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A Potential Real Time AQA for Cyberknife Cones and MLC Based Treatments

S Khanal

C Shang1 , G Gibbard2 , J Cole3 , A Schramm4 , T Leventouri5 , S Khanal6*, (1) Boca Raton Regional Hospital, Boca Raton, FL, (2) Florida Atlantic University, Boca Raton, FL, (3) Lynn Cancer Institute, Boca Raton, FL, (4) Lynn Cancer Institute, Boca Raton, FL, (5) Florida Atlantic University, Boca Raton, Florida, (6) Florida Atlantic University, Boca Raton, FL


SU-F-T-556 (Sunday, July 31, 2016) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose:To investigate the potential use of the Raven™ (LAP of America Laser Applications) for real time AQA of Cyberknife™ with InCise2 MLC (Accuray™ Medical).

Methods: At setup, the Raven was rotated 45° on which an Accuray™ AQA cube was positioned. Three different AQA plans for fixed cone, InCise2MLC, and a modified MLC plan were delivered repeatedly ten times. The additional shapes in modified AQA plan enable additional reproducibility checks for all the MLC pairs. During the test, the cube was aligned by imbedded fiducials and irradiated. The two angled radiation beams aimed center tungsten ball of the cube and projected 45° to phosphor screen and registered by a CCD camera of the Raven device. The centricity of the metal ball in the irradiated field was then analyzed using Matlab codes.

Results:For AP images, the average offsets of X, Y, and radial directions are 0.24 ± 0.04 mm, 0.25 ± 0.02 mm and 0.35 ±± 0.03 mm respectively for the cone; 0.34 ± 0.02 mm, 0.49 ± 0.04 mm and 0.60 ± 0.04 mm respectively for the MLC. For lateral images, they are 0.63 ± 0.05 mm, 0.11 ± 0.02 mm and 0.64 ± 0.04 mm respectively for the cone, 0.79 ± 0.08 mm, ₋0.23 ± 0.06 mm and 0.82 ± 0.09 mm respectively for the MLC. No inconsistent MLC shapes were found in the modified AQA group.

Conclusion:The results are consistent with clinically acceptable values (≤1mm from baseline). The results suggest the potential of replacement of the standard AQA test with the novel real-time Raven device for Cyberknife daily QA. The modified MLC based AQA provides a more comprehensive MLC daily QA capability. Further improvements in its resolution and automatic analyzing capability are warranted.

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