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The Effect of the Virtual Monochromatic Spectral Imaging for the Metallic Artifact and the Pulmonary Nodule Detection

Gyobu, Tomoko MD; Honda, Osamu MD, PhD; Kawata, Yutaka MD; Kikuyama, Ayano MD; Miki, Hiromu RT; Yanagawa, Masahiro MD, PhD; Sumikawa, Hiromitsu MD, PhD; Koyama, Mitsuhiro MD, PhD; Tomiyama, Noriyuki MD, PhD

Journal of Computer Assisted Tomography: September/October 2013 - Volume 37 - Issue 5 - p 707–711
doi: 10.1097/RCT.0b013e31829e0164
Thoracic and Cardiovascular Imaging

Objectives This study aimed to evaluate whether dual-energy computed tomography can reduce metal artifacts and improve detection of pulmonary nodules.

Methods Twelve simulated nodules were randomly placed inside a chest phantom with a pacemaker. Then, dual-energy computed tomography was performed, and 5 virtual monochromatic images at 40, 50, 65, 100, and 140 keV were reconstructed with 5- and 0.625-mm slice thicknesses. Two independent observers assessed the metal artifact (3-point scale from 1, none, to 3, severe) and detection of the nodule (5-point scale from 1, definitely absent, to 5, definitely present). Statistical analysis was performed with a P value of less than 0.01 (0.05/5).

Results With both slice thicknesses, the metallic artifact increased at 40 or 50 keV and decreased at 100 or 140 keV relative to that at 65 keV (P < 0.01). The nodule detection score was not significantly different between each kiloelectron volt level with the 0.625-mm slice thickness; however, the score was significantly worse at 40 keV compared to 65 keV (P < 0.01) with the 5-mm slice thickness.

Conclusions High monochromatic energy images can reduce metal artifacts without a change in nodule detection score. Low monochromatic energy images increase metal artifacts and worsen nodule detection in thick slices.

From the *Department of Radiology, Osaka University Graduate School of Medicine, Suita; †Department of Radiology, Osaka Rosai Hospital, Kita-ku, Sakai; ‡Department of Radiology, Osaka Furitsu Kyuseiki Sogo Iryo Center, Sumiyoshi-ku; §Department of Radiology, Osaka University Hospital, Suita; and ∥Department of Radiology, Osaka Medical College, Takatsuki, Osaka, Japan.

Received for publication March 18, 2013; accepted May 28, 2013.

Reprints: Tomoko Gyobu, MD, Department of Radiology, Osaka University Graduate School of Medicine, 2-2Yamadaoka, Suita, Osaka 565-0871, Japan (e-mail:

Conflicts of interest and source of funding: There is no conflict of interest.

Copyright © 2013 Wolters Kluwer Health, Inc. All rights reserved.