Experimental brain hyperthermia: techniques for heat delivery and thermometry.

Area of Science:

• Neurosurgery
• Biomedical Engineering
• Thermal Medicine

Background:

• Accurate thermal ablation in the brain requires precise control of microwave antenna heating.
• Developing reliable animal models is crucial for testing new neurosurgical tools and techniques.
• Understanding antenna performance in biological tissue is essential for effective hyperthermia treatment.

Purpose of the Study:

• To develop and validate an experimental canine brain model for hyperthermia research.
• To evaluate the performance of various interstitial microwave antennas for creating targeted thermal lesions.
• To optimize antenna design and parameters for achieving specific lesion dimensions and characteristics in brain tissue.

Main Methods:

• Developed a canine brain model to assess hyperthermia effects at varying time and temperature endpoints.
• Evaluated six different microwave antennas (dipole, modified dipole, helical) in phantom and in vivo canine brains.
• Measured temperature profiles using fiberoptic probes and characterized specific absorption rate (SAR) and lesion dimensions via MRI and histology.

Main Results:

• Helical antennas demonstrated superior performance over dipole antennas, showing less sensitivity to insertion depth and frequency changes.
• A 2.0 cm coil length helical antenna at 915 MHz was selected for beagle experiments due to its favorable heating characteristics.
• Achieved well-defined, imagable lesions with blood-brain-barrier breakdown and necrotic zones, measuring 1.5-2.5 cm in diameter.

Conclusions:

• The developed canine brain model effectively supports the evaluation of microwave antenna performance for thermal lesion creation.
• Optimized helical antennas provide precise and localized heating for generating predictable thermal lesions in brain tissue.
• This research validates a method for controlled thermal ablation in the brain, paving the way for potential therapeutic applications.