The role of gamma probe activity counts in minimally invasive parathyroidectomy. Preliminary results.

Aim: The benefit of preoperative gamma probe in the diagnosis of adenoma in patients with histopathologically proven parathyroid (PT) adenomas was examined.

Patients, Material, Methods: 20 patients with positive (99m)Tc MIBI uptake in PT scintigraphy with primary hyperparathyroidism were enrolled in this study. 740 MBq (99m)Tc MIBI were injected 3 h before operation. Counts of four PT regions were obtained with gamma probe before surgery in the operation room. All suspected PT adenomas were resected and histopathologically diagnosed as adenomas. We also obtained counts of the resection region and the resected adenoma with gamma probe after the parathyroidectomy. Preoperative counts of adenoma bearing regions (ABR), non-adenoma bearing regions (NABR), postoperative resection region (PRR), resected adenoma counts (RA) were registered. Statistical analysis was performed by Wilcoxon rank test.

Results: The mean counts of ABR, NABR, the PRR and RA were 462 +/- 106, 230 +/- 66, 164 +/- 42, 374 +/- 87, respectively. The mean counts from ABR were twofold higher than those of NABR. The PRR mean counts decreased by 64% when compared to the mean counts of ABR and by 55% when compared to the mean counts of RA. The differences in mean counts of ABR and NABR, PRR and ABR, PRR and RA (p <0.01) turned out as statistically significant.

Discussion: According to our preliminary results, the region with the highest counts is at least 2 +/- 0,4 times higher than the mean of the other three PT regions. Thus, it seems to be significant for PT adenoma. Resection of adenoma may be accepted as successful, if the count of ABR decreased more than 64% with decreased postoperative parathormone levels.

Conclusion: This technique should not yet be applied instead of parathormone measurement or frozen technique. But it may replace the frozen technique used for confirmation of the diagnosis during the operation in the future.