstrate several advantages of SPECT in parathyroid scintigraphy.
Methods: Forty-four parathyroid 99mTc-MIBI scintigrams were obtained before surgery in 43 patients suffering from hyperparathyroidism. For each patient, we obtained dynamic views and planar and SPECT images of the neck and thorax. For 15 patients, we also acquired a delayed static view of the neck 2 hr after tracer injection. Abnormal thyroid-area glands were detected with factor analysis of dynamic structure (FADS) of the initial dynamic acquisition. In the 15 patients with delayed views of the neck, we compared FADS and the double-phase study results to detect glands in the thyroid uptake area. Glands outside the thyroid area were demonstrated on planar views. The location of enlarged glands was more precisely defined on the tomographic slices. The anatomic and histologic findings and the evolution of hypercalcemia after surgery were taken as reference.
Results: Sixty-four abnormal glands were found during surgery, including 39 observed in patients who underwent reoperation for persistent or recurrent hyperparathyroidism. Twenty-two of these glands were in an abnormal location, including 10 in the mediastinum. SPECT allowed the detection of three glands not demonstrated on planar views or FADS. Fifty-eight glands were correctly localized scintigraphically, including 34 in patients who underwent reoperation. Therefore, SPECT raised the sensitivity from 86% to 90.5% and from 79.5% to 87% in the reoperated patients. Tracer uptake in the low mediastinal area was better analyzed on tomographic slices than on planar views. Only seven false-positive results were depicted by planar views or FADS; none were depicted on SPECT.
Conclusion: A combination of FADS and SPECT permits detection of small glands, even in a posterior location, inside or outside the thyroid area. This scintigraphic method enables the surgeon to define more precisely details about the location of the enlarged gland and contributes to improved parathyroid surgery.