Combines light, sound to create detailed images of cells more quickly than current approach.
Researchers at Washington University School of Medicine in St. Louis and California Institute of Technology report that they have developed a technology to scan a tumor sample and produce images detailed and accurate enough to be used to check whether a tumor has been completely removed.

Called photoacoustic imaging, the new technology takes less time than standard analysis techniques. But more work is needed before it is fast enough to be used during an operation.

The research was published May 17 in the journal Science Advances.

“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,” said Deborah Novack, MD, PhD, an associate professor of medicine, and of pathology and immunology, and a co–senior author on the study.

The researchers are working on improvements that they expect will bring the time needed to scan a specimen down to 10 minutes, fast enough to be used during an operation. The current gold–standard method of analysis, which is based on preserving the tissue and then staining it to make the cells easier to see, hasn’t gotten any faster since it was first developed in the mid–20th century.

“Right now, we don’t have a good method to assess margins during breast cancer surgeries,” said Rebecca Aft, MD, PhD, a professor of surgery and a co–senior author on the study. Aft, a breast cancer surgeon, treats patients at Siteman Cancer Center at Barnes–Jewish Hospital and Washington University School of Medicine.

To speed up the process, the researchers took advantage of a phenomenon known as the photoacoustic effect. When a beam of light of the right wavelength hits a molecule, some of the energy is absorbed and then released as sound in the ultrasound range. These sound waves can be detected and used to create an image.

“All molecules absorb light at some wavelength,” said co–senior author Lihong Wang, who conducted the work when he was a professor of biomedical engineering at Washington University’s School of Engineering & Applied Science. He is now at Caltech. “This is what makes photoacoustic imaging so powerful. Essentially, you can see any molecule, provided you have the ability to produce light of any wavelength. None of the other imaging technologies can do that. Ultrasound will not do that. X–rays will not do that. Light is the only tool that allows us to provide biochemical information.”

The researchers tested their technique by scanning slices of tumors removed from three breast cancer patients. For comparison, they also stained each specimen according to standard procedures.

The photoacoustic image matched the stained samples in all key features. The architecture of the tissue and subcellular detail such as the size of nuclei were clearly visible.

Having established that photoacoustic techniques can produce usable images, the researchers are working on reducing the scanning time.

Aft, Novack and Wang are applying for a grant to build a photoacoustic imaging machine with multiple channels and fast lasers.

“One day we think we’ll be able to take a specimen straight from the patient, plop it into the machine in the operating room and know in minutes whether we’ve gotten all the tumor out or not,” Aft said. “That’s the goal.”