Reduction of Radiation Dose and Contrast Medium Volume in Photon-Counting Detector Computed Tomography Head and Neck Angiography: A Comparison to Energy-Integrating Detector Computed Tomography.

Rationale And Objectives: This study evaluated the image quality of photon-counting detector computed tomography (PCD-CT) for head and neck vascular imaging using the "Quadruple Low" strategy (ultra-low contrast dose, low contrast concentration, low injection rate, and low radiation dose). The results were compared with those from conventional energy-integrating detector computed tomography (EID-CT) performed using routine scanning parameters.

Materials And Methods: This retrospective cohort study included 50 patients with cerebrovascular disease who underwent EID-CT with a standard contrast protocol (contrast dose: body weight × 0.6 mL/kg), serving as the control group (CG). Two prospective cohorts, each comprising 50 patients, underwent PCD-CT with an optimized contrast protocol (contrast dose: body weight × 0.4 mL/kg; injection rate: contrast dose/[delay time + scan duration]), forming the experimental groups (EG1 and EG2). In EG2, the radiation dose was further reduced relative to that in EG1. Objective image quality was assessed by measuring vascular attenuation, image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). Subjective image quality was evaluated using a 5-point Likert scale.

Results: This study included 150 patients (86 men; mean age, 56.03 ± 11.10 years; mean body mass index[BMI], 24.28 ± 3.03 kg/m²). Compared with the CG, the optimized contrast protocol in EG1 and EG2 reduced the median contrast volume by >30%, decreased the contrast concentration by 9%, and lowered the injection flow rate by 10% (all p < 0.001). The effective radiation dose in EG2 was reduced by 28% (p < 0.001) while maintaining image quality comparable to that of other groups (p > 0.05). EG2 exhibited a greater potential for radiation dose reduction. EG1 and EG2 exhibited significant improvements in vascular attenuation, reduced image noise, and enhanced SNR and CNR. Subjective image quality was consistently rated as high across all groups, with a median Likert score of 4 (IQR: 4-5), and excellent interobserver agreement (κ = 0.814-0.934), indicating consistently high diagnostic confidence.

Conclusion: PCD-CT using the "Quadruple Low" strategy enables neurovascular imaging with substantially reduced contrast media and radiation exposure, while maintaining image quality comparable to conventional EID-CT. This protocol may serve as a safer alternative in routine cerebrovascular evaluation.