[gate-users] ring diameter

[Claude Comtat]

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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> gate-users at lphe1pet1.epfl.ch
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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