Abstract

FLAIR (Fluid-Attenuated Inversion-Recovery) is a new sequence applied in MR neuroimaging that uses signal suppression of tissues with lengthened relaxation time, e. g. of cerebrospinal fluid. FLAIR images are characterised with high contrast between normal cerebral tissues and pathological lesions. The aim of the study was to compare the diagnostic value of FLAIR as well as spin-echo sequences and CT images for the assessment of cerebrovascular lesions in patients with symptoms of cerebral circulatory failure. 102 patients were divided into two groups depending on subclinical and clinical form of cerebral ischaemic stroke. The following examinations were performed in all the subjects: CT, MR in standard spin-echo sequences (SE, FSE) as well as in fast spin-echo FLAIR sequence (FSE FLAIR) in 0.5 and 1.5 T. The analysis included the number, size, location and morphology of lesions, relating these to patients' clinical status. Diagnostic value of CT, SE and FLAIR were evaluated, assuming FLAIR as a reference method. Among patients with transient cerebral ischaemia, no lesions were detected in CT and MR examinations in 35% patients. CT sensitivity in lesion detection was 19.6% (p=0.0126), and in SE sequence - 68.6% in relation to FLAIR (p < 0.0001) at high specificity of both methods 100&percnt;. The lesions were detected in all the patients with cerebral infarction. MR usually confirmed the presence of stroke areas visible during CT, thus the sensitivity of both techniques in the detection of lesions was higher than in the previous group. CT sensitivity was 62.5% (p=0.0007), SE sequence - 79.1%in relation to FLAIR (p < 0.0001), specificity of both methods 100%.
LAIR allowed for the visualisation of more cerebrovascular lesions located in brain hemispheres (cortex and white matter), stem and cerebellum, while the number of lesions detected within basal ganglia and thalamus was similar. FLAIR images were highly sensitive in the detection of small gliosis foci, apoplectic cysts and secondary haemorrhagic lesions at various stages of evolution. They allowed for a more accurate assessment of the extent of foci and ischaemic zones, including early lesions, as well as for the differentiation of lacunar stroke from broadened Virchow-Robin spaces.
FLAIR method is particularly useful in the diagnostics of lesions located in the proximity of cerebrospinal fluid, especially for the detection of cortical foci. It enables the detection and differentiation of vascular foci at various stages of evolution, including early lesions that are not visualised in CT and standard MR imaging.

Keywords: Magnetic Resonance Imaging, spin-echo sequences, cerebral infarction, saturation, Diffusion-weighted imaging, Cerebrovascular Disorders