Diagnostic Accuracy of the Constructive Interference in Steady State Sequence Alone for Follow-Up Imaging of Vestibular Schwannomas

BACKGROUND AND PURPOSE: Vestibular schwannoma (VS) is a benign, slow-growing tumor, and radiologic monitoring is an acceptable alternative to surgery in small lesions and in elderly patients, MR imaging with contrast is the study of choice in the follow-up of these lesions. However, gadolinium-based contrast agents have side effects and should be used only when definitely indicated. The purpose of this study was to evaluate the diagnostic accuracy of the constructive interference in steady state (CISS) sequence used without postcontrast sequences for the follow-up imaging of VS. MATERIALS AND METHODS: MR imaging examinations of 18 patients were retrospectively evaluated by 2 radiologists. VS masses were measured on both CISS and the postcontrast images by each observer. For each patient, the masses were also assessed qualitatively for possible progression between every consecutive study. RESULTS: Fifty MR images of 18 patients were evaluated. Patients had 1-5 follow-up studies. The mean time interval between the consecutive studies was 23 months (6-55 months). The sensitivity, specificity, and accuracy of the CISS sequence for the detection of progression were 100%. There was good interobserver and intraobserver (CISS and postcontrast) correlation. The CISS sequence had, however, limited sensitivity for the detection of changes in the internal architecture. CONCLUSIONS: Noncontrast CISS-only technique may be a viable alternative to routine contrast-enhanced sequences for the follow-up of overall lesion size in patients with VS; however, treatmen-trelated changes internal to the tumor are less noticeable using the CISS sequence.