Capability of constructive interference in steady state sequence versus postcontrast T1-weighted imaging in cerebellopontine angle and internal auditory canal masses

Background: The tumor size is one of the main factors in the treatment of cerebellopontine angle (CPA) tumors, and magnetic resonance imaging (MRI) with gadolinium-based contrast agent (GBCA) provides the best evaluation. However, administration of the gadolinium is time consuming and increasing in cost. There is a risk of nephrogenic systemic fibrosis in patients with renal failure and liver or renal transplantation. Objective: The purpose of this study was to assess the capability of constructive interference in steady state (CISS) sequence in measuring the tumor size of the CPA and internal auditory canal (IAC) masses compared to postcontrast T1-weighted images (T1-WI). Materials and Methods: The 118 MR studies with both CISS sequence and postcontrast T1-WI of 45 patients with CPA and IAC masses were retrospectively reviewed. Results: There was no significant difference between CISS and postcontrast T1-WI in measuring size in transverse diameter of the masses (p = 0.051-0.06). The longitudinal diameter measurement revealed a significant difference (p < 0.001) and the measured size on postcontrast T1-WI was slightly larger than the CISS image. The difference in median measurement between two sequences was less than 0.9 mm. and Bland-Altman plots revealed that differences between the two sequences in longitudinal and transverse diameters of the masses were within the limits of agreement. Interobserver agreement showed excellent correlation (r = 0.994-0.999, p < 0.001 by Pearson's product-moment correlation). Conclusions: The CISS sequence may be sufficient for assessing the size of CPA and IAC masses, which can be used interchangeably with postcontrast T1-weighted image as a contrast-free option, especially in follow-up studies and vulnerable settings of gadolinium administration.