The changes in acoustic attenuation due to in vitro heating

Area of Science:

• Biophysics
• Medical Imaging
• Materials Science

Background:

• Ultrasound (US) attenuation in biological tissues is crucial for medical imaging.
• Thermal effects on tissue properties can alter US wave propagation.
• Understanding heat-induced changes in liver tissue is important for applications like thermal ablation.

Purpose of the Study:

• To investigate the impact of heat-generated changes on ultrasound attenuation in porcine liver tissue.
• To quantify the frequency-dependence of ultrasound attenuation changes after thermal exposure.
• To correlate observed attenuation changes with underlying tissue alterations, such as protein coagulation.

Main Methods:

• Porcine liver tissue samples (4-5 mm thick) were subjected to controlled heating (40-80°C for 30-500 s).
• Ultrasound insertion loss was measured using a broadband 3.5-MHz transducer before and after heating.
• Fourier analysis and linear regression were employed to determine frequency-dependent attenuation changes.

Main Results:

• Significant increases in ultrasound attenuation were observed, up to 2.4 dB/cm at 80°C for 300 s.
• The averaged data fitted a single-step exponential model with a time constant of approximately 118 ± 5 s.
• An asymptotic limit for the attenuation coefficient increase was determined to be 2.67 ± 0.5 dB/cm.

Conclusions:

• Heat-induced protein coagulation in liver tissue is the primary cause of increased ultrasound attenuation.
• The study provides quantitative data on the relationship between thermal dose and US attenuation changes in liver.
• Findings are relevant for optimizing thermal therapies and interpreting US imaging of heated liver tissue.