Application Of Fluid-attenuated Inversion-recovery (flair) Sequence In Low Field Trength Mri Of The Brain

Objective:To analyzed the normal appearance of fluid-attenuated inversion-recovery (FLAIR) pulse sequences images in low field MRI of the brain and evaluate the value of clinical application of FLAIR sequences in cerebral diseases.Materials and methods:The study included 148 subjects (82 men and 66 women; age range,2～84 years; mean age,47.6 years) who were studied using SE-T1WI, FSE-T2WI and FLAIR sequence at axial sections.40 of all subjects were healthy, which were analyzed the characteristic of FLAIR images; 108 of all subjects were patients with various cerebral diseases, including 44 patients with cerebral infarction,30 with intracranial tumor, 18 with intracranial hemorrhage,10 with arachnoid cyst, and 6 with cerebral white matter demyelination disease. The FLAIR images and FSE-T2 weighted images were compared for detectability, conspicuity, characteristic of signal intensity and intrinsic structure of lesions.Results:(1) On normal FLAIR images, the signal from CSF was suppressed greatly, and high signal intensity were frequently seen in regions of the particular cerebral white matters and pituitary stalk. Ventricular CSF pulsation artifact (VCSFA) is commonly found in the third and fourth ventricles on axial FLAIR images. (2) Lesion detection:264 lesions were identified with MRI in the 108 patients. FLAIR images detected 261 (98.86%), and FSE-T2 weighted images,233 (88.26%) of the 264 lesions. The difference in lesion detection between them approached statistical significance (p<0.01). (3) Lesion conspicuity:243 (93.10%) lesions were clear with FLAIR images in demonstrating the border of lesions, and 180 (77.25%) ones with FSE-T2 weighted images. The difference in lesion conspicuity between them is statistically significant (p<0.01). (4) Signal intensity: On FSE-T2 weighted images, the signal intensity of lesions was single, only two of them were middle signal intensity, the rest were hyperintense. However, on FLAIR images, the signal intensity of lesions was multiple,3 lesions were middle signal intensity,29 ones were hypointense,16 ones were hypointense centrally with a thin peripheral rim of hyperintensity, the rest were hyperintense. Moreover, FLAIR images showed the intrinsic structure of lesions more clearly than FSE-T2 weighted images.Conclusion:In low field MRI of the brain, there were special appearances on FLAIR images which were different from FSE-T2 weighted images. The FLAIR sequence can reduce greatly the signal from CSF, which produced high lesion contrast in areas close to CSF. Lesions were demonstrated with greater conspicuity on FLAIR images than FSE-T2 weighted sequences in patients with cerebral diseases. Moreover, it is more helpful to diagnose and distinguish from intracranial diseases with the characteristic of lesion's signal on FLAIR images than FSE-T2 weighted images. Therefore, FLAIR sequence can be used as a conventional sequence of the examination in low field MRI of the brain.