SCIENTIFIC LETTER Cardiac catheterisation: radiation doses and lifetime risk of

ardiac catheterisation and angiography uses ionisingradiation and therefore produces a radiation dose to thepatient and to the operating staff. The dose to the patientcan be measured using thermoluminescent dosemeters placedon the skin or by using a large-area detector attached to the xray tube to measure the dose–area product (DAP) for theincident x ray beam (DAP meter). The DAP is particularly usefulfor assessing and comparing the radiation dose from screeningprocedures. It provides a more useful indication of the overallpatient exposure than measurement of surface dose atparticular locations. The dose measurement is used either as asurrogate for radiation risk or as a step in actually estimatingthe risk. Published factors allow conversion of the DAP toeffective dose, a derived quantity in which doses to differentorgans or tissues are weighted according to their radio-sensitivity and summed to give a risk-related dose quantity.