Recommended citation
ICRP, 2018. Occupational radiological protection in interventional procedures. ICRP Publication 139. Ann. ICRP 47(2).

Authors on behalf of ICRP
P. Ortiz Lopez, L.T. Dauer, R. Loose, C.J. Martin, D.L. Miller, E. Vaño, M. Doruff, R. Padovani, G. Massera, C. Yoder

Abstract - In recent publications, such as Publications 117 and 120, the Commission provided practical advice for physicians and other healthcare personnel on measures to protect their patients and themselves during interventional procedures. These measures can only be effective if they are encompassed by a framework of radiological protection elements, and by the availability of professionals with responsibilities in radiological protection. This framework includes a radiological protection programme with a strategy for exposure monitoring, protective garments, education and training, and quality assurance of the programme implementation. Professionals with responsibilities in occupational radiological protection for interventional procedures include: medical physicists; radiological protection specialists; personnel working in dosimetry services; clinical applications support personnel from the suppliers and maintenance companies; staff engaged in training, standardisation of equipment, and procedures; staff responsible for occupational health; hospital administrators responsible for providing financial support; and professional bodies and regulators. This publication addresses these elements and these audiences, and provides advice on specific issues, such as assessment of effective dose from dosimeter readings when an apron is worn, estimation of exposure of the lens of the eye (with and without protective eyewear), extremity monitoring, selection and testing of protective garments, and auditing the interventional procedures when occupational doses are unusually high or low (the latter meaning that the dosimeter may not have been worn).

© 2018 ICRP. Published by SAGE.

Keywords: Occupational radiological protection; Interventional procedures; Exposure monitoring; Exposure of the lens of the eye; Protective garments.

AUTHORS ON BEHALF OF ICRP P. ORTIZ LÓPEZ, L.T. DAUER, R. LOOSE, C.J. MARTIN, D.L. MILLER, E. VAÑÓ, M. DORUFF, R. PADOVANI, G. MASSERA, C. YODER

Key Points: Not included in this publication

Executive Summary
1. Background

(a) Physicians in many medical and surgical specialties, assisted by nurses and radiographers (radiological technologists), perform interventions guided by radiological imaging as an alternative to conventional surgery. On average, these interventions are less invasive, their recovery periods are shorter, and – for many types of interventions – the complication rate is lower than for the equivalent conventional surgery. In addition, some patients who may not tolerate anaesthesia and conventional surgery, as well as lesions that were not previously accessible, can now be treated by less-invasive image-guided interventions.

(b) The number of interventions guided by imaging is increasing greatly in both developed and developing countries. New types of interventions are also of increased complexity, require extensive use of x-ray imaging, and raise new issues of occupational protection. As well as interventional radiologists and cardiologists, other specialists, usually with little or no training in radiological protection, are now users of interventional guidance.

(c) The considerable variation in occupational exposures observed for the same type of procedure suggests that radiological protection practices can be improved. Some recent ophthalmological studies described below, such as those performed under the coordination of the International Atomic Energy Agency (IAEA) programme, the Retrospective Evaluation of Lens Injuries and Dose (RELID study), have shown an increased incidence of radiation-related eye lens opacities in interventionalists when radiological protection devices were not used properly and radiological protection principles were not followed. 2. Purpose and scope of the publication

(d) In Publications 117 (ICRP, 2010a) and 120 (ICRP, 2013a), the Commission provided practical advice on occupational radiological protection for physicians and other healthcare personnel involved in interventional procedures. This publication provides guidance on exposure monitoring strategies, methods and options, radiological protection approaches and garments, their use and testing, the development of a radiological protection programme, education and training, and quality assurance of the programme implementation. The guidance is meant for medical physicists and other healthcare professionals in charge of occupational protection, personnel working in dosimetry services, clinical applications support personnel, regulators, and all those having an influence on the overall safety culture and on quality assurance and improvement. In addition, the guidance will be useful to those engaged in training, standardisation of equipment, and procedures; those with responsibilities for occupational health; hospital managers and administrators responsible for providing financial support for protection purposes; and professional bodies (interventionalists, medical physicists, nurses, and radiographers).

3. Uses of image-guided interventions, occupational exposures, and observed effects
3.1. Uses

(e) Interventions are usually guided by fluoroscopy, and radiographic cine-like series of images are taken to document both normal and abnormal conditions and the outcome of diagnosis or treatment. Interventions can also be guided by computed tomography (CT) imaging, with images taken while the interventionalist can step behind a mobile shield or out of the room, or by CT fluoroscopy, in which the interventionalist stays in the room when exposing the patient for obtaining images during device manipulation. The principal advantage of CT fluoroscopy over ordinary CT images is the real-time monitoring to access lesions that move within the body as a result of patient breathing or other motion. Its use allows interventions to be performed more rapidly and efficiently. On the other hand, CT fluoroscopy may result in relatively high radiation exposure to both the patient, the interventionalist, and other staff involved in the intervention.

(f) X-ray image-guided therapeutic interventions such as radioembolisation with 90Y-labelled microspheres [selective internal radiation therapy (SIRT)] are an alternative method to treat patients with unresectable primary or secondary liver tumours. Several hospitals are exploring the use of real-time positron emission tomography (PET)-CT guidance during interventional procedures, such as for biopsies and/or radiofrequency ablations. 18F-FDG PET-CT imaging is performed within the suite to identify where an embolisation or biopsy should be performed, to check on effectiveness of interventions, and for early detection of residual disease (e.g. after radiofrequency ablation, so that ablation can be repeated, if necessary, in order to obtain the maximum therapeutic benefit).

3.2. Occupational exposures and observed effects
(g) While, with the appropriate protection, it is possible for interventionalists to keep their annual occupational effective dose below 10 mSv, and typically within a range of 2–4 mSv or less, some surveys have shown that individual occupational doses may exceed these values and have considerable variation.

(h) The equivalent dose to the lens of the eye has received increased attention as evidence has become available that cataract development may have a much lower threshold for occurrence than was historically believed. The Commission’s recommendations have lowered the equivalent dose limit for the lens of the eye from 150 mSv year-1 to 20 mSv year-1, averaged over defined periods of 5 years with no single year exceeding 50 mSv. The nature of interventions guided by radiological imaging is such that, without protective measures for the eyes, personnel with a medium or high workload could receive doses to the lens of the eye that would exceed the new annual equivalent dose limit, and could result in eye lens opacities over time.

(i) Several ophthalmological studies were conducted on a sample of interventional cardiologists and nurses who were attending cardiology congresses and who participated voluntarily under the coordination of the IAEA programme, the RELID study. Approximately 40–50% of interventionists and 20–40% of technicians or nurses, were found to have posterior subcapsular opacities compatible with injuries derived from exposure to ionising radiation. The incidence rate in interventionists was four to five times higher than that in unexposed individuals in the control group (approximately 40–50% vs 10%). Lifetime lens absorbed doses were estimated to reach several Gy in some cases.

(j) Extremity equivalent dose may be of concern, as the dose to the interventionalist’s hand that is nearest to the irradiated patient volume can be high and requires specific hand monitoring. Values for annual lower extremity equivalent doses up to 110 mSv have been found, despite the use of a protective curtain hanging on the side of the treatment couch. This exposure is attributed to the gap between the protective curtain and the floor, the size of which is dependent on the height of the x-ray table during exposure.

4. Occupational exposure monitoring and exposure evaluation
(k) A survey performed within the IAEA Information System on Occupational Exposure in Medicine, Industry and Research (ISEMIR) (IAEA, 2014b) showed that 76% of interventional cardiologists stated that they always used their dosimeters and 45% used two dosimeters. This survey relied on self-reporting and may overestimate true dosimeter use. In addition, in some parts of the world, there is a lack of proper monitoring of radiation doses to professionals involved in interventional procedures, and individual dosimeters are often not worn regularly.

(l) In addition to assessing effective dose, occupational exposure monitoring in interventions guided by radiological imaging should include an estimate of the equivalent dose received by the lens of the eye and, in some cases, the extremities.

4.1. Assessment of effective dose
(m) The combination of the readings of two dosimeters, one shielded by the apron and one unshielded above the apron at collar level, provides the best-available estimate of effective dose (as has been stated by the Commission in previous publications). The dosimeter under the apron also provides evidence that an apron that provided sufficient shielding was worn regularly.

4.2. Assessment of equivalent dose to the eye
(n) The dosimeter over the apron, at collar level on the side of the interventionalist closer to the irradiated volume of the patient, not only contributes to assessing effective dose, but also provides a reasonable estimation of the equivalent dose to the lens of the eye and the head.

(o) Improved computational methodologies need to be developed to assess occupational doses, including equivalent dose to the lens of the eye, in high-dose procedures. These methods may be helpful to audit the regular and proper use of personal dosimeters and to assess the need for additional protection (e.g. protective glasses). Research programmes should pursue the development of computational technologies (not requiring dosimeters) together with personnel position sensing devices to assess personnel doses, including dose to the eye.

4.3. Equivalent dose to the extremities
(p) Assessment of equivalent dose to the hands in some specific complex interventional procedures needs more attention in the future. Finger dosimeters may be needed if the hand is very close to the direct x-ray beam. Similarly, assessment of exposure to the lower extremities, including the feet, will also require increased attention, especially when protective curtains are not available or there is a gap between the curtains and the floor. A gap may be present depending on the height of the table during the intervention.

4.4. Examples of errors with the use of dosimeters and indirect approaches to correct the situation
(q) Examples of errors include not using the assigned dosimeter, wearing a dosimeter over the apron that was intended for use under the apron, wearing a ring dosimeter on the incorrect hand, wearing a dosimeter assigned to another person, or losing a dosimeter.

(r) Indirect approaches to dose assessment may be useful in identifying a lack of compliance in wearing personal dosimeters, and also in estimating occupational doses when personal dosimeters have not been used. These approaches may be based on area dosimetry of the scatter radiation near the patient (e.g. at the C-arm), together with conversion coefficients from patient-related quantities such as kerma-area product for different types of procedures and geometries to the dose to the lens of the eye of workers.

5. Guidance on occupational radiological protection
5.1. Relationship between patient and staff exposure

(s) Occupational protection in interventions guided by radiological imaging is closely related to patient protection, and most actions to protect the patient also protect the staff. There are, however, additional measures and protective devices that protect the staff alone. The use of these devices should not interfere with the manipulations of the procedure, nor increase patient exposure.

5.2. Protection by shielding devices
(t) Shielding aprons should be worn by all interventional staff working inside the x-ray room. Aprons usually contain the equivalent of 0.25 mm, 0.35 mm, or 0.5 mm of lead. Some designs overlap at the front to provide protection of 0.5-mm lead equivalence, with 0.25-mm lead equivalence elsewhere. Transmission is typically between 0.5% and 5% in the range 70–100 kV (i.e. attenuation factor between 200 and 20). Aprons shield the trunk against scattered radiation, but parts of the body including the head, arms, hands, and legs are not protected by the apron. These parts of the body need to be considered in the radiological protection programme.

(u) The most important factor in protection of the head is the proper use of ceiling-suspended lead acrylic shields. They should always be included in interventional installations, as they can reduce doses to the whole head and neck by a factor of 2–10, depending on how efficiently they are positioned.

(v) Staff, such as nurses and anaesthesia personnel, who need to remain near the patient may benefit from the additional protection provided by movable (rolling) shields that can be positioned between them and the source of scattered radiation.

(w) As described in Point (h), under occupational exposure, the equivalent dose to the lens of the eye can exceed the new dose limit if protective measures are lacking. Over time, this could result in lens opacities. Conversely, if the interventional fluoroscopy equipment is operating correctly, procedure protocols have been optimised, the operator has been trained, and protective tools for the eyes are being used, the dose to the lens of the eye should be lower than the dose limit.

(x) A close fit of leaded glasses to the facial contours, particularly around the sides and underside of the glasses, is important because the clinician is looking at the image monitor during the x-ray exposures. As a result, the eyes may be irradiated from the side and below.

(y) Lead drapes attached to the bottom edge of the ceiling-suspended shield, as well as shielding drapes and pads, can be effective in protecting the hands in some procedures. This type of protection should be considered for procedures where the operator needs to be close to the source of scattered radiation (i.e. the irradiated volume of the patient). When placing disposable drapes on the patient, attention is required to avoid having the drapes in the primary beam, which might increase patient and operator exposure.

(z) Staff who stand near the patient table during interventions should be aware that the radiation field is more intense in the region adjacent to the beam entrance side. This is particularly important when projections are oblique or lateral. Doses to the head, upper body, and hands of the interventionalist from fluoroscopy with the tube positioned under the table will be substantially lower than the doses received by the lower extremities.

(aa) This is particularly true when no shielding curtains for the lower extremities are available, and when the table is at a higher position, so that the feet may stay unprotected even if the curtains are in place. Rolling lead shields, when available, decrease the effective dose to staff by more than 90% if used properly.

(bb) In summary, all staff in the room should wear protective aprons. Wraparound aprons are desirable for individuals who may not be able to face towards the patient at all times when the beam is on. The interventionalist should be protected by ceiling-suspended screens, table-suspended curtains, and shielding drapes when feasible. Staff can also reduce doses received during the use of high-dose acquisition modes (e.g. image acquisition series and digital subtraction angiography) and during injection of contrast media using an automatic injector by stepping back and increasing the distance to the patient. Staff, such as nurses and anaesthesia personnel, who need to remain near the patient can benefit from protection by movable screens. Other personnel should increase protection by increasing their distance from the irradiated volume of the patient or, if possible, leaving the room during image acquisition.

5.3. Protection of the embryo and fetus
(cc) After a pregnant woman has declared her pregnancy, her working conditions should ensure that the additional dose to the conceptus does not exceed 1 mSv during the remainder of the pregnancy.

(dd) Current data do not justify precluding pregnant woman from performing interventions guided by radiological imaging completely if they follow proper procedures. Pregnancy, in any case, requires that the employer carefully reviews the exposure conditions and other aspects of occupational hazards (e.g. back pain with use of lead aprons) of the pregnant worker.

6. Quality assurance
(ee) Quality assurance with regular documented checks to confirm that professionals involved in interventions guided by radiological imaging always wear their dosimeters and protective equipment, including eyewear, is very important.

(ff) Acceptance tests for protective devices are crucial; some supplies of defective protective clothes have been documented. In addition, handling protective devices with care (e.g. avoid folding) and regular testing are required as part of the quality assurance and improvement programme, as described in Section 5.

7. Education and training
(gg) Initial and continuing education and training of professionals in occupational safety and radiological protection is required. This is especially important regarding safety culture and the proper use of imaging equipment and radiological protection tools (e.g. ceiling-suspended shields and/or leaded eyewear and shielding curtains).

(hh) Use of real-time active dosimeters not only helps in optimising protection of specific high-dose procedures, but also contributes to the education of professionals on the level of doses being received.

(ii) In addition to knowledge of general radiological protection, hospital staff in charge of occupational protection, dosimetry services staff, clinical applications specialists from suppliers, and regulators need knowledge of clinical practice, the x-ray equipment used in interventions, strategies for occupational exposure assessment, the protection methods, and selection and testing of protective garments.

8. Availability of key professionals for radiological protection
(jj) The role of the medical physicists or others in charge of creating and maintaining a radiological protection and training programme is crucial. They are part of the team that ultimately designs and implements optimal radiological protection and care by the interventionalists, radiographers, and nurses.

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