> One more moment to become even more enlightened: when we score dose in usrbin*XYZ and get GeV/g per
> primary particle, and if I assume 1 particle per second, is it correct to state that I have a dose
> rate quantity?
Absolutely! [Gy/s, after the 1.6e-7 mJ/GeV conversion]
> I'm feeling myself not sure about anything anymore
Doubt is a great trigger for solid knowledge
F.
**************************************************
Francesco Cerutti
CERN-EN/STI
CH-1211 Geneva 23
Switzerland
tel. ++41 22 7678962
fax ++41 22 7668854
On Sat, 11 Mar 2017, Ševčik Aleksandras wrote:
> Thanks again, I think I finally got it. Now I see my mistake in which I asked for "total dose" as
> yes, indeed such quantity does not exist in physical meaning.
> One more moment to become even more enlightened: when we score dose in usrbin*XYZ and get GeV/g per
> primary particle, and if I assume 1 particle per second, is it correct to state that I have a dose
> rate quantity? I'm feeling myself not sure about anything anymore
>
> Regards,
> Alex
>
> ___________________________________________________________________________________________________
> From: Francesco Cerutti <Francesco.Cerutti_at_cern.ch>
> Sent: Saturday, March 11, 2017 3:15:00 PM
> To: Ševčik Aleksandras
> Cc: Alfredo Ferrari
> Subject: Re: [fluka-discuss]: Voxel geometry - region dose scoring - it it valid?
>
> Dear Alex,
>
> with dose to the tumour it's indeed meant the average dose over the tumour
> mass. However, in this case one usually has a pretty uniform distribution,
> meaning that the dose value remains rather constant over the tumour mass.
>
> Now, the alternative procedure you mention (scoring ENERGY per region and
> then dividing by the region mass) is totally equivalent to the one you
> adopted (scoring DOSE per region - which turns out to be ENERGY divided by
> the region material density, i.e. GeV/(g/cm3) that as already explained
> for the special case of score per region is not a dose, but the product
> dose*volume - and then dividing by the region volume). In both cases you
> will get the average dose over the region (the total dose does not exist).
>
> Best
>
> Francesco
>
> **************************************************
> Francesco Cerutti
> CERN-EN/STI
> CH-1211 Geneva 23
> Switzerland
> tel. ++41 22 7678962
> fax ++41 22 7668854
>
> On Sat, 11 Mar 2017, Ševčik Aleksandras wrote:
>
> >
> > Dear Francesco,
> >
> > Thank you very much for the explicit explanations. I chose wrong keywords so couldn't find the
> > previous discussions in the forum. So to normalize usrbin*region DOSE, I need to multiply it by
> > GeV/g-Gy conversion value and divide my voxel region volume in cm3.
> >
> >
> > And then I'll get the *average* dose over the region. It took me some time to grasp the idea as I
> > can't recall such concepts in my field/studies. Do I understand correctly that if I want to have
> > the total absorbed dose ( the quantity medical physicists are using, I suppose) then I actually
> > need to score the usrbin*region ENERGY which is the total energy deposition over the region (GeV
> )
> > then normalize to it to J and finally divide by mass of the region to get the total absorbed
> dose.
> >
> >
> > I'm actually little bit confused now... what actual quantity the medical physicists have in mind
> > when saying for example "the tumor should get 50 Gy in 5 days". Do they mean *average* dose over
> > tumor or the total energy deposited within the tumor volume?
> >
> >
> > Regards,
> > Alex
> >
> >__________________________________________________________________________________________________
> _
> > From: Francesco Cerutti <Francesco.Cerutti_at_cern.ch>
> > Sent: Saturday, March 11, 2017 12:53:40 PM
> > To: Ševčik Aleksandras
> > Cc: Alfredo Ferrari
> > Subject: Re: [fluka-discuss]: Voxel geometry - region dose scoring - it it valid?
> >
> > Dear Alex,
> >
> > there are two basic flaws in your approach, already discussed in this
> > forum, e.g. here:
> > http://www.fluka.org/web_archive/earchive/new-fluka-discuss/6342.html
> >
> > First, you talk about "integral" dose and "total" absorbed dose of the
> > specific region, suggesting that you aim for a sum over the region. But
> > dose is not an extensive quantity, as instead deposited energy is,
> > therefore its value on a region represents the *average* over the region,
> > which - in case of not uniform distribution - is lower than local dose
> > values inside the same region.
> >
> > Second, you forget that USRBIN *per region* (contrary to Cartesian or
> > cylindrical USRBIN) cannot normalize by the (region) volume, so the
> > quantity that you find is GeV/(g/cm3), i.e. GeV*cm3/g and not GeV/g. This
> > implies the need for dividing a posteriori by your region volume (in
> > addition to the GeV -> mJ conversion). This way you will get the *average*
> > dose over the region.
> >
> > Cheers
> >
> > Francesco
> >
> > **************************************************
> > Francesco Cerutti
> > CERN-EN/STI
> > CH-1211 Geneva 23
> > Switzerland
> > tel. ++41 22 7678962
> > fax ++41 22 7668854
> >
> > On Sat, 11 Mar 2017, Ševčik Aleksandras wrote:
> >
> > >
> > > Dear experts,
> > >
> > >
> > > Currently I'm simulating an isotope dose distribution in the anthropomorphic human head phantom
> > (25
> > > regions representing different tissues). For the overall picture USRBIN Dose tally goes well,
> but
> > I
> > > also need the integral dose over the specific voxel regions(organs), i.e. to know total
> absorbed
> > > dose of the specific region.
> > >
> > >
> > > For that purpose I used USRBIN Region point parameter and selected the particular region. The
> > > result I got is attached, i.e. simply the number which supposedly should be normalized
> > (multiplied
> > > by 1.602176462E-7) to get it in Gy.
> > >
> > >
> > > My question if this approach is correct as I have some doubts that I am oversimplifying it
> > >
> > >
> > > Many thanks for any comments/input,
> > >
> > >
> > > Rgds
> > >
> > > Alex
> > >
> > >
> > >
> >
> >
>
>
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Received on Sat Mar 11 2017 - 20:03:37 CET