"The potential for medical diagnoses was rapidly put to use and by the turn of the century x-rays were being used routinely to diagnose a range of medical conditions. However the rapid application of x-rays led to the rapid realization of the hazard associated with its use. It was found that excessive radiation led to serious tissue damage and death.

The effects of radiation are out of all proportion to the amount of energy deposited, for example, a single dose of 10gray given to the whole body will kill almost anyone who receives it, unless they are given a bone marrow transplant. However, 10gray deposits only 10 Joule per kg of tissue (1 gray = 1 Joule/kg). You should easily be able to calculate that 10 J/kg represents a temperature rise of only 0.003 deg C, (remember that the bodies specific heat is 3500J/kg/K). Why is radiation so damaging? The main reason is that it produces ionization of the material that it passes through. Thus, chemical changes may occur which are extremely harmful to the body. For example, ionization can convert safe ions to extremely toxic and dangerous materials."

My own example: Sodium is present in all our tissues as the ion Na+ and is necessary for the transmission of nerve impulses. However, Na metal is toxic to the body in even tiny doses. Na and Cl are both toxic, but if you take one electron from Na and add it to Cl, you get common salt.

"A dose of 2 Gry will cause sickness in a substantial portion of the population (25%) while 10 Gry will cause eventual death for most.

Exposure over a long time to relatively low doses may result in the induction of cancer. In fact, this and genetic damage are the only known effects of very low doses of radiation.

Cancer is the most likely consequence of radiation and it is believed that any dose of radiation no matter how small will have a probability of inducing cancer. There is usually a delay of 5 to 10 years between the exposure and the induction of cancer. One Gry of radiation to the whole body will give a probability of cancer of about 4% for adults and rather more for children. This risk is additive so that multiple small doses over a number of years will give the same risk as from the total dose given on a single occasion. (Provided that the total dose is not too high).

Random genetic risk is approximately 1% for each Gry of irradiation. etc., .......

Radiation is commonly used in medicine, in fact medical exposure is by far the largest man made source of radiation. It far exceeds all other sources of exposure such as nuclear reactors, nuclear explosions or the industrial use of radiation.

Examples of the use of radiation in medicine are: simple chest x-ray 1mGy (skin) abdominal x-ray 5mGy (skin) pelvis x-ray 5-10mG (skin) CT scan 10-20 mGy (per slice) angiography 10-100mGy (skin) nuclear medicine 10-20 mGy (specific organs)

Therapy 20-50 Gy (treated volume)

Thus it should be evident that radiation is dangerous and that no dose of radiation is totally safe, yet its benefits cause it to be used routinely in medicine.

The first point to note however is that mankind has been subject to natural radiation throughout the whole of history. The earth is radioactive and so is each and every person on it. There are parts of the earth where the radiation level is quite high either due to the radioactivity of the earth in that area, or due to the increased cosmic radiation which occurs at altitude. On the Darling Scarp (just outside Perth) there are areas where the natural radiation level is about 5mGy per annum. If you fly in a jet the radiation level rises to about 5UGy per hour. Thus a round trip to Europe represents an additional radiation dose of about 0.2mGy." (Of course this if from Perth in Western Australia.)

HALF HOUR BREAK HERE AS I HAD TO GO OUTSIDE AND HELP MY HUSBAND DELIVER A CALF. . . .

Now back to the mini-lecture!!

"Important rules to keep in mind are:

1. Radiation should only be used where the the benefits exceeds the risk to the patient. For most uses of radiation, safety limits are applied to protect workers or the general public. With the medical use of radiation no such safety levels are prescribed. The matter is entirely in the hands of the medical profession so it is important that they are knowledgeable concerning the hazards of radiation.

2. The dose of radiation should be minimized by using it in an optimal manner. This is of course only relevant to those practitioners who actually make direct use of radiation.

3. If in doubt, consult an expert. For example,. a radiologist, to advise on the efficacy of a particular investigation or a radiation physicist, for foetal dose calculations and risk estimates. There have been two recent examples where GPs have advised patients to have an abortion following a minimal exposure to radiation. This represents an extraordinary level of ignorance both as to the risks involved and to the availability of expert advice."

Another thing is that Radiation risks are tallied and calculated over a population. What this means is that if 1 million people have a chest x-ray (5mGray each), the total dose of radiation administered to these people is about 10Gray, and one of these people will die as a result of radiation induced sickness. What this means is that in a population the size of Australia (20 million), 2-3 people die each year of radiation induced cancers and genetic damage. A population the size of the US would give even worse figures. The advent of ct scans has made it even worse. 2-3 people per year in Australia will die as a result of them.

I'm not sure if this is enough information to give GPs who can send people for all sorts of radiation based tests, but I know that those who actually practice in the field do a lot more study as to the effects and dangers of radiation. I believe that doctors are well aware of the dangers of radiation, whether they choose to admit that they may be partly responsible for causing a disease in their patients is, I suppose, a matter of choice for the individual doctor.

There is a category of morbidity and mortality that is attributed to "Iatrogenic" causes in statistics. This is just a nice way of saying that the person died of complications associated with treatment given by the medical profession. A high percentage of deaths in hospitals are attributed to "Iatrogenic causes". Of course, the general public reading these figures will have no idea that the number of deaths directly caused by "treatment" is so high. I think it is a terrible way of presenting statistics to people, and interferes with their right to give "informed consent". I don't suppose that many of my colleagues feel the same way.

Regards