Radiation exposure after cardiac X-ray imaging: risk and prevention in daily practise

Radiation exposure after cardiac X-ray imaging: risk and prevention in daily practise Cardiac computed tomography (CT) angiography (CCTA) has emerged as a useful diagnostic imaging modality in the assessment of coronary artery disease. However, the potential risks due to exposure to ionizing radiation associated with CCTA, and generally with low-dose ionizing radiation (5 to 100 mSv) in the population have raised concerns. The effective dose (E), expressed in units of millisieverts (mSv), is a parameter meant to reflect the risk of the biological effects of ionizing radiation. The hypothetical complication of diagnostic medical radiation exposure that is of greatest concern, the risk of inducing malignancies, is a stochastic, or random, effect in which the interaction of radiation with cellular molecules may cause damage sufficient that a malignancy may result later (30 to 40 years after). Among hypotheses applied to the discussion of carcinogenesis at low radiation doses, the linear no-threshold hypothesis states that there is no threshold below which radiation cannot cause malignancies and that the risk of malignancies increases linearly with radiation dose. The consensus opinion in the BEIR VII report advocates the conservative approach of the linear no-threshold hypothesis. In that report and a prior report by the National Commission for Radiation Protection (ICRP), the age-and gender averaged lifetime risk of dying of a malignancy attributable to radiation exposure was estimated to be 5 to 7.9 in 100 individuals of the general population per 1 Sv of E. There is conflicting evidence regarding the potential presence and degree of carcinogenesis at the levels and types of radiation associated with medical imaging : The ICRP emphasizes that E is intended for use as a parameter in radiation protection and should not be used for epidemiological evaluation or for estimations of specific human exposures; Even though the accuracy of radiation-dose estimates and the relationship between the radiation dose received from cardiac imaging and the risk of malignancies may be uncertain, National and European regulation supports the concept of keeping patient doses as low as reasonably achievable (ALARA principle) but consistent with obtaining the desired medical information. A variety of algorithms for reducing dose in CCTA are available for use in daily practice. Most of the described dose-saving strategies can be combined, resulting in an efficacious reduction of overall radiation exposure. With updated technology, the measured E can be decreased to 1 MsV, much less than the dose recorded after conventional coronarography or SPECT.