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Hi all,</div>
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I am in need of assistance when calculating the dose uncertainty using output from the dose actor. I would like to merge multiple dose point kernel outputs from the dose actor to speed up my overall simulation time. Using the output from a single simulation
to verify the calculation of the uncertainty, my results are ~1% different from the reference GATE output on average with a >8000% difference at the origin. I am using the formula found in GateDoseActor.cc:</div>
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<div><span> </span><span style="color: #569cd6">double</span><span> std_dose =
</span><span style="color: #dcdcaa">sqrt</span><span>( (</span><span style="color: #b5cea8">1.0</span><span>/(N-</span><span style="color: #b5cea8">1</span><span>))*(sq_dose/N -
</span><span style="color: #dcdcaa">pow</span><span>(dose/N, </span><span style="color: #b5cea8">2</span><span>)) )/(dose/N);</span></div>
<div><span> </span><span style="color: #c586c0">if</span><span>( dose == </span>
<span style="color: #b5cea8">0.0</span><span> || N == </span><span style="color: #b5cea8">1</span><span> || sq_dose ==
</span><span style="color: #b5cea8">0</span><span> )</span></div>
<div><span> std_dose = </span><span style="color: #b5cea8">1.0</span><span>;</span></div>
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Here, the corresponding image data (attached in doseActorOutput.zip) are assigned as dose = Dose.mhd, sq_dose = Dose-Squared.mhd, and N = NbOfHits.mhd and then element-wise operations are performed. My approach is slightly different as I mask the matrices to
avoid nan/inf results:<br>
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<div><span> N = np.ma.masked_equal(N, </span><span style="color: #b5cea8">0</span><span>)</span></div>
<div><span> N = np.ma.masked_equal(N, </span><span style="color: #b5cea8">1</span><span>)</span></div>
<div><span> dose = np.ma.masked_equal(dose, </span><span style="color: #b5cea8">0.0</span><span>)</span></div>
<div><span> sq_dose = np.ma.masked_equal(sq_dose,</span><span style="color: #b5cea8">0</span><span>)</span></div>
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<div><span> </span><span style="color: #6a9955"># calculate uncertainty using formula from GateDoseActor.cc</span></div>
<div><span> std_dose = np.sqrt( (</span><span style="color: #b5cea8">1.0</span><span>/(N-</span><span style="color: #b5cea8">1</span><span>))*(sq_dose/N -
</span><span style="color: #dcdcaa">pow</span><span>(dose/N, </span><span style="color: #b5cea8">2</span><span>)) )/(dose/N)</span></div>
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<div><span> std_dose = np.ma.filled(std_dose, </span><span style="color: #b5cea8">1.0</span><span>).astype(np.float32)</span></div>
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Some/very few of the calculated std_dose values are greater than one (1.0000001 so I am not sure if this is indicative of an error or if I should just normalize std_dose before filling the masked values with 1. Also, the Dose-Uncertainty.mhd images appear identical
in ImageJ but the actual values appear to be scaled differently (see attached doseKernel.zip).
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Please correct me in my calculation or provide any information on the correct way to calculate the uncertainty using the Dose, Dose-Squared, and NbOfHits files.</div>
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Positively,</div>
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Matthew<br>
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