OBJECTIVES: Photon-counting detector (PCD) CT allows for ultra-high-resolution (UHR) imaging of the pulmonary vasculature. The aim of this study was to assess the benefits of UHR-PCD-CT pulmonary angiography (CTPA) over dual-energy energy-integrating-detector (EID) CTPA. MATERIALS AND METHODS: Comparing UHR-PCD-CTPA (n = 76 at image quality index (IQ) 50, n = 76 at IQ25) and dual-energy EID-CTPA (n = 75) acquired between April and October 2024, a total of 227 examinations were analyzed in this retrospective single-center study after excluding 56 ineligible studies. Hounsfield unit measurements and subjective image quality ratings of three radiologists (e.g., peripheral pulmonary artery visibility and diagnostic confidence) were investigated. RESULTS: Peripheral pulmonary artery visibility, overall image quality, and self-reported diagnostic confidence were higher in UHR-PCD-CTPA than in EID-CTPA (all p 0.05). Diagnostic confidence was stronger in UHR-PCD-CTPA vs. EID-CTPA (the two highest confidence scores reported by readers after viewing CTPAs and iodine-maps in 92.1-100% of IQ50, 94.6-100% of IQ25 and 66.6-73.3% of EID cases). Median attenuation in the pulmonary trunk was higher in UHR-PCD-CTPA (IQ25: 623.3 HU, IQ50: 567.8 HU) compared with EID-CTPA (397.2 HU, all p < 0.01). CT dose index was highest for IQ50 UHR-PCD-CTPA (6.7 ± 2.4 mGy), compared to EID-CTPA (4.7 ± 2.7 mGy) and IQ25 UHR-PCD-CTPA (3.0 ± 1.0 mGy; all p < 0.01). CONCLUSION: Image quality of CTPA benefits greatly from employing the UHR-mode in PCD-CT. Compared to EID-CTPA, even UHR-PCD-CTPA scans with a markedly lower radiation dose facilitate superior intraluminal attenuation, peripheral pulmonary artery visibility, and diagnostic confidence. KEY POINTS: Question With the introduction of a UHR scan option for PCD-CT of the pulmonary vasculature, the question arises whether patients benefit from this recent technological advancement. Findings UHR-PCD-CTPA offers improved image quality, increased pulmonary artery visibility, and higher diagnostic confidence, even with significant dose reduction compared to conventional EID-CTPA. Clinical relevance The advantages in subjective and objective image quality described for UHR-PCD-CTPA suggest potential for superior diagnostic performance in the work-up of pulmonary embolism.
Pannenbecker et al. (2026) studied this question.