[gate-users] spblurring bug ?

[Christian Wietholt]

Dear Sebastien,

Thanks for the reply and for continuing the discussion. Please 
correct me if I am wrong with my assumption, but aren't those
coordinates in the world coordinate system of the simultaion, or
does the detector have it's own coordinate system? If it is the 
world coordinate system, than the z-axis should be along the 
axis of rotation, which is actually one coordinate in the projection 
image (ordinate). 

If you take a closer look at the benchmark_projection.c file, there, 
z is also used at the location of an event on the ordinate. x 
and y contributions are variable, because they are being 
rotated around the z axis. In benchmark_projection.c there are 
multiple case where the correct location of the event along the 
(absizza) is computed from x and y depending on the angle of rotation. 
So at 0 and 180 degree, x is the depth of interaction in the crystal, and 
at 90 and 270 degree y is the depth of intersection.

If you look at my original post below, where I simulated a point source 
at the origin of the world coordinate system, the average value of X is 
exactly the distance between the origin of the world coordinate system 
and the detector, and Y and Z show roughly zero as expected. 

So I created projection images, without spblurring, I get a nice round 
projection of my point source through the pinhole, but if I turn on 
spblurring, this projection is distorted, and shows no blurring in the 
z direction, indicating that there is a bug in the spblurring functionality. 
But after applying my patch, this distortion is not present anymore, and
I get a nice Gaussian distribution in all direction. 

The only mistake I might be making is that there is indeed within Gate a 
separate coordinate system for the crystal, but my results indicate differently. 
If you have time, I would like to send you my files, running the macro only
takes 10 minutes, and you can see for yourself what I am talking about. I 
just don't want to send tar archives to this mailing list. 

I am looking forward to hearing more from you and I hope I can contribute to
the development of Gate in some way. 

Best Regards,

Christian