Dual-energy computed tomography pulmonary angiography for pulmonary embolism: a three-tier evidence framework to guide individualized low-iodine scanning

Dual-energy computed tomography (DECT) pulmonary angiography (CTPA) is widely studied for pulmonary embolism (PE) evaluation, but heterogeneity in protocols, platforms, and study designs complicates its clinical positioning. This narrative review, with structured search elements adapted from the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020, synthesized evidence from PubMed, Embase, Web of Science, and China National Knowledge Infrastructure (January 2016-June 2026); 28 studies were eligible (26 of 1,287 screened records and 2 identified through citation tracing). Evidence was organized into a three-tier framework (image quality, diagnostic performance, and clinical outcomes). Low-keV virtual monoenergetic imaging at 40-50 keV improves vascular attenuation and enables iodine load reduction to approximately 6 g in selected protocols. Pooled meta-analytic evidence shows no consistent diagnostic advantage of DECT over single-energy CT. The right ventricular/left ventricular diameter ratio remains the most stable prognostic indicator; DECT perfusion metrics have not surpassed it for mortality prediction. Iodine-map hypoperfusion in distal arteries is suspicious for, but not morphologically confirmed as, subsegmental PE; such findings carry a risk of overdiagnosis and warrant caution before anticoagulation. A body mass index- and estimated glomerular filtration rate-stratified protocol table with Oxford Centre for Evidence-Based Medicine 2011 evidence-level annotations is provided, and knowledge gaps in photon-counting CT, artificial intelligence, and cross-platform standardization are identified.