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KMID : 1164220190310020033
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Journal of Korean Society for Radiotherapeutic Technology
2019 Volume.31 No. 2 p.33 ~ p.41
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Study of overlapping setting up of Planning Target Volume for Improving Target Coverage adjacent Organ At Risk
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Lee Jung-Woong
Kim Bo-Kyum
Mun Jun-Ki
Woo Hun
Lee Yang-Hoon
Jeon Chang-Woo
Lee Jea-Hee
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Abstract
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Purpose: The purpose of this study is to improve the reduction of coverage of PTVs adjacent to organ at risk (OAR) by setting up overlapping Planning Target Volume (PTV) during Volumetric Modulated Arc Therapy(VMAT). Materials and
Methods: In patients who received Whole Brain, Gall Bladder and Rectum radiation therapy, We compared the cover change, maximum dose, Homogenicity Index and Conformity Index of PTV and also compared the maximum dose and average dose change of Organ At Risk by organizing treatment plans that are not applied overlaped PTV and treatment plans that are applied overlaped PTV in areas where coverage is insufficient.
Results: overage of treatment plans with overlapping PTVs was increased in all patients, and overall coverage was also increased in each of the four patients. The maximum dose for PTV was increased in five patients, and the Homogenicity Index and Conformity Index for all patients did not differ much. The maximum dose of the lens was increased by 1.12 times, and the maximum dose was decreased in two patients for brain stem. The mean dose of the eyeball was increased by a maximum of 1.15 times, and there was no significant difference between both parotid gland. In case of gallbladder cancer patients, the mean dose in the liver and colon was decreased, and the mean dose in the duodenum was increased. In the case of rectal cancer patients, the mean dose was reduced for both femur and bladder set as OARs. The overall MU was shown to be similar in four patients, excluding one.
Conclusion: If the critical dose of OAR is considered and used properly, I think it is a useful way to improve coverage of PTV.
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KEYWORD
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Volumetric Modulated Arc Therapy, Irregular shape target, Overlaped PTV, coverage, Organ at risk
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