Linearly polarized X-ray fluorescence computed tomography based on a Thomson scattering light source: a Monte Carlo...

Area of Science:

• Medical Imaging
• X-ray Physics
• Computational Science

Background:

• Thomson scattering X-ray sources offer tunable, high-brightness X-rays ideal for advanced imaging.
• Compton scattering presents a significant background noise challenge in X-ray fluorescence computed tomography (XFCT).

Purpose of the Study:

• To investigate the suppression of Compton scattering in XFCT using linearly polarized X-rays.
• To assess the feasibility of linearly polarized XFCT with a Thomson scattering source.
• To evaluate imaging performance considering phantom attenuation, sampling strategy, and comparison with K-edge subtraction CT.

Main Methods:

• Monte Carlo simulations were employed to model XFCT.
• A fan beam and pinhole collimator geometry were used with a polymethyl methacrylate phantom containing gadolinium solutions.
• Simulations analyzed the impact of horizontal versus vertical polarization on Compton scattering suppression.

Main Results:

• Horizontal polarization suppressed Compton scattering by approximately 1.6 times compared to vertical polarization.
• Accurate spatial and quantitative imaging of gadolinium concentrations was achieved, showing good linearity.
• Full 360° sampling and attenuation correction were necessary when attenuation effects were significant.
• XFCT demonstrated improved contrast-to-noise ratios (2.03x at 0.2 wt% Gd, 1.04x at 0.5 wt% Gd) compared to K-edge subtraction CT.
• High flux Thomson scattering sources (10^13 photons/s) enable rapid XFCT data acquisition (seconds to minutes) without pulse pile-up.

Conclusions:

• Linearly polarized X-rays from Thomson scattering sources effectively reduce Compton scattering in XFCT.
• This technique allows for accurate, quantitative imaging of elemental concentrations.
• Optimized sampling and attenuation correction are crucial for accurate results in attenuating phantoms.
• Polarized XFCT offers superior performance to K-edge subtraction CT, especially at low concentrations.
• Advanced Thomson scattering sources facilitate rapid and high-quality XFCT imaging.