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

King JB, Jones JC, Rossmeisl JH, Harper TA, Lanz OI, Werre SR - J. Vet. Sci. (2009)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical Sciences, School of Veterinary Medicine, University of California, Davis, California 95616, USA.

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.

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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).
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Figure 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).

Mentions: All 2D transverse CT images were acquired using the same single detector spiral CT scanner (Picker PQ5000; Universal Medical Systems, USA). Dogs were placed under general anesthesia and positioned in dorsal recumbency. The standard scanning protocol consisted of transverse slices from mid-T10 to mid-L3 [25]. Additional slices were obtained if requested by the primary care clinician or duty radiologist. Slice thickness settings ranged from 2~3 mm, with a 1 mm slice overlap. Two-dimensional CT image sets for each dog were converted into Digital Imaging and Communications in Medicine (DICOM) format and transferred via Ethernet to a Picture Archiving and Communication System (PACS) (RapidStudy; Eklin Medical Systems, USA). Immediately after scanning, studies were also transferred via Ethernet to a CT workstation (Voxel Q Visualization Station; Picker/Philips Medical Systems, USA). Multi-planar reformatted CT images for each dog were created by the on-duty radiologist, using the workstation's image analysis software. Oblique transverse MPR images were generated using the oblique MPR tool, with the slice angle oriented perpendicular to the long axis of the vertebral canal (Fig. 1). Oblique sagittal MPR images were generated using the same tool, with the slice angle oriented parallel to the long axis of the vertebral canal (Fig. 2). Curved dorsal MPR images were created using the curved MPR tool, with a hand-traced line of cut along the dorsal margins of vertebrae (Fig. 3). Each MPR image was saved as a screen capture and the set of saved images was transferred to the PACS via Ethernet. The MPR image set was stored in the PACS as a separate file for each dog, with the identifier "screen save" included in the file name.


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

King JB, Jones JC, Rossmeisl JH, Harper TA, Lanz OI, Werre SR - J. Vet. Sci. (2009)

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).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2801132&req=5

Figure 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).
Mentions: All 2D transverse CT images were acquired using the same single detector spiral CT scanner (Picker PQ5000; Universal Medical Systems, USA). Dogs were placed under general anesthesia and positioned in dorsal recumbency. The standard scanning protocol consisted of transverse slices from mid-T10 to mid-L3 [25]. Additional slices were obtained if requested by the primary care clinician or duty radiologist. Slice thickness settings ranged from 2~3 mm, with a 1 mm slice overlap. Two-dimensional CT image sets for each dog were converted into Digital Imaging and Communications in Medicine (DICOM) format and transferred via Ethernet to a Picture Archiving and Communication System (PACS) (RapidStudy; Eklin Medical Systems, USA). Immediately after scanning, studies were also transferred via Ethernet to a CT workstation (Voxel Q Visualization Station; Picker/Philips Medical Systems, USA). Multi-planar reformatted CT images for each dog were created by the on-duty radiologist, using the workstation's image analysis software. Oblique transverse MPR images were generated using the oblique MPR tool, with the slice angle oriented perpendicular to the long axis of the vertebral canal (Fig. 1). Oblique sagittal MPR images were generated using the same tool, with the slice angle oriented parallel to the long axis of the vertebral canal (Fig. 2). Curved dorsal MPR images were created using the curved MPR tool, with a hand-traced line of cut along the dorsal margins of vertebrae (Fig. 3). Each MPR image was saved as a screen capture and the set of saved images was transferred to the PACS via Ethernet. The MPR image set was stored in the PACS as a separate file for each dog, with the identifier "screen save" included in the file name.

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Clinical Sciences, School of Veterinary Medicine, University of California, Davis, California 95616, USA.

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.

Show MeSH
Related in: MedlinePlus