Graduate Thesis Or Dissertation

 

Vernier Picket Fence Test : A Non-Imaging Method to Localize the Radiation Isocenter with Submillimeter Accuracy Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/js956k89q

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  • Vernier Picket Fence (VPF) offers a method to achieve submillimeter accuracy for aligning the QA phantom to the radiation isocenter without the use of x-ray imaging. VPF tests are read similarly to vernier calipers. The maximum detector signal determines the optimal matching between MLC defined dose strips and detector positions. A Gaussian function was used to fit signals from multiple detectors so that the optimal position can be solved iteratively. In order to evaluate the accuracy of the VPF test, the couch was shifted in a sequence of positions where VPF tests were performed to determine the couch positions in two dimensions on the Sun Nuclear MapCheck® (Melbourne, FL) device. The VPF was delivered at 0° gantry angle with 0° and 90° collimator angles to determine the lateral and longitudinal coordinates, respectively. Each position was also verified using ExacTrac® (Feldkirchen, Germany) to track the couch positions by infrared camera. To achieve three- dimensional capabilities, additional fields at 90° and 270° gantry angles were delivered on the Sun Nuclear ArcCheck® (Melbourne, FL) to determine the vertical direction, while accounting for the geometrical corrections of the diode distribution in the phantom. The radiation isocenter can be identified with up to 0.02 mm accuracy. The results from the VPF tests were compared with ExacTrac® to evaluate the accuracy with a difference of 0.3±0.055 mm laterally and 0.5±0.041 mm longitudinally. Results from the ArcCheck® also verify that the VPF test can be applied in all three directions, with a resolution of 1 cm from the detector spacing. Overall, VPF tests can achieve submillimeter positioning accuracy for QA phantom setup in three-dimensions. The systematic difference found may be attributed to initial setup error. Standard deviations are small, suggesting that results from infrared tracking and VPF tests are highly reproducible.
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  • description.provenance : Approved for entry into archive by Julie Kurtz(julie.kurtz@oregonstate.edu) on 2016-01-20T18:43:24Z (GMT) No. of bitstreams: 1 Jennifer Wong Thesis.pdf: 5088222 bytes, checksum: b5a4970292c759312016722ef600c797 (MD5)
  • description.provenance : Submitted by Jennifer Wong (wongjen@oregonstate.edu) on 2016-01-18T23:26:26Z No. of bitstreams: 1 Jennifer Wong Thesis.pdf: 5088222 bytes, checksum: b5a4970292c759312016722ef600c797 (MD5)
  • description.provenance : Made available in DSpace on 2016-01-25T22:57:10Z (GMT). No. of bitstreams: 1 Jennifer Wong Thesis.pdf: 5088222 bytes, checksum: b5a4970292c759312016722ef600c797 (MD5) Previous issue date: 2015-10-22
  • description.provenance : Approved for entry into archive by Laura Wilson(laura.wilson@oregonstate.edu) on 2016-01-25T22:57:10Z (GMT) No. of bitstreams: 1 Jennifer Wong Thesis.pdf: 5088222 bytes, checksum: b5a4970292c759312016722ef600c797 (MD5)
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  • 2017-08-23 to 2018-02-13

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