To make a lungs source by this method, I was able to create a bin source by following the steps mentioned in the post. Here, I got a uniformly distributed source. To uniformly sample more than one organs simultaneously, say lungs and liver, I have to replace both of their materials to GOLD. Discard energy deposition in any other regions using comscw.f. Correct? Now, if I have to give weights to lungs and liver, can this method be used? For example, in the case if lungs have twice the emissions as liver?
To create a non-uniform source in the lungs, for instance, in a case where the right lung has twice the emissions as the left lung, if this method can be used?
I am aware that non-uniform sampling can be done using source routines. In this case, are the following two situations the same?
a) Sample uniformly, and change the particle_weight to probability of emission.
b) Sample according to the probability and set the particle_weight=ONEONE.
If you want to sample for separate organs with different activity, you need to assign different materials to them, and then you will be able to set the COMSCW variable in a way that the ratio of them would match the ratio of the specific activity of the organs.
It should be possible: If the left and right lungs are separate ROIs then see point 1. If not then you may be able to separate the lungs by checking the coordinate of the energy deposition using the Xa, Ya and Za variables in the comscw.f user routine.
The user routines are not compatible with USRBIN sources, but in general both options for sampling are valid.
Alternatively, you could simulate each organ separately, and combine the results using the usbscw command line program (See: USRBIN-multiply the results - #4 by horvathd). This would allow you to change the activity ratio of the organs without rerunning the whole simulation.
I was trying to create the non-uniform distribution using bin source as mentioned in the post, ie lungs have two times the emissions as liver. I did set the COMSCW variable to the ratio of specific activity of the organs (which is 3 for Lungs:Liver, considering their respective organ masses). I got the attached image, Specific_Activity_Ratio.png. If I am not wrong, I observe that the emission ratio of two times is not reflected in the plot.
Just for a trial, I have set COMSCW variable to the ratio of activity in the organs (which is 2 for Lungs:Liver), I got the attached image Activity_Ratio.png. Here I can perceive the two times emissions in the plot.
I am not sure if I am perceiving the colour bar wrong. Can you please make this difference clear?
Also I have a naive question on comscw.f statement line:
IF ( MATNAM(MEDFLK(MREG,IPRODC)) .EQ. “GOLD” ) COMSCW = ONEONE
Why doesn’t the IF statement in this routine come with END IF?
maybe I wasn’t precise enough when I used the specific activity term. In the comscw.f user routine you need to specify the ratio of primaries (decays) per bin volume and not per mass.
With this, both figure shows correctly the ratios set in the user routine.
The IF statement in the user routine doesn’t need the END IF statement since it also doesn’t have a THEN code word. See: Fortran Tutorial
