Comparison of 3 He and 129 Xe MRI for evaluation of lung microstructure and ventilation at 1.5T

Purpose Hyperpolarized 129Xe MRI characterizes regional lung ventilation in a variety of disease populations, with high sensitivity to airway obstruction in early disease. However, ventilation images are usually limited to a single breath‐hold and most‐often acquired using gradient‐recalled echo sequences with thick slices (~10‐15 mm), which increases partial‐volume effects, limits ability to observe small defects, and suffers from imperfect slice selection. We demonstrate higher‐resolution ventilation images, in shorter breath‐holds, using FLORET (Fermat Looped ORthogonally Encoded Trajectories), a center‐out 3D‐spiral UTE sequence. Methods In vivo human adult (N = 4; 2 healthy, 2 with cystic fibrosis) 129Xe images were acquired using 2D gradient‐recalled echo, 3D radial, and FLORET. Each sequence was acquired at its highest possible resolution within a 16‐second breath‐hold with a minimum voxel dimension of 3 mm. Images were compared using 129Xe ventilation defect percentage, SNR, similarity coefficients, and vasculature cross‐sections. Results The FLORET sequence obtained relative normalized SNR, 40% greater than 2D gradient‐recalled echo (P = .012) and 26% greater than 3D radial (P = .067). Moreover, the FLORET images were acquired with 3‐fold‐higher nominal resolution in a 15% shorter breath‐hold. Finally, vasculature was less prominent in FLORET, likely due to diminished susceptibility‐induced dephasing at shorter TEs afforded by UTE sequences. Conclusion The FLORET sequence yields higher SNR for a given resolution with a shorter breath‐hold than traditional ventilation imaging techniques. This sequence more accurately measures ventilation abnormalities and enables reduced scan times in patients with poor compliance and severe lung disease.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Improved pulmonary ¹²⁹Xe ventilation imaging via 3D‐spiral UTE MRI

Willmering

Niedbalski

Wang

et al. 2019

“…Hyperpolarized 129 Xe MRI is a promising tool both for research and clinical applications that can fill the aforementioned gaps . Imaging of the gas distribution after inhalation of hyperpolarized 129 Xe provides a highly sensitive and reproducible technique for the assessment of local airflow obstruction . Beyond that, upon inhalation by a subject, xenon dissolves in the lung tissue and blood, which affects its Larmor frequency due to chemical shift.…”

Section: Introductionmentioning

confidence: 99%

Mapping of regional lung microstructural parameters using hyperpolarized ¹²⁹Xe dissolved‐phase MRI in healthy volunteers and patients with chronic obstructive pulmonary disease

Kern

Gutberlet

Voskrebenzev

et al. 2018

Purpose To develop a novel technique for voxel‐based mapping of lung microstructural parameters using hyperpolarized 129Xe dissolved‐phase MR imaging during saturation recovery. Methods A pulse sequence using a highly undersampled stack‐of‐stars trajectory was developed, and low‐rank plus sparse matrix decomposition was employed for reconstruction of regional 129Xe uptake dynamics into lung tissue. In 4 healthy volunteers and 9 patients with chronic obstructive pulmonary disease, the technique was tested and compared to chemical shift saturation recovery spectroscopy in patients. Reproducibility of 129Xe gas uptake imaging was assessed by computing coefficients of variation, and results were compared with other modalities. Results Numerical simulations and results from in vivo measurements in patients with chronic obstructive pulmonary disease showed that septal wall thickness and surface‐to‐volume ratio can be measured with an accuracy close to spectroscopic measurements. The average of the microstructural parameters of the total lung volume showed good reproducibility (coefficient of variation wall thickness: 7.4% coefficient of variation surface‐to‐volume ratio: 7.5%) and correlated strongly with the findings of global chemical shift saturation recovery spectroscopy. Gravitational gradients of microstructural parameters and increased heterogeneity in chronic obstructive pulmonary disease patients were observed. Conclusion A novel technique for mapping of regional lung microstructural parameters was introduced, and its feasibility was shown in healthy volunteers and chronic obstructive pulmonary disease patients.

“…There have been substantial advances in functional pulmonary MRI in the last few decades from imaging gases dominated by polarized noble gases and from tissue MRI, notably from the effect of breathing pure oxygen on the tissue T 1 . The present study is anatomical in comparison.…”

Section: Introductionmentioning

confidence: 96%

T₁, T₁ contrast, and Ernst‐angle images of four rat‐lung pathologies

Kuethe

Hix

Fredenburgh

2018

Purpose To initiate the archive of relaxation‐weighted images that may help discriminate between pulmonary pathologies relevant to acute respiratory distress syndrome. MRI has the ability to distinguish pathologies by providing a variety of different contrast mechanisms. Lungs have historically been difficult to image with MRI but image quality is sufficient to begin cataloging the appearance of pathologies in T1‐ and T2‐weighted images. This study documents T1 and the use of T1 contrast with four experimental rat lung pathologies. Methods Inversion‐recovery and spoiled steady state images were made at 1.89 T to measure T1 and document contrast in rats with atelectasis, lipopolysaccharide‐induced inflammation, ventilator‐induced lung injury (VILI), and injury from saline lavage. Higher‐resolution Ernst‐angle images were made to see patterns of lung infiltrations. Results T1‐weighted images showed minimal contrast between pathologies, similar to T1‐weighted images of other soft tissues. Images taken shortly after magnetization inversion and displayed with inverted contrast highlight lung pathologies. Ernst‐angle images distinguish the effects of T1 relaxation and spin density and display distinctive patterns. T1 for pathologies were: atelectasis, 1.25 ± 0.046 s; inflammation from instillation of lipopolysaccharide, 1.24 ± 0.015 s; VILI, 1.55 ± 0.064 s (p = 0.0022 vs. normal lung); and injury from saline lavage, 1.90±0.080 s (p = 0.0022 vs. normal lung; p = 0.0079 vs. VILI). T1 of normal lung and erector spinae muscle were 1.25 ± 0.028 s and 1.02 ± 0.027 s, respectively (p = 0.0022). Conclusions Traditional T1‐weighting is subtle. However, images made with inverted magnetization and inverted contrast highlight the pathologies and Ernst‐angle images aid in distinguishing pathologies.