Comparison of equivalent photon energy calibration methods in computed tomography

Area of Science:

• Medical Physics
• Radiological Imaging
• Materials Science

Background:

• Accurate determination of equivalent photon energy is crucial for quantitative CT imaging.
• Existing methods for specifying equivalent photon energy have limitations in precision and applicability across different materials.

Purpose of the Study:

• To compare a novel method for specifying equivalent photon energy with a standard method.
• To evaluate the accuracy and precision of the novel method under various experimental conditions.
• To assess the impact of uncertainties on equivalent photon energy determination and its application in predicting CT values.

Main Methods:

• A new method defining equivalent photon energy based on maximum correlation between linear attenuation coefficient and CT values was proposed.
• This method was compared against a standard method using water as a reference.
• Experiments were conducted using varying tube potentials, aluminum filtration thicknesses, and water phantom thicknesses.

Main Results:

• The novel method showed high precision (+/- 2.2 keV) in predicting changes in equivalent photon energy.
• Both methods yielded comparable equivalent photon energies within a 3 keV difference, attributed to water's attenuation properties.
• The novel method accurately predicted CT values for high atomic number water solutions (5 mg/ml) with less than 10 CT number difference.

Conclusions:

• The proposed method offers a robust and precise approach for determining equivalent photon energy in CT imaging.
• This method enhances the reliability of quantitative CT analysis, particularly for materials with high atomic numbers.
• The findings contribute to improved accuracy in CT-based material characterization and diagnostics.