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Initial Phantom Evaluation of Varian Identify System SGRT Consistency and Accuracy

H Zhao*, V Sarkar , A Paxton , Y Huang , P Rassiah-Szegedi , M Szegedi , F Su , G Nelson , B Salter , University of Utah, Salt Lake City, UT


(Sunday, 7/14/2019) 4:30 PM - 5:00 PM

Room: Exhibit Hall | Forum 6

Purpose: To evaluate the consistency and accuracy of surface guided radiotherapy (SGRT) functionality of the Varian Identify system.

Methods: A phantom evaluation of the consistency and accuracy for Varian Identify SGRT was performed, including a system consistency test, a translational shift accuracy test, a rotational accuracy test, a continuous recording test, and a SGRT vs CBCT agreement test. All tests were performed on the pelvis section of a Rando phantom. In the consistency test, ten separate Identify SGRT-reported known offsets were tested, each at couch angles of 0, 90 and 270 degree. In the translational shift accuracy test, eight sets of known translational shifts of the treatment couch were compared to Identify SGRT-reported offsets at couch angles of 0, 45, and 315 degrees. In the rotational accuracy test, the couch rotation was compared with Identify SGRT for rotations up to 75 degree clockwise and counter-clockwise. In the continuous recording test, 25 minutes of continuous offsets were recorded, and the maximum variations with STD were calculated. In the SGRT vs CBCT agreement test, an end-to-end test was performed. The phantom setup was based on the DICOM CT surface contour generated in treatment planning system, and the verification CBCT was used to evaluate the surface setup accuracy.

Results: SGRT-reported shift consistency was within 0.1mm for translations and 0.05 degree for rotation. The translational shift accuracy was within 0.6mm, and the rotational accuracy was within 0.1 degree. In the continuous recording, the maximum variation was 0.2mm, 0.02 degree, and the STD was within 0.12mm, 0.01 degree. The difference between Identify SGRT offset and CBCT was within 1mm and 1 degree.

Conclusion: This phantom evaluation study showed overall SGRT consistency and accuracy of the Varian Identify system to be within 1mm and 1 degree, which is less than the 2mm criteria of TG147.


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