A Worcester Polytechnic Institute researcher has developed a way to use laser-induced sound waves to reveal hidden blood vessels and nerves during robot-assisted surgery — and overlay that data as augmented reality onto live surgical video.
Even in the hands of a skilled surgeon, minimally invasive operations carry a hidden danger: the anatomical structures lurking just beneath the surface of tissue, invisible to the naked eye. A researcher at Worcester Polytechnic Institute is working to change that, using a cutting-edge imaging technique to give surgeons a real-time, augmented-reality view of what lies below.
Kai Zhang, an associate professor at WPI, presented his work at the 190th Meeting of the Acoustical Society of America in Philadelphia on May 11. His research focuses on integrating photoacoustic (PA) imaging into robot-assisted laparoscopic surgeries — a class of minimally invasive procedures used for abdominal and pelvic operations.
The Problem With Minimally Invasive Surgery
Laparoscopic surgeries are performed through small incisions, with surgeons guided by a tiny internal camera called a laparoscope. The approach offers real benefits for patients: less pain, faster recovery and smaller scars. But the compact visual field also limits what a surgeon can detect. Blood vessels, nerve bundles, and other critical structures that lie just beneath the tissue surface remain largely invisible — and striking one accidentally can have serious consequences.
“Accidentally severing a hidden blood vessel during robot-assisted laparoscopy occurred in 1%-2% of cases depending on the procedure,” Zhang said in a news release. “Furthermore, such incidents can result in a range of complications, including hemorrhage, paralysis, and, in the worst cases, fatal outcomes.”
Those numbers may sound small, but across the millions of laparoscopic procedures performed every year in the United States alone, even a 1% complication rate translates to thousands of potentially preventable injuries.
How Photoacoustic Imaging Works
Photoacoustic imaging works by firing pulses of laser light deep into biological tissue. When tissue absorbs the light, it heats up slightly and expands, generating ultrasonic sound waves — a phenomenon known as the photoacoustic effect. Those waves travel back through the tissue and are captured by ultrasensitive microphones. Because different tissue types absorb light differently, the resulting sound wave patterns can be decoded to map out what’s beneath the surface with remarkable precision.
The technique can detect structures like blood vessels and nerve clusters that standard laparoscopic cameras simply cannot see. Zhang’s system processes that data to build three-dimensional representations of neurovascular bundles — dense groupings of nerves and blood vessels that surgeons are most concerned about damaging.
“This capability enables visualization of embedded anatomical structures and their depth locations, which is highly valuable for surgical planning and intraoperative monitoring,” Zhang added.
Critically, Zhang’s team didn’t just develop the imaging system in isolation. They integrated it into the actual surgical workflow: the 3D maps of subsurface structures are overlaid directly onto the live video feed from the laparoscopic camera, creating an augmented reality display that surgeons can consult in real time without interrupting an operation.
Tested in Prostate Cancer Surgery
Zhang validated the approach during radical prostatectomies, the surgical procedure used to remove prostate cancer. The prostate gland sits in close proximity to blood vessels and nerve bundles that control bladder function and sexual function — making it one of the higher-stakes environments in which to test a system designed to avoid subsurface damage. The ability to see those structures before accidentally disturbing them is exactly the kind of advance that could reduce post-surgical complications for patients.
But the implications extend well beyond prostate surgery. Laparoscopic procedures are used in gallbladder removal, colon surgery, gynecological operations, and a range of other common interventions. Any surgery that involves working around hidden anatomical structures could potentially benefit from real-time subsurface imaging.
“We anticipate that this imaging instrumentation will be readily translatable to not only other laparoscopic procedures but also other image-guided procedures,” added Zhang.
Why It Matters for the Future of Surgery
The convergence of robotics and artificial intelligence in the operating room is already transforming surgical medicine. Systems like the da Vinci Surgical System have given surgeons finer motor control than the human hand alone can achieve. What has lagged behind is the sensory side of the equation — the ability to perceive tissue composition and hidden structures in real time.
PA imaging addresses that gap directly. Unlike traditional ultrasound or MRI, photoacoustic probes can be designed to fit within the small incisions of laparoscopic surgery and operate without disrupting the procedure. The ability to add a layer of subsurface structural data to a live augmented reality display represents a meaningful step toward surgeries where accidental damage to hidden anatomy becomes far less likely.
For medical and biomedical engineering students, the work also highlights an increasingly important frontier: the integration of imaging physics, signal processing and surgical robotics into unified systems. Interdisciplinary expertise in optics, acoustics and clinical workflows is exactly the kind of background that will drive the next generation of surgical tools.
Source: Acoustical Society of America