title: Impact of a reduced tube voltage on CT angiography and radiation dose: results of the PROTECTION I study.
abstract: OBJECTIVE
  The aim of this study was to determine the impact of a reduced 100-kV tube voltage on image quality and radiation exposure in a pre-defined subgroup analysis of the international, multicenter radiation dose survey PROTECTION I (Prospective Multicenter Study on RadiaTion Dose Estimates Of Cardiac CT AngIOgraphy I) study.
  
  
  BACKGROUND
  Cardiac computed tomography angiography (CCTA) has become a frequently used diagnostic tool in clinical practice. Despite continually improving CT technology, there remain concerns regarding the associated radiation exposure. A reduced tube voltage of 100 kV has been proposed as an effective means for dose reduction in nonobese patients.
  
  
  METHODS
  The study assessed the relevant radiation dose parameters as well as quantitative and qualitative diagnostic image quality data in a subgroup of 321 patients (100 kV: 82 patients; 120 kV: 239 patients), who were scanned at study sites that applied a 100-kV tube voltage in at least 1 patient. Diagnostic image quality was assessed by an experienced CCTA investigator with a 4-point score (1: nondiagnostic to 4: excellent image quality). Effective radiation dose was estimated from the dose-length-product of each CCTA study.
  
  
  RESULTS
  The use of the 100-kV scan protocol was associated with 53% reduction in CCTA median radiation dose estimates, when compared with the conventional 120-kV scan protocol (p < 0.001). Although image noise significantly increased by 26.3% with 100 kV, signal- as well as contrast-to-noise ratios also increased by 7.9% (p = 0.254) and 10.8% (p = 0.027), respectively. Reduction of tube voltage did not impair diagnostic image quality (median diagnostic score: 3.5 [3.25 to 3.75] vs. 3.5 [3.0 to 3.75] for 100 kV vs. 120 kV; p = 0.22).
  
  
  CONCLUSIONS
  In this nonrandomized PROTECTION I dose survey, reducing the CCTA tube voltage to 100 kV in nonobese patients is associated with a significant reduction in radiation exposure while maintaining diagnostic image quality. Thus, the 100-kV scan technique should be considered for CCTA dose reduction in adequately selected patients.
authors.affiliation: Klinik für Herz- und Kreislauferkrankungen, Deutsches Herzzentrum München, Klinik an der TU München, Munich, Germany.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Bischoff
authors.forename: Franziska
authors.initials: F
authors.lastname: Hein
authors.forename: Tanja
authors.initials: T
authors.lastname: Meyer
authors.forename: Martin
authors.initials: M
authors.lastname: Hadamitzky
authors.forename: Stefan
authors.initials: S
authors.lastname: Martinoff
authors.forename: Albert
authors.initials: A
authors.lastname: Schömig
authors.forename: Jörg
authors.initials: J
authors.lastname: Hausleiter
mesh_terms: D015992:Body Mass Index; D017023:Coronary Angiography / Q000009:adverse effects / Q000379:methods*; D004867:Equipment Design; D006801:Humans; D016015:Logistic Models; D018579:Patient Selection; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D018570:Risk Assessment; D014057:Tomography, X-Ray Computed / Q000009:adverse effects