[Gate-users] X-ray energy spectrum as GPS in Gate

Daniel J Sandoval DJSandoval at salud.unm.edu
Fri Dec 8 16:08:42 CET 2017


Thank you so much for your reply! I was hoping that I had understood it correctly, that GATE handled the normalization, and you have cleared that up.

Thank you for you help!

Daniel J. Sandoval, M.S. DABR
Medical Physicist
University of New Mexico Department of Radiology
Phone: 505-272-9298
Cell Phone: 505-239-6334
djsandoval at salud.unm.edu<mailto:djsandoval at salud.unm.edu>

From: simon.rit at gmail.com [mailto:simon.rit at gmail.com] On Behalf Of Simon Rit
Sent: Thursday, December 7, 2017 11:31 PM
To: Daniel J Sandoval <DJSandoval at salud.unm.edu>
Cc: gate-users at lists.opengatecollaboration.org
Subject: Re: [Gate-users] X-ray energy spectrum as GPS in Gate

Hi Daniel,
The spectrum is normalized by Gate to obtain a probability distribution. For every new primary photon, Gate randomly chose a photon energy according to this PDF. So only the relative importance of the numbers matter, their unit does not.
You may want to chose a number of primaries in your simulation to simulate a given irradiation. For this, I suggest to integrate the SpekCalc spektrum for given distance, mA and ms settings, this should give you the total number of primaries. Another option is to chose the number of primaries to reach a given dose (see eq 2 in https://doi.org/10.1002/mp.12448).
Best regards,

On Fri, Dec 8, 2017 at 5:15 AM, Daniel J Sandoval <DJSandoval at salud.unm.edu<mailto:DJSandoval at salud.unm.edu>> wrote:
Hello Simon,

I am attempting a project where I simulate a spectrum using SpekCalc and then run it in GATE. I stumbled upon the below message, and am truly grateful for your script. However, I do not quite understand what it is doing to the fluence. In your example, for the first line, you have an energy of 0.012 MeV, and a fluence of 2.591082e-126. However, when I create a sample spectrum of 120kev, my first line has an energy of 0.012MeV, but a fluence of 0.2479699. I have tried to look into the GATE manual to see what it expects for units of fluence, but have been unsuccessful.

If you could please help me understand what units the fluence are for GATE it would be greatly appreciated.

Thank you,



I have written the enclosed script to convert a SpekCalc output to a

Gate macro. It produces a file like


The output macro file can be called like in



On 14/05/2017 13:10, Emmanuel Marfo wrote:


> Hi Sir,


> Please am a beginner trying to use Gate to do my simulations as part

> of my thesis. So far I have been learning Gate v7.2 user guide. I want

> to use x-ray energy spectrum from SpekCalc as GPS in my simulation but

> don't know how to go about it and the explanation in the user guide is

> hard to understand. Can anyone help or suggest any way I could do

> this. Thanks


> Best regards,


> Emmanuel Marfo


> Student


> University of Otago




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