A simple 5-DoF MR-compatible motion signal measurement system

Area of Science:

• Biomedical Engineering
• Medical Imaging Technology
• Sensor Systems

Background:

• Simultaneous motion measurement and Magnetic Resonance (MR) imaging is challenging due to potential interference.
• Existing motion tracking systems may not be compatible with the strong magnetic fields and radiofrequency pulses used in MR scanners.
• Accurate motion data is crucial for various applications, including neurological studies and physical rehabilitation within an MR environment.

Purpose of the Study:

• To develop a simple, safe, and Magnetic Resonance (MR)-compatible motion measurement system.
• To enable the simultaneous acquisition of high-quality MR images and precise 5-Degrees of Freedom (5-DoF) motion data.
• To ensure the developed system does not interfere with the MR imaging process or compromise image integrity.

Main Methods:

• Utilized a sensor module with a three-axis accelerometer and a two-axis gyroscope for 5-DoF motion detection.
• Employed nonmagnetic materials for all electronic components within the MR environment to minimize interference.
• Implemented pulse width modulation to convert motion signals to optic signals for transmission outside the MR shielded room via an optic cable.
• Housed critical electronic components (amplifier, modulation circuit, power supply) in a shielded case to mitigate radiofrequency (RF) pulse interference.

Main Results:

• The developed system successfully measured 5-DoF motion signals without degrading MR image quality.
• No adverse effects were observed on the MR system's main magnetic field, gradient fields, RF coil, or RF pulse.
• Kinematic variables including angle, acceleration, velocity, and jerk were accurately measured or calculated.
• Motion tracking was achieved by extracting position information from the acquired motion signals.
• Simultaneous and reliable measurement of both MR images and motion signals was experimentally verified.

Conclusions:

• The developed motion measurement system is compatible with MR imaging environments.
• The system provides accurate kinematic data and enables motion tracking during MR scans.
• This technology facilitates simultaneous motion analysis and MR imaging, opening new avenues for research and clinical applications.