We read with interest the new draft report for consultation regarding patient and staff radiological protection in cardiology.
We would like to comment regarding the effective dose calculations for cardiac CT (line 3592) and the use of a chest conversion factor (k) applied to the DLP. Most publications to date have used a conversions factor of 0.014 or 0.017 mSv (mGy.cm)-1. The report rightly suggests that "This method provides a useful approximation of effective dose from cardiac CT based on easily available data, but it typically underestimates effective dose. “; however we have shown that chest conversion factors significantly under-estimate (by 100%) the effective dose from cardiac CT(1) and a conversion factor of 0.028 mSv (mGy.cm)-1 would give a better estimation of effective dose – a conclusion in agreement with the references text from Einstein and Christner.
We would like to suggest the ICRP take this data into consideration as, to date, this is the only paper examining effective dose from cardiac CT within in a clinical cohort.
Thank you for taking this into consideration
1- Gosling O, Loader R, Venables P, Rowles N, Morgan-Hughes G, Roobottom C. Cardiac CT: are we underestimating the dose? A radiation dose study utilizing the 2007 ICRP tissue weighting factors and a cardiac specific scan volume. Clin Radiol. 2010 Dec;65(12):1013-7.