With a bold vision and a deep curiosity, electrical engineer Ruud van Sloun and his research team are on a mission to transform medical ultrasound, making it faster, more affordable, and accessible to everyone. Drawing inspiration from the remarkable efficiency of the human brain, they came up with a daring idea that once seemed impossible. But now, that "crazy plan" is starting to become reality.
Interview: Michelle Wijma
Ruud van Sloun is the kind of scientist who enjoys working on entirely new ideas that no one else has touched yet. If that fresh idea is promising but no longer novel, he's happy to hand it off to others better suited to develop it further, freeing him up to dive into a new challenge.
So around Christmas 2021, Van Sloun had taken a few weeks off to mess around with ideas freely, and ended up plopped in the middle of his living room. The floor around him was covered with dozens of neuroscience papers.
My passion is smart ultrasound - it has the potential to bring medical imaging to so many more people.
Ruud van Sloun
Van Sloun is an associate professor in the Signal Processing Systems group of the Department of Electrical Engineering. Usually, he focuses on algorithms for medical imaging, with ultrasound being a particular source of inspiration.
But not during that Christmas break. Van Sloun briefly stepped outside his field to take a deep dive into the human brain. He used his time off to learn everything about how the brain makes predictions, processes information, and makes decisions.
Medical imaging
"Can't we use these principles for medical imaging, too?" Van Sloun wondered out loud, tossing another paper onto the last bare spot on the floor.
Medical ultrasound could become much better and more accessible that way. Van Sloun dreams of portable, affordable ultrasound devices that deliver excellent image quality -one as small as a smartphone that takes images so you can confidently and reliably make medical decision with them, for every patient.
Flashlight looking for keys
"Imagine you've lost your keys," Van Sloun explains the idea behind his thinking. "You walk through a pitch-dark room with a flashlight, shining it on the spots where your keys might be hiding. Something glints in the beam. You quickly move the light back. Gotcha."
Based on the information (something glinting in the light), your brain just figured out the best next move (shining the flashlight back there). That way, you found your keys quickly without wasting energy.
Your brain predicts the future
Van Sloun explains that this idea is known as active inference in neuroscience. "Your brain constantly makes predictions about what will happen next and then does everything possible to bring those predictions to life. Without active inference, searching for your keys would look very different."
For instance, instead of focusing on where something might be, you'd start at the top left corner of the room and painstakingly sweep the flashlight down centimeter by centimeter. Then, you'd move to the right and slowly scan upwards again. Only after you've scanned the entire room would you finally notice where the keys are.
Reflecting and creating pixels
"That's exactly how an ultrasound image is formed," Van Sloun explains. "The device sends sound waves, which the body's tissues reflect. Then, the software builds the image pixel by pixel. What the machine actually 'sees' doesn't matter - the program treats every pixel in every frame as equally important."
Not only does this method waste a lot of energy on measurements that aren't informative, but the device also picks up a lot of noise and artifacts from tissues you don't want to examine.
AI growth spurt
"I thought it would be cool to apply active inference to ultrasound," says Van Sloun. But that's easier said than done. All the pixels in an ultrasound add up to an enormous number of parameters and dimensions-more zeros than you'd want to deal with. "You need exact statistical models, and that's hard in such high dimensions."
