RESUMEN
Background: In cardiac computed tomography (CT), the best image quality is obtained at mid-diastole at low heart rates (HRs) and at end-systole at high HRs. On the other hand, extracellular volume (ECV) measurements may be influenced by the cardiac phase. Therefore, we aimed to clarify the influence of the cardiac phase on the image quality and ECV values obtained using dual-layer spectral computed tomography (DLCT). Methods: Fifty-five patients (68.0±14.5 years; 26 men) with cardiac diseases who underwent retrospective electrocardiogram-gated myocardial CT delayed enhancement (CTDE) between February 2019 to April 2022 were enrolled. The ECVs at the right ventricle (RV) and left ventricle (LV) walls in the end-systolic and mid-diastolic phases were calculated using iodine-density measurements from CTDE spectral data. Iodine-density image quality was classified on a 4-point scale. ECV and image quality across cardiac phases were compared using the t-test and Wilcoxon signed-rank test, respectively. Inter- and intraobserver variability were evaluated using intraclass correlation coefficient (ICC) values. Results: The ECV of the septal regions during mid-diastole was significantly higher than that during end-systole. Other regions showed similar ECV measurements in both groups (P=0.13-0.97), except for the LV anterior wall and LV posterior wall at the base-ventricular level. The image-quality score in end-systole was significantly higher than that in mid-diastole (systole vs. diastole: 3.6±0.5 vs. 3.2±0.7; P=0.0195). Intra- and interobserver variabilities for RV ECV measurements at the end-systolic phase were superior to those at the mid-diastolic phase, whereas the corresponding values for LV ECV measurements were similar. Conclusions: Septal ECV showed small but significant differences while other region ECV showed no difference during the cardiac cycle. RV ECV measurements in the end-systolic phase were more reproducible than those in the mid-diastolic phase.
RESUMEN
To investigate the usefulness of high-resolution systolic T1 mapping using compressed sensing for right ventricular (RV) evaluation. Phantoms and normal volunteers were scanned at 3 T by using a high-resolution (HR) modified look-locker inversion recovery (MOLLI) pulse sequence and a conventional MOLLI pulse sequence. The T1 values of the left ventricular (LV) and RV myocardium and blood pool were measured for each sequence. T1 values of HR-MOLLI and MOLLI sequences were compared in the LV myocardium, blood pool, and RV myocardium. The T1 values of HR-MOLLI and MOLLI showed good agreement in both phantoms and the LV myocardium and blood pool of volunteers. However, there was a significant difference between HR-MOLLI and MOLLI in the RV myocardium (1258 ± 52 ms vs. 1327 ± 73 ms; P = 0.0005). No significant difference was observed between the T1 value of RV and that of LV (1217 ± 32 ms) in HR-MOLLI, whereas the T1 value of RV was significantly higher than that of LV in MOLLI (P < 0.0001). The interclass correlation coefficients of intraobserver variabilities from HR-MOLLI and MOLLI were 0.919 and 0.804, respectively, and the interobserver variabilities from HR-MOLLI and MOLLI were 0.838 and 0.848, respectively. Assessment of RV myocardium by using HR systolic T1 mapping was superior to the conventional MOLLI sequence in terms of accuracy and reproducibility.