Radiation Exposure from CT Examinations in Japan

<p>Abstract</p> <p>Background</p> <p>Computed tomography (CT) is the largest source of medical radiation exposure to the general population, and is considered a potential source of increased cancer risk. The aim of this study was to assess the current situation of CT use in Japan, and to investigate variations in radiation exposure in CT studies among institutions and scanners.</p> <p>Methods</p> <p>Data-sheets were sent to all 126 hospitals and randomly selected 14 (15%) of 94 clinics in Gunma prefecture which had CT scanner(s). Data for patients undergoing CT during a single month (June 2008) were obtained, along with CT scan protocols for each institution surveyed. Age and sex specific patterns of CT examination, the variation in radiation exposure from CT examinations, and factors which were responsible for the variation in radiation exposure were determined.</p> <p>Results</p> <p>An estimated 235.4 patients per 1,000 population undergo CT examinations each year, and 50% of the patients were scanned in two or more anatomical locations in one CT session. There was a large variation in effective dose among hospitals surveyed, particularly in lower abdominal CT (range, 2.6-19.0 mSv). CT examinations of the chest and upper abdomen contributed to approximately 73.2% of the collective dose from all CT examinations. It was estimated that in Japan, approximately 29.9 million patients undergo CT annually, and the estimated annual collective effective dose in Japan was 277.4 *10³Sv person. The annual effective dose per capita for Japan was estimated to be 2.20 mSv.</p> <p>Conclusions</p> <p>There was a very large variation in radiation exposure from CT among institutions surveyed. CT examinations of the chest and upper abdomen were the predominant contributors to the collective dose.</p

Risk of Cancer from Diagnostic X-rays : estimates for the UK and 14 other countries

目的:The Lancetに掲載されたBerrington氏らによる論文をレビューし,CT検査の在り方について考察する.方法:Risk of Cancer from Diagnostic X-rays : estimates for the UK and 14 other countriesという論文をレビューし,CT検査の利益および不利益という見地から,CT検査の在り方について考察する.結果:本論文において,診断X線検査の放射線による発がんの寄与リスクは,他国に比べ日本が最も高く,日本で年間に発症するがんのうち,3.2%(年間7,587例の発がんに相当)が,診断に使われている放射線によるものであると推定された.結論:放射線を人体に照射する業務を行う我々は,患者に放射線による有害な影響の可能性を上回る利益を提供できるようにするべきであり,防護の最適化について,より工夫する必要がある.Objectives : To review the article by Dr. Berrington de Gonzalez in The Lancet and consider the conduct of CT examinations in Japan. Methods : The article on the cancer risk of X-ray diagnostic examinations in the UK and 14 other countries was reviewed, and then the utilization of CT examinations in Japan was examined from the perspective of the advantages and disadvantages of CT examinations. Results & Conclusions : The article mentioned that, compared with other countries, Japan has the highest annual frequency of diagnostic X-rays. Japan also demonstrated the highest attributable risk, with 3.2% of the cumulative risk of cancer attributable to diagnostic X-rays, equivalent to 7587 cases of cancer per year. In terms of the usage of CT examinations in Japan, we who are involved in performing radiological examinations must ensure that the benefit to the patient exceeds the potential harms from radiation exposure, and we must devise methods to optimize radiation protection.報

"Risk of Cancer from Diagnostic X-rays : estimates for the UK and 14 other countries"

目的:2004年にLANCETに掲載された論文"Risk of Cancer from Diagnostic X-rays : estimates for the UK and 14 other countries"(英国を含む14か国における診断用X線検査による発がんリスクを推定したもの)を教育的にレビューし,診療放射線技師による放射線防護の視点より,Computed Tomography(CT)検査の妥当性について考察する.方法:論文を読み,そのデータや結論をレビューし,関連文献検索を加えた.結果:示されたがん発生リスクのデータには疑問の余地がある.しかしながら,医療被ばくにおいて本邦のCT検査が大きな比重を占めているということは事実である.結論:医療被ばくの低減には,CTによるX線検査の頻度を下げること,装置間,施設間による線量のバラツキを最小化することがかかせない.Objectives : To review the article of "Risk of cancer from diagnostic X-rays : estimates for the UK and 14 other countries" which estimated the cancer risk from diagnostic X-rays in 14 countries including the U. K published in Lancet in 2004 and to discuss the validity of CT examinations in Japan from the viewpoint of radiation protection by radiation technologists. Methods : The article was reviewed, and the related documents were investigated. Results : The estimated cancer risk for Japan seems to be uncertain. However, CT examinations in Japan play a major role in radiation exposure. Conclusion : To reduce radiation exposure, it is necessary to lower the frequency of X-ray check-ups and to reduce the unevenness of the radiation dose from devices in institutions.報

A new shielding calculation method for X-ray computed tomography regarding scattered radiation

鈴鹿医療科学大

Radiation in medicine: Origins, risks and aspirations.

The use of radiation in medicine is now pervasive and routine. From their crude beginnings 100 years ago, diagnostic radiology, nuclear medicine and radiation therapy have all evolved into advanced techniques, and are regarded as essential tools across all branches and specialties of medicine. The inherent properties of ionizing radiation provide many benefits, but can also cause potential harm. Its use within medical practice thus involves an informed judgment regarding the risk/benefit ratio. This judgment requires not only medical knowledge, but also an understanding of radiation itself. This work provides a global perspective on radiation risks, exposure and mitigation strategies

The Risk of Cancer from CT Scans and Other Sources of Low-Dose Radiation: A Critical Appraisal of Methodologic Quality

AbstractIntroduction: Concern exists that radiation exposure from computerized tomography (CT)&nbsp;will cause thousands of malignancies. Other experts share the same perspective regarding the&nbsp;risk from additional sources of low-dose ionizing radiation, such as the releases from Three&nbsp;Mile Island (1979; Pennsylvania USA) and Fukushima (2011; Okuma, Fukushima&nbsp;Prefecture, Japan) nuclear power plant disasters. If this premise is false, the fear of cancer&nbsp;leading patients and physicians to avoid CT scans and disaster responders to initiate forcedevacuations is unfounded.Study Objective: This investigation provides a quantitative evaluation of the methodologic&nbsp;quality of studies to determine the evidentiary strength supporting or refuting a causal relationshipbetween low-dose radiation and cancer. It will assess the number of higher qualitystudies that support or question the role of low-dose radiation in oncogenesis.Methods: This investigation is a systematic, methodologic review of articles published from&nbsp;1975–2017 examining cancer risk from external low-dose x-ray and gamma radiation,&nbsp;defined as less than 200 millisievert (mSv). Following the PRISMA guidelines, the authors&nbsp;performed a search of the PubMed, Cochrane, Scopus, and Web of Science databases.&nbsp;Methodologies of selected articles were scored using the Newcastle Ottawa Scale (NOS)&nbsp;and a tool identifying 11 lower quality indicators. Manuscript methodologies were rankedas higher quality if they scored no lower than seven out of nine on the NOS and contained no&nbsp;more than two lower quality indicators. Investigators then characterized articles as supporting&nbsp;or not supporting a causal relationship between low-dose radiation and cancer.Results: Investigators identified 4,382 articles for initial review. A total of 62 articles met all&nbsp;inclusion/exclusion criteria and were evaluated in this study. Quantitative evaluation of the&nbsp;manuscripts’ methodologic strengths found 25 studies met higher quality criteria while 37&nbsp;studies met lower quality criteria. Of the 25 studies with higher quality methods, 21 out of 25did not support cancer induction by low-dose radiation (P = .0003).Conclusions: A clear preponderance of articles with higher quality methods found no&nbsp;increased risk of cancer from low-dose radiation. The evidence suggests that exposure to&nbsp;multiple CT scans and other sources of low-dose radiation with a cumulative dose up to&nbsp;100 mSv (approximately 10 scans), and possibly as high as 200 mSv (approximately 20&nbsp;scans), does not increase cancer risk

Report of IRPA task group on the impact of the eye lens dose limits

In 2012 IRPA established a task group (TG) to identify key issues in the implementation of the revised eye lens dose limit. The TG reported its conclusions in 2013. In January 2015, IRPA asked the TG to review progress with the implementation of the recommendations from the early report and to collate current practitioner experience. This report presents the results of a survey on the view of the IRPA professionals on the new limit to the lens of the eye and on the wider issue of tissue reactions. Recommendations derived from the survey are presented. This report was approved by IRPA Executive Council on 31 January 2017

γ-H2AX foci as in vivo effect biomarker in children emphasize the importance to minimize x-ray doses in paediatric CT imaging

Objectives: Investigation of DNA damage induced by CT x-rays in paediatric patients versus patient dose in a multicentre setting. Methods: From 51 paediatric patients (median age, 3.8 years) who underwent an abdomen or chest CT examination in one of the five participating radiology departments, blood samples were taken before and shortly after the examination. DNA damage was estimated by scoring gamma-H2AX foci in peripheral blood T lymphocytes. Patient-specific organ and tissue doses were calculated with a validated Monte Carlo program. Individual lifetime attributable risks (LAR) for cancer incidence and mortality were estimated according to the BEIR VII risk models. Results: Despite the low CT doses, a median increase of 0.13 gamma-H2AX foci/cell was observed. Plotting the induced gamma-H2AX foci versus blood dose indicated a low-dose hypersensitivity, supported also by an in vitro dose-response study. Differences in dose levels between radiology centres were reflected in differences in DNA damage. LAR of cancer mortality for the paediatric chest CT and abdomen CT cohort was 0.08 and 0.13% respectively. Conclusion: CT x-rays induce DNA damage in paediatric patients even at low doses and the level of DNA damage is reduced by application of more effective CT dose reduction techniques and paediatric protocols

State of the art: iterative CT reconstruction techniques

Owing to recent advances in computing power, iterative reconstruction (IR) algorithms have become a clinically viable option in computed tomographic (CT) imaging. Substantial evidence is accumulating about the advantages of IR algorithms over established analytical methods, such as filtered back projection. IR improves image quality through cyclic image processing. Although all available solutions share the common mechanism of artifact reduction and/or potential for radiation dose savings, chiefly due to image noise suppression, the magnitude of these effects depends on the specific IR algorithm. In the first section of this contribution, the technical bases of IR are briefly reviewed and the currently available algorithms released by the major CT manufacturers are described. In the second part, the current status of their clinical implementation is surveyed. Regardless of the applied IR algorithm, the available evidence attests to the substantial potential of IR algorithms for overcoming traditional limitations in CT imaging

イリョウ ヒバク ノ ゲンジョウ

Interventional radiology （fluoroscopically-guided） techniques are being used by an increasing number of clinicians not adequately trained in radiation safety or radiobiology. In 1994, Food and Drug Administration of the United States first gave warning to the risk of serious X-ray-induced skin injuries including intractable ulcers among patients who received fluoroscopically-guided procedures. The Japan Radiological Society reacted promptly, and gave a warning in 1995, and the first report on radiation skin injury during prolonged fluoroscopy in Japan appeared in 1998 on a dermatological journal. Since then many cases have been reported on dermatological journals. Radiation skin injuries occurred mainly during cardiac studies, but cases of abdominal studies also have been reported. Recently there was a case report of skin malignancy in a long standing radiation induced ulcer. The international commission on radiation protection published“Publication 85 Avoidance of Radiation Injuries from Medical Interventional Procedures”in 2000. This document can be summarized in the following three major points : 1）The risk of radiation injury should be explained to the patient prior to IVR （informed consent. 2） Protocols should be prepared to define the number of images to be taken and the fluoroscopy time for each procedure of IVR so that standard radiation doses can be calculated. 3） If the cumulative absorbed dose to the patient’s skin exceeds 3 Gy （1 Gy for procedures likely to be repeated）, the site and dose of radiation given should be recorded in the patient’s record. If the dose is more than 3 Gy, the patient should be followed up 10 to 14 days after the procedure. It is very important to measure the cumulative absorbed dose of the skin, but very difficult. We developed a very reliable system for the measurement using a self-developing reflecting-type sheet film and reported their usefulness. CT examinations also have been increasing dramatically in Japan. There was a report of estimation of possible risk of cancer after CT examination based on a hypothesis. Although there has been no evidence of real risk of low dose radiation exposure such as CT reported, we should try to use CT appropriately. Especially we must try to reduce CT dose to children or young adults, because they are more sensitive to radiation and live longer than adults