A study on the consistency of myocardial extracellular volume quantification in the systole and diastole phases using dual-layer detector spectral CT / 中华放射学杂志

ABSTRACT

Objective:To investigate the consistency of myocardial extracellular volume between systole and diastole using dual-layer detector spectral CT.Methods:This was a cross-sectional study. Thirty-five patients who underwent cardiac spectral CT examination in West China Hospital of Sichuan University from April 2022 to December 2022 were retrospectively collected. Hematocrit was collected within 3 days before the CT scan. The delayed phases holographic spectral images in systole (45%) and diastole (75%) were obtained using dual-layer spectral CT. CT data were processed using a spectral post-processing workstation, and the extracellular volume (ECV) based on iodine density images, referred as CT-ECV, in systolic and diastolic phases were calculated, respectively. According to the American Heart Association′s 16-segment model of left ventricular, the standard short-axis images were constructed, and the myocardium was standardized into 16 segments at the basal, mid-cavity, and apical levels of the left ventricle. Two radiologists performed a subjective evaluation in the image quality of the CT-ECV images of the whole heart and the three sections in systole and diastole using a "five-point" scale. The ECV of the 16 segments and the whole heart in systole and diastole was calculated. The consistency of subjective evaluations between systole and diastole was assessed using Kappa statistics. Wilcoxon signed-rank tests were used to compare the differences in scores between systole and diastole. Paired sample t-test was used to compare the differences in CT-ECV scores between systole and diastole. The intraclass correlation coefficient was used to test the intra-and inter-observer consistency of CT-ECV measurements between two radiologists. P<0.05 was statistically significant. Results:There was good agreement between the two radiologists on subjective scores of CT-ECV image quality between systole and diastole ( Kappa>0.80), and there was no statistical difference in image quality among the basal, mid-cavity, and apical levels of the left ventricle and whole heart between systole and diastole ( P>0.05). The systolic and diastolic CT-ECV for the entire heart obtained through the delay phase were (33.29±3.46)% and (33.50±3.39)%, respectively, with no statistically significant difference ( t=-0.78, P=0.442). CT-ECV in systole and diastole were (34.15±3.94)% and (35.30±3.99)% for segment 8, (34.03±3.76)% and (35.46±3.74)% for segment 9, and (33.98±3.32)% and (35.05±3.98)% for segment 14, respectively. The mean values of the systolic CT-ECV of segments 8, 9 and 14 were significantly lower than those of diastolic CT-ECV ( t=-2.65, -3.26, -2.42, P=0.012, 0.003, 0.022, respectively). The ICCs for CT-ECV measurements of 16 segments by the two radiologists were greater than 0.90 in both systolic and diastolic, indicating good agreement. Conclusions:There is no significant difference in whole heart CT-ECV values between systolic and diastolic myocardial ECV based on dual-layer spectral CT. However, minor differences (less than 2%) are found between systolic and diastolic myocardial CT-ECV for some segments. Myocardial CT-ECV measurement should be performed on the same segment during the same phase to obtain stable and accurate ECV values.