The Journal of Korean Society for Radiation Therapy (대한방사선치료학회지)

Korean Society for Radiation Therapy (대한방사선치료학회)
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Evaluation of accuracy in the ExacTrac 6D image induced radiotherapy using CBCT

CBCT을 이용한 ExacTrac 6D 영상유도방사선치료법의 정확도 평가

  • Park, Ho Chun (Department of Radiation Oncology, Chonnam National University Hwasun Hospital, Department of Radiation Oncology, Chonnam National University School) ;
  • Kim, Hyo Jung (Department of Radiation Oncology, Chonnam National University Hwasun Hospital, Department of Radiation Oncology, Chonnam National University School) ;
  • Kim, Jong Deok (Department of Radiation Oncology, Chonnam National University Hwasun Hospital, Department of Radiation Oncology, Chonnam National University School) ;
  • Ji, Dong Hwa (Department of Radiation Oncology, Chonnam National University Hwasun Hospital, Department of Radiation Oncology, Chonnam National University School) ;
  • Song, Ju Young (Department of Radiation Oncology, Chonnam National University Hwasun Hospital, Department of Radiation Oncology, Chonnam National University School)
  • 박호춘 (화순전남대학교병원 방사선종양학과, 전남대학교병원 방사선종양학 교실) ;
  • 김효중 (화순전남대학교병원 방사선종양학과, 전남대학교병원 방사선종양학 교실) ;
  • 김종덕 (화순전남대학교병원 방사선종양학과, 전남대학교병원 방사선종양학 교실) ;
  • 지동화 (화순전남대학교병원 방사선종양학과, 전남대학교병원 방사선종양학 교실) ;
  • 송주영 (화순전남대학교병원 방사선종양학과, 전남대학교병원 방사선종양학 교실)
  • Received : 2016.10.27
  • Accepted : 2016.12.10
  • Published : 2016.12.30
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Abstract

To verify the accuracy of the image guided radiotherapy using ExacTrac 6D couch, the error values in six directions are randomly assigned and corrected and then the corrected values were compared with CBCT image to check the accurateness of ExacTrac. The therapy coordination values in the Rando head Phantom were moved in the directions of X, Y and Z as the translation group and they were moved in the directions of pitch, roll and yaw as the rotation group. The corrected values were moved in 6 directions with the combined and mutual reactions. The Z corrected value ranges from 1mm to 23mm. In the analysis of errors between CBCT image of the phantom which is corrected with therapy coordinate and 3D/3D matching error value, the rotation group showed higher error value than the translation group. In the distribution of dose for the error value of the therapy coordinate corrected with CBCT, the restricted value of dosage for the normal organs in two groups meet the prescription dose. In terms of PHI and PCI values which are the dose homogeneity of the cancerous tissue, the rotation group showed a little higher in the low dose distribution range. This study is designed to verify the accuracy of ExacTrac 6D couch using CBCT. It showed that in terms of the error value in the simple movement, it showed the comparatively accurate correction capability but in the movement when the angle is put in the couch, it showed the inaccurate correction values. So, if the body of the patient is likely to have a lot of changes in the direction of rotation or there is a lot of errors in the pitch, roll and yaw in ExacTrac correction, it is better to conduct the CBCT guided image to correct the therapy coordinate in order to minimize any side effects.

ExacTrac 6D couch를 이용한 영상유도 방사선 치료의 정확도를 검증하기 위하여 여섯 개의 방향의 오차 값을 임의로 부여하여 교정 한 후 CBCT 이미지와 비교 분석하여 ExacTrac의 정확도를 평가 하고자 하였다. Rando head Phantom의 치료좌표 값을 X, Y, Z 방향으로 이동시킨 Translationgroup과 pitch, Roll, Yaw방향으로 이동시킨 Rotationgroup으로 나누어 교정하였다. 교정 수치는 couch의 여섯 개의 방향으로 복합적으로 상호 작용하여 이동 하였다. 교정 값은 최소 1mm, 최대 23mm까지 다양하게 나타났다. 치료좌표로 수정된 Phantom를 CBCT 촬영한 이미지와 3D/3D matching 오차 값의 분석에서는 Rotation group에서 높은 오차 값이 나타났다. CBCT로 교정된 치료좌표 오차 값에 대한 선량분포의 비교에서는 정상조직에 선량 제한치 값은 처방선량에 충족되었으며 종양조직의 선량 균질성 지표인 PHI, PCI 값은 Rotation group에서 저 선량 분포영역이 다소 높음으로 나타났다. 본 연구에서는 ExacTrac 6D couch 의 정확도에 대한 평가를 CBCT를 이용하여 검증해 보았다. 단편적인 이동에 대한 오차 값은 비교적 정확한 교정 능력을 갖추고 있었지만, couch에 각이 들어가는 이동에서는 부정확한 교정 수치를 보였다. 환자의 체위가 Rotation방향으로 많은 변화가 예상되어지거나 ExacTrac 교정하였을 때 pitch, Roll, Yaw값의 오차가 크게 나타나면 CBCT 영상유도를 시행하여 정확히 치료 좌표를 교정하여 예상치 못한 부작용을 최소화해야 된다고 여겨진다.

Keywords

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