[Castor-users] Reconstructed images' units

[jbaran]

Dear Castor-Users,

I have a question regarding the reconstructed images. I tried to 
reconstruct GATE simulation data from my own scanner setup. The images 
looks well. However, there is a problem with voxel values and units.I 
performed attenuation correction (attenuation map in cm^-1) and 
sensitivity correction (long list-mode acquisition with high number of 
true coincidences). I prepared new normalization map which merged 
attenuation and sensitivity (-opti SENS recon option) and put that as an 
-img input for the main reconstruction. What I found is that in case of 
uniform distributed phantom the voxel values are quite low (i.e. 
2*10^-8), however the background values dropping down every iterations 
(i.e. from 10^-2 - 2nd iteration up to 10^-34 15 iteration). I am 
wondering what kind of calibration factor should I apply to get proper 
units i.e. number of counts ? How should I eventually calculate that 
factor? Is it somehow dependent from the iteration number?

I need it to perform NRMSD (Normalised Root Mean Square Deviation) 
analysis to find the optimal number of iterations.

All the best,
Jakub