광자선 및 전자선 치료에서 피부선량계의 측정과 시뮬레이션을 이용한 감약률 오차 평가 = Evaluation of Attenuation Rate Error on Skin Dosimeter using Monte Carlo Simulation in Photon and Electron Beam Therapy

다국어 초록 (Multilingual Abstract)

In the field of radiation therapy using photon beams and electron beams, since each patient has a different sensitivity to radiation, skin side effects may occur even at the same dose. Therefore, if there is a risk of excessive dose to the skin, a dosimeter is attached to verify whether the correct dose is being investigated. However, since the skin dosimeter checks the attachment site visually by measuring a point dose, it is difficult to confirm an accurate dose distribution. As a result, the measurement and simulation errors of the material HgI2 in the 6 MV photon beam were 3.73% and 5.24%, respectively, at the minimum thickness of 25 μm, and the material PbI2 was 4.73% and 5.65%, respectively. On the other hand, as a result of the 6 MeV electron beam, the measurement and simulation errors of the material HgI2 were 1.35% and 1.12%, respectively, at a minimum thickness of 25 μm, and the material PbI2 showed relatively low attenuation error, 1.67% and 1.20%, respectively. Therefore, it was evaluated that the thickness of the photon beam within 25 μm and the electron beam within 100 μm is suitable to have a reduction rate error within 5%. This study presents a new research direction for a flexible dosimeter attached to the human body that is required in clinical practice and the construction conditions of a future skin dosimeter.

국문 초록 (Abstract)

광자선과 전자선을 사용하는 방사선 치료 분야에서는 환자마다 방사선에 대한 민감도가 다르기 때문에 동일한 선량에서도 피부 부작용이 발생될 수 있다. 이에 피부에 과다선량 위험도가 있을 경우, 선량계를 부착하여 정확한 선량이 조사되고 있는지 검증하고 있다. 하지만 피부선량계는 점선량을 측정하는 방식으로 부착부위를 육안으로 확인하기 때문에, 정확한 선량 분포를 확인하기 어려운 문제점이 있다. 이에 본 연구에서는 체표면적에 대한 선량분포를 확인할 수 있는 2D 선량계의 기초 연구로 감약률 오차를 분석하여 최적화된 선량계 조건을 제시하고자 하였다. 본 결과 6 MV 광자선에서 물질 HgI2의 측정과 시뮬레이션 오차는 최소두께 25 μm에서 각 각 3.73%, 5.24%를 보였고, 물질 PbI2는 각각 4.73%, 5.65%를 보였다. 반면 6 MeV 전자선 결과, 물질 HgI2의 측정과 시뮬레이션 오차는 최소두께 25 μm에서 각 각 1.35%, 1.12%를 보였고, 물질 PbI2는 각 각 1.67%, 1.20%로 비교적 낮은 감약률 오차를 보였다. 이에 본 연구 결과 5% 이내의 감약률 오차를 가지기 위해서는 광자선 측정은 최소 25 μm 미만, 전자선 측정은 100 μm 이내 두께가 적합한 것으로 평가되었다. 본 연구는 임상에서 요구되는 인체 부착형 flexible 선량계의 새로운 연구 방향과 미래 피부선량계의 구성 조건을 제시하고 있다.

참고문헌 (Reference)

1 Dirk Wolff, "Volumetric modulated arc therapy (VMAT) vs. serial tomotherapy, step-and-shoot IMRT and 3D-conformal RT for treatment of prostate cancer" Elsevier BV 93 (93): 226-233, 2009

2 B. Emami, "Tolerance of normal tissue to therapeutic irradiation" Elsevier BV 21 (21): 109-122, 1991

3 Tatsiana A. Reynolds, "Surface dose measurements with commonly used detectors: a consistent thickness correction method" Wiley 16 (16): 358-366, 2015

4 Kry SF, "Skin dose during radiotherapy: a summary and general estimation technique" 13 (13): 20-34, 2012

5 Neal E. Hartsough, "Polycrystalline Mercuric Iodide Films on CMOS Readout Arrays" Institute of Electrical and Electronics Engineers (IEEE) 56 (56): 1810-1816, 2009

6 F. M. Khan, "Khan’s the physics of radiation therapy" Wolters Kluwer 1987

7 Mianzeng Zhong, "Flexible photodetectors based on phase dependent PbI2 single crystals" Royal Society of Chemistry (RSC) 4 (4): 6492-6499, 2016

8 Hui Sun, "Flexible X-ray detector based on sliced lead iodide crystal" Wiley 11 (11): 1600397-, 2017

9 Kyungmin Oh, "Flexible X-ray Detector for Automatic Exposure Control in Digital Radiography" American Scientific Publishers 16 (16): 11473-11476, 2016

10 Laurence E. Court, "Experimental evaluation of the accuracy of skin dose calculation for a commercial treatment planning system" Wiley 9 (9): 29-35, 2008

11 이현직, "Evaluations and Comparisons of Body Surface Doses during Breast Cancer Treatment by Tomotherapy and LINAC Radiotherapy Devices" 한국의학물리학회 28 (28): 218-225, 2017

12 K. M. Oh, "Development and evaluation of polycrystalline cadmium telluride dosimeters for accurate quality assurance in radiation therapy" 11 (11): 1-8, 2016

13 K. T. Kim, "Development and evaluation of multi-energy PbO dosimeter for quality assurance of image-guide radiation therapy devices" 12 (12): 1-10, 2017

14 김중선, "Comparison of Skin Injury Induced by β- and γirradiation in the Minipig Model" 대한방사선방어학회 42 (42): 189-196, 2017

15 P. Andreo, "Absorbed Dose Determination in External Beam Radiotherapy: An International Code of Practice for Dosimetry based on Standards of Absorbed Dose to Water" 2006