J Vet Sci.  2009 Sep;10(3):225-232. 10.4142/jvs.2009.10.3.225.

Effect of multi-planar CT image reformatting on surgeon diagnostic performance for localizing thoracolumbar disc extrusions in dogs

• King JB
• Jones JC
• Rossmeisl
• Harper TA
• Lanz OI
• Werre SR

• KMID: 1726922
• DOI: http://doi.org/10.4142/jvs.2009.10.3.225

Abstract

Accurate pre-operative localization and removal of disc material are important for minimizing morbidity in dogs with thoracolumbar disc extrusions. Computed tomography (CT) is an established technique for localizing disc extrusions in dogs, however the effect of multi-planar reformatting (MPR) on surgeon diagnostic performance has not been previously described. The purpose of this study was to test the effect of MPR CT on surgeon diagnostic accuracy, certainty and agreement for localizing thoracolumbar disc extrusions in dogs. Two veterinary surgeons and one veterinary neurologist who were unaware of surgical findings independently reviewed randomized sets of two-dimensional (2D) and MPR CT images from 111 dogs with confirmed thoracolumbar disc extrusions. For each set of images, readers recorded their localizations for extruded disc material and their diagnostic certainty. For MPR images, readers also recorded views they considered most helpful. Diagnostic accuracy estimates, mean diagnostic certainty scores and inter-observer agreement were compared using surgery as the gold standard. Frequencies were compared for MPR views rated most helpful. Diagnostic accuracy estimates were significantly greater for MPR vs. 2D CT images in one reader. Mean diagnostic certainty scores were significantly greater for MPR images in two readers. The change in agreement between 2D and MPR images differed from zero for all analyses (site, side, number affected) among all three readers. Multi-planar views rated most helpful with the highest frequency were oblique transverse and curved dorsal planar MPR views. Findings from this study indicate that multi-planar CT can improve surgeon diagnostic performance for localizing canine thoracolumbar disc extrusions.

Keyword

canine; computed tomography; intervertebral disc; surgeon diagnostic performance

MeSH Terms

Animals
Decision Making
Dog Diseases/*radiography
Dogs
Female
Humans
Image Processing, Computer-Assisted/*methods/standards
Intervertebral Disk Displacement/radiography/*veterinary
Male
Observer Variation
Tomography, X-Ray Computed

Figure

• 

  Fig. 1 Multi-planar reformatting (MPR) computed tomography (CT) image display demonstrating a bone window, oblique transverse image in a dog with surgically-confirmed calcified disc extrusion and spinal cord compression at T13-L1. The image is oriented so that the patient's right is on the viewer's left, and dorsal is at the top. The right upper reference frame displays a soft tissue transverse image. The right middle and lower frames display the angle of cut that was used to create the oblique transverse image. Extruded disc material is visible as a heterogenous mineral opacity mass involving the ventral vertebral canal and right lateral recess (large arrow). The dorsal longitudinal ligament appears as a linear lucency in the center of the mass. In the soft tissue window image, a curvilinear rim of increased opacity surrounds the right lateral margin of the thecal sac (small arrow). This appearance is consistent with epidural or sub-dural hemorrhage.

• 

  Fig. 2 MPR CT image display demonstrating a bone window, mid-sagittal image of the vertebral canal in the same dog. The image is oriented so that rostral is to the left, caudal is to the right, and dorsal is at the top. The right upper and lower reference frames display the line of cut that was used to generate the sagittal image. The right middle frame displays a soft tissue window, sagittal view. Extruded disc material is visible as a semi-circular mineral opacity in the ventral vertebral canal at T13-L1, with associated focal compression of the thecal sac (arrows).

• 

  Fig. 3 MPR CT image display demonstrating a bone window, curved dorsal planar view of the vertebral canal in the same dog (left frame). The image is oriented so that rostral is at the top, and the patient's right is on the viewer's left. The right upper reference frame displays the line of cut that was used to create the curved dorsal planar image. The right middle frame displays a soft tissue window, sagittal view of the vertebral canal. The right lower reference frame displays a dorsal planar view of the vertebral canal, without curvature correction. Extruded disc material is visible as a heterogenous mineral opacity in the ventral canal, right lateral recess and right intervertebral foramen; and extends from the level of cranial T13 to the level of mid L1 (arrow).

• 

  Fig. 4 Examples of criteria used to assign numerical values for CT and surgical localizations for extruded disc material. The text ventral to vertebrae indicates the names assigned to anatomic locations. The numbers dorsal to vertebrae indicate the numerical scores that were assigned for those locations.

• 

  Fig. 5 Mean diagnostic certainty scores for each reader and each CT image display format, using site localizations determined to be "correct". Certainty scores were based on a numerical scoring system from 1~10 with '10' representing the most confident score possible. By contrast, a score of '1' would indicate that the lesion had not been identified (*Significant difference at p < 0.05).

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