Regional myocardial strain measurements from 4DCT in patients with normal LV function

Background: CT SQUEEZ is a new automated technique to evaluate regional endocardial strain by tracking features on the endocardium from 4D cine CT data. The objective of this study was to measure the range of endocardial regional strain (RS_CT) values obtained with CT SQUEEZ in the normal human left ventricle (LV) from standard clinical 4D coronary CTA exams. Methods: RS_CT was measured over the heart cycle in 25 humans with normal LV function using cine CT from three vendors. Mean and standard deviation of RS_CT values were computed in 16 AHA LV segments to estimate the range of values expected in the normal LV. Results: Curves describing RS_CT vs. time were consistent between subjects. There was a slight gradient of decreasing minimum RS_CT value (increased shortening) from the base to the apex of the heart. Mean RS_CT values at end-systole were: base = −32% ± 1%, mid = −33% ± 1%, apex = −36% ± 1%. The standard deviation of the minimum systolic RS_CT in each segment over all subjects was 5%. The average time to reach maximum shortening was 34% of the RR interval. Conclusions: Regional strain (RS_CT) can be rapidly obtained from standard gated coronary CCTA protocols using 4DCT SQUEEZ processing. We estimate that 95% of normal LV end-systolic RS_CT values will fall between −23% and −43%; therefore, we hypothesize that an RS_CT value higher than −23% will indicate a hypokinetic segment in the human heart.