A nuclear magnetic resonance study of molecular disorder in the solid state of some medium ring hydrocarbons

Since the discovery of nuclear magnetic resonance in bulk matter in 1945, n.m.r studies of molecular motion in solids have provided a powerful insight into the details of molecular reorientation processes that occur in solids. By studying the variation of the n.m.r. parameters as a function of temperature it is usually possible to obtain information regarding such phenomena as solid-solid phase transitions, including the anomalous behaviour of heat capacity associated with order-disorder and co-operative processes, rotational disorder and self-diffusion. In suitable cases it is possible to estimate the origin and magnitude of the potential barriers of the crystalline field which hinder the various reorientation processes. The cycloalkane ring series (CH₂)[sub]n from cyclopropane n =3 to cyclohexane n=6 have all previously been studied in the solid state by n.m.r. The results indicate that considerable molecular mobility occurs in the solid state o these substances and that in general the solid-solid phase transitions detected by hear capacity measurements are associated with the onset of molecular reorientation and in some cases self-diffusion. The current interest in the molecular configuration of the medium ring hydrocarbons, and the extensive study by Finke et al. (1956) of the low temperature thermal properties of cycloheptane n=7, and cyclooctane n=8, showing three and two solid-solid phase transitions respectively, prompted an n.m.r. study of cycloheptane and cyclooctane. The results of this investigation together with those of a related seven membered ring hydrocarbon 1, 3, 5 cycloheptatriene C₇H₈ are presented in this thesis, and show that extensive molecular motion exists well below the melting points of all three substances, and information is given regarding the form of the motion in the various crystalline phases

Imaging of lung function using hyperpolarized helium-3 magnetic resonance imaging: Review of current and emerging translational methods and applications

During the past several years there has been extensive development and application of hyperpolarized helium-3 (HP (3)He) magnetic resonance imaging (MRI) in clinical respiratory indications such as asthma, chronic obstructive pulmonary disease, cystic fibrosis, radiation-induced lung injury, and transplantation. This review focuses on the state-of-the-art of HP (3)He MRI and its application to clinical pulmonary research. This is not an overview of the physics of the method, as this topic has been covered previously. We focus here on the potential of this imaging method and its challenges in demonstrating new types of information that has the potential to influence clinical research and decision making in pulmonary medicine. Particular attention is given to functional imaging approaches related to ventilation and diffusion-weighted imaging with applications in chronic obstructive pulmonary disease, cystic fibrosis, asthma, and radiation-induced lung injury. The strengths and challenges of the application of (3)He MRI in these indications are discussed along with a comparison to established and emerging imaging techniques

Pulmonary CT and MRI phenotypes that help explain chronic pulmonary obstruction disease pathophysiology and outcomes

Pulmonary x-ray computed tomographic (CT) and magnetic resonance imaging (MRI) research and development has been motivated, in part, by the quest to subphenotype common chronic lung diseases such as chronic obstructive pulmonary disease (COPD). For thoracic CT and MRI, the main COPD research tools, disease biomarkers are being validated that go beyond anatomy and structure to include pulmonary functional measurements such as regional ventilation, perfusion, and inflammation. In addition, there has also been a drive to improve spatial and contrast resolution while at the same time reducing or eliminating radiation exposure. Therefore, this review focuses on our evolving understanding of patient-relevant and clinically important COPD endpoints and how current and emerging MRI and CT tools and measurements may be exploited for their identification, quantification, and utilization. Since reviews of the imaging physics of pulmonary CT and MRI and reviews of other COPD imaging methods were previously published and well-summarized, we focus on the current clinical challenges in COPD and the potential of newly emerging MR and CT imaging measurements to address them. Here we summarize MRI and CT imaging methods and their clinical translation for generating reproducible and sensitive measurements of COPD related to pulmonary ventilation and perfusion as well as parenchyma morphology. The key clinical problems in COPD provide an important framework in which pulmonary imaging needs to rapidly move in order to address the staggering burden, costs, as well as the mortality and morbidity associated with COPD