Abstract
OBJECTIVES: To evaluate diagnostic image quality (IQ) for pulmonary embolism detection in photon-counting detector CT (PCD-CT) with significantly reduced contrast media (CM) dose vs conventional energy-integrating detector CT (EID-CT), using optimized and individualized CM protocols. MATERIALS AND METHODS: Consecutive CT pulmonary angiography (CTPA) scans performed on the EID-CT (Jan 2024-Mar 2024) with an individualized kilovoltage (kV) and total body weight (TBW) adapted CM protocol, and on the PCD-CT (Aug 2023-Feb 2024) with a TBW adapted CM protocol matching the 70 kV EID-CT protocol, were retrospectively collected. EID-CT scans were performed at 70-120 kV, based on patients' size, while PCD-CT scans were performed at 120 kV with 55 keV virtual monoenergetic images. Objective IQ assessment included mean attenuation (in Hounsfield Units), signal-to-noise ratio, and contrast-to-noise ratio (CNR). Two board-certified radiologists assessed diagnostic IQ subjectively using a five-point Likert scale. RESULTS: In 140 EID-CT and 118 PCD-CT scans, PCD-CT reduced total iodine load by 26.7% and CT dose index volume by 24.4%. Objective IQ parameters showed no significant differences, except for a decrease in CNR in the proximal pulmonary arteries in PCD-CT scans (p = 0.02). Subjective IQ was rated as moderate/good by observers 1 and 2 in 94.9% and 97.9% of the EID-CT scans, respectively, and 96.5% and 100% of the PCD-CT scans, respectively. CONCLUSION: PCD-CT with a TBW-adapted CM protocol can achieve substantial reductions in both CM and radiation dose compared to EID-CT with individualized kV and TBW adapted CM protocols, while maintaining diagnostic IQ in CTPA scans. KEY POINTS: Question The feasibility of CM reduction in PCD-CT vs EID-CT with highly individualized CM protocols, while maintaining diagnostic IQ. Findings PCD-CT reduces total iodine load by 26.7% and CT dose index volume by 24.4% compared to EID-CT, with comparable objective and subjective diagnostic IQ. Clinical relevance This approach enables CM reduction, potentially lowering patient risk and providing environmental and financial benefits. Additionally, PCD-CT allows for CM and radiation dose reduction while maintaining comparable IQ.