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KMID : 9000220160010010129
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NECA Research Report
2016 Volume.1 No. 1 p.1 ~ p.129
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Kim Min-Jeong
Do Kyung-Hyun
Tchoi Ha-Jin
Kim Su-Kyeong
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Abstract
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? Background
Ⅰ. Background and purpose of study
Medical radiation means to artificially generate ionizing radiation and to use it in medical field for the purpose of human health benefits, and its importance and usage ranges in the modern medicine become larger due to non-invasive feature, scientific technologies development, etc. At present, uses of medical radiation for diagnosis account for the most parts of total medical radiation exposure, therefore diagnostic radiation affects extensively many people. The uses of diagnostic radiation are increasing and there are great deviations on the usage in accordance with the level of each country's living and income. In particular, uses of Computed Tomography (CT) have increased, which has become a major factor in the increase of diagnostic radiation dose.
Efforts to reduce unnecessary radiation exposure of the increase in diagnostic radiation have been made in various ways, such as through international organizations and national professional organizations. To reduce unnecessary radiation exposure to the patient, in order to provide a dose management plan for your country situation, investigating international organizations are to understand the management system and the key principles and practices of other countries will be needed first.
Ⅱ. Methods
○ To review the evidences for the medical radiation risks and approaches for uncertain risk management, relevant studies and literature and recommendations of international expert groups were analyzed.
○ International safety standards and foreign advanced management practices on the patients diagnostic radiation dose managements were investigated, analyzed and compared to domestic status.
○ According to the international medical radiation safety management and the core principles and guidances, the future directions for the proposed comprehensive actions were derived.
Finally, "Bonn Call-for-Action (2012)" proposed by the International Atomic Energy Agency (IAEA) and the World Health Organization (WHO) to prioritize activities to identify and fulfill the responsibilities for stakeholder in relation to the radiation protection of the medical field for the next decades and model regulations collected from participating the training workshop on radiation safety regulations for the management organized by IAEA were added to the appendix.
? Results and Discussion
Ⅰ. Review of evidence on diagnostic radiation risks
○ When a person is exposed to high doses of radiation over a certain level, the one suffers apoptosis and functional disability, and this is called the deterministic effects of radiation. In diagnostic radiology area that a relatively low dose of radiation is used, probability of deterministic effects of radiation to appear in a normal application process is very low. Deterministic effects, the unintended medical exposure can be prevented by design modification of medical devices used in diagnosis and comprehensive quality assurance including proper management and operation of equipment and software. And a systematic approach is needed to properly monitor the systems and to report incidents and near misses to prevent similar adverse events.
○ Somatic mutations and subsequent cancers would occur due to radiation exposure, or germ cell mutations resulted from radiation exposure would affect genetic diseases of descendants, which are the stochastic effects of radiation. These effects may appear or not, that is considered to be a problem of probability. The threshold does not exist, but probability of the stochastic effects occur is considered to increase in proportion to the absorbed dose.
○ In order to exactly prove the hazard of low dose radiation, large cohorts with long-term follow-up period, identification of how various genes associated with cancer interact, and consideration of confounding factors such as weak genetic factors on cancer are required. However, in reality it is not easy to carry out the epidemiological and molecular biological studies meeting these requirements. Several international professional organizations and bodies are performing the scientific reviews and assessments with respect to radiation risks, and according to the evidence to date, in the low-dose of less than about 100 mSv of radiation, the evidence remains uncertain although there have been several study results regarding radiation risks.
Ⅱ. Diagnostic radiology risk management
○ Although a risk is uncertain and it is difficult to predict and measure the risk, it needs to develop a predictive model as to protect people and environment from the uncertain risk which might result in serious harm threatening to human life or health such as genetically modified organisms or climate change, this is the precautionary principle. The process of applying these principles should be open and democratic, and include all the groups that are potentially affected. In addition, careful consideration about alternatives including the cases not choosing the methods to prevent the potential risk from occurring or to reduce the risk should be made in advance.
○ Although several studies have reported on potential risk of cancer from low-dose radiation, the evidence for the risk is uncertain. Due to the uncertainty of evidence, the basic concept of medical radiation safety management is represented by the 'ALARA (As Low As Reasonably Achievable)' principle, which means to keep the likelihood of potential exposure, the number of people exposed and the magnitude of individual dose as low as reasonably achievable, with social and economic factors being taken into account.
○ For medical exposure of patients, only the two principles, justification of medical exposure and optimization of protection are applied, and the principle of dose limits cannot be applied. Justification of medical exposure refers to the total radiation exposure from which they take place only if the benefit is greater than the harm, it is the responsibility of the medial doctor to justify in certain medical procedures, so the doctors should be educated and trained on radiation protection. Optimization of protection is defined to keep the magnitude of individual dose, the number of people exposed and the likelihood of potential exposure as low as reasonably achievable, with social and economic factors being taken into account. To execute the justification and optimization principles, there have been materialized action principles proposed. For justification, practice of the 3As of awareness, appropriateness and audit for justification is important, and establishment and management of infrastructure, appropriate use of equipment and technology, and setting and deployment of Diagnostic Reference Levels (DRLs) are emphasized for optimization.
Ⅲ. International diagnostic radiation dose management system
○ Management of infrastructure elements
① Quality control and quality assurance programs
The British law for medical radiation exposure of patients (Ionising Radiation (Medical Exposure) Regulations 2000, IR(ME)R 2000) focusing on radiation protection of patients requires to establish the quality management system within medical institutions. Each medical exposure officer should set the quality assurance program for standard operating procedures, whereby each institution should establish and operate these programs.
In the United States, the breast diagnostic imagings are managed separately by the Mammography Quality Standards Act. Other diagnostic MRI, CT, PET need accreditation by the Medicare Improvement Act for patients and healthcare providers. And additional managements for radiological equipments are performed at the audit department of medical imaging equipment in the state governments.
② Professional workforce management
According to the law of ionizing radiation exposure in the United Kingdom, medical practitioner and operator should receive appropriate training. The employer ensures every practitioner or operator carrying out medical exposures to be educated and trained continuously after qualification including training and the relevant radiation protection requirements for use of new techniques. In addition, when performing medical radiological task, the employer should maintain training records for the detail field and prepare the audit, and ensures medical practitioner and operator complete the training needed to use the equipment for use of a new medical device.
In the United States, it has implemented the workforce management including qualification and continuous education and training through state government laws and accreditation systems. For example, the Texas State implemented all medical doctors and the delegated personnel involved in the use of fluoroscopic intervention should complete the relevant education and training of 8 hours of theoretical education and at least 1 hour of practical training. Hospitals should keep complete records of the relevant radiation safety training of health professionals during the doctor conducts the fluoroscopic intervention in the hospital. American College of Radiology (ACR) accreditation scheme presents detailed criteria for doctors, radiologists, radiological technicians, medical physicists in accordance with the job requirements. The basic qualifications (degrees, licenses, certifications, etc.), work experience and continuing medical education requirements for licensure after takes place through an assessment.
○ Establishment and application of Diagnostic Reference Levels (DRLs)
Diagnostic Reference Levels (DRLs) was first proposed as a method for optimization of radiation protection in the United Kingdom. It was designed to evaluate the current protocols and to develop optimized protocols by comparing with the protocols from other facilities on imaging procedure of a routine condition. If the dose level measured at a facility is abnormally higher or lower than the diagnostic reference level adopted and used by the facility, corrective actions can be made to optimize the current protocols. According to the periodic dose monitoring, diagnostic reference levels have continued to decrease in the United Kingdom. This practical example suggests that to establish and continuously applicate the diagnostic reference levels can help limit the unnecessary irradiation dose.
The ACR operates several types of radiation dose data registry in the United States. For quality management each medical facility compares the difference with a reference point (bench mark) and the area reference point in the United States. A report is created based on the collected data from the National Radiology Data Resgistry, and this report is sent twice a year to facilities. Each medical facility can use this report as a basis for continuous quality management and carry out corrective actions if needed.
Ⅳ. Domestic status
○ Status of radiation diagnostic device
In Korea the introduction of diagnostic imaging equipment of high price such as CT, MRI is higher than the OECD average. In 2011 OECD countries had an average of 23.6 CTs per million population million. South Korea was 35.9 CTs, which was top fifth of the 29 countries. MRI was sixth among the top 28 countries by 21.3 per population million.
In 2012 a survey on CT devices which are capable of displaying radiation dose was conducted. Devices that cannot display dose were equivalent to 43% of the total, and 12% of general hospitals, 51% of hospitals, and 66% of clinics held the equipment that cannot display dose information.
○ Radiologic examination frequency using radiation diagnostic equipment and national radiation dose status
The examination number using radiologic diagnostic equipment has increased, by about 10% increase annually from 2006 to 2011. From the national health insurance claims data, the overall increment rate of CT examination numbers tended to decrease recently excluding a sudden increase in 2011.
According to previous studies used the main secondary data sources and derived the Korean radiation dose, the average effective dose per examination by angiogram and CT scan was 6.9 mSv and 6.1 mSv, respectively, which was not different with the data of other countries. The total radiation dose estimates in 2011 based on status of the examination frequency was 68,000 person?Sv, approximately 50% increased compared to 2007. CT examination was 38,000 person?Sv, 56% of the total radiation. The per capita effective dose was estimated to be 1.4 mSv, this excluded the radiologic examinations which is not reimbursed by national health insurance, nuclear medicine and interventional procedures, therefore the estimate is considered to have been underestimated than the actual value.
? Conclusions and Recommendations
○ Strategy of radiation dose management in accordance with the key radiation safety principles - aspects of the justification principle
The stage clinical decision issued on radiographic examination or intervention is when the step of justification principle is to be implemented. It should be determined whether or not to carry out the test in consideration of each test would benefit to the patient by each examination independently. Therefore, to define appropriate responsibility and to impose duty on it to the expert making clinical decisions should be preceded.
It is important to ensure the appropriateness of a test or treatment, in other countries referral or clinical decision supporting guidelines or tools were developed and recommended to implement.
However there are practical limits only in recommendations of these guidelines, therefore monitoring of compliance with these guidelines and internal and external audits are needed to be carried out within the range that does not infringe the expert area.
○ Strategy of radiation dose management in accordance with the key radiation safety principles - aspects of the optimization principle
The optimization principle is the concept which is considered at the steps to practice test or procedure after the clinical decision justified is conducted. It means that the dose is used As Low As Reasonably Achievable (ALARA) to acquire images with acceptable levels of quality for addressing clinical questions.
First, this requires activities to establish and manage infrastructure, which includes establishing comprehensive quality assurance programs including selection of equipment and software that meets the IEC/ISO/country specifications, managing human resources through professional education and training, equipment calibration, measurement and record of physical parameters, record of process and results, and periodic and independent audits.
In addition, as factors regarding to proper operation of equipment and technologies, to comply with the standard imaging protocol and to have an idea of the appropriate image quality are important. Standard protocols should be developed for all imaging examination techniques, in Korea, such a development is in progress. Also it requires periodic updates of the protocols with the development of equipment. In particular, it needs to reduce radiation dose for pediatric imaging tests compared to imaging for adults, and pediatric protocols should be used separately.
Implementation of the diagnostic reference levels (DRLs) is helpful for optimization of radiation protection. To establish the DRLs, continous and periodic dose survey should be carried out. In Korea, the first DRLs was established and suggested through research projects of national organization and it requires continuous and periodic updates ahead.
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KEYWORD
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Diagnostic radiology, patient medical exposure, dose management, radiation protection, justification, optimization
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