Room: Exhibit Hall | Forum 6
Purpose: Elektaâ€™s Gamma Knife Icon unit incorporates an intrafraction motion management system which enables treatment to be delivered in a gated fashion. Stationary reflectors are placed on the mask mount and a patient reflector is placed at the tip of the patientâ€™s nose. Baseline position is established during CBCT. Movement of the patient reflector outside a preset tolerance will trigger a beam hold. Once the patient reflector moves back to within tolerance, the treatment resumes. If the patient marker moves outside of the tolerance level more than 5 times or for 30 consecutive seconds during one shot, the treatment will pause. Although some regulatory jurisdictions require periodic quantitative assessments of the IFMM, we are unaware of a commercially-available tool with which to measure it. The purpose of this work was the design of a precision tool to assess the systemâ€™s ability to accurately detect movement, and to react appropriately to movements outside the tolerance level.
Methods: We utilized a commercially-available linear stage to precisely move the IFMMâ€™s patient reflector in each of the three orthogonal axes while observing the systemâ€™s reported movement. The operator then remotely moves the patient marker out of and back within tolerance during a shot, and observes the application or release of a beam hold. When the marker is moved more than five times during a single shot, or remains outside the tolerance level for 30 seconds, the system pauses.
Results: We have found the tool to be accurate to within 0.2mm versus the IFMM system, and that the system pauses when appropriate.
Conclusion: This simple tool can be used to assess both the accuracy and the gating function of the systemâ€™s infrared tracking system.