Direct comparison of neck pinhole (PH) dual tracer (DT) & dual phase (DP) sestamibi accuracies with & without SPECT/CT for parathyroid adenoma (PA) localization

Objectives There is uncertainty about accuracies of dual-phase (DP) Tc-99m sestamibi (MIBI) & DT (MIBI/I-123) parathyroid imaging protocols with the newly added SPECT/CT. Conversely, MIBI SPECT/CT was shown to be helpful in PA localization (LOC), however, it may not have optimal resolution as PH particularly when PA is close to or within thyroid. This study compares PH DP & DT accuracies with & without (W/WO) MIBI SPECT/CT in primary hyperparathyroidism patients (PHP).

Methods 155 PHP with pathologically confirmed diagnosis (Dx) had PH DT/DP & early neck/chest MIBI SPECT/CT. PH DP W/WO SPECT/CT was reviewed for PA Dx & LOC by 2 observers. A separate review of PH DT W/WO SPECT/CT was performed. Confidences in PA Dx & LOC were scored as certain, probable or uncertain. Furthermore, PA was classified as clearly or unclearly distinguishable from Thyroid. Contribution of delayed MIBI to PH DT was additionally scored as essential, confirming or non-contributory. Final Dx was classified as PA, parathyroid hyperplasia, & other/no pathology.

Results Of 153 confirmed PA, PH DT SPECT/CT was correct in Dx/LOC of 142 PA, significantly higher than PH DP SPECT/CT (104 PA). The ability to clearly distinguish PA from thyroid was higher in PH DT than DP W/WO SPECT/CT. Consequently, certainty of PA Dx was higher in PH DT than DP W/WO SPECT/CT. Certainty of PA LOC in both PH DT & DP were higher with than without SPECT/CT. In PH DT, delayed MIBI was essential for Dx/LOC of 24 uncertain PA.

Conclusions In our large group PHP, accuracy & certainty of PA Dx/LOC were both higher in PH DT SPECT/CT than PH DP SPECT/CT. PH DT better identified PA than PH DP, while SPECT/CT improved certainty of PA LOC in both. In PH DT, delayed MIBI addition showed limited contribution & thus should be only considered if PH DT findings for PA Dx/LOC are uncertain