[Gate-users] ARF fails to produce output

[David Sarrut]

Hi Matthew,

1. not fully clear for me, but I think that the source should cover the
whole range of a) detector position, b) direction, c) energy, that your
detector will have to handle during the simulation that will use ARF. The
idea is to build a statistical model (histogram) that is representative. My
feeling is that the rectangular shape is not important, as soon as you
cover the space (pos, dir, ene).

2. yes, once computed, any source can be used. The ARF is a statistical
detector response model that gives you the probability to detect a given
pos/dir/ene particle reaching the detector entrance plane in *all* of the
energy windows of your detector. So it will work for any type of source,
provided that the pos/dir/ene of photon impinging the detector plane is
included in the range you learn in step 1.

We had some experiences with ARF and also struggled with the limitations
(YZ plane etc). It works well but is not very convenient to use.

More recently, we have been working on a different version using neural
networks. It is yet in development and requires dependences (libtorch) but
if you are interested I will be happy can guide you.

David


On Mon, Dec 2, 2019 at 10:28 PM Matthew Strugari <matthew.strugari at dal.ca>
wrote:

> 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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-- 
David Sarrut, Phd
Directeur de recherche CNRS
CREATIS, UMR CNRS 5220, Inserm U1206
Centre de lutte contre le cancer Léon Bérard
28 rue Laënnec, 69373 Lyon cedex 08
Tel : 04 78 78 51 51 / 06 74 72 05 42
http://www.creatis.insa-lyon.fr/~dsarrut
_________________________________
 "2 + 2 = 5,  for extremely large values of 2"
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