The Journal of Korean Society for Radiation Therapy (대한방사선치료학회지)

Korean Society for Radiation Therapy (대한방사선치료학회)
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A Comparative Evaluation of Dosal Usefulness in Total Scalp Irradiation according to Treatment Plans and Methods

총 두피 방사선치료 시 치료계획 방법에 따른 선량적 유용성 비교 평가

  • Park byeal nim (Department Of Radiation Oncology, Yonsei University Yonsei Cancer Center) ;
  • Jung dong min (Department Of Radiation Oncology, Yonsei University Yonsei Cancer Center) ;
  • Kwon yong jae (Department Of Radiation Oncology, Yonsei University Yonsei Cancer Center) ;
  • Cho yong wan (Department Of Radiation Oncology, Yonsei University Yonsei Cancer Center) ;
  • Kim se young (Department Of Radiation Oncology, Yonsei University Yonsei Cancer Center) ;
  • Park kwang soon (Department Of Radiation Oncology, Yonsei University Yonsei Cancer Center) ;
  • Park ryeong hwang (Department Of Radiation Oncology, Yonsei University Yonsei Cancer Center) ;
  • Baek jong geol (Department Of Radiation Oncology, Yonsei University Yonsei Cancer Center)
  • 박별님 (연세암병원 방사선종양학과) ;
  • 정동민 (연세암병원 방사선종양학과) ;
  • 권용재 (연세암병원 방사선종양학과) ;
  • 조용완 (연세암병원 방사선종양학과) ;
  • 김세영 (연세암병원 방사선종양학과) ;
  • 박광순 (연세암병원 방사선종양학과) ;
  • 박령황 (연세암병원 방사선종양학과) ;
  • 백종걸 (연세암병원 방사선종양학과)
  • Published : 2022.12.31
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Abstract

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.

목 적: 총 두피 방사선치료 시 정상 뇌 조직을 최대한 보호할 수 있도록 접선조사를 극대화하는 치료계획 및 장비를 선정하고자 하였다. 대상 및 방법: 인체 모형에 총 두피를 구획하여 치료 부위를 설정하고, 나선형 토모테라피(Helical TomoTherapy, HT) 계획, Complete Block을 이용한 나선형 토모테라피(Helical TomoTherapy with Complete Block, HTCB) 계획 그리고 체적조절호형방사선치료(Volumetric Modulated Arc Therapy, VMAT) 계획을 수립하였다. 모든 치료계획은 처방 선량(40 Gy)의 95%가 들어가는 치료계획 용적이 체적의 95% 이상이 될 수 있도록, Dmax가 처방 선량의 110%를 넘지 않게 하였다. 치료계획은 뇌를 포함한 손상 위험 장기의 선량 비교를 실시하였으며 뇌 선량의 경우 Emami 등의 연구 결과의 정상조직 평가기준 체적을 참고하여 뇌 조직의 선량을 평가하였다. 결 과: HT, HTCB, VMAT 각각 뇌 조직 선량 D33%는 21.68 Gy, 13.75 Gy, 20.89 Gy, D67%는 7.06 Gy, 3.21 Gy, 7.84 Gy, D100%는 3.14 Gy, 1.75 Gy, 3.84 Gy, Dmean은 16.64 Gy, 11.78 Gy, 16.64 Gy로 HTCB plan에서 전반적으로 선량이 낮았으며, 저선량은 5 Gy를 기준으로 체적을 구하였을 때 V5Gy는 각각 87%, 49%, 96%로 나타났다. 이외의 시신경을 제외한 나머지(뇌줄기, 해마, 양측 안구)의 최대선량은 HTCB에서 가장 낮았다. 결 론: 토모테라피에서 Complete Block을 적용하였을 때 전체 뇌 조직의 선량 감소와 더불어 뇌에 포함된 양쪽 해마 등의 손상 위험 장기의 선량을 가장 최소화해 방사선 유도 뇌 손상의 발생과 그로 인한 신경인지 기능 감소 등에 대한 부작용의 확률을 줄일 수 있는 치료계획임을 확인하였다. 향후에는 총 두피 조사 이외에도 다양한 부위에 치료되는 고리 형태의 표적(Ring Target)에 대한 추가적인 연구를 진행하여 접선 조사에 대한 이점을 확립하게 된다면 치료계획 시 접선조사 극대화를 위해 Complete Block을 사용한 토모테라피를 적용함으로써 선량적으로 유용한 결과를 얻을 수 있을 것으로 사료된다.

Keywords

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