Reduction of CSF and blood flow artifacts on FLAIR images of the brain with k-space reordered by inversion time at each slice position (KRISP)

BACKGROUND AND PURPOSE: Our purpose was to test a new variant of the fluid- attenuated inversion-recovery (FLAIR) sequence that was designed to reduce CSF and blood flow artifacts by use of a non-slice-selective e inversion pu lse and k-space reordered by inversion time at each slice position (KRISP). METHODS: With the KRISP FLAIR sequence, the slice order was cycled so that each inversion time (TI) was associated with a region of k-space rather tha n a particular slice, and the effective inversion time (TIeff) was chosen t o null the signal from CSF. Scans were obtained with both conventional and KRISP FLAIR sequences. Studies were performed in 20 adult patients with a v ariety of brain diseases. Images were evaluated for artifacts from patient motion, CSP, and blood how, and scored on a four-point scale. The conspicui ty of the cortex! meninges, ventricular system, brain stem, and cerebellum was evaluated, as was lesion number and conspicuity. RESULTS: The KRISP FLAIR sequence showed more patient motion artifacts but had a pronounced advantage over the conventional sequence in control of CSP artifacts around the foramen of Munro, in the third ventricle, aqueduct, a nd fourth ventricle, as well as in the basal cisterns and around the brain stem and cerebellum. Blood flow artifacts from the internal carotid, basila r, and vertebral arteries were also much better controlled. Spurious high s ignal in the sylvian branches of the middle cerebral artery was eliminated. The meninges, cortex, ventricular system, brain stem, and cerebellum mere better seen dug to improved artifact suppression and an edge enhancement ef fect. CONCLUSION: The KRISP FLAIR sequence can suppress CSF and blood dow artifac ts and improve the conspicuity of the meninges, cortex, brain stem, and cer ebellum. Its major disadvantage is its duration, which may he reducible wit h a fast spin-echo version.