In Vivo Cardiac Imaging of Adult Zebrafish Using High Frequency Ultrasound (45-75 MHz)

Abstract

The zebrafish has emerged as an excellent genetic model organism for studies of cardiovascular development. Optical transparency and external development during embryogenesis allow for visual analysis in the early development. However, to understand the cardiovascular structures and functions beyond the early stage requires a high-resolution, real-time, noninvasive imaging alternative due to the opacity of adult zebrafish. In this research, we report the development of a high frequency ultrasonic system for adult zebrafish cardiac imaging, capable of 75 MHz B-mode imaging at a spatial resolution of 25 microm and 45 MHz pulsed-wave Doppler measurement. The system allows for real-time delineation of detailed cardiac structures, estimation of cardiac dimensions, as well as image-guided Doppler blood flow measurements. In vivo imaging studies showed the identification of the atrium, ventricle, bulbus arteriosus, atrioventricular valve and bulboventricular valve in real-time images, with cardiac measurement at various stages. Doppler waveforms acquired at the ventricle and the bulbus arteriosus demonstrated the utility of this system to study the zebrafish cardiovascular hemodynamics. This high frequency ultrasonic system offers a multitude of opportunities for cardiovascular researchers. In addition, the detection of E-flow and A-flow during the ventricular filling and the appearance of diastolic flow reversal at bulbus arteriosus suggested the functional similarity of zebrafish heart to that of higher vertebrates.

High-Resolution Tissue Doppler Imaging of the Zebrafish Heart During Its Regeneration

“…14,28 Under normal conditions most of the blood will fill the ventricle during early diastole in the human heart. Thus, the E-wave peak velocity is larger than the A-wave velocity, which means that the E/A ratio is larger than 1 for the normal human heart.…”

“…Although such an array system can provide a high imaging frame rate for the cardiac imaging of small animals, the use of higher frequency ultrasound would improve the image resolution. 14 The heart of the adult zebrafish is smaller than 1.5 · 1.5 · 1.5 mm 3,15 and so the ultrasound frequency needs to be higher than 75 MHz to provide sufficient resolution for imaging the detailed heart structures according to the suggestions from previous studies. 14,16 Array transducers operating at frequencies higher than 50 MHz are not available, but a singleelement transducer system based on mechanical scanning is still an option for zebrafish heart imaging.…”

“…14 The heart of the adult zebrafish is smaller than 1.5 · 1.5 · 1.5 mm 3,15 and so the ultrasound frequency needs to be higher than 75 MHz to provide sufficient resolution for imaging the detailed heart structures according to the suggestions from previous studies. 14,16 Array transducers operating at frequencies higher than 50 MHz are not available, but a singleelement transducer system based on mechanical scanning is still an option for zebrafish heart imaging. An 80-MHz duplex echocardiography system based on mechanical scanning has been built in our laboratory for obtaining high-frame-rate color Doppler images of the zebrafish heart.…”

Three-Dimensional (3D) Visualisation of the Cardiovascular System of Mouse Embryos and Fetus

“…They are either optimised for diagnosing pathologies in humans (computed tomography (CT), magnetic resonance imaging (MRI), ultrasound (US), single photon emission computed tomography (SPECT), positron emission tomography (PET)), for in vivo analysis of -often transparent -model animals [23][24][25][26][27][28][29][30][31][32], or for post-mortem analyses of entire biological specimens and biological tissue samples, on the molecular, subcellular, cellular, tissue, and organ system level (atomic force microscopy, electron microscopy, confocal imaging, optical projection tomography (OPT), episcopic imaging techniques, histological sectioning, micro-MRI, micro-CT, near infrared imaging techniques, polarised light spectroscopy, optical coherence tomography (OCT)). Not all of these techniques permit 3D imaging of the developing cardiovascular system of unborn mice.…”

Cardiac parameters analysis for zebrafish heart regeneration based on high frequency ultrasound imaging

“…Recently, high-frequency ultrasonic imaging system has been used in the zebrafish heart study, and the results significantly improved delineation of detailed cardiac structures and accurate estimation of cardiac dimensions [4].…”