ogo.calibration.mindways_calibration module¶
Calibration of a mindways phantom
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ogo.calibration.mindways_calibration.MindwaysCalibration¶ Bases:
ogo.calibration.standard_calibration.StandardCalibrationPerform calibration on a Mindways phantom QCT PRO.
There is some nuance to performing density calibration with a Mindways phantom. The reason for this is that the material (\(K_2HPO_4\)) is dissolved in water. This creates a slightly different calibration equation because the content of water must be controled for.
The calibration steps are as follows. First, the densities of water and of \(K_2HPO_4\) must be known in the phantom rods. These can be taken from the certificate of calibration provided with your phantom and is different for each phantom.
Then, the equation of best fit to the Hounsfield units of each rod:
\[\mu_{ROI} = \rho_{water} + \sigma_{ref} * \rho_{K_2HPO_4} + \beta_{ref}\]The coefficient of correlation return is of this equation.
Next, there is a conversion from the water-dissolved equation to traditional density measures.
\[\sigma_{CT} = \sigma_{ref} - 0.2174\]\[\beta_{CT} = \beta_{ref} + 999.6\]Finally, Hounsfield units and K2HPO4 equivalent density are related by the following equation:
\[\mu_{ROI} = \sigma_{CT} * \rho_{K_2HPO_4} + \beta_{CT}\]In the calibration framework presented in Ogo, we want to solve the equation for \(\rho_{K_2HPO_4}\) which gives the parameters in standard calibration of:
\[m = \frac{1}{\sigma_{CT}}\]\[b = \frac{- \beta_{CT}}{\sigma_{CT}}\][1] QCT PRO User Guide, Mindways Software, Inc. v5.0, rev 20110801
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beta_ct¶ Get the computed \(\beta_{CT}\)
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beta_ref¶ Get the computed \(\beta_{ref}\)
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fit(hounsfield_units, densities, water)¶ Override Calibration fit method.
Mindways calibration phantom requires a water density
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sigma_ct¶ Get the computed \(\sigma_{CT}\)
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sigma_ref¶ Get the computed \(\sigma_{ref}\)
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