Mean Thoracic Aortic Wall Thickness Determination by Cine MRI with Steady-State Free Precession: Validation with Dark Blood Imaging

Abstract

To assess the validity and reliability of measuring mean aortic wall thickness (MAWT) of the ascending and descending aorta using cine steady-state free precession (SSFP) imaging compared to dark blood (DB) imaging. DB and SSFP images of the thoracic aorta acquired at 1.5 T in 50 volunteers (26 women, 24 men; mean age: 50.2 ± 13.1 years) were used. MAWT was calculated on DB and SSFP images for the ascending and descending aorta at the level of the right pulmonary artery by two independent observers. Validity was assessed using Bland-Altman analysis, Passing-Bablok regression, and Spearman correlation. Reliability was assessed using Bland-Altman analysis and intraclass coefficients (ICCs). The mean MAWT of the ascending aorta on DB and SSFP images was 1.89 ± 0.21 mm and 1.87 ± 0.20 mm. The measurements for the descending aorta were 1.60 ± 0.22 and 1.63 ± 0.20 mm, respectively. Comparison of DB and SSFP measurements revealed a mean bias of 1.3% (95% limits of agreement (LOA): -7.9, 10.5%) for the ascending and of -2.1% (LOA: -10.5, 6.3%) for the descending aorta. The corresponding regression equation was y = 0.042 + 0.960 × (r = 0.91; P < .0001) and y = 0.118 + 0.939 × (r = 0.95; P < .0001), respectively. Intra- and interobserver variability showed a mean bias of less than 2.0% and LOA of less than ±15.0%. ICCs were greater than or equal to 0.85. MAWT determination in the ascending and descending aorta using cine SSFP sequences is highly valid and reliable compared to DB imaging.