Wide-Angle Tissue Doppler Imaging at High Frame Rate Using Multi-Line Transmit Beamforming: An Experimental Validation In Vivo.

Abstract

Color tissue Doppler imaging (TDI) is a well-established methodology to assess local myocardial motion/deformation. Typically, a frame rate of ∼ 200 Hz can be achieved by imaging a narrow sector (∼ 30°, covering one cardiac wall) at moderate line density, using a dedicated pulse sequence and multi-line acquisition. However, a wide angle field-of-view is required in some clinical applications to image the whole left ventricle, which implies a drop in temporal resolution. Hereto, the aim of this study was to propose a novel imaging sequence using a multi-line transmit (MLT) beamforming approach to achieve high frame rate color TDI while preserving a wide field-of-view (i.e., 90° sector). To this end, a color MLT-TDI sequence achieving a frame rate of 208 Hz with a 90°-sector was implemented on an ultrasound experimental scanner interleaved with a conventional color TDI sequence achieving the same frame rate but only with a 22.5°-sector. Using this setup, the septal wall of 9 healthy volunteers was imaged and the corresponding velocity was extracted. The M-mode velocity images and the velocity profiles obtained from the MLT-TDI images presented physiologic patterns, very similar to those from conventional TDI. Moreover, for the peak systolic/diastolic velocities, good agreement and strong correlation between MLT-TDI and conventional TDI were found. The results thus demonstrate the feasibility of the novel MLT based TDI methodology to achieve high frame rate color TDI without compromising the field-of-view. This may open the opportunity to simultaneously assess regional myocardial function of the whole left ventricle at high temporal resolution.