title: Prevalence and significance of spinal disc abnormalities in an asymptomatic acceleration subject panel.
abstract: BACKGROUND
  A protocol to allow for human centrifuge exposures up to +12 Gz (12 times gravity) required a screening spinal MRI. MRI-derived spinal disc abnormalities were observed in three of the first four asymptomatic volunteer subjects. The protocol was interrupted and a second study was initiated to determine the possible cause and effect relationship between the disc findings and previous +Gz exposure.
  
  
  METHODS
  A T1 or T2 weighted sagittal MRI of the entire spine was accomplished on each of 22 asymptomatic male acceleration panel members, and a similar, age-matched control panel of 19 asymptomatic male subjects with no history of previous acceleration exposure. The MRIs from all 41 subjects were read at 2 diagnostic facilities by 9 radiologists. The evaluating radiologists were aware asymptomatic centrifuge subjects were being evaluated but were unaware a control group was included.
  
  
  RESULTS
  Initial results from any one reader revealed spinal disc abnormalities (bulging, degeneration or herniated nucleus pulposus-HNP) in 91% of the centrifuge panel and 79% of the control group, a non-significant difference. Within-reader and between-reader variability was very high. Comparison of 1st vs. 2nd reading of the same data by one radiologist demonstrated a 28% agreement and a 72% disagreement on observed abnormalities. Comparison of the same MRIs read by two different radiologists revealed a 23% agreement and a 77% disagreement, pointing out the ambiguity of the data and subjectiveness of the interpretation. Two additional neuroradiologists agreed to independently read all 41 MRIs after establishing unique reading criteria. There remained a non-significant difference between the two subject groups, whereas reader disagreement was still high (56%).
  
  
  CONCLUSIONS
  No significant difference was found between the two subject groups. The power of the test was low because of the small sample size. Our confidence in the interpretation is low because of the high degree of between-reader and within-reader variability.
authors.affiliation: Clinical Sciences Divisions, TX 78235-5104, USA.
authors.forename: J W
authors.initials: JW
authors.lastname: Burns
authors.forename: T H
authors.initials: TH
authors.lastname: Loecker
authors.forename: J R
authors.initials: JR
authors.lastname: Fischer
authors.forename: D H
authors.initials: DH
authors.lastname: Bauer
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D002498:Centrifugation / Q000009:adverse effects; D006801:Humans; D018471:Hypergravity / Q000009:adverse effects*; D007403:Intervertebral Disc / Q000473:pathology*; D007405:Intervertebral Disc Displacement / Q000175:diagnosis / Q000209:etiology*; D008279:Magnetic Resonance Imaging / Q000592:standards*; D008297:Male; D015588:Observer Variation; D015995:Prevalence; D015203:Reproducibility of Results; D016037:Single-Blind Method