Re: [fluka-discuss]: PDD comparison

From: Francesco Cerutti <Francesco.Cerutti_at_cern.ch>
Date: Tue, 13 Aug 2019 10:15:51 +0200

Dear Jason,

when you plot as a function of z, you are actually averaging (the dose)
over a transverse xy area. The choice of the latter is not innocent and
should be done with respect to what you wish to compare to. In particular,
see in my attached plot, obtained with your input, the different
normalized dose profiles one gets by averaging over the whole phantom
cross section (as modelled in your geometry, and as you likely did) and a
+-4 cm square (I guess more representative of the real measurement).

Such a transverse restriction can be directly done at plotting level by
specifying in Flair the x/y limits, when plotting as a function of z.

Note that the AMB74 conversion coefficients for dose equivalent scoring
are totally irrelevant to your absorbed dose scoring.

Kind regards

Francesco

**************************************************
Francesco Cerutti
CERN-EN/STI
CH-1211 Geneva 23
Switzerland
tel. +41 22 7678962

On Mon, 12 Aug 2019, TYRRELL, JASON wrote:

>
> Hi Francesco,
>
>
> I am trying to measure absorbed dose along the z-axis. Please find my input file
> attached.
>
>
> Kind Regards,
>
> Jason.
>
> _______________________________________________________________________________________
> From: Francesco Cerutti <Francesco.Cerutti_at_cern.ch>
> Sent: 12 August 2019 19:23:23
> To: TYRRELL, JASON <J.TYRRELL3_at_nuigalway.ie>
> Cc: FLUKA discussion <fluka-discuss_at_fluka.org>
> Subject: Re: [fluka-discuss]: PDD comparison  
>
> Hi Jason,
>
> on which phantom's transverse area is the dose calculated and measured?
>
> Can you send the input file?
>
> Best regards
>
> Francesco
>
> **************************************************
> Francesco Cerutti
> CERN-EN/STI
> CH-1211 Geneva 23
> Switzerland
> tel. +41 22 7678962
>
> On Sun, 11 Aug 2019, TYRRELL, JASON wrote:
>
> >
> > Hi Everyone,
> >
> >
> > I am trying to recreate a linac head where the beam is incident on a water phantom. I
> > am trying to compare the PDD from the simulation with the experimental measurements.
> > However, when I compare the two PDD's the simulation (in red in the image attached)
> > curve has a higher surface dose and a much slower dose drop off when compared to
> > experiment. The beam energy is 15 MeV 0.1x0.1 beam incident on a tungsten target. The
> > jaws and leaves have been omitted. There is a difference filter within the collimator
> > and flattening filter placed behind it. Would anyone know a possible solution?
> >
> >
> > Thanks a lot,
> >
> > Regards,
> >
> > Jason.
> >
> >
> >
>
>


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Received on Tue Aug 13 2019 - 12:14:32 CEST

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