Читать книгу What Doctors Don’t Tell You - Lynne McTaggart, Lynne McTaggart - Страница 16

X-rays are the most common procedure you’re likely to be exposed to at least once in your lifetime. Today they represent approximately 10 per cent of any Western nation’s health expenditure. Ionizing radiation is actually comprised of very high-frequency waves, which pass through living tissue. Depending on how dense the tissues are, the body retains some of this radiation. These absorbed rays are what gets recorded on the film as white or grey; those that pass completely through hit a plate of photographic film and show up as dark grey or black. Besides mammograms, bone x-rays and dental x-rays, the newest kind of x-rays include CAT scans, in which a moving beam of x-rays creates a three-dimensional picture, usually of the brain, and fluoroscopy, which sends the x-ray shadow picture onto a television screen. Occasionally contrast dyes like iopamidol or mediums like barium are used to provide a clearer picture.

Although the newest equipment uses lower and more precisely targeted doses, there is still no such thing as a safe x-ray (that goes for dental x-rays, too). In all of medicine there is virtually no disagreement that ionizing radiation is damaging – and those risks are multiplying as our understanding of the medium grows. ‘Medical irradiation is by far the largest man-made contribution to the radiation burden of the population of developed countries,’ R. Wootton, professor and director of Medical Physics at Hammersmith Hospital in London, wrote in a textbook on the subject. In the UK, he says, x-rays ordered by doctors account for over 90 per cent of the total radiation exposure of our population.⁴¹

X-rays harm people in three ways. First, they can damage individual cells (although the harm caused by the lower doses is usually quickly repaired). Rarely (but depending on exposure), this damage can convert the cell to a cancer cell. Although we don’t know exactly how this works, it has been proposed that, since a cell is 75 per cent water, most of the radiation will be absorbed by the water, forming free radicals, which are known to be carcinogenic.⁴²

Second, if a woman is pregnant, it can injure the developing foetus, causing death or malformations.

Finally, x-rays can damage the sperm or ovaries of children or adults, causing abnormalities in future generations. We also know that x-ray exposure is cumulative; the danger of something going wrong may increase every time you get another one.

We’re still coming to grips with exactly how dangerous x-rays are, however. Unnecessary radiation from x-rays may be responsible for 700 cancer deaths in the UK every year, and perhaps 5,700 cancer deaths per year in the US, according to a recent Oxford University study.⁴³ But these figures may still be conservative. A UK National Academy of Science committee reviewed the usual assumptions that x-rays were responsible for 1 per cent of all leukaemias and 1 to 2 per cent of all other cancers, and concluded that the real risk could be as much as four times higher⁴⁴ – a conclusion also reached that same year by the International Commission on Radiological Protection.⁴⁵ Recently, multiple x-rays have even been linked with multiple myeloma – a form of bone cancer now sharply on the rise. Those who’d had the most exposure had a four times increased risk, the National Cancer Institute found.⁴⁶

As far back as the 1950s, medicine discovered a link between leukaemia and prenatal x-rays. X-raying pregnant woman used to be routine, on the ludicrous notion that x-rays could tell a doctor whether her pelvis was ‘wide enough’ for the foetus to fit through during birth. We now know that if children are exposed to x-rays in utero their risk of all cancers is increased by 40 per cent, of leukaemias by 70 per cent, and of tumours of the nervous system by 50 per cent.⁴⁷ There also may not be a safe ‘dose threshold’; single babies who’d received five to six times less radiation than twins who’d been x-rayed more frequently had the same incidence of cancer.⁴⁸ To put these numbers in perspective, for every million babies exposed in the womb to even a single rad of x-rays – the equivalent of a single picture of the stomach and intestines – between 600 and 6,000 could develop leukaemia.⁴⁹ John Gofman, Professor of Molecular and Cell Biology at the University of California, believes that women who undergo yearly mammograms receive cumulative doses not unlike the Japanese atomic bomb survivors.⁵⁰

Gofman estimates that women’s breasts receive 0.4 rad of medical x-rays a year for each year of life. If you compare that dosage with the levels suffered by Japanese atomic bomb survivors, he says, 114,000 women, from 62 to 75 per cent of those diagnosed every year with breast cancer, could blame x-rays as the cause. Besides cancer and genetic deformities, x-rays of the brain can lead to abnormal hormonal function, possibly causing underactive thyroid and infertility, or resulting in subtle changes in your adrenal glands.⁵¹ The US Food and Drug Administration has also lately received a number of reports of patients suffering skin burns after radiation, so severe in some instances that the skin has died. The problem is complicated by the fact that these injuries don’t show up for weeks after exposure. Your typical dose of fluoroscopy can result in skin injury after less than an hour.⁵²

Even the offspring of those exposed to x-rays suffer. Exposure to x-rays increases a woman’s risk of giving birth to a Down’s syndrome baby.⁵³

Although x-ray risk is cumulative over a lifetime of exposure, even single shots are not innocuous. According to the United States’ Health Research Group, a consumer group which reports on risks in medicine, topping the list are x-rays of the upper intestine, which give an equivalent dose to the entire body of 400–800 millirads; the next highest (apart from the risk associated with x-raying the other organs) is the spine (100–500 millirads); stomach, breast and pelvis (100–200 each); skull or shoulder (25–75); chest (20–60); with whole mouth dental x-rays taking up the rear at 10–30 millirads.⁵⁴

In case you are feeling complacent about that low dosage from dental x-rays, a single bite-wing dental x-ray is equivalent to smoking half a cigarette every day for a year. The US Academy of Sciences figures that one barium meal shot of the intestines carries the same risk as smoking up to a pack of cigarettes a day for a year. This means that, with x-rays of the lower back, which some 700,000 people undergo in Britain alone every year, 19 people could die each year as a direct result.⁵⁵

Even if everyone in medicine knows that x-rays are dangerous – possibly dazzled by another of their ‘miracles’, the ability to ‘see’ through living tissue, Superman style – doctors blithely downplay the dangers and make few efforts to minimize exposure when ordering up a set, even on your teeth. Most GPs and orthopaedists have a kneejerk approach to ordering x-rays.

A joint working party established between the UK’s Royal College of Radiologists and National Radiological Protection Board (NRPB) reviewed the existing evidence in 1990 and estimated that up to one fifth of the x-ray exams done in the UK were unnecessary or downright useless.⁵⁶ In one examination of patients given x-rays of the lower back, more than half were absolutely unnecessary⁵⁷ In the US, the Food and Drug Administration reckons that a third of all radiation is unnecessary.⁵⁸

The most common unnecessary x-rays are those of the chest, limbs and joints. This translates into some seven million unnecessary x-ray exams in a single year. The UK’s more modest wastefulness has worrying implications for the rest of the West, since the UK performs only about half the number of x-rays per person as other countries such as France or the US,⁵⁹ where seven out of every 10 people get subjected to at least one x-ray every year.⁶⁰ In Canada the figures are even worse: virtually everyone gets an annual x-ray of some sort.⁶¹ (It’s also no cause for complacency in the UK, since British doctors order twice the number of certain types of x-rays – barium meal and enema – as their American counterparts.⁶²) The NRPB has recently announced that overall radiation in the UK could be halved without reducing diagnostic effectiveness.

For instance, doctors routinely x-ray for back pain, when it has never been found to do any good at all.⁶³ Skull x-rays have a poor batting average in detecting bleeding in the brain,⁶⁴ and even the good old chest x-ray, used to detect tuberculosis, is considered a waste of time by the World Health Organization.⁶⁵ The prestigious medical journal The Lancet admitted that most chest x-rays routinely performed on patients awaiting surgery other than on their heart or lungs were of so little benefit that over a million pounds’ worth of x-rays would have to be done to end up saving a single life.⁶⁶

The decision of whether you need an x-ray or not also depends on the whim of the individual doctor. An audit of nearly a million day and in-hospital patients has shown that referrals for x-ray varied by 13-fold in general and up to 25-fold for chest x-rays, depending on which consultant was in charge.⁶⁷

Because the reproductive organs are susceptible to radiation damage, they should always be protected from exposure during x-ray by a lead shield. Nevertheless, in a Consumers’ Association (Which?) report, in 40 per cent of cases the men surveyed had not had their testes shielded, and women were unprotected two-thirds of the time.⁶⁸ (In a third of cases, no attempt was made to find out if the women were pregnant.) In another study of children, three-quarters of the time the lead shields used to protect the reproductive organs hadn’t been used or placed properly.⁶⁹

Obviously there are times when x-rays are invaluable – particularly when limbs are first broken (though many doctors insist on constant new shots to check the progress of healing). However, even if your doctor is responsible about ‘dose constraints’ – the new buzzword among radiologists for the least amount of radiation necessary for individual snapshots – you still could be getting more radiation than necessary, largely from ageing equipment. The NRPB has reported that patients in some hospitals receive doses 20 to 30 times higher than necessary for obtaining diagnosis from machines that were, in some cases, 15 years old.⁷⁰ Just a few years ago Liz Francis, NRPB information officer, said ‘physicists were saying that old x-ray equipment was giving out doses bigger than Chernobyl’.⁷¹

Even dental x-rays can subject you to unnecessary risks, since they are often performed by untrained staff who can’t use the equipment properly and who may either need to repeat the exercise or will set the dosage unnecessarily high. Two dentists in the West Midlands escaped suspension by their professional body for using untrained school-leavers to take their x-rays when it became clear that dentists throughout Britain were doing exactly the same thing.

As with most tests, there is a strong likelihood of human error in interpreting the results. One study of Harvard radiologists found they disagreed on the interpretation of chest x-rays half of the time. There were significant errors in 41 per cent of their reports.⁷²