An Inexpensive Scanner-Independent Luminescent Motion Monitor for MRI
M Wahi-Anwar*, A Gearhart, D Little, J Rotella, S Lemieux, The Pennsylvania State University, University Park, PASU-E-I-75 Sunday 3:00PM - 6:00PM Room: Exhibit Hall
Purpose: To develop and test an inexpensive single-channel motion monitor to track and feedback information about patient movement in real-time.
Methods: The motion monitor utilizes an optical motion sensor to track patient movement. The components are a 2000 lumens light source, a light detector and an analog-to-digital converter that connects via USB to a computer. The InstaCal software directs the signal into the Matlab Data Acquisition Toolbox for processing. Fiber optic cables were used to transmit the light from the source and detector during an MRI scan. A movable cylindrical gel phantom, 11.4cm outer diameter and 15.2 cm length, was designed and constructed for testing, including inserts for geometric distortion and spatial resolution. Movement magnitude (2mm, 4mm, 6mm), and direction (roll, pitch, yaw) were varied. Dynamic echo-planar imaging (EPI), TR=2s, spatial resolution = 3mm x 3mm x 3mm, was performed on the gel phantom and human subjects to compare motion monitor results to results from motion correction software. Anatomical images were acquired, scantime 4 minutes, spatial resolution = 1mm x 1mm x 1mm, using magnetization-prepared rapid acquisition with gradient echo, MP-RAGE, to compare the effects of motion at 30 seconds versus motion at 2 minutes.
Results: Motion was viewable in real-time during monitor tests on the phantom that demonstrated sensitivity as small as 2mm. MPRAGE images with motion occurring closer to the center of k-space, at 2 minutes, showed more image distortion than those with motion near the edge of k-space, at 30 seconds. This was evident in both phantom trials and human trials.
Conclusion: The motion monitor developed was sensitive to movements larger than 2mm in both the test phantom and the human subjects. Adding sensors, positioned at different angles on the head, would boost the sensitivity of the motion monitor to a wider range of motions.