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Elliot McVeigh, director biomedical engineering, on capturing MRI images of a beating heart:
How did you become interested in magnetic resonance imaging (MRI)?
MCVEIGH: When I was a physics undergraduate, I read an article in the May 1982 Scientific American on how MRI worked, and I thought it was the coolest thing I’d ever seen. Soon after, I started calling around looking for places to go where I could do MRI research. I went to work at the Ontario Cancer Institute as a summer student and liked it so much that I decided to pursue a graduate degree there. I got my Ph.D. in about three and a half years because I was so absorbed in the research, that it was essentially all I did.
Immediately after that I came to Hopkins as a radiology instructor to work with Elias Zerhouni on cardiac MRI. Imaging the heart was really exciting to me because it was very hard to do at the time, and we were one of the only groups in the world that figured out how to do it well.
What is the medical value of being able to see images of the heart?
MCVEIGH: People with heart disease or a past incidence of a heart attack accumulate damaged tissue in their heart that affects how the heart beats. This damaged tissue puts these people at risk for sudden cardiac death.
Our collaborators in the cardiology department, Joao Lima and Kathy Wu, image patients’ hearts before installing cardioverter defibrillators; these are devices that shock the heart to correct extremely irregular heartbeats. Their work has generated a large clinical data set of patients that we use to predict which patterns of damaged tissue are more likely to cause death. Perhaps one day this research will lead to better diagnostics for identifying those patients at highest risk for sudden cardiac death.
Our collaborator in Biomedical Engineering, Natalia Trayanova, is one of the few people in the world that can take an image of a whole heart and design a computer program that simulates that particular heart’s electrical activity. Using these simulations, she predicts what factors cause the heart to have abnormal electrical behavior.
What are the challenges of imaging a heart with MRI?
MCVEIGH: Any movement during the exposure makes the image blurry. The main problem with imaging the heart is that it moves, making a clear picture difficult to get. Nowadays, MRI machines are more advanced and can take faster images (up to 20 per second), but these images aren’t high enough resolution to see anything in any great detail.
How have you improved upon the latest technology to image the heart?
MCVEIGH: We can use an MRI technique that only looks at a small field of view and takes a set of pictures of the heart when it is in the same general location, and then we assemble the data later. Some people manually use a bellows to measure the patient’s breathing which changes the heart’s position. This is used in conjunction with an electrocardiogram that shows us the electrical activity of the heart which can be used to measure which phase the heartbeat is in.
We can take images fast enough that we get a low-resolution image that can tell us at what position the heart is globally. Then, we line up many low-resolution images that show the path that the heart takes as it moves along during breathing and beating – sort of like a cartoon flip-book. Then we take data from the points along this trajectory that are in the same places. There is a lot of math and programming that goes into assembling a clear image from all this data.
Are you developing new technological advancements in MRI?
MCVEIGH: Researchers, particularly biotech companies, are now interested in developing live MRI imagers to see changes occurring in the body in real time. For example, if doctors inject a drug into a patient, they can see where it goes after they’ve injected it.
We actually built a live MRI imager in my lab and used it to detect stem cells as they were injected into the heart of an animal. The physician looked at a screen and in real time could see the beating heart to know where to inject the cells.
You can’t do this kind of live imaging with an X-ray CT scanner because of the radiation, but as long as there is no magnetic metal used on the patient, MRI imaging is a fairly safe option. I predict that these live imaging techniques will become a lot more prevalent as soon as the technology advances.
--Interviewed by Vanessa McMains
Elliot McVeigh on imaging the heart to predict disease: