Non-invasive imaging techniques have become the reference for the diagnosis and the quantification of edema and myocardial fibrosis in myocarditis, surpassing invasive endomyocardial biopsy by avoidng procedural risks and sampling errors [1,2]. Myocardial extracellular volume (ECV), a biomarker for the assessment myocarditis, is a key criterion for non-ischemic myocardial injury in the 2018 revised Lake Louise criteria [1].

Elevated ECV levels, associated with inflammation, edema, or extracellular infiltration, have been widely studied in both infiltrative and ischemic cardiomyopathies [2,3]. While cardiac magnetic resonance imaging (MRI) remains the reference method for calculating ECV, few studies have investigated the potential role of single-energy or dual-energy computed tomography (CT) in assessing ECV in various conditions [[4], [5], [6], [7], [8], [9], [10]].

To determine ECV with CT, the change in iodine concentration in the myocardium is normalized by the corresponding change in the blood pool. The single-energy CT method calculates ECV based on the change in CT attenuation between the pre- and post-contrast enhancement images. Alternatively, dual-energy CT helps calculate ECV directly from late enhancement iodine maps of. This not only avoids additional radiation exposure, but also allows calculation of ECV from a single scan without potential misregistration between successive scans [[11], [12], [13]].

Dual-source photon counting detector CT (PCD-CT) is a cutting-edge technology, which improves several limitations of conventional energy-integrating scintillation detectors, such as electronic noise, spatial resolution, contrast-to-noise ratio, and spectral imaging capability [11]. PCD-CT simultaneously provides two energy thresholds, which are based on material decomposition into two fundamental components, such as iodine and water [[10], [11]]. Since the introduction of PCD-CT in 2021, there is some evidence in the literature regarding the feasibility of ECV calculation using this new technology [[11], [12], [13]]. A recent meta-analysis demonstrated an excellent correlation between ECV-CT and ECV-MRI in 13 cardiothoracic and abdominal studies [14]. However none of these studies included ECV-CT derived from PCD-CT images.

The purpose of this study was to evaluate the feasibility and accuracy of myocardial LIE for ECV quantification using PCD-CT in patients with suspected acute myocarditis by comparison with cardiac MRI.