Determining the Location of Metallic Needle from MR Images Distorted by Susceptibility Difference

자화율 차이로 인해 왜곡된 영상으로부터 금속 바늘의 위치 결정

  • Kim, Eun-Ju (Fusion Technology Medical Device Team, Korea Food & Drug Administration) ;
  • Kim, Dae-Hong (Molecular Imaging and Therapy Branch, National Cancer Center)
  • 김은주 (식품의약품안전청 융합기기팀) ;
  • 김대홍 (국립암센터 분자영상치료연구과)
  • Received : 2010.10.04
  • Accepted : 2010.12.15
  • Published : 2010.12.30

Abstract

Purpose : To calculate the appearance of the image distortion from metallic artifacts and to determine the location of a metallic needle from a distorted MR image. Materials and Methods : To examine metal artifacts, an infinite metal cylinder in a strong magnetic field are assumed. The cylinder’s axis leaned toward the magnetic field along some arbitrary angle. The Laplace equation for this situation was solved to investigate the magnetic field distortion, and the simulation was performed to evaluation the image artifact caused by both readout and slice-selection gradient field. Using the result of the calculation, the exact locations of the metal cylinder were calculated from acquired images. Results : The distances between the center and the folded point are measured from images and calculated. Percentage errors between the measured and calculated distance were less than 5%, except for one case. Conclusion : The simulation was successfully performed when the metal cylinder was skewed at an arbitrary tilted angle relative to the main magnetic field. This method will make it possible to monitor and guide both biopsy and surgery with real time MRI.

목적: 금속에 의한 영상 왜곡에 대한 정확한 계산하고 영상으로부터의 금속 물질의 위치 결정한다. 대상 및 방법: 주자기장과 일정 각도를 이루는 무한히 긴 비자성 금속 실린더에 대한 라플라스 방정식을 풀고, 이 결과를 이용하여 절편선택 경사자계와 주파수 부호화 경사자계에 의한 영상에 왜곡을 계산한다. 계산 결과를 바탕으로 하여 왜곡된 영상으로부터 원통형 보철물의 위치를 계산한다. 결과: Folded point와 금속 실린더의 중심 사이의 거리를 영상으로부터 측정하여 계산 결과와 비교한다. 측정 결과와 계산 결과 간의 퍼센트 오차는 한 경우를 제외하고 5% 이내였다. 결론: 금속 실린더가 자기장 하에 있을 때, 영상의 왜곡을 시뮬레이션 하였고, 이 기술은 생검술 또는 외과 수술 등을 자기공명영상법을 이용여 실시간 모니터링하는데 적용할 수 있을 것으로 기대한다.

Keywords

References

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