What is electrocardiograph (ECG)-dependent tube current modulation for coronary computed tomography angiography (CCTA)?

Updated: Dec 21, 2017
  • Author: Eugene C Lin, MD; Chief Editor: Eugene C Lin, MD  more...
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Anatomic-based tube current modulation can be performed where the tube current is adjusted for patient size and shape. However, a more effective method of dose reduction is electrocardiograph (ECG)-dependent tube current modulation. As the best image quality for CCTA is typically obtained at the specific phase of the R-R interval (usually mid- to end-diastole), the tube current (and thus dose) can be reduced in the phases where image quality is not optimal. [52] This is the most common method to reduce radiation dose. The primary disadvantage of this technique is that optimal functional imaging is not possible because of poor image quality in the portions of the cardiac cycle where lower tube current was used. The use of ECG-dependent dose modulation can result in a 20-50% decrease in radiation dose. [3] This technique can be optimally used with dual-source CT, as the time requiring the highest tube current is shorter.

Slow and steady heart rates are necessary for effective ECG-dependent dose modulation. At high heart rates, the period of reduced tube output (diastolic duration) becomes shorter relative to the cardiac cycle. With irregular heart rates, the optimal time point in the cardiac cycle to apply the full tube current is less predictable.

Society of Cardiovascular Computed Tomography (SCCT) guidelines [53] recommend ECG-based, tube-current modification in retrospective gated studies, except in patients with highly irregular heart rhythms.

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