Aortic root measurement by cardiovascular magnetic resonance: specification of planes and lines of measurement and corresponding normal values.

BACKGROUND Cardiovascular magnetic resonance is widely used for aortic root visualization and measurement, but methods still need to be standardized. Our aim was to identify appropriate planes of acquisition and lines of measurement and record corresponding normal values. METHODS AND RESULTS We studied 120 healthy volunteers, 10 of each gender in each decile between 20 and 80 years, by using a 1.5-T cardiovascular magnetic resonance system. Steady-state free precession cine acquisitions aligned with the left ventricular outflow tract in oblique sagittal and coronal orientations were used to locate 2 sinus planes that transected the root at its widest point in its maximally expanded systolic and at its end diastolic positions. We measured the cusp-cusp and the cusp-commissure dimensions in these cine planes, each as the average of 3. Diastolic cusp-commissure dimensions were smaller than diastolic cusp-cusp dimensions (32.0+/-3.5 mm versus 34.6+/-4.0 mm in men, 28.4+/-2.8 mm versus 30.7+/-3.3 mm in women, P<0.001 for both). The diastolic cusp-commissure dimensions increased by 0.9 mm per decade in men and 0.7 mm per decade in women (P<0.001 for both) and gave higher R(2) values with respect to age and body surface area (0.40 for men, 0.27 for women) than diastolic cusp-cusp, systolic cusp-commissure, or sinus measurements made in the left ventricular outflow tract planes. CONCLUSIONS The results indicate the importance of consistent methods for measurement of the aortic root by cardiovascular magnetic resonance. We recommend diastolic cusp-commissure measurements, which yielded favorable R(2) values with respect to age and body surface area and were found to correspond closely with reference echocardiographic root measurements recorded in the Framingham cohort. We recorded reference values for these and other possible aortic root measurements by cardiovascular magnetic resonance.