Radiation dose in computed tomography of the heart

Radiation dose estimates for CT examinations of the heart are best expressed as CTDIvol (in Gy), DLP (in mGy X cm), and effective dose E (in mSv). These parameters are precisely defined and allow comparisons of the radiation doses of various CT imaging protocols. Currently, there are no federal or state regulations for acceptable radiation doses for specific CT examinations in the United States. Physicians referring for or performing cardiac CT examinations should understand the absorbed radiation doses associated with various protocols. This understanding may aid in making decisions as to whether a cardiac CT examination is indicated and which protocol addresses the clinical question at hand with the least radiation exposure. It is also important that reports of CT dosimetry in the growing body of literature on cardiac CT imaging be carefully worded and precisely defined, so that the absorbed radiation doses and potential risks of different protocols can be compared. The calculation and comparison of radiation doses received from specific CT imaging protocols are complicated by new scan acquisition techniques designed to decrease radiation dose to the patient. Further studies will be needed to investigate the exact effects of such modifications on the parameters currently used to express radiation dose.