LCModel Basis Sets
- "Kaiser/Govindaraju Coupling Constants" indicates that the chemical shifts and coupling constants from the Kaiser/Govindaraju publications were used (references see below)
- These basis sets were generated for our collaborative studies by:
- Dr. Jim Murdoch
- Principal Research Scientist
- Toshiba Medical Research Institute USA
- Mayfield Village, Ohio
- Email: jmurdoch@tmriusa.com
Details:
TE 68 basis sets (Dydak et al 2011) were generated from density matrix simulations of the sequence using published values for chemical shifts and J-couplings (Govindaraju et al 2000), with an exact treatment of metabolite evolution during the two frequency-selective MEGA inversion pulses. (In contrast, the localization pulses were assumed to be hard pulses, a simplification that fails to model the partial cancellation of GABA signal caused by chemical shift misregistration.) Difference basis spectra were obtained by averaging the simulated metabolite response to selective inversion at 1.9 and 7.5 ppm. Because the subtraction was assumed to be perfect, only those metabolites with resonances close to 1.9 ppm were included in the simulations: GABA, glutamate (Glu), glutamine (Gln), glutathione (GSH), NAA, and NAAG.
The original GABA coupling constants from Govindaraju et al have since been updated with somewhat more accurate values (e.g., Kaiser et al 2008; Kreis and Bolliger 2012; Near et al), all of which yield very similar TE 68 spectra. For the benefit of longitudinal studies, difference basis sets with both the Govindaraju and Kaiser values for GABA are included.
Basis sets for TE 68 edit-off spectra (i.e., 7.5 ppm selective inversion) are also supplied. For each of these, fourteen metabolite spectra were simulated: alanine, aspartate, creatine, GABA, Glu, Gln, GSH, glycerophosphorylcholine (GPC), lactate, myo-inositol, NAA, NAAG, scyllo-inositol, and taurine. (Small differences in the GABA lineshape don’t matter much when fitting edit-off spectra, so only the Kaiser values were used.)
DISCLAIMER: These basis sets are supplied “as is” for strictly research (not clinical) purposes. The entire risk regarding their quality and performance is with you.
References:
