I measured electron dose with TLDs which was calibrated in photon beam. I want to check my results with the results measured by TLDs calibrated in electron beam. I am not convinced myself with the result. Does anyone has data ?
My first very prompt response is, if you have calibrated with sufficient high photon energies, the dosimetric "work" has been done by the secondary electrons, so you don´t have to expert different behaviour because of LET. The whole procedure depends of course from TLD material, I suppose you have used small chips or sticks of LiF and have taken care not to integrate the dose signal over a too large volume. May be you could give some more hints?
Hi Suraj, What type of TLDs did you use? TLD100 (LiF:MgTi) generally does not show difference in response to both high energy photons or electron i.e. TLD100 calibrated in 6 MV x-rays can be used for 6-15 MeV electrons without any significant correction for over or under response.
Look at the interesting papers of Shakardokht Jafari here in RG. A lot of principal statements. And you should try to read Oberhofer/ScharmannApplied Thermoluminescence Dosimetrie.
Good references. I might add Thermoluminescence Dosimetry Materials:Properties and Uses by McKeever, Moscovitch and Twonsend and Thermoluminescence Dosimetry by McKinlay. Both are very good reference books for any one involved in TL dosimetry.
TLDs work fine for both electron and photon beams, as long as you use them in the same energy, beam condition, set-up condition, calibration and annealing condition. You should expect 10% uncertainty. I used TLDs for five years back to 2002. TLD is convenient, but labor intensive and also not very reliable. If you use TLDs not for tiny region dosimetry like brachytherapy seed parameters measurements, EBT films would be better than TLDs in dose measurements.
Thank you Zhang, Nelson and Krieger for your answers. I used TLD-100 which we expect to show about same response for electron, photon and neutron. In my research i used those TLDs which were calibrated in Cs-137 beam. The doses were measured outside the treatment area. I got really small doses for all points of interest for 6 Mev electron beam than photon beam with same energy.I believe that , it can be due to high LET of electron in the medium but really want to compare data of doses measured by TLDs which are calibrated in electron beam.
Dear Suraj,
it would be interesting to see some results. The obvious difference of electron and photon doses outside the irradiation field is surely no problem of calibration factors. It´s depending on the distribution of scattered secondary particles (electrons or photons) and their "range" in tissue. If you could deliver some more details about your irradiation geometry (as sketch or in some other way) we could start a discussion again. The high LET of electron occurs an the final end of the electron path when the energy is lower than a few hundred keV. The residual range in this energy region is about mm only.
I agree with Hanno, more information is needed. I have calibrated TLDs in electron beams at different depths of material. Dose is highly depth dependent. If you have a full 6 Mev beam incident on an unshielded TLD, a thin TLD will be nearly uniformly irradiated. The thicker the TLD the less uniformly irradiated. A Cs137 calibration will be essentially uniformly irradiated. The Cs137 calibration is the average over the TLD volume. The lower the energy of the electron, the less valid is the Cs137 volume calibration.
You say, "The doses were measured outside the treatment area. I got really small doses for all points of interest for 6 Mev electron beam than photon beam with same energy."
Please provide a sketch, depth of TLD in material, thickness of TLD, and type of material.
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