[Gate-users] Total Activity / voxels / and source activity impact on Voxel Source

[Xinjie Cao]

Hello Khalid,

I am not sure why you set activity twice in both the .dat file and the
macro. But from my experience, if you are using voxelized phantom for
simulation and try to attach some specific activity value to voxels, you
just need to set the activity in the .dat file ( need to notice that the
default unit in the .dat file is Bq).

So, let me assume that you are attaching all your activity to voxels with
label 7 as you showed in the image and all your phantom voxels are labeled
as 7  (because you didn't mention the constitution). The total activity
level of 32.928 mCi, which is ~ 1218 MBq will be attached to all voxels of
your phantom matrix evenly. 1218 MBq/6388800 ~= 191 Bq/voxel. But for most
scenarios, you do not want to just assign all voxels with single activity
level. You need to reference some papers about some specific scenarios you
would like to study and attach different activity levels to different
tissues.

Hope this helps!

Best,
Xinjie

On Sun, Oct 10, 2021 at 4:30 AM Khalid Hussain <khalidhussain1134 at gmail.com>
wrote:

> Dear Gate Users,
>
> I am using a voxel source and have defined the activity of each voxel in
> the activity.dat file.
> Here I have a question about the total number of particles. If I look at
> the stat file, activity file, and source files, and cannot be sure how the
> activity is working on and being calculated.
> My voxel image has dimensions of 220x220x132 with 0.5mm^3 voxel size and
> the total number of voxels is 6388800 and the volume is 411.601cm^3 and I
> want to assign 80nCi/cm^3 activity to my voxel source. Mathematically the
> total activity which should I give to the voxelized source is 32.928133 mCi
> but I need your guidance on how can I assign this activity to my voxelized
> source.
>
> I checked by changing the source activity probably not influencing the
> total number of particles.
>
> Please advise
>
> [image: image.png]
> [image: image.png]
>
> [image: image.png]
>
>
> Regards
>
> *KHALID HUSSAIN *| *PhD Scholar*
> *Universiti Putra Malaysia (UPM), Malaysia*
> Email:hussain.khalid at student.upm.edu.my
> Cell: *+60-11-6455-2354*
> _______________________________________________
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-- 
*....................................................*
*Xinjie Cao*
*M.Eng. / Ph.D. Candidate*
*Research Project Assistant*
*Department of Electrical and Computer Engineering & Radiology *
*Novel Medical Imaging Technologies Lab*
*Health Science Center Level 8*
*Stony Brook, NY 11794-8460 *
*Tel: +1 (631)202-9445*
you.stonybrook.edu/goldan/people/
*email: **xinjie.cao at stonybroo*k.edu <xinjie.cao at stonybrook.edu>


*....................................................*
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