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Figure 5-8. A, Preoperative sestamibi scan 15 minutes following injection, suggestive of a solitary right lower parathyroid adenoma. B, Preoperative sestamibi scan 2 hours following injection, suggestive of a solitary right lower parathyroid adenoma. C, Preoperative sestamibi scan 1 hour after injection, suggestive of left lower parathyroid adenoma.

Figure 5-8. A, Preoperative sestamibi scan 15 minutes following injection, suggestive of a solitary right lower parathyroid adenoma. B, Preoperative sestamibi scan 2 hours following injection, suggestive of a solitary right lower parathyroid adenoma. C, Preoperative sestamibi scan 1 hour after injection, suggestive of left lower parathyroid adenoma.

primary disease. IOPTH was accurate in 78% of cases of primary disease and in only 45% of cases of secondary disease. For this reason, only patients with a positive single hot area on sestamibi scan should be considered candidates for a minimal approach.

Use of radioguidance via the gamma probe makes use of the fact that cells in a parathyroid adenoma contain a proportionately higher number of mitochondria compared with those in normal parathyroids and surrounding tissues. Thus, these mitochondria take up and retain Tc 99m sestamibi to a greater degree, and the increased radioactivity can be assessed with a gamma probe.43 Proponents of this technique feel that it minimizes incision length, permits local anesthesia, and directs the dissection. The use of the gamma probe for intraoperative radioguidance was recently evaluated.44 Prior to surgery, a sestamibi scan was used to visualize the solitary adenoma and a gamma probe was used to guide surgical dissection. In 48% of cases, the gamma probe provided confusing or inaccurate information and only detected increased radioactivity when placed directly over the exposed adenoma, and there was significant equipment failure and logistical problems with radioisotope administration. Another study found false-positive results owing to sestamibi retention from thyroid nodules. The gamma probe failed to locate a second adenoma in 75% of cases.45 It appears to add little benefit, especially with experienced endocrine surgeons. This seems especially true given the well-established efficacy of parathyroidectomy without radioguidance. It nearly tripled operating time in one study,46 and there was a 2-hour delay after intravenous injection until the probe could be used.42 It is certainly no substitute for sound surgical technique. Another study found that preoperative Tc 99m sestamibi imaging is far more accurate than intraoperative gamma probe detection in localizing abnormal parathyroids.47 The sensitivity of sestamibi was 100% for hyperplasia and 81% for adenoma compared with 0% and 50% for the gamma probe, respectively.

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