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Association of British Science Writers absw"at"absw.org.uk These pages were designed, well, cobbled together, by Michael Kenward on behalf of the ABSW. |
RADIATION: SCIENCE AND MEDICINE A briefing document prepared for the Royal Society and Association of British Science Writers by Pearce Wright December 1995 Summary The briefing was planned as an update on the risks from low levels of radiation: especially recent findings showing they can be a genetic stimulant - capable of changing the sensitivity of cells to radiation and inducing responses like drug resistance. As it is the centennial of the discovery of X-rays, Ged Adams suggested a wider theme looking to the future of radiology in diagnosis, interventional surgery, screening and radiotherapy into the next millennium - and the already developing applications of teleradiology, 3-D digital imaging and virtual reality. In a near single-handed Technology Foresight exercise, Ian Isherwood reviewed the present and already emerging shape of diagnostic radiology beyond the year 2000. He painted a future of digital imaging that is already here: with pilot schemes of the filmless hospital, systems for producing 3-D images of organs that can be rotated on video screens, radiological consultations over the Internet, and tentative experiments in the application of virtual reality for "minimally invasive" surgery. In Britain, more than a half of all cancer patients are given a course of radiotherapy. From an oncologist's view, Gordon McVie examined the implications for screening and radiotherapy of the explosion in genetics in understanding the basis of cancer: like the variability in families of developing the disease and in the hypersensitivity of some individuals to radiation that is allied in some way to cancer susceptibility. Eric Wright outlined the minefield of research which is showing that low doses of radiation are turning out to be a genetic stimulant, that can alter the sensitivity of a cell to higher doses of radiation or to pharmaceuticals. He demonstrated the similarity with the effects of other toxins - like low doses of drugs, UV light or temporary deprivation of nutrients. He outlined the bewildering variety of processes affecting the genes that control cell progression and proliferation with which low doses of radiation might interact. a. Assessing the risk from radiation at the individual level, Sir Richard Doll gave an update on a national study into the causes of cancer in children, a major project of the United Kingdom Coordinating Committee for Cancer Research (UKCCCR). The largest case control study attempted so far, it covers 90% of cases in England and Wales. Stanley Dische described the progress of a national clinical trial with CHART, a new approach to radiotherapy. About 90% of solid cancers require primary treatment either by radiotherapy or surgery, or both. The success rate has risen with earlier detection and computer planning of therapy. b. RADIATION: SCIENCE AND MEDICINE Introduction A digest of the milestones in X-ray technology and radiation science by Professor Ged Adams, Director of the MRC Radiobiology Unit, also provided an incidental but clear case of the link between curiosity-driven academic research and innovation. Radiology was an unplanned birth. On November 8 1895, the German physicist Wilhelm Conrad Roentgen discovered X-rays in his laboratory while experimenting with a cathode ray tube. Shortly after, he made the now classic image of the bones within his wife's hand. Once doctors realised that at last they had a painless way of seeing what was happening inside a patient without surgery, medical diagnosis was revolutionised. The discovery created the era of X-ray diagnostic radiology, which for the first 50 years meant only radiography - the use of X-rays to obtain a radiograph, the image on a film. Today, radiology embraces techniques like computer tomography (CT), mammography, radioactive isotope imaging, magnetic resonance imaging, ultrasound and various interventional procedures including the use of angiography - in which blood vessels are made visible on an X-ray screen and then unblocked by inserting a catheter tipped with a balloon that is inflated at the appropriate place. Although they are based on different physics, radiography and ultrasonography form complementary technologies that are the two workhorses of diagnostic radiology. Routine pictures of fractures and other skeletal disorders and detailed images of the lungs depend on X-rays. Ultrasound is used routinely for antenatal scans to avoid risks of radiation for mother and baby. Ultrasound imaging has advantages in imaging the pancreas, spleen, kidneys and liver and the neonatal head. Although radiotherapy evolved more slowly, the foundations of cancer treatment by radiotherapy were laid a year after Roentgen's triumph, when Henri Becquerel, in Paris, discovered radioactivity - and Marie Curie unearthed radium shortly after. The increasingly intricate ways of treating cancer through combinations of radiotherapy, chemotherapy and hormone therapy are among the more recent advances by oncologists. A third fundamental and early advance came when J.J. Thomson discovered the electron in 1897, and laid the basis for modern electronics. The trio of discoveries have dominated the 20th Century. The current pace of change in radiology is astonishing, with more developments in the last 15 years than during the rest of a 100-year innovation-packed history. A new era in nuclear medicine is allowing physicians to detect disease at a cellular level by labelling its smallest molecules as targets for diagnosis or treatment. While the X-ray film is not quite a thing of the past, its future is in transition as digital imaging and computer processing are transforming every aspect of radiology. Ged Adams describes the technology as having "gone to the moon". For 60 years X-ray imaging was dominated by fluorescent screens and films. Machine detection of X-rays began with photomultiplier tubes (a special electronic valve that detected and converted X-rays into the form of electronic signals that could be displayed on a tv screen) and was transformed by CT technology. With today's computerised methods of reconstructing images and digitally storing and transmitting them, radiology is undergoing its greatest revolution. Furthermore, great hopes are pinned on the harnessing of molecular biology and biotechnology to improve the technologies of radiodiagnosis and radiotherapy. For instance, there are encouraging experiments with radioactively labelled antibodies for diagnosis and therapy. While describing radiation as a two-edged sword, Ged Adams believes concern about the risks of it as a toxin "unduly damages the appreciation of the huge benefits of the health applications of radiation". The next 100 years In assessing how the key clinical issues for radiology could benefit patients over the next 100 years, Ian Isherwood, Professor of Diagnostic Radiology in the Victoria University of Manchester, focused on 3 inter-related topics. As a pioneer of the application of CT and MRI technologies, he has a clear view of what the new advances mean for the patient. The first impact involves the provision of radiological services. They are already changing as the pattern of investigations changes to make the best diagnostic use of new technologies. The second impact is coming from the progress in understanding the genetic background of society, and its implications for screening. The third, entails the development of digital networks in hospitals and internationally. In principle, with the advances already made in digital imaging and graphic imaging so an X-ray picture can be displayed on a computer screen and examined from different angles "we don't really need the hard copy picture so much any more" he said. The trend in radiology is to replace the X-ray film or laser record with a computer stored digital image, and to convert existing hard copy images into a digital format. Once images are routinely stored digitally, communication between radiologists, and other physicians and surgeons, will be transformed. As an indicator of the way an innovation can shift the provision of clinical services, Ian Isherwood cited the breakthrough in brain imaging with computer tomography (CT) as an example. He said the 20 year-old technology had defied predictions that it would simply become another imaging device. It probably had yet to reach its plateau, in his view. The sheer number of machines in use was an impressive gauge of its importance, he suggested; especially a recent count showing that Japan has reached 70 CT machines per million of the population, a remarkable level of provision of radiological services. Refinements of the technology have continued, with an emphasis on cutting scanning times that originally took minutes to obtain an image. And the latest hi-tech idea, used at the National Heart Hospital, avoids the standard moving parts of a CT machine by electronically switching the beam round a set of detectors. The development that has transformed CT in the past 2 years is spiral scanning: instead of compiling a profile of an organ from a series of views of separate thin slices through the body, the spiral CT is a continuous scan of the part of the body containing the organ under investigation. Moreover, it produces data for a 3-D reconstruction. Although CT scanners gave radiologists a window onto the brain and unprecedented images of other organs, early hopes were dashed of using it to characterise tissue. Indeed, the only non-invasive technology letting doctors assay tissue in any substantial way is bone mineral densitometry. It is unique in looking at the mineral composition of trabecular bone. However, the drive to get functional information has advanced with spiral scanning. It opened the way of combining CT technology with the use of contrast media that is monitored and followed through tissue, giving the radiologist a clue about how well an organ is functioning by observing the flow of the contrast medium. Ian Isherwood's look at the future involved an evaluation of the factors that made CT possible. For instance, it exploited a 1000 fold improvement over the previous 15 years in computational development. But that pace of progress in information technology has continued and remains one of the most significant influences in radiology. Ten years after CT was developed, magnetic resonance imaging (MRI) emerged from the laboratories, based on using a totally different physics, to obtain tomographic, or cross-section, images. The images may look similar to CT scans, but they can be obtained in any plane or 3-D format without the radiation hazard. Instead of depending on just one phenomenon - ie how tissue absorbs X-rays - magnetic resonance can exploit a range of tissue parameters to get a picture. Image contrast using MR scans is achieved by a judicious adjustment of the scanner's radiofrequency field. An MR scan can produce, for example, an image of the spinal canal and, with an adjustment of the radiofrequency field, a detailed view of a damaged disc and the surrounding structures - in effect, simulating a myelogram that highlights the spinal cord by injecting into the spinal canal an agent that absorbs X-rays. Many branches of medicine are reaping benefits from this ability to scan soft tissue anywhere - including the examination of soft tissue in joints and within bone for the diagnosis of sports injuries, particularly knee damage. MRI contrast agents that are injected to highlight vascular or diseased tissue depend on substances with special magnetic properties. Whereas iodine shows up directly in an X-ray, an MR contrast agent alters the local magnetic environment by its paramagnetic properties. Super-paramagnetic agents contain iron particles. The MR images are then influenced by transient effects of the particles' magnetic susceptibility. Microscopic particles of iron oxide, for example, are used to target normal cells in the liver, whilst disregarding tumour cells. Consequently, MR scans then differentiate more distinctly between tumour and normal tissue. Increasing refined contrast media - whether iodinated for X-rays, gadolinium-based or iron-based for MRI - are now designed by computer to exploit advances in receptor agents. Other research suggests that a form of "living microscopy" with MRI is a practical proposition. Images of skin tumours have been produced at spatial resolutions of less than 100 microns. At the cellular level, MR images, highlighted with a contrast agent, have been used to follow the development of a fertilised egg up to the stage it divided to form an 8 cell blastomere. Living human brain cells have been observed by similar methods. For routine diagnosis, Ian Isherwood expects to see an eventual limit in a resolution of about a cubic micron - scarcely in the electron microscopy league but an astonishing performance for radiology. He anticipates other significant advances through the use of biomagnetism, electrical impedance, near infra-red spectroscopy and lasers. But the three major, predictable trends in clinical radiology will be developments for elucidating function rather than structure, interventional radiology in therapies and surgery, and the sub-specialisation in radiology. Research into human cognition and mental processes, like observing activity in the brain with PET imaging when a person is reading, is an indicator of the future. Functional neuro-imaging could complete the jigsaw that Charles Sherrington started 100 years ago; he observed that neuronal activity was connected very much with regional blood flow and cell metabolism. MRI has joined the technologies looking at function with and without the help of contrast media by, for example, visualising activities in the brain associated with motor and ocular activity. In 10 years time up to 70% of surgery will be minimally invasive. The part MRI might play is reflected in the latest development in magnets providing surgical access under direct imaging control. A new machine has been built that splits the magnet in two. A surgeon can then stand between the coils and operate under direct visual control, with an image superimposed over the surgical site Ian Isherwood describes interventional MR as an extension of existing minimally invasive therapy, but offering the surgeon an operating "macroscope" with a 3-D image of the surgical field beneath the skin. He says radiology has been driven by technology in the last 20 years. In the next 20 it is going to be driven by software and computer developments. Massive parallel computers may reach decisions by processes of fuzzy logic, object orientated modelling and perhaps even direct understanding by computers of images. Education programmes and hospital design will need to change to accommodate the new technologies. Risky dilemmas Few branches of medicine seem exempt from the discoveries tumbling almost daily from the molecular biology laboratory: diagnostic radiology and radiotherapy are no exception. Indeed, Gordon McVie, Scientific Director at the Cancer Research Campaign, says there appears to be a genetic component to everything - from traffic accidents to suicide, passing en route through diabetes, Alzheimers, rheumatism and arthritis to heart disease, asthma and the rest of the medical dictionary. Long before the current explosion in genetics, the evidence that genes were heavily implicated in cancer was clear. But the new insights from discoveries like the ubiquitous p53 oncogene - the cancer-causing gene common to many tumours, the breast cancer genes, and the colon and prostate oncogenes have raised formidable questions: such as whether and how the information might be applied in counselling services, screening and therapy. The dilemma has been highlighted by research showing the new possibilities of genetic screening. They might reveal that more women than expected have a susceptibility to breast cancer, and that a high proportion of them could also have a hypersensitivity to radiation which would preclude mammography - not to mention radiotherapy. The quandary has come with research into a rare disorder, ataxia telangiectasia. The results have implications for breast cancer and radiation sensitivity in the wider population. Ataxia telangiectasia sufferers are wheel chair-bound in their teens. They are doubly unfortunate in being both highly prone to cancer and susceptible to radiation, even in moderate doses. Radiotherapy would only make patients worse by damaging healthy tissue. Although the parents of ataxia telangiectasia sufferers are carriers of the disease gene, a recent discovery showing the parents also had a significantly high incidence of cancer came as a surprise. The dilemma was compounded further by two revelations. Any carrier of the AT gene, 1% of the population, had a higher risk of developing cancer. Women carriers of the gene were 4 times more likely of getting breast cancer. Since the results meant 5% of women with breast cancer should be carriers of the AT gene, a Cancer Research Campaign group working with David Scott, in Manchester, decided to explore the possibility of wider implications for the general population of a link between predisposition to cancer and sensitivity to radiation. Their provisional findings suggest that many more women - 13% among breast cancer patients - are sensitive to radiation; and that many other genetic aberrations and environmental factors also predisposing women to breast cancer seem likely, and yet to be found. Unfortunately, there is no easy way of identifying radiation sensitive women, or answering the radiological question of whether non-ionising radiation techniques, like MRI or ultrasound, could be devised to replace mammography. In the meantime, David Scott's team is experimenting with a sensitivity test for detecting women whose lymphocytes have a tendency to curl up and die in radiation beams; and that might provide a method for differentiating between individuals who might react well or badly to radiation. Biological effects of radiation and risk The link between high doses of radiation and malignant disease, particularly leukaemia, was established in follow-up studies of early radiotherapy patients and monitoring the Japanese bomb survivors. A more uncertain and complicated story is still emerging from research into the effects of low levels from background radiation, including the unavoidable natural exposure to radon and other environmental sources. Describing the work of teasing out the subtle influences of small doses of radiation, Professor Eric Wright, Head of Experimental Haematology at the MRC Radiobiology Unit, focused on two phenomena: the stress response and the adaptive response of cells to radiation. The nature and role of the stress response of a cell to an almost imperceptible amount of a toxic agent was first revealed when the heat shock mechanism was discovered. A sudden rise in temperature can stimulate the cell to express special gene products - heat shock proteins - to combat the effect of the heat on various components of the cell. If the cell gets a second thermal shock, the gene products expressed the first time round help to make the cell resistant to the second burst of heat. The mechanism is now known to apply through fruit flies to people, and provides the model example of the response of cells to exposure to low levels of a variety of toxic agents. The effects are triggered by seemingly disparate toxic events: from temporary deprivation of oxygen and exposure to low concentrations of a variety of chemical and poisonous agents to nutritional changes - particularly glucose deprivation of cells - and radiation. The stress response can stimulate a cell to divide, or induce resistance to more than one extraneous agent. Cross-reactions also occur with one agent inducing resistance to another, such as radiation-induced drug resistance, and vice-versa. There may be evolutionary advantages in an ability to develop resistance to a noxious agent. The downside of this adaptation, or cross-reaction, comes in the shape of resistance to what should be a beneficial agent like an antibiotic, chemotherapeutic or a therapeutic dose of radiation. Under the microscope, the changes in cells caused by ionisation radiation are seen as track structures, or blemishes that look like tiny scratches. Track structures show up in various patterns. The patterns depend on the amount of energy that is absorbed in creating the track; and that is determined by linear energy transfer (LET) property of the radiation, or the energy transferred to an absorbing medium per unit distance travelled. Energy transfer characteristics differ enormously between types of radiation. Only 4 or 5 alpha particle tracks - the type of high LET radiation coming from radon and other man-made isotopes - would deliver the energy of 1000 low LET track structures created by X-rays and gamma rays. The energy deposited in a low LET track is also more diffused through the cell, whereas an alpha particle deposits its energy very close to its track. The difference has profound biological consequences. Consequently, X-ray and gamma rays can pass through the nucleus of a cell leaving few tracks, or little energy, in the DNA. A single high LET track in the nucleus means inevitably that the DNA has had an energetic molecular interaction with radiation. Hence, the effects of low doses of radiation turn critically on the sort of radiation in question. When a single alpha particle strikes a cell a high dose is delivered, no matter how low the radiation dose may be to the overall tissue. As far as an individual cell is concerned, there is no such thing as a low dose or a low dose rate, Eric Wright says. Radiobiologists are looking at what happens to cells that survive this intense energy deposition, and, when they proliferate, if the damage is expressed in any way. Radiobiologists have known for a long time that irradiation of stem cells with X-rays can cause chromosome aberrations that are passed on to daughter cells. New experiments in cloning and irradiation of the stem (parent) blood cells are producing surprising effects that are displayed in their progeny. Irradiation experiments of cloned stem cells with alpha particles have caused a surprise in two ways. First, abnormalities arise in daughter cells, but of a different kind from X-ray induced chromosome flaws. Second, some of the daughter cells are absolutely normal but give rise to mutations in their descendants. Since the transmitted change is not a direct chromosome abnormality, some other influence appears to be at work that can cause a chromosome instability 10 or 15 cell cycles in the future. In this research, mutations observed originally in mouse stem cells are reproduced exactly in human cells. Refinements to the experiments have produced 1000 daughter cells of which just a few show the instability mutation. Thus, the picture now emerging of the effects of radiation has a new dimension. An irradiated cell may either die, correct the damage, insufficiently repair itself resulting in direct chromosome mutations, or produce long term instability. This fourth response of inducing changes related to an early history of radiation exposure, and not immediately after irradiation, suggests an important independent cell-signalling pathway has yet to be elucidated. Radiation risks Oncologists and specialists in radiological protection are still digesting the implications of what this new insight means for radiotherapy and assessing the occupational and public risks from radiation. The findings also provide an important backdrop to a study mounted by the United Kingdom Committee for the Coordination of Cancer Research (UKCCCR) into environmental radiation risks. The inquiry chaired by Sir Richard Doll is expected to report in 1997 on a nationwide investigation of all forms of cancer in children: the UK Childhood Cancer Study. An unprecedented investigation, aimed at examining the possible causes of all cases of cancer developed in children under the age of 15, already accounts for more than 90% of cases in England and Wales. While the study goal is to look at all forms of childhood cancer, the inquiry is specifically testing the main hypotheses of the causes of leukaemia. The controversy over the possible source of the cluster of leukaemia cases in the area round Sellafield provided a catalyst for the study. But before the study began, surveys of childhood cancer showed only 20% of cases could be accounted for by established causes: like the known effects of inherited abnormalities, certain powerful drugs, and exposures to ionising radiation as a foetus or in infancy. Hypotheses about the other 80% have grown steadily. Over 4000 cases of cancer have been identified so far, and are expected to exceed 5000 by the end of the year. They will be compared with 8000 controls. The (pounds)£7 million study is backed by the Leukaemia Research Fund and the Kay Kendall Leukaemia Fund with support from the Cancer Research Campaign, Imperial Cancer Research Fund, Medical Research Council and industry. A half a dozen hypotheses are under the magnifying glass. The first depends on the existing knowledge of the risks for infants of exposure in-utero or post-natally to ionising radiation, and involves examining the children's records for all medical exposures to radiation. In the process, a unique compilation is being made of all the places where each child has lived, to be followed by actual measurements of the background gamma and radon in the houses in which each child has lived for 6 months or more since conception. The second hypothesis involves the possible exposure of the child, in-utero or post-natally, to chemicals like fungicides, pesticides, and antibiotics. The third line of inquiry is probing the risk of exposure of parental germ cells to mutagens before conception. It entails assessing occupational risks of exposure to mutagenic agents, and listing all the employments of parents - including any exposure to radiation at work and at home. Estimates of the natural radiation exposures of parents are derived from the National Radiological Protection Board (NRPB) maps of the distribution of radiation throughout the country - which are scaled down to 10 km squares. The fourth hypothesis is the one causing most recent public concern, the risks of exposure to unusual amounts of electromagnetic radiation from high power cables. Establishing a satisfactory protocol for measuring the exposure to magnetic fields had given the UKCCCR team the greatest difficulties, Sir Richard said. But the NRPB and National Grid have devised ways of assessing the exposure of children to electromagnetic radiation in the course of a normal day at home and at school. The fifth supposition under scrutiny entails the effect of population mixing. The suggestion is that when people migrate from urban areas to newly developed zones, they take infections with them. These infections do not spread under urban conditions in which uninfected susceptible people are few, but they will spread in a previously thinly populated area in which the proportion of susceptible people is high. The hypothesis is that leukaemia, and particularly lymphoblastic leukaemia which occurs in children of 2 to 3 years old, might be a relatively rare abnormal response to a perhaps otherwise common infection, and is a result of this mixing effect on the spread of disease. Applying radiobiology Professor Stanley Dische, Honorary Consultant in Oncology in the Mount Vernon Hospital, explained that the treatment of cancer with radiotherapy had advanced phenomenally in the past decade; helped by more exact CT diagnosis of tumour size and pathology, and the insights of radiobiologists of the effects of radiation on living cells and organisms. With this knowledge, oncologists are devising ways to make tumours more susceptible, either to radiotherapy on its own or in a multi-pronged attack on cancer by a combination of treatments. Although targeting and destroying tumours in cancer patients by injecting monoclonal antibodies to which radioactive isotopes were attached looked promising, the magic-bullet approach to therapy has proved difficult to put into practice. So radiotherapy relies on a variety of sources of radiation: intense X-rays and particle beams to penetrate to deep-lying tumours, softer rays for cancerous tissue on or near the skin, and purpose-made radioisotopes - implanted directly into tumours or attached to a drug designed to target particular cancer cells. Whether alone, or in combination with chemotherapy and surgery, the object is to disrupt a cancer cell's biochemistry and cause it to die. It is easier said than done. Prescriptions for radiotherapy have to strike a delicate balance between delivering a lethal dose of radiation to cancer cells, while minimising exposure to surrounding healthy tissues. The planning of a course of radiotherapy treatment is to a large extent based on the experience of radiotherapy departments all over the world. Changes in treatment strategies tend to have been gradual rather than major shifts. A new approach pioneered in the UK, called CHART (continuous, hyperfractionated, accelerated radiotherapy), appears to have broken the mould. It contradicted the prevailing view that a typical course of radiotherapy was best given 5 days a week for up to 7 weeks. The new approach took account of the findings by radiobiologists that tumour cells had an inherent capacity to proliferate very rapidly. There was a risk that when treatment had destroyed large numbers of tumour cells, the remainder could realize this ability to rapidly proliferate: so that during the intervals between treatments many more tumour cells would be produced. The evidence of this ability to proliferate was determined in human tumours by giving a small dose of a drug called Bromodeoxyuridine, and analysing a small sample of the tumour, using specific antibodies to the drug and a special cell sorting machine. By re-programming radiotherapy to bring down the overall length of the course of treatment, the opportunity for tumour cells to repopulate would be reduced. Research has also shown that changes in the normal tissues after radiotherapy can be reduced by giving the treatment in many small doses. This led to the development of CHART at Mount Vernon Hospital, by Stanley Dische and Michele Saunders. The patients are treated 3 times on each of 12 consecutive days. After promising results from a 3 year pilot study, the Medical Research Council, the Cancer Research Campaign and the Department of Health sponsored randomized controlled trials in lung cancer and head and neck cancer. Centres in Bristol, Cardiff, Glasgow, Leeds, the Royal Marsden in London, Manchester, Nottingham, Sheffield and Mount Vernon in the UK, also in Dresden in Germany and Umea and Jonkoping in Sweden took part. Over 1 400 patients were involved and an interim report on the results is expected soon. Contacts Professor Ged Adams Director MRC Radiobiology Unit Chilton Didcot tel: 01235 834393 Oxon OX11 0RD fax: 01235 834776 Professor Ian Isherwood Woodend House Strines Road Disley tel: 01663 764980 Cheshire SK12 2JY fax: 01663 766498 Professor Gordon McVie Scientific Director Cancer Research Campaign 10 Cambridge Terrace tel: 0171 224 1333 London NW1 4JL fax: 0171 487 4302 Professor Eric Wright Head of Experimental Haematology MRC Radiobiology Unit Chilton Didcot tel: 01235 834393 Oxon OX11 0RD fax: 01235 834776 Sir Richard Doll F.R.S. Clinical Trial Service Unit and ICRF Cancer Studies Unit University of Oxford Radcliffe Infirmary tel: 01865 57241 Oxford OX2 6HE fax: 01865 58817 Professor Stanley Dische Honorary Consultant in Oncology Mount Vernon Hospital Rickmansworth Road Northwood tel: 01923 826111 Middlesex HA6 2RN fax: 01923 844138 Miss Anna Link Science Promotion Section The Royal Society 6 Carlton House Terrace London SW1Y 5AG Telephone: 0171 839 5561 ext 2581 12 December 1995 INFORMATION NOTE Radiation: science and medicine On 4 May 1995, the Royal Society and Association of British Science Writers held a scientific press briefing on Radiation: science and medicine. The enclosed document was prepared afterwards to summarize key issues raised by the speakers and to provide a list of helpful contacts for future reference. The document does not necessarily constitute the views of the Royal Society or the Association of British Science Writers, and views expressed in it should not be attributed to either the Society or Association. The document is free of copyright and may be used without reference to source. |
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