Abstract 14334: Coronary Computed Tomography Angiography With Very Low Tube Voltage Reduces Radiation Dose and Maintains Image Quality
Introduction: Coronary computed tomography angiography (CTA) is increasingly used for the non-invasive evaluation of symptomatic coronary artery disease (CAD). However, potential risks of coronary CTA include exposure to ionizing radiation. Lowering tube voltage can significantly decrease radiation dose, but the effects on image quality are unknown.
Hypothesis: To determine if a very low tube voltage of 80kVp is feasible to further minimize radiation dose and maintain diagnostic image quality of coronary CTA.
Methods: We analyzed 191 consecutive patients with low-intermediate probability of CAD, who were evaluated for acute chest pain with 64-multidetector row coronary CTA (Lightspeed, GE Medical). Tube voltage protocols used either standard 120kVp, low 100kVp, or very low 80kVp, depending on physician discretion. Primary end points were radiation effective dose (mSv) and image quality assessed with a 4-point grading system (0 = excellent, 3 = nondiagnostic). Secondary analysis included the influence of body mass index (BMI) (defined as normal <24.9, overweight 25-29.9, obese 30-39.9) on image quality among the tube voltage protocols.
Results: Of the 191 CCTAs, 13 used the standard (120kVp), 90 used the low (100kVp), and 88 used the very low (80kVp) tube voltage protocols. Radiation effective dose significantly decreased with lower tube voltage (10.2 +/− 2.5mSv, 8.1 +/− 0.6mSv, and 3.1 +/− 0.2mSv, respectively, p<0.001). The 80kVp protocol was associated with a 62% relative reduction in radiation exposure as compared to the 100kVp protocol (p<0.001). There was no difference in image quality scores between tube voltage protocols (1.38 +/−0.35, 1.02 +/−0.10, 1.34 +/−0.11 for 120kVp, 100kVp and 80kVp, respectively, p = 0.09). The percentage of diagnostic CCTAs decreased with increasing BMI in the 80kVp protocol group (89.3% with normal BMI, 85.7% in overweight, 80.0% in obese). This trend was not observed with the 120kVp and 100kVp protocols.
Conclusions: In conclusion, very low tube voltage of 80kVp can be used to significantly reduce radiation exposure during CCTA while maintaining diagnostic image quality. Further work is needed to optimize individual body size protocols that minimize radiation risk and maximize diagnostic image quality.
- © 2011 by American Heart Association, Inc.