Digital subtraction angiography (DSA) is based on digital image processing with logarithmic subtraction and edge enhancement. It is used increasingly for the visualization of blood vessels throughout the body. The bulk of the workload in the angiography suite at the Queen Elizabeth Hospital, Birmingham involves carotid and femoral angiograms with other examinations, including hepatic and renal angiograms, being carried out less frequently. A typical DSA examination involves both fluoroscopy and DSA images taken at different projections and at different regions of the body. The exposure factors are selected automatically and the ease of image acquisition facilitates the acquisition of large numbers of images—exceeding 100 for some studies. Some examinations, but predominantly femoral angiograms, also involve the use of Puck serial films with the exposure factors being selected manually. The screening time, number of DSA or Puck images and the exact projection and exposure factors used varies between patients. The dose to different patients varies enormously and, as with all medical radiation exposure, should be clinically justified. Taylor et al (1989) measured the entrance absorbed dose for a posteroanterior (PA) projection using a Rando anthropomorphic phantom and concluded that radiation doses to patients undergoing DSA examinations are amongst the highest for any X-ray procedure. The patient dose is increased because DSA images are taken using low voltages (e.g. 60–70 kVp) if technically possible in order to maximize image contrast.