Radiation from CT and perfusion scanning in pregnancy

A mistyped abbreviation led to an error in a unit in this letter by J Valmai Cook and John Kyriou (BMJ 2005;331:350, 6 Aug). In the second paragraph, in relation to low dose technetium-99m perfusion lung scans, we should have said 50 megabecquerels (not millibecquerels). Also, we spelt out CTPA as computed tomography for pulmonary angiography, whereas the procedure is more usually referred to as computed tomography pulmonary angiography.