TC99M-sestamibi scintigraphy as an imaging procedure in the preoperative evaluation of hyper-parathyroidism: a comparison with other imaging modalities

ABSTRACT

The present study was a prospective clinical study conducted over 4 years from 1996 till 1999 inclusive at KFSH-Kingdom Saudi Arabia to investigate the utility of Tc99m-sestamibi scintigraphy as an imaging tool in the preoperative localization of abnormal glands in cases with hyperparathyroidism. Comparison was also made between this procedure and other imaging procedures in terms of sensitivity and specificity with emphasis on the surgical success and postoperative cure rate. The study included 25 patients, 21 had primary hyper-parathyroidism and 3 had a secondary disease due to associated chronic renal failure. Eighteen were females and 7 were males with a mean age of 44 +/- 28 and a range of 16 to76 years. The mean serum calcium level of the whole group was high [2.81 +/- 0.29] ranging between 2.57 to 3.45 mmol/L while mean serum phosphate level was low 1.62 +/- 0.72 and range of 0.41 to 3.21 mmol/L. The serum parathormon level was also high, it ranges between 8.6 to 34.3 pmol/L with a mean value of 19.8 +/- 10.8. Preoperative imaging evaluation was carried out by scintigraphic detection of pathological parathyroid glands using Tc-sestamibi as a radiotracer for all the patients together with US, CT, MRI and TI/Tc subtraction imaging procedures. All the patients were considered for surgical treatment and confirmation of scans findings was obtained. Tc99m-sestamibi scintigraphy correctly localized 2o out of 21 adenomas with a sensitivity of 96% markedly higher than that obtained with other Imaging techniques [US- 76%, CT- 62%, MRI- 81% and TI/Tc-subtraction scintigraphy 72%]. Tc99m-sestamibi and MRI were the only procedures able to diagnose two of the 3 cases identified surgically as hyperplasia, whereas Tc99m-sestamibi was the only technique able to detect the case with ectopic mediastinal gland with significant higher specificity than other procedures which was reflected on the time and success of surgical treatment. In addition, the smallest abnormal gland in diameter [0.8 cm] and weight [195 mg] were only picked up by Tc99m-sestamibi scintigraphy while missed by other techniques. Surgery was successful in all cases as assessed by normalization of the serum calcium and phosphate levels and serum parathormon level as well. In patients with hyperparathyroidism, Tc-sestamibi scintigraphy may be used as a single imaging technique as it showed a high sensitivity and specificity in the preoperative localization of pathological parathyroid especially the ectopic glands. The benefit of proper preoperative localization of the glands has no doubt a great impact on the surgical success and postoperative cure rate