The rationale for performing MR imaging before surgery for primary hyperparathyroidism.

OBJECTIVE: The purpose of this study was to evaluate prospectively Magnetic Resonance Imaging (MRI) for the preoperative localization of hyperfunctioning parathyroid glands.

DESIGN: Prospective study of 58 consecutive patients with biochemically confirmed primary hyperparathyroidism who underwent preoperative MRI.

SETTING: The setting is a referral centre.

PATIENTS: Fifty-six of the 58 consecutive patients (41 women, 17 men) were studied by both preoperative MRI and 99mTC MIBI scintigraphy, and two by MRI alone. The same surgeon, using the information from both MRI and 99mTC MIBI, performed surgery in 58 patients, including 19 with a history of neck surgery. Initial interpretation of each MR study was done independently by one radiologist and the surgeon and then results were compared. At surgery, the operative duration, the precise anatomical location, weight, and dimensions as well as complete histopathological evaluations of all excised glands were recorded.

MAIN OUTCOME MEASURE: In addition to the prospective assessment of MRI, this study compared performance of MRI with double-phase 99mTC MIBI scintigraphy for preoperative localization of hyperfunctioning parathyroid glands.

RESULTS: All patients became normocalcaemic after surgery. MRI and 99mTC MIBI imaging revealed 53 of 58 (91%) and 47 of 56 (84%) of abnormal glands, respectively. Sensitivities of MRI and 99mTC MIBI were respectively 94.3 and 88.0. Positive predictive values were 96.15 and 93.60. When MRI and 99mTC MIBI were interpreted together, the sensitivity and positive predictive values both raised to 98.10. Median operative duration was 30 minutes (ranges 20-300 minutes, mean 65).

CONCLUSION: MRI has better sensitivity and positive predictive value than 99mTC MIBI scintigraphy for the detection of hyperfunctioning parathyroid glands. The combination of the two studies provides an additional increase in sensitivity and positive predictive value leading to a more precise anatomical localization of the abnormal parathyroid glands reducing both the extent of the surgical dissection and the operative duration.