Diagnostic and therapeutic radiological investigations are an essential part of the workup of patients with a number of clinical problems across a variety of medical specialties. Although new non-x ray technologies have started to replace traditional investigations these have not lead to a reduction in radiation exposure. In contrast, based on global statistics and projections, radiation exposure of patients is increasing, in particular as a result of new indications and use in cross sectional imaging.¹ In addition, multiple investigations of patients with chronic disease can lead to substantial individual radiation exposure as surgical practice increasingly relies on the use of cross sectional imaging to aid diagnosis and treatment.² New imaging techniques, in particular computed tomography (CT) colonography, have become attractive alternatives to conventional colonoscopy.³ However, the necessity for both prone and supine scanning means that radiation exposure is double that of a conventional abdominal scan which …