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National Variation of Technical Factors in Computed Tomography of the Head

Thickman, David MD*; Wang, Guoqiao MA; White, Jaleh BA; Cutter, Gary PhD

Journal of Computer Assisted Tomography:
doi: 10.1097/RCT.0b013e31828ffe23

Objective: The objectives of this study were to describe head computed tomography (CT) technical factors used in the United States; assess guideline compliance and variability by sex, geographic region, institution, and manufacturer; and compare with NEXT (Nationwide Evaluation of X-ray Trends) survey.

Methods: Two thousand thirty-five head CT studies from 895 sites were analyzed. Peak kilovoltage, exposure, slice and image number, slice thickness, field of view, interslice gap, reformations, examination inclusiveness, use of contrast, and reconstruction filter were compared by sex, geographic region, institution type, and manufacturer.

Results: One hundred twenty to 140 kVp (peak kilovoltage) was used by 99.8% of the sites. There was no correlation between mAs and kVp. There was a 30-fold increase in number of images and nearly 9-fold increase in number of slices from least to most. Nearly 4% use slice thickness and interslice gap greater than guidelines. There were significant regional differences in field of view, image number, and slice thickness. Some variation related to manufacturers was found. Minor difference was also found between academic and nonacademic institutions. There were significant differences in kVp and mAs compared with NEXT.

Conclusions: Significant variations in head CT technique exist in the United States.

Author Information

From the *vRAD, Eden Prairie, MN; Department of Biostatistics, UAB School of Public Health, Birmingham AL; and Aspen, CO.

Received for publication December 14, 2012; accepted March 1, 2013.

Dr Thickman is now with Real Radiology, Denver, CO.

Reprints: David Thickman, MD, vRAD, 11995 Singletree Lane, Suite 500, Eden Prairie, MN 55344 (e-mail:

The authors have no conflict of interest to declare.

© 2013 by Lippincott Williams & Wilkins