An analytical solution for improved HIFU SAR estimation.

Area of Science:

• Ultrasound Physics
• Biomedical Engineering
• Medical Imaging

Background:

• Accurate specific absorption rates (SARs) are crucial for comparing high intensity focused ultrasound (HIFU) studies and validating predictive software.
• Current methods for SAR determination from temperature data can have significant errors, impacting treatment planning and evaluation.

Purpose of the Study:

• To develop and test an analytical solution for significantly improving the accuracy of SAR values derived from HIFU temperature data.
• To provide a more reliable method for quantifying energy deposition in HIFU applications.

Main Methods:

• Developed an analytical solution by fitting a one-dimensional radial Gaussian heating pattern to temperature-time data after a power step.
• Evaluated the method's accuracy using parametric simulations and experimental validation in a tissue-mimicking phantom.
• Assessed performance against commonly used linear and exponential methods.

Main Results:

• The analytical method consistently yielded maximum errors of less than 10% at the focal zone center in simulations, outperforming linear (up to 90% error) and exponential (up to 55% error) methods.
• An extension of the analytical method maintained less than 10% error even at high perfusion rates.
• Experimental validation showed good agreement between predicted and measured temperature elevations.

Conclusions:

• The developed analytical method offers a significant improvement in SAR accuracy for HIFU applications.
• This enhanced accuracy is vital for reliable scientific comparison, software validation, and improved patient treatment planning in HIFU.
• The method is robust and validated both computationally and experimentally.