(Sunday, 7/12/2020) [Eastern Time (GMT-4)]
Room: AAPM ePoster Library
Purpose: To evaluate continuous 6D cranial motion detection using a novel capacitive monitoring technology. The system is sensitive to the motion of the cranium within the thermoplastic mask and not the mask itself. It is non-ionizing, modular, and provides near real-time cranial positioning information without relying on surrogates such as skin or requiring any modifications to the mask. Similar capacitive technology has been shown to detect translations accurately; this work examines the additional measurement of rotational motion.
Methods: The capacitive system includes a conductive sensor array in the shape of a ring, with inner and outer radii of 8 and 16 cm, at the vertex of the cranium. The sensor ring is divided into four quadrants (figure 1). Two volunteers were fitted with an S-frame thermoplastic mask. For each volunteer, the sensor array was located around the cranium positioned using a hexapod translational/rotational stage to simulate cranial motion. The array was translated and rotated by known amounts in 6D and the capacitance was readout continuously from all four sensors. A Spearman correlation matrix was populated for each motion and volunteer to classify motion type.
Results: Changes in signal were sufficient for sub-millimeter motion and sub-degree rotations and could be used for quantifying the motion once the direction of the motion was classified. Spearman correlation matrices were rounded to half integer values and the six degrees of motion were uniquely classified by determining five categories with the Spearman matrices. For both volunteers there was agreement for motion classification.
Conclusion: This novel technology permits sensing and classification of cranial motion in near real-time within the thermoplastic immobilization mask.
Funding Support, Disclosures, and Conflict of Interest: The authors report grants from Atlantic Canada Opportunities Agency (ACOA), and non-financial support from Brainlab AG, during the conduct of the study. In addition, the authors have a provisional patent application pending and a licensing agreement with Brainlab AG.
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