Simulation study on X-ray phase contrast imaging with dual-phase gratings

Abstract

Purpose

Two phase gratings in an X-ray grating interferometers can solve several technical challenges for clinical use of X-ray phase contrast. In this work, we adapt and evaluate this setup design to clinical X-ray sources and detectors in a simulation study.

Methods

For a given set of gratings, we optimize the remaining parameter space of a dual-phase grating setup using a numerical wave front simulation. The simulation results are validated with experimentally obtained visibility measurements on a setup with a microfocus tube and a clinical X-ray detector. We then confirm by simulation that the Lau condition for the \(G_0\) grating also holds for two phase gratings. Furthermore, we use a \(G_0\) grating with a fixed period to search for periods of matching phase grating configurations.

Results

Simulated and experimental visibilities agree very well. We show that the Lau condition for a dual-phase grating setup requires the interference patterns of the first phase grating to constructively overlay at the second phase grating. Furthermore, a total of three setup variants for given \(G_{0}\) periods were designed with the simulation, resulting in visibilities between 4.5 and 9.1%.

Conclusion

Dual-phase gratings can be used and optimized for a medical X-ray source and detector. The obtained visibilities are somewhat lower than for other Talbot–Lau interferometers and are a tradeoff between setup length and spatial resolution (or additional phase stepping, respectively). However, these disadvantage appears minor compared to the overall better photon statistics, and the fact that dual-phase grating setups can be expected to scale to higher X-ray energies.