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Individualized kV Selection and Tube Current Reduction in Excretory Phase Computed Tomography Urography: Potential for Radiation Dose Reduction and the Contribution of Iterative Reconstruction to Image Quality

Froemming, Adam T. MD*; Kawashima, Akira MD, PhD*; Takahashi, Naoki MD*; Hartman, Robert P. MD*; Nathan, Mark A. MD*; Carter, Rickey E. PhD; Yu, Lifeng PhD; Leng, Shuai PhD; Kagoshima, Hiroki*; McCollough, Cynthia H. PhD*; Fletcher, Joel G. MD*

Journal of Computer Assisted Tomography: July/August 2013 - Volume 37 - Issue 4 - p 551–559
doi: 10.1097/RCT.0b013e31828f871f
Abdominal Imaging

Objective: The objective of this study was to analyze radiation dose reduction and image quality by combining automated kV selection, tube current reduction, and iterative reconstruction.

Methods: This was a retrospective analysis of the excretory phase of 55 patients with 2 computed tomography urography examinations: automated kV selection with tube current reduction (“low-dose protocol”: with filtered back projection vs iterative reconstruction) and routine dose examinations. Image quality was analyzed blindly and in side-by-side analyses, in addition to quantitative measurements.

Results: Low-dose protocol median dose change was −40% (−10.7 to +12.9 mGy); 100 kV was autoselected in 44 (80%) of 55 patients (body mass index range, 19–36 kg/m2) with mean dose reduction of 42.5%. Whereas up to 19% of low-dose images with filtered back projection were inferior by blinded review (P < 0.001), low-dose iterative reconstruction images were not rated inferior (P = 1.0).

Conclusions: The combination of iterative reconstruction, automated kV selection, and tube current reduction results in radiation dose reduction with preserved image quality and diagnostic confidence.

From the Department of Radiology, and †Division of Biomedical Statistics and Informatics, Department of Health Sciences Research, Mayo Clinic, Rochester, MN.

Received for publication January 7, 2013; accepted February 26, 2013.

Reprints: Adam T. Froemming, MD, 200 First St SW, Rochester, MN 55905 (e-mail:

Drs Fletcher and McCollough receive grant support from Siemens Healthcare, Forchheim, Germany. The Siemens Definition FLASH CT scanner used in this study was provided to Mayo Clinic through this grant support. The Mayo Clinic and Drs McCollough and Fletcher have intellectual property rights related to the kV selection technology used in the research. These authors did not participate in image quality evaluation or collection or statistical analysis of dose reduction data. This research has been reviewed by the Mayo Clinic Conflict of Interest Review Board and is being conducted in compliance with Mayo Clinic Conflict of Interest policies. For the remaining authors, there are no potential conflicts of interest.

© 2013 by Lippincott Williams & Wilkins