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Effects of Rotation On Synchrony Single-Fiducial Tracking System

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Z Christ

Z Christ1*, C Shang2 , G Gibbard3 , J Cole4 , (1) ,,,(2) Boca Raton Regional Hospital, Boca Raton, FL, (3) Florida Atlantic University, Boca Raton, FL, (4) Boca Raton Community Hospital, Wellington, FL


SU-I-GPD-J-17 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To investigate the effects of rotation of a respiratory phantom on Synchrony respiratory motion tracking using a single fiducial.

Methods: Tumor tracking using a single fiducial is limited to linear chasing. However, rotation of gold fiducial on 64x64x64mm cube can be detected using single fiducial tracking. A mini-ball cube was loaded with three gold ficuials. Mini-ball was subject to 1cm amplitude longitudinal motion inside QUASAR respiratory motion phantom and tracked using Synchrony respiratory motion tracking using a single-fiducial. Phantom was imaged using kV rays from two orthogonal sources above treatment couch. Synchrony model was created for motion of fiducial with given uncertainty. Uncertainty in model was recorded for different rotational orientations of phantom 0-90 degrees CW in yaw direction. Measurements were repeated multiple times of three days. End-to-End test was performed indicating uncertainty greater than 40% resulted in planned/delivered dose disagreement >1mm.

Results: Uncertainty in model was seen to increase as angle increased, especially between 20 and 60 degrees. Table 1. Rotational effect on the uncertainty of single-fiducial based tracking model.Yaw Angle Uncertainty SDdegree % % 0 18.9 0.7 10 19.4 0.5 20 23.5 1.9 30 30.3 0.4 40 40.6 0.9 45 45.2 0.6 50 50.6 0.9 60 57.9 0.1 70 62.5 0.3 80 64.1 0.6 90 63.9 0.6The uncertainties (x, %) of the model can also be presented as a function of rotations (y, degree) between 0 and 90 degrees: y = -0.0002x3 + 0.0262x2 - 0.1726x + 18.638R² = 0.998

Conclusion: Yaw rotational deviations affect the uncertainty of the Synchrony model when single fiducial tracking is employed. Such a reported uncertainty by the software provides useful index and enhances the accuracy of the treatment delivery.

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