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Eye131
USA
1 Posts |
 Posted - 04/05/2017 : 16:57:18
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I have a patient at the university hospital I work with who bought the "GQ GMC-300E-Plus" off amazon.
They were concerned about their children being exposed to the nuclide therapy they were given. So they got a GM system (as stated) off amazon.
I'm trying to help them by figuring out how this system responds. I work with a more than 1 curie Cs-137 calibration source and calibrate instruments at work. Most systems such as Ludlums 44-9 ( h**p://services.ludlums.com/component/virtuemart/radiation-detector-185-detail?activetab=specifications&Itemid=0 ) have an energy response curve. This means if you get 1000 cpm detected of say Tc99m then you are actually getting 2000 cpm when corrected to the varying response from given incident energy.
I cannot find any information on the response curve or detector sensitivity. As such it is kinda useless as a monitoring or survey device.
It says on the store page "Three points calibration. For CPM to uSv/h and mR/h conversion"
What are the three points? The dose per cpm differs depending on the nuclide. Am I just missing where the pdf download for the manual is? |
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Distelzombie
Germany
202 Posts |
Posted - 04/07/2017 : 09:15:32
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Three different calibration points. For different values of cpm and the corresponding ySv/h.
A perfect explanation has not been given to us. However ZLM, who works for GQ, has answered this in thus thread: ://www.gqelectronicsllc.com/forum/topic.asp?TOPIC_ID=4204
It was NOT very conclusive though. I guess it is for mimicking energy compensation, like what you described. |
GMC-300E+ V4.20 with sbt-11a alpha tube
My statements are "stuff-a-hobbyist-says" and not in any way professional. |
Edited by - Distelzombie on 04/09/2017 12:52:53 |
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| Reply #2
ullix
Germany
1171 Posts |
Posted - 04/10/2017 : 10:11:43
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@Eye131:
That Ludlum thingy cost $2000 plus the electronics of perhaps another kilobuck. Don't expect you can get an equivalent for $100.
Their energy response curves are quite elaborate. I have never seen anything near that for the GQ devices.
What exactly is it that you want to measure - are the children receiving radioactive something that they need to swallow or inhale or a being injected with?
Or are they receiving a gamma (or beta) radiation treatment, whereby a big hospital device directs some radiation "beam" (of gamma or beta particles) to their bodies?
In the latter case the children will NOT becoming radioactive at all! The exposure is over once the children are removed from that beam, and you won't measure anything even with the best detectors, because there isn't anything.
In the former case it depends what they get. Beta radiation might be completely absorbed inside their bodies, or only measurable in urine or feces. And if that were the case, the hospital would treat that as radioactive waste.
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Distelzombie
Germany
202 Posts |
Posted - 04/10/2017 : 11:35:00
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| If they'll get a technetium scintigraphy they'll be glowing like crazy for hours. Easily maxes out the GQ GMC. But its not very harmful. |
GMC-300E+ V4.20 with sbt-11a alpha tube
My statements are "stuff-a-hobbyist-says" and not in any way professional. |
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Isotope-235
USA
1 Posts |
Posted - 01/04/2020 : 22:29:42
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I want to calculate disintegrations per minute of a source. Using CPM, I will have to have the detector efficiency.
I am trying to find the efficiency for my GCM-600. It has a Pancake SBT-11 Detector.
Please Help |
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| Reply #5
Damien68
France
780 Posts |
Posted - 01/05/2020 : 00:59:59
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I understood that it was his patient who received radiotherapy, for example isotopes of iodine for the thyroid. and he doesn’t want to hurt his children with it.
basically, if we consider the source as a point, i thing that desintegration per minutes (of source) / CPM (measured) = (4 x pi x r x r) / (S x alpha)
with: r is distance between source and detector
S is effective surface detection of SBT-11
alpha is SBT-11 detection (absortion) probability
alpha is function of particule and his energy
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Mastery is acquired by studying, with it everything becomes simple |
Edited by - Damien68 on 01/05/2020 10:50:48 |
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GM response curve and relative efficiencies
