[fluka-discuss]: High resolution x-ray imaging in two steps using mgdraw.f and source.f

From: Primidis, Thomas <Thomas.Primidis_at_liverpool.ac.uk>
Date: Thu, 18 Apr 2019 11:13:37 +0000

Dear all,

I wish to simulate a medical x-ray system that is equipped with a high resolution detector. I would like to see the effect of various source intensities on the image quality. The following description concerns only fully analogue simulations.

After simulating just the source with an electron primary beam, I dumped the generated photons on a file. From this initial simulation I got ~6E+5(photons) with 42E+8(electrons) thus an approximate yield of photons/electron=1.6E-4.

With post processing of those 6E+5 photons I managed to derive an analytical description of the X-ray beam phase space which then I wrote on a source.f card.

I plan on using this source.f card for the second part of the simulation which is photon transport through the phantom and the detector. I have prepared an mgdraw.f card to save photons on a 2D array which represents the pixelated photon counting detector i.e. if a photon enters the detector region, add +1 to the matrix element depending on the photon crossing position. Do not account for any efficiency issues at the moment.

I know that the real electron source has 50uA*50ms and I can translate this in total number of electrons and multiplying this with my 1.6E-4 yield I get how many photons would exit the real source. That amount of photons I will also sample from my analytical photon source.

However, I want not only to see the effect of nominal performance but several cases of lower current as well(thus lower total number of electrons). And do this for 45 different positions of the source as well. So I thought of doing one simulation per position and just save the 2D matrix in intervals, therefore having the image at different total number of electrons(total number of photons in practice).

Is there a way I can ask fluka to save this matrix whenever it has finished transporting various user defined number of particles and save these multiple files differently? So far I have managed to only save it once using NUMPAR(1) and NCASES with "save matrix when NUMPAR(1)=NCASES(this also results in the matrix being saved before the last primary has finished transportation).

One could suggest getting the <photons>/pixel/primary photons and then multiplying with any number of primary photons to get the resulting image but the high resolution of the detector does not allow for low statistical errors in reasonable time.

Best regards,


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Received on Thu Apr 18 2019 - 14:31:34 CEST

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