Spherical lesion formation in HIFU using robotic assistance for controlled focal point manipulation

Area of Science:

• Medical physics
• Robotics
• Biomedical engineering

Background:

• High-intensity focused ultrasound (HIFU) ablation typically creates elongated, cigar-shaped thermal lesions due to its inherent focal acoustic field.
• Controlling lesion shape is crucial for precise therapeutic interventions, particularly for targeting small, spherical tumors.

Purpose of the Study:

• To develop and validate a robot-assisted HIFU method capable of generating spherical thermal lesions.
• To investigate the influence of focal motion patterns on heat transfer and lesion morphology during HIFU ablation.

Main Methods:

• Simulations were performed to evaluate various motion models for their potential to alter heat transfer patterns.
• The Gaussian Random Motion (GRM) model was identified as optimal through simulations.
• A robotic arm was employed to implement the GRM model for HIFU ablation on bovine serum albumin (BSA) gels.
• Lesion sphericity was quantified and compared between the GRM method and conventional fixed-focus HIFU.

Main Results:

• The GRM model successfully generated nearly spherical thermal lesions in BSA gels, achieving an average sphericity of 0.85.
• Conventional fixed-focus HIFU ablation resulted in significantly elongated lesions with an average sphericity of 0.33.
• Experimental results validated the simulation findings, demonstrating the efficacy of focal motion in controlling lesion shape.

Conclusions:

• Robot-assisted focal motion, specifically using the GRM model, enables the generation of spherical thermal lesions with high precision.
• This technique offers a promising approach for non-invasive HIFU treatments targeting early-stage, small, spherical tumors.
• The findings pave the way for more targeted and effective HIFU therapies in clinical applications.