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Session: Multi-Disciplinary General ePoster Viewing [Return to Session]

Head Motion Tracking for Frameless Stereotactic Radiosurgery Using MR-Compatible 1D Lidar

B Boroomandisorkhabi*1, S Montazeri1, T Kim2, M Esmaeelpour1, (1)Missouri University of S&T, Rolla, MO, (2)Washington University in St. Louis, Saint Louis, MO


PO-GePV-M-280 (Sunday, 7/10/2022)   [Eastern Time (GMT-4)]

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Purpose: Head motion management is critical in frameless stereotactic radiosurgery (SRS). Optical tracking on the skin is restricted by thermoplastic masks and the detected signal may not appreciate real scull motion. In the study, we proposed MR-compatible optical solution working underneath the thermoplastic masks for SRS workflow including MRI.

Methods: We developed a motion detection system using one dimensional (1D) Light Detection and Ranging (Lidar) based on optical fiber with MR compatibility. This system is using a 1550 nm ultrafast laser with a pulse duration of 7 ps at 10 MHz repetition rate, the scattered signal is then coupled back into a fiber-based interferometer, amplified, and passed through dispersion compensating fiber and detected by a 45 GHz photodetector connected to a 12 GHz oscilloscope. The back-reflected light that couples back to the system travels a longer distance and therefore has a delay compared to the reference arm. This different in time-of-flight of the pulse allows for detection of object’s motion.

Results: The proposed sensor is stand-alone, real-time, and cost-effective with several orders of magnitude higher resolution than the existing technologies. We are targeting 500-micron resolution for clinical applicability. Because it is only a fiber, it also introduces negligible attenuation during stereotactic radiotherapy. A resolution of 0. 1 mm is achieved for this system.

Conclusion: We developed an all-fiber 1D Lidar system at 1550 nm and demonstrated detection of head motion with high resolution and accuracy for SRS by applying the Lidar system. This system has a small size and electromagnetic immune that makes it compatible with MRI. Such an all-fiber motion detection system will influence the field of biomedical imaging in general and brain imaging in particular in addition to SRS.


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