Pulmonary MRI with hyperpolarized xenon-129 demonstrates novel alterations in gas transfer across the air-blood barrier in asthma.

Background: Individuals with asthma can vary widely in clinical presentation, severity, and pathobiology. Hyperpolarized xenon-129 (Xe129) MRI is a novel imaging method to provide 3-D mapping of both ventilation and gas exchange in the human lung.

Purpose: To evaluate the functional changes in adults with asthma as compared to healthy controls using Xe129 MRI.

Hyperpolarized Xenon-129: A New Tool to Assess Pulmonary Physiology in Patients with Pulmonary Fibrosis.

Purpose: The existing tools to quantify lung function in interstitial lung diseases have significant limitations. Lung MRI imaging using inhaled hyperpolarized xenon-129 gas (Xe) as a contrast agent is a new technology for measuring regional lung physiology. We sought to assess the utility of the Xe MRI in detecting impaired lung physiology in usual interstitial pneumonia (UIP).

Comparison of Hyperpolarized He and Xe MR Imaging in Cystic Fibrosis Patients.

Purpose: In this study, we compared hyperpolarized He and Xe images from patients with cystic fibrosis using two commonly applied magnetic resonance sequences, standard gradient echo (GRE) and balanced steady-state free precession (TrueFISP) to quantify regional similarities and differences in signal distribution and defect analysis.

Materials And Methods: Ten patients (7M/3F) with cystic fibrosis underwent hyperpolarized gas MR imaging with both He and Xe. Six had MRI with both GRE, and TrueFISP sequences and four patients had only GRE sequence but not TrueFISP.

Single-Session Bronchial Thermoplasty Guided by Xe Magnetic Resonance Imaging. A Pilot Randomized Controlled Clinical Trial.

Adverse events have limited the use of bronchial thermoplasty (BT) in severe asthma. We sought to evaluate the effectiveness and safety of using Xe magnetic resonance imaging (Xe MRI) to prioritize the most involved airways for guided BT. Thirty subjects with severe asthma were imaged with volumetric computed tomography and Xe MRI to quantitate segmental ventilation defects.

Hyperpolarized Gas Magnetic Resonance Lung Imaging in Children and Young Adults.

The assessment of early pulmonary disease and its severity can be difficult in young children, as procedures such as spirometry cannot be performed on them. Computed tomography provides detailed structural images of the pulmonary parenchyma, but its major drawback is that the patient is exposed to ionizing radiation. In this context, magnetic resonance imaging (MRI) is a promising technique for the evaluation of pediatric lung disease, especially when serial imaging is needed.

Detecting pulmonary capillary blood pulsations using hyperpolarized xenon-129 chemical shift saturation recovery (CSSR) MR spectroscopy.

Purpose: To investigate whether chemical shift saturation recovery (CSSR) MR spectroscopy with hyperpolarized xenon-129 is sensitive to the pulsatile nature of pulmonary blood flow during the cardiac cycle.

Methods: A CSSR pulse sequence typically uses radiofrequency (RF) pulses to saturate the magnetization of xenon-129 dissolved in lung tissue followed, after a variable delay time, by an RF excitation and subsequent acquisition of a free-induction decay. Thereby it is possible to monitor the uptake of xenon-129 by lung tissue and extract physiological parameters of pulmonary gas exchange.

Assessment of lung function in asthma and COPD using hyperpolarized 129Xe chemical shift saturation recovery spectroscopy and dissolved-phase MRI.

Magnetic-resonance spectroscopy and imaging using hyperpolarized xenon-129 show great potential for evaluation of the most important function of the human lung -- gas exchange. In particular, chemical shift saturation recovery (CSSR) xenon-129 spectroscopy provides important physiological information for the lung as a whole by characterizing the dynamic process of gas exchange, while dissolved-phase (DP) xenon-129 imaging captures the time-averaged regional distribution of gas uptake by lung tissue and blood. Herein, we present recent advances in assessing lung function using CSSR spectroscopy and DP imaging in a total of 45 subjects (23 healthy, 13 chronic obstructive pulmonary disease (COPD) and 9 asthma).

Quantification of human lung structure and physiology using hyperpolarized 129Xe.

Purpose: To present in vivo, human validation of a previously proposed method to measure key pulmonary parameters related to lung microstructure and physiology. Some parameters, such as blood-air barrier thickness, cannot be measured readily by any other noninvasive modality.

Methods: Healthy volunteers (n = 12) were studied in 1.

Magnetic resonance imaging of pediatric lung parenchyma, airways, vasculature, ventilation, and perfusion: state of the art.

Magnetic resonance (MR) imaging is a noninvasive imaging modality, particularly attractive for pediatric patients given its lack of ionizing radiation. Despite many advantages, the physical properties of the lung (inherent low signal-to-noise ratio, magnetic susceptibility differences at lung-air interfaces, and respiratory and cardiac motion) have posed technical challenges that have limited the use of MR imaging in the evaluation of thoracic disease in the past. However, recent advances in MR imaging techniques have overcome many of these challenges.

Regional mapping of gas uptake by blood and tissue in the human lung using hyperpolarized xenon-129 MRI.

Purpose: To develop a breathhold acquisition for regional mapping of ventilation and the fractions of hyperpolarized xenon-129 (Xe129) dissolved in tissue (lung parenchyma and plasma) and red blood cells (RBCs), and to perform an exploratory study to characterize data obtained in human subjects.

Materials And Methods: A three-dimensional, multi-echo, radial-trajectory pulse sequence was developed to obtain ventilation (gaseous Xe129), tissue, and RBC images in healthy subjects, smokers, and asthmatics. Signal ratios (total dissolved Xe129 to gas, tissue-to-gas, RBC-to-gas, and RBC-to-tissue) were calculated from the images for quantitative comparison.

32-channel phased-array receive with asymmetric birdcage transmit coil for hyperpolarized xenon-129 lung imaging.

Hyperpolarized xenon-129 has the potential to become a noninvasive contrast agent for lung MRI. In addition to its utility for imaging of ventilated airspaces, the property of xenon to dissolve in lung tissue and blood upon inhalation provides the opportunity to study gas exchange. Implementations of imaging protocols for obtaining regional parameters that exploit the dissolved phase are limited by the available signal-to-noise ratio, excitation homogeneity, and length of acquisition times.

Single-breath xenon polarization transfer contrast (SB-XTC): implementation and initial results in healthy humans.

Purpose: To implement and characterize a single-breath xenon transfer contrast (SB-XTC) method to assess the fractional diffusive gas transport F in the lung: to study the dependence of F and its uniformity as a function of lung volume; to estimate local alveolar surface area per unit gas volume S(A)/V(Gas) from multiple diffusion time measurements of F; to evaluate the reproducibility of the measurements and the necessity of B(1) correction in cases of centric and sequential encoding.

Materials And Methods: In SB-XTC three or four gradient echo images separated by inversion/saturation pulses were collected during a breath-hold in eight healthy volunteers, allowing the mapping of F (thus S(A)/V(Gas)) and correction for other contributions such as T(1) relaxation, RF depletion and B(1) inhomogeneity from inherently registered data.

Results: Regional values of F and its distribution were obtained; both the mean value and heterogeneity of F increased with the decrease of lung volume.

Multiple-exchange-time xenon polarization transfer contrast (MXTC) MRI: initial results in animals and healthy volunteers.

Hyperpolarized xenon-129 is a noninvasive contrast agent for lung MRI, which upon inhalation dissolves in parenchymal structures, thus mirroring the gas-exchange process for oxygen in the lung. Multiple-exchange-time xenon polarization transfer contrast (MXTC) MRI is an implementation of the XTC MRI technique in four dimensions (three spatial dimensions plus exchange time). The aim of this study was to evaluate the sensitivity of MXTC MRI for the detection of microstructural deformations of the healthy lung in response to gravity-induced tissue compression and the degree of lung inflation.

Simultaneous magnetic resonance imaging of ventilation distribution and gas uptake in the human lung using hyperpolarized xenon-129.

Despite a myriad of technical advances in medical imaging, as well as the growing need to address the global impact of pulmonary diseases, such as asthma and chronic obstructive pulmonary disease, on health and quality of life, it remains challenging to obtain in vivo regional depiction and quantification of the most basic physiological functions of the lung-gas delivery to the airspaces and gas uptake by the lung parenchyma and blood-in a manner suitable for routine application in humans. We report a method based on MRI of hyperpolarized xenon-129 that permits simultaneous observation of the 3D distributions of ventilation (gas delivery) and gas uptake, as well as quantification of regional gas uptake based on the associated ventilation. Subjects with lung disease showed variations in gas uptake that differed from those in ventilation in many regions, suggesting that gas uptake as measured by this technique reflects such features as underlying pathological alterations of lung tissue or of local blood flow.

Large production system for hyperpolarized 129Xe for human lung imaging studies.

Rationale And Objectives: Hyperpolarized gases such as (129)Xe and (3)He have high potential as imaging agents for functional lung magnetic resonance imaging (MRI). We present new technology offering (129)Xe production rates with order-of-magnitude improvement over existing systems, to liter per hour at 50% polarization. Human lung imaging studies with xenon, initially limited by the modest quantity and quality of hyperpolarized gas available, can now be performed with multiliter quantities several times daily.

Hyperpolarized (129)Xe MRI: a viable functional lung imaging modality?

The majority of researchers investigating hyperpolarized gas MRI as a candidate functional lung imaging modality have used (3)He as their imaging agent of choice rather than (129)Xe. This preference has been predominantly due to, (3)He providing stronger signals due to higher levels of polarization and higher gyromagnetic ratio, as well as its being easily available to more researchers due to availability of polarizers (USA) or ease of gas transport (Europe). Most researchers agree, however, that hyperpolarized (129)Xe will ultimately emerge as the imaging agent of choice due to its unlimited supply in nature and its falling cost.