Quantifying spatial and dynamic lung abnormalities with 3D PREFUL FLORET UTE imaging: A feasibility study.

Purpose: Pulmonary MRI faces challenges due to low proton density, rapid transverse magnetization decay, and cardiac and respiratory motion. The fermat-looped orthogonally encoded trajectories (FLORET) sequence addresses these issues with high sampling efficiency, strong signal, and motion robustness, but has not yet been applied to phase-resolved functional lung (PREFUL) MRI-a contrast-free method for assessing pulmonary ventilation during free breathing. This study aims to develop a reconstruction pipeline for FLORET UTE, enhancing spatial resolution for three-dimensional (3D) PREFUL ventilation analysis.

A thermally polarized, dissolved-phase Xe phantom for quality-control and multisite comparisons of gas-exchange imaging.

Harmonizing and validating Xe gas exchange imaging across multiple sites is hampered by a lack of a quantitative standard that 1) displays the unique spectral properties of Xe observed from human subjects in vivo and 2) has short enough T times to enable practical imaging. This work describes and demonstrates the development of two dissolved-phase, thermally polarized phantoms that mimic the in-vivo, red blood cell and membrane resonances of Xe dissolved in human lungs. Following optimization, combinations of two common organic solvents, acetone and dimethyl sulfoxide, resulted in two in-vivo-like dissolved-phase Xe phantoms yielding chemical shifts of 212.

Xe Image Processing Pipeline: An open-source, graphical user interface application for the analysis of hyperpolarized Xe MRI.

Purpose: Hyperpolarized Xe MRI presents opportunities to assess regional pulmonary microstructure and function. Ongoing advancements in hardware, sequences, and image processing have helped it become increasingly adopted for both research and clinical use. As the number of applications and users increase, standardization becomes crucial.

Same-Day Repeatability and 28-Day Reproducibility of Xenon MRI Ventilation in Children With Cystic Fibrosis in a Multi-Site Trial.

Background: MRI with xenon-129 gas (Xe MRI) can assess airflow obstruction and heterogeneity in lung diseases. Specifically, Xe MRI may represent a sensitive modality for future therapeutic trials of cystic fibrosis (CF) therapies. The reproducibility of Xe MRI has not yet been assessed in the context of a multi-site study.

Quantifying abnormal alveolar microstructure in cystic fibrosis lung disease via hyperpolarized Xe diffusion MRI.

Rationale: Cystic Fibrosis (CF) progresses through recurrent infection and inflammation, causing permanent lung function loss and airway remodeling. CT scans reveal abnormally low-density lung parenchyma in CF, but its microstructural nature remains insufficiently explored due to clinical CT limitations. To this end, diffusion-weighted Xe MRI is a non-invasive and validated measure of lung microstructure.

Detection of Bronchiolitis Obliterans Syndrome after Pediatric Hematopoietic Stem Cell Transplantation: An Official American Thoracic Society Clinical Practice Guideline.

Many children undergo allogeneic hematopoietic stem cell transplantation (HSCT) for the treatment of malignant and nonmalignant conditions. Unfortunately, pulmonary complications occur frequently post-HSCT, with bronchiolitis obliterans syndrome (BOS) being the most common noninfectious pulmonary complication. Current international guidelines contain conflicting recommendations regarding post-HSCT surveillance for BOS, and a recent NIH workshop highlighted the need for a standardized approach to post-HSCT monitoring.

A decay-modeled compressed sensing reconstruction approach for non-Cartesian hyperpolarized Xe MRI.

Purpose: Hyperpolarized Xe MRI benefits from non-Cartesian acquisitions that sample k-space efficiently and rapidly. However, their reconstructions are complex and burdened by decay processes unique to hyperpolarized gas. Currently used gridded reconstructions are prone to artifacts caused by magnetization decay and are ill-suited for undersampling.

B and magnetization decay correction for hyperpolarized Xe lung imaging using sequential 2D spiral acquisitions.

Purpose: To mitigate signal variations caused by inhomogeneous RF and magnetization decay in hyperpolarized Xe ventilation images using flip-angle maps generated from sequential 2D spiral ventilation images acquired in a breath-hold. Images and correction maps were compared with those obtained using conventional, 2D gradient-recalled echo.

Theory And Methods: Analytical expressions to predict signal intensity and uncertainty in flip-angle measurements were derived from the Bloch equations and validated by simulations and phantom experiments.

Childhood to adulthood: Accounting for age dependence in healthy-reference distributions in Xe gas-exchange MRI.

Purpose: Xenon-129 ( Xe) gas-exchange MRI is a pulmonary-imaging technique that provides quantitative metrics for lung structure and function and is often compared to pulmonary-function tests. Unlike such tests, it does not normalize to predictive values based on demographic variables such as age. Many sites have alluded to an age dependence in gas-exchange metrics; however, a procedure for normalizing metrics has not yet been introduced.

Pediatric Xe Gas-Transfer MRI-Feasibility and Applicability.

Background: Xe gas-transfer MRI provides regional measures of pulmonary gas exchange in adults and separates xenon in interstitial lung tissue/plasma (barrier) from xenon in red blood cells (RBCs). The technique has yet to be demonstrated in pediatric populations or conditions.

Purpose/hypothesis: To perform an exploratory analysis of Xe gas-transfer MRI in children.

Improving hyperpolarized Xe ADC mapping in pediatric and adult lungs with uncertainty propagation.

Rationale: Hyperpolarized (HP) Xe-MRI provides non-invasive methods to quantify lung function and structure, with the Xe apparent diffusion coefficient (ADC) being a well validated measure of alveolar airspace size. However, the experimental factors that impact the precision and accuracy of HP Xe ADC measurements have not been rigorously investigated. Here, we introduce an analytical model to predict the experimental uncertainty of Xe ADC estimates.

Hyperpolarized Xenon MRI Ventilation Defect Quantification via Thresholding and Linear Binning in Multiple Pulmonary Diseases.

Rationale: There is no agreed upon method for quantifying ventilation defect percentage (VDP) with high sensitivity and specificity from hyperpolarized (HP) gas ventilation MR images in multiple pulmonary diseases for both pediatrics and adults, yet identifying such methods will be necessary for future multi-site trials. Most HP gas MRI ventilation research focuses on a specific pulmonary disease and utilizes one quantification scheme for determining VDP. Here we sought to determine the potential of different methods for quantifying VDP from HP Xe images in multiple pulmonary diseases through comparison of the most utilized quantification schemes: linear binning and thresholding.

Removal of off-resonance xenon gas artifacts in pulmonary gas-transfer MRI.

Purpose: Hyperpolarized xenon ( Xe) gas-transfer imaging allows different components of pulmonary gas transfer-alveolar air space, lung interstitium/blood plasma (barrier), and red blood cells (RBCs)-to be assessed separately in a single breath. However, quantitative analysis is challenging because dissolved-phase Xe images are often contaminated by off-resonant gas-phase signal generated via imperfectly selective excitation. Although previous methods required additional data for gas-phase removal, the method reported here requires no/minimal sequence modifications/data acquisitions, allowing many previously acquired images to be corrected retroactively.

Effects of neonatal lung abnormalities on parenchymal R * estimates.

Infants admitted to the neonatal intensive care unit (NICU) often suffer from multifaceted pulmonary morbidities that are not well understood. Ultrashort echo time (UTE) magnetic resonance imaging (MRI) is a promising technique for pulmonary imaging in this population without requiring exposure to ionizing radiation. The aims of this study were to investigate the effect of neonatal pulmonary disease on R * and tissue density and to utilize numerical simulations to evaluate the effect of different alveolar structures on predicted R *.

The Clinical Use of Lung MRI in Cystic Fibrosis: What, Now, How?

To assess airway and lung parenchymal damage noninvasively in cystic fibrosis (CF), chest MRI has been historically out of the scope of routine clinical imaging because of technical difficulties such as low proton density and respiratory and cardiac motion. However, technological breakthroughs have emerged that dramatically improve lung MRI quality (including signal-to-noise ratio, resolution, speed, and contrast). At the same time, novel treatments have changed the landscape of CF clinical care.

Quantitative inspiratory-expiratory chest CT to evaluate pulmonary involvement in pediatric hematopoietic stem-cell transplantation patients.

Pulmonary complications following allogeneic hematopoietic stem-cell transplantation (HSCT) are a significant source of morbidity and complications may arise from a myriad of infectious and noninfectious sources. These complications may occur soon or many months post-transplantation and can have a broad range of outcomes. Surveillance for pulmonary involvement in the pediatric HSCT population can be challenging due to poor compliance with clinical pulmonary function testing, primarily spirometry, and there may be a role for clinical imaging to provide an additional means of monitoring, particularly in the era of clinical low-dose computed tomography (CT) protocols.

Sensitive structural and functional measurements and 1-year pulmonary outcomes in pediatric cystic fibrosis.

Background: Two functional measurements (multiple breath washout [MBW] and hyperpolarized Xe ventilation magnetic resonance imaging [Xe MRI]) have been shown to be more sensitive to cystic fibrosis (CF) lung obstruction than traditional spirometry. However, functional techniques may be sensitive to different underlying structural abnormalities. The purpose of this study was to determine relationships between these functional markers, their pathophysiology, and 1-year clinical outcomes.

Xe MRI as a measure of clinical disease severity for pediatric asthma.

Background: Measurement of regional lung ventilation with hyperpolarized Xe magnetic resonance imaging (Xe MRI) in pediatric asthma is poised to advance our understanding of disease mechanisms and pathophysiology in a disorder with diverse clinical phenotypes. Xe MRI has not been investigated in a pediatric asthma cohort.

Objective: We hypothesized that Xe MRI is feasible and can demonstrate ventilation defects that relate to and predict clinical severity in a pediatric asthma cohort.

A semi-empirical model to optimize continuous-flow hyperpolarized Xe production under practical cryogenic-accumulation conditions.

Continuous-flow spin exchange optical pumping (SEOP) with cryogenic accumulation is a powerful technique to generate multiple, large volumes of hyperpolarized (HP) Xe in rapid succession. It enables a range of studies, from dark matter tracking to preclinical and clinical MRI. Multiple analytical models based on first principles atomic physics and device-specific design features have been proposed for individual processes within HP Xe production.

Lung microstructure in adolescent idiopathic scoliosis before and after posterior spinal fusion.

Adolescent idiopathic scoliosis (AIS) is associated with decreased respiratory quality of life and impaired diaphragm function. Recent hyperpolarized helium (HHe) MRI studies show alveolarization continues throughout adolescence, and mechanical forces are known to impact alveolarization. We therefore hypothesized that patients with AIS would have alterations in alveolar size, alveolar number, or alveolar septal dimensions compared to adolescents without AIS, and that posterior spinal fusion (PSF) might reverse these differences.