Analyser-based phase contrast image reconstruction using geometrical optics

Area of Science:

• Medical Imaging
• Materials Science
• Physics

Background:

• Analyser-based phase contrast imaging provides high-resolution, high-contrast radiographs.
• Quantitative phase and attenuation information extraction is possible with minimal images under geometrical optics approximations.

Purpose of the Study:

• To develop and validate an improved analytical phase retrieval method for analyser-based phase contrast imaging.
• To enhance the accuracy of quantitative phase and attenuation imaging, particularly for systems with divergent X-ray sources.

Main Methods:

• Phase retrieval was performed by fitting experimental analyser rocking curves using a symmetric Pearson type VII function.
• A test phantom was imaged at 20 keV using a Si(1 1 1) analyser at the ELETTRA synchrotron radiation facility.
• The Takagi number was calculated to differentiate between geometrical optics violations and curve fitting failures.

Main Results:

• The Pearson VII function provided a >10% better fit to rocking curves compared to linear or Gaussian functions.
• The developed phase retrieval method yielded more accurate object reconstruction than linear fitting methods.
• The technique successfully enabled quantitative phase retrieval with a divergent source and accounted for analyser imperfections.

Conclusions:

• The Pearson VII function offers a superior fit for analytical phase retrieval in X-ray phase contrast imaging.
• The proposed method improves object reconstruction accuracy and distinguishes between optical and fitting issues.
• This approach facilitates quantitative phase retrieval in more complex imaging systems, including those with divergent sources.