Poster Presentation Australian & New Zealand Society of Magnetic Resonance Conference 2017

Improved detection of neuro metabolites with short initial echo time 2D L-COSY (#94)

Jameen ARM 1 , Karen Ribbons 2 , Jeannette Lechner-Scott 2 3 4 , Kate Skehan 4 , Shiami Luchow 4 , Albert Thomas 5 , Saadallah Ramadan 1 4
  1. School of Health Sciences, University of Newcastle, Newcastle, NSW, Australia
  2. Neurology, John Hunter Hospital, New Lambton Heights, NSW, Australia
  3. School of Medicine and Public Health, University of Newcastle, Newcastle, NSW, Australia
  4. Hunter Medical Research Institute, New Lambton Heights, NSW, Australia
  5. Department of Radiology, Psychiatry, UCLA , Los Angeles, California, USA

Background

The detection of neuro metabolites such as glutamine+glutamate (Glu+Gln: Glx), glutathione (GSH), glycerophosphocholine (GPC), phosphorylethanolamine (PE), with two dimensional localised correlation spectroscopy (2D L-COSY) can be challenging due to their complex inherent chemical structure and low physiological concentrations1. We investigated if 2D L-COSY with initial short TE of 20ms can improve the detectability of metabolites compared with standard initial TE of 30ms thus improving the detection of metabolites.

 

Method

After ethics approval and informed consent, in-vivo MRS using initial TE values of 20ms and 30ms 2D L-COSY were performed in the same session on 3 Tesla MRI with 64Channel brain coil. Braino Phantom was used for in vitro and three healthy volunteers were enrolled for the in-vivo study. 2D L-COSY was acquired from the posterior cingulate gyrus from a 27cm3 voxel, first TEinitial of 30ms and then TEinitial of 20ms, TR 1.5sec, 8 averages, and 96 increments.  Raw spectral data was processed with Felix software. The signal intensity of diagonal and cross peaks, as well as background noise, were measured for each experiment. Mean SNR (peak intensity/noise)3 of selected peaks, as well as % SNR differences, were calculated.

 

Results and Discussion

The mean and the percentage mean difference in peak SNR betweenTE20 and TE30 showed marked increase in SNR for TE20, both for the diagonal (N-acetyl aspartate, Creatine, Choline, myo Inositol and lipid) and cross peaks (GSH, GPC, PE, Glx and lysine). In vitro data showed similar trend in increasing SNR for all major diagonal and cross peaks, but to lesser extent than in vivo results. Initial TE is an important parameter as it determines the extent of signal loss depending on characteristic T2* values. 2D L-COSY with short TE of 20ms has potential in the improved detection of cross peaks from metabolites.

 

References

  1. Fuchs AH, Boesiger, A P. Special COSY at 7T. Proceedings of the joint 18th annual scientific meeting of ISMRM and the 27th annual scientific meeting of ESMRMB, Stockholm, Sweden, May 1st-7th 2010: 92 2010.
  2. Schirmer T, Auer DP. On the reliability of quantitative clinical magnetic resonance spectroscopy of the human brain. NMR in biomedicine 2000;13:28-36.
  3. Skelton NJ, Palmer AG, Akke M, et al. Practical Aspects of Two-Dimensional Proton-Detected 15N Spin Relaxation Measurements. Journal of Magnetic Resonance, Series B 1993;102(3):253-264.