Quasimonochromatic x-ray computed tomography by the balanced filter method using a conventional x-ray source

Area of Science:

• Medical Imaging
• Physics
• Materials Science

Background:

• Quantitative computed tomography (CT) imaging is crucial for accurate material characterization.
• Conventional CT systems suffer from beam-hardening effects, limiting quantitative accuracy.
• Developing novel CT systems for precise attenuation coefficient measurement is an ongoing research area.

Purpose of the Study:

• To develop and evaluate a quasimonochromatic x-ray computed tomography (CT) system using balanced filters.
• To assess the system's capability in acquiring quantitative CT images without beam-hardening correction.
• To demonstrate the effectiveness of the balanced filter method in CT for accurate material property estimation.

Main Methods:

• A quasimonochromatic x-ray CT system was constructed using a conventional x-ray generator, object stage, and line sensor camera.
• Balanced filters made of Erbium (Er) and Ytterbium (Yb) metallic sheets were employed to generate quasimonochromatic x rays.
• The system utilized the characteristic K-alpha doublet lines of a tungsten target, with x-ray energies characterized using a high-purity Germanium (Ge) detector.

Main Results:

• The quasimonochromatic x rays had a mean energy of 59.0 keV and an energy width of 1.9 keV.
• Spatial distributions of linear attenuation coefficients were successfully obtained for a water phantom, aluminum rod, and human head phantom.
• The CT system demonstrated effectiveness in estimating linear attenuation coefficients without beam-hardening correction.

Conclusions:

• The balanced filter method, when implemented on an x-ray CT scanner, shows significant promise for producing highly quantitative CT images.
• This quasimonochromatic x-ray CT system effectively overcomes the limitations of beam-hardening effects.
• The developed system is a valuable tool for accurate material characterization and quantitative imaging applications.