"Disk extension beyond the interspace": an investigation into an alternative nomenclature in diagnostic imaging for displaced canine intervertebral disk material

Abstract

Background: Displacement of canine intervertebral disk material can be seen directly in diagnostic imaging modalities such as magnetic resonance imaging and computed tomographic imaging. Canine intervertebral disk herniation can be differentiated into Hansen type 1 and 2 categories by clinical appearance, but anular- and nuclear disk material cannot be distinguished in computed tomographic images. Therefore, we hypothesized that the "Disk extension beyond the interspace"-nomenclature that describes the displacement by the disk contour might aid diagnosis. The aim of this study was to test the reliability of the "Disk extension beyond the interspace"-nomenclature in the evaluation of canine intervertebral disks via magnetic resonance and computed tomographic imaging.

Results: Magnetic resonance and computed tomographic images of 144 intervertebral disks of 43 dogs were evaluated by 3 observers with different degrees of experience from 2 institutions retrospectively. A substantial intraobserver agreement was found, while interobserver agreement was fair to moderate with significant differences in evaluation. Comparison of imaging methods showed a fair to moderate agreement without statistically significant differences in evaluation.

Conclusions: DEBIT-nomenclature cannot be recommended for veterinary clinical usage yet. The largest variability was found in the evaluation of the bulged canine intervertebral disk. The observers' experience and the imaging method influenced DEBIT- evaluation only slightly, while training and working at different institutions influenced DEBIT-evaluation strongly.

Figure 1

DEBIT in the three imaging methods DEBIT in magnetic resonance and computed tomographic imaging; for each DEBIT category images of the same intervertebral disk are shown in: (A), T2-weighted transverse Turbo Spin Echos sequence; (B), T1-weighted multi-Fast-Field-Echo sequence; (C), transverse computed tomography.

Figure 2

Evaluation of DEBIT of all observers in MRI and CTThe bars show the number of intervertebral disks that were evaluted as being normal, bulged, protruded, extruded and sequestrated. Each bar is the mean value of two classification sessions of one observer. A): Classification of DEBIT using T2W_TSE images; B): Classifiacation of DEBIT using mFFE images; C): Classification of DEBIT using CT images.