High predictive value of integrated [^99mTc]MIBI SPECT/CT and high-resolution ultrasound for the preoperative localization of parathyroid adenomas in a series of 1319 patients imaged and treated at a single tertiary institution

Objectives: To assess the diagnostic performance of integrated parathyroid scintigraphy and cervical ultrasound in a large cohort of patients with primary hyperparathyroidism (pHPT) imaged and operated at a single tertiary institution.

Methods: The retrospective study included all parathyroid scintigraphies conducted at a single tertiary institution in Norway between January 2006 and December 2018. Exclusion criteria were: Secondary or tertiary HPT, repeat imaging, deviations from the standard imaging protocol. In 2006, patients underwent planar subtraction scintigraphy with [^99mTc]pertechnetate. Since 2007, imaging was performed as 3-phase scintigraphy with [^99mTc]MIBI with initial dynamic planar imaging, SPECT (since 2009: SPECT/CT on a Siemens Symbia T6; Siemens Healthineers, Hoffman Estates/IL) 30 min p.i. (Fig. panels A-C) and a 10-min planar image 3 h p.i. (Panel D). After the completion of scintigraphy, high-resolution ultrasound was conducted by the nuclear medicine specialist on a Hitachi EUB 5500 or Hitachi Preirus (Hitachi Medical Corp., Akihabara, Japan) (Panel E). All images were digitally archived in the department’s PACS. Parathyroidectomy was performed at the same institution. The diagnosis of a parathyroid adenoma was regarded as true positive if it was confirmed by pathology and follow-up revealed the resolution of HPT. All data were recorded in a custom-developed relational database. Statistical analysis was performed with R. The study was approved as a quality control study with no regulatory requirement for patient consent.

Results: 1319 patients with pHPT underwent their first parathyroid scintigraphy and ultrasound between January 2006 and December 2018. 1001 (76 %) were female. Age was 62 years (interquartile range (IQR) 54-73). Imaging was positive in 1038 patients (79 %) and negative in 281 (21 %). Of the 1038 patients with positive imaging, 810 (78 %) underwent operation, of the imaging-negative patients 110 (39 %; p < 0.001; Fisher’s exact test). Mean volume of the 737 correctly identified parathyroid adenomas was 0.3 ml (IQR 0.15; 0.67). 72 % were positive on SPECT(/CT) and 63 % on the late planar images. Using intra- and postoperative outcomes as a reference standard in the 920 operated patients, lesion-based sensitivity for the detection of a parathyroid adenoma was 89 %. The false-positive rate among lesions that were diagnosed as parathyroid glands on imaging was 9 %.

Conclusions: Multimodal imaging of patients with pHPT with [^99mTc]sestamibi and ultrasound in the hands of the same operator is both sensitive and specific, achieving a lesion-based sensitivity of 89 % with a false-positive rate of 9 %.

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