Purpose
To develop and assess a method for acquiring coregistered proton anatomical and hyperpolarized 129Xe ventilation MR images of the lungs with compressed sensing (CS) in a single breath hold.
...Methods
Retrospective CS simulations were performed on fully sampled ventilation images acquired from one healthy smoker to optimize reconstruction parameters. Prospective same‐breath anatomical and ventilation images were also acquired in five ex‐smokers with an acceleration factor of 3 for hyperpolarized 129Xe images, and were compared to fully sampled images acquired during the same session. The following metrics were used to assess data fidelity: mean absolute error (MAE), root mean square error, and linear regression of the signal intensity between fully sampled and undersampled images. The effect of CS reconstruction on two quantitative imaging metrics routinely reported percentage ventilated volume (%VV) and heterogeneity score was also investigated.
Results
Retrospective simulations showed good agreement between fully sampled and CS‐reconstructed (acceleration factor of 3) images with MAE (root mean square error) of 3.9% (4.5%). The prospective same‐breath images showed a good match in ventilation distribution with an average R2 of 0.76 from signal intensity linear regression and a negligible systematic bias of +0.1% in %VV calculation. A bias of −1.8% in the heterogeneity score was obtained.
Conclusion
With CS, high‐quality 3D images of hyperpolarized 129Xe ventilation (resolution 4.2 × 4.2 × 7.5 mm3) can be acquired with coregistered 1H anatomical MRI in a 15‐s breath hold. The accelerated acquisition time dispenses with the need for registration between separate breath‐hold 129Xe and 1H MRI, enabling more accurate %VV calculation.
Existing models of (129)Xe diffusive exchange for lung microstructural modeling with time-resolved MR spectroscopy data have considered analytical solutions to one-dimensional, homogeneous models of ...the lungs with specific assumptions about the alveolar geometry. In order to establish a model system for simulating the effects of physiologically-realistic changes in physical and microstructural parameters on (129)Xe exchange NMR, we have developed a 3D alveolar capillary model for finite element analysis. To account for the heterogeneity of the alveolar geometry across the lungs, we have derived realistic geometries for finite element analysis based on 2D histological samples and 3D micro-CT image volumes obtained from ex vivo biopsies of lung tissue from normal subjects and patients with interstitial lung disease. The 3D alveolar capillary model permits investigation of the impact of alveolar geometrical parameters and diffusion and perfusion coefficients on the in vivo measured (129)Xe CSSR signal response. The heterogeneity of alveolar microstructure that is accounted for in image-based models resulted in considerable alterations to the shape of the (129)Xe diffusive uptake curve when compared to 1D models. Our findings have important implications for the future design and optimization of (129)Xe MR experiments and in the interpretation of lung microstructural changes from this data.
To develop and apply an image acquisition and analysis strategy for spatial comparison of computed tomography (CT)-ventilation images with hyperpolarized gas magnetic resonance imaging (MRI).
Eleven ...lung cancer patients underwent xenon-129 (
Xe) and helium-3 (
He) ventilation MRI and coregistered proton (
H) anatomic MRI. Expiratory and inspiratory breath-hold CTs were used for deformable image registration and calculation of 3 CT-ventilation metrics: Hounsfield unit (CT
), Jacobian (CT
), and specific gas volume change (CT
). Inspiration CT and hyperpolarized gas ventilation MRI were registered via same-breath anatomic
H-MRI. Voxel-wise Spearman correlation coefficients were calculated between each CT-ventilation image and its corresponding
He-/
Xe-MRI, and for the mean values in regions of interest (ROIs) ranging from fine to coarse in-plane dimensions of 5 × 5, 10 × 10, 15 × 15, and 20 × 20, located within the lungs as defined by the same-breath
H-MRI lung mask. Correlation of
He and
Xe-MRI was also assessed.
Spatial correlation of CT-ventilation against
He/
Xe-MRI increased with ROI size. For example, for CT
, mean ± SD Spearman coefficients were 0.37 ± 0.19/0.33 ± 0.17 at the voxel-level and 0.52 ± 0.20/0.51 ± 0.18 for 20 × 20 ROIs, respectively. Correlations were stronger for CT
than for CT
or CT
. Correlation of
He with
Xe-MRI was consistently higher than either gas against CT-ventilation maps over all ROIs (P < .05). No significant differences were observed between CT-ventilation versus
He-MRI and CT-ventilation versus
Xe-MRI.
Comparison of ventilation-related measures from CT and registered hyperpolarized gas MRI is feasible at a voxel level using a dedicated acquisition and analysis protocol. Moderate correlation between CT-ventilation and MRI exists at a regional level. Correlation between MRI and CT is significantly less than that between
He and
Xe-MRI, suggesting that CT-ventilation surrogate measures may not be measuring lung ventilation alone.
This study aimed to assess the suitability of hyperpolarized 129Xe (HPXe) MRI for noninvasive longitudinal evaluation of pulmonary function in preclinical lung cancer models. A mouse model of lung ...cancer (LC) was induced in 5 mice by intraperitoneal injection of urethane, while a negative-control (NC) mice (N = 5) was prepared by injection of saline solution. Longitudinal HPXe MRI was performed over a 5-month period to monitor lung ventilation and gas exchange. The treatment efficacy of ethyl pyruvate (EP), an anti-inflammatory drug, to the mouse LC model was monitored using HPXe MRI by commencing administration of EP pre (early-phase) and 1-month post (late-phase) injection of urethane (N = 5 mice for each group). Gas-exchange function in LC mice was significantly reduced at 1-month after urethane injection compared with NC mice administered with saline (P<0.01). Thereafter, it remained consistently lower than that of the NC group for the full 5-month measurement period. In contrast, the ventilation function of the LC model mice was not significantly different to that of the NC mice. Histological analysis revealed alveolar epithelial hyperplasia in LC mice alveoli at 1 month after urethane injection, and adenoma was confirmed 3 months after the injection. The early- and late-phase EP interventions were found to improve HPXe MRI metrics (reduced at 1 month postinjection of urethane) and significantly inhibit tumor growth. These results suggest that HPXe MRI gas-exchange metrics can be used to quantitatively assess changes in the precancerous lesion microenvironment and to evaluate therapeutic efficacy in cancer. Thus, HPXe MRI can be utilized to noninvasively monitor pulmonary pathology during LC progression and can visualize functional changes during therapy.
The front cover artwork is provided by the group of Dr. Neil J. Stewart, Prof. Hiroshi Hirata, and Dr. Shingo Matsumoto (Hokkaido University, Japan) as well as Dr. Takuya Hashimoto (Chiba University, ...Japan). The image shows hyperpolarized 13C fumarate metabolism to hyperpolarized 13C malate, which is released into the extracellular space in regions of necrotic cell death, where the cell membrane is disrupted. Read the full text of the Article at 10.1002/cphc.202001038.
“We investigated several aspects of the process of PHIP‐induced polarization of 1‐13Cfumarate and its application in vitro and in vivo. In particular, we have report a cost‐effective synthetic pathway for high‐yield production 1‐13Cacetylenedicarboxylic acid…” This and more about the story behind the front cover can be found in the Article at 10.1002/cphc.202001038.
Hyperpolarized 1-
Cfumarate is a promising magnetic resonance imaging (MRI) biomarker for cellular necrosis, which plays an important role in various disease and cancerous pathological processes. To ...demonstrate the feasibility of MRI of 1-
Cfumarate metabolism using parahydrogen-induced polarization (PHIP), a low-cost alternative to dissolution dynamic nuclear polarization (dDNP), a cost-effective and high-yield synthetic pathway of hydrogenation precursor 1-
Cacetylenedicarboxylate (ADC) was developed. The trans-selectivity of the hydrogenation reaction of ADC using a ruthenium-based catalyst was elucidated employing density functional theory (DFT) simulations. A simple PHIP set-up was used to generate hyperpolarized 1-
Cfumarate at sufficient
C polarization for ex vivo detection of hyperpolarized
C malate metabolized from fumarate in murine liver tissue homogenates, and in vivo
C MR spectroscopy and imaging in a murine model of acetaminophen-induced hepatitis.
The front cover artwork is provided by the group of Dr. Neil J. Stewart, Prof. Hiroshi Hirata, and Dr. Shingo Matsumoto (Hokkaido University, Japan) as well as Dr. Takuya Hashimoto (Chiba University, ...Japan). The image shows hyperpolarized
C fumarate metabolism to hyperpolarized
C malate, which is released into the extracellular space in regions of necrotic cell death, where the cell membrane is disrupted. Read the full text of the Article at 10.1002/cphc.202001038.
Purpose
Imaging of the different resonances of dissolved hyperpolarized xenon‐129 (129Xe) in the lung is performed using a four‐echo flyback 3D radial spectroscopic imaging technique and is evaluated ...in healthy volunteers (HV) and subjects with idiopathic pulmonary fibrosis (IPF).
Theory and Methods
10 HV and 25 subjects with IPF underwent dissolved 129Xe MRI at 1.5T. IPF subjects underwent same day pulmonary function tests to measure forced vital capacity and the diffusion capacity of the lung for carbon monoxide (DLCO). A four‐point echo time technique with k‐space chemical‐shift modeling of gas, dissolved 129Xe in lung tissue/plasma (TP) and red blood cells (RBC) combined with a 3D radial trajectory was implemented within a 14‐s breath‐hold.
Results
Results show an excellent chemical shift separation of the dissolved 129Xe compartments and gas contamination removal, confirmed by a strong agreement between average imaging and global spectroscopy RBC/TP ratio measurements. Subjects with IPF exhibited reduced imaging gas transfer when compared to HV. A significant increase of the amplitude of RBC signal cardiogenic oscillation was also observed. In IPF subjects, DLCO% predicted was significantly correlated with RBC/TP and RBC/GAS ratios and the correlations were stronger in the inferior and periphery sections of the lungs.
Conclusion
Lung MRI of dissolved 129Xe was performed with a four‐echo spectroscopic imaging method. Subjects with IPF demonstrated reduced xenon imaging gas transfer and increased cardiogenic modulation of dissolved xenon signal in the RBCs when compared to HV.
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