Assessing the left atrial phasic volume and function with dual-source CT: comparison with 3T MRI.

We wanted to assess the performance of dual-source CT (DSCT) for evaluating the left atrial volume and function and we compared this performance to that of the standard reference technique,cardiac cine MR (CMR). Fifty-one patients who were referred for CT coronary angiography were included in the study. Two were subsequently excluded for having un-analyzable MR images at the onset of left atrial contraction. For the remaining 49 patients, the DSCT data sets and FIESTA (fast imaging employing steady-state acquisition) cines of the vertical long axis covering the left atrium and the short axis covering the left ventricle were obtained on the same day. All the images were analyzed to obtain the maximal left atrial volume (LAVmax), the minimal left atrial volume (LAVmin), the left atrial volume just before left atrium contraction (LAVp), the left atrial reservoir volume (LARV), the left atrial ejection fraction (LAEF), the left atrial passive emptying volume (LAPV), the left atrial active emptying volume(LAAV), the left atrial conduit volume (LACV), the left ventricular end-diastolic volume (LVEDV), the left ventricular end-systolic volume (LVESV) and the left ventricular stroke volume (LVSV) by using 3D semi-segmentation software and Report Card 2.0 software, respectively, for the DSCT and CMR. All the parameters were normalized to the body surface area. Intermodality agreement was tested through linear regression and Bland-Altman analyses.Repeated measurements were performed to determine the interobserver variability. The DSCT measurements resulted in good correlation (r > 0.75) compared with those of CMR. However, DSCT slightly,but insignificantly overestimated the indexed LAVmax, LAVmin, LAVp, LARV, LAPV, LAAV and LACV, as reflected by biases of 1.2, 0.9, 1.1, 0.3, 0.1,0.2 and 0.4 ml/m(2), respectively. The LAEF was minimally, but insignificantly underestimated as reflected by a bias of -0.6% (P = ns). The variability of the DSCT measurements was lower than that of the CMR values. DSCT provides highly reliable and reproducible measurements of the left atrial phasic volume and function in patients who are referred for coronary CT imaging.