The patient was counselled regarding treatment options.
Radiation Protection and Dosimetry in PET and PET/CT
The possible adverse effects of the radiation on her baby, and their mitigation, were explained. A four-vessel cerebral angiogram was performed on the patient, and a left paraclinoid aneurysm, which appeared to be superiorly projecting, was demonstrated Figure 1. It was recommended that the patient undergo an endovascular stent-assisted repair, as open surgery would pose a high risk to the unborn.
The multi-lobulated dome made rupture likely and allowing the pregnancy to continue without the treatment of the aneurysm could have serious consequences. Before the procedure, a medical physicist was consulted to determine the radiation protection measures required to protect the foetus. A lead apron, with 0. This was used as a precautionary measure to ensure that the dose, from sources external to the patient, to the foetus, is negligible. Internal scatter cannot be modified, and as the radiation is to the head in this case, internal scatter is assumed to be minimal at the fluoroscopic energies used.
Ultrasound-guided puncture was made in the right femoral artery, and a 6F sheath set was placed. Via exchange, a 6-F-guiding catheter was placed in the left ICA after which a micro-catheter was placed passing the aneurysm to the middle of the cerebral artery. A second micro-catheter was then placed in the aneurysm. Via the second micro-catheter, the aneurysm was then successfully embolised with seven detachable coils. The control angiogram demonstrated no aneurysmal flow, and all vessels were patent Figure 2. The stent was detached, and the catheters and guide catheter were removed.
The sheath was left in place and removed when clotting was normalised. Foetal radiation exposure was limited by using fluoro roadmaps, minimal angiogram exposures, pulsed fluoroscopy and shielding the abdomen.
ECR / A / B. Radiation risks for patients and staff - EPOS™
The exposure parameters and dose area product DAP values were recorded Table 1. DAP meters are widely used in interventional X-ray units, however, the radiation hazard cannot readily be obtained from the DAP value. Kisielewicz et al. Using this relationship, the patient ESD, after the four-vessel angiogram, was The ESD values calculated the approximate entrance dose. The software calculated the total uterine dose, which was used as a surrogate for dose to the foetus as being at the background level.
Allowing the pregnancy to continue without aneurysm repair could have had serious short-term consequences — thus, the procedure was justified. For optimisation, clinical purpose should be achieved with a minimal radiation dose delivered to the foetus. The dosimeter confirmed that the doses measured were indeed minimal. According to the ICRP, prenatal doses from most diagnostic procedures conducted properly will not cause any adverse effects to the foetus. Dose-dependent exposure risk depends on gestational age, being maximal during organogenesis and the early foetal period.
This case report demonstrates that radiation protection measures can be successfully employed for pregnant patients requiring head and neck interventional procedures, and it was used to educate and reassure the interventional team. Adequate shielding of the abdomen and good technique gave the team confidence that there would be a negligible dose to the foetus, well below the threshold values for increased risk. The authors thank the staff of the Clinical Imaging Sciences Department, School of Medicine, University of the Free State, for assistance in obtaining information regarding the procedure.
They also thank Ms. Mulder, medical editor, School of Medicine, University of the Free State, for technical and editorial preparation of the manuscript. She collected, processed and analysed the data and was the primary author of this document. The early development of life is a time when rapid cell division and differentiation are occurring. Similar to what was shown in Table 1, deterministic effects below an absorbed dose of 0. Pre-natal radiation exposures resulted in an increased cancer rate in the offspring of the survivors of the atomic bombings in Hiroshima and Nagasaki.
In other epidemiological studies, there have also been good statistical results that demonstrate an increased cancer rate in children following pre-natal radiation exposure from diagnostic radiology studies.
Unfortunately, these epidemiological studies do not provide very good data on the specific absorbed dose received to the fetus or embryo. This limits the ability to accurately characterize the dose vs. In the context of dose quantities relevant to the topic of radiation risk, two types of quantities are of importance: dose limits and reference levels. Dose limits refer to the maximum level of dose that the general public can receive from a source other than natural background radiation levels and those received by occupational workers in their job.
A.2. Stochastic Effects (Genetic Changes and Cancer)
The reference levels reflect the typical dose values expected in the majority of imaging studies. Both quantities can be described in terms of a number of dose-related metrics, including absorbed dose, effective dose, exposure, or any modality-specific dose index e. Limits for exposure to radiation should be at a level below the threshold where deterministic effects occur, i.
Furthermore, the limit should exclude exposures from background radiation. Because radiation is around us all of the time from the sun and naturally occurring sources, it would not make sense to try to limit radiation exposure below natural background levels. Using the threshold dose as a starting point, dose limits are determined using the Principles of Justification and Optimization.
It is important to understand that dose limits are not levels of exposure that should be considered acceptable in an occupation or that can be safely received by the general public. They are rather maximum limits consistent with the current state of medical practice. In most states, the ALARA concept requires investigation into dose-reduction methods even if only a fraction of the limit is received by any individual. The risk and benefit from medical exposures are received by the same individual. Yet an average radiation exposure level received from a diagnostic or interventional procedure can be used to evaluate whether the dose being used for a procedure is within an acceptable range based on existing practice norms.
These exposure levels are called reference levels and they are exam-specific.
Reference levels for medical exposures are usually set for an average-size patient at the upper levels 75th percentile seen in normal practice. The typical operational dose for the majority of exams is expected to be below these values. To make meaningful comparisons, aggregate facility data from average size patients should be compared against benchmark DRLs. If the DRL is exceeded, the protocol should be reviewed to determine methods to reduce the exposure for that exam type at the institution.
There are a number of sources for reference level values. Tables 6 — 9 give a sample of the Relative Radiation Level and the range of effective dose values reported for specific diagnostic and interventional radiology examinations. These values are for an average adult patient using typical equipment and techniques. The average effective dose in all of these exams is below mSv i. But the potential for stochastic effects must always be considered when an examination is planned. With an understanding of the effects of radiation and the doses for standard examinations, a physician possibly with the help of a radiologist can make a determination of which examination provides the most benefit to the patient at the lowest possible dose.
To do this, the physician needs consider the following criteria:. In general, the use of non-radiation tests should be considered before using radiation, and less invasive procedures should be considered before more invasive techniques are chosen. The ACR has organized several expert panels to develop criteria for determining appropriate imaging examinations for specific medical conditions. For example, Table 10 shows the Appropriateness Criteria for diagnosing abdominal pain and fever in an adult patient.
Table 11 shows an alternate set of criteria if the patient is pregnant. For example, it is known that some inherited syndromes e. In addition, these criteria assume all equipment options are available at the site. It also addresses what the patient may experience and how to prepare for the exams. The website contains over radiologic procedures and is updated frequently with new information.
Improved awareness and recommendations for imaging pediatric patients has also been initiated by the Image Gently Alliance. This initiative is called the Image Gently campaign. When a risk has a benefit to an individual or to society the risk may be justified with respect to the benefit. But how can both the risks and the benefits be explained? This requires knowledge of how people perceive risk and how to communicate the risk and the benefit to different populations. Medical environments are full of technical jargon that the public and even some personnel within different medical professions cannot understand or interpret correctly.
Technical information must be conveyed in simple, clear terms. In addition, care must be taken to emphasize important ideas so that they do not get lost in the discussion. In general the following principles should be used when trying to convey technical information to the public:. Risk communication differs from risk education. When attempting to discuss risk, experts need to understand the value systems of the people they are addressing. This requires an understanding of how different groups may interpret risk. Individual risk vs population risk Risk magnitudes and estimates, radiation related or otherwise, are developed based on population statistics.
When communicating risk to a patient, we are ascribing the population-base likelihood of harm to an individual, not a population. In this manner, risk is fundamentally a stochastic construct. Without understanding this statistical nature of risk estimates, people tend to use a deterministic interpretation of risk. This often can cause a false understanding of what the risk actually is, especially when compared to other activities or procedures.
Risk ranking Differences between how scientists and non-scientists rank risk is one of the major problems of risk communication. In general, if scientists and non-scientists are asked to rank a series of health risks the rank orders of the lists are considerably different. The top 10 risky activities are highlighted. At best, there is a correlation coefficient of 0.
At the time this study was conducted, x-ray exposure was ranked 24th by the experts and 17th or 22nd by the other groups. It is clear that different groups will assess risk differently; therefore, we, as the experts, need to understand and address these differences in order to communicate risks and benefits effectively. Objective Risks Vs. Subjective Risks There are two basic translations of how risk is interpreted. These are objective in structure, such as how the scientific community normally interprets risk, and subjective in nature, which is often used by the general public.
Objective assessment of risk is what we have done in this document and is based upon peer-reviewed scientific analysis of risks. Yet, the general public may be getting their risk assessment information from less technical sources such as non-peer-reviewed publications and journals newspapers, magazines, etc. Wikipedia , non-documentary-based television shows e. In addition, unlike scientific analysis, the public is unlikely to recall where a fact was presented to them; for instance, they may not be able to recall whether the National Enquirer or the proceedings of the National Academy of Sciences presented the fact.
As a result, equal weight may be given to data presented by any source. The methods to do this are educational and motivational rather than scientific. Furthermore, in medical situations, the patient and their family or friends are often confused and under high stress. In these situations, several things need to be considered:. In risk perception theory, perception equals reality. This means there may be no correlation between public perceptions of risk and scientific or technical information.
Therefore, discussions of risk should include a sensibility of the likely perception as well as the actual risk. Often you will read risks compared for unrelated situations. For example, in Table 14 the odds of dying from accidental death are shown.
Note the lifetime odds of dying from an injury for a person born in were 1 in 22 i. This suggests the odds of dying from accidental causes are similar to getting cancer at a later time from an exposure of 1 Sv see Table 2. The latency is a factor that weights heavily on the risk perception and as such, equal risk factors of different timescale cannot be directly compared. Furthermore, an accidental injury cannot be related to a decision about a medical procedure where the risk of not performing it would have its own associated risk. Herein lies one of the main challenges in communicating risk associated with medical exposures.
The exposure involves a finite stochastic risk with a very long latency period but not doing the procedure would have another risk with possibly a much shorter time horizon. If the issue is primarily communicating the risk of medical radiation alone, a good approach would be to give the risk of exposure to radiation in a radiology exam as an equivalent amount of exposure to the natural background radiation. This is shown in Table Other comparisons that might be acceptable would be with the estimated risk from cancer induction from naturally occurring or human-induced carcinogens, i.
It would be difficult to address all the benefits that are associated with the utilization of radiation in our everyday lives, including its use in medicine. Suffice it to say that radiation is extremely beneficial in many aspects of life when used appropriately. With respect to the use of radiation for diagnosis, assistance in medical interventional procedures, and therapy, the benefits need to be weighed relative to the potential risks. As we have discussed the risk of radiation induced effects are not well understood at the levels of radiation used for diagnostic and interventional procedures.
But there are clearly risks associated with not performing an exam that should also be considered. There are many organizations and advisory groups that monitor and assess radiation use and the risks associated with this use. These sources should be considered when developing teaching material or when determining whether radiation information being presented is valid. A brief description of each of these organizations based on their mission statement is given below. American Association of Physicists in Medicine AAPM Association involved in the advancement of the practice of physics in medicine and biology by encouraging innovative research and development, disseminating scientific and technical information, fostering the education and professional development of medical physicists, and promoting the highest quality medical services for patients.
American College of Radiology ACR A professional society involved in maximizing the value of radiology, radiation oncology, interventional radiology, nuclear medicine, and medical physics by advancing the science of radiology, improving the quality of patient care, positively influencing the socio-economics of the practice of radiology, providing continuing education for radiology and allied health professions, and conducting research for the future of radiology. Conference of Radiation Control Program Directors CRCPD A non-profit professional organization dedicated to radiation protection and the consistent promotion of methods to resolve radiation protection issues, to encourage high standards of quality in radiation protection programs, and to provide leadership in radiation safety and education.
International Commission on Radiation Protection ICRP An independent registered charity established to advance for the public benefit the science of radiological protection, in particular by providing recommendations and guidance on all aspects of protection against ionizing radiation.
Congress to collect, analyze, develop, and disseminate in the public interest information and recommendations about protection against radiation and radiation measurements, quantities and units, particularly those concerned with radiation protection. Radiological Society of North America RSNA A professional society involved in promoting and developing the highest standards of radiology and related sciences through education and research. The Society seeks to provide radiologists and allied health scientists with educational programs and materials of the highest quality, and to constantly improve the content and value of these educational activities.
See www. Image Gently campaign Alliance of organizations and people with a goal to change the practice of imaging children through increasing awareness of the opportunities to lower radiation dose in imaging. Food and Drug Administration FDA that provides independent, professional expertise and technical assistance on the development, safety and effectiveness, and regulation of medical devices and electronic products that produce radiation. Radiation Biology Review Ionizing radiation can cause tissue damage.
Figure 1. Radiation — Deterministic and Stochastic Effects A. Deterministic Effects Cell Death Cells are dying all of the time in the body from physical, chemical and other causes i. Stochastic Effects Genetic Changes and Cancer Stochastic effects are random or probabilistic in nature. Cancer Induction Cancer induction is arguably the most important and the most feared radiation effect. Risk Models Currently there are two models used to assess risk of stochastic effects from radiation exposure; these are the absolute and relative risk models.
Figure 2 Adapted from ICRP Publication 60 These data also demonstrate that you cannot simply use the average relative risk shown in Table 2 to estimate the increased incidence of cancer due to radiation exposure. Dose Limits Limits for exposure to radiation should be at a level below the threshold where deterministic effects occur, i. Principle of Justification: any decision that alters the radiation exposure to an individual or population should have an outcome that does more good than harm. This means that any radiation source should provide a benefit with its use, either to the individual or to society at large, and the risk of any detrimental effects must be small relative to this benefit.
Principle of Optimization: the application of radiation in any situation should be developed to minimize the risk of exposure while maximizing the benefit. When the medical benefit is retained or maximized, the risk should be as low as possible. Reference Levels The risk and benefit from medical exposures are received by the same individual.
Availability of equipment - New and changing radiation equipment technology makes the availability of some procedures limited. Availability of personnel - Personnel must have the appropriate training on the equipment to perform the procedure desired.
Alternative exams - All other non-ionizing radiation options e. How to Convey Technical Information to the Public Medical environments are full of technical jargon that the public and even some personnel within different medical professions cannot understand or interpret correctly. Risk Communication vs. Risk Education Risk communication differs from risk education. Risk Comparison The best practices when making risk comparisons is to use the following criteria: Make comparison of the same risk at two different times or circumstances Make comparison with a standard that is understood by the listener Make comparison with different estimates of the same risk Often you will read risks compared for unrelated situations.
Science and perception of radiation risk. Radiographics ; Gail MH. Hendee WR, Personal and public perceptions of radiation risk.
- Pregnancy and Medical Radiation?
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Related ICRP Publication 84: Pregnancy and Medical Radiation
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