Parathyroid imaging with technetium-99m-sestamibi: preoperative localization and tissue uptake studies.

The accepted radionuclide method for imaging abnormal parathyroid tissue has been the combined use of [99mTc]pertechnetate 201Tl-chloride. Various problems with this approach, however, have suggested the need for an improved parathyroid imaging agent. This study examined the use of 99mTc-sestamibi as a parathyroid imaging agent compared with 201Tl-chloride. Fifty-seven patients were scanned with both 99mTc-sestamibi and 201Tl preoperatively. There were 40 adenomas, of which 37 were localized with 201Tl and 39 with sestamibi. Fifteen patients had hyperplastic glands, of which 29 glands were localized with 201Tl and 32 with sestamibi. Possible differences in uptake of the two agents by thyroid and parathyroid tissue were examined by administering 10 MBq of each agent to patients undergoing surgical exploration and biopsy. Preoperatively 20 patients were studied (13 adenomas and 7 with hyperplasia). Thallium-201 uptake was higher in both the parathyroid and thyroid tissue than sestamibi. However, the uptake per gram of parathyroid tissue of sestamibi was higher than the uptake per gram of thyroid tissue. This was not true for 201Tl. Technetium-99m-sestamibi was at least as effective as 201Tl in parathyroid localization. This may be partly due to a higher target-to-background ratio, but also to the superior physical characteristics of 99mTc.