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KMID : 1164220220340010043
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Journal of Korean Society for Radiotherapeutic Technology
2022 Volume.34 No. 1 p.43 ~ p.50
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A Comparative Evaluation of Dosal Usefulness in Total Scalp Irradiation according to Treatment Plans and Methods
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Park Byeal-Nim
Jung Dong-Min
Kwon Yong-Jae
Cho Yong-Wan
Kim Se-Young
Park Kwang-Soon
Park Ryeong-Hwang
Baek Jong-Geol
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Abstract
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Objective: The purpose of this study is to choose a treatment plan and equipment to maximize tangential irradiation to protect the normal brain tissues as much as possible during total scalp irradiation.
Subjects and Methods: After zoning the total scalp of a phantom and selecting a target area for treatment, the study made a Helical TomoTherapy(HT) plan, a Helical TomoTherapy with a Complete Block(HTCB) plan, and a Volumetric Modulated Arc Therapy(VMAT) plan. All of these plans made sure that the volume of a treatment plan with 95% of a prescription dose(40 Gy) would not exceed 95% of the entire volume and that Dmax would not be more than 110% of the prescription dose. The therapy plans compared doses among organs at risk of damage including the brain. Doses in the brain tissues were assessed based on the volumetric criteria for normal tissues in Emami et al.
Results: HT, HTCB, and VMAT had a dose of 21.68 Gy, 13.75 Gy, and 20.89 Gy, respectively, in brain tissues at D33%, a dose of 7.06 Gy, 3.21 Gy, and 7.84 Gy, respectively, at D67%, and a dose of 3.14 Gy, 1.75 Gy, and 3.84 Gy, respectively, at D100%. They recorded a Dmean of 16.64 Gy, 11.78 Gy, and 16.64 Gy, respectively. These results show that the overall dose was low in the HTCB plan. When the volume of a low dose was calculated based on 5 Gy, they recorded 87%, 49%, and 96%, respectively, in V5Gy. In addition, the maximum dose in the remaining organ(brain stem, hippocampus, and both lenses) except for the optic pathway was the lowest in HTCB
Conclusion: The findings demonstrate that TomoTherapy with a complete block minimized a dose in organs at risk of damage including the brain and hippocampus on both sides and accordingly reduced the probability of side effects such as radiation-induced brain injuries and a resulting decrease in neurocognitive functions. In addition to total scalp irradiation, if additional studies on ring targets treated in various areas are conducted to establish the benefits of tangential irradiation, it is believed that TomoTherapy using Complete Block can be used to maximize tangential irradiation in treatment planning.
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KEYWORD
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Total scalp irradiation, Helical TomoTherapy, Complete Block, Volumetric Modulated Arc Therapy
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