Pulmonary Artery CT Angiography on Photon-Counting Detector CT: A Practical One-Stop Acquisition, Reconstruction, and Reporting Protocol

Background/Objectives: Computed tomography pulmonary angiography (CTPA) is the first-line test for suspected acute pulmonary embolism (PE), yet respiratory and cardiac motion artifacts, non-diagnostic opacification, subsegmental interpretive uncertainty, contrast medium and radiation dose burdens, and historically variable reporting persist. Photon-counting detector CT (PCCT), together with the newly released Pulmonary Embolism Reporting and Data System (PE-RADS) v2026, creates the opportunity for a standardized one-stop examination. This technical note consolidates the PCCT-CTPA evidence base into a practical acquisition, reconstruction, and reporting protocol. Methods: The protocol was developed as a narrative, literature-informed synthesis of the PCCT-CTPA evidence base, identified by searching PubMed/MEDLINE, Scopus, and Web of Science from January 2021 (first clinical PCCT installation) to July 2026; sources included randomized and comparative clinical studies, phantom experiments, and a 2026 systematic review and meta-analysis pooling 12 studies and 950 patients. This technical note is not itself a systematic review, and pooled effect sizes are quoted from that existing meta-analysis rather than newly derived. Results: The protocol specifies a sub-second (<1 s), free-breathing, dual-source high-pitch acquisition in QuantumPlus multi-energy mode, 25–40 mL of contrast medium as evidence-based example regimens rather than fixed volumes, routine reading on 50–55 keV virtual monoenergetic images (VMIs) with 40 keV bolus salvage and 90–120 keV streak suppression, iodine distribution (perfused-blood-volume surrogate) maps from the same scan at no additional dose, an optional ultra-high-resolution (UHR) problem-solving tier that replaces, rather than adds to, the standard acquisition in selected patients, and reporting aligned with PE-RADS v2026 categories, designations, and accessory findings. Effective doses of 1.3–1.4 mSv have been reported for low-dose PCCT protocols (including the free-breathing ultra-high-pitch protocol) under specified conditions; 89% of routine PCCT examinations were entirely artifact-free versus 28.6% on energy-integrating detector CT (EID-CT); and iodine maps diagnosed chronic thromboembolism with sensitivity 0.94 and specificity 0.84 at 1.3 mSv. Reported dose and contrast savings are protocol-dependent and did not retain meta-analytic significance after conservative adjustment. Conclusions: PCCT enables an evidence-supported, PE-RADS-ready one-stop CTPA protocol delivering morphology and iodine-distribution (perfused-blood-volume surrogate) maps in every patient. It complements rather than replaces conventional CTPA, and local validation of dose, contrast use, and reporting outcomes is advised. Whether improved peripheral visibility translates into improved diagnostic accuracy for subsegmental PE remains unproven.