Imaging Glossary
B-value – Indicative of the timing/strength of gradients in diffusion MRI scans; higher b-values capture more information about diffusion at the cost of a higher signal-to-noise ratio; two b-vals (b1000 and b2000) are required for DKI
dicom – the format in which MRI data is stored initially after acquisition
Diffusion metrics
FA – fractional anisotropy; describes the degree to which diffusion within a voxel is isotropic (free diffusion in all directions) or anisotropic (highly aligned structures driving diffusion in a specific direction); 0 = completely isotropic, 1 = complete anisotropic
MD – mean diffusivity; describes the magnitude of diffusion
RD – radial diffusivity; describes the magnitude of diffusion perpendicular to a fiber tract
AD – axial diffusivity; describes the magnitude of diffusion parallel to a fiber tract
Hyperintensity/hypointensity – a cluster of voxels at a markedly higher/lower intensity (appearing brighter) than those around it
Intensity – the measure of tissues as reflected in the brightness or darkness of each voxel
Kurtosis metrics - describe non-Gaussianity
MK (mean kurtosis)
AK (axial kurtosis)
RK (radial kurtosis)
nifti – an MRI data format that compiles all dicoms in a sequence into a viewable 3D image
Normalization – The process of warping an image or many images into a common space.
This may involve warping all images into an average space or, more often, warping all images into a standard space (such as MNI space)
Preprocessing – the process of removing image artifacts and performing necessary corrections to raw MRI data; types of corrections performed during preprocessing
Denoising
Unringing
EPI Distortion Correction
ROI - Region of interest; a specific part of the brain of interest to a specific analysis pipeline
Registration – The process of spatially aligning 2+ images
Sequence – The specific type of scan that was performed when the patient/participant was in the MRI scanner; eg. Diffusion weighted (DKI, DTI, FBI, etc), T1MPRAGE, T2 FLAIR, proton density (PD), MR spectroscopy (MRS), etc.
T1 Weighted (T1W/MPRAGE) – high res anatomical image included is basically every scan ; white matter appears more light, grey matter appears more mid-ranged grey, CSF appears dark grey or black
T2 Weighted (T2W/FLAIR)
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