Exposure to radiation in the workplace is controlled by the Ionising Radiations Regulations 1999. Under these Regulations an employee of 18 years or over is limited to a radiation dose of 20milliSieverts (mSv) in any calendar year. If a person receives a dose greater than this permitted level then an immediate investigation must be carried out into the causes and the overdose reported to the HSE.
In each session Deb is receiving a dose of 1.8 - 2.0 Grays (Gy) of X-ray radiation. The total dose she will receive during her radiotherapy is 55 - 60 Gy. (Don't worry about the units; Sieverts measure the dose received, Grays measure the effect that dose has on the body i.e. to choose a boxing analogy Sieverts measure how hard you are hit, Grays whether you are knocked out or not. For gamma and X-ray radiation Sieverts and Grays are the same i.e. 1 Sv = 1 Gy.)
So in one session Deb is receiving a dose of 2 Gray or 2000 mSv that is 100 times the radiation exposure permitted in a whole year by the radiographers carrying out the therapy. Scary eh?
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