Photon-counting detector computed tomography compared with cardiac magnetic resonance imaging for myocardial extracellular volume quantification in spontaneous coronary artery dissection

Spontaneous coronary artery dissection (SCAD) may cause myocardial infarction. Photon-counting detector computed tomography (PCD-CT) with late iodine enhancement (LIE) imaging enables myocardial extracellular volume (ECV) quantification. In this single-center, prospective study, we quantified myocardial ECV in patients with SCAD using LIE PCD-CT (n = 20 patients), and compared results with CMR (n = 13 patients). Global ECV was quantified in the entire myocardium; lesion ECV was quantified using a threshold-based approach with lesions exceeding an ECV of 40%. Relative lesion volume was calculated as the proportion of lesion to total myocardial volume. Global ECV was calculated across all myocardial segments, lesion ECV was derived from manual segmentation. In the 20 patients, lesion ECV was 45.2% (IQR 44.2-46.8%) compared to a global ECV of 28.5 ± 5.3%. Relative lesion volume strongly correlated with global ECV (ρ = 0.938, P < 0.001). A global ECV cut-off of 28.5% predicted relative lesion volumes < 5% with an AUC of 0.956 (95% CI 0.752-0.999) and a PPV of 82%. Global ECV (28.0 ± 5.2%) and global ECV (29.3 ± 4.2%) was similar (P = 0.085, mean difference 1.4%, 95% limits of agreement: - 4.2 to 7.0%). Lesion ECV (45.2%, IQR 44.6-46.8) and lesion ECV (45.0%, IQR 39.4-48.6) was similar (P = 0.340). In conclusion, LIE PCD-CT enables quantitative myocardial ECV assessment in SCAD patients, showing a good agreement with CMR.