When cancerous lumps are conventionally excised from breast tissue, both surgeon and patient must wait days for pathologists at the lab to determine if all the malignancy has been successfully removed during surgery, by examining the margins of the surgery to look for stray cancer cells.

At present, 20 to 60 percent of patients have to go for a second surgery to have more tissue removed once lab results are in — but 3-D photoacoustic imaging is one method that could make those long waits a thing of the past.

"With 3-D photoacoustic microscopy (PAM), we could analyze the tumor right in the operating room, and know immediately whether more tissue needs to be removed,” Lihong Wang, a professor at Caltech's Division of Engineering and Applied Science, said in a statement.

Wang's research into the technique began when the Optical Imaging Laboratory – where the technique was developed – was located at Washington University in St. Louis. The lab then moved to Caltech's Andrew and Peggy Cherng Department of Medical Engineering in January 2017.

In the team's research, published in the journal Science Advances on May 17, the researchers showed that the system, which measures ultrasonic waves emitted by vibrating tissue, could identify cancerous cells. Diseased tissue tends to have larger nuclei and more densely-packed cells, they noted.

“Implementation of an intraoperative UV-PAM system for breast tumor excision could be transformative. Our UV-PAM system was able to image fixed, unprocessed breast tumors with an image quality comparable to that of conventional histology using processed, paraffin-embedded, sectioned, and H&E-stained specimens,” noted the researchers, adding, “although fixed breast tumors were imaged in this study to maintain tissue integrity during relatively long intervals between surgery and processing for histology, fresh breast tumors are expected to provide similar imaging contrast.”

The initial proof-of-concept results showed that PAM took about three hours to analyze a sample – already a big improvement over conventional microscopic approaches, which take about 7 hours to get comparable results.

“This is a proof-of-concept that we can use photoacoustic imaging on breast tissue and get images that look similar to traditional staining methods without any sort of tissue processing,” noted Washington University Associate Professor of Medicine Dr. Deborah Novack, a co-senior author on the study.

She added that since PAM images have many features in common with traditional staining techniques, "we can use the same criteria to interpret the photoacoustic imaging," noting that this means “we don't have to come up with new criteria."

Impressive as the initial results may be, with further work and faster laser pulses, Wang thinks the time could be shaved to as little as 10 minutes – useful for a variety of clinical applications.

"Because the device never directly touches a patient, there will be fewer regulatory hurdles to overcome before gaining FDA approval for use by surgeons," Wang noted. "Potentially, we could make this tool available to surgeons within several years."