Fluid attenuated inversion recovery (FLAIR)

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Parent item

MRI

General

• Suppresses CSF

• A T2 based Sq

Hyperintense

• Acute blood

• Pus

Used to

• Differentiate arachnoid cyst from other cystic pathologies

• Differentiate SAH on T2 from CSF

Differentiating

FLAIR

T1 pre contrast

Process

1. Inversion Pulse
• A 180° radiofrequency pulse is applied to invert the magnetization of the protons in the tissue.

2. Inversion Time (TI)
• After the inversion pulse, there is a delay known as the inversion time. During this time, the protons recover their longitudinal magnetization.
• The key feature of FLAIR is that the inversion time set long to nullify the signal from fluids like CSF, making it appear dark on the resulting images.
• This enhances the contrast between fat and other tissues, making fluid-filled regions, edema, and inflammation stand out more prominently.

3. Excitation Pulse
• A 90° radiofrequency pulse is then applied to excite the protons.

4. Signal Measurement
• The MRI scanner measures the resulting signal.