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==More In-Depth Information==
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[[File:ICRPGuide.JPG|150px|thumb|right|link=Guide_to_Radiological_Protection_in_Healthcare_(demo)Guide_to_Radiological_Protection_in_Healthcare|Take me back to the ICRP's [[Guide_to_Radiological_Protection_in_Healthcare_(demo)Guide_to_Radiological_Protection_in_Healthcare|Guide to Radiological Protection in Healthcare]]!]]
The primary aim of radiological protection is to provide an appropriate standard of protection for people and the environment without unduly limiting the beneficial practices giving rise to radiation exposure. [[ICRP Publication 103]]<ref name="Pub103">[[ICRP Publication 103]] The 2007 Recommendations of the International Commission on Radiological Protection. Ann. ICRP 37(2-4), 2007.</ref> has formulated a set of fundamental principles of radiological protection that apply to radiation sources and to the individuals being exposed. These principles are applicable to radiological protection in medicine. ICRP has provided recommendations for protection in medicine through [[ICRP Publication 105]] Radiological Protection in Medicine<ref name="Pub105">[[ICRP Publication 105]] Radiological Protection in Medicine. Ann. ICRP 37(6), 2007.</ref>, [[ICRP Supporting Guidance 2]] Radiation and your patient - A Guide for Medical Practitioners<ref name="SG002">[[ICRP Supporting Guidance 2]] Radiation and Your Patient A Guide for Medical Practitioners. Ann. ICRP 31(4), 2001.</ref> and [[ICRP Publication 73]] Radiological Protection and Safety in Medicine<ref name="Pub073">[[ICRP Publication 73]] Radiological Protection and Safety in Medicine. Ann. ICRP 26(2), 1996.</ref>.
==Radiation health effects==
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Radiation exposure can lead to either tissue reactions or stochastic effects.<ref name="Pub103"/> Tissue reactions<ref name="Pub118">[[ICRP Publication 118]] ICRP Statement on Tissue Reactions and Early and Late Effects of Radiation in Normal Tissues and Organs. Ann. ICRP 41(1-2), 2012.</ref> can occur in the application of ionizing radiation in radiation therapy, and in interventional procedures, particularly when fluoroscopically guided interventional procedures are complex and require longer fluoroscopy time or acquisition of numerous images. Tissue reactions occur when many cells in an organ or tissue are killed, the effect will only be clinically observable if the radiation dose is above some threshold. The magnitude of this threshold will depend on the dose rate (i.e. dose per unit time) and linear energy transfer of the radiation, the organ or tissue irradiated, the volume of the irradiated part of the organ or tissue, and the clinical effect of interest.
The optimisation of radiological protection for patients in medicine is usually applied at two levels: (1) the design, appropriate selection, and construction of equipment and installations; and (2) the day-to-day methods of working (i.e. the working procedures). The basic aim of this optimisation of protection is to adjust the protection measures for a source of radiation in such a way that the net benefit is maximised. The optimisation of radiological protection means keeping the doses ‘as low as reasonably achievable, economic and societal factors being taken into account’, and is best described as management of the radiation dose to the patient to be commensurate with the medical purpose.
In optimisation of protection of the patient in diagnostic procedures, such as [[Application_of_ionising_radiation_in_healthcare#Diagnostic_Radiology|diagnostic radiology]] and [[Interventional Application_of_ionising_radiation_in_healthcare#Interventional_Procedures|interventional procedures]], again the same person gets the benefit and suffers the risk, and again individual restrictions on patient dose could be counterproductive to the medical purpose of the procedure. Therefore, source-related individual dose constraints are not relevant. Instead, [[diagnostic reference levels]] (DRLs)<ref name="Pub135">[[ICRP Publication 135]] Diagnostic Reference Levels in Medical Imaging. Ann. ICRP 46(1), 2017.</ref> for a particular procedure, which apply to groups of similar patients rather than individuals, are used to ensure that doses do not deviate significantly from those achieved at peer departments for that procedure unless there is a known, relevant, and acceptable reason for the deviation. This is in contrast to the Commission’s usual balancing of utilitarian protection policies based on collective doses against deontological safeguards using dose constraints for the individual. The policy for radiological protection in medicine is that the radiation exposure be commensurate with the medical purpose.
In radiation therapy, the aim is to eradicate the neoplastic target tissue or to palliate the patient’s symptoms. Some tissue reactions to surrounding tissue and some risk of stochastic effects in exposed non-target tissues are inevitable, but the goal of all radiation therapy is to optimise the relationship between the probability of tumour control and normal tissue complications. It is necessary to differentiate between the dose to the target tissue and the dose to other parts of the body. If the dose to the target tissue is too low, the therapy will be ineffective. The exposures will not have been justified and the optimisation of protection does not arise. However, the protection of tissues outside the target volume is an integral part of dose planning, which can be regarded as including the same aims as the optimisation of protection.
Medical exposures of patients have been properly justified and that the associated doses are commensurate with the medical purpose, so it is not appropriate to apply dose limits or dose constraints to the medical exposure of patients; such limits or constraints would often do more harm than good.<ref name="Pub105"/> Often, there are concurrent chronic, severe, or even life-threatening medical conditions that are more critical than the radiation exposure itself. The emphasis is then on justification of the medical procedures and on the optimisation of radiological protection.<ref name="SG002"/>
In most situations in healthcare, other than radiation therapy, it is not necessary to approach the thresholds for tissue reactions, even for the most part in fluoroscopically guided [[Application_of_ionising_radiation_in_healthcare#Interventional_Procedures|interventional procedures]], if the staff are properly educated and trained. The Commission’s policy is therefore to limit exposures so as to keep doses below these thresholds. The possibility of stochastic effects cannot be eliminated totally, so the policy is to avoid unnecessary sources of exposure and to take all reasonable steps to reduce the doses from those sources of exposure that are necessary or cannot be avoided.
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===Protecting pregnant patients===
{{#evt:service=youtube|id=https://youtu.be/2gQbR4gVXM8|dimensions=500|container=frame|alignment=right|description=Video courtesy of the International Atomic Energy Agency}}
Early pregnancy can go undetected, so it is prudent to ensure that patients of childbearing potential are not pregnant before undergoing [[Application_of_ionising_radiation_in_healthcare#Diagnostic_Radiology|diagnostic radiology]] or [[Application_of_ionising_radiation_in_healthcare#Nuclear_Medicine|nuclear medicine]] studies that provides doses above which the risk of adverse fetal health effects is not considered negligible (1–10 mGy).<ref>PRACTICE PARAMETER FOR IMAGING PREGNANT OR POTENTIALLY PREGNANT ADOLESCENTS AND WOMEN WITH IONIZING RADIATION[https://www.acr.org/-/media/ACR/Files/Practice-Parameters/Pregnant-Pts.pdf]</ref> Before [[Radiation Application_of_ionising_radiation_in_healthcare#Radiation_Therapy|radiation therapy]], and in the absence of a documented history of applicable gynaecological surgery (e.g. tubal ligation, hysterectomy) or an established postmenopausal state, serum or urine pregnancy tests should be obtained, ideally 24–72 h prior to treatment.<ref>The SNMMI Practice Guideline for Therapy of Thyroid Disease with 131I[http://jnm.snmjournals.org/content/53/10/1633]</ref>
There are radiation-related risks to the embryo/fetus during pregnancy that are related to the stage of pregnancy and the absorbed dose to the embryo/fetus. [[ICRP]] has evaluated the effects of prenatal irradiation in detail.<ref name="Pub090">[[ICRP Publication 90]] Biological Effects after Prenatal Irradiation (Embryo and Fetus). Ann. ICRP 33(1-2), 2003.</ref> These effects include lethal effects, malformations, central nervous system effects, leukaemia and childhood cancer. Consideration of these effects is important when pregnant patients undergo [[Application_of_ionising_radiation_in_healthcare#Diagnostic_Radiology|diagnostic radiology]], [[Application_of_ionising_radiation_in_healthcare#Interventional_Procedures|interventional procedures]], or [[Application_of_ionising_radiation_in_healthcare#Radiation_Therapy|radiation therapy]] using ionising radiation. A balance must be attained between the health care of the patient and the potential for detrimental health effects to the embryo/fetus that accompanies the specific radiological procedure.<ref name="Pub084">[[ICRP Publication 84]]Pregnancy and Medical Radiation. Ann, ICRP 30(1), 2000.</ref>
====Pregnant Patients Undergoing Diagnostic Radiology====
For [[Application_of_ionising_radiation_in_healthcare#Diagnostic_Radiology|diagnostic radiology]], referring physicians should have discussions with imaging specialists to help determine the best tests for their pregnant patients, taking into account non-ionising diagnostic imaging modalities, such as ultrasound or magnetic resonance imaging. If these modalities are not the most appropriate test based on the clinical scenario, or are not available, the most appropriate ionising radiation imaging modality should be utilised in such a way as to achieve the diagnosis required while keeping fetal and maternal doses as low as reasonably possible. Almost always, if a [[Application_of_ionising_radiation_in_healthcare#Diagnostic_Radiology|diagnostic radiology]] examination is medically indicated, the risk to the mother of not performing the procedure is greater than the risk of potential harm to the embryo/fetus.
If the examinations are justified and their performance is optimised, they should not be withheld from pregnant patients. Fetal dose reduction measures will vary depending on the specific test being administered, but may include reducing the dose of injected radiopharmaceutical, limiting the number of images performed, beam collimation, patient shielding, and ensuring that the maternal pelvis (and fetus) is not in the beam path during fluoroscopic procedures unless it is absolutely necessary.
====Pregnant Patients Undergoing Radiation Therapy====
[[Application_of_ionising_radiation_in_healthcare#Radiation_Therapy|Radiation therapy]] (whether with external beam, brachytherapy, or nuclear medicine) can involve high radiation doses and may cause harm to the fetus. The risk to the fetus is dependent on the stage of fetal development. Lethal risk occurs in the pre-implantation phase, malformation occurs during major fetal organogenesis 3–7 weeks post implantation, mental retardation occurs at 8–15 weeks post implantation, and future cancer risk follows a stochastic model. Although there is variability in threshold radiation doses, it can be generalised that risks become notable at fetal doses of 100 mGy (10 rad) or above. So, it is essential to ascertain whether a female patient is pregnant prior to [[Application_of_ionising_radiation_in_healthcare#Radiation_Therapy|radiation therapy]]. In pregnant patients, cancers that are remote from the pelvis can usually be treated with radiation therapy. However, this requires careful planning. Cancers in the pelvis cannot be treated adequately during pregnancy without severe or lethal consequences for the embryo/fetus. [[Application_of_ionising_radiation_in_healthcare#Radiation_Therapy|radiation therapy]] in pregnant patients requires pre-therapy fetal dosimetry estimation followed by a comprehensive discussion of the benefits and risks of the procedure, with the patient included as part of the informed consent process.
It should also be noted that <sup>131</sup>I used for diagnostic or therapeutic purposes and <sup>32</sup>P used for therapeutic purposes, should be avoided in pregnant patients because iodine and phosphor can cross the placental barrier readily. The fetal thyroid is sufficiently mature to concentrate iodine at approximately 10 weeks post implantation, and there is a risk of causing fetal hypothyroidism.<ref name="Pub084"/> As a rule, a pregnant patient should not be treated with a radioactive substance unless the radionuclide therapy is required to save her life: in that extremely rare event, the potential absorbed dose and risk to the fetus should be estimated and conveyed to the patient and the referring Physician. Considerations may include terminating the pregnancy.<ref name="Pub084"/>
Children are more sensitive to radiation exposure than adults. Depending on their age, organ, and tumour type, children are reported to be, on average, two to three times more sensitive to radiation than adults, and the younger the infants or children, the more radiosensitive they are at high doses. So, the potential risks of ionising radiation in paediatric patients need to be considered. Physicians should exercise caution when using ionising radiation to image or treat children. In nuclear medicine, a lower administered activity than that would be used for an adult may be used; acceptable images could still be obtained as the size of a child is typically smaller than that of an adult.
For [[Application_of_ionising_radiation_in_healthcare#Diagnostic_Radiology|diagnostic radiology]], the following should be taken into consideration: (1) select the most optimised imaging protocol based on the patient’s age and size; (2) repeat imaging, or phases (e.g. CT), need to be justified relative to the importance of the additional information being gained vs the additional radiation dose; and (3) only image the indicated area. [[ICRP Publication 121]] Radiological Protection in Paediatric Diagnostic and Interventional Radiology<ref name="Pub121"/> and [https://www.imagegently.org Image Gently] provide more details. It is worthwhile to note that where applicable, non-ionizing radiation imaging modalities may be considered.
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==Radiological protection of family members, carers and the public==
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[[file:AdobeStock_134802984_PreviewAdobeStock_134802984.jpegjpg|400px|thumb]]When a patient is exposed to external sources of radiation during [[Application_of_ionising_radiation_in_healthcare#Diagonstic_Therapy|diagnostic radiology]] or [[Application_of_ionising_radiation_in_healthcare#Radiation_Therapy|radiation therapy]], there is no residual radiation in the patient after the procedure, and they pose no radiation risk to people around them. However, when [[Application_of_ionising_radiation_in_healthcare#Nuclear_Medicine|nuclear medicine]] is used for diagnostic radiology or radiation therapy, protection of family members or the others who provide care to the patient, and the protection of the public the patient may come into contact, should be considered.<ref name="Pub094">[[ICRP Publication 94]] Release of patients after therapy with unsealed radionuclides. Ann. ICRP 34(2), 2004.</ref><ref name="Pub105"/>
For diagnostic nuclear medicine procedures (e.g. bone or myocardial perfusion scans), where the source of radiation is inside the body, radiopharmaceuticals retained in these patients emit radiation but the level of radiation is sufficiently low that these patients do not pose a radiation risk to those around them. These patients are generally discharged immediately after the procedure and instructed that they can carry on their normal daily activities.
For specific therapeutic [[Application_of_ionising_radiation_in_healthcare#Nuclear_Medicine|nuclear medicine]] (e.g. unsealed source therapy) or radiation oncology (e.g. brachytherapy) procedures, such as <sup>131</sup>I therapy for thyroid cancer or some forms of hyperthyroidism, the patient has significant amounts of residual radioactivity in their body that they may pose a slight risk to the others. Thus, radiation safety counselling is required to reduce the exposure of other individuals. Depending on the quantity of radionuclide, the treatment facility may need to hold (e.g. admit) the patient until the quantity is sufficiently reduced through a combination of radioactive decay and biological elimination. In addition, these patients are generally given radiation protection instructions, such as avoiding prolonged close contact with children or pregnant women for a specific period of time post therapy. The radiation safety advice will depend on the burden of underlying disease being treated and the treatment dose of <sup>131</sup>I administered.
Radiation safety advice related to implanted therapeutic sources (e.g. brachytherapy) will vary based on the specific radioactive source used. For some sources, such as <sup>125</sup>I used for prostate cancer, present very low risk to others. For other sources, such as <sup>192</sup>Ir, there may be a radiation risk to others and these patients are usually hospitalised with restricted close contact to others until the source is removed.
Exposure to family members or the others who provide care to the patient is defined as medical exposures as there is direct benefits to them, but dose constraints should be established for use in defining the protection policy for visitors to patient and family members at home when a nuclear medicine patient is discharged from hospital. Such groups may include children. ICRP has not previously recommended values for such constraints, but a value of 5 mSv per episode for an adult (i.e. for the duration of a given release of a patient after therapy) is reasonable.<ref>Radiation Dose Limits for Individual Members of the Public[https://www.nrc.gov/reading-rm/doc-collections/cfr/part020/part020-1301.html]</ref> The constraint needs to be used flexibly. For example, higher doses may well be appropriate for the parents of very sick children or for an elderly who would like to take care of his/her sick spouse. Young children, infants, and visitors not engaged in direct comforting or care should be treated as members of the public, who are subject to the public dose limit of 1 mSv/year.
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===Breastfed babies===
In nuclear medicine, varying amounts of radiopharmaceuticals are retained in the patients for varying periods of time. Also, some radiopharmaceuticals can be transferred to breast milk and passed from mother to child during breast feeding. As a result, both the mother, and her breast milk, can be a source of radiation to the baby. Non-urgent tests should be postponed until the breastfeeding period is completed.<ref>Radiation Protection of Patients[https://www.iaea.org/resources/rpop]</ref>
==Radiological protection of healthcare staff==
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[[file:AdobeStock_167496818_PreviewAdobeStock_167496818.jpegjpg|400px|thumb]]The principles for the protection of workers from ionising radiation are discussed fully in [[ICRP Publication 75]] General Principles for the Radiation Protection of Workers.<ref name="Pub075">[[ICRP Publication 75]] General Principles for the Radiation Protection of Workers. Ann. ICRP 27(1), 1997.</ref> These principles apply to healthcare staff working in [[Application_of_ionising_radiation_in_healthcare#Diagnostic_Radiology|diagnostic radiology]], [[Application_of_ionising_radiation_in_healthcare#Interventional_Procedures|interventional procedures]], [[Application_of_ionising_radiation_in_healthcare#Nuclear_Medicine|nuclear medicine]], and [[Application_of_ionising_radiation_in_healthcare#Radiation_Therapy|radiation therapy]] facilities.<ref name="Pub105"/> ICRP has recently published recommendations on occupational radiological protection in interventional procedures.<ref name="Pub139">[[ICRP Publication 139]] Occupational Radiological Protection in Interventional Procedures. Ann. ICRP 47(2), 2018-1.</ref>
The control of occupational radiological exposure in healthcare can be simplified and made more effective by the designation of workplaces into two types: controlled areas and supervised areas. In a controlled area, normal working conditions, including the possible occurrence of minor mishaps, require workers to follow well-established procedures and practices aimed specifically at controlling radiation exposures. A supervised area is one in which the working conditions are kept under review, but special procedures are not normally needed.
Individual monitoring for external radiation is simple and does not require a heavy commitment of resources. In medicine, it should be used for all those who work in controlled areas.
In several areas of healthcare, the control of occupational exposure is of particular importance, including nursing of brachytherapy patients when the sources have been implanted, palpation of patients during procedures utilising fluoroscopy, fluoroscopically guided [[Interventional Application_of_ionising_radiation_in_healthcare#Interventional_Procedures|interventional procedures]] such as in heart catheterisation, or radiopharmaceutical preparation by staff in [[Application_of_ionising_radiation_in_healthcare#Nuclear_Medicine|nuclear medicine]]. In all these procedures, careful shielding and time limits are needed. Individual monitoring with careful scrutiny of the results is also important. In brachytherapy, frequent and careful accounting of sources is essential.
===Protecting pregnant workers===
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[[File:ICRPGuide.JPG|50px|link=Guide_to_Radiological_Protection_in_Healthcare_(demo)Guide_to_Radiological_Protection_in_Healthcare]]Take me back to the ICRP's [[Guide_to_Radiological_Protection_in_Healthcare_(demo)Guide_to_Radiological_Protection_in_Healthcare|Guide to Radiological Protection in Healthcare]]!
==References==
