High-Frequency Ultrasonic Properties of Freshwater Fish Tissue

Abstract

Various ultrasonic properties of whitefish (Coregonus dupeaformis) tissues have been determined. The sound velocity, impedance, and absorption were measured at 22°C with pulse echo techniques for the frequencies of 1, 2, 3, 7, and 11 MHz. The average impedance and absorption of fresh whitefish myomere with a fat content of approximately 8% were 1.634 × 105 cgs units and 0.7 dB/cm/MHz, respectively. No significant velocity or absorption anisotropy was observed for the muscle tissues. The effects of freezing on velocity and absorption were investigated. The mean velocity in thawed flesh was only 0.8% higher than in fresh flesh, but increases up to 100% or more were noted in the absorption. This increase depended on the rate at which freezing proceeded; a longer freezing period generally resulted in greater absorption.