Vol 47, No 12 (2016)

In this work, the distributions of spin–lattice and spin–spin relaxation times of nuclear magnetic resonance are used to characterize the mobility of different parts of the polymer macromolecules and to analyze the crosslink density of the polymer chains. A change in the distribution of relaxation times is applied to detect the changes of the polymers quality caused by the influence of ozone, ultraviolet radiation, temperature cycling, and stretching deformation.

The aim of this work is to show that the bones with marrow, treated as a quasi-porous media, can be successfully used to study the effects of ovariectomy-induced osteoporosis. Proton one-dimensional (1D) nuclear magnetic resonance (NMR) T₂-distribution and two-dimensional (2D) T₂–T₂ exchange maps combined with histological images were used to measure the proximal part of the femoris, diaphysis and distal epiphysis of ovariectomized and non-ovariectomized Wistar albino rats. The 1D normalized T₂ distributions showed four peaks which were associated with protons in four major pools: (1) the protons from bounded water to collagenous matrix; (2) fluids in osteocyte lacunae and canaliculi channels; (3) fluids in secondary pores like Haversian and transverse Volkmann canals and (4) soft matter like bone marrow and fluids in primary pores like trabecular bone cavities. The peak’s association and hierarchical structure of pores in femoral bone were supported by a 2D T₂–T₂ exchange map and by a series of dehydration experiments monitored by NMR measurements. The bone marrow narrows the T₂-distributions, increasing resolution, but will not influence significantly the peaks positions; therefore, the NMR relaxometry is a valuable tool to characterize the pore distributions and effects of induced osteoporosis in diverse bones sections.

The effect of cellulose ethers (CE) and limestone filler added in nowadays receipts to improve some thermal and hygroscopic properties of construction materials based on plaster mortar were evaluated by ¹H 1D nuclear magnetic resonance (NMR) T₂-distributions, distribution of pore size distribution, scanning electron microscopy images and compressive testing. The CE polymer is used in three concentrations of 0.5, 1.0 and 2.0 % from cement mass, and the limestone filler was used into a fixed concentration of 10 % from cement mass. The ¹H 1D NMR Carr-Purcell-Meiboom-Gill decays measured for all samples were analyzed by inverse Laplace transform leading to a series of T₂-distributions generally characterized by four peaks associated, from low to high T₂-values, with bound water to cement components, and then with small, medium and large pores. A series of measurements were performed at 28 days after sample preparation, and then the samples were stored for 2 months in water in order for the pores to be saturated and measured again. From the ¹H 1D NMR T₂-distributions, into a spherical pores approximation, the distributions of pores sizes were calculated and characterized. For all samples a series of SEM images were recorded with different magnitudes and which, in particular were used to estimate the surface relaxivity factor used in the determination of pores distributions. We estimate the effect of CE polymer and limestone filler on the compression rate which was also correlated with the bound water percentage.

Parallel magnetic resonance imaging (PMRI) has the potential to reduce the MRI scan time by acquiring fewer k-space lines using multiple independent receiver coils instead of a single coil for data acquisition. Many advance reconstruction algorithms have been proposed in the recent past to reconstruct fully sampled images from these undersampled data. These algorithms are mainly categorized into k-space and image domain methods. The work presented in this paper develops an interactive graphical user interface (GUI) tool for a variety of advance reconstruction algorithms in MRI, namely, sensitivity encoding (SENSE) [1], conjugate gradient SENSE (CG-SENSE) [2], compressed sensing [3], and radial GRAPPA algorithms [4–7]. The proposed GUI tool environment is a multiple window interface developed using MATLAB (R2013a). The user has the option of loading the undersampled data in an interactive fashion, and image reconstruction can be performed using any of the available algorithms. The quality of the reconstructed images is evaluated using artifact power (AP) and SNR maps. This interactive platform is aimed at providing the researchers and medical practitioners an easy and interactive tool to test their data using various advance reconstruction algorithms in MRI.