Using CORRFACT with CT voxels

Thank you so much André and David for your help.
I’ve adjusted the beam position to hit the geometry and got the the result afterwords. Then I’ve simulated SOBP for proton beam as you can see in the screenshot below but I think it needs to be corrected for stopping power:

For that purpose, I’ve read the medical application slides and tried to implement the same instructions in slide 24 and followed very much the same procedure as it’s clearly seen in this pic:

but simulation finishes with error and outputs the following:
[ *** Region 19 (VOXEL016) containing material BONECOMP with alternate material ratio of dE/dx and other processes density scaling factors 1.30 0.818
is out of allowed range [2/3,3/2]: run stopped ***]

I’d like to know how I utilize the CORRFACT card to correct for density (stopping power) for ion beam and where I’m mistaken.
Thank you

Dear Abdul,
as you can also find on the manual page, CORRFACT allows you to alter the material density for dE/dx and other processes on a region basis. The density scaling factor can be in the range [2/3, 3/2]. If you care only to correct the density for stopping power, you can then put WHAT(2) = 0.0 as it is done on slide 24 of the Medical Application slides.

Could you please try this out? If this does not solve your error and if your files do not contain sensitive information, could you please share them so that I can have a closer look? Indeed, if I look at your second screenshot, I don’t see any CORRFACT card with WHAT(2) = 0.818 so it’s difficult to understand where this comes from.


Thank you David for addressing this issue, I think they moved this topic from another section and that’s why you haven’t had the whole topic at your end.
Here the flair and voxel files that you can take look on them and get idea about m problem.
head20150.flair (3.6 KB)

I’m running this as a beginner not having a wide knowledge about how correctly run simulation for ion beam after making a proper corrections to the voxels of the CT image.
Yesterday, I was able to run the simulation after adjusting the WHAT(1) in the second CORRFACT card to 1.2 instead of 1.3 and it worked.

also 2d plot of the USRBIN can be obtained
2d image
My question here, is my procedure to apply the CORRFACT to correct for dE/dX in order to simulate ion beam is correct or I need to implement it differently.


Dear Abdul,
the use of CORRFACT should be correct. I had a look at your *vxl file by typing string VOXEL.vxl from command line. Flair has already appended all the CORRFACT cards that were calculated while porcessing the DICOM file taking into account the calibration curves that you or someone else provided.
If for some reason you wish to overwrite the density correction for dE/dx only for a given region, I would suggest to put 0 in WHAT(2) to overwrite completely what may be written in the CORRFACT cards appended in the *vxl file.


Dear David,
Thank you for checking all this up,
I haven’t applied any calibration curve, I assume you meant using calibration curve to convert the CT numbers into HU which I think is already made by the CT image provider. The only thing I’ve done after importing the CT image is converting HU into material using predefined material in flair library (head.mat) and not sure if that is quite enough to start simulation.
another question is about using CORRFACT, is choosing regions VOXEL005 and VOXEL016 applicable for whatever CT images imported in flair and also how would I pick the correct scaling factor from (2/3,3/2) range.


Dear Abdul,
I think that it is a good start to familiarize yourself with the tools and play with it, but the important message that is also stated in slide 25 of the Medical Application lecture is: The user should update the “head.mat” or “body.mat” file with his own calibration …
The numbers that you have in the example might not be usable for another case. This also means that VOXEL005 and VOXEL016 could be different voxel regions from those of the example.
You can use the head.mat and body.mat as templates but in the end CORRFACT is a “user dependent” parameter, i.e. it depends on your specific treatment planning system.


Dear Davide,
I’m really grateful for your informative response and indeed I’m still beginner in using FLUKA as the main open source for creating an ion beam treatment planning. I’m able to create a SOBP in water phantom for various ion beams and looking forward to implementing our biophysical model into a real treatment planning system so that I’m training myself on how to utilize flair medical application for the best use. It’s true that the CT image I do have for now is not prepared for a treatment planning as no contouring or cancer volume were designated, but my advisor will get it soon.
Finally, and for future reference, you have stated that each CT image with RTplan must have its calibration curve to make a proper correction, is it true?


Dear Abdul,

yes, the user should apply the calibration curves for dE/dx that take into account his own treatment planning system.