Ultrasonic attenuation and absorption in liver tissue.

Area of Science:

• Biomedical Ultrasound
• Acoustics
• Tissue Optics

Background:

• Discrepancies exist in reported ultrasonic attenuation and absorption coefficients for biological tissues.
• Distinguishing true ultrasonic absorption (energy conversion to heat) from total attenuation is crucial for theoretical and practical applications.

Purpose of the Study:

• To investigate and quantify ultrasonic attenuation and absorption coefficients in bovine liver.
• To determine the relative contributions of absorption and other attenuation mechanisms in liver tissue.

Main Methods:

• Total ultrasonic attenuation was measured in bovine liver across the 1-6 MHz frequency range using phase-sensitive and phase-insensitive insertion loss techniques.
• Ultrasonic absorption coefficients were determined using two thermal methods: the transient thermoelectric (rate-of-heating) method and a novel temperature decay measurement post-ultrasonic pulse.

Main Results:

• Ultrasonic amplitude attenuation and absorption coefficients in bovine liver were found to be not significantly different at low megahertz frequencies.
• Mean values for both coefficients clustered around 0.05 nepers/cm/MHz (0.4 dB/cm/MHz).
• Sample-to-sample variation was minimal, with a standard deviation of 0.01 nepers/cm/MHz (0.09 dB/cm/MHz) or less.

Conclusions:

• In the studied frequency range (1-6 MHz), ultrasonic absorption is the dominant factor contributing to the total attenuation in liver tissue.
• The findings suggest that absorption accounts for most of the ultrasonic signal loss in liver within this frequency spectrum.