Progress in Medical Physics (한국의학물리학회지:의학물리)

Korean Society of Medical Physics (한국의학물리학회)
권호 표지

3-Dimensional Dosimetry of Small Field Photon Beam

광자선의 소조사면에서의 3차원적 선량 측정

  • Jang, Ji-Sun (CyberKnife Center, Seoul St. Mary's Hospital, The Catholic University of Korea) ;
  • Kwon, Soo-Il (Department of Medical Physics, Kyonggi University)
  • 장지선 (가톨릭대학교 서울성모병원 사이버나이프센터) ;
  • 권수일 (경기대학교 대학원 의학물리학과)
  • Received : 2012.02.23
  • Accepted : 2012.03.22
  • Published : 2012.03.31
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Abstract

A polymer gel dosimeter was fabricated. A 3-dimensional dosimetry experiment was performed in the small field of the photon of the cyberknife. The dosimeter was installed in a head and neck phantom. It was manufactured from the acrylic and it was used in dosimetry. By using the head and neck CT protocol of the CyberKnife system, CT images of the head and neck phantom were obtained and delivered to the treatment planning system. The irradiation to the dosimeter in the treatment planning was performed, and then, the image was obtained by using 3.0T magnetic resonance imaging (MRI) after 24 hours. The dose distribution of the phantom was analyzed by using MATLAB. The results of this measurement were compared to the results of calculation in the treatment planning. In the isodose curve on the axial direction, the dose distribution coincided with the high dose area, 0.76mm difference on 80%, rather than the low dose area, 1.29 mm difference on 40%. In this research, the fact that the polymer gel dosimeter and MRI can be applied for analyzing a small field in a 3 dimensional dosimetry was confirmed. Moreover, the feasibility of using these for the therapeutic radiation quality control was also confirmed.

중합체 겔 선량계를 제작하여 사이버나이프의 광자선의 소조사면에서의 3차원적 선량측정 실험을 수행하였다. 겔 선량계는 아크릴로 제작된 두경부 팬텀내에 설치하여 선량측정에 사용하였다. 두경부 팬텀의 영상은 사이버나이프의 두경부 환자 치료를 위해 사용하는 전산화단층촬영장치(CT)의 프로토콜을 사용하여 획득하였고 치료계획 시스템에 전달되었다. 겔 선량계에 치료계획에서 수립한 방사선을 조사하였으며, 24시간 경과 후에 선량분석을 위하여 3.0T 자기공명영상장치(MRI)로 영상을 획득하였다. 측정된 겔 팬텀의 선량분포는 MATLAB을 이용하여 분석하였고 측정된 결과를 치료계획에서의 계산값과 비교하였다. 선량분포는 축상(axial) 방향의 등선량곡선의 80% 고선량 영역에서 치료계획 선량곡선과 측정된 선량곡선과의 차이가 0.76 mm이었으며, 40% 저선량 영역에서는 차이가 1.29 mm로 저선량 영역보다 고 선량영역에서 잘 일치함을 알 수 있었다. 본 연구에서 중합체 겔 선량계와 자기공명영상을 이용하여 소조사면에 대해 3차원적으로 선량을 분석할 수 있을 뿐 아니라 치료방사선 정도관리에도 활용될 수 있는 가능성을 확인하였다.

Keywords

References

  1. Mack A, Scheib SG, Major J, et al: Precision dosimetry for narrow photon beams used in radiosurgery Determination of Gamma Knife output factors. Med Phys 29:2080-2089 (2002) https://doi.org/10.1118/1.1501138
  2. Wilcox EE, Daskalov GM: Accuracy of dose measurements and clacluations within and beyond heterogeneous tissues for 6 MV photon fields smaller than 4 cm produced by Cyberknife. Med Phys 35:2259-2266 (2008) https://doi.org/10.1118/1.2912179
  3. Das IJ, Ding GX, Ahnesjo A: Small fields: Nonequilibrium radiation dosimetry. Med Phys 35:206-215 (2008) https://doi.org/10.1118/1.2815356
  4. Pappas E, Petrokokkinos L, Aangelopoulos A, et al: Relative output factor measurements of a 5 mm diameter radiosurgical photon beam using polymer gel dosimetry. Med Phys 32:1513-1520 (2005) https://doi.org/10.1118/1.1916048
  5. Pantelis E, Antypas C, Petrokokkinos L, et al: Dosimetric Characterization of CyberKnife radiosurgical photon beams using polymer gels. Med Phys 35:2312-2320 (2008) https://doi.org/10.1118/1.2919099
  6. McJury M, Oldham M, Cosgrove VP, et al: Radiation dosimetry using polymer gels: methods and applications. Br J Radiol 73:919-929 (2000)
  7. Novotny J Jr, Spevacek V, Dvorak P, Novotny J, Cechak T: Energy and dose rate dependence of BANG-2 polymer-gel dosimeter. Med Phys 28:2379-2386 (2001) https://doi.org/10.1118/1.1414307
  8. Wong CJ, Ackerly T, He C, et al: Small field size dose-profile measurements using gel dosimeters, gafchromic films and micro-thermoluminescent dosimeters. Radiat Meas 44:249-256 (2009) https://doi.org/10.1016/j.radmeas.2009.03.012
  9. Pappas E: On the role of polymer gels in the dosimetry of small photon fields used in radiotherapy. J Phys Conf Ser 164:012060 (2009) https://doi.org/10.1088/1742-6596/164/1/012060
  10. Moutsatsosn A, Petrokokkinos L, Zourari K, et al: Gamma Knife relative dosimetry using VIP polymer gel and EBT radiochromic films. J Phys Conf Ser 164:012053 (2009) https://doi.org/10.1088/1742-6596/164/1/012053
  11. 오영택, 강해진, 김미화 등: 중합체 겔과 자기공명영상을 이용한 3차원 선량분포 측정. 대한방사선종양학회 20:264-273 (2002)
  12. 강해진, 조삼주, 정은기 등: 방사선 근접치료에 있어서 핵자기공명영상을 이용한 3차원 방사선 선량분포도의 가시화를 위한 polymer 젤의 이용. 의학물리 9:207-215 (1998)
  13. Cho SJ, Shin DH, Huh HD, et al: Development of a Novel Normoxic Polymer Gel Dosimeter (TENOMAG). J Korean Phys Soc 51:1798-1804 (2007) https://doi.org/10.3938/jkps.51.1798
  14. 정재용, 이충일, 민정환 등: X-ray CT Scanner를 이용한 MAGAT (Methacrylic Acid, Gelatin Gel and THPC) 중합체 겔 선량계의 선량 반응성 연구. 의학물리 21:1-8 (2010)
  15. Maryanski MJ, Audet C, Gore JC: Effects of crosslinking and temperature on the dose response of a BANG polymer gel dosimeter. Phys Med Biol 42:303-311 (1997) https://doi.org/10.1088/0031-9155/42/2/004
  16. Spevacek V, Novotny J Jr, Dvorak P, Novotny J, Vymazal J, Cechak T: Temperature dependence of polymer-gel dosimeter nuclear magnetic resonance response. Med Phys 28:2370-2378 (2001) https://doi.org/10.1118/1.1410124