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Hyperpolarized (HP) 129Xe MRI uniquely images pulmonary ventilation, gas exchange, and terminal airway morphology rapidly and safely, providing novel information not possible using conventional imaging modalities or pulmonary function tests. As such, there is mounting interest in expanding the use of biomarkers derived from HP 129Xe MRI as outcome measures in multi‐site clinical trials across a range of pulmonary disorders. Until recently, HP 129Xe MRI techniques have been developed largely independently at a limited number of academic centers, without harmonizing acquisition strategies. To promote uniformity and adoption of HP 129Xe MRI more widely in translational research, multi‐site trials, and ultimately clinical practice, this position paper from the 129Xe MRI Clinical Trials Consortium (https://cpir.cchmc.org/XeMRICTC) recommends standard protocols to harmonize methods for image acquisition in HP 129Xe MRI. Recommendations are described for the most common HP gas MRI techniques—calibration, ventilation, alveolar‐airspace size, and gas exchange—across MRI scanner manufacturers most used for this application. Moreover, recommendations are described for 129Xe dose volumes and breath‐hold standardization to further foster consistency of imaging studies. The intention is that sites with HP 129Xe MRI capabilities can readily implement these methods to obtain consistent high‐quality images that provide regional insight into lung structure and function. While this document represents consensus at a snapshot in time, a roadmap for technical developments is provided that will further increase image quality and efficiency. These standardized dosing and imaging protocols will facilitate the wider adoption of HP 129Xe MRI for multi‐site pulmonary research.

BACKGROUND AND PURPOSE: Dynamic contrast-enhanced MR imaging parameters can be biased by poor measurement of the vascular input function. We have compared the diagnostic accuracy of dynamic contrast-enhanced MR imaging by using a phase-derived vascular input function and "bookend" T1 measurements with DSC MR imaging for preoperative grading of astrocytomas.

Purpose: To map physiological gas exchange parameters using dissolved hyperpolarized (HP) 129 Xe in a rat model of regional radiation-induced lung injury (RILI) with spiral-IDEAL and the model of xenon exchange (MOXE). Results are compared to quantitative histology of pulmonary tissue and red blood cell (RBC) distribution. Methods: Two cohorts (n = 6 each) of age-matched rats were used. One was irradiated in the rightmedial lung, producing regional injury. Gas exchange was mapped 4 weeks postirradiation by imaging dissolved-phase HP 129 Xe using spiral-IDEAL at five gas exchange timepoints using a clinical 1.5 T scanner. Physiological lung parameters were extracted regionally on a voxel-wise basis using MOXE. Mean gas exchange parameters, specifically air-capillary barrier thickness (d) and hematocrit (HCT) in the right-medial lung were compared to the contralateral lung as well as nonirradiated control animals. Whole-lung spectroscopic analysis of gas exchange was also performed. Results: d was significantly increased (1.43 AE 0.12 lm from 1.07 AE 0.09 lm) and HCT was significantly decreased (17.2 AE 1.2% from 23.6 AE 1.9%) in the right-medial lung (i.e., irradiated region) compared to the contralateral lung of the irradiated rats. These changes were not observed in healthy controls. d and HCT correlated with histologically measured increases in pulmonary tissue heterogeneity (r = 0.77) and decreases in RBC distribution (r = 0.91), respectively. No changes were observed using whole-lung analysis. Conclusion: This work demonstrates the feasibility of mapping gas exchange using HP 129 Xe in an animal model of RILI 4 weeks postirradiation. Spatially resolved gas exchange mapping is sensitive to regional injury between cohorts that was undetected with whole-lung gas exchange analysis, in agreement with histology. Gas exchange mapping holds promise for assessing regional lung function in RILI and other pulmonary diseases.

PurposeThe purpose of this work was to use magnetic resonance imaging (MRI) of hyperpolarized (HP) 129Xe dissolved in pulmonary tissue (PT) and red blood cells (RBCs) to detect regional changes to PT structure and perfusion in a partial-lung rat model of radiation-induced lung injury and compare with histology.Methods and materialsThe right medial region of the lungs of 6 Sprague-Dawley rats was irradiated (20 Gy, single-fraction). A second nonirradiated cohort served as the control group. Imaging was performed 4 weeks after irradiation to quantify intensity and heterogeneity of PT and RBC 129Xe signals. Imaging findings were correlated with measures of PT and RBC distribution.ResultsAsymmetric (right vs left) changes in 129Xe signal intensity and heterogeneity were observed in the irradiated cohort but were not seen in the control group. PT signal was observed to increase in intensity and heterogeneity and RBC signal was observed to increase in heterogeneity in the irradiated right lungs, consistent with histology.ConclusionRegional changes to PT and RBC 129Xe signals are detectable 4 weeks following partial-lung irradiation in rats.

Purpose:To demonstrate the feasibility of mapping gas exchange with single breathhold hyperpolarized (HP) 129 Xe in humans, acquiring parametric maps of lung physiology. The potential benefit of acceleration using parallel imaging for this application is also explored. Methods: Six healthy volunteers were scanned with a modified spiral-IDEAL sequence to acquire gas exchange-weighted images using a single dose of 129 Xe.These images were fit with the model of xenon exchange (MOXE) on a voxel-wise basis calculating parametric maps of lung physiology, specifically: air-capillary barrier thickness (δ), alveolar septal thickness (d), capillary transit time (t x ), pulmonary hematocrit (HCT), and alveolar surface area-to-volume ratio (SVR). An accelerated version of the sequence was also tested in subset of 4 volunteers and compared to the fully sampled (FS) results. Results: Mean image-wide values calculated from MOXE parametric maps derived from FS dissolved 129 Xe spiral-IDEAL images were: δ = 0.89 ± 0.17 μm, d = 7.5 ± 0.5 μm, t x = 1.1 ± 0.2s, HCT = 28.8 ± 2.3%, and SVR = 140 ± 16 cm −1 , in good agreement with previously published values based on whole-lung spectroscopy of healthy human subjects.

BACKGROUND AND PURPOSE:Tumor CBV is a prognostic and predictive marker for patients with gliomas. Tumor CBV can be measured noninvasively with different MR imaging techniques; however, it is not clear which of these techniques most closely reflects histologicallymeasured tumor CBV. Our aim was to investigate the correlations between dynamic contrast-enhanced and DSC-MR imaging parameters and immunohistochemistry in patients with gliomas.

Representative Rvent, FVLcc, and QN maps overlaid on the registered GRE image (grayscale) for participant 11 (top) and participant 07 (bottom). Yellow arrows highlight regions of low FVLcc and QN in the left lung. RVent = regional ventilation; FVLcc = flow volume loop cross correlation; QN = normalized perfusion. by Brandon Zanette et al. (1696–1707)