Cancer belongs to the primary diseases these days. Although different successful treatments including surgery, chemical, pharmacological, and radiation therapies are established, the aggressive proliferation of cancerous cells and the related formation of blood vessels has to be better understood to develop more powerful strategies against the different kinds of cancer. Angiogenesis is one of the crucial steps for the survival and metastasis formation of malignant tumors. Although therapeutic strategies attempting to inhibit these processes are being developed, the biological regulation is still unclear. This study concentrates on the three-dimensional morphology of vessels formed in a mouse tumor xenograft model post mortem. Synchrotron radiation-based micro computed tomography (SRµCT) could provide the necessary information that is essential for validating the simulations. Using mouse and human brain tissue, the different approaches to extract the vessel tree from SRµCT data are discussed. These approaches include corrosion casting, the application of contrast agents such as barium sulfate, tissue embedding, all of them regarded as materials science based. Alternatively, phase contrast tomography was used, which gave rise to promising results but still not reaches the spatial resolution to uncover the smallest capillaries.

A key issue in developing strategies against diseases such as cancer is the analysis of the vessel tree in comparison to the healthy one. In the search for parameters that might be characteristic for tumor capillaries we study the vascularization in mice for cancerous and healthy tissues using synchrotron radiation-based micro computed tomography in absorption and phase contrast modes. Our investigations are based on absorption tomograms of casted healthy and cancerous tissues as well as a phase tomogram of a fixated tumor. We demonstrate how the voxel-based tomography data can be vectorized to assess the capillary networks quantitatively. The processing includes segmentation, skeletonization, and vectorization to finally extract the vessel parameters. The mean diameter of capillaries in healthy and cancerous tissues corresponds to (8.0±1.1) μm and (3.9±1.1) μm, respectively. Further evaluated parameters show marginal or no differences between capillaries in healthy and cancerous tissues, namely fractal dimension 2.3±0.3 vs. 2.3±0.2, tortuosity (SOAM) 0.18 rad/μm vs. 0.24 rad/μm and vessel length 20 μm vs. 17 μm. The bifurcation angles exhibit a narrow distribution around 115°. Furthermore, we show that phase tomography is a powerful alternative to absorption tomography of casts for the vessel visualization omitting any invasive specimen preparation procedure.

We report on a study on the accuracy and precision of X-ray phase and absorption tomograms obtained with a grating interferometer using monochromatic synchrotron radiation. The quantitative assessment of the performances of the X-ray interferometer is a fundamental aspect in the interpretation of the results obtained with this device. The work presented in this paper consists in the comparison of experimental with calculated three-dimensional distributions of the X-ray refractive index in a phantom sample made of known materials. The quality of phase and absorption tomograms has been determined with respect to their sensitivity and contrast-to-noise ratios. Moreover, the effect of image artifacts typical in phase contrast imaging based on the phase-stepping technique, especially stripe features generated by the phase wrapping phenomenon, has been investigated by comparison with numerical simulations. The results show that the artifacts cannot only be qualitatively explained by the calculations, but they can even be quantitatively reproduced.

International audienceX-ray phase-contrast imaging techniques are used at synchrotron facilities to visualize tiny density variations in bulk samples. They overcome the limitations of other non-destructive methods, which often provide insufficient spatial and/or density resolution. Holotomography (HT) and X-ray grating interferometry (XGI) are among the most powerful phase-contrast techniques. Here, we show a direct comparison of HT versus XGI. We find that XGI excels in fidelity of the density measurements and is more robust against low-frequency artifacts, while HT is superior in spatial resolution. This study gives indications for applications and developments of phase-contrast imaging