(Sunday, 7/12/2020) [Eastern Time (GMT-4)]
Room: AAPM ePoster Library
Purpose:
Frameless stereotactic radiosurgery (SRS) requires dedicated systems to monitor patient’s motion to avoid inaccurate radiation delivery due to involuntary shift. The purpose of this study is to assess the accuracy and sensitivity of two motion monitoring systems used for frameless SRS.
Methods:
A surface imaging guided system as Optical Surface Monitoring System (OSMS), and fiducial marker based system as High Definition Motion Management (HDMM) system in the latest Gamma Knife Icon® were compared. A 3D printer based cranial motion phantom was developed to evaluate the accuracy and sensitivity of these two systems in terms of: (1) the capability to recognize predefined shifts up to 3cm, and (2) the capability to recognize predefined speed up to 3cm/s. The performance of OSMS by choosing different reference surfaces was also evaluated.
Results:
Translational motion could be accurately detected by both systems, with an accuracy of 0.3mm for displacement up to 1cm, and 0.5mm for larger displacements. The reference surface selection had impact on OSMS performance with flat surface presenting less accuracy. HDMM is in general more sensitive compared to OSMS in capturing the movement due to faster frame speed, but a delay response was observed with faster speed. Both systems were less sensitive to detect superior-inferior motion compared to lateral or vertical displacement.
Conclusion:
Translational motion can be accurately and sensitively detected by OSMS and HDMM real-time monitoring systems. But the performance variations were observed along different directions, or selection of reference images. Cautions are needed when using real-time monitoring system for frameless SRS treatment.
Innovation: The transition from frame to frameless immobilization is a paradigm shift in SRS, particularly in the GK community. However, there is still limited data regarding tracking accuracy of non-ionizing infrared camera based motion management systems. In addition, the newly developed systems use different principles to monitor motion, as the HDMM used in GK Icon is a single fiducial based tracking platform while OSMS is a surface imaging based system. Both systems allow sub-millimeter tracking, yet the sensitivity in detecting patient motion may be different. Thus in this study, we aim to assess the position and speed accuracy and sensitivity of two motion monitoring systems used for frameless stereotactic treatment using a 3D-printer based movable head phantom.
Key findings: It showed both systems can achieve sub-millimeter accuracy in measuring linear motion in general. But the positioning accuracy in Y-direction (S-I) for OSMS forehead monitoring (0.8±0.5mm) was poorer than OSMS nose (0.3±0.2mm, p=0.01*) and HDMM (0.1±0.2mm, p<0.001*) monitoring. Both systems were also able to detect sudden changes of the motion with minimal time delay. But if motion speed was beyond 20mm/s along Y-direction (S-I), OSMS was relatively insensitive in detecting the motion.
Keywords
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Taxonomy
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