Quantitative Assessment of Head Motion toward Functional Magnetic Resonance Imaging during Stepping

Purpose: Stepping motions have been often used as gait-like patterns in functional magnetic resonance imaging (fMRI) to understand gait control. However, it is still very difficult to stabilize the task-related head motion. Our main purpose is to provide characteristics of the task-related head motion during stepping to develop robust restraints toward fMRI. Methods: Multidirectional head and knee position during stepping were acquired using a motion capture system outside MRI room in 13 healthy participants. Six phases in a stepping motion were defined by reference to the left knee angles and the mean of superior-inferior head velocity (V-mean ) in each phase was investigated. Furthermore, the correlation between the standard deviation of the knee angle (theta(sd)) and the maximum of the head velocity (V-max) was evaluated. Results: The standard deviation of each superior-inferior head position and pitch were significantly larger than the other measurements. V-mean showed a characteristic repeating pattern associated with the knee angle. Additionally, there were significant correlations between theta(sd) and V-max. Conclusions: This is the first report to reveal the characteristics of the task-related head motion during stepping. Our findings are an essential step in the development of robust restraint toward fMRT during stepping task.