By Kate Becker<\/em><\/p>\n The operating room at Indiana University Health University Hospital was lit up with excitement and relief. The surgery, planned and rehearsed for months, was a success\u2014every trace of the tumor removed.<\/p>\n But this operating room was very different from the others lining the hospital hallway. For one thing, with the exception of the breast surgeon performing the lumpectomy, it was full of engineers, not other doctors and nurses. And it was the only operating room in the building\u2014in the world, actually\u2014using a new, experimental device called AcouStar, which is designed to pinpoint tumors so that they can be taken out faster and more accurately.<\/p>\n And then there was this little added quirk of the procedure: The patient was not actually a patient, but a cadaver, and the tumor was not really a tumor, but a small clip of metal standing in for the real thing. No life was saved that day. But Boston University engineers Ji-Xin Cheng, College of Engineering professor of electrical and computer engineering, biomedical engineering, and of materials science and engineering, Lu Lan (ENG\u201919), biomedical engineering graduate research assistant, and their colleagues at BU and Purdue University believe that, one day, AcouStar could lead to better outcomes for thousands of breast cancer patients.<\/p>\n More than\u00a0<\/span>300,000 women are diagnosed with breast cancer each year in the United States<\/a>, and most of those who are diagnosed with early-stage disease choose either lumpectomy or breast-conserving surgery, over mastectomy. Lumpectomy is less invasive than mastectomy and is typically easier to recover from. Both surgeries give patients an equal shot at survival.<\/p>\n However, lumpectomy does not always remove the whole tumor the first time around. In fact, one in four breast cancer patients needs repeat surgery soon afterward because microscopic examination reveals that trace cancer cells were left behind. Cheng, Lan, and their colleagues think that AcouStar will increase the odds of removing tumors completely on the first try.<\/p>\n Cheng\u2019s research group<\/a>\u00a0<\/span>invents new ways to study the body using light instead of invasive, and potentially toxic, chemical stains and labels. In 2016, Cheng and his coworkers were observing a lumpectomy surgery and noticed how long it took just for the surgeon to locate the tumor. \u201cThe surgeon may take a couple of hours to find the tumor, and sometimes they miss it,\u201d says Cheng. He wondered: \u201cIs there a way we can help the surgeon see the tumor in real time, during the surgery?\u201d<\/p>\n Many small, early-stage tumors can\u2019t be felt by hand during an exam, which makes them difficult to locate during surgery. For tumors like these, a doctor typically inserts a thin guide wire, less than a millimeter wide, into the breast prior to the lumpectomy, using mammography or ultrasound to make sure that the tip of the wire is sitting inside the tumor.<\/p>\n The technique is the gold standard, but because the position of the wire is not visible to the surgeon, finding the tumor is still a challenge, explains breast surgeon Linda Han, director of breast oncology at the Parkview Cancer Institute, who has been collaborating with Cheng\u2019s team since 2014. First, the surgeon has to mentally map two-dimensional scans onto a three-dimensional body. This maneuver is made more complicated by the fact that the patient\u2019s position changes between the time the wire is placed and the time she reaches the operating table. \u201cIf it\u2019s really deep you really have no idea where the tip of the wire is,\u201d says Han. The result: prolonged surgeries and higher rates of redo operations.<\/p>\n Cheng brought the problem to graduate student Lu Lan. Lan quickly devised a plan to harness what\u2019s called optoacoustic technology, which uses light to generate sound waves, to create a beacon that could broadcast the location of the guide wire tip. Then, after hearing that Microsoft\u2019s augmented reality headset, HoloLens, was taking early orders, Lan and Cheng got the idea to project a virtual image of the guide wire tip onto the HoloLens display during surgery. \u201cWe realized that augmented reality can be the part that fills the gap of improving the efficiency of the surgical guidance of our optoacoustic guide,\u201d says Lan.<\/p>\n AcouStar works by sending nanosecond flashes of laser light through a fiber-optic guide wire. Because the laser pulses are so short, they don\u2019t heat up the breast tissue; instead, their energy is converted into sound waves, too high for humans to hear, that ripple out in every direction.<\/p>\n Those sound waves are picked up by three sensors attached to an adhesive patch stuck on the outside of the patient\u2019s breast. By comparing the time it takes for the sound waves to arrive at each of the three receiving sensors, the device can triangulate the location of the guide wire tip to within less than a millimeter.<\/p>\n Device makers are developing similar beacons using a variety of different technologies, says Cheng. One is a tiny radioactive \u201cseed\u201d that the surgeon places at the site of the tumor. But that seed absolutely must be removed after surgery, and many hospitals are wary of taking on risk associated with temporarily implanting radioactive devices in the body. Another type of beacon sends out radio waves, but this approach isn\u2019t very precise, and the radio waves can also interfere with other electronic instruments used during surgery. AcouStar is appealing to surgeons and hospitals because it does not produce electromagnetic radiation or radioactivity, says Cheng.<\/p>\n Arriving at the concept was the easy part, says Lan. The hard part\u2014turning it into something that doctors would actually want to use\u2014was still to come.<\/p>\n \u201cDoctors and engineers speak different languages,\u201d says Cheng. While doctors are pragmatists, engineers are technology-first thinkers, Cheng explains, always devising new uses for the latest materials and techniques to come out of their labs. Even the most state-of-the-art gadget will flop if no one needs or wants it, says Cheng. \u201cIt may be cool, but it may not be useful.\u201d That\u2019s why Cheng takes a \u201cproblem-oriented approach,\u201d starting each project by working with doctors to identify a problem, rather than looking for jazzy applications of new technology.<\/p>\n Lan learned this lesson firsthand, when Han and her surgical colleague, Samilia Obeng-Gyasi, gently vetoed his proposal to use the HoloLens: the headset was just too heavy for a surgeon to wear for the duration of a surgery, they said. So Lan changed course, deciding to project the AcouStar guidance onto a tablet display instead.<\/p>\n In the spring of 2017, after three months testing a prototype on a silicone breast model called a \u201cphantom,\u201d Cheng, Lu, and their team were ready for a more realistic trial. At this proof-of-concept stage, they couldn\u2019t yet test it on a real patient. But they could try it out on a cadaver breast.<\/p>\n The solution was standard stuff for surgeons, but was way outside the engineers\u2019 lab-bench comfort zone. Lan spent three days discussing the idea with his team before deciding to go ahead with it, but ultimately it was an easy decision, he says: \u201cThe main thing, the goal, is to verify the device, so we have to push ourselves to overcome this mental barrier.\u201d<\/p>\n The team would have access to the cadaver for only three days, and Obeng-Gyasi would act as surgeon. On her very first try, she was able to completely excise the \u201cpseudo-tumor,\u201d but the researchers realized that the patch they had used to fix the sensors to the body wasn\u2019t sticky enough; it kept moving around during the surgery.<\/p>\n Two months later, after tweaking the sensor patch design, the team was ready to try again. They spent hours reviewing video footage of their previous attempt, figuring out how they could make the procedure faster and more accurate. The surgery was a success, and the team\u00a0<\/span>published\u00a0<\/a>their work in May 2018.<\/p>\nA New Tool for Doctors<\/h3>\n
Using Light and Sound to Treat Tumors<\/h3>\n
The Future of Surgery?<\/h3>\n