Inversion Recovery SEQUENCE

Inversion Recovery

1. Sequence: Short tau inversion recovery

Abbr.: STIR

Physics: Fat suppression by setting an inversion time where the signal of fat is zero.

Tissues and their STIR appearance

Muscles: - darker than fat signal
White matter - darker than gray
Bone marrow: - dark
Moving blood- dark
Gray matter - gray
Fluids – very bright
Bone - dark
Fat – dark
Air - dark

Pathological appearance

Pathological processes normally increase the water content in tissues. Due to the added water component this results in a signal increase on STIR images. Consequently pathological processes are usually bright on STIR images.

Use

Very useful for brachial and lumbar plexus imaging
Very useful for anterior neck orbits and face imaging
Very useful for any musculoskeletal imaging
Very useful for extremity imaging
Very useful for spine imaging
Useful for abdominal imaging (respiratory gated STIR)
Useful for chest imaging (respiratory gated STIR)

Main Clinical distinctions: High signal in edema, such as in more severe stress fracture.

Shin splints pictured:

2. Sequence: Fluid-attenuated inversion recovery

Abbr.: FLAIR

Physics: Fluid suppression by setting an inversion time that nulls fluids

Tissues and their FLAIR appearance

Bone marrow: - equal to or higher than that of muscle (fatty marrow is usually bright)
White matter - darker than gray
Moving blood- dark
Gray matter - gray
Muscles -gray
Fat – bright
Fluids – dark
Bone - dark
Air - dark

Pathological appearance

Pathological processes normally increase the water content in tissues. The added water component results in a signal increase on FLAIR images. Consequently, pathological processes are usually bright on FLAIR images.

Use

Very useful for brain imaging
Useful for spine imaging

Main Clinical distinctions: High signal in lacunar infarction, multiple sclerosis (MS) plaques, sub-arachnoid hemorrhage and meningitis (pictured).