CT-derived myocardial extracellular volume: current evidence, clinical utility, and the emerging role of photon-counting CT-a systematic review

Objective: Cardiac extracellular volume (ECV) is a quantitative imaging biomarker of myocardial interstitial expansion and diffuse fibrosis, with cardiac magnetic resonance regarded as the reference standard method for assessment. Interest in computed tomography (CT)-derived cardiac ECV is increasing owing to its wide availability and potential integration into routine cardiac CT examinations. This systematic review was conducted within the framework of the European Network for the Assessment of Imaging in Medicine (EuroAIM). Materials and methods: This PRISMA-compliant systematic review searched PubMed, Embase, and Scopus, with the last search performed in December 2025. Extracted data included study design, target pathology, CT technology, acquisition approach, timing of delayed imaging, hematocrit estimation, region-of-interest methodology, type of comparator, and reporting and definition of ECV cutoff values. Study quality was evaluated using the Newcastle-Ottawa scale. Results: Of 304 unique records, 113 studies were included, with a marked increase in publications over the last 3 years (30 studies in 2025). Studies covered a broad range of clinical settings, including aortic stenosis, amyloidosis, heart failure, cardiomyopathies, myocarditis, and cardio-oncology. Sixty-seven studies were retrospective, and forty-six were prospective. ECV was assessed using single-energy CT (n = 65), dual-energy CT (n = 34), and photon-counting CT (n = 14, 10 of them in 2025). Cutoff values were reported in only 38 studies. The Newcastle-Ottawa Scale score was 6.33 ± 1.42 (mean ± standard deviation). Conclusion: Cardiac ECV is rapidly expanding, with photon-counting CT emerging as a promising platform. Nevertheless, substantial methodological heterogeneity and inconsistent cutoff reporting persist, highlighting the need for standardized protocols and harmonized reporting.