[Gate-users] FW: LET problem in GATE

[Andreas Resch]

Hi Klara,

I would recommend to

- update to a newer Gate version (in the old Gate version you could also 
try following command: /gate/actor/myLETActor/stepHitType    random )

- set electron cut to 10 mm

- set max step size limit to 1/10 of scoring grid size in beam direction 
(after that you may gradually increase it until the effect sets in 
again).

to convert dcm files, maybe check out gatetools

best,

Andreas

Am 2022-03-31 14:21, schrieb Klára Badraoui Čuprová:

> Dear Andreas and Gate users,
> 
> thank you for your reply, I have Gate version 8.2. I set electron cut 
> in patient 0.1mm and I did not set step size limit.
> 
> OK, yes it seems the voxel size is really the problem. Hopefully then, 
> the solution would be
> 
> to create voxel phantom with grid 2mmx2mmx2mm. I wrote my own script to 
> convert CT
> 
> dicom slices to mhd and raw files, but the voxel size copies the size 
> of the CT (1.2695,1.2695,2).
> 
> I would like to ask, is there some program to resample the dicom CT 
> slices (to grid 2mmx2mmx2mm), output can be either dicom or mhd+raw 
> files?
> 
> Thank you in advance,
> 
> best regards,
> 
> Klára
> 
> From: Andreas Resch [mailto:andreas.resch at meduniwien.ac.at]
> Sent: Thursday, March 31, 2022 10:47 AM
> To: Klára Badraoui Čuprová <Klara.BadraouiCuprova at ptc.cz>
> Cc: gate-users at lists.opengatecollaboration.org
> Subject: Re: [Gate-users] FW: LET problem in GATE
> 
> Dear Klara,
> 
> interesting!
> 
> Which Gate version are you using? e- production cuts? Max Step size 
> limit?
> 
> " May there be some artefact because of calculation grid and phantom 
> voxel size?" yes, that would be my first guess. Seems like is happening 
> every 2-3 voxels, which can come from having a non constant number of 
> geometric boundaries per scoring unit volume, e.g. if CT is 1.2695 mm 
> spaced and calculation grid 2 mm, in the third calculation voxel there 
> are two geometric boundaries, whereas in the first two are only one 
> each.
> 
> best,
> 
> Andreas
> 
> Am 2022-03-31 07:34, schrieb Klára Badraoui Čuprová:
> 
>> Dear,
>> 
>> I am medical physicist in Proton Therapy Center in Czech and I am 
>> concerned with Monte Carlo simulations in GATE for proton therapy.
>> 
>> I calculate dose and LET distributions in patients and in some 
>> patients I get strange results for LETdistributions. (Dose 
>> distributions are all OK.)
>> 
>> In some LET distributions a line pattern appears (I am attaching 
>> printscreen). (The patients with such problem are irradiated from main 
>> angles (0°,90° or 270°).
>> 
>> Calculation of LET to water phantom was OK. May there be some artefact 
>> because of calculation grid and phantom voxel size? Calculation grid 
>> is 2mmx2mmx2mm.
>> 
>> Voxel phantom of one particular prostatic patient is of size 1.2695mm, 
>> 1.2695mm, 2mm. Please, do you have some idea why this happens?
>> 
>> I would be very grateful for help.
>> 
>> Best regards,
>> 
>> Klára Badraoui Čuprová
>> 
>> Ing. Klára Badraoui Čuprová, PhD.
>> 
>> Medical physicist
>> 
>> Proton Therapy Center Czech s.r.o., Křenova 11, CZ-162 00 Praha 6
>> 
>> Zapsáno v OR u MS Praha, odd. C, 84153, IČ 26466791, DIČ CZ26466791
>> 
>> telefon +420 222 998 941 info at ptc.cz, www.ptc.cz [1]
>> 
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