Monique C. Tourell

The distribution of the apparent diffusion coefficient as an indicator of the response to chemotherapeutics in ovarian tumour xenografts.

Diffusion-weighted magnetic resonance imaging (DW-MRI) was used to evaluate the effects of single-agent and combination treatment regimens in a spheroid-based animal model of ovarian cancer. Ovarian tumour xenografts grown in non-obese diabetic/severe-combined-immunodeficiency (NOD/SCID) mice were treated with carboplatin or paclitaxel, or combination carboplatin/paclitaxel chemotherapy regimens. After 4 weeks of treatment, tumours were extracted and underwent DW-MRI, mechanical testing, immunohistochemical and gene expression analyses. The distribution of the apparent diffusion coefficient (ADC) exhibited an upward shift as a result of each treatment regimen. The 99-th percentile of the ADC distribution (“maximum ADC”) exhibited a strong correlation with the tumour size (r2 = 0.90) and with the inverse of the elastic modulus (r2 = 0.96). Single-agent paclitaxel (n = 5) and combination carboplatin/paclitaxel (n = 2) treatment regimens were more effective in inducing changes in regions of higher cell density than single-agent carboplatin (n = 3) or the no-treatment control (n = 5). The maximum ADC was a good indicator of treatment-induced cell death and changes in the extracellular matrix (ECM). Comparative analysis of the tumours’ ADC distribution, mechanical properties and ECM constituents provides insights into the molecular and cellular response of the ovarian tumour xenografts to chemotherapy. Increased sample sizes are recommended for future studies. We propose experimental approaches to evaluation of the timeline of the tumour’s response to treatment.

Load-induced changes in the diffusion tensor of ovine anulus fibrosus: A pilot MRI study: Load-Induced Changes in Spinal Disc

To assess the feasibility of diffusion tensor imaging (DTI) for evaluating changes in anulus fibrosus (AF) microstructure following uniaxial compression.

T1-based sensing of mammographic density using single-sided portable NMR

A single‐sided NMR instrument was used to investigate the ability of the T1 relaxation constant to distinguish between regions of low and high mammographic density in human breast tissue.

Quantifying collagen fibre architecture in articular cartilage using small-angle X-ray scattering

Collagen fibre architecture in articular cartilage is commonly described in terms of the predominant direction of fibre alignment. X-ray scattering has been used to study the distribution of fibre orientations in cartilage. In this paper, a new methodology for the analysis of small-angle X-ray scattering (SAXS) patterns of articular cartilage in order to quantitatively determine the distribution of collagen fibre orientations in the tissue is presented. A simple three-component model was used to fit intensity data from SAXS patterns to separate diffraction maxima from general diffuse scatter. Deconvolution of angular distributions of intensities of diffraction maxima obtained from SAXS patterns of articular cartilage and ligament samples yielded fibre orientation distributions in the cartilage samples. The methodology developed in this study worked reliably on a large set of SAXS patterns collected from native, dehydrated and trypsin-treated articular cartilage samples. The methods can be extended to quantitative analysis of small or wide angle X-ray scattering patterns obtained from other collagenous materials.

Chapter 7: Quantification of articular cartilage microstructure by the analysis of the diffusion tensor

In this chapter, we present approaches to the numerical simulation of the diffusion of water molecules in fibre networks that serve as models of articular cartilage. The simulations are intended as a tool for the translation of experimental diffusion magnetic resonance imaging (MRI) data into quantitative microstructural and compositional characteristics of articular cartilage. The chapter begins with a brief introduction to diffusion nuclear magnetic resonance and diffusion imaging, focusing on diffusion tensor imaging. It discusses the current limitations of diffusion MRI in quantifying articular cartilage microstructure beyond the predominant direction of collagen fibre alignment. We then detail the construction of aligned and partially aligned networks of fibres that can serve as models of articular cartilage. We discuss the methods for the simulation of the diffusion of tracer molecules through the model networks (especially Langevin dynamics and Monte Carlo techniques), and reconstruction of the diffusion tensor from the simulated molecular trajectories. The aim of these simulations is to quantitatively link the eigenvalues and the fractional anisotropy of cartilage diffusion tensor to collagen fibre volume fraction and the degree of collagen fibre alignment. The global aim of this work is to move diffusion tensor imaging of articular cartilage beyond determination of the predominant direction of fibre alignment, and towards quantification of the fibre orientation distribution.

Assessment of collagen fiber orientation dispersion in articular cartilage by small-angle X-ray scattering and diffusion tensor imaging: Preliminary results

Measurements of the orientational dispersion of collagen fibers in articular cartilage were made using diffusion tensor imaging (DTI) and small-angle X-ray scattering (SAXS) on matched bovine articular cartilage samples. Thirteen pairs of samples were excised from bovine knee joints; each pair was taken from neighboring locations in the same bone. One sample from each pair was used for DTI measurements and the other for SAXS measurements. Fractional anisotropy (FA) values were calculated from the DTI data both for the individual imaging voxels and for whole regions of interest (ROI). The FA values were used as a measure of fiber dispersion and compared to the ellipticities of the fiber orientation distributions obtained from SAXS. Neither the spatially-resolved FA values nor whole-ROI FA values showed any correlation with SAXS ellipticities. We attribute the lack of DTI-SAXS correlation to two principal factors: (1) the significant difference in the imaging resolution of the two techniques; and (2) the inherent limitations of both the SAXS data analysis methodology and the diffusion tensor model in the case of multi-modal fiber orientation distributions. We discuss how these factors could be overcome in future work.

Corrigendum: Diffusion tensor of water in partially aligned fibre networks (2013 J. Phys. D: Appl. Phys. 46 455401)

This is a corrigendum for the article 2013 J. Phys. D: Appl. Phys. 46 455401 ePrints 63904