Determination of the left ventricular long‐axis orientation from a single short‐axis MR image: relation to BMI and age

Abstract

Accurate determination of imaging planes in relation to the left ventricular (LV) long‐axis orientation is important for anatomical and functional evaluation as well as for serial comparisons with cardiac magnetic resonance (CMR) imaging. Therefore, a fast and reliable method to test the accuracy of CMR imaging for measuring the orientation of the LV long‐axis was developed and validated. In addition, the relationship between LV long‐axis orientation and body mass index (BMI), gender and age was assessed. Two approaches were used, a long‐axis approach (based on a manually defined vector) and a short‐axis approach (based on a calculated vector). The concordance between the two approaches was assessed in 72 healthy volunteers. The accuracy and precision of MR imaging for measuring three‐dimensional orientations were tested using a LV phantom. The mean difference between the long‐ and short‐axis approaches for measuring the LV long‐axis orientation in the study population was 0 ± 3°, 0 ± 2°, and −1 ± 3° in the frontal, transverse and sagittal plane, respectively. BMI and age were shown to influence LV long‐axis orientation, especially in the frontal and sagittal planes. A significant difference in LV long‐axis orientation in the frontal and sagittal planes was found between genders. The correlation coefficient between MR‐measured phantom orientation and true phantom orientation was >0·98 in all three orthogonal planes. These observations suggest that a single LV short‐axis MR image can be used for measuring LV long‐axis orientation in patients with no cardiac disease.