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

An evaluation of diurnal variability of cerebral metabolites using 2D L-COSY MRS (#110)

Jameen ARM 1 , Karen Ribbons 2 , Jeannette Lechner-Scott 2 3 4 , Kate Skehan 4 , Shiami Luchow 4 , Sadallah 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, New Lambton Heights, NSW, Australia
  4. Hunter Medical Research Institute, New Lambton Heights, NSW, Australia

Background & Aim

Two dimensional localised correlation spectroscopy (2D L-COSY) has been applied to evaluate in vivo metabolic activity in many neurological conditions1,2. Reproducibility studies have shown 2D L-COSY is reliable and found to have little variation (<10%) in the detection of both diagonal and cross peaks1,3. However, circadian mediators such as brain temperature, hydration and osmotic regulation can affect metabolic profiles4. The aim of this study was to evaluate the diurnal variability in neuro metabolites using 2D L-COSY in healthy subjects.

 

Methods

After local ethics approval and informed consent, 2D L-COSY were obtained on 3T MR unit with 64ch coil. Ten healthy subjects (mean age 36.1±7.7 years, 5Male/5Female) were scanned repeatedly over 10-hour period at 0700, 1200 and 1700 on the same day. The 3x3x3 cm3 MRS voxel was located in the  posterior cingulate gyrus with first TEinitial of 30ms, TR 1.5sec, 8 averages, t1 delay of 0.8ms, and 96 increments. Braino GE phantom was used for in vitro study. Raw spectral data was processed and analysed with Felix software. The peaks studied were total N-acetylaspartate (t_NAA), choline, myo-inositol, glutamate+glutamine (Glx), glutathione and glucose. All peaks were normalised to creatine as an internal reference. One-way repeated measures ANOVA was used to evaluate the effects of time of day on metabolite levels.

 

Results and Discussion

In vitro results showed no significant differences in metabolite ratios (p>0.12) between any time points. In vivo results showed there was statistically significant increase in metabolite levels between 0700 and 1700 for all metabolites (p≤0.05, F>3.88). Glucose (34%) and t_NAA (1.9%) showed the largest and smallest percentage changes respectively. Although the subjects were not controlled for diet or hydration, the possible increase in metabolic changes may be due to osmotic regulatory processes and short-term physiological changes. This study has significant implications for future longitudinal studies using 2D L-COSY where time of the day needs consideration when quantifying neuro metabolites.

  1. Lin AP, Ramadan S, Stern RA, et al. Changes in the neurochemistry of athletes with repetitive brain trauma: preliminary results using localized correlated spectroscopy. Alzheimers Res Ther 2015;7.
  2. Ramadan S, Andronesi OC, Stanwell P, et al. Use of in vivo two-dimensional MR spectroscopy to compare the biochemistry of the human brain to that of glioblastoma. Radiology 2011;259(2):540-549.
  3. Binesh N, Yue K, Fairbanks L, et al. Reproducibility of localized 2D correlated MR spectroscopy. Magn Reson Med 2002;48(6):942-948.
  4. Soreni N, Noseworthy MD, Cormier T, et al. Intraindividual variability of striatal H-1-MRS brain metabolite measurements at 3 T. Magn Reson Imaging 2006;24(2):187-194.