title: Vascular enhancement and image quality of MDCT pulmonary angiography in 400 cases: comparison of standard and low kilovoltage settings.
abstract: OBJECTIVE
  The purpose of this study was to investigate the vascular enhancement and image quality of pulmonary CT angiography performed with lower peak kilovoltage settings in a large patient sample.
  
  
  METHODS
  This retrospective study was approved by our institutional review board, which waived the requirement for informed consent. Four hundred patients believed to have a pulmonary embolism were studied. All patients underwent 16- or 64-MDCT with automatic tube current modulation. The 200 patients in the standard peak kilovoltage group (mean age, 57 years; range, 22-95 years) underwent MDCT at 130 or 120 kVp. The 200 patients in the low peak kilovoltage group (mean age, 56 years; range, 21-92 years) underwent MDCT at 110 or 100 kVp. Vascular enhancement was evaluated by measurement of the attenuation value in the main pulmonary artery and segmental and subsegmental arteries. Image noise was quantified by measurement of the SD of the attenuation value in the main pulmonary artery. One blinded radiologist assessed image quality using visual scores. Wilcoxon's rank test was used to evaluate differences between the groups.
  
  
  RESULTS
  Mean vascular enhancement in the main pulmonary artery had significantly higher attenuation values in the low peak kilovoltage group (376.1 +/- 102.9 HU) than in the standard peak kilovoltage group (309.2 +/- 94.8 HU) (p < 0.0001). Mean attenuation values in all measured segmental and subsegmental arteries were significantly higher in the low peak kilovoltage group than in the standard peak kilovoltage group (p < 0.0001). Image noise in the low peak kilovoltage group was significantly higher than in the standard peak kilovoltage group (p < 0.0001). There was no significant difference in the image quality scores of the two groups (p = 0.116).
  
  
  CONCLUSIONS
  Lowering kilovoltage improved vascular enhancement without deterioration of image quality. The results of our study confirm previously reported preliminary findings.
authors.affiliation: Department of Radiology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA. shin4114@mac.com
authors.forename: Shin
authors.initials: S
authors.lastname: Matsuoka
authors.forename: Andetta R
authors.initials: AR
authors.lastname: Hunsaker
authors.forename: Ritu R
authors.initials: RR
authors.lastname: Gill
authors.forename: Isabel B
authors.initials: IB
authors.lastname: Oliva
authors.forename: Beatrice
authors.initials: B
authors.lastname: Trotman-Dickenson
authors.forename: Francine L
authors.initials: FL
authors.lastname: Jacobson
authors.forename: Hiroto
authors.initials: H
authors.lastname: Hatabu
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000792:Angiography / Q000379:methods*; D001822:Body Burden; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011651:Pulmonary Artery / Q000000981:diagnostic imaging*; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging*; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D055815:Young Adult