title: Optimizing CT technique to reduce radiation dose: effect of changes in kVp, iterative reconstruction, and noise index on dose and noise in a human cadaver.
abstract: For assessment of the effect of varying the peak kilovoltage (kVp), the adaptive statistical iterative reconstruction technique (ASiR), and automatic dose modulation on radiation dose and image noise in a human cadaver, a cadaver torso underwent CT scanning at 80, 100, 120 and 140 kVp, each at ASiR settings of 0, 30 and 50 %, and noise indices (NIs) of 5.5, 11 and 22. The volume CT dose index (CTDIvol), image noise, and attenuation values of liver and fat were analyzed for 20 data sets. Size-specific dose estimates (SSDEs) and liver-to-fat contrast-to-noise ratios (CNRs) were calculated. Values for different combinations of kVp, ASiR, and NI were compared. The CTDIvolvaried by a power of 2 with kVp values between 80 and 140 without ASiR. Increasing ASiR levels allowed a larger decrease in CTDIvoland SSDE at higher kVp than at lower kVp while image noise was held constant. In addition, CTDIvoland SSDE decreased with increasing NI at each kVp, but the decrease was greater at higher kVp than at lower kVp. Image noise increased with decreasing kVp despite a fixed NI; however, this noise could be offset with the use of ASiR. The CT number of the liver remained unchanged whereas that of fat decreased as the kVp decreased. Image noise and dose vary in a complicated manner when the kVp, ASiR, and NI are varied in a human cadaver. Optimization of CT protocols will require balancing of the effects of each of these parameters to maximize image quality while minimizing dose.
authors.affiliation: Department of Diagnostic Imaging, Rhode Island Hospital, The Warren Alpert Medical School of Brown University, 593 Eddy St., Providence, RI, 02903, USA. kchang@lifespan.org.
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Chang
authors.affiliation: Department of Diagnostic Imaging, Rhode Island Hospital, The Warren Alpert Medical School of Brown University, 593 Eddy St., Providence, RI, 02903, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: Collins
authors.affiliation: Department of Radiology, Boston Medical Center, 80 E. Concord St., Boston, MA, 02118, USA.
authors.forename: Baojun
authors.initials: B
authors.lastname: Li
authors.affiliation: Department of Radiology, Brigham and Women's Hospital, 1620 Tremont Street, One Brigham Circle BC-3-010C.11, Boston, MA, 02120, USA.
authors.forename: William W
authors.initials: WW
authors.lastname: Mayo-Smith
mesh_terms: D002102:Cadaver; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D011829:Radiation Dosage; D059629:Signal-To-Noise Ratio; D014057:Tomography, X-Ray Computed / Q000379:methods*; D060726:Torso / Q000000981:diagnostic imaging
keywords: Automatic dose modulation; CT radiation dose reduction; Iterative reconstruction; Reduced kVp