Re: Bragg Peak for proton beam in water

From: Florian Sommerer (
Date: Wed Jan 30 2008 - 16:11:13 CET

  • Next message: Vitaly Pronskikh: "Re: Bragg Peak for proton beam in water"

    Dear Alberto,
    Dear FLUKA users,

    as far as I know there is no definition for a Bragg Peak. Therefore, if
    you want to simulate one you should do it according to the data you are
    comparing the simulation with.
    I have asked Katia Parodi (who is an expert in FLUKA and in ion therapy)
    and she says that one should use for scoring the same spacial region as
    the detector.
    She also mentioned that medical physicists use a small detector and
    create a large irradiation field so that in the center the dose is
    homogeneous and you are no longer sensitive to these variations
    depending on where you measure (or "score" in the simulation) the dose.

    Best regards,

    Alberto Fasso' wrote:
    > There is some confusion in my head about what we call a "Bragg peak".
    > Please, Florian and other experts, help me clarify this concept.
    > Does the Bragg peak refer to the local dose along the path of the charged=
    > =20
    > particle, or to the laterally integrated dose?
    > If the dose is laterally integrated, a FLUKA binning is not the correct
    > technique to determine it (unless, of course, the bins are laterally
    > "infinite"). If instead the dose is local, the result can be strongly
    > dependent on the bin lateral size and on the delta ray cutoff.
    > Is there any accepted convention?
    > I have done some research on Internet and my confusion has increased.
    > For Wikipedia, the Bragg peak refers to the "energy loss" (not to the "ener=
    > gy
    > deposition"): therefore, the dose seems to be laterally integrated.
    > For the Encylopaedia Britannica, the Bragg peak refers to ionization. This =
    > is
    > less clear: total ionization is laterally integrated, but primary ionizatio=
    > n is
    > not. The exact text is:
    > "The ionization density (number of ions per unit of path length) produced b=
    > y a=20
    > fast charged particle along its track increases as the particle slows down.=
    > It=20
    > eventually reaches a maximum called the Bragg peak close to the end of its=
    > =20
    > trajectory".
    > It speaks about "The ionization density produced by a fast charged particle=
    > ":
    > does it include ionization due to secondaries, or only by the fast charged=
    > =20
    > particle itself?=20
    > Because it says "ionization density", I think it refers to the primary only=
    > ,
    > otherwise it would say just ionization.
    > The first paper by Bragg himself was also ambiguous:
    > W.H. Bragg and R. Kleeman, "On the ionization curves of radium", Phil. Ma=
    > g
    > 1904; S.6:726=C2=AD38
    > Bragg said:
    > "...measurements of the ionization produced in air by alpha
    > particles, at varying distances from a very thin source of
    > radium salt. The recorded ionization curves brought to light
    > a fact, which we believe to have been hitherto unobserved. It
    > is, that the a particle is a more efficient ionizer towards the
    > extreme end of its course."=20
    > Was that ionization, or ionization density?
    > The above text is cited by A. Brown and H. Suit, "The centenary of the
    > discovery of the Bragg peak", Radiotherapy and Oncology 73 (2004) 265.
    > In their paper, they mention another parameter affecting the Bragg peak,
    > namely the beam size: for beams of small size "the progressive scatter with=
    > =20
    > depth reduces the Bragg peak and for beams of 1=C2=AD2 mm diameter there is=
    > a=20
    > decrease in dose with depth". Clearly, that implies a dose NOT laterally
    > integrated.
    > Most other papers I have found don't help to remove the ambiguity, with
    > two important exceptions:
    > - N.V. Mokhov and A. Van Ginneken, "Muons versus hadrons for radiotherapy"
    > Proc. 1999 Particle Accel. Conf., New York 1999
    > - K. Parodi and T. Bortfeld "A filtering approach based on Gaussian-powerla=
    > w
    > convolutions for local PET verification of proton radiotherapy"
    > In both these papers it is very clearly said "laterally integrated".
    > I tend to think that the laterally integrated Bragg peak should be the righ=
    > t=20
    > choice. But in this case the plots should show energy vs depth, and not dos=
    > e vs=20
    > depth (GeV/cm, not Gev/cm3 as in the plot sent by Jamshid Soltani).
    > Or, if the alternative definition is preferred, I think that the following
    > parameters should be clearely reported, since they are likely to affect the=
    > =20
    > shape of the peak:
    > - beam size
    > - binning size
    > - delta ray cutoff
    > Alberto
    > On Tue, 29 Jan 2008, Florian Sommerer wrote:
    >> Dear Jamshid Soltani,
    >> the problem is again just the statistical fluctuation. Increase the numbe=
    > r of=20
    >> primary particles and you will see that this fluctuations will decrease. =
    > As=20
    >> the statistics goes with the square root of the number of primaries you h=
    > ave=20
    >> to increase the primaries by a factor 4 to bring the peaks of the fluctua=
    > tion=20
    >> down by a factor of 2.
    >> Please read also carefully the answer Vasilis posted in reply to your=20
    >> question from Dec 10th.
    >> Regards,
    >> Florian Sommerer
    >> Jamshid Soltani wrote:
    >>> Hi FLUKA user,
    >>> =20
    >>> I want to draw a curve for interaction of charged particles with water a=
    > s
    >>> attach file.the Bragg peak of proton beam isn't smooth and there is "zig
    >>> zag" form in its Bragg peak.I changed the binning in Z direction and it
    >>> exist the same problem again.I tried to draw a carve for the interaction
    >>> of proton beam with Calcium(target) and there is the zig zag form.
    >>> As you see in the bragg peaks of Boron, oxygen and Iron there is sharp i=
    > n
    >>> peak too.
    >>> can anyone tell me, how can I solve this problem?
    >>> =20
    >>> thanks
    >>> jamshid soltani
    > --1334196822-1027288155-1201656895=3D:18230--

    Florian Sommerer
    European Organization for Nuclear Research
    Mailbox Z04500
    Geneve 23
    CH-1211 Switzerland
    Tel : +41 2276 75582
    Fax : +41 2276 77555

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