Contrast-enhanced CISS MRI of vestibular schwannomas: Phantom and clinicalstudies

Purpose: The purpose of this work was to assess the changes of signal inten sity on constructive interference in steady state (CISS) 3D Fourier transfo rmation (3DFT) MRI after administration of Gd-DTPA and to evaluate the effi cacy of contrast-enhanced CISS-3DFT MRT to depict the seventh and eighth cr anial nerves affected by vestibular schwannomas. Method: All scans were carried out on a 1.5 T MR unit. First, an experiment al study was conducted to evaluate the changes in signal intensity of the C ISS-3DFT sequence in relation to the concentration of contrast medium. Seco nd, nine consecutive patients with 11 vestibular schwannomas underwent CISS -3DFT imaging before and after contrast agent administration. Signal intens ities of the tumors and nerves were measured and compared between the pre- and postcontrast images. Visualization of the facial and cochlear nerves wa s rated on pre- and postcontrast CISS imaging independently, Results: On the phantom study, the CISS-3DFT sequence showed a constant inc rease in signal intensity as the concentration of Gd-DTPA increased. The co ntrast between the nerves and tumors significantly increased after contrast agent administration (from 0.1 to 9.0 as mean contrast-to-noise ratio). Th e ability to depict the nerves was also significantly higher for postcontra st CISS-3DFT imaging than for precontrast. Conclusion: Although the CISS-3DFT sequence offers similar contrast as othe r heavily T2-weighted sequences, the signal intensity of contrast-enhanced tumors increased on CISS-3DFT imaging. Contrast-enhanced CISS imaging was v aluable for evaluating the seventh and eighth cranial nerves affected by ve stibular schwannomas.