With the diagnosis of primary hyperparathyroidism, patients are counseled regarding the standard versus radioguided approach. Sestamibi scintigraphy or any other localizing studies are not performed until the day of the surgery. Patients are scheduled for an operation and the surgical technique used (standard vs. radio-guided parathyroidectomy) is dictated by the results of the sestamibi scintigraphy performed an hour or two before the procedure. Because of the importance of timing, it is our recommendation that surgeons learning this technique begin by selecting patients for radioguided parathyroidectomy who have had a sestamibi scan, deemed clearly positive, a week or two before the surgery. Subsequently, once the technique has been learned, the goal is to scan patients only once, 1 or 2 h before surgery. If a single adenoma is found on the presurgical scan, then radioguided parathyroidectomy is performed. If no localization occurs, a standard bilateral exploration will be performed (Fig. 1).
Because of the tremendous variability in the quality of sestamibi scans from institution to institution, the percentage of patients who are able to undergo radioguided parathyroidectomy will vary at each hospital. The dosage of 99mTc-sestamibi that we use is 740-925 MBq (20-25 mCi) . In working closely with our nuclear medicine department, we are able to get a positive sestamibi scan on 86.9% of all patients referred. Interestingly, only about 6% of patients referred
to us have had scans previously, with the majority having negative scans. The weight rests on the surgeon, not just the nuclear medicine physician, to review the films closely and be confident that the scan is positive. Our definition of a positive sestamibi scan is one that has been performed on a patient with sporadic primary hyperparathyroidism that shows a single focus of increased radioactivity which is distinct and separate from the thyroid. In order to achieve the latter part of this definition, more than just anterior-posterior views must be obtained. We strongly believe that simple oblique views are the only other views that are needed, and in fact are essential to clearly delineate the focus of radioactivity separate from the thyroid. Interestingly, lateral views are almost universally useless.
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