Lung MRI Using Inhaled Can Detect Damage

An investigative lung MRI that uses inhaled perfluoropropane gas has demonstrated an ability to identify damaged regions of the lung in patients with asthma and chronic obstructive pulmonary disease (COPD) as well as lung transplant recipients, two recently published studies reported.

The technique, called dynamic fluorine 19-MRI (19F-MRI), can enable clinicians to evaluate lung function and regional defects in the lung earlier on than existing methods, Peter Thelwall, PhD, director for the Center for In Vivo Imaging at Newcastle University, Newcastle upon Tyne, England, told Medscape Medical News.

“While this is a research tool at the moment, there is a pathway to the clinic,” Thelwall said. He noted that existing approaches to assessing lung function with MRI require using hyperpolarized 129xenon (129Xe) or hyperpolarized gas.

“Those gases require a special magnetic preparation step that has to be done on site, so you need equipment and expertise beyond the MRI scanners that we’re using, whereas we’re able to buy medical-grade perfluoropropane and have the patient inhale it. The barrier to entry of doing really good lung function imaging is a little bit lower with the approach we’re taking,” he said.

Finding ‘Patchy Ventilation’

The technique has the ability to evaluate changes in regions of the lung, what Thelwall called “patchy ventilation,” in patients with lung disease. “For example, when we scan a patient as they use their asthma medication, we can see how much of their lungs and which parts of their lungs are better able to move air in and out with each breath,” he said.

Thelwall’s group at Newcastle University published two recent studies on the 19F-MRI method: One assessing lung function in patients with asthma and COPD and the other reporting on its use in lung transplant recipients with and without chronic lung allograft dysfunction (CLAD).

“We’re hopeful we can capture subtle regional early changes with an imaging-based method that are invisible on current clinical measurement,” Thelwall said.

The asthma and COPD study found an average 19F-MRI–derived ventilation defect percentage (VDP) of 1.8% in healthy patients vs 8.3% for those with asthma and 27.2% for patients with COPD. After bronchodilator administration, the patients with asthma had a 33% reduction in average VDP, and patients with COPD had a 14% reduction.

In the study of lung transplant patients, 19F-MRI identified differences in regional ventilation with and without CLAD. The study used gas washin and washout parameters to evaluate regional lung clearance index (RLCI) and measure regional lung ventilation. The study found patients with CLAD had significant differences in RLCI between central and peripheral lung regions and wider variations in RLCI upon washin than stable patients.

Thelwall said his group is conducting another study of dynamic 19F-MRI in patients receiving radiotherapy for lung cancer. More clinical research is needed before the imaging technique can be deployed more widely in any application, he said.

Limited Applications

“We’re most interested in applications where we can genuinely make a difference,” Thelwall said of dynamic 19F-MRI. “We’re not expecting this to become a hugely broad technique that everyone gets this kind of scan, but in a few cases that we think it has a really fine value.” Lung transplant recipients are a good example of a target population, he said.

“These are people who went through a really tough medical journey, where the healthcare costs are very high, and after lung transplantation, 40% of the people die after 5 years, which is actually not a great outlook, and anything you can do in that time to manage a transplant recipient’s healthcare journey and minimize degradation of the lung, that can have a huge impact on patient outcome,” Thelwall said.

“We’re really hopeful that with the relatively small number of lung transplants done that it might actually be quite transformative in managing patients posttransplant,” he added.

Current methods for evaluating lung function, such as spirometry, are “quite blunt tools,” Thelwall said. “What we’re hopeful of is that with more detailed, granular information on how the different parts of the lung are working gives us the opportunity to see change in pathology earlier with the hope of being able to minimize damage and maximize treatment posttransplant as well as we can.”

Emerging New Tools for Detecting Lung Disease

The 19F-MRI studies research by Thelwall and associates “add considerably to the growing literature” of novel imaging approaches in lung disease, Giles Santyr, PhD, a researcher at The Hospital for Sick Children and the University of Toronto, Toronto, Ontario, Canada, whose focus is MRI for children with lung disease, told Medscape Medical News.

“MRI of tracer gases containing 19F and 129Xe breathed in the lung are anticipated to provide pulmonologists with new tools to interrogate regional disease, unlike current pulmonary function tests (eg, spirometry) that provide only an at-the-mouth measure of lung health,” Santyr said.

These advances in imaging will lead to more sensitive detection of early lung disease, greater understanding of the pathophysiology of lung disease, and development of new treatments, he added.

“Furthermore, MRI does not involve ionizing radiation characteristic of x-ray–based imaging techniques such as CT, making it ideal for use in vulnerable populations, such as children, and/or for repeated use when monitoring disease progress and treatment effect such as bronchodilators and transplant,” Santyr said.

Advances in 19F-MRI technology will make the test more widely available and supplant spirometry to an extent, he said. “It is worth noting that spirometry remains an effort-dependent test, requiring a forced exhalation, contributing to variability, especially challenging to perform in very young children,” Santyr said. “19F-MRI has the potential to overcome this limitation since it involves quiescent breathing and is therefore potentially more reproducible.”

Thelwall and Santyr had no relevant disclosures.

Richard Mark Kirkner is a medical journalist based in the Philadelphia area.