title: The time-adjusted gradual replacement injection method enables better visualization of the right heart.
abstract: BACKGROUND
  Despite the improvement of cardiac CT, right heart visualization remains challenging.
  
  
  OBJECTIVE
  We herein describe a new method, called the time-adjusted gradual replacement injection protocol. The aim of this study was to compare this protocol with the split-bolus injection protocol.
  
  
  METHODS
  Fifty-two patients who had undergone dual-source cardiac CT were retrospectively recruited. Twenty-six patients were injected by using the split-bolus injection protocol, and 26 patients were injected by using the time-adjusted gradual replacement injection protocol. For this method, we injected contrast medium for 10 seconds at a flow rate of 0.07 × body weight mL/s, then gradually replaced the contrast material with saline until 2 seconds before finishing the scans. The CT attenuation was measured in 4 chambers, the aorta, and the coronary arteries. The visualization of the anatomic structures and the occurrence and severity of streak artifacts were scored for the cardiac structures in the heart. For the analyses, either Welch t-test or Student t-test was performed.
  
  
  RESULTS
  In the right heart, the CT values and visualization scores were significantly higher in the time-adjusted replacement injection group than in the split-bolus injection group, whereas the artifact scores were comparable between the 2 groups. The CT values, visualization scores, and artifact scores of the left heart were not significantly different between the 2 groups.
  
  
  CONCLUSIONS
  In this study, the time-adjusted gradual replacement injection protocol provided excellent attenuation for visualization of the right heart. This method may help to accurately evaluate the right cardiac anatomy and thereby identify any potential diseases.
authors.affiliation: Department of Medicine and Biological Science, Gunma University Graduate School of Medicine, 3-39-22 Showa, Maebashi, Gunma, 371-8511, Japan. Electronic address: takehironakahara@gmail.com.
authors.forename: Takehiro
authors.initials: T
authors.lastname: Nakahara
authors.affiliation: Department of Diagnostic Radiology, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Jinzaki
authors.affiliation: Department of Medicine and Biological Science, Gunma University Graduate School of Medicine, 3-39-22 Showa, Maebashi, Gunma, 371-8511, Japan.
authors.forename: Nogiku
authors.initials: N
authors.lastname: Niwamae
authors.affiliation: Department of Medicine and Biological Science, Gunma University Graduate School of Medicine, 3-39-22 Showa, Maebashi, Gunma, 371-8511, Japan.
authors.forename: Yuuichirou
authors.initials: Y
authors.lastname: Saito
authors.affiliation: Department of Medicine and Biological Science, Gunma University Graduate School of Medicine, 3-39-22 Showa, Maebashi, Gunma, 371-8511, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Arai
authors.affiliation: Department of Diagnostic Radiology and Nuclear Medicine, Gunma University Graduate School of Medicine, Gunma, Japan.
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Tsushima
authors.affiliation: Department of Diagnostic Radiology, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Sachio
authors.initials: S
authors.lastname: Kuribayashi
authors.affiliation: Department of Medicine and Biological Science, Gunma University Graduate School of Medicine, 3-39-22 Showa, Maebashi, Gunma, 371-8511, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Kurabayashi
mesh_terms: D003287:Contrast Media / Q000008:administration & dosage*; D003331:Coronary Vessels / Q000000981:diagnostic imaging; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging*; D006325:Heart Atria / Q000000981:diagnostic imaging; D006331:Heart Diseases / Q000000981:diagnostic imaging*; D006352:Heart Ventricles / Q000000981:diagnostic imaging; D006801:Humans; D007267:Injections; D008297:Male; D061330:Multidetector Computed Tomography / Q000379:methods*; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012965:Sodium Chloride / Q000008:administration & dosage; D013997:Time Factors
chemical_list: D003287:Contrast Media; D012965:Sodium Chloride
keywords: Cardiac CT; Homogeneous enhancement; Injection method; Right heart; Visualization of cardiac structure in detail