[Gate-users] Materials.xml collaboration !
Irène Buvat
Irene.Buvat at imed.jussieu.fr
Tue Jan 15 09:27:40 CET 2008
>Hi,
There is still an error in the reference manual
in section 12.2.1 regarding the scintillation
properties:
"The variance of this normal distribution is
RESOLUTIONSCALE times this expectation value"
should be "The variance of this normal
distribution is RESOLUTIONSCALE squared times
this expectation value", to be consistent with
equation 12.2.
Irene
>I've misunderstanding the equations,
>and about the energy resolution I've mismatch 'overall
>resolution' (cristal+PM, R at 511 = 0.12) and 'intrinsic
>resolution' (cristal alone, R at 511 = 0.09) !
>
>Best regards,
>
>Samuel
>
>--- D.J.vanderLaan at IRI.TUDELFT.NL a écrit :
>
>> Hi Samuel,
>>
>> I had another look at the equations, but as far I
>> can see the equations in
>> the manual are correct.
>>
>> The standard deviation in the number of optical
>> photons generated by the
>> scintillation event N at E is given by:
>> s = RS*sqrt(N at E),
>> with N at E = E * SY. Using this in the equation for
>> the energy resolution:
>> R at E = FWHM at E/N at E = 2.35*s/N at E
>> = 2.35*RS*sqrt(N at E)/N at E
>> = 2.35*RS/sqrt(N at E)
>> From which the resolution scale can be derived:
>> RS = R at E*sqrt(N at E)/2.35
>>
>> Using the following numbers for LSO:
>> SY = 26000 1/MeV
>> R at 511 = 0.09 (this is the value used in the
>> Materials.xml file)
>> E = 0.511 MeV
>>
>> Gives
>> RS = 0.09*sqrt(26000*0.511)/2.35 = 4.41
>>
>>
>>
>> Regards,
>> Jan
>>
>>
>>
>>
>>
>> > Hi all,
>> >
>> > a litle update/fix about "RESOLUTIONSCALE", but
>> not a
>> > solution.
>> >
>> > Best regards,
>> >
>> > Samuel Burg
>> >
>> >
>> > --- Samuel BURG <samuel_burg at yahoo.fr> a écrit :
>> >
>> >> Hi Simon,
>> >> Hi all,
>> >>
>> >> 1)
>> >> here's some data I've collected about most used
>> >> cristals : NaI(Tl), BGO, GSO, LSO:Ce, YSO,
>> YAP:Ce,
>> >> CsI(Tl), CsI(Na).
>> >>
>> >> I have not put them in a structured XML file, as
>> >> there
>> >> is still some missing data (mostly ABSLENGHT at PEAK
>> >> and
>> >> RESOLUTIONSCALE).
>> >>
>> >> 2)
>> >> I'm also very confuesed about page 162 of the
>> >> GateUserGuide_v3.1.2, § "12.2.1 Scintillation
>> >> properties" :
>> >>
>> >> Knowing number of photons follow a normal
>> >> distribution
>> >> (Gauss Law), and assuming equation 12.2 [s = RS *
>> >> sqrt
>> >> (E * SY)] is right,
>> >> then equation 12.3 [RS = R at E / 2.35 * sqrt(E *
>> SY)]
>> >> is
>> >> false and should be : [ RS = R at E / (2.35 * sqrt(E
>> *
>> >> SY)) ].
>> >>
>> >> s = standar deviation
>> >> RS = ResolutionScale
>> >> sqrt = square root
>> >> E = energy (511000 eV)
>> >> SY = ScintillationYield
>> >> R at E = energy résolution @ E
>> >>
>> >> as we have a normal law : FWHM = 2,354820045 *
>> Simga
>> >>
>> >> 3)
>> >> Then I have had a look in the Materials.xml
>> sample
>> >> file given with Gate 3.1.2, and found the data
>> about
>> >> LSO:
>> >>
>> >> .../...
>> >> <material name="LSO">
>> >> <propertiestable>
>> >> <property name="SCINTILLATIONYIELD" value="26000"
>> >> unit="1/MeV"/>
>> >> <property name="RESOLUTIONSCALE" value="4.41"/>
>> >> .../...
>> >>
>> >> but when I use [ RS = R at E / (2.35 * sqrt(E * SY))
>> ]
>> >> with :
>> >>
>> >> R = 0,12
>> >> E = 511000
>> >> SY = 26000
>> >>
>> >> I found RS = 0,23, witch is about 1/4.41 !
>> >>
>> >> So, what do we need to put in Materials.xml for
>> >> RESOLUTIONSCALE, and how to compute it ?!?
>> >>
>> >>
>> >>
>> >> Best regards,
>> >>
>> >> Samuel Burg
>> >>
>> >>
>> >>
>> >> --- Simon Stute <gate.stute at gmail.com> a écrit :
>> >>
>> >> > Hi all,
>> >> >
>> >> >
>> >> > I suggest to everybody that have done some
>> optical
>> >> > photon tracking with Gate
>> >> > to answer this mail and to post your
>> Materials.xml
>> >> > file if it contains some
>> >> > additional material definitions. It would be
>> nice
>> >> to
>> >> > merge them and to put
>> >> > the more complete file as possible in the next
>> >> Gate
>> >> > release. And I propose
>> >> > to do the job :-)
>> >> > When you post your file, could you just write
>> the
>> >> > list of materials included
>> >> > in this file to easily avoid multiple
>> definition
> > >> ??
>> >> >
>> >> > Thanks in advance for your collaboration,
>> >> > Simon Stute
>> >> > >
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--
-------------------------------
Irene Buvat, PhD
Equipe "Imagerie in vivo de la perfusion et des échanges moléculaires"
http://www.guillemet.org/irene/equipe4
U678 INSERM
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e-mail : buvat at imed.jussieu.fr
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