Dose reduction in spiral CT coronary angiography with dual source equipment. Part II. Dose surplus due to slope-up and slope-down of prospective tube current modulation in a phantom model

Radiol Med. 2010 Feb;115(1):36-50. doi: 10.1007/s11547-010-0483-6.
[Article in English, Italian]


Purpose: This study was undertaken to estimate surplus radiation dose in retrospectively electrocardiography (ECG)-gated dual-source computed tomography coronary angiography (DSCT-CA) due to the slope-up and slope-down of the tube current using prospectively ECG-triggered tube modulation.

Materials and methods: We used an anthropomorphic phantom with an ECG-gated retrospective protocol and a DSCT scanner (Definition, Siemens). We used four tube current modulation algorithms: narrow pulsing window, with tube current reduction to 20% (A) and 4% (B) of peak current; and wide pulsing window, with tube current reduction to 20% (C) and 4% (D). Each algorithm was applied at five heart rates (HR=45, 60, 75, 90 and 120 bpm) with adaptive pitch values (0.2-0.5). Data sets were reconstructed in 5% increments from 0-95% of the R-R interval. Noise was measured at each R-R step in order to identify low noise (100% dose), medium noise (slope-up/down) and high noise (4/20% dose). Width of the transition window (slope-up/slope-down from 4/20% to 100% dose) was calculated. The surplus dose due to slope-up/slope-down was calculated.

Results: Surplus dose was 19% (A), 34% (B), 14% (C) and 21% (D). The transition window lasted 10%+10% (slope-up + down) for HR <75 bpm and all HR in C (except for 120 bpm; 25%+15%), 15%+15% for HR >90 bpm (A). For C and D, instead, the slope-up increased with progressively higher HR (10%-25% of the R-R interval, except for 90 bpm, 10%), whereas the slope-down remained constant at 5% (except for 120 bpm; 10%).

Conclusions: The adaptive ECG-pulsing windows produced an increment of the surplus dose with increasing HR. The transition window was a constant source of surplus radiation dose in the range of 14%-34%.

MeSH terms

  • Absorptiometry, Photon
  • Algorithms
  • Coronary Angiography / instrumentation*
  • Coronary Angiography / methods
  • Electrocardiography*
  • Equipment Design
  • Heart / diagnostic imaging
  • Heart Rate*
  • Humans
  • Models, Theoretical
  • Phantoms, Imaging*
  • Radiation Dosage*
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Thermoluminescent Dosimetry
  • Tomography, Spiral Computed*