CT-like image based on 3D fast low-angle shot: superior diagnostic performance of ossification of the posterior longitudinal ligament.

Abstract

To evaluate the diagnostic performance of 3D fast low-angle shot (FLASH) compared with conventional MRI sequences for detecting OPLL. This retrospective study included 106 patients who underwent cervical spine MRI and CT. Thirty-nine and 67 patients were enrolled in the OPLL and control groups, respectively. Diagnostic performance and reader confidence for detecting OPLL were compared between conventional MRI using turbo spin echo (TSE) and conventional MRI plus 3D FLASH. Interobserver agreement was also calculated. Three subgroups were defined within the OPLL group according to the sequences required for detecting OPLL (TSE group: cases that were diagnosed as OPLL by reviewing only TSE; 3D FLASH group: cases that were diagnosed by reviewing both TSE and 3D FLASH; none group: cases that were not diagnosed on MRI). The thickness of the OPLL was compared between the subgroups. The diagnostic performance of both readers improved when 3D FLASH was added to conventional MRI, and the difference was statistically significant for reader 2 (p = 0.006). After adding 3D FLASH, reader confidence significantly increased (p < 0.001), and interobserver agreement improved from good to excellent. The three subgroups exhibited significantly different OPLL thicknesses (p = 0.008), with the thickest in the TSE group (4.5 mm), followed by the 3D FLASH (3.4 mm) and None groups (2.4 mm). 3D FLASH can be helpful for detecting OPLL when combined with conventional T1- and T2-weighted imaging.