Comparison of aortic valve area measured by magnetic resonance imaging and dual-source computed tomography.

ABSTRACT

BACKGROUND: Aortic valve stenosis is the most common type of valve lesion in Europe and North America. Patient treatment is based on disease severity, which is classified by determining the aortic valve area (AVA). PURPOSE: To compare dual-source computed tomography (DSCT) with magnetic resonance (MR) imaging for quantifying AVA. MATERIAL AND METHODS: Thirty-two patients, 28 with normal aortic valve function and four with aortic valve stenosis, who underwent DSCT coronary angiography (Somatom Definition; Siemens, Erlangen, Germany), were included in this study. Retrospective ECG-gated contrast-enhanced DSCT scans with dose-reducing tube current modulation were performed, and data sets were reconstructed in 3% steps of the R-R interval (slice thickness 0.75 mm, increment 0.6 mm). Planimetry of the AVA in systole was assessed on cross-sectional images by multiplanar reformations. Within 48 hours, MR was performed with a 1.5T scanner (Magnetom Sonata; Siemens, Erlangen, Germany) using a balanced steady-state free-precession cine sequence (repetition/echo time 3/1.5 ms, flip angle 60 degrees, spatial resolution 1.4 x 1.4 mm(2)). Cine sequences of the left ventricular outflow tract (LVOT) were obtained in two orthogonal planes, and MR planimetry was performed on cross-sectional images of the aortic valve perpendicular to the LVOT images. RESULTS: AVA assessment by DSCT and MR was feasible in all 32 patients. Mean AVA values determined by DSCT and MR were 4.73+/-1.5 cm(2) and 4.69+/-1.4 cm(2), respectively. A strong positive correlation was found between both imaging modalities (R=0.98, P<0.001). Bland-Altman analysis demonstrated an excellent intermodality agreement, with a slight underestimation of AVA by DSCT. The mean difference was -0.04 cm(2), with a standard deviation of 0.32 cm(2). CONCLUSION: Retrospective ECG-gated contrast-enhanced DSCT with tube current modulation provides an accurate imaging technique for the assessment of the AVA. Further studies are required to determine whether DSCT also allows for AVA quantification in patients with aortic valve stenosis.