Using the Tissue Impulse Response Function to Streamline Fractionated MRgFUS-Induced Hyperthermia

Area of Science:

• Oncology
• Medical Physics
• Biomedical Engineering

Background:

• Combining radiation therapy with hyperthermia, particularly MR-guided focused ultrasound (MRgFUS), can improve cancer treatment outcomes.
• Current MRgFUS applications are mainly ablative, and frequent MRI guidance increases costs and complexity.
• A streamlined workflow is needed to integrate MRgFUS hyperthermia more efficiently into radiation therapy.

Purpose of the Study:

• To develop and validate a simplified workflow for repeated MRgFUS hyperthermia treatments.
• To reduce reliance on continuous MRI thermometry feedback during treatments.
• To optimize acoustic power settings in advance using an impulse response function (Green's function) approach.

Main Methods:

• Implemented the Green's function approach in a perfused phantom simulating tissue for MRgFUS hyperthermia delivery.
• Conducted 30 experiments using pre-calculated acoustic power settings for stable temperature control.
• Performed retrospective analysis of patient thermometry data to assess clinical applicability and robustness.

Main Results:

• Achieved consistent, stable hyperthermia (+7 °C for 15 min) across varied perfusion rates in phantom experiments.
• Demonstrated superior temperature stability compared to conventional closed-loop MRI feedback methods.
• Confirmed the method's noise robustness and clinical applicability through retrospective patient data analysis.

Conclusions:

• The off-line Green's function approach simplifies MRgFUS hyperthermia integration into cancer treatment.
• This method has the potential to significantly reduce treatment costs and logistical challenges.
• Findings support broader adoption of MRgFUS hyperthermia as an adjuvant therapy in oncology.