Ultrashort echo-time, hyperpolarized gas MRI methods make it safer to assess new
by Tim Bonfield
Jason Woods, PhD, is a leader in developing safer lung imaging methods for children.
Two teens with cystic fibrosis (CF) blow into spirometers. Both tests come back with 100 percent scores on a key measure of lung capacity, the FEV1 (forced expiratory volume in one second). Both patients appear to be doing well.
A closer look at the patients’ lungs, using a new approach called ultrashort echo-time magnetic resonance imaging (UTE MRI), reveals striking structural differences in the lungs. Meanwhile, an MRI scan using hyperpolarized gas as a contrast agent reveals clear differences in lung function. Despite having similar FEV1 results, these MRI tests reveal that one patient is doing much worse than the other, and likely needs prompt intervention.
As recently as a few years ago, detecting such differences in lung function for children and young adults with cystic fibrosis had minimal practical value because the menu of treatment interventions was so limited. Now, however, two new cystic fibrosis drugs have reached the market and several more are in development. Now, clinicians need to decide exactly when these exciting-but-expensive new treatments should be employed.
“We are right on the cusp of individualized medicine for cystic fibrosis. As new pharmaceutical agents continue to be developed, it becomes critical to obtain detailed data to assess which therapies are working best for particular patients,” says Jason Woods, PhD, Director of the Center for Pulmonary Imaging Research at Cincinnati Children’s. “The FEV1 is a standard clinical test, but results can be widely variable.”
Another well-established imaging method — CT scanning — also can provide useful, detailed data on lung function. However, a single CT scan delivers as much as 200 times more radiation than a standard chest X-ray. While the risks of triggering cancer later in life are small, those risks are real enough to make clinicians reluctant to use CT scanning as a frequent surveillance tool, especially for the youngest CF patients.
These images demonstrate the results of UTE MRI (top), hyperpolarized gas MRI (middle), and a colorized image that combines both results (bottom).
Enter the MRI. With improved techniques, MRI scanning can produce lung imagery that rivals the quality of a CT scan. In fact, UTE MRI in particular can be a safe and effective tool for evaluating lung health in patients as young as six months. David Roach, PhD, (a fellow in Woods’ lab) recently presented pilot study data about UTE MRI in Denver at the annual meeting of the American Thoracic Society. The findings also were published May 1, 2015, in the abstract issue of the American Journal of Respiratory and Critical Care Medicine.
Woods reports that UTE MRI can assess bronchiectasis, bronchial wall thickening, parenchymal opacity and air trapping. “We show that MRI can detect the same abnormalities that can be detected with CT,” he says.
The next steps for wider adoption of UTE MRI include larger, multicenter clinical trials to confirm the pilot study findings.
Meanwhile, Woods continues his work as a leading expert in the use of hyperpolarized-gas MRI. Cincinnati Children’s is participating in stage II clinical trials to evaluate the use of Xenon-129 MRI scanning for cystic fibrosis patients. The noble gas can be tracked during breathing, which provides much more information about lung function than can be obtained from the FEV1 test.
Initial results from a study of hyperpolarized-gas MRI in CF patients will be presented by his group at the International Workshop on Pulmonary Functional Imaging in Edinburgh, Scotland, and at the North American Cystic Fibrosis Conference in Phoenix.
Woods sees the UTE and hyperpolarized-gas methods as complementary tools that do not pose the radiation risk of CT scanning. Within the next several years, he predicts that new MRI techniques will be used well beyond the cystic fibrosis population to evaluate lung function and development in premature infants and other children with rare lung diseases.
Also, hospitals will not need to make major investments to adopt these technologies, Woods says. Many clinical MRI scanners already have the software needed to support UTE MRI. The hyperpolarized-gas method does require equipment upgrades, but not entirely new scanners.