title: Effects of body position, imaging plane, and observer on computed tomographic measurements of the lumbosacral intervertebral foraminal area in dogs.
abstract: OBJECTIVE
  To evaluate effects of imaging plane, flexion and extension, patient weight, and observer on computed tomographic (CT) image measurements of the area of the lumbosacral (L7-S1) intervertebral foramen (LSIF) in dogs.
  
  
  METHODS
  12 dog cadavers (2 were excluded because of foraminal stenosis).
  
  
  METHODS
  In each cadaver, sagittal, sagittal oblique, transverse oblique, and double oblique CT images were obtained at 3 zones (entrance, middle, and exit zones) of the region of the lateral lumbar spinal canal that comprises the LSIF while the lumbosacral junction (LSJ) was positioned in flexion or extension. Barium-impregnated polymethylmethacrylate was used to fill the intervertebral foramina to aid boundary detection. Measurements of interest were obtained.
  
  
  RESULTS
  Among the dog cadavers, there was large variability in LSIF cross-sectional areas (range, 0.12 to 0.44 cm2; SD, 0.1 cm2) and in foraminal angles required to obtain a double oblique plane in LSJ extension (SD, 8 ° to 9 °). For LSIF area measurements in standard sagittal CT images, interobserver variability was 23% to 44% and intraobserver variability was 4% to 5%. Sagittal oblique images obtained during LSJ extension yielded smaller mean LSIF areas (0.30 cm2), compared with findings in sagittal images (0.37 to 0.52 cm2). The exit and middle zone areas were smaller than the entrance zone area in sagittal images obtained during LSJ extension.
  
  
  CONCLUSIONS
  Repeated measurements of the LSIF area in images obtained during LSJ extension may be unreliable as a result of interobserver variability and the effects of dog positioning and CT slice orientation.
authors: Department of Musculoskeletal Biology, Leahurst Campus, University of Liverpool, Neston, Wirral, Cheshire, CH64 7TE, England.
authors: Brent M
authors: BM
authors: Higgins
authors: Peter J
authors: PJ
authors: Cripps
authors: Martin
authors: M
authors: Baker
authors: Lee
authors: L
authors: Moore
authors: Fay E
authors: FE
authors: Penrose
authors: James F
authors: JF
authors: McConnell
mesh_terms: D000818:Animals; D001464:Barium / Q000737:chemistry; D002102:Cadaver; D004285:Dogs / Q000033:anatomy & histology*; D005260:Female; D007091:Image Processing, Computer-Assisted; D007403:Intervertebral Disc / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D008159:Lumbar Vertebrae / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D008297:Male; D015588:Observer Variation; D010375:Pedigree; D019904:Polymethyl Methacrylate / Q000737:chemistry; D011187:Posture; D012016:Reference Values; D015203:Reproducibility of Results; D012447:Sacrum / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D013115:Spinal Canal / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods* / Q000662:veterinary
chemical_list: D001464:Barium; D019904:Polymethyl Methacrylate