G. Miller, Gordon Cates Jr., David Keder, Talissa Altes, Jaime Mata, Kun Qing, Iulian Ruset, F. Hersman, John Mugler III

The increase in available dissolved-phase signal made possible by high-performing Xe-129 polarizers has led to renewed interest in dissolved-phase imaging of Xe-129 outside the lung. Here we examine the time course of the dissolved phase Xe-129 signal in the human kidney following gas inhalation, in order to optimize kidney image acquisition and explore the potential for studying kidney function using hyperpolarized Xe-129.  In addition to spectral peaks commonly associated with Xe-129 dissolved in tissue/plasma, red blood cells, and fat, we have identified an additional peak at 201 ppm that lags the blood peaks by a few seconds.

David Mummy, Stanley Kruger, Michael Evans, Wei Zha, Ronald Sorkness, Nizar Jarjour, Mark Schiebler, Loren Denlinger, Sean Fain

We assessed the ventilation defect percent (VDP) on hyperpolarized helium-3 MRI as an indicator of severe clinical outcomes (emergency department [ED] visits and hospitalizations as surrogates for significant asthma exacerbations). We compared VDP with conventional biomarkers of lung function and inflammation and found VDP was more strongly associated with both ED and hospitalizations as outcomes. VDP was correlated with spirometry, air trapping measured on CT, and eosinophil levels in sputum and peripheral blood. These findings suggest that VDP is a candidate biomarker associated with clinical outcomes of asthma exacerbation and stability.

Brandon Zanette, Elaine Stirrat, Salomeh Jelveh, Andrew Hope, Giles Santyr

Dissolved ¹²⁹Xe imaging holds promise for the detection of early functional decline due to radiation-induced lung injury through the extraction of regional quantitative parameters relating to lung physiology and gas exchange. In this work a spiral-IDEAL imaging technique was used with a partial-lung irradiation rat model to investigate regional changes lung function associated with injury and compare to histology. A significant reduction in capillary hematocrit (HCT) was observed in the vicinity of irradiation. These results were in agreement with quantitative histology of red blood cells. Imaging results were more sensitive than whole-lung spectroscopy, which was performed simultaneously.

Laura Walkup, Robert Thomen, Emily Bell, Beth Decker, Zackary Cleveland, John Clancy, Jason Woods

Quantitative hyperpolarized ¹²⁹Xe ventilation MRI was compared to FEV₁, the spriometric gold standard for assessing lung function, and lung clearance index (LCI), an emerging pulmonary function test to assess global ventilation heterogeneity, in 12 pediatric cystic fibrosis subjects. A range of severity and spatial distributions of ¹²⁹Xe ventilation deficits were observed, with a ¹²⁹Xe ventilation defect percentage (VDP) of 18.0% ± 8.1%. VDP did not correlate with FEV₁ (p=0.45) but correlated very strongly with LCI (p=0.0001), suggesting that the spatial distribution of defects in the ¹²⁹Xe images represents obstructed areas of the lung that give rise to elevated LCI.

Paul Hughes, Bilal Tahir, Felix Horn, Alberto Biancardi, Rob Ireland, Helen Marshall, Jim Wild

Analysis of the matching of ventilation and perfusion using MRI is an important area of research in the pulmonary MRI community. This work presents a quantitative method of voxelwise analysis of ventilation from hyperpolarized gas MRI and perfusion from dynamic contrast enhanced ¹H MRI. The method developed allows for direct comparison of ventilation and perfusion including global measurements of ventilated and perfused volume.

Grzegorz Bauman, Orso Pusterla, Francesco Santini, Oliver Bieri

This study demonstrates the feasibility of fast and simultaneous T1 and T2 mapping of the lung parenchyma in oxygen-enhanced MRI. The data acquisition was performed using an adapted 2D inversion recovery ultra-fast steady-state free precession imaging in healthy human subjects. Relaxation time maps were generated for normoxic and hyperoxic acquisitions. Statistical analysis was performed to compare the relaxation times in the lung parenchyma for both gas conditions.

Robert Thomen, Laura Walkup, David Roach, Zackary Cleveland, John Clancy, Jason Woods

We have quantified the extent of ventilation impairment in lungs due to specific pathologies associated with cystic fibrosis (CF) lung disease using ultrashort echo-time (UTE) MRI to identify structural abnormalities and hyperpolarized (HP) ¹²⁹Xe MRI to identify ventilation deficits. We found that bronchiectasis demonstrates the best correlation with lung function decline, as measured by the percent predicted forced expiratory volume in 1 second (FEV₁% predicted) and demonstrated the greatest deficit in HP ¹²⁹Xe signal within corresponding defective regions. However, the greatest volume-percentage of defects identified were due to mucus plugging.

Marta Tibiletti, Volker Rasche

Fluorinated gases are a promising alternative to hyperpolarized gases to study ventilation in clinical and preclinical applications. 3D Ultra Short Echo Time (UTE) acquisitions can be employed to visualize inhaled SF6 and lung parenchyma. DC self-gating was applied to discriminate between inspiration and expiration in free-breathing acquisitions. Proton and gas density were estimated in inspiration, expiration and in ungated data. The information derived from tissue-density changes matched the changes observed in the gas density, thus indicating the ventilation information can be derived from tissue density mapping.

Rachel Eddy, Dante Capaldi, Khadija Sheikh, Sarah Svenningsen, David McCormack, Grace Parraga

Pulmonary MRI provides strong evidence of ventilation abnormalities that are temporally and spatially persistent; this has generated a paradigm shift in our understanding of asthma as a spatially and temporally heterogeneous, non-stochastic disease.  Based on these findings, here our objective was to develop image-processing methods to estimate and mathematically describe the spatial probability distribution of MRI-derived ventilation defects. To accomplish this, we generated functional lung MRI atlases based on asthmatics who were evaluated before and post-methacholine using hyperpolarized ³He static-ventilation MRI. This proof-of-concept evaluation showed that in asthmatics, ventilation abnormalities are not diffuse nor stochastic, but heterogeneous and deterministic. 

Andrew Hahn, Nara Higano, Jean Tkach, Laura Walkup, Robert Thomen, Xuefeng Cao, Stephanie Merhar, Jason Woods, Sean Fain

The majority of patients in the neonatal intensive care unit (NICU) have pulmonary morbidities, yet little is known about the underlying parenchymal structure.  We quantify parenchymal proton density and R₂^* in the lungs of quiet breathing, non-sedated neonates in the NICU using a multi-echo 3D radial UTE MRI.  Results indicate that lung proton density decreases as expected with lung inflation, while R₂^* increases.  A positive relationship between gravitational dependence and tissue density is also apparent, while R₂^* decreases in more gravitationally dependent regions.  Overall, our findings support a negative relationship between tissue density and R₂^* in the neonatal lung.