industry, government or the medical profession,’ says Dr Charles Burton.76
It took patients with myelogram-induced LSAA bringing legal suits against the manufacturers before anyone else took notice. In the UK, the Arachnoiditis Society has some 1,000 members, and a class action suit was taken against Glaxo. After detailed negotiations, Glaxo reached a settlement with the 426 plaintiffs of £7 million, without admission of liability.
The water-based dyes now being used instead are not without risk. One woman being investigated for sciatic pain (back-caused leg pain) with iopamidol (Niopam 200), a water-soluble contrast medium, was immediately rendered paraplegic,77 as was another middle-aged woman given a myelogram with itohexol (Omnipaque), another water-soluble dye.78 Dr Burton says that some new mediums have caused such pain that the x-rays have had to be performed under general anaesthesia. ‘The medical profession has not yet succeeded in finding a benign, effective myelographic medium,’ he says.79
BONE SCANS
Besides looking for broken bones, x-rays are now being used to screen for osteoporosis. That might be a good idea – if we had a test that could be relied upon to deliver an accurate result. The problem is, as many medical experts agree, that even the latest techniques in bone scanning should be interpreted with caution, since changes in bone mass may not signify anything.80
The instruments are imprecise, multiple measurements may be wrong, even the assumptions upon which we scan bone are open to question – for example, the very notion that bones have a density that can be measured or that we can treat it and effectively reverse bone loss.
The latest souped-up bone scan is the ‘dual energy x-ray absorptiometry’ or DEXA – a fancy sort of x-ray. Again, you are injected with a radioactive liquid beforehand, then asked to lie flat on a table while you are scanned for between a half-hour to an hour or even more if a full three-dimensional shot is required. Measurements are usually taken from the spine, hip, spine, heel and forearm.
But an accurate reading in this technique can easily be knocked off. ‘A walk around the room causes the measurement to change by up to 6 per cent (at the hip), which corresponds to six years of bone lost at the usual rate,’ says Susan M. Ott, associate professor in the Division of Metabolism, University of Washington in Seattle.81 Poor machine quality-control and a high percentage of operator error also throw off results.
The favoured technique, measuring many different areas of the body at the same time – one shot of the top of the leg produces five separate measurements, for instance – also increases the risk of a false-positive reading.
‘Apparently dramatic changes can be taken as indicating improvement or dramatic bone loss but may simply be due to the precision of the measurement and poor repositioning technique,’ wrote David M. Reid, a rheumatologist at City Hospital in Aberdeen, Scotland, and his colleagues.82
Studies show that DEXA tests are not necessarily very accurate. In one study, the scans failed to detect osteonecrosis in one-sixth of confirmed cases.83 Extremes in weight (under- or overweight), age (over 60) and arthritis can throw off the result of a test. In fact, the entire exercise of measuring bone mass may be useless, because bone mass doesn’t necessarily have anything to do with bone strength. For instance, fluoride causes bone mass to increase dramatically, but decreases its strength. This is why elderly populations in highly fluoridated communities show an increase in osteoporosis. Similarly, some drugs may increase bone mass by 5 per cent, but because bone structure has been damaged, it isn’t strengthened with the drug. New research shows that only half the people considered to be at most danger from a fracture because of their reduced bone density will actually suffer one.84
It’s important to understand that bone in healthy individuals is a dynamic entity, constantly undergoing interior remodelling. Two sets of cells are responsible: osteoclasts – the construction workers – which rip down the worn-out bone; and osteoblasts – the architects – which utilize calcium, magnesium, boron and other minerals to build up healthy new tissue. This process is called ‘resorption’. All that the usual drugs for osteoporosis such as oestrogen, calcitonin or etidronate (called ‘antiresorbing drugs’) do is to slow this process of turnover and renewal, preventing the hardhat osteoclasts from doing their job. Eventually, there is no further bone formation.
Some researchers argue that the presence or absence of low bone density is a meaningless indicator of risk of fractures or osteoporosis.85 In one nine-year study of 1,000 middle-aged women, the group considered at high risk of osteoporosis actually had fewer fractures than the group not considered at risk. Bone-density screening has also never been shown to be effective in preventing fractures, according to a large review of published work on bone-density screening.86
Bone scans may have a one-time use to help in diagnosing women suspected clinically of osteoporosis, but appear to be too variable to be relied upon as a general screening test for women without symptoms.
CAT SCANS
As with most other industries, the advent of the computer has taken the medical x-ray business to a new level. In the 1970s, computed axial tomography, now usually known as CAT, or CT, scans, revolutionized diagnosis, particularly of bones, blood vessels and soft tissue of the body, offering pictures with up to 20 times the detail of ordinary x-rays. It has now made it possible to scan for diseases of the abdomen, lung, heart, liver and pancreas, and even for early osteoporosis.
Adapted from an image-processing system developed for the Apollo moon landings, CAT scans take a 360-degree series of cross-sectional x-ray images from multiple angles – up to 30 shots – by passing a pencil-thin beam through a particular portion of the body, sometimes with the use of a contrast agent. An X-ray tube on a moveable ring revolves around your body, taking individual ‘slices’ of images.
This information is then passed through a computer, which reconstructs the slices into a three-dimensional image on a video screen, allowing the operator to see this portion of the body from any angle. It is also stored so that the doctor can take photographs of the video screen or call up the information in the future. Your problem is that now that your doctor has computerized diagnostic toys at his disposal, he’s more likely to want to play with them. Although doctors have attempted to claim that CT scanning reduces the need for other tests such as brain scans, arteriography or exploratory surgery, this may be a false saving.
While no doubt CAT scanning represented the height of 20th-century technology, it also poses far more risks than most other tests, blasting you with far higher doses of radiation. In 1991, the NRPB concluded that CAT scans accounted for only 2 per cent of the total UK x-ray examinations but 20 per cent of the overall collective dose, and so were the largest single source of exposure from x-rays.87 This risk is magnified if you don’t stay stock still during the half-minute or so of the test and it has to be repeated. In Japan nearly one-eighth of the population was getting CT-scanned as far back as 1979. Radiation from a single body shot is now considered comparable to that of the low-dose atomic bomb survivors from Hiroshima.
