Quantification of regional early stage gas exchange changes using hyperpolarized¹²⁹Xe MRI in a rat model of radiation-induced lung injury

Abstract

Regional RILI can be detected two weeks post-irradiation using HP (129)Xe MRI and analysis of gas exchange curves. This approach correlates well with histology and can potentially be used clinically to assess radiation pneumonitis associated with early RILI to improve radiation therapy outcomes.

Physiological gas exchange mapping of hyperpolarized 129Xe using spiral‐IDEAL and MOXE in a model of regional radiation‐induced lung injury

“…This likely contributed to the observation that measurements of gas transfer time ( T ) and alveolar septal thickness ( d ) were not significantly different between cohorts even though some tissue thickening was observed histologically. This is unexpected since previous studies have reported increased transfer times as well as increased septal thicknesses . However, the manifestation of injury across all studies is likely to be different due to differences in the doses used, incubation periods, and lung volumes irradiated which may be partly responsible for any discrepancies.…”

“…where similar decreases in HCT were observed with whole‐lung spectroscopic gas exchange analysis 3 months after whole‐thorax irradiation. Similarly, Doganay et al . measured reduced relative blood volume in the entire irradiated right lung 2 weeks after hemithoracic irradiation with spiral‐IDEAL using a different gas exchange model.…”

“…This work demonstrates that voxel‐by‐voxel gas exchange mapping of the lung is feasible using spiral‐IDEAL in rats with clinical hardware. Previous work benefitted from dedicated high‐performance animal gradient coils . However, due to hardware limitations (length of readout, spoiling of transverse magnetization, and gradient cool‐down), the fastest that a single pulse‐acquisition could be performed in this study was limited to 34 ms.…”

“…Recently, a technique has been developed combining rapid spiral readout and iterative decomposition of water and fat with echo asymmetry and least squares estimation (IDEAL) chemical shift encoding to overcome these challenges . Regional differences in gas exchange were demonstrated in rats after hemithoracic irradiation (entire right lung) using this spiral‐IDEAL imaging approach, but these changes were observed entirely between the left and right lungs only . A limitation of the previously mentioned studies is that whole and hemithoracic irradiation models may exacerbate injury due to the large volume of tissue irradiated .…”

Magnetic resonance imaging with hyperpolarized agents: methods and applications

“…HP 129 Xe has shown promise with respect to the lung inflammation and fibrotic processes underlying RILI because of its solubility in tissues and blood. For example, several feasibility studies in rat models of RILI have shown increased tissue signal from dissolved phase 129 Xe, suggestive of wall thickening in radiation treated lung tissues vs. control regions [207, 208]. Consistent with this observation, others have used DWI on 129 Xe MRI to detect reduced ADC values in control vs. irradiated rat lungs [209].…”