ICRP Publication 121

Radiological Protection in Paediatric Diagnostic and Interventional Radiology

Recommended citation
ICRP, 2013. Radiological protection in paediatric diagnostic and interventional radiology. ICRP Publication 121. Ann. ICRP 42(2).

Authors on behalf of ICRP
P-L. Khong, H. Ringertz, V. Donoghue, D. Frush, M. Rehani, K. Appelgate, R. Sanchez

Abstract - Paediatric patients have a higher average risk of developing cancer compared with adults receiving the same dose. The longer life expectancy in children allows more time for any harmful effects of radiation to manifest, and developing organs and tissues are more sensitive to the effects of radiation. This publication aims to provide guiding principles of radiological protection for referring clinicians and clinical staff performing diagnostic imaging and interventional procedures for paediatric patients. It begins with a brief description of the basic concepts of radiological protection, followed by the general aspects of radiological protection, including principles of justification and optimisation. Guidelines and suggestions for radiological protection in specific modalities – radiography and fluoroscopy, interventional radiology, and computed tomography – are subsequently covered in depth. The report concludes with a summary and recommendations.

The importance of rigorous justification of radiological procedures is emphasised for every procedure involving ionising radiation, and the use of imaging modalities that are non-ionising should always be considered. The basic aim of optimisation of radiological protection is to adjust imaging parameters and institute protective measures such that the required image is obtained with the lowest possible dose of radiation, and that net benefit is maximised to maintain sufficient quality for diagnostic interpretation. Special consideration should be given to the availability of dose reduction measures when purchasing new imaging equipment for paediatric use. One of the unique aspects of paediatric imaging is with regards to the wide range in patient size (and weight), therefore requiring special attention to optimisation and modification of equipment, technique, and imaging parameters. Examples of good radiographic and fluoroscopic technique include attention to patient positioning, field size and adequate collimation, use of protective shielding, optimisation of exposure factors, use of pulsed fluoroscopy, limiting fluoroscopy time, etc. Major paediatric interventional procedures should be performed by experienced paediatric interventional operators, and a second, specific level of training in radiological protection is desirable (in some countries, this is mandatory). For computed tomography, dose reduction should be optimised by the adjustment of scan parameters (such as mA, kVp, and pitch) according to patient weight or age, region scanned, and study indication (e.g. images with greater noise should be accepted if they are of sufficient diagnostic quality). Other strategies include restricting multiphase examination protocols, avoiding overlapping of scan regions, and only scanning the area in question. Up-to-date dose reduction technology such as tube current modulation, organ-based dose modulation, auto kV technology, and iterative reconstruction should be utilised when appropriate.

It is anticipated that this publication will assist institutions in encouraging the standardisation of procedures, and that it may help increase awareness and ultimately improve practices for the benefit of patients.

© 2013 ICRP. Published by Elsevier Ltd.

Keywords: Justification; Optimisation; Paediatric patient; Radiological protection; Diagnostic radiology; Interventional radiology.

Key Points
Justification of every examination involving ionising radiation, followed by optimisation of radiological protection, is important in every patient, and especially in paediatric patients in view of the higher risk of adverse effects per unit of radiation dose compared with adults.

According to the justification principle, if a diagnostic imaging examination is indicated and justified, this implies that the risk to the patient of not doing the examination is greater than the risk of potential radiation-induced harm to the patient.

Imaging techniques that do not employ the use of ionising radiation should always be considered as a possible alternative.

Optimisation of radiological protection involves optimised functioning of radiological equipment and quality control, ensuring radiological equipment and technical parameters are adequately tailored for paediatric patients, and the implementation of DRLs to assist in the optimisation process.

Quality criteria implementation and regular audits should be instituted as part of the radiological protection culture in the institution.

Attention should be paid to good radiographic technique including positioning and immobilisation of paediatric patients, field size, and protective shielding. Radiographic exposure parameters should be specially tailored for patient size and age.

As most imaging equipment and vendor-specified protocols are structured for adults, modifications of equipment and exposure parameters may be necessary for paediatric use. Advice of medical physicists should be sought, if possible, to assist with installation, setting imaging protocols, and optimisation.

Interventional procedures should be performed by experienced paediatric interventional staff due to the potential for high patient radiation dose exposure, and additional training in radiological protection is recommended to protect both patients and staff.

For CT, dose reduction should be optimised by adjustment of scan parameters (mA, kVp, and pitch) according to patient weight or age, and weight-adapted CT protocols have been suggested and published. For the purpose of minimising radiation exposure, noisier images, if sufficient for radiological diagnosis, should be accepted. Optimised study quality also depends on region scanned and study indication. Other dose reduction strategies include restricting multiphase examination protocols, avoiding overlapping of scan regions, and only scanning the area in question. Furthermore, study quality may be improved by image postprocessing to facilitate radiological diagnoses and interpretation.

Executive Summary
(a) This publication aims to provide guiding principles to protect paediatric patients from radiation for referring clinicians and clinical staff performing diagnostic imaging and interventional procedures, highlighting the specific issues which may be unique to the imaging of children.

(b) It begins with a brief description of the basic concepts of radiological protection, followed by the general aspects of radiological protection, including principles of justification and optimisation. Guidelines and suggestions for radiological protection in specific modalities – radiography and fluoroscopy, interventional radiology, and computed tomography (CT) – are subsequently covered in depth. The final chapter concludes with a summary and recommendations.

(c) The importance of rigorous justification of radiological procedures is emphasised for every procedure involving ionising radiation, especially with regards to modalities that impart a relatively high radiation dose: CT and interventional procedures. The use of alternative imaging modalities that are non-ionising should always be considered.

(d) The basic aim of optimisation of radiological protection for diagnostic imaging and interventional procedures is to adjust imaging parameters and institute protective measures in such a way that the required image is obtained with the lowest possible dose of radiation, and net benefit is maximised.

(e) The optimisation of radiological equipment for paediatric use with the broadest range of settings to address the wide range in patient size (and weight) is necessary. As most imaging equipment and vendor-specified protocols are structured for adults, modifications of equipment and exposure parameters may be necessary for paediatric use. The advice of medical physicists should be sought, if possible, to assist with installation, setting imaging protocols, and optimisation. Special consideration should be given to the availability of dose reduction measures when purchasing new imaging equipment.

(f) The development and regular updating of local, regional, or national diagnostic reference levels (DRLs) to assist in the optimisation process is encouraged. Also, regular audits of referral criteria, imaging quality, and imaging technique should be implemented as part of the radiological protection culture.

(g) Good radiographic technique requires attention to patient positioning and immobilisation, accurate field size and correct x-ray beam limitation, the use of protective shielding, and optimisation of radiographic exposure factors (e.g. focal spot size, filtration, antiscatter grid characteristics and appropriate use, focus to image plane distance, and tube current–exposure time product).

(h) Dose reduction techniques in fluoroscopy include the use of pulsed fluoroscopy, keeping the fluoroscopy table as far as possible from the x-ray source and the image intensifier as close to the patient as possible, limiting fluoroscopy time and restricting fluoroscopy to the evaluation of moving targets alone, the use of virtual collimation for positioning prior to commencing fluoroscopy, tight collimation to the relevant anatomical area, and angling of the x-ray beam away from radiosensitive areas. Magnification should be kept to a minimum. Finally, radiation dose (air kerma–area product) should be recorded.

(i) Interventional procedures, particularly in small infants, should be performed by experienced interventional operators. All team members should undergo training in radiological protection, with a second, specific level of training required by some countries as this is a relatively high-dose procedure with the potential to impart high peak skin doses and absorbed doses to the exposed organs and tissues. The large size of the image intensifier relative to the size of the neonate, infant, or child, and the greater need for magnification compared with adults are factors that can potentially increase dose to the patient. Image acquisition runs should only be performed if necessary, and the fewest number of frames per second required to achieve the clinical objective should be used. Images should be obtained using tight collimation and the lowest magnification. Reduction of unnecessary dose, not only to the patient but also to the staff from exposure to scattered radiation, is important.

(j) For CT, dose reduction should be optimised by the adjustment of scan parameters (such as mAs, kVp, and pitch) according to patient weight or age, region scanned, and study indication (e.g. images with greater noise should be accepted if they are of sufficient diagnostic quality). Other strategies include restricting multiphase examination protocols, avoiding overlapping of scan regions, and only scanning the area in question. Attention should also be paid to minimising motion artefacts, meticulous use of intravenous contrast, and application of postprocessing techniques such as multiplanar and three-dimensional reconstruction as this can help improve study quality. Display monitors and the ambient environment should be optimised for the viewing of images. With regards to the use of local protective shielding, practices vary between institutions. Protocols should be tested specifically for each scanner as one approach is not appropriate for all scanners, and if not used properly, shielding may even increase radiation dose. If used, it is important to note that bismuth protection should only be placed after the scout view (or automatic exposure control prescanning) is performed, so that the system does not inappropriately increase tube current in the area of the shield. Shields should not be placed too close to the surface of the skin, and should be smoothly positioned over the surface to avoid artefacts. Finally, up-to-date dose reduction technology such as tube current modulation, organ-based dose modulation, auto kV technology, and iterative reconstruction should be used when appropriate.


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