Siobhan,
To answer your question about shielding the eyes.... in most cases, it is not advisable to shield the eyes during a radio-logic scan of the head because the shield would have to be lead lined which would deflect the rays from penetrating the underlying areas that need to be exposed to the rays.
Doctors and technicians tend to verbally diminish the radiation exposure because of these reasons.... 1) they are not sure what the exact amount of the radiation exposure is... 2) they do not want to frightened the patient into not doing the scan. Keep in mind that anyone who performs radiography on a routine basis is going to be concerned about the radiation exposure as they themselves are being exposed repetitively. So it is in their best interest, as well as the patients, to use the equipment wisely by calibrating the settings to the least amount of effective radiation exposure as possible.
Also, everyone's body reacts a bit differently to radiation as it depends on their lifestyle, diet and medical history. Someone who works in or lives near an industrial complex for instance is going to have a high level of radiation exposure on a daily basis. Add to that a poor diet and/or poor health and their system is not going to rid itself of the toxicities from the radiation. The toxicity of radiation is cumulative. Meaning the more intense and repetitive the exposure one has the more it will accumulate in the tissues of the body. In healthy people, infrequent xrays are not going to accumulate in the tissues as there is reprieve in between exposures and their healthy diet helps them to rid the body of the radiation.
Regarding the calculation of radiation being given to each patient...
Again there are factors to take in to consideration with each patient. Most often the machines are already set at the lowest effective dose. Which is pre calculated by the manufacturer based on physiological factors, etc. The technician usually has the ability to alter the exposure time and intensity of the rays if needed. Some facilities may require that the setting amounts be recorded in the patients notes. Some machines may even imprint the calibration of exposure on the report.
Bryanna
Quote:
Originally Posted by Siobhan
OK, I've been "studying" this, so for anyone interested, this is what I figured.
1) The referring doctor will usually play down the radiation levels, and especially the technicians doing the test. The usual comparison to background radiation or to airplane flights is totally unacceptable since they are trying to compare apples and pears.
It is only that certain (scientific or other) authorities and studies will play a different song - radiation in medical imaging is simply quite a concern.
2) The so-called "effective dose" is indeed a flawed concept. It basically looks at the received (or should it be "given") amount of radiation and then calculates (averages) it over the WHOLE body, even when only a small section is scanned (eg. sinuses). To me, this is very wrong (or I have misunderstood the concept).
Different tissues absorb radiation at extremely different levels. Each tissue type has a 'tissue factor' assigned to it. Then they add up all tissues in the body (each multiplied by the tissue factor) and that is your effective dose (also considered is the age and sex somehow - they don't say how). So for some tissues, actual absorbed dose can be 40 mSv, and those tissues are small, but for other, large areas ("tissues"), the dose might be 0.1 Sv. So your lens receive massive amounts of radiation, but they tell you your head CT scan was "only 2 mSv". Scan area is say 30 cm square, but they average the radiation dose over the whole body.
I am also wondering if radiology technicians are required by law to record the exact parameters they adjusted/used for each test, or is this recorded automatically and can't be messed with. Or is it machine-specific?
Are these parameters and doses received (however flawed they may be) easily given to patients?
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