title: Image quality and radiation exposure at pulmonary CT angiography with 100- or 120-kVp protocol: prospective randomized study.
abstract: OBJECTIVE
  To prospectively compare 16-section multidetector computed tomography (CT) at 100 and 120 kVp for image quality and radiation dose.
  
  
  METHODS
  The study had institutional review board approval; written informed consent was obtained. Sixty patients were referred for evaluation of suspected pulmonary embolism with CT angiography. Patients were randomly assigned to a 100-kVp (n = 30; 17 men, 13 women; mean age, 66 years +/- 17 [standard deviation]; range, 19-89 years) or 120-kVp (n = 30; 15 men, 15 women; mean age, 62 years +/- 15; range, 28-86 years) protocol. Other scanning parameters were kept constant. Contrast medium was injected automatically with bolus tracking. Pulmonary vessel enhancement and image noise were quantified; signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. Subjective vessel contrast was assessed by two radiologists in consensus. Effective dose was calculated on the basis of dose length product and volume CT dose index. Results of both protocols were compared by using the chi(2) test and Student t test.
  
  
  RESULTS
  The 100-kVp protocol had a nonsignificantly higher mean vessel attenuation than the 120-kVp protocol (386.8 HU +/- 130.1 vs 317.9 HU +/- 112.5; P = .56) and a nonsignificantly higher image noise (16.9 HU +/- 5.8 vs 13.7 HU +/- 6.2; P = .84), which resulted in almost identical SNR (25.3 +/- 11.7 vs 27.0 +/- 14.5; P = .37) and CNR (22.0 +/- 11.2 vs 22.9 +/- 13.1; P = .51). There was no significant difference in subjective image quality between protocols. Mean effective dose for the 100-kVp protocol was significantly lower than that for the 120-kVp protocol (1.37 mSv +/- 0.39 vs 2.44 mSv +/- 0.97; -44%; P < .001).
  
  
  CONCLUSIONS
  Reduction of kilovoltage from 120 to 100 kVp resulted in significant reduction of effective dose at pulmonary CT angiography, without significant loss of objective or subjective image quality.
authors.affiliation: Institute of Diagnostic Radiology, Interventional Radiology and Nuclear Medicine, BG Clinics Bergmannsheil, Ruhr-University of Bochum, Buerkle-de-la-Camp Platz 1, D-44789, Bochum, Germany. christoph.heyer@rub.de
authors.forename: Christoph M
authors.initials: CM
authors.lastname: Heyer
authors.forename: Patrick S
authors.initials: PS
authors.lastname: Mohr
authors.forename: Stefan P
authors.initials: SP
authors.lastname: Lemburg
authors.forename: Soeren A
authors.initials: SA
authors.lastname: Peters
authors.forename: Volkmar
authors.initials: V
authors.lastname: Nicolas
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000792:Angiography / Q000379:methods*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D008297:Male; D011446:Prospective Studies; D011651:Pulmonary Artery / Q000000981:diagnostic imaging*; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging*; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D011874:Radiometry / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*