The future of cardiac MRI: “3-D cine”
Andrew Powell, MD, and physicist Mehdi Hedjazi Moghari, PhD, are working together on a new MRI-based technology that can produce beating 3-D images of the heart. Their technique allows cardiologists and cardiac surgeons to see a patient’s heart from any angle, as well as observe its movement throughout the entire cardiac cycle.
The technology simplifies the cardiac MRI process for both doctor and patient and provides a much richer data set for discerning diagnoses.
Moghari and Powell refer to their technology as “3-D cine,” because the image data appears as a 3-D block anatomy that moves as the heart beats.
“3-D cine is an important technical development,” says Powell. “It’s much easier to appreciate complex anatomy when you can see it in 3-D, instead of integrating lots of 2-D slices in your mind.”
Simplified data collection, easier for the patient
A standard cardiac MRI includes multiple 2-D image slices stacked next to each other that must be carefully positioned, based on a patient’s particular anatomy. Planning the location of the slices requires a highly knowledgeable operator and takes time.
“In our alternative 3-D cine technique, the whole chest is imaged as a 3-D block so there is no need to tailor the position of the images based on a patient’s condition," says Powell. "This leads to easier, faster planning.”
Another challenge with the standard 2-D cine cardiac MRI approach is that patients must hold their breath while the picture is being taken, because any chest movement will blur the picture. A typical patient must hold his or her breath for 10–15 seconds a total of 15–20 times. Young children, and those who are quite ill, often find this challenging, and the process can take a while. With the 3-D cine approach, patients can just breathe normally. “We track the patient’s breathing motion and only collect data during expiration, when the patient is breathing out,” explains Moghari. “The technical aspects of this are continually being refined.”
It takes less than 10 minutes to acquire 3-D cine images of the chest. That block of data is then loaded onto a specialized viewing computer that allows doctors to view the moving heart and blood vessels from any perspective by cutting into the block at various locations and angles. It can even be rendered in 3-D with lighting and shadows so it looks real. “In the end, we get much more valuable, richer data,” says Powell.
“One downside to the technique,” he adds, “is that, unlike 2-D cine, 3-D cine requires the use of intravenous contrast.”
Testing it out
In 2016, Powell and Moghari tested their 3-D cine MRI technique on 30 Heart Center patients with varying ages and conditions. “We continue to make technical refinements to find the best balance of speed versus image quality,” Powell notes. “We’re also validating the 3-D cine data by comparing measurements to those from standard 2-D cine to make sure they match,” says Moghari.
“This whole 3-D cine development project is the result of a carefully planned, step-by-step process,” Powell emphasizes.
First, the team worked on producing clear pictures without breath-holding for 2-D cine, then 3-D still images and now 3-D moving images. At each step, their work has been peer-reviewed and published.
Several more development steps are needed before 3-D cine MRI technology is ready for widespread use. Current commercially available tools for measuring the size of the heart are built for 2-D images; Powell and Moghari are working with several companies to develop software suitable for rapid measurements in 3-D.
Moghari also notes that their technique was designed specifically for a Philips MRI scanner; “If another center uses Philips too, they can also use this technique,” he says. “But it would have to be adapted for a different scanner manufacturer.”
In the future, Moghari and Powell plan to take a similar approach to image blood flow in 3-D. They will develop techniques to combine the anatomic and blood-flow data, as well as user-friendly visualization and analysis tools. Polina Golland, MD, and Danielle Pace, MD at MIT’s CSAIL lab are collaborating in this effort. The result will be a powerful tool for understanding the function of the cardiovascular system and making treatment recommendations for patients with congenital heart disease.