Identification of the Distal Dural Ring Using Three-dimensional Spin Echo Imaging: Application to Paraclinoid Aneurysms

Purpose: This study investigated the ability of three-dimentional motion-sensitized driven-equilibrium prepared T1-weighted fast spin echo (3D MSDE-FSE) imaging to identify distal dural rings (DDRs) and paraclinoid aneurysms (ParaC-ANs) and differentiate between intradural and extradural ParaC-ANs and compared it with that of established MR cisternography-based techniques. Methods: 3D MSDE-FSE images were acquired along with fast imaging employing steady state acquisition (FIESTA), and time-of-flight magnetic resonance angiography (TOF-MRA) on a 3T MRI system in 53 patients with unruptured and untreated ParaC-ANs. Two radiologists applied a 3-point scale to rate the clarity with which the DDR (53 left and 53 right) and ParaC-ANs (total of 55) were depicted in the 3D MSDE-FSE and FIESTA images. The clarity scores, which were determined by averaging the scores of the 2 assessors, on the 3D MSDE-FSE and FIESTA images were compared using the Wilcoxon signedrank test. Furthermore, the same radiologists classified the ParaC-ANs as intradural, extradural, or transitional on 3D MSDE-FSE images. A third radiologist independently classified the ParaC-ANs as intradural, extradural, or transitional based on the FIESTA and MRA fusion images. The kappa coefficient was used to compare this classification with that based on 3D MSDE-FSE images. Results: The Wilcoxon signed-rank test revealed no significant difference between 3D MSDE-FSE images and FIESTA images in the scores for the clarity of depiction of the DDRs (P = 0.119). However, the scores for the clarity of the depiction of the ParaC-ANs were significantly greater for the 3D MSDE-FSE images than for the FIESTA images (P < 0.001). The kappa coefficient for comparison of classification based on 3D MSDE-FSE images and FIESTA and MRA fusion images was 0.82. Conclusion: 3D MSDE-FSE imaging has the potential to differentiate between intradural and extradural ParaC-ANs by directly recognizing the DDR.