[Gate-users] PROBLEM WITH SPATIAL RESOLUTION STUDY - HIGH ENERGY COLLIMATOR - SPECT

[Anestis Nakas]

Hello all,

I am trying to do a spatial resolution study using Iodine - 131 (364 keV energy) for a SPECT sytem.  I am using a high energy collimator, based on specifications that I have (septal thickness - 2mm, hole diameter (across hexagon flats) - 4 mm, hole length - 59.7mm, number of holes - 8000 and source - collimator surface distance - 10cm).

I have modeled the HE collimator within the GATE environment exactly as stated in the specifications. However, when performing the resolution study, I do not get the 13.4 mm spatial resolution that is stated in the specifications. I have fitted a Gaussian curve to the data I get from my simulation in order to determine the FWHM but the resolution I get is way worse than the desired one.

Normally when the resolution is bad, collimator parameters such as the hole length, the hole diameter or source-collimator distance need to be modified, but since those are fixed from the specifications I cannot really change them.
I tried to increase the density of the septa (lead) in order to reduce any septal penetration but even though the resolution was improved, I still did not get the one from the specifications.

Do you have any ideas or suggestions of what I could try?

Best Regards

Anestis

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