Browsing by Author "Nouls, John"

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    Diverse Cardiopulmonary Diseases are Associated with Distinct Xenon MRI Signatures.
    (The European respiratory journal, 2019-10-16) Wang, Ziyi; Bier, Elianna A; Swaminathan, Aparna; Parikh, Kishan; Nouls, John; He, Mu; Mammarappallil, Joseph G; Luo, Sheng; Driehuys, Bastiaan; Rajagopal, Sudarshan
    BACKGROUND:As an increasing number of patients exhibit concomitant cardiac and pulmonary disease, limitations of standard diagnostic criteria are more frequently encountered. Here, we apply noninvasive 129Xenon MR imaging and spectroscopy to identify patterns of regional gas transfer impairment and hemodynamics that are uniquely associated with chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), left heart failure (LHF), and pulmonary arterial hypertension (PAH). METHODS:Healthy volunteers (n=23) and patients with COPD (n=8), IPF (n=12), LHF (n=6), and PAH (n=10) underwent 129Xe gas transfer imaging and dynamic spectroscopy. For each patient, 3D maps were generated to depict ventilation, barrier uptake (129Xe dissolved in interstitial tissue), and red blood cell (RBC) transfer (129Xe dissolved in RBCs). Dynamic 129Xe spectroscopy was used to quantify cardiogenic oscillations in the RBC signal amplitude and frequency shift. RESULTS:Compared to healthy volunteers, all patient groups exhibited decreased ventilation and RBC transfer (p≤0.01, p≤0.01). Patients with COPD demonstrated more ventilation and barrier defects compared to all other groups (p≤0.02, p≤0.02). In contrast, IPF patients demonstrated elevated barrier uptake compared to all other groups (p≤0.007) and increased RBC amplitude and shift oscillations compared to healthy volunteers (p=0.007, p≤0.01). Patients with COPD and PAH both exhibited decreased RBC amplitude oscillations (p=0.02, p=0.005) compared to healthy volunteers. LHF was distinguishable from PAH by enhanced RBC amplitude oscillations (p=0.01). CONCLUSION:COPD, IPF, LHF, and PAH each exhibit unique 129Xe MR imaging and dynamic spectroscopy signatures. These metrics may help with diagnostic challenges in cardiopulmonary disease and increase understanding of regional lung function and hemodynamics at the alveolar-capillary level.
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    Generalized Linear Binning to Compare Hyperpolarized 129Xe Ventilation Maps Derived from 3D Radial Gas Exchange Versus Dedicated Multislice Gradient Echo MRI.
    (Academic radiology, 2019-11-27) He, Mu; Wang, Ziyi; Rankine, Leith; Luo, Sheng; Nouls, John; Virgincar, Rohan; Mammarappallil, Joseph; Driehuys, Bastiaan
    RATIONALE:Hyperpolarized 129Xe ventilation MRI is typically acquired using multislice fast gradient recalled echo (GRE), but interleaved 3D radial 129Xe gas transfer MRI now provides dissolved-phase and ventilation images from a single breath. To investigate whether these ventilation images provide equivalent quantitative metrics, we introduce generalized linear binning analysis. METHODS:This study included 36 patients who had undergone both multislice GRE ventilation and 3D radial gas exchange imaging. Images were then quantified by linear binning to classify voxels into one of four clusters: ventilation defect percentage (VDP), Low-, Medium- or High-ventilation percentage (LVP, MVP, HVP). For 3D radial images, linear binning thresholds were generalized using a Box-Cox rescaled reference histogram. We compared the cluster populations from the two ventilation acquisitions both numerically and spatially. RESULTS:Interacquisition Bland-Altman limits of agreement for the clusters between 3D radial vs GRE were (-7% to 5%) for VDP, (-10% to 14%) for LVP, and (-8% to 8%) for HVP. While binning maps were qualitatively similar between acquisitions, their spatial overlap was modest for VDP (Dice = 0.5 ± 0.2), and relatively poor for LVP (0.3 ± 0.1) and HVP (0.2 ± 0.1). CONCLUSION:Both acquisitions yield reasonably concordant VDP and qualitatively similar maps. However, poor regional agreement (Dice) suggests that the two acquisitions cannot yet be used interchangeably. However, further improvements in 3D radial resolution and reconciliation of bias field correction may well obviate the need for a dedicated ventilation scan in many cases.
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    Hyperpolarized Xe MR imaging of alveolar gas uptake in humans.
    (PLoS One, 2010-08-16) Cleveland, Zackary I; Cofer, Gary P; Metz, Gregory; Beaver, Denise; Nouls, John; Kaushik, S Sivaram; Kraft, Monica; Wolber, Jan; Kelly, Kevin T; McAdams, H Page; Driehuys, Bastiaan
    BACKGROUND: One of the central physiological functions of the lungs is to transfer inhaled gases from the alveoli to pulmonary capillary blood. However, current measures of alveolar gas uptake provide only global information and thus lack the sensitivity and specificity needed to account for regional variations in gas exchange. METHODS AND PRINCIPAL FINDINGS: Here we exploit the solubility, high magnetic resonance (MR) signal intensity, and large chemical shift of hyperpolarized (HP) (129)Xe to probe the regional uptake of alveolar gases by directly imaging HP (129)Xe dissolved in the gas exchange tissues and pulmonary capillary blood of human subjects. The resulting single breath-hold, three-dimensional MR images are optimized using millisecond repetition times and high flip angle radio-frequency pulses, because the dissolved HP (129)Xe magnetization is rapidly replenished by diffusive exchange with alveolar (129)Xe. The dissolved HP (129)Xe MR images display significant, directional heterogeneity, with increased signal intensity observed from the gravity-dependent portions of the lungs. CONCLUSIONS: The features observed in dissolved-phase (129)Xe MR images are consistent with gravity-dependent lung deformation, which produces increased ventilation, reduced alveolar size (i.e., higher surface-to-volume ratios), higher tissue densities, and increased perfusion in the dependent portions of the lungs. Thus, these results suggest that dissolved HP (129)Xe imaging reports on pulmonary function at a fundamental level.