Click here to

Session: Therapy Radiotherapy Planning and Delivery [Return to Session]

High Definition Motion Management Safety Function Testing

Z Pham1*, C Ramsey1,2, K Skidmore1, J Bowling2, E Ross1, I Pfeiffer2, (1) University of Tennessee Knoxville, Knoxville, TN, (2) Thompson Cancer Survival Center, Knoxville, TN


WE-C1000-IePD-F7-3 (Wednesday, 7/13/2022) 10:00 AM - 10:30 AM [Eastern Time (GMT-4)]

Exhibit Hall | Forum 7

Purpose: The purpose of this study was to develop a technique for testing the accuracy and performance of the GammaKnife High Definition Motion Management (HDMM) system. The HDMM “Alarm” and “Pause” are automatic safety functions that are enabled when the patient moves beyond a user-defined threshold. The performance of this safety system and the accuracy of the HDMM log files were evaluated during delivery using a newly designed test tool.

Methods: A test tool was designed using a robotic actuator to move a patient tracking marker. This tool was used to test the performance of the HDMM system. The first test verified that an HDMM Pause would be automatically enabled during treatment if the marker was moved outside the HDMM limit for a given period of time. The second test verified that an HDMM Pause would be automatically enabled if the marker moved out of position five times in a single shot. The spatial accuracy of the HDMM log files was tested by moving the marker in 500-μm intervals in the X, Y, and Z directions.

Results: Testing of the spatial accuracy of the log files found that the HDMM system has an average positional accuracy of 80 microns. The average measured system noise was 16 microns. The HDMM pause automatically initiated 30 seconds after the actuator moved the marker out of position according to a stopwatch and the HDMM log files. Actuator testing also confirmed that the HDMM pause was automatically initiated after five HDMM alarms within the same shot using motion of the actuator.

Conclusion: A simple device and procedure were develop to test to HDMM safety system and log files on a GammaKnife Icon. These tests verified that the safety and HDMM systems are working as designed.


Gamma Knife, Patient Movement


TH- External Beam- Photons: Motion management - intrafraction

Contact Email