Abstract
Visualizing the internal architecture of large soft tissue specimens within the laboratory environment in a label-free manner is challenging, as the conventional absorption-contrast tomography yields a poor contrast. In this communication, we present the integration of an X-ray double-grating interferometer (XDGI) into an advanced, commercially available micro computed tomography system nanotom® m with a transmission X-ray source and a micrometer-sized focal spot. The performance of the interferometer is demonstrated by comparing the registered three-dimensional images of a human knee joint sample in phase- and conventional absorption-contrast modes. XDGI provides enough contrast (1.094 ± 0.152) to identify the cartilage layer, which is not recognized in the conventional mode (0.287 ± 0.003). Consequently, the two modes are complementary, as the present XDGI set-up only reaches a spatial resolution of (73 ± 6) μm, whereas the true micrometer resolution in the absorption-contrast mode has been proven. By providing complimentary information, XDGI is especially a supportive quantitative method for imaging soft tissues and visualizing weak X-ray absorbing species in the direct neighborhood of stronger absorbing components at the microscopic level.
Highlights
Micro computed tomography based on the conventional X-ray sources usually operates in the absorption-contrast mode
We present the integration of an X-ray double-grating interferometer (XDGI) into an advanced, commercially available micro computed tomography system nanotomVR m with a transmission X-ray source and a micrometer-sized focal spot
Our results suggest that the extension of a commercially available lCT system via a grating interferometer offers potential to fill the gap between laboratory-based absorption-contrast lCT and phase-contrast lCT using synchrotron radiation or conventional X-ray sources in visualizing soft tissues
Summary
Micro computed tomography (lCT) based on the conventional X-ray sources usually operates in the absorption-contrast mode. Disadvantages of this technique are a limited contrast in materials composed of low atomic number elements and acquired values cannot be related to a local X-ray absorption as determination of an effective photon energy of a polychromatic spectrum is complex. Simultaneous visualization of soft and hard tissues is a challenge too. For an optimized choice of the photon energy, weak absorbing parts do not provide sufficient contrast, and staining procedures are often required, whereas hard parts show the streak and beam hardening artifact characteristics for low photon energies.
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