Background  In surgery for primary hyperparathyroidism, preoperative localization together with intraoperative parathyroid hormone assay is important when minimal invasive operations of the parathyroid glands are intended. In cases of reoperation, correct localization of the abnormal parathyroid glands is extremely instrumental. Computed tomography (CT)–^99mTc-sestamibi (MIBI)–single photon emission computed tomography (SPECT) image fusion allows for a virtual exploration of the neck by showing the suspected gland three-dimensionally with all the anatomic landmarks in correct position. The aim of this study was to evaluate whether CT–MIBI–SPECT image fusion is superior to MIBI–SPECT alone in detecting abnormal parathyroid glands in patients with previous neck surgery.

Patients and methods  In a prospective study, CT–MIBI–SPECT image fusion for preoperative localization was performed in 28 patients with hyperparathyroidism and previous neck surgery. Twenty-one patients had thyroidectomy and seven patients had surgery for hyperparathyroidism. The results of MIBI–SPECT alone and CT–MIBI–SPECT image fusion were compared in these patients. The outcome and the exact predicted position, not just the predicted side, were correlated with intraoperative findings.

Results  CT–MIBI–SPECT image fusion was able to predict the exact position of the abnormal gland in 24 of 28 patients (86%), whereas MIBI–SPECT alone was successful in 12 of 28 cases (43%, p < 0.004) only. CT–MIBI–SPECT image fusion detected all three pathologic glands in their ectopic position. With MIBI–SPECT alone, just one ectopic pathologic gland was found.

Conclusion  This study provides evidence that CT–MIBI–SPECT image fusion is superior to MIBI–SPECT alone in preoperative localization of enlarged parathyroid glands in patients with hyperparathyroidism and previous neck surgery. This should be kept in mind if the results are compared to earlier studies concerning CT–MIBI–SPECT image fusion.