The Journal of Korean Society for Radiation Therapy (대한방사선치료학회지)

Korean Society for Radiation Therapy (대한방사선치료학회)
권호 표지

Evaluation of Dose Variation according to Air Gap in Thermoplastic Immobilization Device in Carbon Ion

탄소입자 치료 시 열가소성 고정기구의 공기층에 따른 선량 변화 평가

  • Ye-jin Na (Department of Radiation Oncology, Yonsei University Yonsei Cancer Center) ;
  • Ji-Won Jang (Department of Radiation Oncology, Yonsei University Yonsei Cancer Center) ;
  • Se-Wuk Jang (Department of Radiation Oncology, Yonsei University Yonsei Cancer Center) ;
  • Hyo-Kuk Park (Department of Radiation Oncology, Yonsei University Yonsei Cancer Center) ;
  • Sang-Kyu Lee (Department of Radiation Oncology, Yonsei University Yonsei Cancer Center)
  • 나예진 (연세암병원 방사선종양학과) ;
  • 장지원 (연세암병원 방사선종양학과) ;
  • 장세욱 (연세암병원 방사선종양학과) ;
  • 박효국 (연세암병원 방사선종양학과) ;
  • 이상규 (연세암병원 방사선종양학과)
  • Published : 2023.12.31
Download PDF
⟨ Previous Next ⟩

Abstract

Purpose: The purpose of this study is to find out the dose variation according to thickness of the air gap between the patient's body surface and immobilization device in the treatment plan. Materials and Methods : Four conditions were created by adjusting the air gap thickness using 5 mm bolus, ranging from 0 mm to 3 mm bolus. Immobilization was placed on top in each case. And computed tomography was used to acquire images. The treatment plan that 430 cGy (Relative Biological Effectiveness,RBE) is irradiated 6 times and the dose of 2580 cGy (RBE) is delivered to 95% of Clinical Target Volume (CTV). The dose on CTV was evaluated by Full Width Half Maximum (FWHM) of the lateral dose profile and skin dose was evaluated by Dose Volume Histogram (DVH). Result: Results showed that the FWHM values of the lateral dose profile of CTV were 4.89, 4.86, 5.10, and 5.10 cm. The differences in average values at the on the four conditions were 3.25±1.7 cGy (RBE) among D95% and 1193.5±10.2 cGy (RBE) among D95% respectively. The average skin volume at 1% of the prescription dose was 83.22±4.8%, with no significant differences in both CTV and skin. Conclusion: When creating a solid-type immobilization device for carbon particle therapy, a slight air gap is recommended to ensure that it does not extend beyond the dose application range of the CTV.

목 적: 환자 체표면과 고정기구 사이에 발생하는 공기층 두께에 따른 선량 변화를 치료 계획을 통해 알아보고자 한다. 대상 및 방법: 팬텀과 열가소성 고정기구 사이에 5 mm 두께의 Bolus를 0, 1, 2, 3장을 놓아 공기층의 두께를 조절하였고 고정기구를 씌워 총 4가지 조건으로 전산화 모의단층촬영을 시행하였다. 430 cGy (Relative Biological Effectiveness,RBE)씩 6번이 조사 되도록 계획하였으며, 임상표적체적의 95% 부피에 전달된 선량이 2580 cGy (RBE)가 되도록 치료 계획을 수립하였다. 임상표적체적의 선량은 Lateral dose profile의 반치폭값으로 평가하였고 피부 선량은 선량 체적 곡선으로 평가하였다. 결 과: 임상표적체적에서 Lateral dose profile 반치폭 값은 4.89, 4.86, 5.10, 5.10 cm로 나타났다. 피부에서 4가지 조건의 선량의 평균값은 D95%3.25±1.7 cGy (RBE), D30%1193.5±10.2 cGy (RBE)의 차이를 보였으며 처방 선량 1%에서의 피부 부피 값 평균은 83.22±4.8% 이내의 차이를 확인하였다. 공기층 두께 변화에 따른 임상표적체적과 피부에서의 선량 모두 큰 변화를 보이지는 않았다. 결론 : 탄소입자 치료를 위해 Solid 형태의 고정기구 제작 시 약간의 공기층은 CTV의 선량 적용 범위를 벗어나지 않는다.

Keywords

References

  1. Emami B, Lyman J, Brown A, et al.:Tolerance of normal tissue to therapeutic irradiation. International Journal of Radiation Oncology Biology Physics 1991;21:109-122 https://doi.org/10.1016/0360-3016(91)90171-Y
  2. Grau C , Durante M, Langendijk JA, et al.:Particle therapy in Europe. Molecular Oncology 2020;14:1492-1499. https://doi.org/10.1002/1878-0261.12677
  3. Karger CP, Peschke P, Sanchez-Brandelik R, et al.:Radiation tolerance of the rat spinal cord after 6 and 18 fractions of photons and carbon ions: Experimental results and clinical implications. International Journal of Radiation Oncology Biology Physics 2006;66:1488-1497. https://doi.org/10.1016/j.ijrobp.2006.08.045
  4. Weyrather WK, Ritter S, Scholz M, at al.:RBE for carbon track-segment irradiation in cell lines of differing repair capacity. International Journal of Radiation Biology 1999;75:1357-1364.
  5. Kanai T, Furusawa Y, Fukutsu K, et al.:Irradiation of mixed beam and design of spread-out Bragg peak for heavy-ion radiotherapy. Radiation Research 1997;147:78-85. https://doi.org/10.2307/3579446
  6. Phillips TL, Ross GY, Goldstei LS, et al.:In vivo radiobiology of heavy ions. International Journal of Radiation Oncology Biology Physics 1982;8:2121-2125. https://doi.org/10.1016/0360-3016(82)90555-7
  7. Karger CP, Glowa C, Peschke P, et al.:The RBE in ion beam radiotherapy: In vivo studies and clinical application. Zeitschrift fur Medizinische Physik 2021;31:105-121. https://doi.org/10.1016/j.zemedi.2020.12.001
  8. Mohamad O, Sishc BJ, Saha J, et al.:Carbon Ion Radiotherapy: A Review of Clinical Experiences and Preclinical Research, with an Emphasis on DNA Damage/Repair. Multidisciplinary Digital Publishing Institute Cancer Journal 2017;9:66.
  9. Nichiporov D, Moskvin V, Fanelli L, et al.:Range shift and dose perturbation with high-density materials in proton beam therapy. Nuclear Instruments and Methods in Physics Research B 2011;269:2685-2692. https://doi.org/10.1016/j.nimb.2011.07.109
  10. 김연래, 서태석, 고신관 등:공동(air cavity)의 존재 시 실험적 선량분포와 치료계획상의 선량분포 비교. 대한방사선기술학회지:방사선기술과학 2010;33:261-268.
  11. Paganetti H.:Range uncertainties in proton therapy and the role of Monte Carlo simulations. Physics in Medicine & Biology 2012;57:99-117.