MRI pulse sequence

An MRI pulse sequence in magnetic resonance imaging (MRI) is a particular setting of pulse sequences and pulsed field gradients, resulting in a particular image appearance.

A multiparametric MRI is a combination of two or more sequences, and/or including other specialized MRI configurations such as spectroscopy.

Overview table

This table does not include uncommon and experimental sequences.

Group	Sequence	Abbr.	Physics	Main clinical distinctions	Example
Spin echo	T1 weighted	T1	Measuring spin–lattice relaxation by using a short repetition time (TR) and echo time (TE).	Lower signal for more water content, as in edema, tumor, infarction, inflammation, infection, hyperacute or chronic hemorrhage. High signal for fat High signal for paramagnetic substances, such as MRI contrast agents Standard foundation and comparison for other sequences
	T2 weighted	T2	Measuring spin–spin relaxation by using long TR and TE times	Higher signal for more water content Low signal for fat in standard Spine Echo (SE), though not with Fast Spin Echo/Turbo Spin Echo (FSE/TSE). FSE/TSE is the standard of care in modern medicine because it is faster. With FSE/TSE, fat has high signal due to disruption of hyperfine J-coupling between adjacent fat protons. Low signal for paramagnetic substances Standard foundation and comparison for other sequences
	Proton density weighted	PD	Long TR (to reduce T1) and short TE (to minimize T2).	Joint disease and injury. High signal from meniscus tears. (pictured)
Gradient echo (GRE)	Steady-state free precession	SSFP	Maintenance of a steady, residual transverse magnetisation over successive cycles.	Creation of cardiac MRI videos (pictured).
	Effective T2 or "T2-star"	T2*	Spoiled gradient recalled echo (GRE) with a long echo time and small flip angle	Low signal from hemosiderin deposits (pictured) and hemorrhages.
	Susceptibility-weighted	SWI	Spoiled gradient recalled echo (GRE), fully flow compensated, long echo time, combines phase image with magnitude image	Detecting small amounts of hemorrhage (diffuse axonal injury pictured) or calcium.
Inversion recovery	Short tau inversion recovery	STIR	Fat suppression by setting an inversion time where the signal of fat is zero.	High signal in edema, such as in more severe stress fracture. Shin splints pictured:
	Fluid-attenuated inversion recovery	FLAIR	Fluid suppression by setting an inversion time that nulls fluids	High signal in lacunar infarction, multiple sclerosis (MS) plaques, subarachnoid haemorrhage and meningitis (pictured).
	Double inversion recovery	DIR	Simultaneous suppression of cerebrospinal fluid and white matter by two inversion times.	High signal of multiple sclerosis plaques (pictured).
Diffusion weighted (DWI)	Conventional	DWI	Measure of Brownian motion of water molecules.	High signal within minutes of cerebral infarction (pictured).
	Apparent diffusion coefficient	ADC	Reduced T2 weighting by taking multiple conventional DWI images with different DWI weighting, and the change corresponds to diffusion.	Low signal minutes after cerebral infarction (pictured).
	Diffusion tensor	DTI	Mainly tractography (pictured) by an overall greater Brownian motion of water molecules in the directions of nerve fibers.	Evaluating white matter deformation by tumors Reduced fractional anisotropy may indicate dementia.
Perfusion weighted (PWI)	Dynamic susceptibility contrast	DSC	Measures changes over time in susceptibility-induced signal loss due to gadolinium contrast injection.	Provides measurements of blood flow In cerebral infarction, the infarcted core and the penumbra have decreased perfusion and delayed contrast arrival (pictured).
	Arterial spin labelling	ASL	Magnetic labeling of arterial blood below the imaging slab, which subsequently enters the region of interest. It does not need gadolinium contrast.
	Dynamic contrast enhanced	DCE	Measures changes over time in the shortening of the spin–lattice relaxation (T1) induced by a gadolinium contrast bolus.	Faster Gd contrast uptake along with other features is suggestive of malignancy (pictured).
Functional MRI (fMRI)	Blood-oxygen-level dependent imaging	BOLD	Changes in oxygen saturation-dependent magnetism of hemoglobin reflects tissue activity.	Localizing brain activity from performing an assigned task (e.g. talking, moving fingers) before surgery, also used in research of cognition.
Magnetic resonance angiography (MRA) and venography	Time-of-flight	TOF	Blood entering the imaged area is not yet magnetically saturated, giving it a much higher signal when using short echo time and flow compensation.	Detection of aneurysm, stenosis, or dissection
Magnetic resonance angiography (MRA) and venography	Phase-contrast magnetic resonance imaging	PC-MRA	Two gradients with equal magnitude, but opposite direction, are used to encode a phase shift, which is proportional to the velocity of spins.	Detection of aneurysm, stenosis, or dissection (pictured).	(VIPR)