Impact of Rotational and Translational Motion on Accuracy of One-dimensional Measurements of Regional Left Ventricular Systolic Deformation

Measurements of regional left ventricular (LV) systolic deformation are usually one-dimensional and thus, may be subject to errors induced by rotational and translational LV motion. The effects of these motions on the accuracy of the measurements are unknown. Accordingly, we performed ECG-gated short (SA) and long axis (LA) cine magnetic resonance imaging (MRI) with radiofrequency tissue tagging on eight normal volunteers (4 males; average age 35 yrs) under both resting conditions and on dobutamine (5-10 mcg/kg/min; DOB). Radially oriented “tag lines” were identified in the anterior, posterior and septal myocardium on the S images and in the lateral wall and septum on the L images on both the end diastolic (ED) and end systolic (ES) image frames. Endocardial and epicardial intersection points with the tag line were identified on the ED and ES images with the distance between these points representing wall thickness (cm). Rotational motion was calculated as the change in angle (Thet [°] measured from the LV cavity centroid to the middle of the MRI tag line. Measurements of translational motion (TRANS [cm]) were obtained by computing the distance between the ED and ES tag lines. Deformation was defined as the wall thickness at ES (cm). Measurements performed without the tag line information (W/O) to simulate one-dimensional measurements were compared with those incorporating the tag line information (WI). The absolute error (ABS) induced by not accounting for rotational and translational motion was determined as the absolute value of the difference between the measurements of wall thickness at ES with and without the tag line information divided by the value with the tag information × 100: Although rotational and translational LV motion is significant, the impact of these motions on one-dimensional measurements of deformation are small in humans with normal LV function, particularly when performed in the S orientation.