Finite element analysis of a capacitive array for 6D intrafraction motion detection during stereotactic radiosurgery

Area of Science:

• Medical Physics
• Radiotherapy Technology
• Biomedical Engineering

Background:

• Intrafraction cranial motion during radiotherapy can reduce treatment accuracy.
• Current motion monitoring methods may have limitations in precision or invasiveness.
• Accurate real-time tracking of six-degrees of freedom (DoF) cranial motion is crucial for adaptive radiotherapy.

Purpose of the Study:

• To develop and evaluate a non-contact, non-ionizing capacitive monitoring system for continuous intrafraction cranial motion detection.
• To assess the system's capability in detecting both translational and rotational cranial motion.
• To compare different capacitive sensor array designs for optimal six-DoF motion detection during radiotherapy.

Main Methods:

• Development of a modular capacitive monitoring system integrated with a thermoplastic mask.
• Utilizing finite element analysis (FEA) to model cranial motion and system capacitance.
• Validation of the FEA model using experimental data from human volunteers.
• Comparison of various capacitive array designs based on sensitivity and response uniqueness for six-DoF motion.

Main Results:

• The capacitive monitoring system demonstrated non-contact, continuous detection of cranial motion.
• FEA simulations accurately predicted system capacitance changes corresponding to simulated cranial translations and rotations.
• Multiple array designs were evaluated, identifying a most promising configuration for six-DoF motion detection.
• The validated FEA model facilitated the comparison and selection of optimal array designs.

Conclusions:

• A novel capacitive monitoring system offers a promising non-contact, non-ionizing solution for real-time six-DoF intrafraction cranial motion detection.
• The developed system, utilizing a thermoplastic mask, avoids the need for skin surrogates.
• The study successfully identified an optimal sensor array design for enhanced radiotherapy precision through accurate motion tracking.