Tissue imaging is a pivotal component of both biomedical research and clinical practice. In order to identify tissue structures down to the cellular level, it requires the capability to image mm-size unstained tissue specimens with micron to sub-micron resolution. Tissue imaging is normally performed either using x-rays or visible light. While the latter is limited by light scattering in relatively thick tissues, the former often suffers from poor contrast in absorption-based systems. Phase-contrast x-ray microscopes exist but they often lack the required quantitativeness, entail acquisition times of the order of tens of hours for 3-D imaging and are limited to narrow fields of view. We propose a novel multi-modal phase-based x-ray microscope capable of imaging mm-thick tissue samples on a mm-size field of view using intensity-modulation masks. They act as optical elements allowing the quantitative retrieval of tissue properties such as transmission, refraction and scattering. Additionally, given that the system’s spatial resolution depends only on the mask aperture size, a multi-resolution approach is possible by selecting masks with aperture size matching the resolution requirements (micron and sub-micron) of specific samples. The design and optimization of the x-ray microscope is presented in this paper together with exemplar images of a thin foam sample resulting from the retrieval of the three contrast channels. The final paper will include details of the system parameter optimization (e.g., propagation distance, mask aperture and period), their effect on the retrieval algorithm and imaging performance as well as the first images of biological samples.
The implementation of X-Ray Phase Contrast (XPC) imaging at synchrotrons has demonstrated transformative potential on a wide range of applications, from medicine and biology to materials science. However, translation to conventional laboratory sources has proven more problematic, because of XPC’s stringent requirements in terms of spatial coherence. This has imposed the use of either micro-focal sources, or collimators (e.g. source gratings) where sources with extended focal spots were used. This reduces the available x-ray flux leading to long exposure times, which is often exacerbated by the use of additional optical elements that need to be scanned during image acquisition. Where these elements are placed downstream of the object, they also lead to an increase in the delivered dose.
XPC has also been successfully adapted to full 3D, computed tomography (CT) implementations, which has however exacerbated the above concerns in terms of acquisition times and delivered doses.
We tackled this problem by developing an incoherent approach to XPC that works with non micro-focal laboratory sources without requiring any additional collimation. The method uses one or two low aspect ratio x-ray masks that are built on low-absorbing graphite substrates for maximum transmission through the mask apertures. The combination of this with a “single-shot” phase retrieval algorithm has enabled the development of a lab-based XPC-CT system that can perform a full scan in a few minutes while delivering low radiation doses. The talk will briefly describe how the method works, then show application examples including direct comparisons with the synchrotron gold standard.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.