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Forum: Medical Applications
Re: None Problem of two peaks in the bragg peak (Honghuan Liu)
Re: None Re: Problem of two peaks in the bragg peak (michel maire)
Re: None Re: Problem of two peaks in the bragg peak (Honghuan Liu)
Date: 03 Mar, 2013
From: Francesco Romano <Francesco Romano>

Dear Honghuan, the two peaks you see are due to the fact that probably you are using one of the macro files we have provided, where the beam traverse a specific beam line designed for proton beams at 62 MeV. In fact a brass collimator and a stopper of 7 mm are present, which are able to stop protons up to 70 MeV maximum. In your case, you are sending protons at higher energy and, therefore, they traverse the collimator and te stopper, loosing a part of their energy (and creating a second peak). My suggestion is to modify the macro you are using in order to choose a suitable initial position of the beam: not the default one (-310 cm) but, for example, -0.1 cm (which means just 1 mm before the water phantom). In such a way you are "skipping" the passive beam line (specific for 62 MeV protons for ocular tumor treatment) and sending the beam just before the water phantom where the peak is acquired. Hence, substitute the command:

/gps/pos/centre -310. 0. 0. cm

with the command

/gps/pos/centre -0.1 0. 0. cm

Hope this can help you.

Cheers, Francesco

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1 None: Re: Problem of two peaks in the bragg peak   (Honghuan Liu - 04 Mar, 2013)
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