[Homer-users] tMCimg.C question

[David Boas]

Photons are only scored to the history file when the photon escapes from a
boundary.  When the photon reaches a boundary, a search through the listed
detectors is performed to see if the photon falls within the aperture of any
of the detectors.  

 

It sounds like you are hoping that the code checks the list of detectors at
all points along the photon trajectory.  That would slow the code down
significantly and was never needed for the questions we were addressing with
the code.

 

I worry about your creation of artificial boundaries, because whenever the
photon reaches a boundary, its propagation will end.  So, you will be
artificially ending the propagation of the photon.

 

Hope this helps.

 

David

 

 

 

 

  _____  

From: homer-users-bounces at nmr.mgh.harvard.edu
[mailto:homer-users-bounces at nmr.mgh.harvard.edu] On Behalf Of Bryan
McLaughlin
Sent: Monday, March 06, 2006 1:36 PM
To: homer-users at nmr.mgh.harvard.edu
Subject: [Homer-users] tMCimg.C question

 

All,

I have a question regarding the use of TMCimg.  When I run the simulation
with a simple, linear transmission geometry, TMCimg always moves my source
and detectors to a nearby boundary defined in the user defined ".BIN"
segmentation file.  However, if I run TMCimg with the switch "-d" which is
supposed to force TMCimg to NOT move the detector, the program runs and the
.HIS history file is empty.  This is strange because if I let it move the
detectors to the boundary, then I get sensible data in the .HIS history
file.

 

I suspect that if the detector aperture is not at the boundary, then the
program is somehow not counting the photon exiting from the system and this
is why the .HIS is empty.  I just cannot understand why if the detector is
at an arbitrary location inside one of the tissues that the result is an
empty HIS file.

 

Is there any way around this?  I could potentially just define a .BIN with
some artificial boundaries so that when TMCimg moves them then I know they
are at a sensible location that will correctly represent the simulation I
intend to do.

 

Kind Regards,

Bryan

 







 

 



Bryan McLaughlin
PhD Candidate 

Cambridge University
544 King's College
Cambridge CB2 1ST
United Kingdom 


 <mailto:bryan.mclaughlin at marshallscholarship.org>
bryan.mclaughlin at marshallscholarship.org
 <mailto:bm304 at cam.ac.uk> bm304 at cam.ac.uk
IM: mclaugb_uk 


mobile: 

UK 0+44+(0)7976 000620 

 



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