MR cisternography of the cerebellopontine angle: Comparison of three-dimensional fast asymmetrical spin-echo and three-dimensional constructive interference in the steady-state sequences

BACKGROUND AND PURPOSE: MR cisternography has been used as the noninvasive screening tool of the cerebellopontine angle. The purpose of this study was to directly compare two currently dominant types of sequences for heavily T2-weighted MR cisternography. METHODS: Three-dimensional fast asymmetric spin-echo (3D-FASE) sequences, w hich are 3D half-Fourier rapid acquisition with relaxation enhancement and 3D constructive interference in the steady-state (3D-CISS) sequences, were compared on a clinical 1.5-T MR unit using the same scan times. In five hea lthy volunteers, the contrast-to-noise ratio (CN) between CSF and the cereb ellum was measured at three locations. Then, for qualitative analysis, the quality of the labyrinth was scored on the original source multiplanar refo rmatted images, the virtual endoscopic images, and the maximum intensity pr ojection (MIP) images. In 20 consecutive patients with suspected cerebellop ontine angle tumors, visualization of the tumors was evaluated using 3D con trast-enhanced spoiled gradient-echo imaging as the standard of reference. RESULTS: Both sequences showed comparable mean C/N values; however, in qual itative analysis, the scores for 3D-CISS on the source, virtual endoscopic, and MIP images were significantly lower than those on the images obtained with 3D-FASE, owing to more prominent flow and magnetic susceptibility arti facts on the 3D-CISS sequences. In all subjects, discontinuity of the semic ircular canals was seen on the virtual endoscopic and MIP images obtained w ith 3D-CISS, owing to susceptibility artifacts, but not on those obtained w ith 3D-FASE. All 12 tumors were detected by both sequences, but 3D-CISS gav e one false-positive result. CONCLUSION: 3D-FASE is considered the method of choice because artifacts ar e reduced and specificity is increased.