Multiple‐exchange‐time xenon polarization transfer contrast (MXTC) MRI: Initial results in animals and healthy volunteers

Abstract

Hyperpolarized xenon-129 is a non-invasive 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 (3 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. MXTC MRI was performed in four rabbits and in three healthy human volunteers. Two lung function parameters, one related to tissue- to alveolar-volume ratio and the other to average septal-wall thickness, were determined regionally. A significant gradient in MXTC MRI parameters, consistent with gravity-induced lung tissue deformation in the supine imaging position, was found at low lung volumes. At high lung volumes, parameters were generally lower and the gradient in parameter values was less pronounced. Results show that MXTC MRI permits the quantification of subtle changes in healthy lung microstructure. Further, only structures participating in gas exchange are represented in MXTC MRI data, which potentially makes the technique especially sensitive to pathological changes in lung microstructure affecting gas exchange.

Stem Cells and Cell Therapies in Lung Biology and Diseases: Conference Report

“…Hyperpolarized magnetic resonance imaging with 3He or 129Xe works by measuring the random atomic motion (diffusion) of the gas molecules (64,65). Because airway structures will limit the diffusion of gas, measurement of the atomic motion will provide information about the lung microstructure.…”

“…Because airway structures will limit the diffusion of gas, measurement of the atomic motion will provide information about the lung microstructure. Both gases have been used in humans, large animals, and, more recently, small animals in both healthy and diseased conditions and have provided important insights into the three-dimensional structure of the lungs (64)(65)(66)(67)(68)(69)(70)(71)(72)(73). The usefulness of this approach to treatment of human disease is obvious, with greater ability to determine the changes in lung microstructure as a function of disease and over time.…”

Probing lung microstructure with hyperpolarized noble gas diffusion MRI: theoretical models and experimental results

“…The local oxygen concentration and its decrease during breath‐hold have been determined from the 3 He T 1 , allowing the local ventilation–perfusion ratio to be calculated . 129 Xe gas exchange processes between gas and tissue‐dissolved phases have also been studied . Various improvements and new techniques of hyperpolarized gas MRI in lung imaging have been developed over the years (see, for example, review articles and references therein).…”

Front Cover: Simulating Non‐linear Chemical and Physical (CAP) Dynamics of Signal Amplification By Reversible Exchange (SABRE) (Chem. Eur. J. 32/2019)

“…This equilibrium follows from Equations (6) and (7). This equilibrium follows from Equations (6) and (7).…”

“…The hyperpolarization (HP) of nuclear spins promises to revolutionize medical diagnostics [1][2][3][4][5][6][7][8][9][10] and chemical analysis [11][12][13][14][15] alike. Amongo thers, signal amplification by reversible exchange (SABRE), discovered in 2008, [16] is an up-and-coming technique with unique properties,i ncluding continuous hyperpolarization.…”