MRI T2-weighted imaging and fat-suppressed T2-weighted imaging image fusion technology improves image discriminability for the evaluation of anal fistulas

Abstract

Objective: To explore whether MRI fusion technology (combined T2-weighted imaging [T2WI] and fat-suppressed T2WI [T2WI -FS ]) improves signal differences between anal fistulas and surrounding structures. Materials and Methods: A total of 32 patients with confirmed diagnoses of anal fistula were retrospectively studied. All available T2WI and T2WI -FS images for each patient were used to generate fusion image (T2WI -Fusion ) based on the addition of gray values obtained from each pixel via an MR post-processing work station. The discriminability of fistula, perianal sphincter, and perianal fat in T2WI, T2WI -FS , and T2WI -Fusion images was quantified with Fisher’s scoring algorithm. For subjective visual image assessment by researchers, five-point scale scores were determined using a modified double-stimulus continuous quality-scale test to evaluate T2WI -FS , T2WI, enhanced axial three-dimensional-volumetric interpolated breath-hold examination (3D-VIBE), and T2WI -Fusion sequence images. The differences were subsequently compared. Results: Mean Fisher scores for fistulas vs. sphincters obtained from T2WI -Fusion (FFusion -fistula = 6.56) were significantly higher than those from T2WI (FT2WI -fistula = 3.35) (p = 0.001). Mean Fisher scores for sphincters vs. fat from T2WI -Fusion (FFusion -sphincter = 10.84) were significantly higher than those from T2WI-FS (FSFS -sphincter = 2.57) (p = 0.001). In human assessment, T2WI-Fusion showed the same fistula discriminability as T2WI -FS , and better sphincter discriminability than T2WI. Overall, T2WI -Fusion showed better discriminability than T2WI, T2WI -FS , and enhanced 3D-VIBE images. Conclusion: T2WI and T2WI-FS fusion technology improves signal differences between anal fistulas and surrounding structures, and may facilitate better evaluation of anal fistulas and sphincters.