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

The conventional magnetic resonance imaging (MRI) method for right ventricular (RV) volume and motion, using short-axis (SA) orientation, is limited by RV anatomy and shape. We suggest an orientation based on six slices rotated around the long axis of the RV, rotated long axis (RLA).

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° increments. For comparison, short-axis slices were acquired. Imaging parameters were identical in both acquisitions.

Right ventricular end-diastolic (EDV), end-systolic (ESV) and stroke volumes (SV) 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). Interobserver variability ranged between 3.2% and 6.6% and intraobserver 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 ESV and 10% in EDV.

The RLA method results in better visualization and definition of the RV inflow, outflow and apex. Accurate measurement of RV volumes for diagnosis and follow-up of cardiac diseases are enhanced by the RLA orientation, even though additional acquisition time is required.