Academic Background and Problem Statement

Respiratory diseases impose a significant burden on healthcare systems globally. Although existing pulmonary function tests (such as conventional spirometry) aid in disease diagnosis and monitoring, these methods are relatively insensitive in detecting early-stage diseases and cannot provide information on regional lung function heterogeneity. This limitation means that localized pathologies, such as regional airway disease and ventilation impairment, may be masked by global spirometric measurements. Current clinical imaging modalities (e.g., chest radiography, CT, and PET) offer spatially localized information but rely on ionizing radiation, which poses a cumulative risk of malignancy and limits their use in longitudinal evaluations.

Lung MRI (magnetic resonance imaging) has lagged behind MRI of other organs due to challenges posed by the low water density and magnetic field inhomogeneities caused by the ubiquitous air-water interfaces in the lungs. However, advancements in novel MRI techniques have overcome many of these barriers, enabling quantitative assessment of regional lung structure and function. These technological improvements hold promise for enhancing early disease detection and monitoring therapeutic interventions.

Research Objective

This study aimed to evaluate regional lung ventilation properties using fluorine-19 (19F) MRI of inhaled perfluoropropane in participants with asthma, chronic obstructive pulmonary disease (COPD), and healthy individuals. Additionally, the study sought to quantitatively assess the bronchodilator response in participants with respiratory diseases.

Research Team and Publication Information

The study was conducted by a research team from Newcastle University and the University of Sheffield in the UK. The primary authors include Benjamin J. Pippard, Mary A. Neal, and others. The research was published in December 2024 in the journal Radiology, under the title Assessing Lung Ventilation and Bronchodilator Response in Asthma and Chronic Obstructive Pulmonary Disease with 19F MRI.

Research Methods and Procedures

Study Design and Sample

This prospective, dual-center study recruited participants with asthma and COPD between July 2019 and September 2022, and healthy participants between May 2018 and June 2019. All participants underwent conventional spirometry, proton MRI, and 19F MRI following inhalation of a 79% perfluoropropane and 21% oxygen gas mixture. For participants with asthma or COPD, spirometric and MRI measurements were repeated after the administration of nebulized salbutamol. The ventilation defect percentage (VDP) was calculated from the perfluoropropane distribution, and linear mixed-effects models were used to assess differences in VDP between participant groups and before and after bronchodilator administration.

Study Procedures

1. Participant Recruitment and Screening: Healthy participants were recruited from universities and healthcare institutions in Newcastle and Sheffield, while asthma and COPD patients were recruited from respiratory outpatient clinics at two hospitals. All participants provided written informed consent.
2. Spirometry: Conducted by experienced respiratory clinicians using CareFusion spirometers. For asthma and COPD patients, spirometry was performed immediately before MRI and 20 minutes after nebulized salbutamol administration.
3. MRI Examination: Performed using 3T MRI scanners with participants in the supine position. Participants inhaled the perfluoropropane gas mixture and underwent three-dimensional 19F MRI scans during a breath-hold.
4. Image Analysis: MRI scans were analyzed using MATLAB and in-house software to calculate VDP values.

Key Findings

The study evaluated 35 participants with asthma (mean age 50 years), 21 participants with COPD (mean age 69 years), and 38 healthy participants (mean age 41 years). The results showed that 19F MRI-derived VDP was significantly higher in participants with COPD and asthma compared to healthy participants (geometric means of 27.2%, 8.3%, and 1.8%, respectively). After bronchodilator administration, VDP decreased by 33% in participants with asthma (from 8.3% to 5.6%) and by 14% in participants with COPD (from 27.2% to 23.3%).

Conclusions and Significance

The study demonstrated that 19F MRI of inhaled perfluoropropane is sensitive to changes in regional ventilation properties associated with lung disease and can quantify changes following bronchodilator therapy. This technique does not require hyperpolarization equipment, is cost-effective, and has significant potential for clinical applications, particularly in early disease diagnosis, disease progression monitoring, and treatment efficacy assessment.

Research Highlights

1. Innovation: This study is the first to apply 19F MRI technology to assess regional ventilation in asthma and COPD patients, demonstrating its feasibility without hyperpolarization.
2. Sensitivity: 19F MRI-derived VDP showed higher sensitivity in detecting early-stage disease and treatment response compared to conventional spirometry.
3. Clinical Potential: The technique does not require complex hyperpolarization equipment and is cost-effective, making it suitable for widespread clinical use.

Additional Valuable Information

The study also explored the potential of 19F MRI in dynamically assessing lung gas distribution, particularly through the wash-in and washout rates of perfluoropropane to quantify regional ventilation heterogeneity. Future research could further validate the application of this technology in early diagnosis, disease progression monitoring, and treatment efficacy assessment.