Re: [fluka-discuss]: Energy, Dose scoring questions

From: Georgios Dedes <>
Date: Fri, 14 Mar 2014 15:12:04 +0100

Dear Paola and Alberto,

thanks for the remarks, especially for the 3D to 2D/1D plots (this was
my initial question when started this small test).

Everything is quite clear now.

Dr. Georgios DEDES
Ludwig-Maximilians-Universität München (LMU)
Medical Physics Chair (LS Parodi)
Am Coulombwall 1
85748 Garching
Tel:+49 (0) 89 289-14022
Fax:+49 (0) 89 289-14072

On 03/14/2014 03:05 PM, paola sala wrote:
> Dear Georgios,
> yes, your conclusions are correct. As explaned by Alberto, Cartesian
> or R-Z binnings are normalized per primary/cm3, region binnings are
> normalized only per primary.
> WARNING: the VOLUME field in the REGION card as presented by FLAIR is
> NOT written in the FLUKA input file, it is not used by fluka.
> Moreover, even if it was written in the input, the volume would be
> used only for the "by region summary" in the output file (see card
> SCORE) , NOT in the USRBIN by region. You can find more details in
> recent threads in the fluka-discuss archive:
> For what concerns the FLAIR plots,
> what is done is that going from 3D to 2D the values are averaged over the
> projected coordinate, keeping the normalization /primary/cm3. By
> default, the average is done over the whole range of the projected
> coordinate, but the user can choose to select a projecton interval,
> that can coincide with one or more of the original bins. The same
> going to 1D.
> Ciao
> Paola
> On 03/14/2014 01:20 PM, Georgios Dedes wrote:
>> Dear FLUKAers,
>> I've been doing some beginner's mental exercise on USRBIN ENERGY and
>> DOSE scoring. I came up to some conclusions on how it works, but I would
>> like to have some feedback from the experts.
>> First of all, I am using FLUKA 2011.2b.5 and flair 1.2-4.
>> The setup is extremely simple. An Al (d=2.6989g/cm^3) cube of size
>> 2x2x2cm^3, spanning from -1.0 , 1.0 in all dimensions.
>> I use a linear source (Deltax=0.5cm) of protons of 1MeV, such us that
>> the line source is almost equally splitted between two voxels. The
>> protons stop in the voxel that are created and the energy is completely
>> contained in those 2 voxels. I run 1000 primaries in 1 cycle, in order
>> to keep things simple.
>> Now the scoring:
>> I score either in X-Y-Z USRBIN or the whole target region. For the X-Y-Z
>> case, the target cube is divided in x,y,z as 3,2,2. So 12 voxels
>> dividing a volume of 8cm^3, resulting in a volume per voxel Vi=8/12
>> cm^3.
>> I have:
>> 2. Region ENERGY USRBIN
>> 4. Region DOSE USRBIN
>> I write both in bin and ASCII, in different logical volumes so as to
>> make it idiot proof.
>> Now my results:
>> - In the ASCII file of the X-Y-Z ENERGY USRBIN, I get:
>> 7.9027E-03 7.0856E-03 0.0000E+00 0.0000E+00 0.0000E+00
>> 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00
>> 0.0000E+00 0.0000E+00
>> As all the energy is almost equally splitted in two voxels, the
>> Energy/Primary/Vi = 5GeV/ 1000primaries / (8/12)cm^3 = 7.5E-3 (the
>> disagreement with the above comes because I assume exactly equal energy
>> deposit)
>> So the results is as expected, which means that the ENERGY in the ASCII
>> is energy density [GeV/primary/cm^3], normalized per primary and per
>> voxel volume
>> - In the ASCII file of the region ENERGY USRBIN, I get:
>> 1.0000E-02
>> which mean that the energy deposit per primary is assigned to the whole
>> target volume without any volume normalization (it is not the energy
>> density anymore) [GeV/primary]. Otherwise it would be 1E-2 / 8cm^3. So
>> for the region NO VOLUME normalization is applied. Correct?
>> - In the ASCII file of the X-Y-Z DOSE USRBIN, I get:
>> 2.9280E-03 2.6253E-03 0.0000E+00 0.0000E+00 0.0000E+00
>> 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00
>> 0.0000E+00 0.0000E+00
>> which is the dose per primary, approximately: 5GeV / 1000primaries /
>> [(8/12)cm^3 * 2.6989g/cm^3] = 2.7789 (the disagreement with the above
>> comes because I assume exactly equal energy deposit)
>> So the dose is calculated per voxel in [GeV/g] and a total dose over the
>> whole volume should be the average of all voxel doses.
>> - In the ASCII file of the region DOSE USRBIN, I get:
>> 3.7022E-03
>> which is obviously not the real dose per primary in the whole Al target
>> cube. If this was the case the dose would be either the average of the
>> doses in the X-Y-Z DOSE USRBIN ASCII file, or the total energy deposit
>> divided by the total mass of the region:
>> Edep / Nprimaries / (8cm^3 * 2.6989g/cm^3) = 10GeV / 1000primaries /
>> (8cm^3 * 2.6989g/cm^3) = 4.632E-4 Gy/g
>> So it seems that the dose it assigns to the whole region is the total
>> Energy deposit per primary in the region assuming a unit volume (1cm^3).
>> Right? Note that changing in the REGION card the volume to 8cm^3, won't
>> change the result. So in general the region scoring is not aware of the
>> volume, which is OK for the energy, but one should be aware of that when
>> scoring dose. Are my assumptions so far correct?
>> Finally, when I take a look into the 2D and 1D plots from flair, using
>> the bin files produced:
>> - The 2D xy ENERGY plot has as expected only two pixels filled, with
>> numbers close to 0.00375. This corresponds to the energy deposit in the
>> voxel that it actually happened, but normalized using the whole
>> projected volume on the single x-y pixel. That means 2 voxels depth in
>> z: 5GeV / 1000primaries / (2*8/12cm^3) = 0.00375 [GeV/primary/cm^3]
>> - The 1D x ENERGY plot gives again as expected only two bins filled,
>> with an average value of 0.00375. This corresponds to a normalization to
>> 4 voxels, as 4 y-z combinations will be projected to the same x bin:
>> 5GeV / 1000primaries / (4*8/12cm^3) = 0.001875 [GeV/primary/cm^3]
>> Similarly for the Dose...
>> Thanks in advance,
>> George
Received on Fri Mar 14 2014 - 16:17:04 CET

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