Introduction Radiosraphers have a responsibility, under the Ionising Radiation (Medical Exposures) Regulations 2000 to produce ? mases of optimum diasnostic quality whilst keepms the radiation dose to patients as low as reasonably practicable - the ALARP principle In the past, numerous techniques have been utilised to minimise patient dose durins x-ray procedures, mcludins accurate positionins, careful collimation, appropriate selection of equipment, exposure factors, film-screen combinations, and throush the use of lead shielding where appropriate ; In x-ray departments with computed radiography (CR) systems, most of these techniques are still applicable. [...] the authors recosnise that FFD is more familiar to practitioners, so have used the term throughout. Research has shown that geometric factors, ie, the inverse square law, are the main contributors to dose reduction when utilising this method ' Increases the FFD has the same effect as reducins the mAs, ie, less photons reach the imase receptor, but it also has the additional benefits of reducins magnification and geometric unsharpness in the image produced5,13,14,15,16,17 Database and journal searches found no research investigating the effects of increased FFD on patient dose and image quality using a CR system, although earlier research into the effects of altering the FFD has been conducted using traditional film-screen radiosraphy, with the results demonstratins that this method can significantly reduce patient dose For example, Brennan et al16 demonstrated a 34.5% reduction in entrance surface dose for an anteroposterior (AP) pelvic examination when the FFD was increased to 130cm, with no loss of image quality.
Focussing on dose Joanne Woods; Simon Messer Synergy; Sep 2009; Docstoc pg. 16 Reproduced with permission of t
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