MR cisternography with fast imaging employing steady-state acquisition (FIESTA)

Learning objectives: to illustrate the main features of FIESTA sequence, and its advantages over other MR imaging sequences in imaging cisternal parts of cranial nerves V-VII-VIII. Background: FIESTA sequence generates T2/T1 contrast because of its short repetition time (TR) and the symmetrical and balanced gradient around the echo time (TE), it provides very high signals from tissues with large T2/T1 ratios, such as fluid, blood, and fat. Scanning time is shorter than in conventional CISS and FISP, movement and flow artifacts occur less often than with other sequences. The contrast to noise ratio (CNR) is higher. Blurring artifacts occur less often because the MR signal is always achieved in a coherent state. Magnetic susceptibility artifacts occur with lower frequency due to very short TE and wide band thickness. Imaging findings: We assessed FIESTA sequence’s performance in patients with V-VII-VIII cranial nerve’s related symptoms. In cases of posterior fossa tumors, FIESTA sequence depicted clearly tumor’s extension and facilitated a superior assessment of tumor’s effect on cranial nerve anatomy. When a neuro-vascular conflict was suspected FIESTA identified in all patients the anatomical relationship between vascular structures and trigeminal, facial and cochleovestibular nerves. Moreover volumetric 3D acquisition allowed very high quality from multiplanar reformations using minimum intensity projection (min-IP) algorithm. Conclusion: 3D FIESTA sequences are superior to other heavily T2-weighted sequences in visualizing cisternal parts of the posterior fossa cranial nerves for the following reasons: high-resolution, short acquisition time, less artifacts from CSF pulsation and magnetic susceptibility. Thus high quality images can be obtained.