Gaurav Verma PhD, Presenter: Nothing to Disclose

Michael Albert Thomas PhD, Abstract Co-Author: Nothing to Disclose

Hari Hariharan, Abstract Co-Author: Nothing to Disclose

Rajakumar Nagarajan PhD, Abstract Co-Author: Nothing to Disclose

Neil Wilson BS, Abstract Co-Author: Nothing to Disclose

Manoj Kumar Sarma PhD, Abstract Co-Author: Nothing to Disclose

Elias Rafic Melhem MD, PhD, Abstract Co-Author: Nothing to Disclose

E. J. Delikatny, Abstract Co-Author: Nothing to Disclose

Harish Poptani PhD, Abstract Co-Author: Nothing to Disclose

Two-dimensional (2D) Localized Correlated Spectroscopy (L-COSY) facilitates improved detection of metabolites that may otherwise appear overlapping and difficult to resolve using 1D MR spectroscopy (MRS). The increased sensitivity/spectral resolution offered by a 7T MRI scanner further enhances the ability of L-COSY to resolve J-coupled metabolites that are difficult to separate at lower fields using conventional spectroscopy. The purpose of this study was to implement L-COSY on a 7T scanner in human brain in vivo. 

The 2D L-COSY sequence was implemented on a Siemens 7T scanner using a 32-channel head “receive” coil (Siemens Medical Solutions, Erlangen, Germany). Seven healthy males, aged 30-72 years, were scanned to test the sensitivity and reproducibility of the 7T L-COSY sequence. A 3 minute T1-weighted MR imaging scan was performed to facilitate placement of the 27cm3 voxel in the mid-occipital gray/white matter region. Two volunteers were also scanned in the parietal region. Scan parameters were as follows: TE/TR=20/2000ms, F1/F2 bandwidth=2500/4000Hz, 8 averages, 64 Δt1 increments, 2048 complex t2 points, with a scan time of 17 minutes. Water suppression was accomplished using the variable power RF pulses with optimized relaxation delays (VAPOR) scheme. 

The 2D L-COSY spectra extracted from both human occipital gray/white matter and parietal lobe studies demonstrated improved spectral sensitivity and resolution compared to analogous studies at lower fields. 2D cross peaks were used to resolve aspartate (Asp), γ-aminobutyric acid (GABA), glutathione (GSH), glutamate/glutamine (Glx), leucine (Leu), Isoleucine (Ile), valine (Val), lactate (Lac), lysine (Lys), myo-inositol (mI), N-acetyl aspartate (NAA), threonine (Thr) as well as the choline group - phosphocholine (PCh), glycerylphosphocholine (GPC), free choline overlapping with mI (mICh), and phosphoethanolamine (PE).

2D L-COSY was successfully implemented at 7T and initial brain spectra show improved detection of metabolites and macromolecules compared to lower fields. 

By resolving choline groups, Lac/lipids and metabolites like GSH, Leu, Lys and Ile, L-COSY could improve the non-invasive assessment of tumors and neuropsychiatric disorders.

Verma, G, Thomas, M, Hariharan, H, Nagarajan, R, Wilson, N, Sarma, M, Melhem, E, Delikatny, E, Poptani, H, Two-dimensional Localized Correlated Spectroscopy Improves Detection of Cerebral Metabolites and Macromolecules Using a 7T Human MRI Scanner.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12043890.html