Development of an ultrasonic nonlinear frequency compounding method with applications in tissue thermometry.

Area of Science:

• Ultrasound imaging
• Biomedical engineering
• Medical physics

Background:

• Ultrasound imaging techniques are crucial for medical diagnostics.
• Improving signal-to-noise ratio (SNR) enhances image clarity and diagnostic accuracy.
• Noninvasive tissue thermometry requires precise temperature monitoring during procedures.

Purpose of the Study:

• To introduce and investigate a novel nonlinear frequency compounding (NLFC) method for ultrasound imaging.
• To assess the efficacy of NLFC in noninvasive tissue thermometry by mapping temperature-sensitive changes.
• To compare the SNR performance of NLFC against the traditional nonlinear single frequency (NLSF) method.

Main Methods:

• Developed and applied the NLFC method to generate 2D maps of temperature-sensitive change in backscattered energy of acoustic harmonics (hCBE).
• Heated ex vivo porcine tissue using a low-intensity focused ultrasound transducer.
• Performed hCBE-to-temperature calibration and compared resulting temperature maps with a COMSOL-based model.

Main Results:

• The NLFC method achieved a superior SNR of 6.06 ± 1.28.
• The NLSF method yielded lower SNRs of 3.70 ± 0.53 (at 4.31 MHz) and 4.38 ± 0.84 (at 5.43 MHz).
• NLFC demonstrated a significant SNR improvement of 64.13% over 4.31 MHz NLSF and 38.72% over 5.43 MHz NLSF.

Conclusions:

• The NLFC method provides enhanced hCBE and temperature maps with significantly improved image SNR.
• NLFC offers a more effective approach for noninvasive tissue thermometry compared to NLSF.
• This advancement holds potential for more accurate ultrasound-based temperature monitoring in medical applications.