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Verification of Dose Distribution for Stereotactic Radiosurgery with a Linear Accelerator

  • 박경란 (연세대학교 원주의과대학 치료방사선과학교실) ;
  • 김계준 (연세대학교 원주의과대학 치료방사선과학교실) ;
  • 추성실 (연세대학교 원주의과대학 치료방사선과학교실) ;
  • 이종영 (연세대학교 원주의과대학 치료방사선과학교실) ;
  • 조철우 (연세대학교 원주의과대학 치료방사선과학교실) ;
  • 이창걸 (연세대학교 의과대학 치료방사선과학교실) ;
  • 서창옥 (연세대학교 의과대학 치료방사선과학교실) ;
  • 김귀언 (연세대학교 의과대학 치료방사선과학교실)
  • Park Kyung Ran (Department of Radiation Oncology, Yonsei University Wonju College of Medicine) ;
  • Kim Kye Jun (Department of Radiation Oncology, Yonsei University Wonju College of Medicine) ;
  • Chu Sung Sil (Department of Radiation Oncology, Yonsei University Wonju College of Medicine) ;
  • Lee Jong Young (Department of Radiation Oncology, Yonsei University Wonju College of Medicine) ;
  • Joh Chul Woo (Department of Radiation Oncology, Yonsei University Wonju College of Medicine) ;
  • Lee Chang Geol (Department of Radiation Oncology, Yonsei University College of Medicine) ;
  • Suh Chang Ok (Department of Radiation Oncology, Yonsei University College of Medicine) ;
  • Kim Gwi Eon (Department of Radiation Oncology, Yonsei University College of Medicine)
  • 발행 : 1993.12.01

초록

The calculation of dose distribution in multiple arc stereotactic radiotherapy is a three-dimensional problem and, therefore, the three-dimensional dose calculation algorithm is important and the algorithm's accuracy and reliability should be confirmed experimentally. The aim of this study is to verify the dose distribution of stereotactic radiosurgery experimentally and to investigate the effect of the beam quality, the number of arcs of radiation, and the tertiary collimation on the resulting dose distribution. Film dosimetry with phantom measurements was done to get the three-dimensional orthogonal isodose distribution. All experiments were carried out with a 6 MV X-ray, except for the study of the effects of beam energy on dose distribution, which was done for X-ray energies of 6 and 15 MV. The irradiation technique was from 4 to 11 arcs at intervals of from 15 to 45 degrees between each arc with various field sizes with additional circular collimator. The dose distributions of square field with linear accelerator collimator compared with the dose distributions obtained using circular field with tertiary collimator. The parameters used for comparing the results were the shape of the isodose curve, dose fall-offs fom $90\%$ to $50\%$ and from $90\%\;to\;20\%$ isodose line for the steepest and shallowest profile, and $A=\frac{90\%\;isodose\;area}{50\%\;isodose\;area-90\%\;isodose\;area}$(modified from Chierego). This ratio may be considered as being proportional to the sparing of normal tissue around the target volume. The effect of beam energy in 6 and 15 MV X-ray indicated that the shapes of isodose curves were the same. The value of ratio A and the steepest and shallowest dose fall-offs for 6 MV X-ray was minimally better than that for 15 MV X-ray. These data illustrated that an increase in the dimensions of the field from 10 to 28 mm in diameter did not significantly change the isodose distribution. There was no significant difference in dose gradient and the shape of isodose curve regardless of the number of arcs for field sizes of 10, 21, and 32 mm in diameter. The shape of isodose curves was more circular in circular field and square in square field. And the dose gradient for the circular field was slightly better than that for the square field.

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