Progress in Medical Physics (한국의학물리학회지:의학물리)

Korean Society of Medical Physics (한국의학물리학회)
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Evaluations of Inhomogeneous Shimming in $^1$H MR Spectroscopy

자기공명분광에서 비균질 자장보정에 관한 평가

  • Choe, Bo-Young (Department of Biomedical Engineering, College of Medicine, The Catholic University of Korea) ;
  • Baik, Hyeon-Man (Department of Biomedical Engineering, College of Medicine, The Catholic University of Korea) ;
  • Suh, Tae-Suk (Department of Biomedical Engineering, College of Medicine, The Catholic University of Korea) ;
  • Lee, Hyoung-Koo (Department of Biomedical Engineering, College of Medicine, The Catholic University of Korea) ;
  • Chun, Heung-Jae (Department of Biomedical Engineering, College of Medicine, The Catholic University of Korea) ;
  • Shim, Kyung-Sub (Department of Biomedical Engineering, College of Medicine, The Catholic University of Korea)
  • Published : 2000.03.01
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Abstract

In this study, we investigate the effects of poor shimming on quantitative measurement of ratios of metabolite levels by proton magnetic resonance spectroscopy ($^1$H MRS). Coefficient of variation (COV) of metabolite ratios for point resolved spectroscopy (PRESS) and stimulated-echo acquisition mode (STEAM) spectra was evaluated from a phantom containing in vivo levels of metabolites using a conventional whole body 1.5T MR system and conventional acquisition and analysis protocol. A statistical P-value was also calculated from a linear regression for relationship of metabolite ratios. N-acetylaspartate (NAA)/ creatine (Cr) and NAA/ choline (Cho) had low COV values for the long and short TE spectra (29.1 and 27.5%; 23.8 and 12.6 %), whereas Cho/Cr and Cr/Cho had high COV values (50.0 and 68.6 %; 27.5 and 29.3 %). A linear relationship between NAA/Cr and Cho/Cr, and between NAA/Cho and Cr/Cho revealed the statistical significance in the long and short TE spectra, respectively (P < 0.0001 and P < 0.0001; P = 0.015 and P = 0.005). There was no significant relationship between Cho/NAA and Cr/NAA in the measurement (P = 0.159; P = 0.910). The present study suggested that NAA/Cr and NAA/Cho could be useful for data with poor shimming in $^1$H MR spectroscopy. In conclusion, statistical significance of metabolite ratios indicated that the Cr and Cho levels could be interpreted as a significant alteration factor in the long and short TE spectra, and then should be used with care to provide precise metabolite quantification.

본 연구에서는 양성자 자기공명분광법을 이용하여 대사물질의 양적 비율 산출시 비균질한 자장보정의 영향을 정량평가하였다. 점분해분광법과 자극반향 획득법을 사용하여 대사비율의 변화상수를 전신 1.5T 자기공명장비, 기존 분석방법에 의해 평가하였다. 통게학적 분석방법으로 선형계측방법을 사용하여 P d값을 산출하였다. 결과로서 N-acetylaspartate (NAA)/ creatine (Cr)과 NAA/ choline (Cho) 비율은 긴 TE와 짧은 TE 값에 대해 낮은 COV 값은 나타낸 반면 Cho/Cr과 Cr/Cho 비율은 높은 COV 값을 나타냈다. NAA/Cr과 Cho/Cr 그리고 NAA/Cho과 Cr/Cho 비율은 긴 TE와 짧은 TE 값에 대해 상당한 긴밀한 P값을 나타냈다. (P < 0.0001 and P < 0.0001; P = 0.015 and P = 0.005). 반면 Cho/NAA과 Cr/NAA은 통게Gkr적 유의성이 발견되지 않았다. (P = 0.159; P = 0.910). 본 연구 결과에 의해서 NAA/Cr과 NAA/Cho 비율은 자기공명분광 비율산출에서 자기보정에 관계없이 가장 유용한 방법으로 나타났다. 결론적으로 Cr과 Cho는 정확한 정량측정시 가장 유용한 대사물질로 나타났다.

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