Content area
Full Text
Introducing a study to determine the effect of source to image receptor distance on entrance surface dose, dose area product and image quality of AP pelvic radiographs when using computed radiography.
Introduction
Diagnostic x-rays are the largest man-made source of radiation, accounting for 14% of the population's total annual exposure worldwide1. It is therefore of utmost importance to investigate methods of reducing patient dose. Pelvic x-ray examinations are responsible for the third highest number of cases of radiation-induced cancer1 and the Commission of European Communities guidelines2 state that the average entrance surface dose (ESD) for a particular examination is a useful measure of the level of a patient's radiation protection in an imaging department. The dose reference level for an antero-posterior (AP) pelvis is an ESD of 4mGy per radiograph and a dose area product (DAP) of 3Gycm9 per radiograph3.
According to the International Commission of Radiological Protection (ICRP)1, there are two basic principles of radiation protection of the patientjustification of procedure and optimisation of protection, which includes the consideration of dose reference levels. Graham & Cloke suggest that the best ways of minimising the amount of radiation received by patients are to limit the field size by appropriate collimation, using highest practicable kV and implementing the use of autotimers to control exposure time5. It is in this way that this research may affect the future practice of all radiographers and assistant practitioners because it is linked with the ALARP (as low as reasonably practicable) principle.
The study focuses on computed radiography (CR) systems because, to date, although there has been much research into source-to-image receptor distance (SID) and effective dose, there has not been any undertaken using CR systems. However, Vano et al6 report the median values of ESDs to have increased 40-103% after the implementation of CR. DAP has been used because it is an indicator of effective dose and is more efficient than thermo luminescent detectors (TLDs). DAP readings are also useful to check if collimation is consistent.
Grondin et al7 suggest that, by using SID changes in conjunction with other dose reducing strategies, it is possible to decrease effective dose by up to 77% for AP pelvis examinations, without a significant reduction in image quality. Meanwhile, Potetti & McLean8...