Risk stratification using coronary artery calcium scoring based on low tube voltage computed tomography

Area of Science:

• Radiology
• Cardiovascular Imaging
• Medical Physics

Background:

• Coronary artery calcium (CAC) scoring is crucial for cardiovascular risk stratification.
• Standard CAC scoring protocols utilize 120 kilovolt-peak (kVp) computed tomography (CT).
• Lowering kVp in CT can reduce radiation dose but may impact image quality and diagnostic accuracy.

Purpose of the Study:

• To evaluate the accuracy of CAC scoring using reduced tube voltages (80 kVp and 70 kVp) compared to the standard 120 kVp protocol.
• To assess the impact of kVp-adapted scoring thresholds on risk reclassification and agreement.
• To determine the radiation dose reduction achieved with lower kVp protocols.

Main Methods:

• Prospective study of 170 patients undergoing CAC scanning at 120 kVp, 80 kVp, and 70 kVp.
• Tube current was adapted to maintain consistent image noise across scans.
• Novel kVp-adapted thresholds were applied for CAC score calculation at lower kVp settings.
• Risk reclassification rates and agreement (Kendall's Tau-b) were compared against the 120 kVp standard.

Main Results:

• Good agreement was observed between 80 kVp and 120 kVp (Τb=0.967) and 70 kVp and 120 kVp (Τb=0.915) scans.
• Reclassification rates were 7.1% for 80 kVp and 17.2% for 70 kVp, primarily towards lower risk categories.
• Radiation dose was reduced from 0.54 mSv (120 kVp) to 0.42 mSv (80 kVp) and 0.26 mSv (70 kVp).
• Reclassification rates were influenced by body mass index (BMI).

Conclusions:

• CAC scoring using reduced tube voltage (80 kVp and 70 kVp) allows for accurate cardiovascular risk stratification.
• Application of kVp-adapted thresholds is essential for maintaining accuracy with lower kVp protocols.
• Reduced kVp protocols offer significant radiation dose savings without compromising risk assessment efficacy.