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KMID : 1164220120240020115
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Journal of Korean Society for Radiotherapeutic Technology
2012 Volume.24 No. 2 p.115 ~ p.121
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Evaluation on the Accuracy of the PPS in the Proton Therapy System, Which Uses the Self Made QA Phantom
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Lee Ji-Eun
Kim Jae-Won
Kang Dong-Yun
Choi Jae-Hyock
Youm Doo-Seok
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Abstract
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Purpose: The process of the proton treatment is done by comparing the DRR and DIPS anatomic structure to find the correction factor and use the PPS to use this factor in the treatment. For the accuracy of the patient set up, the PPS uses a 6 axis system to move. Therefore, there needs to be an evaluation for the accuracy between the PPS moving materialization and DIPS correction factor. In order to do this, we will use a self made PPS QA Phantom to measure the accuracy of the PPS.
Materials and Methods: We set up a PPS QA Phantom at the center to which a lead marker is attached, which will act instead of the patient anatomic structure. We will use random values to create the 6 axis motions and move the PPS QA Phantom. Then we attain a DIPS image and compare with the DRR image in order to evaluate the accuracy of the correction factor.
Results: The average correction factor, after moving the PPS QA Phantom’s X, Y, Z axis coordinates together from 1∼5 cm, 1 cm at a time, and coming back to the center, are 0.04 cm, 0.026 cm, 0.022 cm, 0.22o, 0.24o, 0o on the PPS 6 axis. The average correction rate when moving the 6way movement coordinates all from 1 to 2 were 0.06 cm, 0.01 cm, 0.02 cm, 0.1o, 0.3o, 0o when moved 1 and 0.02 cm, 0.04 cm, 0.01 cm, 0.3o, 0.5o, 0o when moved 2.
Conclusion: After evaluating the correction rates when they come back to the center, we could tell that the Lateral, Longitudinal, Vertical were all in the acceptable scope of 0.5 cm and Rotation, Pitch, Roll were all in the acceptable scope of 1°. Still, for a more accurate proton therapy treatment, we must try to further enhance the image of the DIPS matching system, and exercise regular QA on the equipment to reduce the current rate of mechanical errors.
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KEYWORD
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proton therapy, PPS, DIPS, correction factor
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