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Radiation Levels

nadger
Rising Star
Posts: 4,498
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Registered: 13-04-2007

Radiation Levels

When they have talked about radiation levels in Japan they kept saying it's only the equivalent to one CT scan.
When I had a CT aortagram this afternoon I asked the radiographer how many millisieverts were involved. He said he could give me the exact amount after the scan.
It was 9 millisieverts as I had a fairly detailed acan - cancer scans that I've had give a lower figure.
14 REPLIES
Community Veteran
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Registered: 01-08-2007

Re: Radiation Levels

Whatever happened to Roentegens? - Thats what I thought radiation was measured in.. at least thats what is suggested at the Kidd of speed
I need a new signature... i'm bored of the old one!
pierre_pierre
Grafter
Posts: 19,757
Registered: 30-07-2007

Re: Radiation Levels

Roentegens is X-Ray radiation, Nuclear is measured in The sievert which is is the SI derived unit of dose equivalent radiation. It attempts to quantitatively evaluate the biological effects of ionizing radiation as opposed to the physical aspects, which are characterised by the absorbed dose, measured in gray. It is named after Rolf Sievert, a Swedish medical physicist renowned for work on radiation dosage measurement and research into the biological effects of radiation.
Community Veteran
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Registered: 24-09-2008

Re: Radiation Levels

@ pierre and Okrzynska:- I Can remember programming nuclear calculations based on millirems (roentgen equivalent in man ) back in the 60's , do you know when SI's replaced millirems as the standard?
Seem to remember 3 mile Island was calculated in millirems (but not sure).
One radiation dose that always amused me were BED's (From wiki). A banana equivalent dose (BED) is a defined to be the absorbed dose of radiation due to eating one banana. It is a concept that was intended to explain the relative danger of radiation by comparison with natural doses.
Bananas contain potassium, of which 0.0117% is radioactive.
Community Veteran
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Re: Radiation Levels

I recall something similar to the BED known as a Cornwall Year.  Crazy
(google radon, granite, cornwall)
I think it was the invention of a specific physics teacher though, never heard of it since.  Roll eyes
nadger
Rising Star
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Registered: 13-04-2007

Re: Radiation Levels

I was working from these figures as I've had at least 15 CT scans + several x-rays over past three years.
http://www.bbc.co.uk/news/health-12722435
johpal
Grafter
Posts: 550
Registered: 20-04-2008

Re: Radiation Levels

To the best of my knowledge, Roentgens are not SI units and are considered obsolete; it measured the rate of exposure to radiation (now measured in Grays, if memory serves me well).
The Sievert is a unit of dose (the amount of ionising radiation absorbed by tissue).
Quantities of radioactivity are measured in Becquerels (SI replacement for the Curie)
Simples.
The NHS employs Clinical Scientists, who (sometimes) have a greater knowledge of these units than the humble radiographer.
nadger
Rising Star
Posts: 4,498
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Registered: 13-04-2007

Re: Radiation Levels

I did specifically ask the radiographer about millisiverts.
As each scan is different he was able to be fairly specific after scan completed.
In the news reports they kept quoting 11 millisiverts for CT scan and I was told that this figure probably came from US where they use a higher dosage.
I realise that the scientists should know more but I was talking with a very senior radiographer who's scanned me many times over past 3 years.

johpal
Grafter
Posts: 550
Registered: 20-04-2008

Re: Radiation Levels

@nadger No problem with asking the radiographer; all modern diagnostic imaging machines display the delivered dose and it is a requirement that this figure be stored with the examination images and report, but not necessarily stated.
The radiographer may not necessarily have a comprehensive understanding of  the various units of measurement.
johpal
Grafter
Posts: 550
Registered: 20-04-2008

Re: Radiation Levels

For those advocates of nuclear power, news that the risks attached to such power stations are far from localised:
http://www.bbc.co.uk/news/uk-scotland-glasgow-west-12892383
The concentrations may be minuscule and Iodine-131 has a half-life of approx. 7 days. Again, in minuscule quantites, Caesium-137 will follow and it has a half-life of some 30 years, adding to the natural background radiation levels to which we are all exposed.
Community Veteran
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Registered: 02-08-2007

Re: Radiation Levels

What level of exposure are astronauts subject to for each day in space, anybody know ?
Moderator
Moderator
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Registered: 11-01-2008

Re: Radiation Levels

This reg article seems to to have a more balanced viewpoint.
Was amusing to see everyone run indoors when there was a brief shower today incase the rain was radioactive...
Will Moderate For Thanks
johpal
Grafter
Posts: 550
Registered: 20-04-2008

Re: Radiation Levels

If you have the stomach for it, here is an interesting read:  Wink
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20070010704_2007005310.pdf
The immediate answer to your question is summed in Table 4 at the end of the article (roughly an exposure of 1 mSv per day average, but dependent upon many factors).
Did you know that (former) Concorde passengers suffered a higher radiation dose than those flying transatlantic in conventional jet aircraft? Also, if you go on a ski-ing holiday, at high altitude you are also exposed to (very slightly) higher radiation levels?
Community Veteran
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Registered: 24-09-2008

Re: Radiation Levels

Not being flippent,
How many bananas do you need to eat in a day to get up to 1 mSv
johpal
Grafter
Posts: 550
Registered: 20-04-2008

Re: Radiation Levels

Bananas are rich in potassium (as are Brazil nuts). Potassium-40 is a radioactive isotope of potassium, found, I believe in a fixed proportion in all quantities potassium. Your body contains a certain amount of potassium. If you ingest a banana, an equivalent amount of its potassium content will be excreted from your body.
Yes, bananas are radioactive, but the net effect of eating one does not add to your dose of naturally occurring radioisotopes already in your body (well, only briefly until nature takes her inevitable course).  Wink