Automatic Definition of an Anatomic Field of View for Volumetric Cardiac Motion Estimation at High Temporal Resolution

Alejandra Ortega,Ling Tong,Jan D’Hooge,João Pedrosa,Brecht Heyde

doi:10.3390/app7070752

Abstract

Fast volumetric cardiac imaging requires reducing the number of transmit events within a single volume. One way of achieving this is by limiting the field of view (FOV) of the recording to the myocardium when investigating cardiac mechanics. Although fully automatic solutions towards myocardial segmentation exist, translating that information in a fast ultrasound scan sequence is not trivial. In particular, multi-line transmit (MLT) scan sequences were investigated given their proven capability to increase frame rate (FR) while preserving image quality. The aim of this study was therefore to develop a methodology to automatically identify the anatomically relevant conically shaped FOV, and to translate this to the best associated MLT sequence. This approach was tested on 27 datasets leading to a conical scan with a mean opening angle of 19.7° ± 8.5°, while the mean “thickness” of the cone was 19° ± 3.4°, resulting in a frame rate gain of about 2. Then, to subsequently scan this conical volume, several MLT setups were tested in silico. The method of choice was a 10MLT sequence as it resulted in the highest frame rate gain while maintaining an acceptable cross-talk level. When combining this MLT scan sequence with at least four parallel receive beams, a total frame rate gain with a factor of approximately 80 could be obtained. As such, anatomical scan sequences can increase frame rate significantly while maintaining information of the relevant structures for functional myocardial imaging.

Highlights

Over the last decades, volumetric cardiac ultrasound imaging has gained momentum as the modality of choice to assess cardiac morphology and visualize global heart motion [1]
We recently demonstrated that by small modifications of the transmit beamforming
The lines crossing the ventricular walls have the highest percentage of coverage while the ones crossing the apex have the lowest

Summary

Introduction

Volumetric cardiac ultrasound imaging has gained momentum as the modality of choice to assess cardiac morphology and visualize global heart motion [1]. (i.e., multi-line acquisition, MLA) [6]. This typically results in a frame rate of up to ~30 Hz when scanning with a moderate line density, when using a representative wide-angle field of view ~60◦ × ~ 60◦ ) and when gating is performed over four to six cardiac cycles. ECG gating lengthens the acquisition but can induce artefacts due to arrhythmias, breathing, motion or incorrect gating. A frame rate of 30 Hz for a 60◦ × 60◦ opening angle is adequate to evaluate.

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