Set scoring plane position

[tairozero]

I want to create general head-tube for measure backscatter factor in diagnostic radiology and already have accelerator and egsphant CT phantom file for simulation. However, I don’t sure that I have correct understanding in some condition, so please help me checked it.

I decided to used isource 9 (Beam treatment head simulation used as source, incident from any angle). If I want to get the dose at the surface of phantom and 100 cm Focal-surface distance, I must set the “distance from source to iso-center (cm)” at the surface of the phantom with the same position of scoring plane in beamnrc setting and move my focal spot in beamnrc to correspond with 100 cm of FSD?

Even if, my phantom’s position is in the -y direction. Must I have set the source in -y direction too?

[rtownson]

For a beam aimed along -y, use this:

./coordinateTransform.py 180 0 0
('Gantry, couch, collimator:', 180.0, 0.0, 0.0)
('Theta, phi, phicol:', 90.0, 90.0, 270.0)

The dsource parameter in DOSXYZnrc corresponds for source 9 to the distance from the isocenter to the source scoring plane in BEAMnrc. So let's say you BEAMnrc your scoring plane is at z=50cm, your isocenter is at 0,0,0, and your phantom surface is at y=+10. Then use the theta/phi/phicol from above, with dsource=60. This means your FSD is 100, and FAD (focal to axis distance) is 110.

Duplicate post: https://www.reddit.com/r/EGSnrc/comments/12ml745/check_infirmation/

[rtownson]

To get statdose (and dosxyznrc) to compile with so many voxels, you'll need to adjust compiler flags, and be sure you have a lot of RAM available. Expect to need about RAM equal to about X*Y*Z*8bytes*5, where X is your maximum number of voxels along X, etc.

See here: https://www.reddit.com/r/EGSnrc/comments/jkcv4e/increase_the_maximun_number_of_voxels_in_xyz/

The grey doses I'm not sure, but just check the dose profile, does it make sense?

[tairozero]

How can I find the flags? Is in statdose.mortran?

[rtownson]

In omega/progs/statdose/Makefile change

@$(F77) $(FOPT) $(FCFLAGS) $(FOUT)$@ statdose_$(my_machine).f

to

@$(F77) $(FOPT) $(FCFLAGS) -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -mcmodel=large $(FOUT)$@ statdose_$(my_machine).f

and trying recompiling statdose. I assume you already had to do this for ctcreate and dosxyznrc in order to get them to compile with so many voxels.

[tairozero]

I didn’t change in ctcreate and dosxyznrc yet, should I change too?

[tairozero]

I've tried to change the line follow your mention, Unfortunately, my RAM is not have space enough to compile it. However, I'll try to use external resources like 3ddose_tool or Profeel

[tairozero]

Yes, I set the lowest SLAB as scoring plane to use as Field size with the 10x10 cm to 40x40 cm so, that mean I must set the outer boundary between 5-20 cm right? And after I got the 3ddose file, how I can read the dose in the file?

[rtownson]

I don't see how changing the boundary changes this - you would still use a tool like VICTORIA to look at the dose profiles in the 3ddose file from DOSXYZnrc.

[tairozero]

I still using VICTORIA to see dose profile, since I can’t use statdose. And I didn’t show the dose result from boundary changing. It’s still simulating.

[tairozero]

Or just I should to extend the boundary to cover all of the phantom’s surface?

[rtownson]

The boundary of the CM is an artificial cut-off for the radiation field, so you should make it large enough that it does not affect the quantities of interest. The only reason to reduce it is for an accuracy/efficiency trade-off. Ideally, all collimation should be done by realistic objects modelled in your simulation.

[tairozero]

Thank you for your information. In this case, Should I change only the half-width of outer square boundary or both of half-width and thickness of the SLAB?