A Fully MRI-Compatible, Non-Electrical System for Near Real-Time Tremor Monitoring During MR-guided Focused Ultrasound

Introduction: Tremor quantification during Magnetic Resonance-guided Focused Ultrasound (MRgFUS) for essential tremor (ET) remains a clinical challenge. Current methods, such as accelerometry, can still be limited by electromagnetic artefacts in certain cases, magnetic resonance imaging (MRI) incompatibility, and indirect correlation with sonication timing. We aimed to develop a fully MRI-compatible, non-electrical system capable of continuous, electromagnetically artefact-free tremor monitoring with near real-time frequency analysis, precisely synchronized with ultrasound delivery. The primary purpose of this tool is to assist with targeting during the verification stage by providing the tremor amplitude in situ. Methods: We designed a pneumatic device using a standard, easily available endotracheal cuff inflated to a fixed pressure, held by the patient during MRgFUS sonications. Tremor-induced pressure fluctuations were transmitted outside the MRI suite and digitized using a custom Arduino-based system. A software tool was implemented to calculate the tremor amplitude in near real-time. Results: The pressure system allowed real-time visualization of the tremor and assessment of the tremor reduction at the verification stage of 10 patients. The mean tremor reduction was 86% immediately after the end of the verification sonication, confirming the correct position of the target. All patients had a lesion at this location except one, in which the target was moved because he experienced sensory side effects. Conclusion: We designed and implemented a near real-time pressure system for quantification of the tremor amplitude during sonications. The inexpensive and MR-compatible device is easy to implement on patients requiring MRgFUS treatments and avoid the possible loss of information between the temporary tremor reduction and the clinical evaluation.