title: Comparison of iterative model, hybrid iterative, and filtered back projection reconstruction techniques in low-dose brain CT: impact of thin-slice imaging.
abstract: BACKGROUND
  The purpose of this study was to evaluate the utility of iterative model reconstruction (IMR) in brain CT especially with thin-slice images.
  
  
  METHODS
  This prospective study received institutional review board approval, and prior informed consent to participate was obtained from all patients. We enrolled 34 patients who underwent brain CT and reconstructed axial images with filtered back projection (FBP), hybrid iterative reconstruction (HIR) and IMR with 1 and 5 mm slice thicknesses. The CT number, image noise, contrast, and contrast noise ratio (CNR) between the thalamus and internal capsule, and the rate of increase of image noise in 1 and 5 mm thickness images between the reconstruction methods, were assessed. Two independent radiologists assessed image contrast, image noise, image sharpness, and overall image quality on a 4-point scale.
  
  
  RESULTS
  The CNRs in 1 and 5 mm slice thickness were significantly higher with IMR (1.2 ± 0.6 and 2.2 ± 0.8, respectively) than with FBP (0.4 ± 0.3 and 1.0 ± 0.4, respectively) and HIR (0.5 ± 0.3 and 1.2 ± 0.4, respectively) (p < 0.01). The mean rate of increasing noise from 5 to 1 mm thickness images was significantly lower with IMR (1.7 ± 0.3) than with FBP (2.3 ± 0.3) and HIR (2.3 ± 0.4) (p < 0.01). There were no significant differences in qualitative analysis of unfamiliar image texture between the reconstruction techniques.
  
  
  CONCLUSIONS
  IMR offers significant noise reduction and higher contrast and CNR in brain CT, especially for thin-slice images, when compared to FBP and HIR.
authors.affiliation: Diagnostic Radiology, Amakusa Medical Center, Kameba 854-1, Amakusa, Kumamoto, 863-0046, Japan. kff00712@nifty.com.|Department of Diagnostic Radiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan. kff00712@nifty.com.
authors.forename: Takeshi
authors.identifier: http://orcid.org/0000-0002-9010-0341
authors.initials: T
authors.lastname: Nakaura
authors.affiliation: Diagnostic Radiology, Amakusa Medical Center, Kameba 854-1, Amakusa, Kumamoto, 863-0046, Japan.|Department of Diagnostic Radiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Iyama
authors.affiliation: Diagnostic Radiology, Amakusa Medical Center, Kameba 854-1, Amakusa, Kumamoto, 863-0046, Japan.|Department of Diagnostic Radiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan.
authors.forename: Masafumi
authors.initials: M
authors.lastname: Kidoh
authors.affiliation: Diagnostic Radiology, Amakusa Medical Center, Kameba 854-1, Amakusa, Kumamoto, 863-0046, Japan.|Department of Diagnostic Radiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Yokoyama
authors.affiliation: Department of Diagnostic Radiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan.
authors.forename: Seitaro
authors.initials: S
authors.lastname: Oda
authors.affiliation: Philips Electronics, Kumamoto, Japan.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Tokuyasu
authors.affiliation: Department of Surgery, Amakusa Medical Center, Kumamoto, Japan.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Harada
authors.affiliation: Department of Diagnostic Radiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Yamashita
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001921:Brain / Q000000981:diagnostic imaging*; D001927:Brain Diseases / Q000000981:diagnostic imaging*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D015588:Observer Variation; D011829:Radiation Dosage; D000069079:Radiation Exposure / Q000032:analysis / Q000517:prevention & control*; D011835:Radiation Protection / Q000379:methods*; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D059629:Signal-To-Noise Ratio; D013382:Subtraction Technique; D014057:Tomography, X-Ray Computed / Q000379:methods*; D055815:Young Adult
keywords: Brain; CT; Iterative reconstruction; Radiation dose