scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Hyperpolarized 129Xe MRI of the human lung

01 Feb 2013-Journal of Magnetic Resonance Imaging (NIH Public Access)-Vol. 37, Iss: 2, pp 313-331
TL;DR: Preliminary results from methods for imaging 129Xe 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 the understanding of lung disease.
Abstract: 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.
Citations
More filters
Journal ArticleDOI
TL;DR: This comprehensive review describes the state of the art of clinically approved contrast agents, their mechanism of action, and factors influencing their safety and efforts to make safer contrast agents either by increasing relaxivity, increasing resistance to metal ion release, or by moving to gadolinium(III)-free alternatives.
Abstract: Tens of millions of contrast-enhanced magnetic resonance imaging (MRI) exams are performed annually around the world. The contrast agents, which improve diagnostic accuracy, are almost exclusively small, hydrophilic gadolinium(III) based chelates. In recent years concerns have arisen surrounding the long-term safety of these compounds, and this has spurred research into alternatives. There has also been a push to develop new molecularly targeted contrast agents or agents that can sense pathological changes in the local environment. This comprehensive review describes the state of the art of clinically approved contrast agents, their mechanism of action, and factors influencing their safety. From there we describe different mechanisms of generating MR image contrast such as relaxation, chemical exchange saturation transfer, and direct detection and the types of molecules that are effective for these purposes. Next we describe efforts to make safer contrast agents either by increasing relaxivity, increasing resistance to metal ion release, or by moving to gadolinium(III)-free alternatives. Finally we survey approaches to make contrast agents more specific for pathology either by direct biochemical targeting or by the design of responsive or activatable contrast agents.

817 citations

Journal ArticleDOI
TL;DR: The classification system proposed and illustrated in this article provides a structured approach to visual and quantitative assessment of COPD and helps to contribute to a personalized approach to the treatment of patients with COPD.
Abstract: Integration of visual characterization of emphysema and airway abnormalities with physiologic and quantitative CT assessment permits categorization of chronic obstructive pulmonary disease into distinct structurally and functionally defined subtypes.

389 citations

Journal ArticleDOI
TL;DR: This article explores selected advances in methods for the preparation and use of hyperpolarized contrast agents, many of which are already at or near the phase of their clinical validation in patients.
Abstract: Recent developments in NMR hyperpolarization have enabled a wide array of new in vivo molecular imaging modalities, ranging from functional imaging of the lungs to metabolic imaging of cancer. This Concept article explores selected advances in methods for the preparation and use of hyperpolarized contrast agents, many of which are already at or near the phase of their clinical validation in patients.

225 citations

Journal ArticleDOI
TL;DR: This method enables hyperpolarization of molecular sites with NMR T1 relaxation times suitable for biomedical imaging and spectroscopy and provides large enough signal gains to enable one of the first 15N images (2 × 2 mm2 resolution).
Abstract: NMR signal amplification by reversible exchange (SABRE) is a NMR hyperpolarization technique that enables nuclear spin polarization enhancement of molecules via concurrent chemical exchange of a target substrate and parahydrogen (the source of spin order) on an iridium catalyst. Recently, we demonstrated that conducting SABRE in microtesla fields provided by a magnetic shield enables up to 10% 15N-polarization (Theis, T.; et al. J. Am. Chem. Soc. 2015, 137, 1404). Hyperpolarization on 15N (and heteronuclei in general) may be advantageous because of the long-lived nature of the hyperpolarization on 15N relative to the short-lived hyperpolarization of protons conventionally hyperpolarized by SABRE, in addition to wider chemical shift dispersion and absence of background signal. Here we show that these unprecedented polarization levels enable 15N magnetic resonance imaging. We also present a theoretical model for the hyperpolarization transfer to heteronuclei, and detail key parameters that should be optimiz...

176 citations

Journal ArticleDOI
TL;DR: This Minireview covers the fundamentals of the preparation of hyperpolarized gases and focuses on selected applications of interest to biomedicine and materials science.
Abstract: Nuclear spin polarization can be significantly increased through the process of hyperpolarization, leading to an increase in the sensitivity of nuclear magnetic resonance (NMR) experiments by 4-8 orders of magnitude. Hyperpolarized gases, unlike liquids and solids, can be more readily separated and purified from the compounds used to mediate the hyperpolarization processes. These pure hyperpolarized gases enabled many novel MRI applications including the visualization of void spaces, imaging of lung function, and remote detection. Additionally, hyperpolarized gases can be dissolved in liquids and can be used as sensitive molecular probes and reporters. This mini-review covers the fundamentals of the preparation of hyperpolarized gases and focuses on selected applications of interest to biomedicine and materials science.

138 citations

References
More filters
Journal ArticleDOI
21 Jul 1994-Nature
TL;DR: It is shown that 129Xe gas can be used for high-resolution MRI when the nuclear-spin polarization of the atoms is increased by laser optical pumping and spin exchange, which produces hyperpolarized 129xe, in which the magnetization is enhanced by a factor of about 105.
Abstract: As currently implemented, magnetic resonance imaging (MRI) relies on the protons of water molecules in tissue to provide the NMR signal. Protons are, however, notoriously difficult to image in some biological environments of interest, notably the lungs and lipid bilayer membranes such as those in the brain. Here we show that 129Xe gas can be used for high-resolution MRI when the nuclear-spin polarization of the atoms is increased by laser optical pumping and spin exchange. This process produces hyperpolarized 129Xe, in which the magnetization is enhanced by a factor of about 10(5). By introducing hyperpolarized 129Xe into mouse lungs we have obtained images of the lung gas space with a speed and a resolution better than those available from proton MRI or emission tomography. As xenon (a safe general anaesthetic) is rapidly and safely transferred from the lungs to blood and thence to other tissues, where it is concentrated in lipid and protein components, images of the circulatory system, the brain and other vital organs can also be obtained. Because the magnetic behaviour of 129Xe is very sensitive to its environment, and is different from that of 1H2O, MRI using hyperpolarized 129Xe should involve distinct and sensitive mechanisms for tissue contrast.

1,017 citations


"Hyperpolarized 129Xe MRI of the hum..." refers methods in this paper

  • ...Although the first hyperpolarized-gas MR images were obtained using hyperpolarized (129)Xe (11), and images of the human lung were acquired with hyperpolarized (129)Xe only a few years later (12), the vast majority of work in humans has been performed using hyperpolarized (3)He instead....

    [...]

Journal ArticleDOI
TL;DR: The intrinsic and system SNR is applied to predict image SNR and has found satisfactory agreement with measurements on images, which indicates that the initial choice of pixel size is crucial in NMR.
Abstract: The fundamental limit for NMR imaging is set by an intrinsic signal-to-noise ratio (SNR) for a particular combination of rf antenna and imaging subjects. The intrinsic SNR is the signal from a small volume of material in the sample competing with electrical noise from thermally generated, random noise currents in the sample. The intrinsic SNR has been measured for a number of antenna-body section combinations at several different values of the static magnetic field and is proportional to B0. We have applied the intrinsic and system SNR to predict image SNR and have found satisfactory agreement with measurements on images. The relationship between SNR and pixel size is quite different in NMR than it is with imaging modalities using ionizing radiation, and indicates that the initial choice of pixel size is crucial in NMR. The analog of "contrast-detail-dose" plots for ionizing radiation imaging modalities is the "contrast-detail-time" plot in NMR, which should prove useful in choosing a suitable pixel array to visualize a particular anatomical detail for a given NMR receiving antenna.

760 citations

Journal ArticleDOI
TL;DR: The theory of spin exchange between optically pumped alkali-inetal atoms and noble-gas nuclei is presented in this article, where the main spin interactions are assumed to be the spin-rotation interactions yN S between the rotational angular momentum N of the alkali ion and the electron spin S of the noble ion.
Abstract: The theory of spin exchange between optically pumped alkali-Inetal atoms and noble-gas nuclei is presented. Spin exchange with heavy noble gases is dominated by interactions in long-lived van der Waals molecules. The main spin interactions are assumed to be the spin-rotation interactions yN S between the rotational angular momentum N of the alkali-metal — noble-gas pair and the electron spin S of the alkali-metal atom, and the contact hyperfine interaction aK S between the nuclear spin K of the noble-gas atom and the electron spin S. Arbitrary values for EC and for the nuclear spin I of the alkali-metal atom are assumed. Precise formal expressions for spin transfer coefficients are given along with convenient approximations based on a perturbation expansion in powers of (o.'/yX), a quantity which has been shown to be small by experiment.

404 citations


"Hyperpolarized 129Xe MRI of the hum..." refers background in this paper

  • ...In the second step of OPSE, collisions between spin-polarized rubidium atoms and noble-gas (129Xe or 3He) atoms within the cell result in spin exchange—the transfer of polarization from rubidium electrons to noble-gas nuclei (Fig....

    [...]

  • ...Nonetheless, the nuclear polarization can be increased dramatically compared to that produced by the magnet of the MR scanner by using a method called optical pumping and spin exchange (OPSE) (9,38), which was originally developed for nuclear-physics experiments many years before being applied to medical imaging....

    [...]

  • ...While the basic OPSE process described above is effective for generating high polarization in a ‘‘batch’’ of pressurized 3He over a period of several hours, the situation is somewhat more complicated for 129Xe....

    [...]

  • ...As its name implies, OPSE is, in concept, a twostep process....

    [...]

  • ...cal pumping and spin exchange (OPSE) (9,38), which was originally developed for nuclear-physics experi-...

    [...]

Journal ArticleDOI
TL;DR: 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 are outlined.
Abstract: 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.

398 citations

Journal ArticleDOI
TL;DR: Various unique features associated with performing MRI with hyperpolarized gases, such as the selection of the noble gas species, polarization technique, and constraints on the MR pulse sequence are discussed.
Abstract: Magnetic resonance images of the lungs of a guinea pig have been produced using hyperpolarized helium as the source of the MR signal. The resulting images are not yet sufficiently optimized to reveal fine structural detail within the lung, but the spectacular signal from this normally signal-deficient organ system offers great promise for eventual in vivo imaging experiments. Fast 2D and 3D GRASS sequences with very small flip angles were employed to conserve the norenewable longitudinal magnetization. We discuss various unique features associated with performing MRI with hyperpolarized gases, such as the selection of the noble gas species, polarization technique, and constraints on the MR pulse sequence.

370 citations