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Quantitative Measure of Lung Structure and Function Obtained from Hyperpolarized Xenon Spectroscopy

Hyperpolarized Xenon-129 (HXe) magnetic resonance imaging (MRI) provides tools for obtaining 2- or 3-dimensional maps of lung ventilation patterns, gas ...

University of Pennsylvania

To demonstrate the feasibility of using a 3D radial double golden-means acquisition with variable flip angles to monitor pulmonary gas transport in a single breath hold with hyperpolarized xenon-129 MRI.

Rapid assessment of pulmonary gas transport with hyperpolarized 129Xe MRI using a 3D radial double golden-means acquisition with variable flip angles.

Many forms of lung disease manifest themselves as pathological changes in the transport of gas to the circulatory system, yet the difficulty of imaging this process remains a central obstacle to the comprehensive diagnosis of lung disorders. Using hyperpolarized xenon-129 as a surrogate marker for oxygen, we derived the temporal dynamics of gas transport from the ratio of two lung images obtained with different timing parameters. Additionally, by monitoring changes in the total hyperpolarized xenon signal intensity in the left side of the heart induced by depletion of xenon signal in the alveolar airspaces of interest, we quantified the contributions of selected lung volumes to the total pulmonary gas transport. In a rabbit model, we found that it takes at least 200 ms for xenon gas to enter the lung tissue and travel the distance from the airspaces to the heart. Additionally, our method shows that both lungs contribute fairly equally to the gas transport in healthy rabbits, but that this ratio changes in a rabbit model of acid aspiration. These results suggest that hyperpolarized xenon-129 MRI may improve our ability to measure pulmonary gas transport and detect associated pathological changes.

Assessment of Pulmonary Gas Transport in Rabbits Using Hyperpolarized Xenon-129 Magnetic Resonance Imaging.

To investigate the feasibility of describing the impact of any flip angle-TR combination on the resulting distribution of the hyperpolarized xenon-129 (HXe) dissolved-phase magnetization in the chest using a single virtual parameter, TR .

Assessment of flip angle-TR equivalence for standardized dissolved-phase imaging of the lung with hyperpolarized 129Xe MRI.

In this study, we compared a newly developed multibreath simultaneous alveolar oxygen tension and apparent diffusion coefficient (PO-ADC) imaging sequence to a single-breath acquisition, with the aim of mitigating the compromising effects of intervoxel flow and slow-filling regions on single-breath measurements, especially in chronic obstructive pulmonary disease (COPD) subjects.

Multibreath Hyperpolarized He Imaging Scheme to Measure Alveolar Oxygen Tension and Apparent Diffusion Coefficient.

While hyperpolarized xenon-129 (HXe) MRI offers a wide array of tools for assessing functional aspects of the lung, existing techniques provide only limited quantitative information about the impact of an observed pathology on overall lung function. By selectively destroying the alveolar HXe gas phase magnetization in a volume of interest and monitoring the subsequent decrease in the signal from xenon dissolved in the blood inside the left ventricle of the heart, it is possible to directly measure the contribution of that saturated lung volume to the gas transport capacity of the entire lung. In mechanically ventilated rabbits, we found that both xenon gas transport and transport efficiency exhibited a gravitation-induced anterior-to-posterior gradient that disappeared or reversed direction, respectively, when the animal was turned from supine to prone position. Further, posterior ventilation defects secondary to acute lung injury could be re-inflated by applying positive end expiratory pressure, although at the expense of decreased gas transport efficiency in the anterior volumes. These findings suggest that our technique might prove highly valuable for evaluating lung transplants and lung resections, and could improve our understanding of optimal mechanical ventilator settings in acute lung injury.

Measurement of Regional 2D Gas Transport Efficiency in Rabbit Lung Using Hyperpolarized 129Xe MRI.

To investigate biases in the measurement of apparent alveolar septal wall thickness (SWT) with hyperpolarized xenon-129 (HXe) as a function of acquisition parameters.

Investigating biases in the measurement of apparent alveolar septal wall thickness with hyperpolarized 129Xe MRI.

Prone ventilation redistributes lung inflation along the gravitational axis; however, localized, nongravitational effects of body position are less well characterized. The authors hypothesize that positional inflation improvements follow both gravitational and nongravitational distributions. This study is a nonoverlapping reanalysis of previously published large animal data.

Positional Therapy and Regional Pulmonary Ventilation.

To demonstrate the feasibility of generating red blood cell (RBC) and tissue/plasma (TP)-specific gas-phase (GP) depolarization maps using xenon-polarization transfer contrast (XTC) MR imaging.

Measuring pulmonary gas exchange using compartment-selective xenon-polarization transfer contrast (XTC) MRI.

This study aims to develop and validate a parametric response mapping (PRM) methodology to accurately identify diseased regions of the lung by using variable thresholds to account for alterations in regional lung function between the gravitationally-independent (anterior) and gravitationally-dependent (posterior) lung in CT images acquired in the supine position.

Deriving Regionally Specific Biomarkers of Emphysema and Small Airways Disease Using Variable Threshold Parametric Response Mapping on Volumetric Lung CT Images.

Simultaneous Imaging of Ventilation and Gas Exchange with Hyperpolarized Xe MRI for Monitoring Patients with Endobronchial Valve Interventions.

To demonstrate the utility of continuous-wave (CW) saturation pulses in xenon-polarization transfer contrast (XTC) MRI and MRS, to investigate the selectivity of CW pulses applied to dissolved-phase resonances, and to develop a correction method for measurement biases from saturation of the nontargeted dissolved-phase compartment.

Investigating the impact of RF saturation-pulse parameters on compartment-selective gas-phase depolarization with xenon polarization transfer contrast MRI.

To demonstrate the feasibility of a multi-breath xenon-polarization transfer contrast (XTC) MR imaging approach for simultaneously evaluating regional ventilation and gas exchange parameters.

Faraz Amzajerdian

Department of Radiology

University of Pennsylvania

Quantitative Measure of Lung Structure and Function Obtained from Hyperpolarized Xenon Spectroscopy

Faraz Amzajerdian

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Radiology

University of Pennsylvania

Quantitative Measure of Lung Structure and Function Obtained from Hyperpolarized Xenon Spectroscopy

Department of Radiology