Improving the yield of preoperative parathyroid localization: Technetium Tc 99m-sestamibi imaging after thyroid suppression

Background. Preoperative localization is essential for successful directed, minimally invasive or reoperative parathyroidectomy. Standard technetium Tc 99m-sestamibi imaging is the most sensitive modality for localization. We reviewed our experience with ^99mTc-sestamibi imaging and specifically investigated the effect of thyroid suppression on repeat imaging of patients who had initially nonlocalizing scans. Methods. The records of patients who underwent ^99mTc-sestamibi imaging during evaluation for primary hyperparathyroidism were reviewed. A subset of patients with initially nonlocalizing scans underwent thyroid suppression with either thyroxin or liothyronine and then had their scans repeated. Results. Ninety-nine patients with primary hyperparathyroidism underwent ^99mTc-sestamibi imaging followed by parathyroidectomy (initial operation, 78; reoperation, 21). Successful parathyroid localization was obtained on standard imaging in 67 patients. Fourteen of 32 patients who had nonlocalizing ^99mTc-sestamibi imaging studies underwent an additional scan after thyroid suppression. In 10 of 14 patients (71%), repeat ^99mTc-sestamibi imaging after thyroid suppression successfully localized abnormal parathyroid tissue. Conclusions. Thyroid suppression may improve the yield of ^99mTc-sestamibi imaging in patients with hyperparathyroidism who have an initially nonlocalizing study. This diagnostic strategy may be helpful in patients motivated to undergo a directed, minimally invasive operation, as well as in the evaluation of patients for reoperative parathyroidectomy.