Intraindividual Comparison of Radiation Dose and Image Quality: Photon-counting versus Energy-integrating Detector CT in Obesity

Background Maintaining diagnostic CT image quality in patients with obesity remains challenging because increased x-ray attenuation is often offset by higher radiation exposure. Photon-counting CT (PCCT) has demonstrated improved dose efficiency and image quality, but intraindividual data in this population are limited. Purpose To compare radiation dose, quantitative image quality, and subjective image quality between PCCT and energy-integrating detector (EID) CT intraindividually in patients with obesity. Materials and Methods This retrospective study included patients with obesity undergoing thoracic and/or abdominal CT at both PCCT and EID CT between December 1, 2022, and January 31, 2025. Signal, image noise, and signal to noise ratio (SNR) were measured in vascular, parenchymal, muscular, and adipose tissue. Two radiologists independently rated image quality on a six-point Likert scale. Radiation dose parameters were volume CT dose index (CTDIvol), dose-length product (DLP), and effective dose. The paired two-sided t test or Wilcoxon signed-rank test was used for group comparisons. Results This study included 51 patients with obesity (median age, 56 years [IQR, 51-66.5 years]; 33 male). Signal was higher with PCCT than EID CT in vascular structures, parenchymal organs, and muscle and more negative in subcutaneous fat (all P < .001), with similar image noise (P = .09-.84). SNR was higher with PCCT in vascular structures (ascending aorta: mean, 19.65 ± 6.47 [SD] vs 13.22 ± 4.83; P < .001) and most parenchymal organs (liver: 5.53 ± 1.69 vs 4.71 ± 1.89; P = .02). The difference in SNR increased with body mass index for vessels (r = 0.36) and parenchymal organs (r = 0.51) (both P < .001). Both readers rated overall image quality, contrast, and sharpness higher and artifact-related impairment lower for PCCT (all P < .001), whereas subjective image noise was similar (P = .16 and .14). CTDIvol (median, 11.99 vs 17.05 mGy) and DLP (median, 526.25 vs 709.32 mGy · cm) were lower with PCCT (both P < .001). Conclusion In patients with obesity, intraindividual comparisons demonstrated that PCCT had superior quantitative and subjective image quality at a lower radiation dose than EID CT.