Comparison of radiation doses between coronary CT and catheter coronary angiography: an update

Background: Much attention has been paid to radiation exposure with CT coronary angiography (CTCA) but less to the dose associatedwith invasive catheter angiography (CA). Methods: Radiation doses were reviewed from consecutive CTCA and diagnostic CA studies (100 CTCA, 400 CA) from January 2014. CT and CA studies for bypass graft or non-coronary indications were excluded. Effective radiation doses were estimated from the dose-length product and the dose-area product using the respective chest conversion coefficients (0.014 mSv/mGy x cm and 0.20 mSv/Gy x cm2). CTCA was performed on a 128 detector row dual source scanner. Doses were then compared with 2012 when a 1st generation dual source CT scanner was in use. Results: The median effective dose for CTCA was 2.0 mSv (IQR 1.3 to 3.6) vs 9.2 mSv (IQR 6.3 to 12.8) for CA, p < 0.001. The majority of CTCA patients (87/100) underwent calcium scoring with a median additional dose of 0.7 mSv. In patients weighing < 80kg, the median CTCA dose was 1.6 mSv vs 7.0 for CA (p < 0.001). Compared with 2012, CTCA radiation doses have reduced from 5.2mSv to 2.0 mSv (p < 0.001) while there has been no significant change in CA doses (9.1 vs 9.2 mSv, p = NS). Conclusion: At our institution, radiation exposure associated with CTCA is several-fold less than that with CA. With new hardware, CTCA doses have halved since 2012 while there has been no significant change in CA over the same period.