Going With the “Flow” in Imaging the Heart

4D Flow Imaging
Two years ago, after initially being treated for an infection at a suburban hospital, 6-year-old Ariana Sohn began to experience chest pains. Diagnosed with a common type of congenital heart disease, bicuspid aortic valve, and two associated complications, she was transferred to the Heart Center at Ann & Robert H. Lurie Children’s Hospital of Chicago, the region’s largest pediatric heart center.
To develop her treatment plan, cardiologist Joshua Robinson, MD, relied on a variety of diagnostic imaging tests or “scans” to obtain highly detailed views of her heart’s anatomy and function. The specialists in the hospital’s Department of Medical Imaging and Division of Cardiology have a wide variety of technologies available for this purpose, including x-rayechocardiography, cardiac CT angiography and magnetic resonance imaging (MRI).
These scans helped Ariana’s caregivers determine the type of surgery that was most appropriate. Ultimately, she underwent successful cardiovascular-thoracic surgery to correct two problems with her aorta. Now 8, Ariana has regular follow-ups with Dr. Robinson to monitor her bicuspid aortic valve disease, which can cause the valve to narrow or develop leaks.
For children like Ariana, usually echocardiograms are performed first, and MRI and CT scans are then used as “problem solvers,” says Cynthia Rigsby, MD, Vice-Chair of Medical Imaging and physician leader of the hospital’s cardiac MRI program.
“In particular, MRI is useful in looking for structural heart disease—parts of the heart’s anatomy which are not connected as they should be,” she says. “MRI is also the gold standard for looking at heart function, allowing us to see 3D views that indicate the heart anatomy and how well it pumps blood.”
Children with complex conditions like Ariana’s may require multiple MRI scans that require them to remain still for as long as 90 minutes. A number of separate MRI “pulse sequences” need to be performed, each looking at a specific set of data, including heart structure and function, vasculature, blood flow and signs of scarring. But expecting a young child to remain still while enclosed in a 5-foot-long machine with a “tunnel” 28 inches in circumference
around them is unrealistic, says Dr. Rigsby.
“Babies and younger kids just can’t do it, which is why we have to use anesthesia when we scan them,” she says. “There are also many adults who can’t be scanned without anesthesia.”
But what if these detailed images of the heart’s blood flow could be acquired in 10 to 20 minutes or less? It would mean that many more babies and young children could undergo non-invasive MRI imaging, reducing the risks associated with repeated x-ray exposures and cardiac catheterizations.
To achieve that goal, Drs. Rigsby and Robinson and colleagues in Medical Imaging and the Heart Center have partnered with Michael Markl, PhD, a physicist at Northwestern University Feinberg School of Medicine’s Center for Translational Imaging, to collaborate on a research project using the latest MRI technology: 4D flow.
4D flow MRI technology, (essentially 3-dimensional scanning with the added parameter of time), allows for analysis of cardiovascular blood flow of the entire heart and surrounding great vessels. Thanks to its research partnership with Northwestern University and MRI manufacturer Siemens, Lurie Children’s is one of the few medical facilities in the world using4D flow MRI imaging.
Dr. Robinson notes that Ariana has benefitted from 4D flow scanning, which may indicate conditions that can lead to the formation of aneurysms and help determine the patients who would most benefit from bicuspid valve repair surgery. He says the research project would not be possible without the close collaboration between the various teams.
“Here at Lurie Children’s, we have MRI technology that can do 4D flow imaging,” he says. “We have medical specialists with knowledge about congenital heart disease. We have medical imaging specialists who understand how to implement new imaging innovations. But without the bioengineering team and physicists at Northwestern who created the 4D flow software, we would not be able to do this, because the software is not commercially
In addition to reducing scanning time, Dr. Rigsby says the use of 4D flow technology offers potential benefits.
“We do a significant amount of blood flow quantification in pediatrics, and this techniquecan be used to quantify blood flow in a vessel or chamber over time,” she says. “Now, we can look for distorted blood flow patterns and measure the velocity of the flow in the blood vessels, which can indicate various types of heart disease. We believe this distorted flow can contribute to and possibly predict cardiovascular disease individuals may have later in life. This technology has opened a window into a new world we’ve never been able to see before.”
Dr. Robinson says children treated for heart problems at Lurie Children’s also benefit from the close working relationship between the cardiology and cardiovascular surgery teams and the hospital’s cardiac imaging specialists.
“We have a symbiotic relationship that you don’t find at many pediatric medical centers, and it’s one that is important for optimal patient care,” he says. “We have established a truly collaborative program where we can leverage the strengths and expertise of each division. Things like 4D flow, MRI for infants and other technologies are available to us because Medical Imaging is using them across different areas of pediatric specialization. Access to the latest technology helps ensure that we ask the right questions when doing an exam and that we come up with the right answers. And that translates into better care for patients.”

This article was originally published in the Fall 2013 issue of Heroes magazine.