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DOI: 10.1148/radiol.2442060606
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(Radiology 2007;244:524-531.)
© RSNA, 2007

Musculoskeletal Imaging

Multidetector CT in Patients Suspected of Having Lumbar Disk Herniation: Comparison of Standard-Dose and Simulated Low-Dose Techniques1

Pascale Bohy, MD, Viviane de Maertelaer, PhD, Aymeric Roquigny, MD, Caroline Keyzer, MD, Denis Tack, MD, PhD, and Pierre Alain Gevenois, MD, PhD

1 From the Department of Radiology, Hôpital Erasme, Université Libre de Bruxelles, Route de Lennik 808, 1070 Brussels, Belgium (P.B., P.A.G.); Department of Radiology, Réseau Hospitalier de Médecine Sociale, Baudour, Belgium (A.R., D.T.); Department of Radiology, Centre Hospitalier Universitaire de Charleroi, Charleroi, Belgium (C.K.); and Statistical Unit, Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire, Université Libre de Bruxelles, Brussels, Belgium (V.d.M.). Received April 5, 2006; revision requested June 5; revision received July 4; accepted August 2; final version accepted December 7. Address correspondence to P.A.G. (e-mail: Pierre.alain.gevenois{at}ulb.ac.be).

Purpose: To compare standard-dose and simulated low-dose multidetector computed tomography (CT) in patients suspected of having lumbar disk herniation.

Materials and 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/m2), 300 (BMI ≥22 to <30 kg/m2), and 400 effective mAs (BMI ≥30 kg/m2). 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.

Conclusion: For patients suspected of having lumbar disk herniation, tube charge settings could be reduced to 65% of the standard dose adapted to the BMI.

© RSNA, 2007