Speakers
Invited Speaker
X-ray phase-contrast tomography (XPCT) has emerged as a powerful tool over the last years for nondestructive 3D imaging of biological specimen. In the form of propagation based phase contrast CT, it enables full-field recordings with voxel sizes in the range of a few microns down to the range of 100nm when combined with high geometric magnification and at small Fresnel numbers (so-called holo-tomography). However, to date the technique largely relies on the monochromaticity and high spatial coherence of synchrotron radiation.
In order to exploit the full potential of XPCT in particular for applications in a preclinical and clinical setting, the translation of the method to small-scale compact instrumentation is required. Histopathology of human biopsy and autopsy samples is a case in point where pathologists would need direct access to compact highly dedicated instruments, but offering an image quality which is so far only achievable with synchrotron radiation. For this reason, we extend the capabilities of laboratory CT (lab-CT) by custom-built instrumentation in combination with dedicated phase retrieval algorithm, taking into account the broad spectrum and low partial coherence. In particular, we use a nanotube source (NT2, Excillum) and the event-based and photon energy-resolving pixel detector Mönch (PSI, Switzerland) to implement lab-CT with enhanced partial coherence offered by sub-micron source spot size combined with spectrally-informed image acquisition and reconstruction.
After measuring and modeling the spectrum, we first study the influence of the source spot size, and spectral range on the phase-contrast signal, as well as the potential gain of photon energy resolved recordings. Further, we investigate super-resolution by pixel interpolation which is a known feature enabled by the Mönch detector. Experiments and simulations are then carried out to improve understanding of how source spot size and spectral filtering influence image formation, using dedicated test objects in 2D and 3D. Different advanced phase-retrieval algorithms are compared in view of applications in a low coherence setting.
Finally, we present a benchmark for enhanced 3D imaging of unstained human biopsy tissue. The impact of spectral filtering and interpolation on contrast and resolution is quantified, and the comparison of the results with data obtained on the same sample at a commercial µCT setup (Easytom, RX solutions) and even synchrotron parallel-beam imaging (GINIX/P10) demonstrates the superior reconstruction quality for the setup presented here.