Fluid attenuated inversion recovery

Overview
Fluid Attenuated Inversion Recovery (FLAIR) is a pulse sequence used in Magnetic Resonance Imaging.

The pulse sequence is an inversion recovery technique that nulls fluids. For example, it can be used in brain imaging to suppress Cerebrospinal fluid (CSF) so as to bring out the periventricular hypertintense lesions, such as multiple sclerosis (MS) plaques.

By carefully choosing the TI, the signal from any particular tissue can be nulled. The appropriate TI depends on the tissue via the formula:

TI = ln2 * T1

One should typically yield a TI of 70% of T1. In the case of CSF suppression, one aims for T2 weighted images.