Magnetic Resonance Imaging with Fluid Attenuated Pulse Sequences in Evaluation of Craniospinal Lesions

Abstract

Once obtained, T2 weighted sequences generally constitute a fundamental element in the study of craniospinal pathology, provided that they determine the signal hyperintensity of lesions which are clearly visible against the surrounding tissue.

A sequence was recently introduced into clinical practice which allows for attentuation of cerebrospinal fluid signals. Here, a change in the tissue becomes the point, during the scan, at which the signal is at its most intense.

This sequence, named “Fluid Attenuated Inversion Recovery” (FLAIR), suppresses the free water signals and thus the cerebrospinal fluid, while the parenchymal lesions retain their hyperintensity. FLAIR uses a technique which selectively eliminates the fluid signal with a sequence of very long echoes, thereby determining substantial T2 weighted images. Using a 0.5T system, we tried to determine in which pathologies the sequences could be used, other than the already well documented application in demyelinating pathology, by comparing spin-echo and FLAIR sequences.

The results obtained confirm that the FLAIR sequence can have further application in vascular pathology; in the evaluation of ischaemic junctional lesions; in some neoplastic pathologies; in mesial temporal sclerosis and in the potential evaluation of extra-axial haematomas.

Overall, a greater number of lesions was identified using FLAIR. Certainly the identification of cortical-subcortical lesions, both in vascular and demyelinating pathologies has benefitted most from this new sequence. In particular, a greater number of small ischaemic junctional lesions was detected, with a high level of correspondence between clinical data and magnetic resonance findings, even in patients without lesions in other sites.

In conclusion, despite the fact that the FLAIR sequence involves an execution time of approximately seven minutes and must only be conducted following standard examination with the application of the base spin-echo sequence, it provides a further tool in the identification of craniospinal pathologies.