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Multiple-exchange-time xenon polarization transfer contrast (MXTC) MRI: initial results in animals and healthy
Isabel Dregely1, Iulian C Ruset, Jaime F Mata
1Department of Physics, University of New Hampshire, Durham, NH, USA.
Abstract:
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. 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.
Insights
Multiple-exchange-time xenon polarization transfer contrast (MXTC) MRI detects subtle lung microstructural changes. This advanced lung MRI technique shows sensitivity to gravity-induced deformations and inflation levels in healthy lungs.
Area of Science:
- Pulmonary imaging
- Medical physics
- Cardiovascular and respiratory system imaging
Background:
- Hyperpolarized xenon-129 MRI is a noninvasive tool for visualizing lung structures.
- Xenon polarization transfer contrast (XTC) MRI visualizes gas exchange, but its sensitivity to microstructural changes needs further evaluation.
Purpose of the Study:
- To assess the sensitivity of four-dimensional multiple-exchange-time xenon polarization transfer contrast (MXTC) MRI in detecting microstructural deformations in healthy lungs.
- To evaluate the impact of gravity-induced tissue compression and lung inflation on MXTC MRI parameters.
Main Methods:
- MXTC MRI was performed on four rabbits and three healthy human volunteers.
- Regional lung function parameters, including tissue-to-alveolar-volume ratio and average septal-wall thickness, were determined.
- The study analyzed MXTC MRI parameter gradients in response to varying lung volumes and body positioning.
Main Results:
- A significant gradient in MXTC MRI parameters was observed at low lung volumes, indicating gravity-induced tissue deformation.
- At high lung volumes, MXTC MRI parameters were lower, with a less pronounced gradient.
- The study successfully quantified subtle changes in healthy lung microstructure using MXTC MRI.
Conclusions:
- MXTC MRI is sensitive to microstructural changes in the healthy lung, particularly under conditions of low lung volume and gravitational stress.
- The technique's focus on gas-exchanging structures suggests high potential for detecting lung pathologies affecting gas exchange.
