MCXlab returning 0s after first time point?

[Jesse Fine]

Hi,

I'm trying to run the attached script and it seems to work properly for the first time point, but results in all 0s for any subsequent time point. Any guidance in correcting or understanding this is much appreciated. I run into this issue whenever I construct a model with multiple layers and an additional internal geometry.

Thank you! 

[Qianqian Fang]

On 1/29/19 10:31 AM, Jesse Fine wrote:

Hi,

I'm trying to run the attached script and it seems to work properly for the first time point, but results in all 0s for any subsequent time point. Any guidance in correcting or understanding this is much appreciated. I run into this issue whenever I construct a model with multiple layers and an additional internal geometry.

hi Jesse

the mua/mus values in cfg.prop looks very big, I think you must have scaled them by 1/cfg.unitinmm. if yes, this should be undone.

the mua/mus in cfg.prop should always be given in the unit of 1/mm, independent of your cfg.unitinmm settings. mcx does the scaling internally. if you pre-scaled these values, it will be done twice and give you incorrect results.

Qianqian

Thank you! 

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[Jesse Fine]

Thank you! I can't believe I made that mistake. I have another quick question- is there a way to keep the excitation source on for all time steps?

Thanks again

Jesse 

[Qianqian Fang]

On 1/29/19 2:19 PM, Jesse Fine wrote:

Thank you! I can't believe I made that mistake. I have another quick question- is there a way to keep the excitation source on for all time steps?

for that, what you need is a convolution as a post-processing to the TPSF of the fluence from mcx/mmc.

mcx/mmc only solves for the IRF (impulse response function) assuming the source is a delta at t=0. An arbitrary waveform of the source should be convolved to the TPSF to get the final solution.

Qianqian