UCLA

In this dissertation a novel method for rapid quantification of left ventricular (LV) twist was developed, validated, and clinically evaluated. LV twist is defined as the difference in rotation of the apex relative to the base of the heart. Alteration in LV twist has been shown the correlate with LV dysfunction. Rotation was measured using Fourier Analysis of STimulated echoes (FAST), an image acquisition and rapid processing method. FAST can be applied to cardiovascular magnetic resonance (CMR) images with myocardial tagging, which imparts a sinusoidal pattern on the myocardial tissue that deforms with the LV during contraction and relaxation. First, FAST estimates of LV twist were validated using intra- and inter-observer comparison, intra- and inter-scan comparison, and comparison to values derived from a `gold-standard' technique. Second, FAST was used in conjunction with a CMR imaging technique designed to lengthen the duration of myocardial tag detection to acquire diastolic twist information. Third, FAST was applied to an imaging technique developed to minimize chemical shift induced myocardial tagging pattern artifacts, which produces more accurate measurements of LV twist. Fourth, FAST was used in combination with two free-breathing techniques to determine the impact of free-breathing on FAST estimates of LV twist. Fifth, FAST was used to characterize differences in LV twist in patients with moderate and severe mitral regurgitation. LV twist measurements derived from FAST showed good agreement for the intra- and inter-observer study and the intra- and inter-scan study. Additionally, systolic LV twist values matched well with the `gold-standard'. When used in combination with the improved myocardial tag duration, FAST estimates of diastolic LV twist matched well with literature values. LV twist derived from the normal imaging technique compared with the artifact minimizing technique did not detect any significant differences, however this study was performed in healthy subjects, specific patient populations may provide different results. The free-breathing study detected a significant decrease peak LV twist due to free-breathing compared with breath-held imaging derived values. A significant decrease in peak LV twist was detected in patients with moderate and severe mitral regurgitation. Overall, the FAST method for quantitative LV twist measurement has been validated and shown to produce accurate measurements of twist with limited user interaction.