Hyperpolarized Xe MRI and Spectroscopy: Quantitative Measurements, Results, and Emerging Opportunities.

Hyperpolarized xenon 129 (Xe) MRI uses inhaled Xe gas to visualize pulmonary function and microstructure. This review aims to summarize established and emerging quantitative measurements derived from Xe MRI and MR spectroscopy (MRS) and illustrate their clinical applications in the characterization and management of cardiopulmonary diseases. They are well tolerated by adults and children with pulmonary disease, employ no ionizing radiation, and their measurements have been validated by correlation with pulmonary function tests in various cardiopulmonary diseases.

Integration of mass cytometry and single-cell RNA-sequencing of cells in bronchoalveolar lavage.

Single-cell RNA sequencing (sc-RNA-seq) is a popular method for characterization of cell populations. However, the relationship between RNA and protein expression in cells is often discordant. Protein-based detection methods, such as cytometry by time-of-flight (CyTOF), can provide complementary data to sc-RNA-seq.

Quantification of Xe MRI Ventilation-defect-percent Using Binary-threshold, Gaussian Linear-Binning and K-means Methods: Differences in Asthma and COPD.

Rationale And Objectives: Hyperpolarized Xe magnetic resonance imaging (MRI) provides a way to quantify ventilation heterogeneity as ventilation defect percent (VDP), calculated as the volume of unventilated lung volume normalized to the thoracic cavity volume. Currently used methods for quantifying VDP include (1) binary signal-intensity thresholds (Binary-threshold, BT), (2) Gaussian transformation of signal-intensity histogram with standard deviation thresholds or Gaussian-linear-binning (GLB), and (3) iterative centroid-based clustering of the signal-intensity histogram (k-means). These methods have not been directly compared in patients with asthma and chronic obstructive pulmonary disease (COPD), in whom ventilation defects are hallmark findings.

Three-Dimensional Free-Breathing Ultrashort Echo Time (UTE) H MRI Regional Ventilation: Comparison With Hyperpolarized Xe MRI and Pulmonary Function Testing in Healthy Volunteers and People With Cystic Fibrosis.

MRI can provide localized assessment of lung function for monitoring people with lung disease. Hyperpolarized Xe MRI directly images pulmonary gas distribution but requires specialized hardware. Conventional H MRI acquisitions can also provide functional maps using free-breathing approaches.

The Canadian Lung Outcomes in Users of Vaping Devices (CLOUD) Study: protocol for a prospective, observational cohort study.

Introduction: The rapid growth in popularity of e-cigarettes over the past decade has prompted concerns about their impact on long-term respiratory health. Small airway injury is suspected to be a direct consequence of e-cigarette use and may be quantifiable by novel structural and functional diagnostic modalities.

Methods And Analysis: In a multicentre observational longitudinal study, participants will be enrolled in either an adolescent (ages ≥12 and <19 years) or an adult arm (≥19 years old) and followed over 3 years across three time points (baseline, 18 months and 36 months).

A Systematic Review of the Variability of Ventilation Defect Percent Generated From Hyperpolarized Noble Gas Pulmonary Magnetic Resonance Imaging.

Hyperpolarized (HP) gas pulmonary MR ventilation images are typically quantified using ventilation defect percent (VDP); however, the test-retest variability of VDP has not been systematically established in multi-center trials. Herein, we perform a systematic review of the test-retest literature on the variability of VDP, and similar metrics, generated from HP MRI. This review utilizes the Medline, EMBASE, and EBM Reviews databases and includes studies that assessed the variability of HP MRI VDP.

Transcriptomic profiling of the airway epithelium in COPD links airway eosinophilia to type 2 inflammation and corticosteroid response.

Background: A subset of COPD patients have high levels of eosinophils in the distal airways ("airway eosinophilia").

Objectives: To compare the gene expression of type 2 inflammation in airway epithelial brushings of COPD patients with and without airway eosinophilia and to investigate the changes after inhaled corticosteroids (ICS).

Methods: analyses of the DISARM randomised controlled trial investigated the expression of airway inflammation (type 1, 2 and 17), interleukin (IL)-13 and mast cell gene signatures at baseline and after 12-week ICS treatment.

Pulmonary Xe MRI: CNN Registration and Segmentation to Generate Ventilation Defect Percent with Multi-center Validation.

Rationale And Objectives: Hyperpolarized Xe MRI quantifies ventilation-defect-percent (VDP), the ratio of Xe signal-void to the anatomic H MRI thoracic-cavity-volume. VDP is associated with airway inflammation and disease control and serves as a treatable trait in therapy studies. Semi-automated VDP pipelines require time-intensive observer interactions.

A proposed approach to pulmonary long COVID: a viewpoint.

https://bit.ly/48WceB3

Xe MRI and Oscillometry of Irritant-Induced Asthma After Bronchial Thermoplasty.

Irritant-induced asthma (IIA) may develop after acute inhalational exposure in individuals without preexisting asthma. The effect of bronchial thermoplasty to treat intractable, worsening IIA has not yet been described. We evaluated a previously healthy 52-year-old man after inhalation of an unknown white powder.

Cluster analysis to identify long COVID phenotypes using Xe magnetic resonance imaging: a multicentre evaluation.

Background: Long COVID impacts ∼10% of people diagnosed with coronavirus disease 2019 (COVID-19), yet the pathophysiology driving ongoing symptoms is poorly understood. We hypothesised that Xe magnetic resonance imaging (MRI) could identify unique pulmonary phenotypic subgroups of long COVID. Therefore, we evaluated ventilation and gas exchange measurements with cluster analysis to generate imaging-based phenotypes.

Mild airways obstruction: spirometric diagnostic pitfalls and solutions.

Purpose Of Review: Spirometry is a validated tool in the diagnosis of obstructive airways disease. However, it may be insufficiently sensitive in detecting airflow limitation in the small airways. This review highlights common clinical scenarios wherein airflow limitation may be missed or overlooked.

Post-COVID-19 dyspnoea and pulmonary imaging: a systematic review and meta-analysis.

Background: A proportion of coronavirus disease 2019 (COVID-19) survivors experience persistent dyspnoea without measurable impairments in lung function. We performed a systematic review and meta-analysis to determine relationships between dyspnoea and imaging abnormalities over time in post-COVID-19 patients.

Methods: Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we analysed studies published prior to 15 September 2022 and indexed by Google Scholar, PubMed and LitCOVID which assessed chest imaging in adults ≥3 months after COVID-19.

Xe MRI Ventilation Defects in Asthma: What is the Upper Limit of Normal and Minimal Clinically Important Difference?

Rationale And Objectives: The minimal clinically important difference (MCID) and upper limit of normal (ULN) for MRI ventilation defect percent (VDP) were previously reported for hyperpolarized He gas MRI. Hyperpolarized Xe VDP is more sensitive to airway dysfunction than He, therefore the objective of this study was to determine the ULN and MCID for Xe MRI VDP in healthy and asthma participants.

Materials And Methods: We retrospectively evaluated healthy and asthma participants who underwent spirometry and XeMRI on a single visit; participants with asthma completed the asthma control questionnaire (ACQ-7).

CT Mucus Score and Xe MRI Ventilation Defects After 2.5 Years' Anti-IL-5Rα in Eosinophilic Asthma.

Background: We previously showed in patients with poorly controlled eosinophilic asthma that a single dose of benralizumab resulted in significantly improved Asthma Control Questionnaire (ACQ-6) score and Xe MRI ventilation defect percent (VDP) 28 days postinjection, and Xe MRI VDP and CT airway mucus occlusions were shown to independently predict this early ACQ-6 response to benralizumab.

Research Question: Do early VDP responses at 28 days persist, and do FEV, fractional exhaled nitric oxide, and mucus plug score improve during a 2.5 year treatment period?

Study Design And Methods: Participants with poorly controlled eosinophilic asthma completed spirometry, ACQ-6, and MRI, 28 days, 1 year, and 2.

A Soft Labeling Approach to Develop Automated Algorithms that Incorporate Uncertainty in Pulmonary Opacification on Chest CT using COVID-19 Pneumonia.

Rationale And Objectives: Hard data labels for automated algorithm training are binary and cannot incorporate uncertainty between labels. We proposed and evaluated a soft labeling methodology to quantify opacification and percent well-aerated lung (%WAL) on chest CT, that considers uncertainty in segmenting pulmonary opacifications and reduces labeling burden.

Materials And Methods: We retrospectively sourced 760 COVID-19 chest CT scans from five international centers between January and June 2020.