P880Determination of right ventricular volume and function using multiple axially rotated MRI slices.

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Background: The complex shape and orientation of the right ventricle(RV) is a challenging factor in the visualization and assessment of RV function on magnetic resonace imaging (MRI). In clinical practice, RV volume analysis relies on short axis (SA) views obtained simultaneously with the LV. In SA acquisitions, excluding atrial volume from the ventricular measurement is important. To obtain an optimal visualization of the RV inflow and outflow tract, we suggest an orientation based on six slices rotated around the long axis of the RV (RLA).Material and method: Three phantoms were investigated in SA and RLA using cine balanced steady state free precession MRI. Volumes were calculated based on segmentation and checked against true volumes. In 23 healthy male volunteers we used six long axis planes from the middle of the tricuspid valve to the RV apex, rotated in 30 degree increments. For comparison, SA slices were acquired. Imaging parameters were identical in both acquisitions.Results: RV end-diastolic, end-systolic and stroke volumes determined in the RLA 179.1 ± 29.3; 80.1 ± 17.1; 99.3 ± 16.9 ml and in the SA were 174.0 ± 21.1; 78.8 ± 13.6; 95.3 ± 14.5 ml with p-values for the difference from 0.17 to 0.64 (ns). Inter-observer variability ranged between 3.2% and 6.6%, intra-observer variability between 2.8% and 6.8%. In SA views, consensus for the definition of the basal slice was necessary in 39% of the volunteers for whom the average volume change was 20% in end-systolic and 10% in end-diastolic volume.Conclusions: The RLA method results in better visualisation and definition of the right ventricular inflow, outflow and apex. Accurate measurement of RV volumes for diagnosis and follow up of cardiac diseases may be enhanced by the RLA orientation.

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