Quantitative Evaluation of Image Quality Improvement and Reduced Radiation Output with Photon-Counting CT in 4D Parathyroid Imaging

BACKGROUND AND PURPOSE: Parathyroid four-dimensional CT (4DCT) involves repeated non-contrast and multiphase contrast-enhanced acquisitions, leading to increased radiation exposure. As the examination targets the anatomically complex structures of the neck, maintaining high image quality is particularly important. Photon-counting CT (PCCT) is a novel technology reported to improve dose efficiency and image quality compared to conventional energy-integrating detector CT (EIDCT). This study provides a systematic, quantitative comparison of CT scanner radiation output (CTDIvol and DLP) and image quality, assessed by signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), between PCCT and EIDCT for multiphase parathyroid 4DCT exams. MATERIALS AND METHODS: In this IRB-approved retrospective study, 96 patients who underwent a 4DCT for the workup of hyperparathyroidism (PCCT, n = 32; EIDCT, n = 64) were reviewed. Regions of interest (ROIs) were placed on the non-contrast, arterial, and venous phase images in the sternocleidomastoid muscles at the upper thyroid level, the anterior scalene muscles at the lower thyroid level, and in the extracorporeal air. Mean attenuation, SNR, and CNR were measured. Statistical analyses included unpaired t-tests and two-way ANOVA. RESULTS: PCCT had significantly lower radiation output across all 4DCT phases (total CTDIvol 30.6 ± 3.3 vs. 60.8 ± 15.7 mGy; DLP 859 ± 178 vs. 1523 ± 519 mGy·cm; P < .001). SNR and CNR were significantly higher on PCCT across all evaluated ROIs, with lower background noise (all P < .05). Two-way ANOVA confirmed the advantages of PCCT regardless of contrast injection side, with no significant interactions. CONCLUSIONS: PCCT substantially reduces CT scanner radiation output while improving quantitative image quality in multiphase parathyroid 4DCT, including technically challenging arterial-phase acquisitions at the lower thyroid level, supporting its technical advantage over conventional EIDCT.