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Diagnostic Accuracy of Modified Low-Dose Four-Dimensional Computed Tomography for Preoperative Localization in Patients with Primary Hyperparathyroidism
*Courtney E Quinn, *Amit Mahajan, *Neeta J Erinjeri, *Taylor C Brown, *Jennifer Malinowski, *Glenda G Callender, Robert Udelsman, *Tobias Carling
Yale University School of Medicine, New Haven, CT

Objective: Primary hyperparathyroidism (PHPT) is common and amendable to curative parathyroidectomy. Four-dimensional computed tomography (4DCT) has demonstrated efficacy in the pre-operative identification of culprit lesion(s). While highly accurate, with sensitivity of 93.9%, 4DCT exposes patients to higher radiation doses than other imaging modalities. In 2012, our institution introduced a low-dose, 4DCT, by switching from a 5-phase to a 3-phase scan and reducing the kVp from 140 to 120 kV. The objective of this study is to assess the accuracy of low-dose 4DCT in the preoperative localization of abnormal parathyroid glands.
Design: Retrospective analysis of prospective database.
Setting: Tertiary academic referral center.
Patients: From April 2012 through December 2014, 933 patients with PHPT underwent parathyroidectomy. Of these, 404 had low-dose 4DCT imaging for localization.
Interventions: Low-dose 4DCT was instituted uniformly with a single radiologist interpreting these studies. Parathyroidectomy was performed using intra-operative intact parathyroid hormone (ioPTH) monitoring.
Main Outcome Measure(s): Low-dose 4DCT imaging reports were reviewed to determine pre-operative localization of abnormal gland(s). Operative and pathology reports were reviewed to determine anatomical position of the lesion(s) and to determine sensitivity and positive predictive value (PPV) of low-dose 4DCT.
Results: PHPT was due to single adenoma in 64.6% and multigland disease (MGD) in 35.1%. Overall sensitivity and PPV of low-dose 4DCT were 79.6% and 89.1%, respectively. Sensitivity and PPV for single adenoma were 98.3% and 88.8%, respectively. For MGD, sensitivity and PPV were 47.4% and 90.1%, respectively. Low-dose 4DCT has an effective dose reduction from 30mSv to 13.2mSv.
Conclusions: Low-dose 4DCT can reliably localize culprit lesions in patients presenting with PHPT caused by single gland disease, with comparable sensitivity to standard 4DCT, and decreased radiation exposure.

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