What is the amount of radiation in a Coronary Computed Tomography Angiography (CCTA)?

Radiation Exposure in Coronary Computed Tomography Angiography (CCTA)

The typical effective radiation dose for CCTA ranges from 3 to 10 mSv, with modern techniques and dose-reduction strategies allowing for doses as low as 2-5 mSv. 1

Radiation Dose Comparison

CCTA radiation exposure can be understood in context:

• Standard CCTA: 10 mSv average (without dose reduction) 1
• CCTA with dose-reduction techniques: 3-5 mSv 1
• Annual background radiation exposure: 3.1 mSv 1
• Invasive coronary angiography: 7 mSv 1
• Chest X-ray: 0.05 mSv (CCTA is equivalent to approximately 60-200 chest X-rays) 1

Factors Affecting CCTA Radiation Dose

Several factors influence the radiation dose in CCTA:

• Acquisition protocol: Retrospectively gated scans (12-25 mSv) deliver significantly higher doses than prospectively triggered scans (3-5 mSv) 1
• Patient characteristics:
  • Body weight (5% increase in dose per unit increase) 2
  • Heart rhythm (irregular rhythms require 10% higher doses) 2
• Technical factors:
  • Tube voltage (100 kV vs 120 kV reduces dose by 46%) 2
  • ECG-controlled tube current modulation (reduces dose by 25%) 2
  • Sequential scanning (reduces dose by 78% compared to helical) 2
  • Scanner type (dose varies by up to 97% between different 64-slice CT systems) 2

Dose Reduction Strategies

Modern CCTA protocols incorporate several dose-reduction techniques:

• Prospective ECG triggering: Limits X-ray exposure to specific phases of the cardiac cycle
• Lower tube voltage: Using 100 kV instead of 120 kV in non-obese patients
• Tube current modulation: Adjusts radiation output based on ECG and tissue density
• Iterative reconstruction: Maintains image quality with lower radiation doses
• High-pitch helical acquisition: Significantly reduces radiation exposure 3

Clinical Considerations

When considering CCTA, clinicians should:

1. Follow appropriate use criteria: Limit exposure to patients who meet appropriate indications based on ACC guidelines 1
2. Apply ALARA principle: Use As Low As Reasonably Achievable dose for all patients 1
3. Consider alternative tests: For low-risk premenopausal women, tests without radiation exposure (e.g., stress echocardiography) may be preferable 1
4. Balance risk vs. benefit: The small projected cancer risk must be weighed against the potential benefit of IHD risk detection 1

Temporal Trends

Radiation doses from CCTA have decreased significantly over time:

• In 2005-2007, median doses were 12-13 mSv 2, 3
• By 2010-2012, median doses decreased to 3.3-3.7 mSv (74.8% reduction) 3, 4
• Current guidelines report typical doses of 3-5 mSv with modern equipment and protocols 1

The significant reduction in CCTA radiation exposure over time reflects technological advances and increased awareness of dose optimization strategies, making CCTA a more acceptable option from a radiation safety perspective.