Agreement and Repeatability of Linear Vertebral Body and Canal Measurements Using Computed Tomography (CT) and Low Field Magnetic Resonance Imaging (MRI)

Objective To evaluate agreement and repeatability of vertebral column measurements using computed tomography (CT) and magnetic resonance imaging (MRI). Study Design Retrospective observational study. Animals Dogs (n=18) with disc associated wobbler syndrome; Dog cadavers (n=3). Methods Five measurements of the 5th cervical vertebra were performed: vertebral body length (VBL), vertebral canal height (VCH), vertebral body height (VBH), vertebral canal width (VCW), and vertebral body width (VBW). Measurements were performed independently twice by 2 observers. Bland-Altman plots were created to evaluate agreement. Cadaveric vertebrae with soft tissue removed had the same variables and actual dimensions measured. Results The largest discrepancy between CT and MRI measurement was for VBL (mean difference +/- SD=1.262 mm +/- 1.245; P <.001), with the difference for all the other variables being acceptable. The 1st measurement was significantly higher than the 2nd only for VBL using CT (mean difference=0.476 mm +/- 1.120; P=.009), with all other variables having acceptable differences. Mean difference for all measurements between 2 observers was small, except for VBL using CT (mean difference=0.762 mm +/- 1.042; P <.001). Only the difference for VBL between CT and cadaver specimens was statistically significant. Conclusions Our results suggest high repeatability and good agreement for most vertebral measurements of interest. VBL measurement using CT was considered problematic. Clinical Relevance Provided limitations are understood, linear measurements of vertebral dimensions from CT and MRI images can be used clinically.