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Pennati F.,Polytechnic of Milan | Quirk J.D.,University of Washington | Yablonskiy D.A.,University of Washington | Castro M.,University of Washington | And 3 more authors.
Radiology | Year: 2014

Purpose: To introduce a method based on multivolume proton (hydrogen [1H]) magnetic resonance (MR) imaging for the regional assessment of lung ventilatory function, investigating its use in healthy volunteers and patients with obstructive lung disease and comparing the outcome with the outcome of the research standard helium 3 (3He) MR imaging.Materials and Methods: The institutional review board approved the HIPAA-compliant protocol, and informed written consent was obtained from each subject. Twenty-six subjects, including healthy volunteers (n = 6) and patients with severe asthma (n = 11) and mild (n = 6) and severe (n = 3) emphysema, were imaged with a 1.5-T whole-body MR unit at four lung volumes (residual volume [RV], functional residual capacity [FRC], 1 L above FRC [FRC+1 L], total lung capacity [TLC]) with breath holds of 10-11 seconds, by using volumetric interpolated breath-hold examination. Each pair of volumes were registered, resulting in maps of 1H signal change between the two lung volumes. 3He MR imaging was performed at FRC+1 L by using a two-dimensional gradient-echo sequence. 1H signal change and 3He signal were measured and compared in corresponding regions of interest selected in ventral, intermediate, and dorsal areas.Results: In all volunteers and patients combined, proton signal difference between TLC and RV correlated positively with 3He signal (correlation coefficient R2 = 0.64, P < .001). Lower (P < .001) but positive correlation results from 1H signal difference between FRC and FRC+1 L (R2 = 0.44, P < .001). In healthy volunteers, 1H signal changes show a higher median and interquartile range compared with patients with obstructive disease and significant differences between nondependent and dependent regions.Conclusion: Findings in this study demonstrate that multivolume 1H MR imaging, without contrast material, can be used as a biomarker for regional ventilation, both in healthy volunteers and patients with obstructive lung disease. © RSNA, 2014. Source

Altes T.A.,University of Missouri | Mugler J.P.,University of Virginia | Ruppert K.,Center for Pulmonary Imaging Research | Tustison N.J.,University of Virginia | And 5 more authors.
Journal of Allergy and Clinical Immunology | Year: 2016

Background Lung ventilation defects identified by using hyperpolarized 3-helium gas (3He) lung magnetic resonance imaging (MRI) are prevalent in asthmatic patients, but the clinical importance of ventilation defects is poorly understood. Objectives We sought to correlate the lung defect volume quantified by using 3He MRI with clinical features in children with mild and severe asthma. Methods Thirty-one children with asthma (median age, 10 years; age range, 3-17 years) underwent detailed characterization and 3He lung MRI. Quantification of the 3He signal defined ventilation defect and hypoventilated, ventilated, and well-ventilated volumes. Results The ventilation defect to total lung volume fraction ranged from 0.1% to 11.6%. Children with ventilation defect percentages in the upper tercile were more likely to have severe asthma than children in the lower terciles (P =.005). The ventilation defect percentage correlated (P <.05 for all) positively with the inhaled corticosteroid dose, total number of controller medications, and total blood eosinophil counts and negatively with the Asthma Control Test score, FEV1 (percent predicted), FEV1/forced vital capacity ratio (percent predicted), and forced expiratory flow rate from 25% to 75% of expired volume (percent predicted). Conclusion The lung defect volume percentage measured by using 3He MRI correlates with several clinical features of asthma, including severity, symptom score, medication requirement, airway physiology, and atopic markers. © 2015 American Academy of Allergy, Asthma & Immunology. Source

Tkach J.A.,Oh | Walkup L.L.,Center for Pulmonary Imaging Research
Magnetic Resonance in Medicine | Year: 2016

Purpose: To implement pulmonary three-dimensional (3D) radial ultrashort echo-time (UTE) MRI in non-sedated, free-breathing neonates and adults with retrospective motion tracking of respiratory and intermittent bulk motion, to obtain diagnostic-quality, respiratory-gated images. Methods: Pulmonary 3D radial UTE MRI was performed at 1.5 tesla (T) during free breathing in neonates and adult volunteers for validation. Motion-tracking waveforms were obtained from the time course of each free induction decay's initial point (i.e., k-space center), allowing for respiratory-gated image reconstructions that excluded data acquired during bulk motion. Tidal volumes were calculated from end-expiration and end-inspiration images. Respiratory rates were calculated from the Fourier transform of the motion-tracking waveform during quiet breathing, with comparison to physiologic prediction in neonates and validation with spirometry in adults. Results: High-quality respiratory-gated anatomic images were obtained at inspiration and expiration, with less respiratory blurring at the expense of signal-to-noise for narrower gating windows. Inspiration-expiration volume differences agreed with physiologic predictions (neonates; Bland-Altman bias=6.2mL) and spirometric values (adults; bias=0.11L). MRI-measured respiratory rates compared well with the observed rates (biases=-0.5 and 0.2 breaths/min for neonates and adults, respectively). Conclusions: Three-dimensional radial pulmonary UTE MRI allows for retrospective respiratory self-gating and removal of intermittent bulk motion in free-breathing, non-sedated neonates and adults. © 2016 Wiley Periodicals, Inc. Source

Chang Y.V.,University of Washington | Chang Y.V.,Washington University in St. Louis | Quirk J.D.,University of Washington | Ruset I.C.,Xemed LLC | And 4 more authors.
Magnetic Resonance in Medicine | Year: 2014

Purpose To present in vivo, human validation of a previously proposed method to measure key pulmonary parameters related to lung microstructure and physiology. Some parameters, such as blood-air barrier thickness, cannot be measured readily by any other noninvasive modality. Methods Healthy volunteers (n = 12) were studied in 1.5T and 3T whole body human scanners using hyperpolarized xenon. Xenon uptake by lung parenchyma and blood was measured using a chemical shift saturation recovery sequence. Both dissolved-xenon peaks at 197 ppm and 217-218 ppm were fitted against a model of xenon exchange (MOXE) as functions of exchange time. Parameters related to lung function and structure can be obtained by fitting to this model. Results The following results were obtained from xenon uptake (averaged over all healthy volunteers): surface-area-to-volume ratio = 210 ± 50 cm-1; total septal wall thickness = 9.2 ± 6.5 μm; blood-air barrier thickness = 1.0 ± 0.3 μm; hematocrit = 27 ± 4%; pulmonary capillary blood transit time = 1.3 ± 0.3 s, in good agreement with literature values from invasive experiments. More detailed fitting results are listed in the text. Conclusion The initial in vivo human results demonstrate that our proposed methods can be used to noninvasively determine lung physiology by simultaneous quantification of a few important pulmonary parameters. This method is highly promising to become a versatile screening method for lung diseases. © 2013 Wiley Periodicals, Inc. Source

Young S.M.,Ohio State University | Liu S.,Cincinnati Childrens Hospital | Joshi R.,Cincinnati Childrens Hospital | Batie M.R.,Clinical Engineering | And 4 more authors.
Journal of Applied Physiology | Year: 2015

Synthesis and remodeling of the lung matrix is necessary for primary and compensatory lung growth. Because cyclic negative force is applied to developing lung tissue during the respiratory cycle, we hypothesized that stretch is a critical regulator of lung matrix remodeling. By using quantitative image analysis of whole-lung and whole-lobe elastin in situ zymography images, we demonstrated that elastase activity increased twofold during the alveolar stage of postnatal lung morphogenesis in the mouse. Remodeling was restricted to alveolar walls and ducts and was nearly absent in dense elastin band structures. In the mouse pneumonectomy model of compensatory lung growth, elastase activity increased threefold, peaking at 14 days postpneumonectomy and was higher in the accessory lobe compared with other lobes. Remodeling during normal development and during compensatory lung growth was different with increased major airway and pulmonary arterial remodeling during development but not regeneration, and with homogenous remodeling throughout the parenchyma during development, but increased remodeling only in subpleural regions during compensatory lung growth. Left lung wax plombage prevented increased lung elastin during compensatory lung growth. To test whether the adult lung retains an innate capacity to remodel elastin, we developed a confocal microscope-compatible stretching device. In ex vivo adult mouse lung sections, lung elastase activity increased exponentially with strain and in peripheral regions of lung more than in central regions. Our study demonstrates that lung elastase activity is stretch-dependent and supports a model in which externally applied forces influence the composition, structure, and function of the matrix during periods of alveolar septation. Copyright © 2015 the American Physiological Society. Source

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