Accurate planning of minimally invasive surgery of parathyroid adenomas by means of [(99m)Tc]MIBI SPECT.

Aim: The aim of the study was to evaluate the clinical role or [(99m)Tc]MIBI SPECT in selecting primary hyperparathyroid (PHPT) patients for minimally invasive radioguided surgery (MIRS).
Methods: One hundred and forty-one consecutive PHPT patients were studied by a single-session [(99m)Tc]Percethnetate/[(99m)Tc]MIBI subtraction scintigraphy, followed by [(99m)Tc]MIBI SPECT in order to localize hyperfunctioning parathyroid adenoma (PA) and plan the surgical approach.
Results: A solitary PA was depicted at preoperative scintigraphy in 135 of 141 patients (95.7%), two or more PA in 5 patients, and was negative in 6 patients (4.3%). In 27 patients, the PA was located deep in the paraesophageal/paratracheal space. One hundred and twenty-four patients (in 18 of them the PA was located deeply in the neck) underwent successful MIRS using the low 37 MBq (1 mCi) [(99m)Tc]MIBI dose protocol. Intraoperative quick parathyroid hormone (QPTH) assay demonstrated a fall >50% in respect to the baseline value in all patients, confirming successful parathyroidectomy. After a follow-up of 6 to 37 months (median 18 months), no case of persistent/recurrent PHPT was recorded. When comparing the parathyroid to background (P/B) ratio measured at planar and SPECT preoperative scintigraphy with that measured intraoperatively with the gamma probe, a significant linear correlation was found between the SPECT and intraoperative gamma probe measurements (r = 0.91; P <0.01) while no correlation was found with planar scintigraphic data.
Conclusions: Our data suggest that the P/B ratio calculated by means of [(99m)Tc]MIBI SPECT is more accurate in predicting the intraoperative measurements with the intraoperative gamma probe. Thus, a preoperative [(99m)Tc]MIBI SPECT acquisition should be recommended for a better selection of PHPT patients to offer MIRS.