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_CT was quantified in the entire myocardium; lesion ECV_CT was quantified using a threshold-based approach with lesions exceeding an ECV_CT of 40%. Relative lesion volume was calculated as the proportion of lesion to total myocardial volume. Global ECV_CMR was calculated across all myocardial segments, lesion ECV_CMR was derived from manual segmentation. In the 20 patients, lesion ECV_CT was 45.2% (IQR 44.2-46.8%) compared to a global ECV_CT of 28.5 ± 5.3%. Relative lesion volume strongly correlated with global ECV_CT (ρ = 0.938, P < 0.001). A global ECV_CT 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_CT (28.0 ± 5.2%) and global ECV_CMR (29.3 ± 4.2%) was similar (P = 0.085, mean difference 1.4%, 95% limits of agreement: - 4.2 to 7.0%). Lesion ECV_CT (45.2%, IQR 44.6-46.8) and lesion ECV_CMR (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.