Gamma Spectrometry Forum

Hello,

currently i am writing a report about a few incidents where the Terac-25 radiation treatment device irradiated at least six people and i want to ask if the following incident could be possible with electron radiation.

In the first accident, a woman developed red marks on the skin on her breast and her back after she was radiated from the front to cure breast cancer. The dose was estimated to be somewere between 150 and 400 gray electron radiation. The energy choosen for the treatment was 10 MeV.

The device is only able to produce 25 MeV electron radiation or X-Ray. My sources think, that the injury are caused by electron radiation, but would it be possible for electrons to penetrate through the breast and thorax and produce such a high dose at the skin on the back to redden it with only 10 MeV or even at 25 MeV? If so, wouldn't the dose so high to instantly kill the skin on the breasts instead of reddening it?

I only found one german source about the penetreation dept of electron radiation in water (page 3 http://wwwa1.kph.uni-mainz.de/Vorlesung ... nar/A1.pdf).
Does someone of you know if i can compare water with fat, flesh, bones and the lung?
Can someone link me a reputable source or person to ask about the biological effect of these doses of radiation to the skin?

The reason is: If it was not electron radiation that produced the reddening, it was x-Rays. that would mean that there is another, not found bug in the Therac-25.

greetings

Felix

Hi Felix,
Indeed a lot of incidents were reported with this equipment. Main problems were related to using the wrong software and also the failure of hardware resulting in a wrong position of the selector for X-ray/electron beam exposure. These failures resulted in settings where patients were exposed to the highest level of X-ray radiation, i.e. 25 MeV.
Water-based models are a good representation for biomaterials and as such it can be shown that electrons have short pathways in these materials. X-rays have long range character.
Main problem seems to me that from the high exposition of 25MeV X-ray settings many secondary (high energetic) electrons are generated (Compton effect) and these transfer their energies in short-range exchange, resulting in local tissue damage by thermal effects, generation of radicals, so destroying cells, etc.
greetings
Willem
Additional Note:
The mechanism for curing cancer is actually the same as described above; the difference here is that at 25MeV this is 125x the normal "healthy" dose. Starting from 25MeV on, the secondary electrons have a higher (kinetic) energy and so have a deeper penetration and destructive power as the electrons have at normal dose settings. At "normal dose" MeV and electron mode setting the only aim is to destroy the carcinogenic cell tissues and dna of these cells only. Setting the right energy level and focusing the electron beam together with right time settings is the aim for the professional. Side effects as burning of tissue cannot always be avoided, but have to be minimized anyhow.
Literature Ref: Hanno Krieger, Strahlungsmessung und dosimetrie, Springer Spectrum, 978-3-658-00385-2, also as e-book available.