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Item Heart failure is independently associated with white matter lesions: insights from the population-based LIFE-Adult Study(John Wiley and Sons Ltd on behalf of European Society of Cardiology, 2021-02) Stegmann T; Chu ML; Witte VA; Villringer A; Kumral D; Riedel-Heller SG; Roehr S; Hagendorff A; Laufs U; Loeffler M; Wachter R; Zeynalova SAims White matter lesions (WML) are common structural alterations in the white matter of the brain and their prevalence increases with age. They are associated with cerebral ischaemia and cognitive dysfunction. Patients with heart failure (HF) are at risk for cognitive decline. We hypothesized that the presence and duration of HF are associated with WML. Methods and results The LIFE-Adult Study is a population-based study of 10 000 residents of Leipzig, Germany. WML were quantitated in 2490 participants who additionally underwent cerebral MRI using the Fazekas score. Mean age was 64 years, and 46% were female; 2156 (86.6%) subjects had Fazekas score of 0–1, and 334 (13.4%) had Fazekas score of 2–3. Thirty participants had a medical history of HF, 1019 had hypertension, and 51 had a history of stroke. Median left ventricular ejection fraction of the participants with HF was 57% (interquartile ranges 54–62). Age, troponin T, NT-proBNP, body mass index, history of acute myocardial infarction, stroke, HF, and diabetes were positively associated with WML in univariate analysis. On multivariate analysis, age, hypertension, stroke, and HF were independently associated with WML. The odd's ratio for the association of WML (Fazekas 2–3) with HF was 2.8 (95% CI 1.2–6.5; P = 0.019). WML increased with longer duration of HF (P = 0.036 for trend). Conclusions In addition to age, hypertension, and stroke, the prevalence and duration of HF are independently associated with WML. This observation sets the stage to investigate the prognostic value of WML in HF and the impact of HF therapies on WML.Item Susceptibility, diffusion and relaxation contrast in NMR microscopy at high resolution : a thesis presented in partial fulfilment of the requirement for the degree of Master of Science in physics at Massey University(Massey University, 1994) Forde, Lucy CatherineAn integrated approach to the functional NMR imaging of plant tissue at moderately-high transverse resolution (23 µm) was undertaken. Attention was paid to all the possible commonly-known influences, such as sources of nuclear spin relaxation or of artefacts, relevant to the final image intensity of the different tissues. While it was not clear at the outset which influences might prove to be significant, two phenomena in particular, susceptibility inhomogeneity and correlated diffusion effects, were selected for detailed investigation using simple model systems constructed from small glass tubes and rods combined with aqueous solutions, before continuing on to more complex plant samples. Simulated images compared well with the experimental results in these studies. Preliminary images of a stem of an intact Stachys sylvatica L. plant showed that the apparent T₂ relaxation time is much less (an order of magnitude) than the T₁ relaxation time in all tissues. A range of diagnostic pulse sequences was then carried out on this and similar stems in order to reveal the signatures for different models of T₂ relaxation which might explain this fact (assuming that the water protons imaged fall within the extreme-narrowed region of Bloembergen, Purcell and Pound theory). It was found that measures were necessary to avoid the complicating factor of attenuation due to diffusion in the applied read gradient, specifically the use of Carr-Purcell-Meiboom-Gill (CPMG) refocusing pulses. Susceptibility inhomogeneity seemed important in sensitive gradient echo images, but further experiments at different B₀ strengths revealed that it (and chemical shift exchange) does not contribute significantly to the spin echo image contrast. The Brownstein-Tarr model of relaxation at boundaries and surfaces (without local field offsets) was also considered as a possibility, but was ruled out for at least some of the tissues (those which display a CPMG pulse-spacing dependence). Another alternative explanation is short-range dipole interactions between water protons and protons of more slowly-moving molecules, which should be abundant in the particular cells which escape the other hypotheses, but it is difficult to confirm this within the scope of the pulse sequences used here. More progress might be possible with proper multicomponent T₂ analysis and improved knowledge of subcellular structure of our particular tissues.Item Static and dynamic imaging using magnetic field gradients = Jingtai yu dongtai heci chengxiang : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Physics at Massey University(Massey University, 1988) Xia, YangThe theory and techniques of NMR imaging are described together with a detailed description of the Filtered Back Projection (FBP) technique used in an existing NMR imaging system. The existing 'static' NMR imaging system has been modified to be capable of performing 'dynamic' NMR imaging experiments, as well as better 'static' NMR imaging experiments. The potential of NMR microscopy in the imaging of both the static spin distribution P(rₒ) and the dynamic spin correlation function P(rₒ|r,t)has been investigated. Both homogeneous and inhomogeneous systems have been studied. Detailed theoretical analysis and experimental considerations of dynamic imaging experiments have been given. A transverse resolution of 15 µm for a 1 mm slice thickness is obtained from a static imaging experiment of a phantom using the modified system. The rabbit trachea imaging experiment has revealed the asymmetrical collapse of tracheas under negative pressures, a collapse which had previously been considered as symmetrical process. The Poiseuille flow experiment has involved the first simultaneous measurement of flow and diffusion at the microscopic level. Maps of two dimensional distribution functions of flow and diffusion are given by this experiment, highlighting this totally non-invasive dynamic imaging technique. As an example of dynamic imaging, the wheat grain experiment has displayed the flow and diffusion maps within a single wheat grain in vivo.Item Magnetic resonance spectroscopy and imaging as applied to the forestry sector : a thesis submitted to Massey University in partial fulfilment for the degree of Doctor of Philosophy(Massey University, 2003) Meder, Albert RogerThe forestry sector in New Zealand ranks as the third largest export earner. The individual industries within the forestry sector have, in some cases, grown up on the basis of institutionalised knowledge, sometimes without a full understanding of the underlying fundamental physico-chemical relationships and the changes that occur during wood material processing. At the same time the commercial pressures of operating within the forestry sector have resulted in demand for more uniform, high quality, fit-for-purpose product, faster throughput and less downgrade from what is becoming a lower quality feedstock as harvest ages decline. In the 21st century, the forestry sector is being transformed into an "engineered ligno-cellulosic materials processor" and this in turn is requiring a more sophisticated knowledge of the material feedstock and the processes involved in wood products manufacture. The aim of this work was to use magnetic resonance techniques to explore aspects of ligno-cellulosic materials processing at points along the value-added process chain, namely drying, chemical modification (preservation) and re-engineering (gluing) of wood products. Magnetic resonance mini-imaging studies of the water transport during the drying of radiata pine boards rave shown differences in the directional movement of water within the wood structure. These effects show a dependence on the surface area to volume ratio of timber and the orientation of the annual rings with respect to the larger drying face. Narrow, flat-sawn boards exhibit anomalous drying behaviour in terms of water mass transport, whereas thicker boards display more conventional core-shell drying behaviour. These restrictions to flow have been further investigated using diffusion tensor imaging via a modified pulsed field gradient spin-echo sequence to elucidate the nature of anisotropic diffusion in wood. The direction of least restriction to self-diffusion is in the longitudinal direction, as would be expected with it being the direction of active transport within a tree stem, whereas the direction of greatest restriction to self-diffusion is in the radial direction, with the higher density latewood acting as a barrier. Preservation of radiata pine sapwood with novel boron-based preservatives has been investigated using magnetic resonance imaging to determine the penetration and retention of the incipient compounds. An apparent anomaly in retention for trimethylborate-treated Pinus radiata sapwood was investigated by 11B MAS NMR spectroscopy of excised sections of latewood and earlywood, which showed hydrolytic decomposition of trimethyl borate to form boric acid. The rate of hydrolysis of trimethylborate was monitored by 11B MAS NMR spectroscopy and was shown to occur very rapidly in the latewood (within 24 hours), and over a longer time scale of several days in the earlywood. The resulting publication has reported some of the first published 11B MRI images. Magnetic resonance spectroscopy has provided (in conjunction with separate mass spectrometry studies) mechanistic evidence for the accelerated curing of phenol-resorcinol formaldehyde resols, using ammonia in combination with the conventional paraformaldehyde hardener - a process known as GreenWeldTM. Carbon-13 and nitrogen-15 NMR spectroscopy has shown evidence of both benzylamine and aniline type bridging structures formed during cure, compared to only methylene structures being formed under conventional curing conditions. Poly(vinyl acetate) emulsion polymer adhesive has also been examined using NMR spectroscopic methods, with particular focus on the effect of addition of aluminium chloride, which is often commercially added to PVAc formulations as a crosslinking agent. Multinuclear magnetic resonance spectra obtained during the cure of AlCl3 modified PV Ac adhesive, shows a low frequency 27 Al shift of ca. 3 ppm suggesting a local change in environment as the aluminium changes from a solvated to a covalently bonded octahedral environment. Finally, as a preliminary study, a new device for measuring uniaxial extension of visco-elastic solids was trialled on poly(vinyl acetate) hydrogels to study the effect of addition of aluminium chloride on the visco-elastic properties of the adhesive. A similar, manually operated device was used to obtain NMR spectroscopic data during compression of the gel. These studies have shown that addition of aluminium chloride as a crosslinking agent, in fact produces a cured adhesive with fewer crosslinks than the corresponding unmodified adhesive, but with increased resistance to shear-induced creep.