Finding the optimal dose reduction and iterative reconstruction level for coronary calcium scoring

Area of Science:

• Radiology
• Medical Imaging
• Cardiovascular Disease

Background:

• Coronary artery calcium (CAC) scoring is crucial for cardiovascular risk assessment.
• Optimizing radiation dose in CT imaging is a key concern.
• Iterative reconstruction (IR) techniques offer potential for dose reduction in CT scans.

Purpose of the Study:

• To determine the maximum achievable radiation dose reduction for CAC scoring using iterative reconstruction (IR).
• To evaluate the impact of dose reduction on the accuracy and interpretability of CAC scoring.
• To assess patient reclassification rates at reduced radiation doses.

Main Methods:

• A phantom and a within-patient study involving 30 participants were conducted.
• Coronary artery calcium scoring was performed at four dose levels (100%, 60%, 40%, 20%) using a 256-slice CT scanner.
• Data were reconstructed using filtered back-projection (FBP) and three levels of IR, with Agatston, volume, and mass scores analyzed.

Main Results:

• Phantom studies indicated stable Agatston scores down to 40% dose with FBP, but increased noise at lower doses.
• With IR, all CAC scoring reconstructions were interpretable even at 20% dose.
• IR lowered Agatston scores at 20% dose, with strong IR leading to 15% reclassification.

Conclusions:

• Iterative reconstruction allows for significant radiation dose reduction (up to 80%) in CAC scoring.
• Effective doses can be reduced to 0.15-0.18 mSv while maintaining interpretability.
• Applying the highest IR level keeps reclassification rates within 15% at these reduced doses.