Comparison of in vivo lung morphometry models from 3D multiple b-value 3He and 129Xe diffusion-weighted MRI

Purpose To compare in vivo lung morphometry parameters derived from theoretical gas diffusion models, the cylinder model and stretched exponential model, in a range of acinar microstructural length scales encountered in healthy and diseased lungs with 3He and 129Xe diffusion‐weighted MRI. Methods Three‐dimensional multiple b‐value 3He and 129Xe diffusion‐weighted MRI was acquired with compressed sensing at 1.5 T from 51 and 31 subjects, respectively, including healthy volunteers, ex‐smokers, idiopathic pulmonary fibrosis, and chronic obstructive pulmonary disease patients. For each subject, the stretched exponential model–derived mean diffusive length scale (LmD) was calculated from the diffusion signal decay, and was compared with the cylinder model–derived mean chord length (Lm) and mean alveolar diameter (LAlv) in order to determine the relationships among the different lung morphometry parameters. Results For both 3He and 129Xe diffusion‐weighted MRI, the mean global LmD value was significantly related (P < .001) to Lm in a nonlinear power relationship, whereas the LAlv demonstrated excellent linear correlation (P < .001) with LmD. A mean bias of +1.0% and urn:x-wiley:07403194:media:mrm27608:mrm27608-math-00012.6% toward LmD was obtained for Bland‐Altman analyses of 3He and 129Xe LmD and LAlv values, suggesting that the two morphometric parameters are equivalent measures of mean acinar dimensions. Conclusion Within the experimental range of parameters considered here for both 3He and 129Xe, the stretched exponential model–derived LmD is related nonlinearly to cylinder model–derived Lm, and demonstrates excellent agreement with the cylinder model–derived LAlv

3D diffusion-weighted (129) Xe MRI for whole lung morphometry

PURPOSE: To obtain whole lung morphometry measurements from (129) Xe in a single breath-hold with 3D multiple b-value (129) Xe diffusion-weighted MRI (DW-MRI) with an empirically optimized diffusion time and compressed sensing for scan acceleration. METHODS: Prospective three-fold undersampled 3D multiple b-value hyperpolarized (129) Xe DW-MRI datasets were acquired, and the diffusion time (Δ) was iterated so as to provide diffusive length scale (LmD ) estimates from the stretched exponential model (SEM) that are comparable to those from (3) He. The empirically optimized (129) Xe diffusion time was then implemented with a four-fold undersampling scheme and was prospectively benchmarked against (3) He measurements in a cohort of five healthy volunteers, six ex-smokers, and two chronic obstructive pulmonary disease patients using both SEM-derived LmD and cylinder model (CM)-derived mean chord length (Lm). RESULTS: Good agreement between the mean (129) Xe and (3) He LmD (mean difference, 2.2%) and Lm (mean difference, 1.1%) values was obtained in all subjects at an empirically optimized (129) Xe Δ = 8.5 ms. CONCLUSION: Compressed sensing has facilitated single-breath 3D multiple b-value (129) Xe DW-MRI acquisitions, and results at (129) Xe Δ = 8.5 ms indicate that (129) Xe provides a viable alternative to (3) He for whole lung morphometry mapping with either the SEM or CM. Magn Reson Med, 2017. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited

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

Functional Imaging: CT and MRI

SYNOPSIS: Numerous imaging techniques permit evaluation of regional pulmonary function. Contrast-enhanced CT methods now allow assessment of vasculature and lung perfusion. Techniques using spirometric controlled MDCT allow for quantification of presence and distribution of parenchymal and airway pathology, Xenon gas can be employed to assess regional ventilation of the lungs and rapid bolus injections of iodinated contrast agent can provide quantitative measure of regional parenchymal perfusion. Advances in magnetic resonance imaging (MRI) of the lung include gadolinium-enhanced perfusion imaging and hyperpolarized helium imaging, which can allow imaging of pulmonary ventilation and .measurement of the size of emphysematous spaces

Hyperpolarised &quot;3He gas production for magnetic resonance imaging of the human air ways

This thesis describes the experimental techniques, and methods employed in hyperpolarised &quot;3He gas production and magnetic resonance imaging of the human air-ways, using spin-echo sequences and MR tagging techniques. An in-house polariser utilising the metastability optical pumping technique was constructed. The main results of this work are concerned with engineering difficulties involved in compressing HP &quot;3He and a large proportion of this PhD thesis details the design, construction, and performance of an in-house built peristaltic compressor. In preliminary imaging experiments using RARE, high signal to noise projection images of the lungs were acquired using less than 0.5 cm&quot;3 (STP) of purely polarised HP gas. Later, increased HP gas quantities (typically 10 cm&quot;3) were obtained by employing the peristaltic compressor. Consequently we could acquire 10 mm thick slices spanning the entire lung following a single &quot;3He gas bolus administration. Finally, the first results using MR tagging techniques in conjunction with &quot;3He imaging to track gas flow during an inspiratory and expiratory manoeuvre are presented. (author)Available from British Library Document Supply Centre- DSC:DXN058970 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

Increased dopaminergic activity in restricting-type anorexia nervosa

Eye blink rate, a peripheral measure of central dopaminergic activity, has been investigated in 20 female anorexic "restricting-type" patients and 16 healthy female subjects. A significantly increased blink rate was found in the anorexic patients. A significant positive correlation between blink rate and duration of illness was also found

What happens to eating disorder outpatients who withdrew from therapy?

OBJECTIVE: Dropouts are frequent among eating disorder (ED) patients, but less is known about their natural history. This paper assesses the outcome of outpatients who dropped out from a therapy programme and its possible causes. MATERIAL AND METHODS: From 1992 to 1994, we assessed 222 ED subjects. Psychiatrists expert in EDs evaluated these subjects by defining baseline parameters and diagnosis was made according to the 3rd revisioned edition of the Diagnostic and Statistical Manual of Mental Disorders. One hundred and twenty-eight subjects (57%) dropped out during the treatment. In 1997, we contacted them, reassessed the same baseline parameters and asked for a self-judgment about their social and clinical condition during the previous 2-5 years. Patients were classified as "improved" and "not improved" (stationary or worse) according to their social, physical and psychological condition. The relation between baseline condition and outcome was determined statistically. RESULTS: Seventy-one percent of subjects were "improved" and no deaths were recorded. A significant correlation was found between "duration of illness" and no treatment following a dropout. DISCUSSION: The high percentage of improvement among dropouts was unexpected. Shorter duration of illness and lack of specific therapy in the improved patients suggest the existence of a subset of ED patients with acute onset and a spontaneous tendency to improve. This point obviously requires further investigation