title: Effect of Tube Voltage (100 vs. 120 kVp) on Radiation Dose and Image Quality using Prospective Gating 320 Row Multi-detector Computed Tomography Angiography.
abstract: OBJECTIVE
  The objective of the following study is to evaluate the effect of reducing tube voltage from 120 to 100 kVp using prospective gating 320 row multi-detector computed tomography angiography on image quality and reduction in radiation dose.
  
  
  METHODS
  A total of 78 sequential patients were scanned with prospective electrocardiogram gating. A total of 45 patients (Group 1) with mean body mass index (BMI) 29 ± 2 and heart rate (HR) 57 ± 7 beats per minute (BPM) were scanned at 120 kVp. 33 patients (Group 2) with mean BMI 23 ± 3 and HR 58 ± 6 bpm were scanned at 100 kVp. Effective dose was calculated using dose length product and factor (k = 0.014). Quantitative assessment of image quality was calculated by measuring signal to noise ratio (SNR) and contrast to noise ratio (CNR) in the left ventricle and left main coronary artery. Two experienced cardiac radiologists using a three-point ordinal scale assessed subjectively image quality.
  
  
  RESULTS
  In Group 1, the median radiation dose was 5.31 mSv (95% confidence interval [CI]: 4.86-6.09) and for Group 2 (P = 0.009) the mean radiation dose was 3.71 mSv (95% CI: 2.76-4.87), representing 30% decrease in radiation dose. In multivariate analyses, adjusting for age, gender, HR, BMI, tube current and scan length, an absolute median reduction of 2.21 mSv (1.13-3.29 mSv) was noted in patients scanned with 100 kVp (P < 0.0001). The quantitative image quality (SNR and CNR) was not statistically significant between the groups. Subjective image quality was rated as good or excellent in 99% of coronary segments for both groups (P value was considered as non-significant).
  
  
  CONCLUSIONS
  Our study suggests that radiation dose may be lowered from 120 to 100 kVp with preservation of image quality in patient's whose BMI is ≤27.
authors.affiliation: Department of Radiology, Beth Israel Deaconess Medical Center, Harvard University, Boston, MA, USA.
authors.forename: Atif N
authors.initials: AN
authors.lastname: Khan
authors.affiliation: Department of Radiology, Emory University Hospital Midtown, Atlanta, GA, USA.
authors.forename: Faisal
authors.initials: F
authors.lastname: Khosa
authors.affiliation: Department of Radiology, Emory University Hospital Midtown, Atlanta, GA, USA.
authors.forename: Waqas
authors.initials: W
authors.lastname: Shuaib
authors.affiliation: Department of Cardiology, Yale University School of Medicine, New Haven, CT, USA.
authors.forename: Khurram
authors.initials: K
authors.lastname: Nasir
authors.affiliation: Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Ron
authors.initials: R
authors.lastname: Blankstein
authors.affiliation: Department of Radiology, Beth Israel Deaconess Medical Center, Harvard University, Boston, MA, USA.
authors.forename: Melvin
authors.initials: M
authors.lastname: Clouse
keywords: Dose reduction; image quality; multi-detector computed tomography angiography; tube voltage