The Korean Journal of Nuclear Medicine (대한핵의학회지)

The Korean Society of Nuclear Medicine (대한핵의학회)
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Assessment of Attenuation Correction Techniques with a $^{137}Cs$ Point Source

$^{137}Cs$ 점선원을 이용한 감쇠 보정기법들의 평가

  • Bong, Jung-Kyun (Department of Radiology, Yonsei University College of Medicine Research Institute of Radiological Science, Yonsei University) ;
  • Kim, Hee-Joung (Division of Nuclear Medicine, Yonsei University) ;
  • Son, Hye-Kyoung (Department of Radiology, Yonsei University College of Medicine Research Institute of Radiological Science, Yonsei University) ;
  • Park, Yun-Young (Department of Radiology, Yonsei University College of Medicine Research Institute of Radiological Science, Yonsei University) ;
  • Park, Hae-Joung (Division of Nuclear Medicine, Yonsei University) ;
  • Yun, Mi-Jin (Division of Nuclear Medicine, Yonsei University) ;
  • Lee, Jong-Doo (Department of Radiology, Yonsei University College of Medicine Research Institute of Radiological Science, Yonsei University) ;
  • Jung, Hae-Jo (Department of Radiology, Yonsei University College of Medicine Research Institute of Radiological Science, Yonsei University)
  • 봉정균 (연세대학교 진단방사선과 방사선의과학 연구소) ;
  • 김희중 (연세대학교 핵의학과) ;
  • 손혜경 (연세대학교 진단방사선과 방사선의과학 연구소) ;
  • 권윤영 (연세대학교 진단방사선과 방사선의과학 연구소) ;
  • 박해정 (연세대학교 핵의학과) ;
  • 윤미진 (연세대학교 핵의학과) ;
  • 이종두 (연세대학교 진단방사선과 방사선의과학 연구소) ;
  • 정해조 (연세대학교 진단방사선과 방사선의과학 연구소)
  • Published : 2005.02.28
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Abstract

Purpose: The objective of this study was to assess attenuation correction algorithms with the $^{137}Cs$ point source for the brain positron omission tomography (PET) imaging process. Materials & Methods: Four different types of phantoms were used in this study for testing various types of the attenuation correction techniques. Transmission data of a $^{137}Cs$ point source were acquired after infusing the emission source into phantoms and then the emission data were subsequently acquired in 3D acquisition mode. Scatter corrections were performed with a background tail-fitting algorithm. Emission data were then reconstructed using iterative reconstruction method with a measured (MAC), elliptical (ELAC), segmented (SAC) and remapping (RAC) attenuation correction, respectively. Reconstructed images were then both qualitatively and quantitatively assessed. In addition, reconstructed images of a normal subject were assessed by nuclear medicine physicians. Subtracted images were also compared. Results: ELEC, SAC, and RAC provided a uniform phantom image with less noise for a cylindrical phantom. In contrast, a decrease in intensity at the central portion of the attenuation map was noticed at the result of the MAC. Reconstructed images of Jaszack and Hoffan phantoms presented better quality with RAC and SAC. The attenuation of a skull on images of the normal subject was clearly noticed and the attenuation correction without considering the attenuation of the skull resulted in artificial defects on images of the brain. Conclusion: the complicated and improved attenuation correction methods were needed to obtain the better accuracy of the quantitative brain PET images.

목적: PET 영상화를 위해 다양한 감쇠 보정 방법들이 $^{137}Cs$ 투과 점선원의 데이터를 처리하는데 있어서 개발되어 왔다. 본 연구의 목적은 뇌 PET 영상을 위해 $^{137}Cs$ 점선원에서 사용하는 감쇠보정 가법들을 평가하는 것이다. 대상 및 방법: 감쇠 보정 기법들을 시험하기 위해, 4가지 종류의 팬텀들이 사용되었다. $^{137}Cs$투과 점선원의 데이터는 팬텀 안에 방출 선원을 주입한 후 획득되었고, 그 뒤로 방출 선원 데이터가 3D 획득 방식으로 획득되었다. 산란 보정은 배후 방사능을 가감하는 방법 (background tail-fitting algorithm)으로 실행되었다. 그리고 나서, 방출 데이터는 각각 측정 감쇠 보정(MAC), 타원형 감쇠 보정(ELAC), 분할 감쇠보정(SAC), 재배치 감쇠보정(RAC)으로 반복적 재구성 방법을 사용하여 재구성되었다. 그런 다음, 재구성된 영상들이 정량적으로 그리고 정성적으로 평가가 되었다. 부가적으로, 정상인에 대해서 평가가 이루어졌는데, 정상인에 대한 재구성 영상은 핵의학 전문의들에 의해서 평가되었다. 또한 가감된 영상들이 비교되었다. 결과: ELAC, SAC, RAC은 원통형 팬텀에 대해 노이즈가 적은 균일한 팬텀 영상을 제공하였다. 반면에, MAC의 결과에서 감쇠맵의 중심 부분에서 세기가 떨어지는 것을 보여주었다. Jaszack과 Hoffman 팬텀들에 대한 재구성 영상은 RAC과 SAC을 각각 적용시 더 좋은 영상 질을 나타냈다. 정상인 대상자의 영상에 있어서 두개골의 감쇠가 두드러졌고, 두개골에 대한 감쇠를 고려하지 않은 감쇠 보정은 뇌 영상들상에서 인공적인 손상이 있는 것처럼 나타났다. 결론: 복잡하고 개선된 감쇠보정 기법들이 정량적 그리고 정성적으로 정확한 뇌 PET영상으로 개선시키는데 있어서 필요하다. 본 연구는 $^{137}Cs$ 투과 선원을 사용하여 이루어지는 감쇠보정법을 이용하는 뇌 PET 영상화 기기들을 개선시키는데 유용할 것으로 사료된다.

Keywords

References

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