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AJNR - American Journal of Neuroradiology

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Applicability and Advantages of Flow artifact–insensitive Fluid-attenuated Inversion-recovery MR Sequences for Imaging the Posterior Fossa

Norimitsu Tanaka^,a, Toshi Abe^a, Kazuyuki Kojima^a, Hiroshi Nishimura^a and Naofumi Hayabuchi^a

^a From the Department of Radiology, Kurume University School of Medicine, 67, Asahimachi, Kurume, 830-0011, Japan.

View larger version (134K): [in a new window]   FIG 1. Conventional FLAIR images showing artifacts in the cerebellopontine angle cistern (A) and in the third ventricle (B). By combining the information from two reverse-ordered sequences, Scan 1 (C, D) and Scan 2 (E, F), the FAIS-FLAIR images result in a conspicuous absence of flow-related FLAIR artifacts (G, H). It is a simple summation of images, which are processed automatically in line with the image-array processor. Note flow-related artifacts lessen on Scan 1 and Scan 2, but image contrast is not constant. On Scan 1, signal intensity is increasing from C to D, whereas on Scan 2, it is decreasing from E to F.

View larger version (19K): [in a new window]   FIG 2. The FAIS-FLAIR sequence consisted of two scans. On the first scan, a 180° inversion prepulse is nonselectively applied to the whole brain, and is then followed by a multislice fast spin-echo sequence. The intent of the prepulse is to null the water-dependent signal by inducing a delay before the center-slice ex

View larger version (97K): [in a new window]   FIG 3. A vestibular schwannoma is demonstrated on multiple images in a 58-year-old woman, including unenhanced conventional FLAIR (A), unenhanced (B) and enhanced (C) FAIS-FLAIR, and T1-weighted (D) images. FAIS-FLAIR shows the tumor in the cerebellopontine cistern more clearly than does T1-weighted imaging. The same lesion is even more visible with postcontrast FAIS-FLAIR imaging. On the FLAIR image, the tumor is depicted, but inflow artifacts in the cerebellopontine and prepontine cistern interfere with interpretation citation. The second scan consists of parameters similar to the first, with the exception that each slice is excited in reverse order. TI* means the interval between 180° inversion prepulse and the excitation pulse of the center slice

View larger version (15K): [in a new window]   FIG 4. The T1 shortening effect with MR contrast agents results in an upward shift of the T1 relaxation curve during FLAIR imaging