Hyperpolarized Xenon‐129 gas‐exchange imaging of lung microstructure: First case studies in subjects with obstructive lung disease

Abstract

Purpose: To develop and test a method to noninvasively assess the functional lung microstructure. Materials and Methods: The Multiple exchange time Xenon polarization Transfer Contrast technique (MXTC) encodes xenon gas‐exchange contrast at multiple delay times permitting two lung‐function parameters to be derived: (i) MXTC‐F, the long exchange‐time depolarization value, which is proportional to the tissue to alveolar‐volume ratio and (ii) MXTC‐S, the square root of the xenon exchange‐time constant, which characterizes thickness and composition of alveolar septa. Three healthy volunteers, one asthmatic, and two chronic obstructive pulmonary disease (COPD) (GOLD stage I and II) subjects were imaged with MXTC MRI. In a subset of subjects, hyperpolarized xenon‐129 ADC MRI and CT imaging were also performed. Results: The MXTC‐S parameter was found to be elevated in subjects with lung disease (P‐value = 0.018). In the MXTC‐F parameter map it was feasible to identify regional loss of functional tissue in a COPD patient. MXTC‐F maps showed excellent regional correlation with CT and ADC (P ≥ 0.90) in one COPD subject. Conclusion: The functional tissue‐density parameter MXTC‐F showed regional agreement with other imaging techniques. The newly developed parameter MXTC‐S, which characterizes the functional thickness of alveolar septa, has potential as a novel biomarker for regional parenchymal inflammation or thickening. J. Magn. Reson. Imaging 2011;33:1052–1062. © 2011 Wiley‐Liss, Inc.

Cluster formation restricts dynamic nuclear polarization of xenon in solid mixtures

“…3,4 Unlike optical pumping techniques, 5,6 DNP is performed in the solid state, with 1000 times higher 129 Xe density and, potentially, higher production rates. 129 Xe DNP builds upon the earlier success of low-temperature DNP of 13 C-labelled biomolecules, where high 13 C polarization (15%−75%) 7 is retained at room temperature after a rapid dissolution.…”

“…After a number of modifications to the DNP system with an aim of reducing sample overheating, our subsequent experiment showed a four-fold increase in 129 Xe polarization, from 5.3% to 21%. 4 He variable-temperature insert could be cooled down to below 1.3 K for about an hour (or kept indefinitely at 1.43 K and above) using an external pump while being monitored with an Oxford Instruments ITC-503 controller. A computer-controlled primary microwave source (7-8 GHz range and 18.3 dBm power, Hewlett-Packard 83623B or Giga-tronics SNY-0410-510-01) fed via a short coaxial cable into a probe-mounted ×18 frequency multiplier/narrow-band 140 GHz, 70 mW microwave amplifier (ELVA DCOIMA-06/140/70).…”

Robust solidXe129longitudinal relaxation times

“…(The recently developed "open source" polarizer is a notable exception [8].) A cold trap using liquid nitrogen (LN 2 ) is typically used both to separate xenon from the other gases in the mixture that are needed to optimize spin-exchange optical pumping (SEOP) and to provide a compact storage vessel with a polarization lifetime T 1 ≈ 2.5 h. A detailed understanding of 129 Xe longitudinal relaxation in solid xenon is thus important for its use in a wide variety of fundamental studies and applications [9][10][11], including magnetic resonance imaging of the lung [12][13][14][15]. More generally, noble-gas solids are excellent model systems for first-principles calculation of nuclear relaxation mechanisms and rates.…”

Using Raman Spectroscopy to Improve Hyperpolarized Noble Gas Production for Clinical Lung Imaging Techniques

“…Recent hyperpolarization methods can create near-unity net spin polarizations [13], resulting in spectroscopic signals four to five orders of magnitude greater than nonhyperpolarized samples. Such improvements in image quality facilitate the use of HP noble gas MRI within the lungs as a diagnostic imaging tool for characterizing lung structure and function [14], and consequently may potentially enable earlier and more reliable diagnosis of various respiratory disorders, such as idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD) 7]. An example of a HP 129 Xe lung ventilation image can be seen in Figure 2.…”