Progress in Medical Physics (한국의학물리학회지:의학물리)

Korean Society of Medical Physics (한국의학물리학회)
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Definition of Tumor Volume Based on 18F-Fludeoxyglucose Positron Emission Tomography in Radiation Therapy for Liver Metastases: An Relational Analysis Study between Image Parameters and Image Segmentation Methods

간 전이 암 환자의 18F-FDG PET 기반 종양 영역 정의: 영상 인자와 자동 영상 분할 기법 간의 관계분석

  • Kim, Heejin (Radiological Cancer Medicine, University of Science and Technology) ;
  • Park, Seungwoo (Research Center for Radiotherapy, Korea Institute of Radiological and Medical Sciences) ;
  • Jung, Haijo (Radiological Cancer Medicine, University of Science and Technology) ;
  • Kim, Mi-Sook (Radiological Cancer Medicine, University of Science and Technology) ;
  • Yoo, Hyung Jun (Research Center for Radiotherapy, Korea Institute of Radiological and Medical Sciences) ;
  • Ji, Young Hoon (Radiological Cancer Medicine, University of Science and Technology) ;
  • Yi, Chul-Young (Division of Metrology for Quality of Life, Korea Research Institute of Standards and Science) ;
  • Kim, Kum Bae (Radiological Cancer Medicine, University of Science and Technology)
  • 김희진 (과학기술연합대학원대학교 원자력암의학) ;
  • 박승우 (한국원자력의학원 방사선치료연구센터) ;
  • 정해조 (과학기술연합대학원대학교 원자력암의학) ;
  • 김미숙 (과학기술연합대학원대학교 원자력암의학) ;
  • 유형준 (한국원자력의학원 방사선치료연구센터) ;
  • 지영훈 (과학기술연합대학원대학교 원자력암의학) ;
  • 이철영 (한국표준과학연구원 삶의질표준측정본부) ;
  • 김금배 (과학기술연합대학원대학교 원자력암의학)
  • Received : 2013.01.30
  • Accepted : 2013.05.24
  • Published : 2013.06.30
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Abstract

The surgical resection was occurred mainly in liver metastasis before the development of radiation therapy techniques. Recently, Radiation therapy is increased gradually due to the development of radiation dose delivery techniques. 18F-FDG PET image showed better sensitivity and specificity in liver metastasis detection. This image modality is important in the radiation treatment with planning CT for tumor delineation. In this study, we applied automatic image segmentation methods on PET image of liver metastasis and examined the impact of image factors on these methods. We selected the patients who were received the radiation therapy and 18F-FDG PET/CT in Korea Cancer Center Hospital from 2009 to 2012. Then, three kinds of image segmentation methods had been applied; The relative threshold method, the Gradient method and the region growing method. Based on these results, we performed statistical analysis in two directions. 1. comparison of GTV and image segmentation results. 2. performance of regression analysis for relation between image factor affecting image segmentation techniques. The mean volume of GTV was $60.9{\pm}65.9$ cc and the $GTV_{40%}$ was $22.43{\pm}35.27$ cc, and the $GTV_{50%}$ was $10.11{\pm}17.92$ cc, the $GTV_{RG}$ was $32.89{\pm}36.8$4 cc, the $GTV_{GD}$ was $30.34{\pm}35.77$ cc, respectively. The most similar segmentation method with the GTV result was the region growing method. For the quantitative analysis of the image factors which influenced on the region growing method, we used the standardized coefficient ${\beta}$, factors affecting the region growing method show GTV, $TumorSUV_{MAX/MIN}$, $SUV_{max}$, TBR in order. The result of the region growing (automatic segmentation) method showed the most similar result with the CT based GTV and the region growing method was affected by image factors. If we define the tumor volume by the auto image segmentation method which reflect the PET image parameters, more accurate and consistent tumor contouring can be done. And we can irradiate the optimized radiation dose to the cancer, ultimately.

간 전이 암은 이전에는 수술을 통한 외과적 절제가 주요 치료기법이었지만 방사선 치료 기법의 발전으로 인해 점차 방사선치료의 시행이 늘어나고 있다. 18F-FDG PET 영상은 간 전이 암 진단 시 더욱 우세한 민감도와 특이도를 보이며, 치료계획용 CT 영상과 더불어 종양조직의 위치를 정의하는 중요한 영상장비로 자리매김하고 있다. 본 연구에서는 간 전이 암의 18F-FDG PET 영상에 나타난 종양영역을 영상분할기법 적용하였으며 PET영상의 여러 인자들이 영상분할기법들에 미치는 영향을 알아보았다. 2009년부터 2012년까지 방사선 치료를 받은 간전이 환자들 중 18F-FDG PET/CT 촬영을 시행한 13명의 환자들의 치료계획용 CT와 PET/CT 영상을 얻었다. 그 뒤 PET 영상의 관심영역을 설정하기 위하여 3가지 영상 분할 기법인 상대적문턱기법, 기울기기법, 영역성장기법을 적용하였다. 이 결과들을 바탕으로 GTV와 각 영상 기법으로 구현된 종양 영역과 부피 비교를 시행하였으며 영상 분할 기법에 영향을 미치는 영상인자들과의 관계를 회귀 분석하였다. GTV (Gross Tumor Volume)의 평균 부피는 $60.9{\pm}65.9$ cc이며, 40% 상대적문턱값 기법은 $22.43{\pm}35.3$ cc, 50% 상대적문턱값 기법은 $10.11{\pm}17.9$ cc, 영역성장기법은 $32.89{\pm}36.8$ cc, 기울기기법은 $30.34{\pm}35.8$ cc로 나타났다. 기존의 GTV와 가장 유사한 영역을 나타낸 영상 분할 기법은 영역성장기법 이었다. 이 영역성장기법에 영향을 미치는 영상인자를 정량적으로 분석하기 위해 표준화 계수 ${\beta}$값을 이용하였으며, GTV의 크기, $TumorSUV_{MAX/MIN}$, $SUV_{max}$, TBR 순으로 나타났다. 이와 같은 PET 영상인자를 반영한 영상 분할 기법을 이용해서 종양 영역을 정의한다면 보다 정확하고 일관성 있는 종양그리기를 수행할 수 있으며 궁극적으로 종양에 최적화된 방사선량을 투여할 수 있을 것이다.

Keywords

References

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