https://escholarship.org/content/qt16g3d6mk/qt16g3d6mk.pdf

Nuclear magnetic resonance of laser-polarized noble gases in molecules, materials, and organisms.

The nuclear spin polarization of the noble gas isotopes (3)He and (129)Xe can be increased using optical pumping methods by four to five orders of magnitude. This extraordinary gain in polarization translates directly into a gain in signal strength for MRI. The new technology of hyperpolarized (HP) gas MRI holds enormous potential for enhancing sensitivity and contrast in pulmonary imaging. This review outlines the physics underlying the optical pumping process, imaging strategies coping with the nonequilibrium polarization, and effects of the alveolar microstructure on relaxation and diffusion of the noble gases. It presents recent progress in HP gas MRI and applications ranging from MR microscopy of airspaces to imaging pulmonary function in patients and suggests potential directions for future developments.

MRI of the lungs using hyperpolarized noble gases.

Using a new method of xenon laser-polarization that permits the generation of liter quantities of hyperpolarized 129Xe gas, the first 129Xe imaging results from the human chest and the first 129Xe spectroscopy results from the human chest and head have been obtained. With polarization levels of approximately 2%, cross-sectional images of the lung gas-spaces with a voxel volume of 0.9 cm3 (signal-to-noise ratio (SNR), 28) were acquired and three dissolved-phase resonances in spectra from the chest were detected. In spectra from the head, one prominent dissolved-phase resonance, presumably from brain parenchyma, was detected. With anticipated improvements in the 129Xe polarization system, pulse sequences, RF coils, and breathing maneuvers, these results suggest the possibility for 129Xe gas-phase imaging of the lungs with a resolution approaching that of current conventional thoracic proton imaging. Moreover, the results suggest the feasibility of dissolved-phase imaging of both the chest and brain with a resolution similar to that obtained with the gas-phase images.

MR imaging and spectroscopy using hyperpolarized 129Xe gas: preliminary human results.

By permitting direct visualization of the airspaces of the lung, magnetic resonance imaging (MRI) using hyperpolarized gases provides unique strategies for evaluating pulmonary structure and function. Although the vast majority of research in humans has been performed using hyperpolarized (3)He, recent contraction in the supply of (3)He and consequent increases in price have turned attention to the alternative agent, hyperpolarized (129) Xe. Compared to (3)He, (129)Xe yields reduced signal due to its smaller magnetic moment. Nonetheless, taking advantage of advances in gas-polarization technology, recent studies in humans using techniques for measuring ventilation, diffusion, and partial pressure of oxygen have demonstrated results for hyperpolarized (129)Xe comparable to those previously demonstrated using hyperpolarized (3)He. In addition, xenon has the advantage of readily dissolving in lung tissue and blood following inhalation, which makes hyperpolarized (129)Xe particularly attractive for exploring certain characteristics of lung function, such as gas exchange and uptake, which cannot be accessed using (3)He. Preliminary results from methods for imaging (129) Xe dissolved in the human lung suggest that these approaches will provide new opportunities for quantifying relationships among gas delivery, exchange, and transport, and thus show substantial potential to broaden our understanding of lung disease. Finally, recent changes in the commercial landscape of the hyperpolarized-gas field now make it possible for this innovative technology to move beyond the research laboratory.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/jmri.23844

Hyperpolarized 129Xe MRI of the human lung

Lung imaging has traditionally relied on x-ray methods, since proton MRI is limited to some extent by low proton density in the lung parenchyma and static field inhomogeneities in the chest. The relatively recent introduction of MRI of hyperpolarized noble gases has led to a rapidly evolving field of pulmonary MRI, revealing functional information of the lungs, which were hitherto unattainable. This review article briefly describes the physical background of the technology, and subsequently focuses on its clinical applications. Four different techniques that have been used in various human investigations are discussed: ventilation distribution, ventilation dynamics, and small airway evaluation using diffusion imaging and oxygen uptake assessment.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/jmri.20154

Functional MRI of the lung using hyperpolarized 3-helium gas.

Temporal dynamics of hyperpolarized 129Xe resonances in living rats.

A method and system for producing polarized 129Xe gas in an economical manner, allowing the polarized 129Xe gas to be used commercially in research and clinical applications. The production system of the present invention includes a holding tank (12) for holding an unpolarized xenon gas/nitrogen gas mixture. The holding tank (12) is in communication with a temperature controlled polarization chamber (14). A wide spectrum high power light source (22) such as a diode laser array is in communication with the polarization chamber (14). The alkali metal vapor is optically pumped by the light source (22). The polarization chamber (14), which contains a given quantity of an alkali metal and its associated vapor, receives the gaseous mixture from the holding tank (12). The optically pumped alkali metal vapor atoms then collide with the xenon gas atoms, thus polarizing the xenon atoms. The entire gaseous mixture expands out of the polarization chamber (14) into a device (24) that separates the alkali metal vapor atoms from the polarized 129Xe atoms. The polarized 129Xe are then controllably output to a system/user interface (32) for application purposes.

METHOD AND SYSTEM FOR PRODUCING POLARIZED 129Xe GAS

Hyperpolarized 129Xe MR imaging of the oral cavity.

Hyperpolarized 129Xe Lifetimes in Blood

Time reversal and parity non‐invariant interactions within an atom naturally give rise to an atomic permanent electric dipole moment (PEDM) For noble gas atoms, the size of such a PEDM scales as Z2 and higher powers of Z depending on the actual manifestation of T non‐invariance, most importantly a distribution of electric dipole moment within the nucleus (Schiff Moment) and a T‐odd tensor interaction between the nucleus and atomic electrons We have developed techniques to simultaneously measure the PEDMs of 129Xe and 3He in a single cell in order to mitigate systematic effects due to leakage currents and common mode problems such as magnetic field and time base noise The philosophy of our approach is that PEDM of 3He is negligible compared to that of 129Xe and thus we use the 3He as a ‘‘magnetometer’’ and monitor of systematic effects Sensitivity of ≊10−25 e‐cm per day has been demonstrated in preliminary work using a free‐induction decay technique

/pdf/the-search-for-a-permanent-electric-dipole-moment-using-xrkin0ev57.pdf

Eduardo Oteiza

Papers

Temporal dynamics of hyperpolarized 129Xe resonances in living rats.

METHOD AND SYSTEM FOR PRODUCING POLARIZED 129Xe GAS

Hyperpolarized 129Xe MR imaging of the oral cavity.

Hyperpolarized 129Xe Lifetimes in Blood

The Search for a Permanent Electric Dipole Moment using 129Xe and 3He