[gate-users] updated proposal and patches

[Claude Comtat]

Hi Ross,

yes, please, I'm definitely interested in your root program (this is 
what I did for the ecat7 output, to rebin the LOR via the block and 
crystal ID's).

The reason I wanted also a "purely geometric" view was for more complex 
systems, with gaps (like the HRRT). In that case, I do not know how to 
compute easily the crystal-inside-ring ID, in particular if the gap 
width is not a integer multiple of the crystal width.

Cheers,

Claude

Schmidtlein, Ross/Medical Physics wrote:

>Hi Claude,
>
>As an alternative to using the coordinates in the crystals you can bin
>the LOR via the rsector, module, submodule, and crystal ID's to compute
>the crystal and ring number pairs.  These pairs then can be binned in
>any format.  I have a general root program that does this. Is this
>something you are interested in.
>
>Cheers,
>
>ross
>
>-----Original Message-----
>From: gate-users-bounces at lphe1pet1.epfl.ch
>[mailto:gate-users-bounces at lphe1pet1.epfl.ch] On Behalf Of Claude Comtat
>Sent: Sunday, August 08, 2004 5:43 PM
>To: null99 at mails.tsinghua.edu.cn; GATE feedback and helpline for Users
>Cc: Stir-devel at lists.sourceforge.net
>Subject: Re: [gate-users] updated proposal and patches
>
>
>Dear Long,
>
>thank you very much for your effort to define a joint GATE - STIR 
>proposal. I'll do my best to help you in this job. Indeed, the Gate 
>developer team is more than happy to incorporate new contributions from 
>different users.
>
>To begin with, a few words about data format/organization in PET. By 
>nature, in "3D PET" (acquisition  without septa or with the septa 
>retracted), the data are actually 4D and not 3D. The four dimensions
>are:
>
>1) radial
>2) azimuthal
>3) axial
>4) polar
>
>A sinogram is defined by dimensions 1 and 2, and the size of the third 
>dimension (number of axial bins) decreases as the polar angle increases.
>
>In addition, because of the typical curvature of the detectors, the 
>radial sampling is not uniform.  Theses facts make that there is no 
>consensus on how to store these 4D data (unlike interfile for 3D data 
>like in SPECT, where the polar angle is null and the radial sampling is 
>uniform). Each manufacturer has its own implementation, highly dependent
>
>on the geometry of the scanner. For these reasons, the ECAT7 output 
>could not be implemented as a generic output format for CylindricalPET 
>and a new system had to be defined in order to support that format. I do
>
>not know how Interfile supports 4D PET data and ring curvature ??? For 
>ECAT7 data, the non uniformity of the radial sampling is typically 
>corrected during the reconstruction of the image (this also prevents 
>truly generic reconstruction tools).
>
>The sinogram output is closely related to the ECAT7 format, except for 
>the polar mashing (span) and can not be implemented as it is in the 
>cylindricalPET system. The radial, azimuthal, axial and polar indexing 
>of the sinogram bin is based on the crystal numbering (approximate and 
>non exact rebinning,  like for real ecat systems). For cylindricalPET, I
>
>would rather suggest a different approach, where the radial, azimuthal, 
>axial and polar indexing of the sinogram bin is based on the exact 
>radial, azimuthal, axial and polar coordinates of the LOR (exact 
>rebinning). This will make also the reconstruction easier. The exact 
>radial and azimuthal coordinates of the LOR are already calculated in 
>the root output. Once you know the exact four coordinates of the LOR, 
>based on the closest neighbor, you can assign the corresponding sinogram
>
>bin (you can let the user choose the sampling). I suggest to start with 
>a root macro rather than a new Gate class (can be done later, when 
>everything is working properly). This root macro will convert the 
>listmode root output into an Interfile  sinogram format. I can help you 
>in this job.
>
>Best regards,
>
>Claude
>
>
>null99 at mails.tsinghua.edu.cn wrote:
>
>>Dear all,
>>
>>The JOINT GATE STIR proposal is updated, including typo fix, and adding
>>
>
>>roadmap. Most important of all, adding request for help on GATE side 
>>implement.
>>
>>Patches including:
>>stir patch
>>1. newly fixed support for userdefined scanner for ifheader_for_ecat7
>>
>>gate patch
>>1. introduce macro: B_JOINT_GATESTIR
>>2. add support for Userdefined_Scanner
>>3. add Interfile support for GATESinoToECAT7
>>
>>TODOs:
>>STIR:
>>  no plans yet.
>>GATE:
>>  request help on how to adding Interfile support for cylinder system,
>>
>
>>suggestions and contribution is highly appreciated, esp. those from 
>>GATE developer.
>>  
>>Again, I hope all kinds of questions, comments, suggestions, 
>>contributions! Thanks in advance!
>>
>>Regards,
>>
>>Long Zhang
>>
>>
>>
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>>
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