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Commentary |
1Department of Diagnostic Radiology, Hairmyres Hospital, East Kilbride G75 8RG, 2Clinical Physics Group, St Bartholomew's Hospital, West Smithfield, London EC1A 7BE and 3Medical Engineering and Physics, King's College Hospital, London SE5 9RS, UK
The 10th International Congress of the International Radiation Protection Association (IRPA) was held on 14–19 May 2000 in Hiroshima. This conference is held every 4 years, a reasonable time interval that could usefully be copied by other international congresses, as it allows the development of new ideas and science for debate.
Hiroshima is a bustling city, but also the self-styled "city of peace". The conference centre is on the periphery of Peace Memorial Park, built on a site beneath the epicentre of the bomb. There are a number of statues and monuments within the park, the best known being the "A-bomb (Genbaku) dome", one of very few structures within a 1500 m radius to survive the blast and now a world heritage site. Each day the park receives hundreds of visitors of all ages and nationalities.
The big issue at the conference was the debate on "controllable dose", a concept promoted by Roger Clarke in 1998, which has received much attention in the radiation protection community [1]. In 1999, the IRPA invited its member societies worldwide to comment on the proposals for major revision to the International Commission on Radiological Protection (ICRP) system for radiological protection. The outcome was a series of position papers from many member societies, including the UK Society for Radiological Protection, leading to a major debate in Hiroshima. The overall purpose was to review the current effectiveness of radiation protection and to provide input at an early stage to the ongoing work for a new or revised recommendation for the future. A full report of the debate was published in the Journal for Radiological Protection, to which the interested reader is referred [2]. It is sufficient to say here that the consultation process was widely acclaimed, that the basic principles of justification, optimization and dose limitation have proved sound and that in any review, defects and weaknesses should be corrected before introducing more radical change. Guidance on interpretation of the present system of radiation protection and means of communication with others needs amplifying, as well as involving other professional groups and the public. In summary, the radiation protection community received the Clarke proposal with interest but were conscious of the need to establish the existing framework more widely before introducing further changes. The proposals also threw up an interesting problem, not often considered in the past but becoming an increasing difficulty, namely that of language and terminology. Many different meanings and nuances can be put on a word in any one language, but the same word cannot always be directly translated into another language as the word may not exist or the concept is not understood.
Traditionally, the conference opens with the Sievert Lecture and Award. Itsuzo Shigematsu (Japan) discussed lessons from the Atomic Bomb Survivors in Hiroshima and Nagasaki. He raised the possibility that the current survivors may reflect a resistant subpopulation that is not representative of overall human risk, and emphasized that radiation dosimetry remains essential for identifying an exposed population so that dose–response relationships can define the health risks of radiation. He pointed out that absolute risk is the fundamental index for assessing the frequency with which a radiation-induced disease occurs and concluded by describing the work of the Adult Health Study, which has been following a subsection of 20 000 survivors since 1958. Not only has this given data on emerging and non-fatal effects of radiation, but also on the ageing process in the Japanese population.
The scientific programme was divided into 24 main topics, covering all aspects of radiation protection, from cosmic to underground, from medical to nuclear, from containment to communication with the public. The proceedings of this conference have been published on CD-ROM. This is a great improvement from before and made a significant difference to the degree of arm strain experienced by delegates on returning home! The CD-ROM is available from the Business Center for Academic Societies Japan [3]. This commentary does not intended to go into a great deal of detail on the programme, but some comment on the medical and physics sessions is appropriate.
Medically, there were two main themes: improvement in diagnostic techniques with lower exposure of patients and staff; and radiation protection for interventional radiology. The keynote lecture on improvements in diagnostic techniques was strangely allocated to an oncologist and, while interesting in itself, sadly missed many important development issues such as improvements in tube design leading directly to dose reduction and oddly overlooked the introduction of rare earth screens. It introduced the concept of as low as reasonably achievable (ALARA), now at least 15 years old.
All papers proffered to this conference, when accepted, were only accepted as posters. Three or four were selected for a 15 min oral presentation. Time was found in the programme for the posters to be visited and discussed on site, although the posters themselves were only on display for 24–36 h. The four papers in the first session were remarkably disparate. The first reported on medical radiation usage and exposure in Shandong Province, China and was perhaps one of the first papers to give information to the Western world on the extent of use of medical radiation in China. It is interesting that there has been a 27.8% increase in the use of CT in the last 2 years, to 16.1 examinations per 1000 population in 1998. Compared with 22.6 CT examinations per 1000 population in 1997/8 in the UK, the use of CT in China is not too far behind. The next paper discussed the influence of radiologist's technique on patient dose in barium studies and showed a major difference between the UK and doses often found in other countries. Typical doses for barium enemas in the UK were in the region of 20–29 Gy cm2, with doses in Finland and Spain found to be more in the region of 36 Gy cm2 and 50 Gy cm2. Doses in the UK for barium meals ranged from 4–15 Gy cm2. In Greece the same examination produced exposures of 23 Gy cm2, in India 22 Gy cm2 and in Spain 33 Gy cm2. Papers on fetal radiation dose from radiopharmaceuticals administered during pregnancy and the optimization of patient protection in diagnostic radiology by the use of guidance levels completed the first session.
The second medical session, on interventional radiology, was opened by Hironobu Nakamura (Japan). He discussed the development and increasing importance of radiation protection in interventional radiology, especially in the light of more complex procedures, hence increasing fluoroscopy times and dose. He reported that 7.2% of cases required fluoroscopy for 60 min or longer and 0.85% required 120 min or longer. Experimental results showed that with an overcouch tube, the eye lens of an interventional radiologist may be exposed to more than 150 mSv year-1, although at his facility overcouch tube devices are seldom used, even for non-vascular interventional radiology. He emphasized the need to wear protective glasses and advocated the use of patient dose display on the monitors. He concluded with three main comments:
To a UK audience these principles are widely understood and accepted. However, this session demonstrated that such basic ALARA principles are not universally applied, particularly in the developing nations.
Four proffered papers were given. The first of these described the effect of radiation doses in 82 interventional radiologists in Shandong Province, China. Language problems abounded here. The speaker was able to read a prepared text, but not to understand or answer questions. She concluded that interventional radiologists had received higher doses (12–168 mSv year-1) than ordinary radiologists and were in poor health. Many were suffering from headaches, languor and palpitation. There were also significant differences in cell counts, cell anomalies and chromosome aberration frequencies between the interventional radiologists and the traditional radiologists or control group. Bewildered by these reports, the audience could not elicit more details from the speaker owing to the language barrier, but drew the conclusion that radiologists were not wearing protective clothing! The next paper, with an English author but given by an Austrian-based Spaniard, described the deterministic effects that have been found both in patients and staff following interventional procedures and reviewed the lessons learnt from investigation of the incidents. The last paper reported on an investigation of doses received by cardiologists in Brazil; not surprisingly the highest dosages were received by the hands, followed by the eye. Advice to wear eye protection and to reduce the number of procedures performed per cardiologist per week has been given.
The session concluded with a description of a real-time extremity dose monitor to be worn on the wrist, currently under development. Initial reports claimed it worked reasonably well, but it was described as being rather bulky. One author (RHC) feels it needs considerable development, with remote visualization of the dose—who is going to stop in a procedure to look at their wrist? Also, the monitor will need to be sterilizable or need to be worn under sterile gloves, matters not apparently appreciated by the developers.
The Congress was made even more interesting by the polemic debate that went on between those who believe that radiation, no matter how small the dose, can cause detriment and those who do not hold this view but propose that low dose radiation can, in some cases, bring benefit. Groups of scientists in different parts of the world challenge the validity of the linear no-threshold hypothesis on which the current radiation protection concept of ALARA is based. Reports from animal experiments suggested that cells exposed to low levels of radiation can develop "adaptive responses" that reduce the risk of the cells being transformed into cancer cells by a subsequent exposure. Supporters of this view call for a new risk-based approach to radiation protection based on biology rather than dose.
A new aspect of the conference was the inclusion of a special session to allow member societies to air matters and issues of importance to them. The main themes were the ethics of radiation protection, the establishment of societies, the arrangements for international meetings and the debate on whether the IRPA should be involved with standards, the future of publications, research and education. Risk communication and perception remained a thorny problem requiring further thought.
The meeting was complemented by an interesting technical exhibition biased heavily towards the nuclear industry. The vast majority of the stands were concerned with practical dosimetry, monitors and nuclear engineering. No diagnostic equipment manufacturers were present to show how they implement dose protection and dose reduction procedures. Should they have been?
The highlight of the conference for some delegates, organized by the Peace Memorial Museum adjacent to the conference centre, was a talk by one of the bomb survivors. A diminutive lady in her 70th year described through a translator her experience as a 15-year-old schoolgirl drafted in to help the war effort by working in the telegraph office. On a beautifully sunny morning in August, only an hour after the air raid sirens had signalled the "all-clear", she saw a bright light falling from the sky followed by a huge explosion that rendered her unconscious. On regaining consciousness and having lost her sight, she described her rescue from the ensuing firestorm by one of her teachers. She subsequently received extensive plastic surgery to burns on her face and regained the sight of one eye. In her later years she has been diagnosed with both breast cancer and cervical cancer. The extent of her suffering is, perhaps, no greater than that of many others subject to man-made devastation, but poignant in the circumstances. Her witness clearly gripped the attention of the audience.
The IRPA General Assembly was held on the traditional "afternoon off" for most delegates. A full report can be found on the IRPA website [http://www.irpa.net]. Geoff Webb (UK) was elected president for the next 4 years. The 11th conference will be held in Madrid in May 2004.
Received for publication December 1, 2000. Revision received May 29, 2001. Accepted for publication June 14, 2001.
References
irpa10/CD-ROM/index.html
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