title: CT outperforms radiographs at a comparable radiation dose in the assessment for spondylolysis.
abstract: BACKGROUND
  Lumbar spondylolysis, a unilateral or bilateral fracture at pars interarticularis, is a common cause of low back pain in children. The initial imaging study in the diagnosis of lumbar spondylolysis has historically been lumbar spine radiographs; however, radiographs can be equivocal or false-negative. Definitive diagnosis can be achieved with computed tomography (CT), but its use has been limited due to the dose of ionizing radiation to the patient.
  
  
  OBJECTIVE
  By limiting the z-axis coverage to the relevant anatomy and optimizing the CT protocol, we are able to provide a definitive diagnosis of fractures of the pars interarticularis at comparable or lower radiation dose than commonly performed lumbar spine radiographs. As there is no gold standard for the diagnosis of spondylolysis besides surgery, we compared interobserver agreement and degree of confidence to determine which modality is preferable.
  
  
  METHODS
  Sixty-two patients with low back pain ages 5-18 years were assessed for the presence of spondylolyis. Forty-seven patients were evaluated by radiography and 15 patients were evaluated by limited field-of-view CT. Both radiographic and CT examinations were assessed anonymously in random order for the presence or absence of spondylolyisis by six raters. Agreement was assessed among raters using a Fleiss Kappa statistic for multiple raters.
  
  
  RESULTS
  CT provided a significantly higher level of agreement among raters than radiographs (P < 0.001). The overall Kappa for rater agreement with radiographs was 0.24, 0.34 and 0.40 for 2, 3 or 4 views, respectively, and 0.88 with CT.
  
  
  CONCLUSIONS
  Interobserver agreement is significantly greater using limited z-axis coverage CT when compared with radiographs. Radiologist confidence improved significantly with CT compared to radiographs regardless of the number of views.
authors.affiliation: Department of Radiology, Children's Hospital Colorado, 13123 East 16th Ave., Aurora, CO, 80045, USA, Michael.fadell@childrenscolorado.org.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Fadell
authors.forename: Jane
authors.initials: J
authors.lastname: Gralla
authors.forename: Istiaq
authors.initials: I
authors.lastname: Bercha
authors.forename: Jaime R
authors.initials: JR
authors.lastname: Stewart
authors.forename: Roger K
authors.initials: RK
authors.lastname: Harned
authors.forename: James D
authors.initials: JD
authors.lastname: Ingram
authors.forename: Angie L
authors.initials: AL
authors.lastname: Miller
authors.forename: John D
authors.initials: JD
authors.lastname: Strain
authors.forename: Jason P
authors.initials: JP
authors.lastname: Weinman
mesh_terms: D000293:Adolescent; D002648:Child; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging; D008161:Lumbosacral Region / Q000000981:diagnostic imaging; D008297:Male; D011829:Radiation Dosage; D015203:Reproducibility of Results; D013169:Spondylolysis / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed