FLAIR with BLADE results in increased flow related artefact in the subarachnoid space.

Purpose: To compare the extent and intensity of FLAIR CSF flow related artefacts with and without BLADE (motion correction with multiple radial blade acquisition). Methods and materials: Retrospective review of 22 patients who received FLAIR with and without BLADE. Patients were scanned on three different scanners, two of which are 1.5T, the remainder being 3T. The CSF spaces in the pre-pontine cistern were evaluated for presence of flow related artefact. The cases were blindly assessed by an experienced neuroradiologist (SS) and an MRI fellow (CF). Extent/ Intensity of artefact was assessed on a four point scale (ranked 0-3). Result(s): Flow related artefact was identified on 17 of 22 BLADE studies and 16 of 22 rectilinear FLAIR. The average score based on the four point scale was 1.67 for BLADE and 0.81 for rectilinear FLAIR. The effect was much more pronounced at 3T. Average scores for 3T BLADE was 2.13 compared to 1.00 on rectilinear FLAIR. At 1.5T average scores were 0.43 for BLADE and 0.29 for FLAIR. Conclusion(s): Despite being widely regarded as having less pulsation, ghosting and movement artefacts when compared to conventional FLAIR sequences; BLADE FLAIR images demonstrate increased CSF flow related artefact extent and intensity in the prepontine cistern. The FLAIR with BLADE appearances may mimic the appearance of subarachnoid haemorrhage whereas conventional FLAIR on modern MRI equipment is less likely to result in this appearance. This effect is more pronounced on 3T field strengths when compared to 1.5T. Awareness of this difference may assist in avoiding a false positive subarachnoid haemorrhage diagnosis when FLAIR has been acquired with the BLADE technique.