Comparison of radiation dose and image quality: 320-MDCT versus 64-MDCT coronary angiography

AJR Am J Roentgenol. 2011 Jul;197(1):163-8. doi: 10.2214/AJR.10.5250.


Objective: The purpose of this study was to compare radiation dose and image quality of 320- and 64-MDCT angiography using prospective gating.

Materials and methods: One hundred seventy-four patients underwent 320-MDCT, and 95 patients underwent 64-MDCT. The scan parameters for 320-MDCT were 120 kVp, 400 mA, and gantry rotation of 350 milliseconds; the parameters for 64-MDCT were 120 kVp, 600 mA, and gantry rotation of 350 milliseconds. Effective dose (ED) was calculated from the dose-length product and a conversion factor (k = 0.014 mSv / mGy × cm). Two observers independently assessed image quality using a 3-point scale, where 3 denotes excellent quality and 1 denotes nondiagnostic quality, using a 16-segment model. Discrepancies were settled by consensus.

Results: The ED was significantly lower in patients undergoing 320-MDCT angiography, with a median ED of 4.4 mSv (interquartile range [IQR], 3.4-6.2 mSv), compared with 64-MDCT angiography, with a median ED of 6.2 mSv (IQR, 5.5-6.9 mSv) (p = 0.0001). In patients with a heart rate of 65 beats/min or less (92%), the median radiation dose using 320-MDCT was 4.1 mSv (IQR, 3.2-6.1 mSv), and that for 64-MDCT angiography was 6.2 mSv (IQR, 5.8-6.9 mSv) (p = 0.0001). In patients with heart rate greater than 65 beats/min (8%), the median dose was higher with 320-MDCT (8.7 mSv; IQR, 5.9-14.3 mSv) than with 64-MDCT (5.8 mSv; IQR, 5.3-6.7 mSv) (p = 0.02). Segmental image quality was significantly better for 320-MDCT (excellent or good quality, 96.66%; nondiagnostic quality, 0.1%) than for 64-MDCT angiography (excellent or good quality, 86%; nondiagnostic quality, 3.33%) (all p < 0.0001).

Conclusion: Image quality was good for both 320- and 64-MDCT angiography. Overall radiation dose was significantly lower in 320-MDCT angiography when the heart rate was 65 beats/min or less. Every effort should be made to control heart rate to minimize radiation dose.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Coronary Angiography / methods*
  • Coronary Artery Disease / diagnostic imaging*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Radiation Dosage*
  • Radiometry
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Tomography, X-Ray Computed / instrumentation
  • Tomography, X-Ray Computed / methods*