Hyperpolarized gas MRI in pulmonology

Abstract

Lung diseases have a high prevalence amongst the world population and their early diagnosis has been pointed out to be key for successful treatment. However, there is still a lack of non-invasive examination methods with sensitivity to early, local deterioration of lung function. Proton-based lung MRI is particularly challenging due to short T times and low proton density within the lung tissue. Hyperpolarized gas MRI is aan emerging technology providing a richness of methodologies which overcome the aforementioned problems. Unlike proton-based MRI, lung MRI of hyperpolarized gases may rely on imaging of spins in the lung's gas spaces or inside the lung tissue and thereby add substantial value and diagnostic potential to lung MRI. This review article gives an introduction to the MR physics of hyperpolarized media and presents the current state of hyperpolarized gas MRI of Headvasd andXe in pulmonology. Key applications, ranging from static and dynamic ventilation imaging as well as oxygen-pressure mapping to Xe dissolved-phase imaging and spectroscopy are presented. Hyperpolarized gas MRI is compared to alternative examination methods based on MRI and future directions of hyperpolarized gas MRI are discussed.

Regional investigation of lung function and microstructure parameters by localized 129Xe chemical shift saturation recovery and dissolved‐phase imaging: A reproducibility study

“…Over the last 2 decades, hyperpolarized 129 Xe magnetic resonance imaging and spectroscopy have become valuable tools for the assessment of lung function and lung microstructure, because of the good solubility of 129 Xe in bodily fluids and tissue and because of its large range of chemical shifts . By measuring the gas‐uptake dynamics in the lung, the chemical shift saturation recovery (CSSR) hyperpolarized 129 Xe MR spectroscopy sequence in combination with an analytical model for gas uptake provides a means for characterizing lung microstructure and diffusion capacity .…”

Mapping of regional lung microstructural parameters using hyperpolarized 129Xe dissolved‐phase MRI in healthy volunteers and patients with chronic obstructive pulmonary disease

“…Hyperpolarized 129 Xe MRI is a promising tool both for research and clinical applications that can fill the aforementioned gaps. 5 Imaging of the gas distribution after inhalation of hyperpolarized 129 Xe provides a highly sensitive and reproducible technique for the assessment of local airflow obstruction. 6,7 Beyond that, upon inhalation by a subject, xenon dissolves in the lung tissue and blood, which affects its Larmor frequency due to chemical shift.…”

T1, T1 contrast, and Ernst‐angle images of four rat‐lung pathologies

“…There have been substantial advances in functional pulmonary MRI in the last few decades from imaging gases dominated by polarized noble gases and from tissue MRI, notably from the effect of breathing pure oxygen on the tissue T 1 . The present study is anatomical in comparison.…”

“…To be certain we are not missing signal, we have used free induction decay (FID)-projection imaging (as in 11,[20][21][22] dubbed ZTE, for "zero echo time" 23 ) with acquisition times appropriate for the T * 2 calculated from the 8 ppm line width. 21 There have been substantial advances in functional pulmonary MRI in the last few decades from imaging gases 24 dominated by polarized noble gases [25][26][27][28][29][30][31] and from tissue MRI, notably from the effect of breathing pure oxygen on the tissue T 1 . [32][33][34][35][36][37][38][39][40] The present study is anatomical in comparison.…”