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A Comparative Study Between High-Definition Volumetric Imaging Computed Tomography and Multi-Slice Computed Tomography in the De Journal of the South African Veterinary Association ISSN: (Online) 2224-9435, (Print) 1019-9128 Page 1 of 7 Original Research A comparative study between high-definition volumetric imaging computed tomography and multi-slice computed tomography in the detection of acute thoraco-lumbar disc extrusions in dogs Authors: Computed tomography (CT) is commonly used to image intervertebral disc extrusion 1,2 Ross C. Elliott (IVDE) in dogs. The current gold standard for CT imaging is the use of multi-slice CT Chad F. Berman1,2 Remo G. Lobetti2 (MS CT) units. Smaller high-definition volumetric imaging (HDVI) mobile CT has been marketed for veterinary practice. This unit is described as an advanced flat panel. The Affiliations: goal of this manuscript was to evaluate the ability of the HDVI CT in detecting IVDE 1Department of Companion Animal and Clinical Studies, without the need for CT myelography, compared with the detection of acute disc Onderstepoort, South Africa extrusions with a MS CT without the need for MS CT myelogram. Retrospective blinded analyses of 219 dogs presented for thoraco-lumbar IVDE that had a HDVI CT (n = 123) or 2 Bryanston Veterinary MS CT (n = 96) were performed at a single referral hospital. A total of 123 cases had HDVI Hospital, Johannesburg, South Africa CT scans with surgically confirmed IVDE. The IVDE was identified in 88/123 (72%) dogs on pre-contrast HDVI CT. The remaining 35/128 (28%) cases required a HDVI CT myelogram Corresponding author: to identify the IVDE. Ninety-six cases had MS CT scans with surgically confirmed IVDE. Ross Elliott, The IVDE was identified in 78/96 (81%) dogs on the pre-contrast MS CT. The remaining [email protected] 18/96 (19%) cases had a MS CT myelogram to identify the IVDE. Multi-slice CT Dates: detected IVDE significantly more than HDVI CT (p = 0.032). This study showed that the Received: 14 Aug. 2019 ability of HDVI CT for detecting IVDE is lower than that of MS CT. The HDVI CT Accepted: 15 Jan. 2021 Published: 11 Mar. 2021 system may be useful in smaller referral practices, with a lower case load where space is limited. How to cite this article: Elliott, R.C., Berman, C.F. & Keywords: computed tomography; volumetric imaging; intervertebral disc disease; disc Lobetti, R.G., 2021, ‘A extrusion; multi-slice computed tomography. comparative study between high-definition volumetric imaging computed tomography and multi-slice Introduction computed tomography in the detection of acute thoraco- Thoraco-lumbar intervertebral disc disease is a common condition in the small animal patient lumbar disc extrusions in (Griffin, Levine & Kerwin 2009). Decompressive surgery is the treatment of choice in treating dogs’, Journal of the South thoraco-lumbar intervertebral disc disease in small animals. A hemilaminectomy is considered African Veterinary the technique of choice to decompress the spinal cord (Aikawa et al. 2012; McKee 1992; Langerhuus Association 92(0), a2010. https://doi.org/10.4102/ & Miles 2017). jsava.v92i0.2010 Advanced imaging studies such as myelography, computed tomography (CT) or magnetic Copyright: resonance imaging (MRI) are essential to correctly identify the site of disc extrusion (Cooper © 2021. The Authors. Licensee: AOSIS. This work et al. 2014; Noyes et al. 2017; Robertson & Thrall 2011; Schroeder et al. 2011). Myelography is the is licensed under the most basic and most invasive imaging technique with the highest complication rate (Barone Creative Commons et al. 2002; Da Costa, Parent & Dobson 2011; Hecht et al. 2009; King et al. 2009). Magnetic Attribution License. resonance imaging has the highest rate of identification of thoraco-lumbar disc extrusion in dogs of around 98% (Cooper et al. 2014; Noyes et al. 2017; Robertson & Thrall 2011), but is relatively more expensive and time-consuming (25–145 min per examination) to acquire than both CT and myelography (4–45 min per examination) (Cooper et al. 2014; Hecht et al. 2009; Robertson & Thrall 2011). Read online: Scan this QR Computed tomography is a rapid imaging modality that allows accurate detection of code with your smart phone or mineralised disc extrusions in dogs. Certain breeds have been shown to have a higher mobile device incidence of detection of intervertebral disc extrusions such as the dachshund (Hecht et al. to read online. 2009; King et al. 2009; Kranenburg et al. 2013; Newcomb et al. 2012; Schroeder et al. 2011). http://www.jsava.co.za Open Access Page 2 of 7 Original Research Detection rates of an acute disc extrusion using multi-slice identification of acute disc extrusion in pre-contrast HDVI CT (MS) CT are reported to be 88%, with markedly shorter would be significantly lower in detection of intervertebral disc scan times when compared with MRI (Cooper et al. 2014). extrusion in the dog when compared with MS CT. A negative pre-contrast MS CT requires an additional MS CT myelogram or ideally an MRI, if there is a strong Materials and methods suspicion of a disc extrusion. A CT myelogram has similar complications to a radiographic myelogram (Hecht et al. Inclusion criteria 2009; Newcomb et al. 2012; Robertson & Thrall 2011). The records of Bryanston Veterinary Hospital were searched from 01 June 2017 to 01 June 2018 and from 01 November Recently a high-definition volumetric imaging (HDVI) CT 2019 to 01 August 2020 for all files containing CT, disc system was marketed for use in small animal veterinary extrusion, hemilaminectomy and spinal surgery. These practice; it was introduced to the South African veterinary records were re-examined to only include canine patients industry in 2015 (Vimago, www.epicaanimalhealth.com). The with a myelopathy affecting spinal cord segment T3-S1. To be unit is marketed as a mobile, smaller unit (230 centimetres included in the study, the dog had to have had a HDVI CT or [cm] × 150 cm footprint), lower operating costs, plug in and a MS CT scan and an acute intervertebral disc extrusion with use to a single phase 220 volts (V) connection and lighter the surgical site and side of the dog confirmed after (600 kilograms [kg]) when compared with conventional MS decompressive hemilaminectomy. CT units. The cost of the HDVI CT unit is similar to a conventional 16 slice CT unit, however, the set up, installation All dogs that had visible mineralised opacity in the vertebral costs and infrastructure requirements are much less. The room canal or extradural compression on myelography consistent housing the HDVI CT unit still requires radiation safety with an acute intervertebral disc extrusion were selected protocols as for MS CT. for the study. Exclusion criteria were: MRI scan as the initial imaging modality; other spinal cord pathology High-definition volumetric imaging is a modification of an (mass, fibrocartilaginous embolism, meningomyelitis, non- older cone beam CT (CBCT) technology. High definition compressive disc extrusion); no visible mineralised disc imaging is defined as using advanced flat panel CT material on the pre contrast HDVI CT\MS CT and no technology. It entails a cone shaped source of ionising extradural compression on the HDVI CT/MS CT radiation directed through the middle of the area of interest myelogram; a chronic disc protrusion and presence of more to an x-ray detector both of which are in a fixed position in than one disc extrusion at the time of presentation. the gantry (Scarfe & Farman 2008). During the rotation of the machine within the gantry, multiple (approximately 150 to Examinations more than 600) sequential planar projection images of the field of view are acquired in a complete, or partial, arc. High- All dogs had a complete physical and neurological definition volumetric imaging CT exposure incorporates the examination performed at the time of presentation. This entire field of view, and only one rotational sequence of the isolated the pathology to the spinal segment T3-S1. A gantry is necessary to acquire enough data for reconstruction modified Frankel score was assigned to each patient to (Scarfe & Farman 2008). These fields of view or stacks are allow prognostication for the owner prior to proceeding available in two selectable options prior to scanning, with surgery (Levine et al. 2009). Patients older than 8 years a standard (265 millimetres [mm] × 215 mm) and a large of age had a full serum biochemistry and haematology (302 mm × 249 mm). performed. All patients in this study were determined to be clinically normal apart from the thoraco-lumbar disc The spatial resolution is suggested to be equivalent to MS disease. (4–16 slice) CT because of the decreased size of the voxels utilised. However, the speed of acquisition is markedly High-definition volumetric imaging computed slower. Spatial resolution could be lost because of motion blur tomography/multi-slice computed tomography and negate the potential advantages (Scarfe & Farman 2008). technique Dogs were premedicated with diazepam (valium The capabilities of HDVI CT are unknown in small animal 0.2 milligrams [mg]/kg IV, Roche, South Africa) and veterinary practice. However, the imaging ability of the morphine (morphine sulphate 0.5 mg/kg IV, Pharma-Q, HDVI CT unit needs to be determined as the cost of the unit South Africa). Induction was performed with propofol itself is similar to a MS CT unit. (Diprivan 1% 6.6 mg/kg IV, AstraZeneca Pharmaceuticals, South Africa). Dogs were then intubated and maintained on The aim of the study was to compare the ability of HDVI isoflurane (Isofor, Safeline Pharmaceuticals, South Africa). CT and MS CT imaging to detect acute thoraco-lumbar The dogs were placed in dorsal recumbency to allow as little intervertebral disc extrusion in dogs. The ability of both HDVI movement from breathing as possible to affect the quality of CT and MS CT was determined by confirmation of the the spinal imaging.
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