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AttenuationConv data should be in units of cm-1 #44

@robbietuk

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@robbietuk

In

10
0 0 Air
114 114 Lung
115 383 Body
384 384 Adipose
385 394 Body
395 395 Muscle
396 402 Body
403 403 Body
404 420 Body
421 1000 SpineBone

the attenuation coefficient ranges are not intuitive. STIR uses attenuation coefficient units of cm^-1.
The input attenuation voxelised phantom for this project should use this attenuation coefficient unit for future STIR processing.

Body tissue has an approximate attenuation coefficient of 0.096cm^-1 (i.e. water).
In

stir_math --including-first --times-scalar 10000 $AttenuationFilenameGATE".hv" $AttenuationFilename

the interfile attenuation image is multipled by 10,000 to create a GATE interfile image, which would corespond to a AttenuationConv of 960 for body tissue/water. This would corresponds to SpineBone in GATE.

Two options:

  1. change the multiplier in In

    stir_math --including-first --times-scalar 10000 $AttenuationFilenameGATE".hv" $AttenuationFilename
    to not be 10,000 but some scaling value that maps between the values in an XCAT and the expected GATE materials.

  2. Change the values in

    10
    0 0 Air
    114 114 Lung
    115 383 Body
    384 384 Adipose
    385 394 Body
    395 395 Muscle
    396 402 Body
    403 403 Body
    404 420 Body
    421 1000 SpineBone

    to better align the multiplied coefficients.

In my opinion, 2. is the better method.
To do this, we need to use something like XCAT to assertain the attenuation coefficients ranges of different body materials, multiply by 10,000, and update the AttenuationConv.dat file. Should be done for #37

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