CT Scanner Setup

Requires ImageJ 1.53k or higher, MuMassCalculatorLib.jar, ImageJAddins.jar.

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Scanner Setup is a 1D attenuation model that displays x-ray intensity distributions at important points along the ray path. The plugin provides a non-modal dialog to aid in selecting optimal CT scanner operating conditions to improve signal-to-noise and reduce beam hardening artifact.

The User Interface

• Target - The anode material of a conventional X-ray source.
• KV - The accelerating potential of a conventional X-ray source.
• ma - The beam current of a conventional X-ray source.
• Filter Material - Usually a metal foil placed just downstream of the X-ray source.
• Filter Thickness(cm) - The thickness of the filter in centimeters.
• Sample Name Filter - Clips the materials list choices to those beginning with the characters in this textbox. Clear to restore the full list.
• Sample Name Choices -Pick a material from this list imported from DefaultMaterials.csv in the plugins/DialogData folder.
• Sample Formula - Pre-populated from the name choice. Edit to change the sample formula.
• Sample Thickness(cm) - Pre-populated from the name choice. Edit to change the sample thickness.
• Sample Density(gm/cc) - Pre-populated from the name choice. Edit to change the sample density.
• Detector Name Filter - Clips the choices to those beginning with the characters in this textbox. Clear to restore the full list.
• Detector Name Choices -Pick a material from this list.
• Detector Formula - Pre-populated from the name choice. Edit to change the detector formula.
• Detector Thickness(cm) - Pre-populated from the name choice. Edit to change the detector thickness.
• Detector Density(gm/cc) - Pre-populated from the name choice. Edit to change the detector density.
• Plot Minimum(keV) - Sets the X-ray Spectra plot minimum energy. The maximum energy is the accelerating potential(KV).
• Plot Inc(keV - Sets the energy step size for the polychromatic scan. Large steps go faster. Small steps have better spectral resolution.
• keV Angstroms Buttons - Selects the plot x-axis scale
• Update Plot - Recalculate the plots and results.
• OK - Recalculate, update and exit leaving plot and results windows open
• Cancel - Exit closing plots and results windows.
• Help - Brings up this page.

The top plot shows the relationship between sample thickness and attenuation. It should look like a nearly straight line if the incident photon beam is approximately monochromatic.

The middle plot shows intensity vs X-ray energy at five sampling points along the beam path.

• Blue, the source spectrum.
• Red, the source spectrum after the filter.
• Green, the source spectrum after the filter and sample.
• Gray, source spectrum after the filter detected. "Io"
• Black, the source spectrum after the filter and sample detected. "I"

The window at the bottom shows the results for each trial configuration.

The ImageJ plugin

The Scanner Setup plugin helps to fine-tune the pre-hardening technique.

Pro:
• It guides selection of the operating conditions that should optimize contrast and attenuation measurements for your sample.
• It provides an interactive way to minimize the severity of beam hardening.

Con:
• The detector is "ideal" in that it returns at each energy the fraction of counts absorbed by the scintillator screen. Energy dependent fluorescent yield, collection efficiency, gain and other characteristics of real detectors are neglected.
• The x-ray source intensity is calculated using the Kramers equation and neglects characteristic emission lines and source configuration.
• Specimen scatter and fluorescence are neglected.
• Due to the above characteristics, it may not be a good predictor of your scanner's performance.

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