Objective: To evaluate a method for obtaining half-dose CT images for observer studies evaluating lower-dose CT.
Methods: Phantoms of varying sizes were scanned at multiple tube potentials using dose-matched dual-source (DS) and single-source (SS) protocols. Images from single-tube reconstruction of DS data were compared with SS images acquired at half-original CTDIvol. Thirty patients underwent supine SS and dose-matched prone DS CT colonography (CTC). Half-dose prone images were reconstructed with sinogram-affirmed iterative reconstruction (SAFIRE). Two radiologists scored image quality on 2-dimensional (2D) and 3D images.
Results: Image noise was similar between half-dose SS images and DS images reconstructed from one tube only with tube potential of 120 kV or more for phantoms 40 cm or smaller (P < 0.05). For both readers, the patients’ CTC image quality scores were more than 84% concordant between SS or DS CTC images, and half-dose–prone CTC images with SAFIRE had 84% or more concordance with routine-dose CTC except for 3D image noise.
Conclusions: In appropriately sized patients, DS acquisition with single-tube reconstruction can create half-dose images, permitting comparison to full-dose images. For CTC, there is comparable image quality for colonic evaluation between full-dose and half-dose images reconstructed with SAFIRE.
From the *Department of Radiology, Mayo Clinic, Rochester, MN; †Department of Radiology, Stanford University Stanford, CA; and ‡Siemens Healthcare, Forchheim, Germany.
Received for publication February 2, 2012; accepted June 5, 2012.
Reprints: Joel G. Fletcher, MD, 200 First St SW, Rochester, MN 55905 (e-mail: firstname.lastname@example.org).
The CT scanner used in this project was provided to Mayo Clinic from Siemens Healthcare through a grant to the Mayo CT Clinical Innovation Center, as is the noise reduction product under evaluation (SAFIRE, Sinogram-affirmed Iterative Reconstruction). Drs. Katie Grant, Bernhard Schmidt, and Thomas Allmendinger are Siemens employees. All image quality analyses were performed and analyzed by Mayo investigators.
The authors report no conflicts of interest.