Abstract
Optimisation of radiological protection is one of the most challenging activities for the new imaging technologies in medicine. It requires involvement of the full imaging team of radiologists, radiographers, and medical physicists, but also the input of technical personnel from the vendors and, in part, the hospital management. The new technologies require a continuous interaction with the vendor representatives, especially after updates of software and hardware of the x-ray systems. The use of dose management systems or automated exposure information systems in optimisation may also be helpful in improving optimisation and radiation safety aspects, and is being integrated as part of the quality programme in many radiology departments.
One of the advantages, but also one of the challenges, of digital imaging is that it is possible to select the quality of the images for a clinical task or clinical indication. The term ‘image quality’ should also be understood as ‘diagnostic information’ when several series of images are obtained during a procedure. More quality in the images, or more diagnostic information, requires the use of a greater radiation dose. Many physics parameters are involved in the different operational protocols (kV, mA, pulse time, filtration, geometry, image acquisition modes, etc.), and specific training for optimisation is required for the new x-ray systems. In addition, patient size, the ability of patients to cooperate (especially in paediatrics), and some specific situations (e.g. pregnant patients) may require particular operational protocols. The priority should always be to obtain the required diagnostic information for the clinical task, with the minimum radiation dose for the patient.
Consideration of occupational protection should also be one of the aspects to be integrated into the full optimisation process for some interventional procedures, as recommended in Publication 139 on ‘Occupational radiological protection in interventional procedures’ (ICRP, 2018). Other non-radiation-related risks (e.g. use of contrast agents, medications, sedation/anaesthesia, etc.) should also be considered for some optimisation actions.
The recommended operational protocols may be suggested by the vendors initially, but they need to be tested and, in some cases, adapted for individual patients. In these cases, the roles of radiologists (or other medical doctors involved in the imaging procedure), radiographers, and medical physicists are especially important. Radiation dose may be fairly easy to measure (or calculate), and modern x-ray systems offer this information, but the image quality or diagnostic information needed for the clinical tasks may be more difficult to establish in some cases.
Sometimes, several, or even many, images are necessary, using different acquisition modes (especially for interventional procedures). The impact of new technologies and post-processing of the images may improve the diagnostic information obtained from the images considerably. Radiologists should know the level of radiation dose involved in the different operational protocols when deciding the required image quality (or amount of diagnostic information).
Initial and continuing training for optimisation strategies are relevant aspects to be integrated in radiology departments. The cooperation of the technical staff of the vendors should also be considered.
This publication contains detailed recommendations and will be used in many hospitals to help in the practical aspects of optimisation for the three most relevant imaging modalities: digital radiography; fluoroscopy/interventional radiology; and computed tomography. Two additional short chapters are dedicated to paediatric procedures and examinations of pregnant patients. This publication contains the main points for every chapter, summarised conclusions, and two annexes on ‘Dose quantities and units’ and ‘Automated exposure information reporting systems’.
This publication discusses the three main areas for good management of optimisation: (i) collaboration between radiologists and other physicians, radiographers, medical physicists, and managers; (ii) access to the appropriate methodology, technology, and expertise; and (iii) provision of organisational processes to ensure that equipment performance tests, patient dose surveys, and reviews of protocols are undertaken at appropriate time intervals.
The needs for proper initial education and ongoing training of staff on the operation of equipment, both of which are crucial in achieving optimisation, are highlighted. Aspects of artificial intelligence and the advantages of iterative reconstruction for computed tomography should form part of the training.
This publication suggests three levels of optimisation – basic, intermediate, and advanced – with preliminary planning in order to start the process. Optimisation is not a static process. It requires constant attention with frequent monitoring of performance, feedback of experience, and regular review. Medical physicists should follow the values of patient dose indicators for a periodic comparison with diagnostic reference levels (DRLs), and new imaging protocols (especially with new x-ray systems or new software) could require new local DRLs to be set. This is much easier when a dose management system or automated exposure information system is available.