Effects of pulmonary inhalation on hyperpolarized krypton-83 magnetic resonanceT₁relaxation

Abstract

The 83Kr magnetic resonance (MR) relaxation time T1 of krypton gas in contact with model surfaces was previously found to be highly sensitive to surface composition, surface to volume ratio, and surface temperature. The current work explored aspects of pulmonary 83Kr T1 relaxation measurements in excised lungs from healthy rats using hyperpolarized (hp) 83Kr with approximately 4.4 % spin polarization. MR spectroscopy without spatial resolution was applied to the ex vivo lungs that actively inhale hp 83Kr through a custom designed ventilation system. Various inhalation schemes were devised to explore the influence of anatomical dead space upon the measured 83Kr T1 relaxation times. The longitudinal 83Kr relaxation times in the distal airways and the respiratory zones were independent of the lung inhalation volume, with T1 = 1.3 s and T1 = 1.0 s, depending only on the applied inhalation scheme. The obtained data was highly reproducible between different specimens. Further, the 83Kr T1 relaxation times in excised lungs were unaffected by the presence of up to 40% oxygen in the hp gas mixture. The results support the possible importance of 83Kr as a biomarker for evaluating lung function.

Pathway to Cryogen Free Production of Hyperpolarized Krypton-83 and Xenon-129

“…Hp 129 Xe provides additional information due to its chemical shift and tissue solubility [11] and its attractiveness is further augmented by the limited availability of the 3 He isotope [12], [13]. The isotope 83 Kr possesses a nuclear electric quadrupole moment (eQ) that may enable hp 83 Kr to be used as a surface sensitive contrast agent and biomarker [14], [15].…”

Perspectives of hyperpolarized noble gas MRI beyond 3He

“…As a consequence of its extremely low gyromagnetic ratio, the 83 Kr T 2 relaxation times are typically much longer than that of 129 Xe. Furthermore, due to its low γ , the 83 Kr T 1 relaxation in rat lungs is not affected by the presence of up to 40% paramagnetic oxygen [122]. Note that although hp 83 Kr may dissolve in many tissues, the useful signal associated with its dissolved phase is lost owing to fast quadrupolar relaxation.…”

“…12 provides an example of surface sensitive contrast in hp 83 Kr gas phase MRI. Hp 83 Kr NMR relaxation measurements of excised but actively ventilating rat lungs have been used recently to study T 1 relaxation as a function of lung inflation [122]. The longitudinal 83 Kr relaxation in the distal airways and the respiratory zones was found to be independent of the lung inhalation volume and highly reproducible between different specimens.…”

6‐Hydroxybenzothiophene Ketones: Potent Inhibitors of 17β‐Hydroxysteroid Dehydrogenase Type 1 (17β‐HSD1) Owing to Favorable Molecule Geometry and Conformational Preorganization

“…The hp gas mixture was then delivered under continuous flow SEOP conditions for 45 s at 40 mL min −1 into the relaxation agent containing solution. After flow stoppage, the dissolved phase hp 129 Xe T 1 relaxation was measured through a sequence of 16 constant flip angle (12°) experiments 22. A standard inversion recovery sequence was used to obtain the 1 H T 1 relaxation of H 2 O.…”