Dual-energy 4-phase CT scan in primary hyperparathyroidism.

We read with interest the article by Gafton et al published in 2012. The authors illustrated the use of a dual-phase CT protocol for the enhancement characterization of parathyroid lesions and suggested the elimination of precontrast and delayed scan phases from 4D CT to reduce radiation exposure. In this letter, we describe the alternative approach of our institution to 4D CT. Our modified 4D CT protocol uses virtual noncontrast (VNC) images obtained from dual-energy CT-reconstructed venous-enhanced images to replace true precontrast scans. This process allows a complete examination of the contrast enhancement and washout characteristics of parathyroid adenomas on 4D CT, without reducing the number of scan phases. Here we present a 57-year-old female patient who was suspected of having primary hyperparathyroidism (PHPT) and was scanned by using our modified 4D CT protocol. The institutional review board approval was waived for this dose-saving study. The patient was referred for neck imaging using our modified protocol after negative technetium Tc99m-sestamibi scintigraphy findings, despite the presence of elevated total serum calcium and parathyroid hormone levels. A modified 4-phase CT scan was obtained, with a dual-energy scan acquired during the venous phase.