Table V. Magnetic resonance imaging (MRI) neuroimaging techniques. BOLD, blood oxygen level dependent; DTI, diffusion tensor imaging, fMRI, functional MRI; MRS, magnetic resonance spectroscopy; PW-MRI, perfusion weighted MRI; SWI, susceptibility-weighted imaging Reproduced with permission from ref 37: Van Boven RW, Harrington GS, Hackney DB, et al. Advances in neuroimaging of traumatic brain injury and posttraumatic stress disorder. J Rehabil Res Dev. 2009;46:717-757. Copyright © Dept of Veterans' Affairs 2009.

Technique	What it measures	Applications
BOLD fMRI	Indirect measure of blood flow, BOLD signal changes originate in venules BOLD f MRI takes advantage of susceptibility differences between oxygenated and deoxygenated blood.	Evaluate regional brain activity related to particular cognitive tasks or sensory/motor stimulation Evaluate brain networks related to cognitive states Evaluate brain “resting state ” or “default ” networks.
PW-MRI	Direct measure of blood flow, allows quantification of blood perfusion.	Assess brain perfusion or resting cerebral blood flow Evaluate brain function in manner similar to fMRI.
DTI	Indirectly measures diffusion of water molecules. Mean diffusion, diffusion direction, and anisotropy white matter tracts.	Use diffusion anisotropy measures as marker of disease. Improved visualization of edema. Evaluate structural “connectivity ” between brain regions.
MRS	Proton (1H) MRI spectra typically contain signals from the metabolites N-acetylaspartate, creatine, Choline, glutamate/glutamine, and myo-inositol.	Evaluate changes in brain metabolites related to myelination, neuronal density, edema, etc.
SWI	MRI sequences that are especially sensitive to changes in magnetic susceptibility, in particular blood	Improved detection of hemorrhages Improved imaging of blood vessels.