ICRP Publication 154
Optimisation of Radiological Protection in Digital Radiology Techniques for Medical Imaging
Recommended citation
ICRP, 2023. Optimisation of radiological protection in digital radiology techniques for medical imaging. ICRP Publication 154. Ann. ICRP 52(3)
Authors on behalf of ICRP
C.J. Martin, K. Applegate, I. Hernandez-Giron, D. Husseiny, M. Kortesniemi, M. Del Rosario Perez, D.G. Sutton, J. Vassileva
Abstract - Use of medical imaging continues to increase, making the largest contribution to the exposure of populations from artificial sources of radiation worldwide. 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 involves more than ALARA – it requires keeping individual patient exposures to the minimum necessary to achieve the required medical objectives. In other words, the type, 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 the images are inadequate for the clinical purpose. The move to digital imaging has provided versatile acquisition, post-processing, and presentation options, and enabled wide and often immediate availability of image information. However, 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 allow the application of artificial intelligence methods. Optimisation of radiological protection for digital radiology (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 publication. The first is collaboration between radiologists/other radiological medical practitioners, radiographers/medical radiation 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 which ensure that required tasks, such as equipment performance tests, patient dose surveys, and review of protocols, are carried out. There is wide variation 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 publication sets out broad levels for aspects of optimisation that different facilities might achieve, and through which they can progress incrementally: Level D – preliminary; Level C – basic; Level B – intermediate; and Level A – advanced. Guidance from professional societies can be invaluable in helping users to evaluate systems and aid in adoption of best practice. Examples of systems and activities that should be in place to achieve the different levels are set out. Imaging facilities can then evaluate the arrangements they already have, and use this publication to guide decisions about the next actions to be taken in optimising their imaging services.
MAIN POINTS
EXECUTIVE SUMMARY
(a) Optimisation is a key principle of radiological protection. Medical exposures make the largest contribution to the exposure of populations from artificial sources of ionising radiation worldwide, so optimisation of such exposures is particularly important. Optimisation of radiological protection for imaging requires radiation dose to be minimised in a manner that is consistent with providing the images/information required for the intended purpose. Digital radiology encompasses all radiological techniques that present images in digital form, for which the appearance can be manipulated to display the image in a form that best suits the purpose, and includes digital radiography, fluoroscopic techniques, and computed tomography. The emphasis on image quality has become crucial in digital radiology with more versatile image acquisition, post-processing, and presentation options. These techniques require a more rigorously defined optimisation process, awareness of underlying technical factors that are not always obvious, and comprehension of the impact of information technology on the displayed image. The clinical risk of patient mismanagement resulting from an examination for which the dose has been reduced to the point at which the image quality is insufficient to allow changes in diseased or damaged tissue to be characterised is likely to be high compared with any additional risk from a higher radiation exposure that gives sufficient image quality. However, cumulative radiation doses from the ever-increasing use of radiology may result in health consequences that, although not immediately apparent, could manifest at a later point in time. Thus, it is a question of balance between different types of risk (potential long-term effects from dose and more immediate clinical consequences), and achieving the correct balance is a challenging task from both technical and professional perspectives.
(b)To achieve successful optimisation, a facility must have sufficient imaging equipment, and enough staff who have been adequately trained in use of the equipment and the information technology features that are available. The optimisation process starts with specification of the equipment required to fulfil the clinical need, and continues through its purchase, installation, acceptance, and commissioning. It includes maintenance and the quality assurance programme which continue throughout the life cycle of the equipment. Optimisation then continues during clinical use of the equipment, with requirements for provision of necessary clinical information by those referring patients for examinations based on accepted guidelines, and appropriate processes for reporting and acting on results of imaging procedures.
(c) Optimisation requires the input of knowledge and skills on many different aspects of how radiological images are formed, and so requires contributions from different healthcare professionals working together as a team. A radiologist, other appropriately trained radiological medical practitioner, or radiographer can judge whether the image quality is sufficient for the diagnostic purpose. A radiographer should know the practical operation and limitations of the equipment and associated information technology, and have a basic knowledge of the physical principles of image formation and interpretation of measurements on images. A medical physicist should have a deeper understanding of the physical principles behind image formation, and be able to perform and interpret measurements of dose and image quality. In order to achieve optimisation, the three specialities, together with other healthcare professionals who will sometimes be involved, must have mutual respect for their individual skills and work together as a cohesive group (i.e. professionalism). Unfortunately, at the time of preparation of this publication, the levels of knowledge and skills in many countries are often inadequate to achieve good optimisation on more complex digital radiology systems due to lack of resources. Increasing technical and computational complexity in radiology equipment and applications underlines the importance of multi-professional collaboration and dependency on the combined knowledge of different professionals. Dedicated time must be made available for professionals to work together to meet emerging challenges in optimisation as applications of new equipment are developed.
(d) Digital imaging provides the potential for images to be obtained with lower exposures than previously possible using film screen combinations, enabling levels to be adapted to the diagnostic requirements of specific examinations. New techniques are continuously becoming available that can improve image quality and potentially enable diagnostic images to be obtained with lower patient doses. As an example, automated exposure control systems are continuously developed to be more effective in ensuring consistent image quality while reducing patient dose by adapting the radiation level to each procedure and the patient. However, all of these features introduce additional complexities and require settings to be chosen correctly for proper operation of software controls. If users do not deploy them effectively due to limited awareness of their mode of operation, the doses received by patients may not be optimal, but this will not be apparent to the user. Therefore, more complex equipment requires knowledgeable staff with more extensive training for its operation. Knowledge and skills, in combination with the instruments and test objects to evaluate the performance of the equipment, form the basis of optimisation (i.e. methodology).
(e) A key component of optimisation is keeping the radiation dose to the patient as low as reasonably practicable, while maintaining an adequate level of image quality and diagnostic information. At the basic level, this requires regular assessments of doses from groups of patients to determine the dose levels, and comparisons with diagnostic reference levels to confirm acceptability. Evolving technical optimisation features and quality management systems will enable extension of the optimisation process to individual patients and procedures based on clinical indication. Operators must have the knowledge and skills to use such features appropriately, and if they do not, important opportunities will be lost. Such an indication and patient-specific level of optimisation is applied routinely every day in radiology departments, and is a fundamental extension of the conventional optimisation principle (known as ‘as low as reasonably achievable’) as applied to patients. Indication orientation and patient specificity connect the optimisation process directly to the justification process, and enable them to be mutually supportive and comprehensive, forming a unitary process for radiological protection.
(f) Evaluation of image quality as part of quality assurance/quality control programmes typically involves evaluation of clinical images by an experienced radiologist, other appropriate radiological medical practitioner, or radiographer against established good image quality criteria, and objective analysis of phantom images by a medical physicist. Further net improvements could be gained in the future through automated image quality evaluation based directly on clinical patient images, and may involve artificial intelligence algorithms implemented directly into image archives or imaging modalities. Regardless of the present or future methodology, the process of measuring image quality involves many interdependent parameters and, due to this comprehensive nature, is a pivotal part of the overall assessment of performance. Results from evaluations of clinical image quality, coupled with results from patient dose and image quality measurements, feed into the development of examination protocols optimised for the clinical purpose. To ensure that optimisation processes are carried out consistently, management systems need to be in place to confirm that measurements and assessments are made, to ensure that available data from clinical use and performance measurements are used in making adjustments to protocols to address any deficiencies, and to monitor the progress that is made (i.e. process management).
(g) The degree to which any organisation has implemented optimisation in digital radiology will depend on the personnel, facilities, and level of knowledge and experience available. Within the aspects of professionalism, methodology, and process, there will be different levels of performance that radiology facilities will have achieved. This publication sets out broad categories for the systems that would be in place to achieve different levels of optimisation: Level D – preliminary; Level C – basic; Level B – intermediate; and Level A – advanced. It is hoped that evaluation of the arrangements that radiology facilities already have in place will provide a guide to decisions about what actions should be taken next to improve optimisation of their imaging service. It is also noted that these categories (Levels D, C, B, and A) with increasingly advanced optimisation methods also reflect the increasing capability to reach indication-oriented and patient-specific optimisation processes.
(h) There is a need for a cultural change in order to enable improvements and developments in optimisation methods, and to avoid key processes being overlooked. Optimisation will only be achieved through facilities investing in adequate staffing levels to operate their imaging equipment, and providing the appropriate training, together with continuing professional development opportunities for their staff. This begins at the stage of entry into medical imaging professions with sufficient courses for the education of trainees with opportunities to learn under the guidance of experienced practitioners. Knowledge and understanding are key to successful optimisation of radiological imaging. The cultural shift towards multi-professionalism required can only occur if the professional roles and competences are built to support this fundamental shift.
(i) This publication provides guidance on the adaptation of levels of dose and image quality to clinical tasks, taking advantage of the wide dynamic range offered by digital imaging equipment. Practical aspects that depend on specific x-ray image acquisition techniques are covered in a separate companion publication.
ICRP, 2023. Optimisation of radiological protection in digital radiology techniques for medical imaging. ICRP Publication 154. Ann. ICRP 52(3)
Authors on behalf of ICRP
C.J. Martin, K. Applegate, I. Hernandez-Giron, D. Husseiny, M. Kortesniemi, M. Del Rosario Perez, D.G. Sutton, J. Vassileva
Abstract - Use of medical imaging continues to increase, making the largest contribution to the exposure of populations from artificial sources of radiation worldwide. 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 involves more than ALARA – it requires keeping individual patient exposures to the minimum necessary to achieve the required medical objectives. In other words, the type, 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 the images are inadequate for the clinical purpose. The move to digital imaging has provided versatile acquisition, post-processing, and presentation options, and enabled wide and often immediate availability of image information. However, 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 allow the application of artificial intelligence methods. Optimisation of radiological protection for digital radiology (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 publication. The first is collaboration between radiologists/other radiological medical practitioners, radiographers/medical radiation 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 which ensure that required tasks, such as equipment performance tests, patient dose surveys, and review of protocols, are carried out. There is wide variation 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 publication sets out broad levels for aspects of optimisation that different facilities might achieve, and through which they can progress incrementally: Level D – preliminary; Level C – basic; Level B – intermediate; and Level A – advanced. Guidance from professional societies can be invaluable in helping users to evaluate systems and aid in adoption of best practice. Examples of systems and activities that should be in place to achieve the different levels are set out. Imaging facilities can then evaluate the arrangements they already have, and use this publication to guide decisions about the next actions to be taken in optimising their imaging services.
MAIN POINTS
- Optimisation of radiological protection in diagnostic imaging and image-guided procedures requires provision of clinical images for individual patients that are of sufficient quality to ensure an accurate and reliable diagnosis, with radiation exposure minimised according to the applied imaging technology.
- In medical imaging, optimisation of protection is at two levels: (i) the design and construction of the equipment and the installation where it is used; and (ii) the day-to-day working procedures performed by the staff involved. Optimisation will only occur if all staff are properly trained in their roles, and equipment operation is assured through a comprehensive quality assurance programme, with ongoing review of performance that feeds into affirmation and development of protocols.
- Different aspects contribute to optimisation. These are: professionalism within optimization teams comprising radiologists, radiographers, and medical physicists, each using their unique sets of skills to improve imaging performance; methodology and technology coupled with the necessary expertise to evaluate performance; and organizational processes to manage quality improvement within a structured framework.
- Complex digital x-ray equipment allows dose levels to be reduced without compromising image quality. This requires high levels of knowledge and skill from imaging professionals, as if features are used incorrectly, patient doses can be unnecessarily high without this being apparent. All members of the imaging team must be given the necessary expertise through training, updated regularly, so they fully understand equipment operation.
- The degree to which an organisation has implemented optimisation will depend on the personnel, facilities, level of knowledge and experience available, and regulatory oversight. This publication sets out a layered approach to the development of optimization with broad categories for systems that might be expected to be in place to achieve different levels: Level D – preliminary; Level C – basic; Level B – intermediate; and Level A – advanced. The aim is to guide managers and staff in decisions about the next step to take in their programme of optimisation.
EXECUTIVE SUMMARY
(a) Optimisation is a key principle of radiological protection. Medical exposures make the largest contribution to the exposure of populations from artificial sources of ionising radiation worldwide, so optimisation of such exposures is particularly important. Optimisation of radiological protection for imaging requires radiation dose to be minimised in a manner that is consistent with providing the images/information required for the intended purpose. Digital radiology encompasses all radiological techniques that present images in digital form, for which the appearance can be manipulated to display the image in a form that best suits the purpose, and includes digital radiography, fluoroscopic techniques, and computed tomography. The emphasis on image quality has become crucial in digital radiology with more versatile image acquisition, post-processing, and presentation options. These techniques require a more rigorously defined optimisation process, awareness of underlying technical factors that are not always obvious, and comprehension of the impact of information technology on the displayed image. The clinical risk of patient mismanagement resulting from an examination for which the dose has been reduced to the point at which the image quality is insufficient to allow changes in diseased or damaged tissue to be characterised is likely to be high compared with any additional risk from a higher radiation exposure that gives sufficient image quality. However, cumulative radiation doses from the ever-increasing use of radiology may result in health consequences that, although not immediately apparent, could manifest at a later point in time. Thus, it is a question of balance between different types of risk (potential long-term effects from dose and more immediate clinical consequences), and achieving the correct balance is a challenging task from both technical and professional perspectives.
(b)To achieve successful optimisation, a facility must have sufficient imaging equipment, and enough staff who have been adequately trained in use of the equipment and the information technology features that are available. The optimisation process starts with specification of the equipment required to fulfil the clinical need, and continues through its purchase, installation, acceptance, and commissioning. It includes maintenance and the quality assurance programme which continue throughout the life cycle of the equipment. Optimisation then continues during clinical use of the equipment, with requirements for provision of necessary clinical information by those referring patients for examinations based on accepted guidelines, and appropriate processes for reporting and acting on results of imaging procedures.
(c) Optimisation requires the input of knowledge and skills on many different aspects of how radiological images are formed, and so requires contributions from different healthcare professionals working together as a team. A radiologist, other appropriately trained radiological medical practitioner, or radiographer can judge whether the image quality is sufficient for the diagnostic purpose. A radiographer should know the practical operation and limitations of the equipment and associated information technology, and have a basic knowledge of the physical principles of image formation and interpretation of measurements on images. A medical physicist should have a deeper understanding of the physical principles behind image formation, and be able to perform and interpret measurements of dose and image quality. In order to achieve optimisation, the three specialities, together with other healthcare professionals who will sometimes be involved, must have mutual respect for their individual skills and work together as a cohesive group (i.e. professionalism). Unfortunately, at the time of preparation of this publication, the levels of knowledge and skills in many countries are often inadequate to achieve good optimisation on more complex digital radiology systems due to lack of resources. Increasing technical and computational complexity in radiology equipment and applications underlines the importance of multi-professional collaboration and dependency on the combined knowledge of different professionals. Dedicated time must be made available for professionals to work together to meet emerging challenges in optimisation as applications of new equipment are developed.
(d) Digital imaging provides the potential for images to be obtained with lower exposures than previously possible using film screen combinations, enabling levels to be adapted to the diagnostic requirements of specific examinations. New techniques are continuously becoming available that can improve image quality and potentially enable diagnostic images to be obtained with lower patient doses. As an example, automated exposure control systems are continuously developed to be more effective in ensuring consistent image quality while reducing patient dose by adapting the radiation level to each procedure and the patient. However, all of these features introduce additional complexities and require settings to be chosen correctly for proper operation of software controls. If users do not deploy them effectively due to limited awareness of their mode of operation, the doses received by patients may not be optimal, but this will not be apparent to the user. Therefore, more complex equipment requires knowledgeable staff with more extensive training for its operation. Knowledge and skills, in combination with the instruments and test objects to evaluate the performance of the equipment, form the basis of optimisation (i.e. methodology).
(e) A key component of optimisation is keeping the radiation dose to the patient as low as reasonably practicable, while maintaining an adequate level of image quality and diagnostic information. At the basic level, this requires regular assessments of doses from groups of patients to determine the dose levels, and comparisons with diagnostic reference levels to confirm acceptability. Evolving technical optimisation features and quality management systems will enable extension of the optimisation process to individual patients and procedures based on clinical indication. Operators must have the knowledge and skills to use such features appropriately, and if they do not, important opportunities will be lost. Such an indication and patient-specific level of optimisation is applied routinely every day in radiology departments, and is a fundamental extension of the conventional optimisation principle (known as ‘as low as reasonably achievable’) as applied to patients. Indication orientation and patient specificity connect the optimisation process directly to the justification process, and enable them to be mutually supportive and comprehensive, forming a unitary process for radiological protection.
(f) Evaluation of image quality as part of quality assurance/quality control programmes typically involves evaluation of clinical images by an experienced radiologist, other appropriate radiological medical practitioner, or radiographer against established good image quality criteria, and objective analysis of phantom images by a medical physicist. Further net improvements could be gained in the future through automated image quality evaluation based directly on clinical patient images, and may involve artificial intelligence algorithms implemented directly into image archives or imaging modalities. Regardless of the present or future methodology, the process of measuring image quality involves many interdependent parameters and, due to this comprehensive nature, is a pivotal part of the overall assessment of performance. Results from evaluations of clinical image quality, coupled with results from patient dose and image quality measurements, feed into the development of examination protocols optimised for the clinical purpose. To ensure that optimisation processes are carried out consistently, management systems need to be in place to confirm that measurements and assessments are made, to ensure that available data from clinical use and performance measurements are used in making adjustments to protocols to address any deficiencies, and to monitor the progress that is made (i.e. process management).
(g) The degree to which any organisation has implemented optimisation in digital radiology will depend on the personnel, facilities, and level of knowledge and experience available. Within the aspects of professionalism, methodology, and process, there will be different levels of performance that radiology facilities will have achieved. This publication sets out broad categories for the systems that would be in place to achieve different levels of optimisation: Level D – preliminary; Level C – basic; Level B – intermediate; and Level A – advanced. It is hoped that evaluation of the arrangements that radiology facilities already have in place will provide a guide to decisions about what actions should be taken next to improve optimisation of their imaging service. It is also noted that these categories (Levels D, C, B, and A) with increasingly advanced optimisation methods also reflect the increasing capability to reach indication-oriented and patient-specific optimisation processes.
(h) There is a need for a cultural change in order to enable improvements and developments in optimisation methods, and to avoid key processes being overlooked. Optimisation will only be achieved through facilities investing in adequate staffing levels to operate their imaging equipment, and providing the appropriate training, together with continuing professional development opportunities for their staff. This begins at the stage of entry into medical imaging professions with sufficient courses for the education of trainees with opportunities to learn under the guidance of experienced practitioners. Knowledge and understanding are key to successful optimisation of radiological imaging. The cultural shift towards multi-professionalism required can only occur if the professional roles and competences are built to support this fundamental shift.
(i) This publication provides guidance on the adaptation of levels of dose and image quality to clinical tasks, taking advantage of the wide dynamic range offered by digital imaging equipment. Practical aspects that depend on specific x-ray image acquisition techniques are covered in a separate companion publication.
