Using radiation safely in cardiology: what imagers need to know

### Learning objectives Exposure to ionising radiation is an important healthcare concern, primarily due to the potential increased lifetime risk of malignancy. This is important for patients and staff who are exposed to ionising radiation during diagnostic imaging or interventional procedures. Ionising radiation refers to radiation in the electromagnetic spectrum, which has enough energy to remove electrons from an atom. For the purposes of diagnostic imaging, this includes X-rays and gamma rays. The UK average background radiation dose is 2.7 mSv per year, and about 0.4 mSv (16%) of this is from diagnostic medical examinations.1 2 In the UK, the number of CT scans performed increased fivefold between 1996/1997 and 2012/2013.3 Similar trends are seen in other countries and with other imaging modalities. The USA has seen a threefold increase in the annual number of nuclear medicine procedures, and CT procedures have increased 20-fold between 1985 and 2005.4 Cardiac imaging and interventional procedures are responsible for approximately 40% of the US cumulative effective dose due to medical imaging.5 ### Estimating patient radiation dose The term ‘radiation dose’ can refer to one of several measures (table 1). Dose area product (DAP) is used in X-ray and fluoroscopic imaging (eg, invasive coronary angiography [ICA]). Radiation dose in CT is calculated from dose indices measured in standardised phantoms. Volume CT dose index (CTDIVOL) can be used to compare protocols, and dose length product (DLP) can be used to compare doses between patients for the same CT …