Characterizing Age Dependent Ultrasonic Properties of Zebrafish Embryos Using GHz Ultrasound Imaging

Zebrafish are a versatile vertebrate animal model that serves science, biomedical, and the pharmaceutical industry in gaining insights into vertebrate development and helping develop drugs for diseases. This paper demonstrates the first results on imaging zebrafish embryos using GHz ultrasonic imaging using a CMOS-integrated GHz ultrasonic transmit/receive array. Zebrafish embryos are imaged on the imager to obtain their ultrasonic impedance across the embryo with 50um spatial resolution. Embryos are imaged intermittently up to 60-70 hpf (hours-post-fertilization). Gigahertz (1-2 GHz) ultrasonic pulses that are 100 nanoseconds wide penetrate through the thin chorion of the eggs into the fluid or the embryo tissue in contact with the chorion. The measurement of the complex reflection coefficients suggests that ultrasound impedance decreases over the growth period, matching the trend measured using mechanical force probes.