Acceleration of tissue phase mapping by k-t BLAST: a detailed analysis of the influence of k-t-BLAST for the quantification of myocardial motion at 3T

Abstract

Background: The assessment of myocardial motion with tissue phase mapping (TPM) provides high spatiotemporal resolution and quantitative motion information in three directions. Today, whole volume coverage of the heart by TPM encoding at high spatial and temporal resolution is limited by long data acquisition times. Therefore, a significant increase in imaging speed without deterioration of the quantitative motion information is required. For this purpose, the k-t BLAST acceleration technique was combined with TPM black-blood functional imaging of the heart. Different k-t factors were evaluated with respect to their impact on the quantitative assessment of cardiac motion.

Results: It is demonstrated that a k-t BLAST factor of two can be used with a marginal, but statistically significant deterioration of the quantitative motion data. Further increasing the k-t acceleration causes substantial alteration of the peak velocities and the motion pattern, but the temporal behavior of the contraction is well maintained up to an acceleration factor of six.

Conclusions: The application of k-t BLAST for the acceleration of TPM appears feasible. A reduction of the acquisition time of almost 45% could be achieved without substantial loss of quantitative motion information.

Figure 1

Anatomical and phase contrast images with and without k-t BLAST. Anatomical (left) images of the myocardium and respective velocity encoded phase images in AP, FH and RL directions for the conventional sequence and the k-t BLAST accelerated sequences (acceleration factors 2, 4 and 6, heart phase with maximum longitudinal velocity (approx. 50 ms after the R-Wave)

Figure 2

Velocity curves for different k-t accelerating factors and for the reproducibility study. In Figure 2 a) and b) the radial and longitudinal velocity curves of a healthy volunteer over the time after the R-peak are displayed for different k-t accelerations (kt-group). In c) and d) two velocity curves without k-t acceleration are displayed (reference group).