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Forum: Medical Applications
Re: Question Hadrontherapy voxel size changes (asad merouani)
Date: 03 Mar, 2013
From: Francesco Romano <Francesco Romano>

Dear Asad, the reason is that the Bragg peak in the .root file is intended to be an histogram where you can plot the energy deposited as a function of the depth (slice). Hence, if you leave the default voxel size (.1 40 40 mm) the detector is actually divided in slices and you can plot the Bragg peak. In case you change in .1 .1 .1 mm, you are creating a voxelized detector (not slice), where each voxel is 0.1 mm. Thus, you cannot plot the Bragg peak simply using the mentioned histogram but you can, for instance, create your own analysis script and sum the energy deposited in all the voxels for a fixed slice (or plot as function of the central voxel). In such a case, I suggest you to use directly the ASCII file Dose.out produced at the end of the simulation and read with your favorite analysis program. Voxels are mainly useful if you want to plot, for example, a lateral beam profile a different depths, for Bragg peaks you can use slices. Anyhow, if you want simply to produce and plot a Bragg peak, you should leave the last two numbers as default (40 40 mm), so you can have a sliced geometry. Of course, you can change the slice thickness (in order to have higher spatial resolution of Bragg peak) simply changing the first number, for instance: .01 40 40 mm. In such a case you will have a Bragg peak with a slice thickness of 10 um (instead of default 100 um). Moreover, if you want to change the detector dimensions along the beam direction (which is X axis) you can use the command: /changeDetector/size 6 4 4 cm in order to have a longer phantom (for example for higher energy primary protons). In any case, my final suggestion is to use the ASCII file Dose.out and analyse results as you prefer.

In case something is not clear yet or for any other issue, please let me know.

Cheers, Francesco

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1 None: Re: Hadrontherapy voxel size changes   (asad merouani - 05 Mar, 2013)
(_ None: Re: Hadrontherapy voxel size changes   (Francesco Romano - 08 Mar, 2013)
(_ Agree: Re: Hadrontherapy voxel size changes   (asad merouani - 20 Mar, 2013)
(_ None: Re: Hadrontherapy voxel size changes   (Francesco Romano - 24 Mar, 2013)
(_ Question: Re: Hadrontherapy voxel size changes   (Maluba Vernon - 14 Apr, 2014)
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