Breathing Xenon Into MRI Reveals Hidden Lung Damage in a Teenager

When a 14-year-old girl arrived at Cincinnati Children’s Hospital Medical Center with a persistent dry cough that had lingered for two years, her medical history held the first clue to what was wrong. Six years earlier, she had undergone an allogeneic hematopoietic stem cell transplantation to treat acute myeloid leukemia, a procedure in which donor stem cells are infused to rebuild the bone marrow and blood system after intensive chemotherapy. While such transplants can be lifesaving for children with leukemia, they carry a well-known risk of late complications, and one of the most feared among them is chronic lung injury. The teenager’s symptoms, combined with the results of pulmonary function testing, pointed clinicians toward exactly that kind of complication, and a cutting-edge imaging technique was about to show her damaged lungs in a way conventional scans never could.

Pulmonary function testing revealed a severe obstructive defect, with her forced expiratory volume in one second, or FEV1, measuring only 40 percent of the predicted value for her age and size. FEV1 is one of the most widely used benchmarks in respiratory medicine: the patient takes a maximal breath and then exhales as hard and fast as possible, and the machine records how much air leaves the lungs in the first second. A healthy child typically clears the large majority of their vital capacity in that window, so a value of 40 percent signaled that air was having trouble escaping her lungs, the hallmark of an obstruction in the small airways. In children, such a pattern raises particular concern for bronchiolitis obliterans, a disease in which inflammation and fibrosis progressively narrow and destroy the bronchioles, the tiniest branches of the airway tree.

Bronchiolitis obliterans after stem cell transplantation is generally understood to be a manifestation of chronic graft-versus-host disease, the process by which donor immune cells recognize the recipient’s tissues as foreign and attack them. In the lungs, this attack targets the small airways, producing scarring that is essentially irreversible once established. The condition is a leading cause of late non-relapse mortality in long-term transplant survivors, which makes early detection and careful monitoring critically important. Yet the disease is notoriously difficult to assess precisely, because the small airways where the damage occurs are far below the resolution of even the best conventional imaging, and the functional consequences are scattered unevenly across the lung in a patchwork of affected and spared regions.

To visualize that patchwork, the clinical team turned to expiratory coronal chest computed tomography. The CT images demonstrated diffuse mosaic attenuation, a pattern in which the lung parenchyma appears as a patchwork of darker and lighter regions, like a quilt of alternating density. In the context of small airway disease, the darker areas represent air trapping: regions of lung where obstructed bronchioles prevent air from emptying during exhalation, leaving those territories abnormally inflated and under-perfused. Mosaic attenuation on an expiratory scan is a classic radiological signature of air trapping and supported the diagnosis of bronchiolitis obliterans in this patient. But while CT can show that some regions are denser and others less dense than they should be, it cannot directly measure whether those regions are actually participating in ventilation, and it delivers a dose of ionizing radiation, a meaningful consideration in a child who will need repeated surveillance over many years.

That is where hyperpolarized xenon-129 MRI enters the picture, and it represents one of the most striking technical achievements in modern medical imaging. Ordinary MRI excels at imaging soft tissue rich in hydrogen nuclei, but it is nearly blind to the air inside the lungs, because air contains almost no hydrogen and produces essentially no signal. The solution is to image a gas instead, and to boost that gas’s signal to extraordinary levels through a process called hyperpolarization. Xenon-129, a stable, non-radioactive isotope of the noble gas xenon, is paired with rubidium vapor and exposed to laser light in a process known as spin-exchange optical pumping. This transfers angular momentum from the laser-polarized rubidium atoms to the xenon nuclei, aligning their nuclear spins far beyond what is possible at normal thermal equilibrium, sometimes amplifying the available MRI signal by tens of thousands of times.

Once hyperpolarized, the xenon gas is inhaled by the patient inside the MR scanner, and because the nuclei are polarized, the gas itself becomes visible to the MRI system. In this case, the xenon-129 was inhaled and ventilation images were acquired during a single breath hold, meaning the entire three-dimensional picture of where the gas reached within the lungs was captured in the few seconds the child could comfortably hold her breath. This is a crucial practical advantage in pediatric imaging, where long scan times and repeated breath holds are often impossible for young patients to tolerate. Regions of the lung that received the gas appear as high signal on the images, while regions that the gas could not reach, because of obstructed or destroyed airways, appear as low signal, or ventilation defects. The result is a direct, functional map of breathing, region by region, rather than an inference drawn from density patterns.

The raw ventilation images were then processed into a color map, translating signal intensity into an intuitive visual display of lung function. In the published images, the areas of decreased attenuation on the CT scan corresponded closely to the ventilation defects highlighted on the xenon-129 MRI, providing a compelling side-by-side demonstration that the two modalities were capturing the same underlying pathology. More importantly, the technique allowed the team to calculate a single quantitative metric: the ventilation defect percentage, or VDP, which expresses the proportion of total lung volume showing impaired ventilation. In this patient, the VDP was 36 percent, a dramatic figure compared with the normal threshold of less than 5 percent. In other words, more than a third of her lung volume was effectively silent on the ventilation map, unable to participate in gas exchange through the damaged airways.

The significance of a reproducible number like VDP is difficult to overstate for a disease that has long been monitored indirectly. FEV1, the workhorse of pulmonary function testing, reflects the summed behavior of millions of airways and can be influenced by the patient’s effort and cooperation, which is a particular challenge in young children. It also cannot say anything about where in the lungs the obstruction is concentrated or how the pattern of disease evolves over time. Xenon-129 MRI, by contrast, offers a spatially resolved, quantitative, and radiation-free measure that can be repeated at regular intervals. For a teenager facing decades of surveillance after stem cell transplantation, the ability to track her ventilation defect percentage over time, and to see whether it worsens, stabilizes, or improves in response to treatment, represents a fundamentally more informative way to manage her disease.

The case, published in the journal Pediatric Radiology by Tyler Obermark, Kathryn Donohue, Elizabeth Kramer, Laura Walkup, and Cara Morin of the University of Cincinnati College of Medicine and Cincinnati Children’s Hospital Medical Center, is presented as a demonstration of what hyperpolarized gas imaging can offer in pediatric practice. The authors note that xenon-129 MRI provides a reproducible quantitative measure for longitudinal surveillance and assessment of treatment response in children with bronchiolitis obliterans. The report is open access, allowing clinicians and researchers anywhere to examine the images and methods in full detail, and the work reflects a broader movement to bring hyperpolarized gas MRI from the research laboratory into routine clinical care for pediatric lung disease.

For the field of pediatric pulmonology, the implications extend well beyond a single patient. Bronchiolitis obliterans is not limited to stem cell transplant recipients; it can also follow severe viral infections, including adenovirus and other pathogens, and it shares features with the small airway damage seen in chronic obstructive pulmonary disease in adults. A technique that maps ventilation directly, quantifies it precisely, and avoids ionizing radiation could reshape how all of these conditions are diagnosed and followed in children. The image of a teenager’s lungs, painted in color by a magnetically aligned noble gas she breathed in for a single breath hold, captures a moment when physics, chemistry, and clinical medicine converge to make the invisible visible, and to give clinicians a number they can actually act on in the long fight to preserve a child’s breathing.

Subject of Research: Hyperpolarized xenon-129 MRI ventilation imaging for assessing bronchiolitis obliterans after pediatric stem cell transplantation

Article Title: Xenon-129 ventilation imaging in pediatric bronchiolitis obliterans patient

Article References: Obermark, T., Donohoe, K., Kramer, E., Walkup, L., & Morin, C. (2026). Xenon-129 ventilation imaging in pediatric bronchiolitis obliterans patient. Pediatric Radiology. https://doi.org/10.1007/s00247-026-06799-5

Image Credits: AI Generated

DOI: 10.1007/s00247-026-06799-5

Keywords: xenon-129 MRI, hyperpolarized gas imaging, bronchiolitis obliterans, pediatric radiology, stem cell transplantation, ventilation defects, FEV1, air trapping, chronic graft-versus-host disease, lung imaging, ventilation defect percentage, Xenon-129