title: Low-Contrast and Low-Radiation Dose Protocol in Cardiac Computed Tomography: Usefulness of Low Tube Voltage and Knowledge-Based Iterative Model Reconstruction Algorithm.
abstract: OBJECTIVE
  This study aimed to evaluate the feasibility of a low contrast, low-radiation dose protocol of 80-peak kilovoltage (kVp) with prospective electrocardiography-gated cardiac computed tomography (CT) using knowledge-based iterative model reconstruction (IMR).
  
  
  METHODS
  Thirty patients underwent an 80-kVp prospective electrocardiography-gated cardiac CT with low-contrast agent (222-mg iodine per kilogram of body weight) dose. We also enrolled 30 consecutive patients who were scanned with a 120-kVp cardiac CT with filtered back projection using the standard contrast agent dose (370-mg iodine per kilogram of body weight) as a historical control group. We evaluated the radiation dose for the 2 groups. The 80-kVp images were reconstructed with filtered back projection (protocol A), hybrid iterative reconstruction (HIR, protocol B), and IMR (protocol C). We compared CT numbers, image noise, and contrast-to-noise ratio among 120-kVp protocol, protocol A, protocol B, and protocol C. In addition, we compared the noise reduction rate between HIR and IMR. Two independent readers compared image contrast, image noise, image sharpness, unfamiliar image texture, and overall image quality among the 4 protocols.
  
  
  RESULTS
  The estimated effective dose (ED) of the 80-kVp protocol was 74% lower than that of the 120-kVp protocol (1.4 vs 5.4 mSv). The contrast-to-noise ratio of protocol C was significantly higher than that of protocol A. The noise reduction rate of IMR was significantly higher than that of HIR (P < 0.01). There was no significant difference in almost all qualitative image quality between 120-kVp protocol and protocol C except for image contrast.
  
  
  CONCLUSIONS
  A 80-kVp protocol with IMR yields higher image quality with 74% decreased radiation dose and 40% decreased contrast agent dose as compared with a 120-kVp protocol, while decreasing more image noise compared with the 80-kVp protocol with HIR.
authors.affiliation: From the *Diagnostic Radiology, Amakusa Medical Center, Amakusa; †Department of Diagnostic Radiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto; ‡Department of Surgery, Amakusa Medical Center, Amakusa, Kumamoto, Japan; and §Philips Healthcare Asia Pacific, Tokyo, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Iyama
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nakaura
authors.forename: Koichi
authors.initials: K
authors.lastname: Yokoyama
authors.forename: Masafumi
authors.initials: M
authors.lastname: Kidoh
authors.forename: Kazunori
authors.initials: K
authors.lastname: Harada
authors.forename: Seitaro
authors.initials: S
authors.lastname: Oda
authors.forename: Shinichi
authors.initials: S
authors.lastname: Tokuyasu
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Yamashita
mesh_terms: D000368:Aged; D055424:Cardiac-Gated Imaging Techniques / Q000379:methods; D003287:Contrast Media / Q000008:administration & dosage*; D017023:Coronary Angiography / Q000379:methods*; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging*; D004305:Dose-Response Relationship, Drug; D004781:Environmental Exposure / Q000032:analysis / Q000517:prevention & control*; D005260:Female; D006801:Humans; D051188:Knowledge Bases; D000069550:Machine Learning; D008297:Male; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media