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June 10, 2009

Radiation Doses Associated With Cardiac Computed Tomography Angiography

JAMA. 2009;301(22):2324-2325. doi:10.1001/jama.2009.764

To the Editor: Dr Hausleiter and colleagues1 compared radiation doses resulting from different CCTA studies and concluded that identification of factors that influence radiation dose may be important. While technical characteristics clearly influence the radiation dose, major differences in radiation dose could also arise from the calculation methodology. For example, the authors calculated the effective dose using a region-specific factor of 0.014, whereas a study by Husmann et al2 used a conversion factor of 0.017. Using different methods for calculating the effective dose can be misleading. The flaw in the concept of effective dose calculation is mainly due to the disparity of the tissue-weighting factors, which stand at the foundation of effective dose calculation.3-5 To eliminate this discrepancy, DLP values rather than effective dose for different CT scenarios should be compared, because DLP calculation is standardized and it is currently displayed by a majority of the CT scanners. Moreover, the DLP reflects the total energy absorbed and thus the potential biological effect.