A Comparison and Catalog of Intrinsic Tumor Growth Models

Determining the dynamics and parameter values that drive tumor growth is of great interest to mathematical modelers, experimentalists and practitioners alike. We provide a basis on which to estimate the growth dynamics of ten different tumors by fitting growth parameters to at least five sets of published experimental data per type of tumor. These timescale tumor growth data are also used to determine which of the most common tumor growth models (exponential, power law, logistic, Gompertz, or von Bertalanffy) provides the best fit for each type of tumor. In order to compute the best-fit parameters, we implemented a hybrid local-global least squares minimization algorithm based on a combination of Nelder-Mead simplex direct search and Monte Carlo Markov Chain methods

Quantitative imaging using high-energy X-ray phase-contrast CT with a 70 kVp polychromatic X-ray spectrum

Imaging of large and dense objects with grating-based X-ray phase-contrast computed tomography requires high X-ray photon energy and large fields of view. It has become increasingly possible due to the improvements in the grating manufacturing processes. Using a high-energy X-ray phase-contrast CT setup with a large (10 cm in diameter) analyzer grating and operated at an acceleration tube voltage of 70 kVp, we investigate the complementarity of both attenuation and phase contrast modalities with materials of various atomic numbers (Z). We confirm experimentally that for low-Z materials, phase contrast yields no additional information content over attenuation images, yet it provides increased contrast-to-noise ratios (CNRs). The complementarity of both signals can be seen again with increasing Z of the materials and a more comprehensive material characterization is thus possible. Imaging of a part of a human cervical spine with intervertebral discs surrounded by bones and various soft tissue types showcases the benefit of high-energy X-ray phase-contrast system. Phase-contrast reconstruction reveals the internal structure of the discs and makes the boundary between the disc annulus and nucleus pulposus visible. Despite the fact that it still remains challenging to develop a high-energy grating interferometer with a broad polychromatic source with satisfactory optical performance, improved image quality for phase contrast as compared to attenuation contrast can be obtained and new exciting applications foreseen

X-ray fluorescence analysis of long-term changes in the levels and distributions of trace elements in the rat brain following mechanical injury

This paper describes the results of the application of X-ray fluorescence microscopy to the qualitative, topographic and quantitative elemental analysis of nervous tissue from rats with neocortical brain injury. The tissue samples were analyzed with a 15 μm beam defined by the size of the polycapillary focus. Raster scanning of the samples generated 2D cartographies, revealing the distributions of elements such as P, S, Cl, K, Ca, Fe, Cu, and Zn. Special emphasis was placed on the analysis of the areas neighboring the lesion site and the hippocampal formation tissue. The results obtained for rats with mechanical brain injuries were compared with those recorded for controls and animals with pilocarpine-induced seizures. There were no significant differences in the elemental compositions of gray and white matter between injured and uninjured brain hemispheres. A higher level of Ca was observed in the gray matter of both of the hemispheres in brains with neocortical injuries. A similar relation was noticed for Fe in the white matter. A comparative study of hippocampal formation tissue showed a statistically significant decrease in the mass per unit area of P in the dentate gyrus (DG) and the hilus (H) of DG for animals with brain lesions in comparison with the control group. Analogous relations were found for Cu in the DG and Zn in sector 3 of Ammon’s horn (CA3) and the DG. It is important to note that identical changes in the same areas were observed for animals with pilocarpine-induced seizures in our previous study

Computer vision quantification of whole-body Parkinsonian bradykinesia using a large multi-site population.

Parkinson's disease (PD) is a common neurological disorder, with bradykinesia being one of its cardinal features. Objective quantification of bradykinesia using computer vision has the potential to standardise decision-making, for patient treatment and clinical trials, while facilitating remote assessment. We utilised a dataset of part-3 MDS-UPDRS motor assessments, collected at four independent clinical and one research sites on two continents, to build computer-vision-based models capable of inferring the correct severity rating robustly and consistently across all identifiable subgroups of patients. These results contrast with previous work limited by small sample sizes and small numbers of sites. Our bradykinesia estimation corresponded well with clinician ratings (interclass correlation 0.74). This agreement was consistent across four clinical sites. This result demonstrates how such technology can be successfully deployed into existing clinical workflows, with consumer-grade smartphone or tablet devices, adding minimal equipment cost and time