Radiation Oncology Journal

The Korean Society for Radiation Oncology (대한방사선종양학회)
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Evaluation of the Positional Uncertainty of a Liver Tumor using 4-Dimensional Computed Tomography and Gated Orthogonal Kilovolt Setup Images

사차원전산화단층촬영과 호흡연동 직각 Kilovolt 준비 영상을 이용한 간 종양의 움직임 분석

  • Ju, Sang-Gyu (Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine) ;
  • Hong, Chae-Seon (Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine) ;
  • Park, Hee-Chul (Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine) ;
  • Ahn, Jong-Ho (Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine) ;
  • Shin, Eun-Hyuk (Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine) ;
  • Shin, Jung-Suk (Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine) ;
  • Kim, Jin-Sung (Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine) ;
  • Han, Young-Yih (Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine) ;
  • Lim, Do-Hoon (Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine) ;
  • Choi, Doo-Ho (Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine)
  • 주상규 (성균관대학교 의과대학 삼성서울병원 방사선종양학교실) ;
  • 홍채선 (성균관대학교 의과대학 삼성서울병원 방사선종양학교실) ;
  • 박희철 (성균관대학교 의과대학 삼성서울병원 방사선종양학교실) ;
  • 안종호 (성균관대학교 의과대학 삼성서울병원 방사선종양학교실) ;
  • 신은혁 (성균관대학교 의과대학 삼성서울병원 방사선종양학교실) ;
  • 신정석 (성균관대학교 의과대학 삼성서울병원 방사선종양학교실) ;
  • 김진성 (성균관대학교 의과대학 삼성서울병원 방사선종양학교실) ;
  • 한영이 (성균관대학교 의과대학 삼성서울병원 방사선종양학교실) ;
  • 임도훈 (성균관대학교 의과대학 삼성서울병원 방사선종양학교실) ;
  • 최두호 (성균관대학교 의과대학 삼성서울병원 방사선종양학교실)
  • Received : 2010.04.07
  • Accepted : 2010.07.07
  • Published : 2010.09.30
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Abstract

Purpose: In order to evaluate the positional uncertainty of internal organs during radiation therapy for treatment of liver cancer, we measured differences in inter- and intra-fractional variation of the tumor position and tidal amplitude using 4-dimentional computed radiograph (DCT) images and gated orthogonal setup kilovolt (KV) images taken on every treatment using the on board imaging (OBI) and real time position management (RPM) system. Materials and Methods: Twenty consecutive patients who underwent 3-dimensional (3D) conformal radiation therapy for treatment of liver cancer participated in this study. All patients received a 4DCT simulation with an RT16 scanner and an RPM system. Lipiodol, which was updated near the target volume after transarterial chemoembolization or diaphragm was chosen as a surrogate for the evaluation of the position difference of internal organs. Two reference orthogonal (anterior and lateral) digital reconstructed radiograph (DRR) images were generated using CT image sets of 0% and 50% into the respiratory phases. The maximum tidal amplitude of the surrogate was measured from 3D conformal treatment planning. After setting the patient up with laser markings on the skin, orthogonal gated setup images at 50% into the respiratory phase were acquired at each treatment session with OBI and registered on reference DRR images by setting each beam center. Online inter-fractional variation was determined with the surrogate. After adjusting the patient setup error, orthogonal setup images at 0% and 50% into the respiratory phases were obtained and tidal amplitude of the surrogate was measured. Measured tidal amplitude was compared with data from 4DCT. For evaluation of intra-fractional variation, an orthogonal gated setup image at 50% into the respiratory phase was promptly acquired after treatment and compared with the same image taken just before treatment. In addition, a statistical analysis for the quantitative evaluation was performed. Results: Medians of inter-fractional variation for twenty patients were 0.00 cm (range, -0.50 to 0.90 cm), 0.00 cm (range, -2.40 to 1.60 cm), and 0.00 cm (range, -1.10 to 0.50 cm) in the X (transaxial), Y (superior-inferior), and Z (anterior-posterior) directions, respectively. Significant inter-fractional variations over 0.5 cm were observed in four patients. Min addition, the median tidal amplitude differences between 4DCTs and the gated orthogonal setup images were -0.05 cm (range, -0.83 to 0.60 cm), -0.15 cm (range, -2.58 to 1.18 cm), and -0.02 cm (range, -1.37 to 0.59 cm) in the X, Y, and Z directions, respectively. Large differences of over 1 cm were detected in 3 patients in the Y direction, while differences of more than 0.5 but less than 1 cm were observed in 5 patients in Y and Z directions. Median intra-fractional variation was 0.00 cm (range, -0.30 to 0.40 cm), -0.03 cm (range, -1.14 to 0.50 cm), 0.05 cm (range, -0.30 to 0.50 cm) in the X, Y, and Z directions, respectively. Significant intra-fractional variation of over 1 cm was observed in 2 patients in Y direction. Conclusion: Gated setup images provided a clear image quality for the detection of organ motion without a motion artifact. Significant intra- and inter-fractional variation and tidal amplitude differences between 4DCT and gated setup images were detected in some patients during the radiation treatment period, and therefore, should be considered when setting up the target margin. Monitoring of positional uncertainty and its adaptive feedback system can enhance the accuracy of treatments.

목 적: 4-dimensional computed tomography (4DCT) 영상과 on board imaging (OBI) 및 real time position management (RPM) 장치로 매 회 치료 시마다 얻은 호흡연동 직각 kilovolt (KV) 준비 영상(gated orthogonal kilovolt setup image)을 이용해 간암 환자를 치료하는 동안 발생하는 종양 위치의 불확실성을 평가하고자 했다. 대상 및 방법: 3차원입체조형치료가 예정된 20명의 간암 환자를 대상으로 RPM과 전산화단층촬영모의치료기를 이용해 치료계획용 4DCT를 시행했다. 표적 근처에 위치한 간동맥화학색전술 후 집적된 리피오돌(lipiodol) 혹은 횡격막을 종양의 위치 변이를 측정하는 표지자로 선택했다. 표지자의 위치 차이를 이용해 온라인 분할간 및 분할중 내부 장기 변이와 움직임 진폭을 측정했다. 측정된 자료의 정량적 평가를 위해 통계 분석을 실시했다. 결 과: 20명 환자로부터 측정된 표지자의 분할간변이의 중앙값은 X (transaxial), Y (superior-inferior), Z (anterior-posterior) 축에서 각각 0.00 cm (범위, -0.50~0.90 cm), 0.00 cm (범위, -2.4~1.60 cm), 0.00 cm (범위, -1.10~0.50 cm) 였다. 4명의 환자에서 X, Y, Z축 중 하나 이상에서 0.5 cm를 초과하는 변이가 관찰되었다. 4DCT와 호흡연동 직각 준비 영상으로부터 얻은 표적의 움직임 진폭의 차이는 X, Y, Z 축에서 각각 중앙값이 -0.05 cm (범위, -0.83~0.60 cm), -0.15 cm (범위, -2.58~1.18 cm), -0.02 cm (범위, -1.37~0.59 cm) 였다. 두 영상간 표적의 움직임 진폭 차이가 1 cm를 초과하는 환자가 Y축 방향으로 3명 관찰되었으며, 0.5 cm 초과 1 cm 미만의 차이를 보이는 환자도 Y축과 Z축 방향을 합쳐 5명 관찰되었다. 분할중 표지자 위치 변이의 중앙값은 X, Y, Z축에서 각각 0.00 cm (범위, -0.30~0.40 cm), -0.03 cm (범위, -1.14~0.50 cm), 0.05 cm (범위, -0.30~0.50 cm)였으며 2명의 환자에서 1 cm를 초과하는 변이가 Y축 방향으로 관찰되었다. 결 론: 4DCT와 호흡연동 직각 KV 준비 영상으로 얻은 표지자의 분할간, 분할중 및 움직임 진폭에서 큰 변이가 관찰되었다.

Keywords

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