Detection of emphysema in rat lungs by using magnetic resonance measurements of
            <sup>3</sup>
            He diffusion

Chen, X. Josette; Hedlund, Laurence W.; Möller, Harald E.; Chawla, Mark S.; Maronpot, Robert R.; Johnson, G. Allan

doi:10.1073/pnas.97.21.11478

Cited by 163 publications

(183 citation statements)

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“…In the simplest sense, DWI and q-space DWS give equivalent information since the rms displacement and ADC are related through Eq. [2]. This relation is supported by an excellent correlation between mean ADC from DWI and the rms displacements from q-space DWS.…”

Section: Discussionmentioning

confidence: 62%

“…HYPERPOLARIZED 3 HE GAS (HHe) is an inhaled contrast agent that provides detailed information about lung function and structure in MRI (1)(2)(3)(4). Because no ionizing radiation is used in MRI and 3 He is a biologically inert gas, HHe MRI is a very safe imaging technique.…”

mentioning

confidence: 99%

“…In recent years, HHe diffusion-weighted imaging (DWI) has been used to assess the lung microstructure for the detection and characterization of emphysema. In emphysema, a disease characterized by tissue destruction and enlargement of lung alveoli, the measured HHe ADC is elevated relative to that of healthy adults (2,6,7). Histological studies in animal models of emphysema have correlated this elevation in ADC with increased alveolar size (8).…”

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confidence: 99%

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q‐space analysis of lung morphometry in vivo with hyperpolarized³He spectroscopy

Shanbhag

Altes

Miller

et al. 2006

Magnetic Resonance Imaging

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Purpose:To examine the utility of a 3 He spectroscopic q-space technique for detecting changes in lung morphometry in vivo. Materials and Methods:A diffusion-weighted spectroscopy sequence was used to collect global diffusion data from healthy adults (N ϭ 11), healthy children (N ϭ 5), and chronic obstructive pulmonary disease (COPD) patients (N ϭ 2) using 40 cc of hyperpolarized 3 He gas within a two second breathhold. Displacement probability profiles (DPP) were obtained by Fourier transformation of diffusion data with respect to q. A bi-Gaussian model was used to decompose the DPPs into narrow and broad components, characterized by root-mean-square displacements X rms1 and X rms2 , respectively. Results:In healthy adults, the narrow component (X rms,1 ) of the DPP had a mean displacement of 188 Ϯ 10 m, slightly less than the reported average size of the alveoli. The broad component (X rms,2 ) had a mean value of 474 Ϯ 44 m, comparable to the diameter of the respiratory bronchioles in the acinus. In children, both X rms1 (167 Ϯ 4 m) and X rms2 (382 Ϯ 22 m) compared to healthy adults (P Ͻ 0.01). In COPD patients, the mean displacements were elevated (X rms1 : 265 Ϯ 71 m; X rms2 : 530 Ϯ 109 m) compared to healthy adults. Excellent correlation was found between rms displacements and age (age vs. X rms,1 : r ϭ 0.78, P Ͻ 0.001; age vs. X rms,2 : r ϭ 0.90, P Ͻ 0.001). Conclusion:The q-space parameters agreed remarkably well with published alveolar morphometry data. The results suggest that the technique may be sensitive to disease, as evident from the elevated mean displacements in COPD patients compared to healthy volunteers. Detailed lung microstructural information can be obtained using a very low volume of inhaled 3 He.

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Section: Discussionmentioning

confidence: 62%

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confidence: 99%

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confidence: 99%

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q‐space analysis of lung morphometry in vivo with hyperpolarized³He spectroscopy

Shanbhag

Altes

Miller

et al. 2006

Magnetic Resonance Imaging

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“…Considering a wall with N well-separated holes per area A, the overall flux J, averaged over the area of the wall, will be [10] Viewed overall, J can be expressed in terms of the overall diffusivity LRDC and the overall concentration gradient (C 2 -C 1 )/L, [11] giving [12] where n is the number density of holes, n=N/A.…”

Section: Diffusion Through Holesmentioning

confidence: 99%

“…Measured ADC values in normal human lungs are approximately 0.2 cm 2 /s and increase in emphysema; in severely diseased lungs, 0.6 cm 2 / s is common (11). Likewise, increases of ADC in rats are observed in emphysema (12,14). 3 He ADC measurements have yet to enter common clinical practice, though they are regarded as the emerging new gold-standard for characterizing the emphysema-component of COPD.…”

Section: Introductionmentioning

confidence: 99%

The Role of Collateral Paths in Long-range Diffusion of 3He in Lungs

et al. 2008

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Rationale and Objectives-The hyperpolarized 3 He long-range diffusion coefficient (LRDC) in lungs is sensitive to changes in lung structure due to emphysema, reflecting the increase in collateral paths resulting from tissue destruction. However, no clear understanding of LRDC in healthy lungs has emerged. Here we compare LRDC measured in healthy lungs with computer simulations of diffusion along the airway tree with no collateral connections.Materials and Methods-Computer simulations of diffusion of spatially modulated spin magnetization were performed in computer generated, symmetric-branching models of lungs and compared with existing LRDC measurements in canine and human lungs.Results-The simulations predict LRDC values of order 0.001 cm 2 /s, approximately 20 times smaller than the measured LRDC. We consider and rule out possible mechanisms for LRDC not included in the simulations: incomplete breath hold, cardiac motion, and passage of dissolved 3 He through airway walls. However, a very low density of small (micron) holes in the airways is shown to account for the observed LRDC.Conclusion-It is proposed that LRDC in healthy lungs is determined by small collateral pathways.

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Measurements of hyperpolarized gas properties in the lung. part III:3HeT1

Hedlund

et al. 2001

Magn. Reson. Med.

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Hyperpolarized 3He spin‐lattice relaxation was investigated in the guinea pig lung using spectroscopy and imaging techniques with a repetitive RF pulse series. T1 was dominated by interactions with oxygen and was used to measure the alveolar O2 partial pressure. In animals ventilated with a mixture of 79% 3He and 21% O2, T1 dropped from 19.6 sec in vivo to 14.6 sec after cardiac arrest, reflecting the termination of the intrapulmonary gas exchange. The initial difference in oxygen concentration between inspired and alveolar air, and the temporal decay during apnea were related to functional parameters. Estimates of oxygen uptake were 29 ± 11 mL min−1 kg−1 under normoxic conditions, and 9.0 ± 2.0 mL min−1 kg−1 under hypoxic conditions. Cardiac output was estimated to be 400 ± 160 mL min−1 kg−1. The functional residual capacity derived from spirometric magnetic resonance experiments varied with body mass between 5.4 ± 0.3 mL and 10.7 ± 1.1 mL. Magn Reson Med 45:421–430, 2001. © 2001 Wiley‐Liss, Inc.

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Detection of emphysema in rat lungs by using magnetic resonance measurements of ³ He diffusion

Abstract: Emphysema is a pulmonary disease characterized by alveolar wall destruction, resulting in enlargement of gas exchange spaces without fibrosis. This condition is a part of chronic obstructive pulmonary disease (COPD), which causes 3.5% of deaths worldwide [Anonymous (

Cited by 163 publications

References 28 publications

q‐space analysis of lung morphometry in vivo with hyperpolarized³He spectroscopy

q‐space analysis of lung morphometry in vivo with hyperpolarized³He spectroscopy

The Role of Collateral Paths in Long-range Diffusion of 3He in Lungs

Measurements of hyperpolarized gas properties in the lung. part III:3HeT1

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Detection of emphysema in rat lungs by using magnetic resonance measurements of 3 He diffusion

Abstract: Emphysema is a pulmonary disease characterized by alveolar wall destruction, resulting in enlargement of gas exchange spaces without fibrosis. This condition is a part of chronic obstructive pulmonary disease (COPD), which causes 3.5% of deaths worldwide [Anonymous (

Cited by 163 publications

References 28 publications

q‐space analysis of lung morphometry in vivo with hyperpolarized3He spectroscopy

q‐space analysis of lung morphometry in vivo with hyperpolarized3He spectroscopy

The Role of Collateral Paths in Long-range Diffusion of 3He in Lungs

Measurements of hyperpolarized gas properties in the lung. part III:3HeT1

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Product

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Detection of emphysema in rat lungs by using magnetic resonance measurements of ³ He diffusion

q‐space analysis of lung morphometry in vivo with hyperpolarized³He spectroscopy

q‐space analysis of lung morphometry in vivo with hyperpolarized³He spectroscopy