Xenon ventilation MRI in difficult asthma: initial experience in a clinical setting

Location, Location, Location: Spatial Immune-Stroma Crosstalk Drives Pathogenesis in Asthma

Chronic lung diseases including asthma are characterized by an abnormal immune response and active tissue remodeling. These changes in the architecture of the tissue are a fundamental part of the pathology across the life course of patients suffering from asthma. Current treatments aim at dampening the immune system hyperactivation, but effective drugs targeting stromal or acellular structures are still lacking. This is mainly due to the lack of a detailed understanding of the composition of the large airways and the cellular interactions taking place in this niche. We and others have revealed multiple aspects of the spatial architecture of the airway wall in response to airborne insults. In this review, we discuss four elements that we believe should be the focus of future asthma research across the life course, to increase understanding and improve therapies: (i) specialized lung niches, (ii) the 3D architecture of the epithelium, (iii) the extracellular matrix, and (iv) the vasculature. These components comprise the main stromal structures at the airway wall, each playing a key role in the development of asthma and directing the immune response. We summarize promising future directions that will enhance lung research, ultimately benefiting patients with asthma.

Hyperpolarized Xenon-129 MRI: Narrative Review of Clinical Studies, Testing, and Implementation of Advanced Pulmonary In Vivo Imaging and Its Diagnostic Applications

Hyperpolarized xenon-129 MRI (129XeMRI) has emerged as a powerful tool in the identification, evaluation, and assessment of disease endotyping and in response to interventions for a myriad of pulmonary diseases. Growing investigative efforts ranging from basic science to application in translational research have employed 129XeMRI in the evaluation of pulmonary conditions such as chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), asthma, and cystic fibrosis (CF). The novel feature of 129XeMRI is its ability to generate anatomic and physiologic readouts of the lung with resolution from the whole lung down to the lobar level. Additional advantages include being non-invasive and non-radioactive, and utilizing an inexpensive and ubiquitous noble gas as an inhalation contrast agent: xenon-129. In this review, we outline the clinical advances provided by 129XeMRI among common pulmonary diseases with high healthcare burdens in recent decades.

Ultrasensitive 129Xe Magnetic Resonance Imaging: From Clinical Monitoring to Molecular Sensing

Magnetic resonance imaging (MRI) is a cornerstone technology in clinical diagnostics and in vivo research, offering unparalleled visualization capabilities. Despite significant advancements in the past century, traditional 1H MRI still faces sensitivity limitations that hinder its further development. To overcome this challenge, hyperpolarization methods have been introduced, disrupting the thermal equilibrium of nuclear spins and leading to an increased proportion of hyperpolarized spins, thereby enhancing sensitivity by hundreds to tens of thousands of times. Among these methods, hyperpolarized (HP) 129Xe MRI, also known as ultrasensitive 129Xe MRI, stands out for achieving the highest polarization enhancement and has recently received clinical approval. It effectively tackles the challenge of weak MRI signals from low proton density in the lungs. HP 129Xe MRI is valuable for assessing structural and functional changes in lung physiology during pulmonary disease progression, tracking cells, and detecting target molecules at pico-molar concentrations. This review summarizes recent developments in HP 129Xe MRI, including its physical principles, manufacturing methods, in vivo characteristics, and diverse applications in biomedical, chemical, and material sciences. In addition, it carefully discusses potential technical improvements and future prospects for enhancing its utility in these fields, further establishing HP 129Xe MRI's importance in advancing medical imaging and research.

Cystic Fibrosis or asthma? Discerning dyspnea with hyperpolarizaed xenon gas magnetic resonance imaging

Hyperpolarized Xenon MRI (HPG MRI) has been studied for its potential use in assessing lung function in patients with cystic fibrosis (CF) and in patients with asthma. We present a case of a man with overlapping cystic fibrosis and allergic asthma with severe obstructive lung disease in which spirometry and computed topography (CT) imaging was unable to determine the primary cause for his uncontrolled symptoms. HPG MRI was used to guide a tissue biopsy and determine the primary driver to be allergic asthma. After starting targeted therapy for severe asthma, his symptoms have greatly improved.

Histopathological, Cytological and Radiological Correlations in Allergy and Public Health Concerns: A Comprehensive Review

Allergies represent a significant and growing public health concern, affecting millions worldwide and burdening healthcare systems substantially. Accurate diagnosis and understanding of allergy is crucial for effective management and treatment. This review aims to explore the historical evolution, current advances, and prospects of histopathological and cytological techniques in allergy diagnosis, highlighting their crucial role in modern medicine. Major biomedical, public health, and imaging databases such as PubMed, Scopus, Web of Science, and EMBASE were used. The search strategy used include specific keywords and Medical Subject Headings (MeSH) terms related to histopathology, cytology, radiology, allergic diseases, and public health. Histopathological and cytological studies play a pivotal role in elucidating the underlying mechanisms of allergies, offering insights into the cellular and tissue-level changes associated with allergic responses. Histopathology reveals characteristic features such as inflammation, tissue remodeling, and the presence of specific immune cells like eosinophils and mast cells. Cytological analysis can detect cellular changes and abnormalities at a finer scale, providing a complementary perspective to histopathological findings. The correlation between histopathological and cytological findings is critical for achieving accurate and reliable diagnoses. Combined histopathological and cytological studies can reveal the extent of airway inflammation, epithelial damage, and immune cell infiltration, providing a robust basis for clinical decision-making. Recent advancements in diagnostic techniques have further revolutionized the field of allergy diagnosis. These technologies offer increased accuracy, speed, and reproducibility, making them invaluable in both clinical and research settings. Despite these advancements, several challenges and limitations persist. By integrating tissue-level and cellular-level analyses, clinicians can achieve more accurate diagnoses, tailor treatments to individual patients, and ultimately improve the quality of care for those suffering from allergies. In conclusion, histopathological and cytological correlation in allergy diagnosis provides a comprehensive framework for understanding and managing allergic conditions.

Ventilation Heterogeneity Is a Treatable Trait in Severe Asthma

BACKGROUND

Ventilation heterogeneity (VH) is a feature of asthma and indicates small airway disease. Nuclear imaging methods assess VH, which can facilitate clinical diagnosis and further our understanding of disease aetiology.

OBJECTIVE

We sought to assess VH in severe eosinophilic asthma (SEA) using ventilation/perfusion single-photon emission computed tomography (V/P SPECT), and to assess its use as an objective test of the effect of biologic treatment for ventilation defects in SEA.

METHODS

Adults (≥18 y) with severe asthma were recruited to participate in a cross-sectional observational study. Participants underwent a clinical assessment and V/P SPECT CT using Technegas as the ventilation agent. Measures were repeated for a nested before-after treatment study in people with SEA commencing biologics.

RESULTS

A total of 62 participants with severe asthma were recruited. From this, 38 participants with SEA were included in the before-after study. The VH was associated with clinical variables such as lung function impairment and significantly improved after monoclonal antibody treatment in the severe asthma group. The changes in VH correlated with change in post bronchodilator forced expiratory volume in 1 second (FEV1) %predicted (r = -0.503; P = .001) and post bronchodilator FEV1/FVC (forced vital capacity) (r = -0.415; P = .01).

CONCLUSIONS

The VH is clinically significant, measurable, and treatable, which establishes VH as a treatable trait in severe asthma.

Specific Ventilation in Severe Asthma Evaluated with Noncontrast Tidal Breathing 1H MRI

Purpose To determine if proton (1H) MRI-derived specific ventilation is responsive to bronchodilator (BD) therapy and associated with clinical biomarkers of type 2 airway inflammation and airways dysfunction in severe asthma. Materials and Methods In this prospective study, 27 participants with severe asthma (mean age, 52 years ± 9 [SD]; 17 female, 10 male) and seven healthy controls (mean age, 47 years ± 16; five female, two male), recruited between 2018 and 2021, underwent same-day spirometry, respiratory oscillometry, and tidal breathing 1H MRI. Participants with severe asthma underwent all assessments before and after BD therapy, and type 2 airway inflammatory biomarkers were determined (blood eosinophil count, sputum eosinophil percentage, sputum eosinophil-free granules, and fraction of exhaled nitric oxide) to generate a cumulative type 2 biomarker score. Specific ventilation was derived from tidal breathing 1H MRI and its response to BD therapy, and relationships with biomarkers of type 2 airway inflammation and airway dysfunction were evaluated. Results Mean MRI specific ventilation improved with BD inhalation (from 0.07 ± 0.04 to 0.11 ± 0.04, P < .001). Post-BD MRI specific ventilation (P = .046) and post-BD change in MRI specific ventilation (P = .006) were greater in participants with asthma with type 2 low biomarkers compared with participants with type 2 high biomarkers of airway inflammation. Post-BD change in MRI specific ventilation was correlated with change in forced expiratory volume in 1 second (r = 0.40, P = .04), resistance at 5 Hz (r = -0.50, P = .01), resistance at 19 Hz (r = -0.42, P = .01), reactance area (r = -0.54, P < .01), and reactance at 5 Hz (r = 0.48, P = .01). Conclusion Specific ventilation evaluated with tidal breathing 1H MRI was responsive to BD therapy and was associated with clinical biomarkers of airways disease in participants with severe asthma. Keywords: MRI, Severe Asthma, Ventilation, Type 2 Inflammation Supplemental material is available for this article. © RSNA, 2023 See also the commentary by Moore and Chandarana in this issue.

Detection of Small Airway Dysfunction in Asthmatic Patients by Spirometry and Impulse Oscillometry System

BACKGROUND

There is no gold standard in diagnosing SAD. Indicators of SAD are considered: (a) a value <65% of predicted values of two of three measures, FEF25-75, FEF50 e FEF75 (FEF+); (b) a value of FEV3/FEV6 < LLN (FEV3/FEV6+); (c) an IOS value of R5-R20 >0.07 kPa·s·L-1 (R5-R20+).

AIM AND OBJECTIVES

The aim of the study was to ascertain, in asthmatic patients, whether spirometry and IOS indicators agree in detecting SAD. We also assessed the relationship between spirometry and IOS indicators and clinical features of asthma.

METHODS

We prospectively recruited adult asthmatic patients. Anthropometric and clinical characteristics were recorded. All patients performed spirometry and IOS tests.

RESULTS

We enrolled 301 asthmatic patients (179 females; mean age 50 ± 16 years) with normal to moderately severe degree of airway obstruction; 91% were non-smokers, 74% were atopic, 28% had an exacerbation in the previous year, and 18% had a poor asthma control by ACT. SAD was diagnosed in 62% of patients through FEF+, in 40% through FEV3/FEV6+ and in 41% through R5-R20+. κ values were 0.49 between FEF+ and FEV3/FEV6+, 0.20 between FEF+ and R5-R20+, 0.07 between FEV3/FEV6+ and R5-R20+. R5-R20+ but not FEF+ and FEV3/FEV6+ was significantly associated with ACT score (p < 0.05).

CONCLUSIONS

Our study shows that in mild to moderately severe asthmatic patients, spirometry and IOS indicators are complementary in diagnosing SAD. Additionally, IOS indicator, but not spirometry ones, was related to asthma control.

Imaging-derived biomarkers in Asthma: Current status and future perspectives

Asthma is a common disorder affecting around 315 million individuals worldwide. The heterogeneity of asthma is becoming increasingly important in the era of personalized treatment and response assessment. Several radiological imaging modalities are available in asthma including chest x-ray, computed tomography (CT) and magnetic resonance imaging (MRI) scanning. In addition to qualitative imaging, quantitative imaging could play an important role in asthma imaging to identify phenotypes with distinct disease course and response to therapy, including biologics. MRI in asthma is mainly performed in research settings given cost, technical challenges, and there is a need for standardization. Imaging analysis applications of artificial intelligence (AI) to subclassify asthma using image analysis have demonstrated initial feasibility, though additional work is necessary to inform the role of AI in clinical practice.

Functional imaging in asthma and COPD: design of the NOVELTY ADPro substudy

The NOVEL observational longiTudinal studY (NOVELTY; ClinicalTrials.gov identifier NCT02760329) is a global, prospective, observational study of ∼12 000 patients with a diagnosis of asthma and/or COPD. Here, we describe the design of the Advanced Diagnostic Profiling (ADPro) substudy of NOVELTY being conducted in a subset of ∼180 patients recruited from two primary care sites in York, UK. ADPro is employing a combination of novel functional imaging and physiological and metabolic modalities to explore structural and functional changes in the lungs, and their association with different phenotypes and endotypes. Patients participating in the ADPro substudy will attend two visits at the University of Sheffield, UK, 12±2 months apart, at which they will undergo imaging and physiological lung function testing. The primary end-points are the distributions of whole lung functional and morphological measurements assessed with xenon-129 magnetic resonance imaging, including ventilation, gas transfer and airway microstructural indices. Physiological assessments of pulmonary function include spirometry, bronchodilator reversibility, static lung volumes via body plethysmography, transfer factor of the lung for carbon monoxide, multiple-breath nitrogen washout and airway oscillometry. Fractional exhaled nitric oxide will be measured as a marker of type-2 airways inflammation. Regional and global assessment of lung function using these techniques will enable more precise phenotyping of patients with physician-assigned asthma and/or COPD. These techniques will be assessed for their sensitivity to markers of early disease progression.

Imaging Regional Airway Involvement of Asthma: Heterogeneity in Ventilation, Mucus Plugs and Remodeling

The imaging of asthma using chest computed tomography (CT) is well-established (Jarjour et al., Am J Respir Crit Care Med 185(4):356-62, 2012; Castro et al., J Allergy Clin Immunol 128:467-78, 2011). Moreover, recent advances in functional imaging of the lungs with advanced computer analysis of both CT and magnetic resonance images (MRI) of the lungs have begun to play a role in quantifying regional obstruction. Specifically, quantitative measurements of the airways for bronchial wall thickening, luminal narrowing and distortion, the amount of mucus plugging, parenchymal density, and ventilation defects that could contribute to the patient's disease course are instructive for the entire care team. In this chapter, we will review common imaging methods and findings that relate to the heterogeneity of asthma. This information can help to guide treatment decisions. We will discuss mucous plugging, quantitative assessment of bronchial wall thickening, delta lumen phenomenon, parenchymal low-density lung on CT, and ventilation defect percentage on MRI as metrics for assessing regional ventilatory dysfunction.

Computed tomography findings in bronchial asthma: quantification of air trapping and correlation with pulmonary function tests

Background

High-resolution computed tomography (HRCT) scans can help identify subsets of asthma patients who show rapid decline in lung function.

Purpose

To evaluate high-resolution computed tomography (HRCT) findings in adult patients with asthma, obtain quantitative measurements of air trapping on expiratory scans, and correlate the findings with pulmonary function tests (PFTs).

Material and Methods

Thirty adults with asthma with persistent-mild, persistent-moderate, and persistent-severe categories as per standard clinical guidelines were evaluated with inspiratory and expiratory HRCT for various imaging features of bronchial asthma. Expiratory HRCT scan were used to quantify degree of air-trapping, and their values quantified as “pixel index,” using a special “density' mask” software. Complete spirometry and body plethysmography were performed on each patient within 0–2 days of HRCT scans. HRCT findings were correlated with the clinical severity groups and the CT pixel indices (PI) were correlated with the PFT results using correlation coefficients and linear regression analysis.

Results

The inspiratory CT findings did not correlate with increase in disease severity. Expiratory scans accurately quantified areas of air trapping. CT-PI correlated well with PFT values indicative of airway obstruction and airflow limitation, which helped differentiate patients with asthma with increasing severity from those with milder forms of the disease.

Conclusion

Expiratory thin-section CT is a useful objective method to quantify air-trapping in people with asthma. The air-trapping score measured in “pixel indices” correlates well with PFT results and can successfully identify patients with severe asthma. Further studies are needed to confirm if this parameter can serve as a potential marker for airway remodeling and declining lung function.