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X-rays: Too much of a good thing?

The invention of x-ray and ultrasound technologies has had one important negative consequence in India -- sex-selection, with the sex ratio in places like Chandigarh down to 773:1,000. There is another: over-investigation and over-exposure to radiation. With the number of CT scans quadrupling since 1992, as many as 2% of cancers could now be attributable to radiation exposure, writes Sanjay A Pai

Of the many technologies that have had an impact on medicine, the development of radiology and imaging stands out as unique. There are many reasons for this: the discovery of x-rays was a serendipitous one; the exact dates on which the discovery was made are known; the application of a new field of medicine was immediately obvious to doctors and the public; and the application of this technology to medicine was done almost immediately after the discovery of x-rays. Besides, the new technology entered the minds and lives of the common man in more ways than one would have expected in the early years, while much later, additional developments in the field brought other changes in our lives. Changes that perhaps would not even have been dreamed about at the time of the development of the first x-rays.

Discovery of x-rays

Wilhelm Conrad Roentgen was director of the Physical Institute at the University of Wurzburg, in 1895. On November 8, 1895, Roentgen was working in his laboratory with a cathode ray tube when he noticed some fluorescent rays at a distance that was greater than expected for cathode rays. Roentgen was clever enough to realise immediately that he had stumbled across a new type of ray (a form of electromagnetic radiation) that was hitherto unknown to man. He spent the next six weeks in his laboratory working at a feverish pace to identify the ray. He found that the unknown rays, which he called “x-strahlen” penetrated many materials, but not lead. Importantly, he realised that the rays blackened photographic plates and produced shadows of bones.

On December 28, 1895, Roentgen submitted his paper ‘On a New Kind of Ray -- A Preliminary Communication’ to the Proceedings of the Physical-Medical Society, of the University of Wurzburg. On January 1, 1896, he sent copies of the paper to colleagues and friends in different parts of Europe. One of these friends was Franz Exner in Vienna. Exner exhibited the paper and images to some of his friends at a party in his house a few days later. One of them was a physicist, Ernst Lecher, whose father, Z K Lecher, was editor of the newspaper Vienna Presse. On January 5, 1896, Vienna Presse carried on its front page an article describing the discovery and, more importantly, suggesting that this new wave might be useful in medical diagnosis. On January 6, 1896, the London Standard cabled the news around the world. The New York Sun and later the London Standard were quick to suggest the medical potential of the wondrous ray.

Roentgen received 1,000 letters within a week, and over 1,000 articles were written on x-rays in the first year itself.

It was not long before x-rays began to be used in medicine. The first medical x-ray was used to diagnose a Colles’ fracture (a fracture of the radius, one of the bones that make up the forearm) on February 3, 1896, by Dr Gilman Frost, with the assistance of his brother Edwin, an astronomer.

How important is the discovery of x-rays? What do the experts feel? Andras Gedeon, in ‘Science and Technology in Medicine’, includes x-rays among the 99 most important technological advances that have contributed to medical science since 1528. Eugene and Alex Strauss place it as the 11th greatest advance in medicine out of the 100 most important concepts in medicine that they enumerate in their book Medical Marvels. They consider advanced imaging techniques such as CT, PET, ultrasound and MRI as the 49th greatest such advance. However, Meyer Friedman and Gerald Friedland, in their book Medicine’s 10 Greatest Discoveries rate the discovery of x-rays as one of the top ten discoveries. The Nobel committee awarded the first Nobel Prize in physics -- in 1901 -- to Roentgen. Finally, not just experts but laypersons agree: in November 2009, nearly 50,000 people voted that x-rays were the greatest modern scientific discovery.

Those who have seen the 1980s movie The Gods Must Be Crazy will recall the amusing plot where a group of happy, content African tribals come across an empty bottle of Coca-Cola and find the bottle so useful in their daily activities that they cannot imagine life without the omnipotent empty Coke bottle! Certainly, all of us have experienced similar things with respect to newer technologies -- in recent years we have often wondered how we were able to live life before the worldwide web, or digital photography, or cell phones! A hundred years ago, it appears that it was x-rays that filled this breach.

Because x-rays were the hottest thing in the news, and everyone was aware of the almost miraculous powers of these wonderful rays, unscrupulous businessmen used the word x-rays indiscriminately and unscientifically to sell their goods. None of them had anything to do with x-rays of course! Thus, we had x-ray whiskey which was “scientific, substantial, beneficial”, an x-ray coffee bean grinder, x-ray blades (“the finest blades known to science”), x-ray dry batteries, x-ray flashlight batteries, x-ray cream furniture polish, x-ray soap, x-ray golf balls and x-ray headache tablets! There was also some fear about the possibility of the new ray invading people’s privacy -- a London firm attempted to sell lead underwear!

The plain x-ray, of course, still remains a very useful diagnostic tool. Variations of the x-ray such as Barium meals and Barium follow-through (where a patient swallows a paste of Barium radio-opaque material which lines the lumen of the gastrointestinal tract and delineates it, thereby helping diagnose conditions such as tumours, ulcers, etc), fluoroscopy, etc, have also proved immensely useful over the years.

After World War II, use of the ultrasound machine made significant contributions to the practice of medicine. The ultrasound, developed during the war, works on the simple principle that sound waves bounce after hitting an object. This, of course, is the principle that bats use to fly.

Ultrasonography, in particular, has entirely changed obstetric practice. This is largely because it is safe and does not emit radiation, as do x-rays and CT scans, which may be unsafe. It is now routine to perform serial scans on pregnant women to evaluate the growth rate of the foetus, check for congenital anomalies, etc.

In India, however, this great advance has an important negative social consequence: sex-selection. It is not uncommon for Indian parents to desire boys rather than girl-children. In many parts of India therefore, particularly in the north, female babies are aborted. In Haryana, this has reached a stage where the state’s female:male ratio is an alarming 861:1,000. In Chandigarh, the capital of Punjab, which has a literacy rate of 81% and among the highest per capita incomes, the sex ratio is 773:1,000. This skewed ratio has led to a drastic decrease in the number of marriageable girls in Punjab and Haryana -- with another alarming consequence, that of bride trafficking. Guesstimates suggest that there are about 50,000 trafficked brides in Haryana, many of them from Orissa, West Bengal and Jharkhand. Because sex-selective abortion was particularly high among Sikhs, the Sikh clergy in 2001 issued an edict threatening social ostracisation of Sikhs who practised sex selection.

Today, it is illegal for a radiologist to disclose the sex of the foetus during an ante-natal scan of the mother. A law, the PNDT, or Pre-Natal Diagnostic Techniques (Regulation and Prevention of Misuse) Act, has been introduced to counter the practice. In fact, radiologists are required by law to disclose that they have not revealed the sex of the baby to the parents on every scan that they perform. Disclosing the sex of the baby is punishable by law and can result in imprisonment of the radiologist. In the West, of course, where such a problem does not exist, one can learn the sex of the foetus in the second trimester, thus taking away the fun and anticipation of not knowing whether one is the parent of a boy or a girl some months down the line!

There are other problems with x-rays. While the marked overexposure to x-rays amongst radiologists and technicians that took place a century ago no longer exists, patients who undergo many x-rays still get overexposed to the rays. (One early victim, albeit on a small scale, was Thomas Alva Edison who experimented with x-rays and found that he developed sore eye!) A single CT scan or nuclear medicine study, for instance, can deliver an effective dose of 10-25 millisieverts (mSv). Compare this with an estimated annual background radiation dose of 3 mSv per year. A single chest CT may have a dose of 8 mSv -- the equivalent of 400 chest x-rays.

Excessive radiation could lead to cancer. Thus, x-rays, while usually beneficial, can be a double-edged sword: too much exposure could potentially lead to cancer. A recent editorial (August 27, 2009) in the New England Journal of Medicine by Michael Lauer states that the number of CT scans has quadrupled since 1992, and that perhaps as many as 2% of cancers could now be attributable to radiation exposure during CT scanning. Also, the number of myocardial perfusion scans increased by 6% per year between 1993 and 2001. Myocardial perfusion scanning leads to more radiation exposure than any other procedure, yet there have been no studies that have shown any benefit of this investigation in improving health outcomes! Physicians remain complacent merely because it is difficult to accurately measure the risk associated with radiation, and because the cancer, if it develops, does so many years after exposure to radiation and cannot obviously be linked to imaging in the past. 

Besides this obvious problem, there is another lesser known one (lesser known to the layperson at any rate). Imaging, like most other things in medicine -- and in life -- has its limitations. Screening for cancer and other illnesses is common nowadays, and health checks, with all their naysayers and proponents, are here to stay. Apart from the unnecessary radiation that, say, a ‘routine chest x-ray’ subjects a person to -- with no medical indication -- imaging sometimes throws up false positive results where non-diseases are identified as diseases. The best known examples of this are in screening mammography and in abdominal ultrasonography. In screening mammography, a study by Elmore and his colleagues, published in the New England Journal of Medicine in 1998, showed some discouraging findings. They carried out a ten-year retrospective study of 2,400 women and found that 9,762 screening mammograms and 10,905 screening breast examinations were performed, with a median of four mammograms and five clinical breast examinations over the ten-year period. Of them, almost 24% of the women had at least one false positive mammogram -- compared to just above 13% of women who had a false positive clinical examination! The false positive tests resulted in 870 out-patient appointments, 539 diagnostic mammograms, 186 ultrasound examinations, 188 biopsies, and one hospitalisation. They estimated that among women who do not have breast cancer, over 18% will undergo a biopsy after 10 mammograms, and 6% will do so after 10 breast examinations. Further, for every 100 dollars spent on screening, a further 33 dollars will then be spent to evaluate the false positive cases. It goes without saying, of course, that many of these women will undergo severe psychological stress because of the possibility of their having cancer.

Medicine has ceased to be merely a healing profession. For many, medicine is now a business, and the proliferation of private hospitals and imaging centres is clear evidence of this. For many, the bottom line is profits, and this can have adverse effects on the patient’s health and rights. It is well documented that physicians who own imaging centres tend to over-investigate their patients. There may not be a conscious desire to do so; it could be a subconscious or reflex act, or part of a defensive culture. Or it may just reflect the fact that physicians are human. However, with every additional imaging done, the patient is exposed to unnecessary radiation (of course, this is true in any hospital not just in a private hospital).

At a time when patient safety is the buzzword in the West -- and is a topic that’s being addressed even in India -- it is time to take appropriate steps. Hillman and Goldsmith, writing in the New England Journal of Medicine (2010) believe that the medical school curriculum would be a good place to start. They are correct. Medical students are rarely, if ever, educated about the risks of x-rays. Most teaching in radiology, in India at any rate and probably in the West too, revolves around identifying classic images and making diagnoses. What’s lacking is a holistic approach to the science. Given that very few students will become radiologists (who will, hopefully, have at least some idea of the dangers inherent in x-rays), while many will embrace general practice (meaning an end to their formal education), this is the best time to introduce the idea that x-rays can be harmful.

It is also imperative that associations and government agencies show enterprise and try to reduce unnecessary radiation. There is evidence that diagnostic accuracy does not necessarily decrease when the radiation levels of a CT scan are reduced; this suggests that research needs to be done to establish appropriate cut-off levels of radiation. It is also the duty of medical and health professionals to educate the lay public about the hazards of unnecessary radiation.

The amazing advances in technology, particularly in the fields of communications and software, over the past two decades, have led to a new field: teleradiology. Teleradiology is the transmission of radiologic (x-ray or scan) images by electronic means to another geographical location where a radiologist can see the image and interpret it. The advantages of this are obvious: areas which do not have a specialist radiologist (smaller towns or villages) can enjoy the benefit of an expert opinion from a big centre, at very little cost. But there are those who argue that teleradiology, already a specialty where patients often do not come in contact with their radiologist-physician, is separated from its patients by an even greater, unfathomable chasm. Moreover, the field is relatively young and Indian medical laws are probably still unclear on medico-legal issues with respect to consent, error, malpractice, etc.

Finally, teleradiology leads to an unusual situation. We are experiencing the outsourcing of radiology and other images from American hospitals to radiologists in India. The time difference between the two countries -- and the high cost of medicine in America -- means that a radiologist in India can interpret an image and send back a report even before his American counterpart gets to the hospital in the morning to see the previous night’s x-rays and images. And we have the West lamenting American jobs being lost to India (‘Bangalored’). Can this be interpreted as unfair, even unethical? It is of course delightfully ironic that this is the reverse of what has been claimed over the years: that the brain drain, when talented young doctors and other professionals migrated to affluent countries, was unethical because it deprived developing nations of their very best minds!

The discovery of x-rays changed the face of medicine. X-rays and further advances in the field -- ultrasonography, CT scans and MRIs, among others -- have led to better precision in diagnostic radiology. Interventional radiology -- where the radiologist sometimes plays a therapeutic role as well -- is yet another development.

All of these advances have, however, not been without their associated problems. We are grappling simultaneously with changes in our approach to healthcare -- but almost always at greater expense, sometimes complications, and occasionally with no evidence at all of better outcomes.

(Sanjay A Pai is a Bangalore-based surgical pathologist with an interest in the history of medicine)

Infochange News & Features, December 2010