“I wanted to save lives”
At 14, Bell enrolled in the highly selective Brooklyn Technical High School, where she divided her time between academics and a newfound interest in running; she was, as she puts it, “competitive in track and competitive in school.” During her sophomore year, she participated in a program designed to introduce girls to engineering—and was hooked. “I fell in love with engineering through that program,” she says.
Once she’d set her sights on becoming an engineer, Bell says, her brother, Abdul-Rahman Lediju (who is now an attorney), directed her attention to the Institute. “He was the one who told me about MIT,” she says, remembering her excitement. “I thought: ‘I want to cure cancer and AIDS—and I’ll get to do math there!’”
At 18, Bell already knew she wanted to focus on biomedical engineering, but at the time it was only offered as a minor, so she majored in mechanical engineering. “Just looking at the trajectory of the curriculum, I knew it was a way to get a foundation in how to make stuff in general,” she says, remembering the sequence of courses, from Mechanics and Materials to Measurement and Instrumentation. “I knew I could learn biomedical engineering later. For me it was the perfect setup.”
In her junior year, while Bell was making her way through that curriculum, her mother died of breast cancer. The loss solidified her interest in cancer research and clarified her academic path forward. “I wanted to use everything I learned at MIT, and I wanted to save lives,” she says. “So I moved to early detection and ultrasound as the best possible tool, in terms of safety, portability, and cost-efficiency.”
Bell found the right next step at Duke University in the lab of biomedical engineer Gregg Trahey, whose work focuses on developing new ultrasound technologies. She knew his lab was the ideal fit even though she jokes, “I probably scared him with how direct and focused I was.”
Bell remembers her excitement at the prospect of going to MIT. “I thought: ‘I want to cure cancer and AIDS—and I’ll get to do math there!’”
During her first year in Trahey’s lab, Bell investigated what’s known as acoustic clutter—random noises or artifacts that are recorded and translated into ultrasound images and can interfere with their clarity and usefulness. “It makes it difficult to identify structures of interest,” she explains.
But a solution soon presented itself. Bell realized that when the motion of an ultrasound probe caused the abdominal wall to move while, say, the bladder was being imaged, some of these acoustic artifacts “moved” in the image too. Analyzing that movement led to ways of filtering out that clutter, resulting in clearer ultrasonic images with better contrast-to-noise ratio, one of the main metrics of ultrasound image quality. “What’s left behind is the structure itself,” she says.
One of Bell’s pioneering discoveries came during her final years at Duke, where she developed a technique known as short-lag spatial coherence beamforming. In ultrasonography, sound waves are transmitted through the body, and echoes that bounce off internal organs are used to form images of them. These images, traditionally, are created through a process known as “delay and sum” beamforming—a signal-processing algorithm that converts the acoustic echoes captured or received by an ultrasound transducer into an image that is displayed.
