FLAIR recovery

Another method to optimize image contrast includes the addition of an inversion recovery pulse before the typical SE sequence to suppress signal from cerebrospinal fluid (CSF). This yields so-called fluid-attenuated inversion recovery (FLAIR)-or CSF-suppressed DWI images or ADC maps. With this approach, the partial-volume effect of cerebrospinal fluid can be substantially reduced, which is particularly relevant in cortical regions due to the frequent CSF contribution to individual voxels (Latour and Warach 2002). The technique may enhance lesion conspicuity in the vicinity of CSF and has been shown to be of value in research studies utilizing pixel-wise analyses to predict tissue fate. The technique is not yet implemented in many centers, although this may change in the near future. 

Fig. 9.2. Fluid-attenuated inversion recovery (FLAIR, upper row) and T2-weighted (lower row) magnetic resonance images demonstrating early small focal lesions of leukoaraiosis...

FLAIR is an inversion recovery sequence with long repetition and echo times and an inversion time that is tailored to null the signal from CSF. Most pathologic processes including LA show increased signal intensities on T2-weighted images and the conspicuity of lesions located close to interfaces between brain parenchyma and CSF may be poor (Rumboldt and Marotti 2003). Additionally, the... 

Figure 18.1. MRI signal abnormalities in the brain and spinal cord in a 55-year-old woman with multiple sclerosis. (A) FLAIR (Fluid attenuated inversion recovery) image of axial brain image at the level of the lateral ventricles. Arrows point to hyperintense periventricular lesions demonstrating a characteristics MS demyelination pattern (B) T2W image of sagittal view of the spinal cord of the same individual, demonstrating focal bright signal (arrow) representing demyelination in the cervical spinal cord.

Amphetamines can be determined in hair by a GC-MS method following SFE (103). Flair was washed sequentially with sodium docecyl sulfate (SDS), CF12C12, methanol, and water and then dried. The amphetamines were extracted from the hair with 90% CO2 and 10% CFlCls/isopropyl alcohol at 262 bar and 70°C as the extractant in the dynamic extraction mode for 30 min. The amphetamine were derivatized and determined by GC MS. Mephenter-mine was used as an internal standard. The calibration graphs were linear from 0.02 to 20 ng/mg for all of the amphetamines studied. The detection limits were 0.02-0.1 ng/mg, the RSDs (five replicates) were 11-28%, and the recoveries were 71-84%. 

Fig. 9.5 Magnetic resonance imaging of the brain T2-weighted images using FLAIR (fluid attenuated inversion recovery) and FSE (fast spin echo) reveal enhanced signal intensity representing white matter abnormalities...

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