In Vivo Non-Thermal, Selective Cancer Treatment With High-Frequency Medium-Intensity Focused Ultrasound.

Area of Science:

• Biomedical Engineering
• Oncology
• Acoustic Therapy

Background:

• High-intensity focused ultrasound (HIFU) is a non-invasive cancer treatment but lacks specificity, causing damage to healthy tissues.
• Existing HIFU methods rely on extreme heat and cavitation, leading to low spatial resolution and potential side effects.

Purpose of the Study:

• To evaluate the therapeutic efficacy of pulsed, high-frequency, medium-intensity focused ultrasound (pHFMIFU) for selective cancer treatment.
• To assess pHFMIFU's ability to treat tumors without thermal damage or significant risk of inertial cavitation.

Main Methods:

• Utilized a microfabricated self-focusing acoustic transducer (SFAT) with a Fresnel lens to generate pHFMIFU (20.7 MHz).
• Employed a three-axis positioning system for automated scanning and a water-cooling system for transducer stability.
• Tested the treatment on an *in vivo* subcutaneous B16F10 melanoma tumor model in mice.

Main Results:

• pHFMIFU treatment maintained skin temperature below 35.6 °C, without damaging normal tissues.
• Treated tumors showed significant reduction in size with extensive necrosis and apoptosis compared to controls after eleven days.
• Achieved a focal diameter of 104 μm with low mechanical index (< 0.66), indicating minimal cavitation risk.

Conclusions:

• pHFMIFU demonstrates selective, non-thermal cancer cell killing effects in a melanoma model.
• This modality offers high spatial resolution and potential for safer cancer treatment, particularly in sensitive body regions.
• Further analysis of treatment variations and mechanisms could optimize pHFMIFU as a novel therapeutic option.