[gate-users] ring diameter

[Mutanga Theodore]

Thanks for that clarification Claude, I should have checked in the codes
myself, thanks anyway.
I also found out that the axial sampling interval is 1/2*axial pitch ???
Am I right ?
Cheers

Theo

> In the following exemple for the ECAT system (the exemple might have
> inconsistancies), the diameter is 83.4 cm:
>
> diameter = 2 * (427 - 30/2 + (30 - 20)/2)
>
> that is the distance between the front face of two opposing crystals and
> not opposing blocks. The calculation is based on the block and the
> crystal element descriptions only. You can also have a look inside the
> code:
>
> src/GateEcatSystem.cc, routine ComputeInternalRadius
>
> Regards,
>
> Claude
>
>
> #     B L O C K
> /gate/ecat/daughters/name block
> /gate/ecat/daughters/insert box
> /gate/block/placement/setTranslation 427.0 0.0 0.0 mm
> /gate/block/geometry/setXLength 30.0 mm
> /gate/block/geometry/setYLength 35.8594 mm
> /gate/block/geometry/setZLength 38.7 mm
> /gate/block/setMaterial Air
> /gate/block/vis/forceWireframe
>
> #
> C R Y S T A L
> /gate/block/daughters/name crystal
> /gate/block/daughters/insert box
> /gate/crystal/geometry/setXLength 20.0 mm
> /gate/crystal/geometry/setYLength 4.4 mm
> /gate/crystal/geometry/setZLength 4.75 mm
> /gate/crystal/setMaterial BGO
> /gate/crystal/vis/setColor yellow
>
>
> Mutanga Theodore wrote:
>
>> Greetings all
>>
>> I will like to know how GATE calcultes the scanner radius, I designed a
>> macro for the DST geometry (ring diameter 88.6 cm)  but when I rand
>> the /gate/systems/describe command I found out that the scanner radius
>> was
>> 88.7 cm instead , how is that so ?
>> For the system, I used the ecat system with and inner radius of 44.3 for
>> the DST camera.
>>
>> Secondly is that the axial sampling interval I was hoping for is 3.27 mm
>> but I don't find this in the system description,
>>
>> Also I found out upon zooming , in the ecat scanner example that the
>> block
>> size in the axial direction extends out of the outer radius of the
>> scanner, this only appears when you zoom in on this portion, I wonder if
>> its a problem.
>> So for my own design, I had to add a few mm's to Rmax to ensure that the
>> blosks are fully enclosed in the axial direction.
>>
>>
>>               GATE object:        'systems/ecat/crystal'
>>                 Attached to volume: crystal
>>                 Nb of children:       0
>>  >> geometrical design type: 1
>>  >> ring diameter: 88.7 cm
>>  >> block axial pitch: 3.92501 cm
>>  >> block azimuthal pitch: 5.21739 degree
>>  >> block tangential size: 3.925 cm
>>  >> block axial size: 3.925 cm
>>  >> crystal axial size: 6.3 mm
>>  >> crystal tangential size: 6.3 mm
>>  >> crystal axial pitch: 6.5417 mm
>>  >> crystal tangential pitch: 6.5417 mm
>>  >> axial nb of blocks: 4
>>  >> azimuthal nb of blocks: 70
>>  >> axial nb of crystals: 6
>>  >> tangential nb of crystals: 6
>>
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>>
>>
>>
>
>
> --
> Claude Comtat					comtat at ieee.org
> Image acquisition and processing group		tel: +33 1 69 86 77 02
> Frédéric Joliot Hospital Facility		fax: +33 1 69 86 77 49
> French Atomic Energy Commission 		www-dsv.cea.fr/shfj
>
>
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