Use of medical imaging continues to increase, making the major contribution to population exposure from artificial sources of radiation world-wide. The principle of optimisation of protection is that the likelihood of incurring exposures, the number of people exposed, and the magnitude of their individual doses should all be kept as low as reasonably achievable (ALARA), taking into account economic and societal factors. Optimisation for medical imaging requires more than ALARA, it implies keeping patient exposure to the minimum necessary to achieve the required medical objective. In other words, the number and quality of images must be adequate to obtain the information needed for diagnosis or intervention. Dose reductions for imaging or x-ray image-guided procedures should not be used if they degrade image quality to the point where it is inadequate for the clinical purpose. The move to digital imaging has provided versatile acquisition, post-processing, and presentation options, but because images are adjusted for optimal viewing, the appearance may not give any indication if the dose is higher than necessary. Nevertheless, digital images provide opportunities for further optimisation and offer the possibility of applying artificial intelligence methods in the future.
Optimisation of radiological protection for digital radiology of patients (radiography, fluoroscopy and computed tomography) involves selection and installation of equipment, design and construction of facilities, choice of optimal equipment settings, day-to-day methods of operation, quality control programmes, and ensuring that all personnel receive proper initial and career-long training. The radiation dose levels that patients receive also have implications for doses to staff. As new imaging equipment incorporates more options to improve performance, it becomes more complex and less easily understood, so operators have to be given more extensive training. Ongoing monitoring, review, and analysis of performance is required that feeds back into the improvement and development of imaging protocols. Several different aspects relating to optimisation of protection that need to be developed are set out in this report. The first is collaboration between radiologists/clinicians, radiographer/imaging technologists, and medical physicists, each of whom have key skills that can only contribute to the process effectively when individuals work together as a core team. The second is appropriate methodology and technology, with the knowledge and expertise required to use each effectively. The third relates to organisational processes that ensure required tasks, such as equipment performance tests, patient dose surveys, and review of protocols are carried out.
There is a wide range in equipment, funding, and expertise around the world, and the majority of facilities do not have all the tools, professional teams and expertise to fully embrace all the possibilities for optimisation. Therefore, this report sets out broad levels for aspects of optimisation that different facilities might achieve, and through which they can progress incrementally; D: Preliminary, C: Basic, B: Intermediate, and A: Advanced. Examples of systems and activities that should be in place to achieve different levels are set out. Imaging facilities can then evaluate arrangements they already have and use the document to guide decisions about the next actions to be taken in optimising their imaging services.
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