Table 2.

Neuroimaging vocabulary

Term	Acronym	Explanation
Amplitude	A	Distance from a wave’s equilibrium point to the crest of either a crest or trough.
Apparent Diffusion Coefficient	ADC	DTI measure of water molecule diffusion within brain tissue.
Arterial Spin Labeling/ Pseudocontinuous ASL	ASL/ pCASL	Structrual MRI technique that traces blood flow and tissue perfusion. Refinements such as pCASL allow for higher quality images.
Axial Diffusivity	AD	DTI measure of water molecule diffusion parallel to nerve tract.
Bandwidth	B	Band of frequencies between the upper and lower cut-off frequencies of a wave.
Beta Decay	ß-decay	Radioactive decay characterized by emission of an electron.
Blood-Oxygen-Level Dependent	BOLD	The change in fMRI signal between oxygenated and deoxygenated hemoglobin.
Computed Tomography	CT	Imaging technique that uses x-rays to generate anatomical images.
Cyclotron	–	Accelerator used for radionuclide production.
Cerebral Blood Flow	CBF	The amount of blood supplied to the brain at any given moment.
Cerebrospinal Fluid	CSF	Clear, colorless fluid that surrounds brain and spinal cord.
Deoxygenated Hemoglobin	Hb	Hemoglobin molecules in which there is no bound oxygen.
Diffusion Tensor Imaging	DTI	Structural MRI technique that measures water molecule diffusion along nerve fibers for direct visualization of white matter bundles.
Electroencephalography	EEG	Functional neuroimaging technique that maps brain activity using sensors placed on the scalp.
Fluid Attenuation Inversion Recovery	FLAIR	Structural MRI technique which suppresses CSF signal to provide image and is highly sensitive to pathological abnormalities.
Fractional Anisotropy	FA	DTI measurement of nerve fiber integrity.
Functional Magnetic Resonance Imaging	fMRI	MRI technique that measures blood oxygenation in the brain, so that assumptions may be made about both broad and specific brain functions.
Functional Neuroimaging	–	Neuroimaging technqiues that examines connectivity between brain regions.
Half-Life	t1/2	Time in which a radioactive atom undergoes radiactive decay.
Magnetic Resonance Imaging	MRI	Imaging technique that uses radiofrequency waves and a magnetic field to produce anatomical images.
Magnetoencephalography	MEG	Functional neuroimaging technique that maps brain activity using sensors placed around the scalp.
Mean Diffusivity	MD	DTI measure of water molecule diffusion overall all directions at a single point on a nerve tract.
Oscillation	–	Rhythmic frequency patterns in the CNS that occur during activation of either single neurons or neuronal clusters.
Photomultiplier Tubes	–	Part of PET machine that amplifys the signal of emitted positrons.
Positrons	e+, ß+	Subatomic particle with the same mass as an electron, but with a positive charged.
Positron Emission Tomography	PET	Functional neuroimaging technique that uses positron-emitting radionuclide tracers for in vivo imaging of biological, biochemical, and physiological processes.
Radial Diffusivity	RD	DTI measure of water molecule diffusion perpendicular to nerve tract.
Radio Frequency Pulse	RF	A magnetic field whose direction is oscilating at the Larmor frequency.
Radionuclide Tracer	–	A compound in which atoms have been replaced by their radioactive isotopes. In the context of imaging, these compounds are often biochemical analogues.
Region of Interest	ROI	A shape, coordinate, or anatomical region of the brain in which a researcher looks for activation or inactivation
Resting-State fMRI	rs-fMRI	fMRI technique that measure brain activity while at rest.
Scintillators	–	Photon detectors within a PET machine.
Signal to Noise Ratio	SNR	The ratio of fMRI signal to noise (background interference causing signal distortion). Higher SNR ratios indicate higher quality images. Noise control and reduction is especially important in fMRI research.
Structural Neuroimaing	–	Neuroimaging techniques that examine the structures of the brain.
Task-Evoked fMRI	–	fMRI technique that measures brain activity in response to a stimulus.
T1 or T2 Relaxation Time	–	T1 relaxation time describes the amount of time needed for the longitudinal magnetization vector to recover to 63% of its original strength after being flipped 90° into the transverse plane by an RF pulse. T2 relaxation time describes the amount of time it takes for the MR signal to decay to 37% of its original strength after tipping the longitudinal magnetization vector towards the transverse plane.
T1- or T2-Weighted	T1W/T2W	Body tissues have associated T1, T2, and Proton Density values, which depend on the tissue’s anatomy and chemical composition. For example, T1 image acquisition time is the time it takes for protons in a specific area to realign to the magnetic field after a RF pulse.
Voxel	–	A single volumetric unit of measurement within the brain. The dimensions of a voxel can differ between images based on the imaging technique used.
X-Ray	–	High-energy radiation capable of penetrating most tissue.
Tesla	T	A Tesla is a unit of measurement for magnetic flux density. MRI magnetic fields range commercially from 0.2 T to to 7T. Higher T values effectively indicate higher magnet strength.