Fundamental mechanisms of 3He relaxation on glass

Proc. Natl. Acad. Sci. U.S.A.

Stupic

et al. 2005

For the first time, magnetic resonance imaging (MRI) with hyperpolarized (hp) krypton-83 ( 83 Kr) has become available. The relaxation of the nuclear spin of 83 Kr atoms (I ‫؍‬ 9͞2) is driven by quadrupolar interactions during brief adsorption periods on surrounding material interfaces. Experiments in model systems reveal that the longitudinal relaxation of hp 83 Kr gas strongly depends on the chemical composition of the materials. The relaxationweighted contrast in hp 83 Kr MRI allows for the distinction between hydrophobic and hydrophilic surfaces. The feasibility of hp 83 Kr MRI of airways is tested in canine lung tissue by using krypton gas with natural abundance isotopic distribution. Additionally, the influence of magnetic field strength and the presence of a breathable concentration of molecular oxygen on longitudinal relaxation are investigated.NMR ͉ optical pumping ͉ pulmonary ͉ MRI ͉ xenon H igh nuclear spin polarization in noble gasses can be generated through rubidium vapor spin exchange optical pumping (RbSEOP) (1) and allows for NMR signal enhancements of many orders of magnitude (2). Hyperpolarized (hp) 3 He and hp 129 Xe (both I ϭ 1͞2) have both been used in a wide range of NMR and magnetic resonance imaging (MRI) experiments that are otherwise impossible (3-15). In particular hp 3 He has been applied for medical MRI diagnosis of pulmonary diseases (16)(17)(18)(19). One of the fundamental parameters with high diagnostic value for hp 3 He MRI is the spin-density that is a result of the helium concentration in a particular volume. Spin-density mapping of hp 3 He can be applied to visualize ventilation in lungs. Other useful parameters are 3 He diffusion that provides information about alveolar size distributions in lung tissue and hp 3 He relaxation that depends on oxygen partial pressure in lungs. In vivo MRI of airways with hp 129 Xe as a contrast agent (19-21) suffers from a lower sensitivity compared with hp 3 He. However, 129 Xe adds a further parameter not available by 3 He, namely, the chemical shift that allows for insights into the local environment of the xenon atoms (22-27). The 129 Xe chemical shift has been used extensively for research in materials science, engineering, and xenon dissolved in liquids including human blood (3,5,6,8,9,12,28). The chemical shift obtained from hp 129 Xe can be used to generate an in vivo MRI contrast that is a probe for gas perfusion in lungs (i.e., exchange of the gaseous xenon with the lung parenchyma) (29).3 He and 129 Xe are the only spin I ϭ 1͞2 stable isotopes of the noble gas group, but there are three more NMR active isotopes in this group with higher spin that possess a nuclear electric quadrupole moment. The three quadrupolar isotopes are 21 Ne (I ϭ 3͞2, natural abundance 0.27%), 83 Kr (I ϭ 9͞2, natural abundance 11.5%), and 131 Xe (I ϭ 3͞2, natural abundance 21%). Quadrupolar interactions in these noble gas atoms cause spin relaxation and coherent spin evolution that are probes for the shape, size, and symmetry of void spaces as well as the ...

Section: Batch Mode Hp 83 Kr Mri Of a Desiccated Lungmentioning

confidence: 99%

Hyperpolarized krypton-83 as a contrast agent for magnetic resonance imaging

Pavlovskaya

Proc. Natl. Acad. Sci. U.S.A.

Stupic

et al. 2005

“…According to Jacob et al [24], the relaxivity is expected to depend on the solubility and diffusivity of 129 Xe in the polymer as well as on the strength of dipolar interactions with 1 H or 19 F nuclei in the polymer matrix. Compared to Teflon, which consists of (CF 2 CF 2 ) n chains, the dipolar interaction is expected to be slightly stronger in Tedlar, which consists of (CH 2 CHF) n chains, as the magnetic moment of the proton is slightly larger than that of 19 F. This should lead to an increased relaxivity in Tedlar.…”

Section: Resultsmentioning

confidence: 99%

“…To model

1 / T_{1}^{W}

in a deflating gas reservoir made of polymer material, we adopt a model originally proposed by Jacob et al [24] to describe noble gas relaxation on glass surfaces where dissolution of the gas into the glass is a factor. This model is based on the solubility, diffusion, and intrinsic relaxation of 129 Xe in the polymer.…”

Section: Methodsmentioning

confidence: 99%

Relaxation of hyperpolarized 129Xe in a deflating polymer bag

Möller

Journal of Magnetic Resonance

Driehuys

2011

In magnetic resonance imaging with hyperpolarized (HP) noble gases, data is often acquired during prolonged gas delivery from a storage reservoir. However, little is known about the extent to which relaxation within the reservoir will limit the useful acquisition time. For quantitative characterization, 129Xe relaxation was studied in a bag made of polyvinyl fluoride (Tedlar). Particular emphasis was on wall relaxation, as this mechanism is expected to dominate. The HP 129Xe magnetization dynamics in the deflating bag were accurately described by a model assuming dissolution of Xein the polymer matrix and dipolar relaxation with neighboring nuclear spins. In particular, the wall relaxation rate changed linearly with the surface-to-volume ratio and exhibited a relaxivity of κ = 0.392± 0.008 cm/h, which is in reasonable agreement with κ = 0.331 ± 0.051 cm/h measured in a static Tedlar bag. Estimates for the bulk gas-phase 129Xe relaxation yielded T1bulk=2.55±0.22h, which is dominated by intrinsic Xe-Xe relaxation, with small additional contributions from magnetic field in homogeneities and oxygen-induced relaxation. Calculations based on these findings indicate that relaxation may limit HP 129Xe experiments when slow gas delivery rates are employed as, for example, in mouse imaging or vascular infusion experiments.

“…67 The opposite effect on a much longer timescale has been observed with 129 Xe and 3 He NMR 68,69 because the surface coating insulates the noble gas atoms from paramagnetic sites in the glass surface. 70 In the case of 83 Kr, the separation from paramagnetic sites in the glass surface is outweighed by quadrupolar relaxation on the high affinity, siliconized surface.…”

Section: Probing Surface-to-volume Ratio and Surface Chemistry With Hmentioning

confidence: 99%

Studying porous materials with krypton-83 NMR spectroscopy

Meersmann

2007

Magn. Reson. Chem.

This report is the first review of (83)Kr nuclear magnetic resonance as a new and promising technique for exploring the surfaces of solid materials. In contrast to the spin I = 1/2 nucleus of (129)Xe, (83)Kr has a nuclear spin of I = 9/2 and therefore possesses a nuclear electric quadrupole moment. Interactions of the quadrupole moment with the electronic environment are modulated by surface adsorption processes and therefore affect the (83)Kr relaxation rate and spectral lineshape. These effects are much more sensitive probes for surfaces than the (129)Xe chemical shielding and provide unique insights into macroporous materials in which the (129)Xe chemical shift is typically of little diagnostic value. The first part of this report reviews the effect of quadrupolar interactions on the (83)Kr linewidth in zeolites and also the (83)Kr chemical shift behavior that is distinct from that of its (129)Xe cousin in some of these materials. The second part reviews hyperpolarized (hp) (83)Kr NMR spectroscopy of macroporous materials in which the longitudinal relaxation is typically too slow to allow sufficient averaging of thermally polarized (83)Kr NMR signals. The quadrupolar-driven T(1) relaxation times of hp (83)Kr in these materials are sensitive to surface chemistry, surface-to-volume ratios, coadsorption of other species on surfaces, and surface temperature. Thus, (83)Kr T(1) relaxation can provide information about surfaces and chemical processes in macroscopic pores and can generate surface-sensitive contrast in hp (83)Kr MRI.