Research applications of magnetic resonance spectroscopy to investigate psychiatric disorders

Abstract

Advances in magnetic resonance spectroscopy (MRS) methodology and related analytic strategies allow sophisticated testing of neurobiological models of disease pathology in psychiatric disorders. An overview of principles underlying MRS, methodological considerations, and investigative approaches is presented. A review of recent research is presented that highlights innovative approaches applying MRS, in particular, hydrogen MRS, to systematically investigate specific psychiatric disorders, including autism spectrum disorders, schizophrenia, panic disorder, major depression, and bipolar disorder.

Figure 1

Time domain free induction decay (left-hand side) and frequency domain Fourier transform (right-hand side) of brain 1H MRS signal. The top and bottom panels demonstrate spectra without and with water suppression, respectively.

Figure 2

3-D spatial chemical concentration maps at different acquisition times (using SENSE acceleration to reduce the number of phase-encoding steps) are shown on the left-hand side, with corresponding spectral fitting error maps (RMS-ERROR) calculated in comparison to the non-accelerated reconstruction (R=1×1) acquired at 8 minutes for a) NAA, b) Creatine and c) Choline. Cramer-Rao lower bound (CRLB) is shown on the right-hand side for each chemical concentration map. CRLB is the error term resulting from spectral fitting to the LC apriori model used to determine chemical concentration. (Figure provided by Dr. Ricardo Otazo)

Figure 3

a) 3-D spatial chemical concentration maps and Cramer-Rao lower bound (CRLB) maps for Glutamate (Glu) at different acquisition times using SENSE to reduce the number of phase-encoding steps. CRLB is the error term resulting from spectral fitting to the LC apriori model used to determine chemical concentration. b) Raw absorption mode spectrum (black line) and corresponding LCModel fit (red line) for a gray matter (GM) voxel and a white matter (WM) voxel (voxel locations are indicated in part a). The remaining baseline is given by the smooth black curve. The concentration of Glutamate is given in each example. (Figure provided by Dr. Ricardo Otazo)

Figure 4

Proton echo-planar spectroscopic image (PEPSI) NAA spatial distribution map shown in orange (top panel) and corresponding anatomical atlas (bottom panel) both of which are overlaid onto a MRI structural image. Each color in the atlas represents a different brain region (http://www.sph.sc.edu/comd/rorden/mricro.html).

Figure 5

Superimposed individual raw spectral acquisitions from the left frontal lobe, after filtering out spectra with artifact. These spectra are then averaged to obtain a single spectrum for this brain region.

Figure 6

LC Model fit of averaged spectra acquired from the left frontal lobe. Black line: averaged spectrum. Red line: the LC Model fit. The residuals, calculated as a subtraction of the fit from the average spectrum, are plotted at the top. The table of metabolite concentrations calculated from the fit is to the right.