As of now, there's no standard form of imaging for both the structure and function of the lungs. A CT scan can tell you, say, if a patient with cystic fibrosis might have air trapping, and where. But it also exposes the patient to about two years of background radiation, and it can't tell you anything about airflow or capacity. Spirometry can do that, but it can't tell you much about blockage. And if the patient is younger than about 6 years old, it can't tell you much of anything, at least not accurately.
"You could do pulmonary MRI, but that's a lot of equipment, people and computing power, and it's expensive," says Emily DeBoer, MD, a pediatric pulmonologist at Children's Hospital Colorado specializing in biomarkers of lung disease. "Most centers don't do it. And most kids under 6 still can't tolerate sitting still that long."
"We get worried about doing frequent CTs on younger children," says pediatric pulmonologist Jordana Hoppe, MD. "But we need way to get information to tell us how we're doing treating kids with cystic fibrosis. Are they getting better? Is this or that treatment making a difference? There aren't a lot of options to understand lung disease in the preschool-age range."
That's about to change.
Mapping the lungs through conductivity
Different tissues conduct electricity differently. Blood is a great conductor. Bone, not so much. Air-infused lung tissue, even less.
"As current flows through tissues, it takes the path of least resistance," says Jennifer Mueller, PhD, Professor of Mathematics and Biomedical Engineering at Colorado State University. "The idea is that we can measure that and use that data to map what's inside the body."
As an idea, electrical impedance tomography, or EIT, has been around for a long time. Electrical engineer John G. Webster first detailed it in 1978. Computer scientists and medical physicists produced the first working cross-section of a human forearm in 1983. Now, Dr. Mueller is collaborating with Dr. DeBoer and others at Children's Colorado to develop that technology for the clinical space.
"The way it works is that you have these measurements and you're trying to figure out what causes them, to find the cause of an effect," says Dr. Mueller. "That's called inverse problem. And it's a difficult one."
The mathematical challenge of electrical impedance tomography