[Gate-users] ARF fails to produce output

[Matthew Strugari]

Hi everyone,

Does anyone know if the ARF table is designed to be used with parallel hole collimators? I am having a hard time obtaining any useful results when using the ARF table with my single pinhole collimator. The attached photos show the projection data used to generate the ARF table and, under identical source placement and SPECThead placement conditions, the output does not appear anything like it should. Could this be caused by the fact that my SPECThead is defined in the XZ plane and then rotated into the YZ plane to generate, compute, and use the ARF tables? I have tried changing the projectionPlane orientation from XZ to YZ which produces identical output as shown in the image.

Thank you,
Matthew

________________________________
From: Matthew Strugari <matthew.strugari at dal.ca>
Sent: December 2, 2019 5:27 PM
To: gate-users at lists.opengatecollaboration.org <gate-users at lists.opengatecollaboration.org>
Subject: Re: ARF fails to produce output

Hi again everyone,

As it turns out, the ARF only works with the detector in the YZ plane. I was able to get the ARF working for my own application but the functionality is still not clear to me so any information on the following would be greatly appreciated.

  1.  Is the ARF data best generated with a rectangular source? According to "Implementation of angular response function modeling in SPECT simulations with GATE" by Descourt et al., the ARF tables are generated with a rectangular source but no rationale is provided.

  2.  Furthermore, once the ARF is tabulated and computed for a given collimator/detector pair and energy window, the ARF table may be used for any simulation involving the collimator/detector pair. Therefore, can the ARF tables be used in any simulation with any source definition? I would assume that the ARF tables should be generated under the same conditions for which they will be used (i.e. identical sources and detector placement in the generation and use of ARF tables) but this doesn't appear to be the case.

Regards,
Matthew

________________________________
From: Gate-users <gate-users-bounces at lists.opengatecollaboration.org> on behalf of Matthew Strugari <matthew.strugari at dal.ca>
Sent: November 29, 2019 5:34 PM
To: gate-users at lists.opengatecollaboration.org <gate-users at lists.opengatecollaboration.org>
Subject: [Gate-users] ARF fails to produce output

Hi everyone,

Do any of you have a working example of the angular response functions from the ARF or SPECT_FFD examples in the GateContrib folders?

I could also use some clarification on a couple of things. First, the ARF example contains some errors/unclear settings such as the generation of the ARF tables using 364.5 keV photons and then the computation of the ARF tables using a reference energy of 140. keV. I assume this is a typo and 364.5 keV should be the reference energy but this discrepancy is present in both the readthedocs and the ARF macro files. Second, the readthedocs doesn't instruct users to set

  *   /gate/systems/SPECThead/setProjectionPlane <> <Unit>

where <> <Unit> "sets the YZ projection plane relative to the ARF device center". Is this line no longer required and does ARF only work with detectors in the YZ plane? My setup places my detector in the ZX plane and I cannot get any output to be produced. In all cases, the analog simulation produces output but the ARF simulation does not. I have attached the terminal output following execution of the SPECT_FFD angularResponseFunctionSPECT.mac simulation. It appears as though the ARF tables are not being loaded correctly.

Regards,

Matthew


--

Matthew Strugari

Biomedical Translational Imaging Centre - BIOTIC,
5890 University Ave,
Halifax, NS, B3K 6R8
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