Program Information
Real-Time Motion Management with Helical Tomotherapy
E Schnarr1*, D Henderson1 , M Beneke1 , D Casey1 , E Chao1 , J Chappelow2 , P Jordan2 , D Lucas1 , A Myronenko2 , C Maurer2 , (1) Accuray Incorporated, Madison, WI, (2) Accuray Incorporated, Sunnyvale, CA
Presentations
TH-AB-205-1 (Thursday, August 3, 2017) 7:30 AM - 9:30 AM Room: 205
Purpose: The CyberKnife® System is an established and proven device capable of real-time tracking and correction of respiratory target motion. In this study, we evaluate the potential for adapting this technology to a TomoTherapy® System.
Methods: We adapted the CyberKnife System’s respiratory motion tracking technology (Synchrony®) to an experimental tomotherapy system, and performed motion correction using the jaws and binary MLC: A kV flat-panel imaging system was added to an existing gantry, mounted 90 degrees offset from the MV treatment source, and an optical camera was mounted above the foot of the couch. This experimental system acquires a flat-panel image every few seconds to determine internal target positions, and correlates these positions with breathing amplitudes (external marker positions) detected continuously by the camera. Jaw positions and MLC leaf patterns are updated continuously, to reshape (effectively re-pointing) the treatment beam to follow the target motion. Jaw and MLC updates occur approximately every 10 ms, with only a few tens of milliseconds end-to-end latency.
Results: To measure the system's ability to correct for respiratory motion, we delivered a helical treatment plan to a small (1 cm diameter) moving target. A 3-axis robotic phantom was programmed to move following a breathing trace with superior-inferior motion of 15 mm. Film measurements were taken of the deliveries with and without motion management enabled, and compared against the planned (no motion) dose. Without motion correction, dose errors within the target of up to 19% were observed. With motion correction enabled, dose delivered to the target closely matched the planned dose.
Conclusion: Real-time respiratory motion management is technically feasible on an experimental tomotherapy system, with some hardware and software changes relative to systems currently on the market, enabling a high level of dose delivery accuracy to targets that move with respiration.
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