title: Multidetector CT in patients suspected of having lumbar disk herniation: comparison of standard-dose and simulated low-dose techniques.
abstract: OBJECTIVE
  To compare standard-dose and simulated low-dose multidetector computed tomography (CT) in patients suspected of having lumbar disk herniation.
  
  
  METHODS
  The institutional review board approved the research protocol with a waiver of patient informed consent. Sixty consecutive patients underwent multidetector CT with four detector rows at 1 mm collimation at 140 kVp, with tube current-time product adapted to body mass index (BMI): 200 (BMI< 22 kg/m(2)), 300 (BMI > or =22 to <30 kg/m(2)), and 400 effective mAs (BMI > or =30 kg/m(2)). Simulated doses at 65%, 50%, 35%, and 20% of the dose were used for acquisition. During two separate sessions, three independent radiologists coded each of three caudal disks as normal, bulging, or herniated and graded canal and foramen compromise. Median numbers of discrepancies between the standard and reduced doses were compared with Friedman and Wilcoxon tests. Agreements within and between readers were evaluated through kappa statistics.
  
  
  RESULTS
  Dose reduction had no effect on a reader's ability to identify bulging disks (P = .128) and left and right foramen compromises (P = .413 and .665, respectively). However, for normal disks (P = .002), herniated disks (P = .004), and canal compromise (P = .002), dose reduction did have a significant effect. For normal disks and canal compromise, a reduction dose effect was not detected at 65% (P = .121 and .250, respectively) but appeared at 50% (P = .004 and .008, respectively). For herniation, a dose reduction effect was detected at 35% (P = .031). Agreements within and between readers ranged from poor to excellent and tended to decrease with dose reduction.
  
  
  CONCLUSIONS
  For patients suspected of having lumbar disk herniation, tube charge settings could be reduced to 65% of the standard dose adapted to the BMI.
authors.affiliation: Department of Radiology, Hôpital Erasme, Université Libre de Bruxelles, Route de Lennik 808, 1070 Brussels, Belgium.
authors.forename: Pascale
authors.initials: P
authors.lastname: Bohy
authors.forename: Viviane
authors.initials: V
authors.lastname: de Maertelaer
authors.forename: Aymeric
authors.initials: A
authors.lastname: Roquigny
authors.forename: Caroline
authors.initials: C
authors.lastname: Keyzer
authors.forename: Denis
authors.initials: D
authors.lastname: Tack
authors.forename: Pierre Alain
authors.initials: PA
authors.lastname: Gevenois
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007405:Intervertebral Disc Displacement / Q000000981:diagnostic imaging*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D009010:Monte Carlo Method; D011829:Radiation Dosage; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed / Q000379:methods*