[Gate-users] ASCII output

[Chen, Yu]

Hi, Simon,

I think you confuse hit with pulse. See my comments in other messages.

I am pretty sure that the Single's energy, position are *NOT* the energy, position of
the last hit, but the sum and weighted (with energy) centroid of *ALL* hits recorded.

What I am not sure is:

1) Are *ALL* hits included from different crystals or just one crystal (considering each
crystal as individual detector)?

2) Is the scattered photon different single with incident photon?

Seb, or any other expert, can you teach us about this? 

Yu Chen, Ph.D.
University of Massachusetts Medical School
Division of Nuclear Medicine
55 Lake Avenue North
Worcester, MA 01655-0243
Phone:  (508) 856-6123
Fax:    (508) 856-4572



-----Original Message-----
From: Simon Stute [mailto:gate.stute at gmail.com]
Sent: Thu 12/13/2007 11:29 AM
To: Chen, Yu
Cc: ??; gate-users at lists.healthgrid.org
Subject: Re: [Gate-users] ASCII output
 
Hi Chen Ju,

Now I am confused, I think you are write but there are still missing
informations ... I don't really know what thinking about it now ...
Hope an expert will clarify that too.

2007/12/13, Chen, Yu <Yu.Chen at umassmed.edu>:
>
>  Hi, Simon,
>
> In the following message, you mentioned:
>
> >So if your hits have scattered many
> >times in your crystal, I think the position, energy and time stamp
> mentioned
> >are for the last one. And so for your singles, there is a sort of average
> >applied by these modules that change the position, energy and time stamp.
>
> Are you indicating that only last scattered photon infomation be recorded
> and initial incident photon information just simply lost?
>
Here I want to say that the Singles informations (energy, time stamp, and
position) are for the last hit where occurred a photoelect effect in the
crystal (moreover the digitizer modules : adder, readout and blurrings, are
applied on its too). For scatter effect, there is no energy deposit, the
energy is just transferred to an other particle. But all informations about
that are recorded in the hits collection (where no digitizer is applied).
But I am not sure of anything now ...

If this had been the case for GATE, I think it would be problematic since
> one single crystal detector could not be able to distinguish incident and
> scattered photons deposited in it.
>
> My understanding for GATE is the following as sent two days ago:
>
> >From GATE manual, what I can learn is that Singles is from Pulse, and the
> latter is given by centroid of hits (weighted by energy).
> >What I am not clear is if a Pulse is only related to individual detector.
> i.e., Can a photon generate and be recorded several Pulses
> >in different detectors (crystals) if scatter (and/or penetration) occurs?
>
> >1)If yes, then it is possible to record the first pulse information
> besides that single (I assume it is centroid of pulses) information.
>
> >2)If no, (that is, one photon, one pulse, one single) we can try to
> record the first hit information (global X,Y,Z and crystal ID) into
> >corresponding Single though they are not experiment-detectable.
>
> >I prefer solution 2), which can give us precise information on how big
> the scatter and penetration effects are.
>
> And I tend to believe that above 2) is the case for current GATE: i.e.,
> even an incident photon occurs many scatterings in different crystals
> the final output is still one single that takes into account all hits from
> initial and scattered photons.
>
> Can any expert clarify this?
>
> Thanks,
>
>
> Yu Chen, Ph.D.
> University of Massachusetts Medical School
> Division of Nuclear Medicine
> 55 Lake Avenue North
> Worcester, MA 01655-0243
> Phone:  (508) 856-6123
> Fax:    (508) 856-4572
>


Thank you for the discussion,
Simon

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