Re: Delta-ray production threshold

Dear all,

Many thanks to Alfredo for providing me the reason of my variation in
dose, i.e the fact that electronic equilibrium was not proven if the
production threshold is too large between adjacent regions.
Two days ago, I ran new FLUKA calculations with the same threshold in
all regions and total dose is OK.

Jean-Emmanuel

-- 
_______________________________________________
Jean-Emmanuel Groetz
Laboratoire Chrono-Environnement UMR CNRS 6249
Chimie-Physique & Rayonnements
Université de Franche-Comté
16 route de Gray
25030 Besançon Cedex
France
mailto : jegroetz_at_univ-fcomte.fr
tel : +33 (0) 3 81 66 65 07
fax : +33 (0) 3 81 66 65 22
_______________________________________________
Le mardi 25 septembre 2012 à 10:10 +0200, Alfredo Ferrari a écrit :
> Dear all
>
> the reason is not lack os statistics. The reason is that Jean-Emmanuel
> broke artificially electronic equilibrium by using a different (lower)
> threshold in the cell culture part wrt the materials before and after,
> which is a major conceptual mistake. Obviously the lower the delta
> threshold in the culture region wrt the surrounding the larger the amount
> of low energy electrons produced there close to the interface which escape
> into the surrodundings without being "compensated" by those produced in
> the surrounding because of the (wrongly) higher threshold -> a fake
> reduction in dose. The correct way is to set delta thresholds (and
> electron transport threshold) equal and correspodning to a range of say
> 1/4-1/10 of the cell culture thickness, if this is too cpu expensive for
> the surrounding region, they can be split into two pieces keeping the
> threshold the same only in the layer directly in contact with the cell
> culture.
>
>                 Alfredo
>
>
> +----------------------------------------------------------------------+
> |  Alfredo Ferrari                ||  Tel.: +41.22.76.76119            |
> |  CERN-EN/STI                    ||  Fax.: +41.22.76.69474            |
> |  1211 Geneva 23                 ||  e-mail: Alfredo.Ferrari_at_cern.ch  |
> |  Switzerland                    ||                                   |
> +----------------------------------------------------------------------+
>
> On Sun, 23 Sep 2012, tkatsh65_at_mail.ru wrote:
>
> >
> > Jean-Emmanuel,
> >
> >
> >
> > I think the reason is lack of counting statistic in cell culture region
> >
> > because its volume less about 10 times than cover slip and water volumes.
> >
> > So ranging from 0.18 cGy to 0.2 cGy is statistic fluctuation.
> >
> >
> >
> > Best regards,
> >
> >
> >
> > Oleg
> >
> >
> >
> >
> > Thu, 13 Sep 2012 17:40:31 +0200 от Jean-Emmanuel Groetz
> > <jegroetz_at_univ-fcomte.fr>:
> >       Users and experts,
> >
> >       With FLUKA, I have calculated the dose deposited by iron ions at
> >       1 GeV
> >       and secondaries (electrons, photons, protons...) in a cell
> >       culture with
> >       1 micron thick (between a cover slip and water).
> >       I used the HADROTHErapy option, with a transport cutoff at 1 keV
> >       for all
> >       particles and 150 eV for electrons (as Alfredo Ferrari suggested
> >       in a
> >       paper PMB 56 - 2011).
> >       When I modified the delta-ray production threshold (only in the
> >       cell
> >       culture) from 1 keV to 10 and 100 keV, the dose deposited by
> >       heavy ions
> >       increased and the dose from electrons decreased, as expected.
> >       But if I
> >       consider the total dose in the cell culture, it is not constant,
> >       ranging
> >       from 0.18 cGy to 0.2 cGy (the experimental dose was about 0.2
> >       cGy).
> >       Total doses in cover slip (1 mm thick) and in water (1.9 cm)
> >       remain
> >       constant.
> >
> >       I am wondering what could be the reason of such results in the
> >       cell
> >       culture.
> >
> >       Thank you in advance for your help and suggestions.
> >
> >       Jean-Emmanuel
> >       --
> >       _______________________________________________
> >       Jean-Emmanuel Groetz
> >       Laboratoire Chrono-Environnement UMR CNRS 6249
> >       Chimie-Physique & Rayonnements
> >       Universitц╘ de Franche-Comtц╘
> >       16 route de Gray
> >       25030 Besanц╖on Cedex
> >       France
> >
> >       mailto : jegroetz_at_univ-fcomte.fr
> >       tel : +33 (0) 3 81 66 65 07
> >       fax : +33 (0) 3 81 66 65 22
> >       _______________________________________________
> >
> >
> >
> >
> >
> >
> >