Radiation dose is of concern in coronary CT angiog¬raphy: a very recent international survey of 50 sites which routinely perform coronary CT angiography— the PROTECTION I study—revealed that some centers performed their scans with average effective radiation doses as high as 30 mSv [1]. However, these high doses are only one end of what is really a spectrum—in fact, a quite extreme end of that spectrum. In PROTECTION I, some sites used average dose as low as 5 mSv, and the median effective dose associated with coronary CT angiog¬raphy in a total of 1,965 patients was 12 mSv.