Dual-isotope 99mTc-MIBI/123I parathyroid scintigraphy in primary hyperparathyroidism: comparison of subtraction SPECT/CT and pinhole planar scan.

PURPOSE: In patients with primary hyperparathyroidism, the preoperative imaging objective is to locate accurately and reliably uniglandular or multiglandular hyperfunctioning parathyroid, to guide surgery, particularly for minimally invasive method. Subtraction planar scintigraphy with dual-isotope (I/Tc-MIBI) is an efficient examination to specify abnormal parathyroid location, but without accurate anatomic reference. This lack should be avoided by a hybrid SPECT/CT image acquisition.

METHODS: We compared planar scans (neck and mediastinum parallel-hole, associated with anterior neck pinhole) to neck and mediastinum SPECT/CT, all with subtraction (I/Tc-MIBI) method, in exact location of abnormal parathyroid in 50 patients with sporadic primary hyperparathyroidism. Surgical and histological findings were used as the standard of comparison.

RESULTS: Sensitivity is equivalent for the 2 protocols (86% and 75% for SPECT/CT and planar protocol, respectively, P = 0.15), but SPECT/CT was highly specific (specificity 100% and 90% for SPECT/CT and planar protocol, respectively, P = 0.04). In patients with concomitant thyroid disease, subtraction SPECT/CT appeared to be more sensitive than planar protocol (88% and 62% for SPECT/CT and planar protocol, respectively, P = 0.04).

CONCLUSIONS: In preoperative assessment of primary hyperparathyroidism and to guide surgery, we propose to perform first subtraction SPECT/CT and to complete it with neck pinhole, only if tomoscintigraphy is negative.