Photoacoustic Imaging

Developing less invasive biopsies

From the 2013 Department of Surgery Annual Report

Breast ImagingJulie Margenthaler, MD, and colleagues are employing photoacoustic tomography to pinpoint the target of breast biopsies so that biopsies can be done by needle rather than open surgery. WASHINGTON UNIVERSITY breast surgeons and biomedical engineers are using a new imaging technology to develop a less invasive method for sentinel lymph node biopsy — a critical part of breast cancer staging. Their efforts could help thousands of women avoid permanent adverse side effects that can occur with the current surgical biopsy.

Sentinel lymph nodes are the first nodes likely to be reached by cancer cells from breast tumors. In the current biopsy procedure, physicians inject a dye near the tumor, and in an open surgery, visualize the labeled nodes by eye and remove them; pathologists study the nodes microscopically to look for cancer cells and determine the stage of disease. Although side effects are uncommon, some, such as lymphedema and numbness, are significant and can be permanent.

“In the United States, there are approximately 230,000 new breast cancer cases a year, and a majority of those women will have sentinel node procedures,” says Julie Margenthaler, MD, Washington University breast surgeon at Barnes-Jewish Hospital. “If even one percent develops lymphedema, resulting in arm swelling, that’s thousands of women with a permanent condition from a relatively low-risk procedure.”
That’s why Margenthaler and colleagues have spent the last two years studying whether photoacoustic tomography, an imaging technique that combines strong optical contrast and high ultrasonic resolution, can pinpoint the sentinel lymph nodes noninvasively so that the biopsy can be done by needle. In the new procedure, she injects a blue dye near breast tumors; a probe detects the dye in the nodes and generates a computer image showing the location of the sentinel nodes.

The instruments were developed in collaboration with Philips Research by Lihong Wang, PhD, the Gene K. Beare DistinguishedProfessor of Biomedical Engineering, an international  leader in applying photoacoustic tomography to medical diagnostics.

As Margenthaler tested accuracy of the system in 25 patients, Wang made equipment modifications. The end result was an effective system for identifying sentinel lymph nodes.

Wang and Margenthaler have received a five-year National Institutes of Health (NIH) grant to compare pathology results of surgically removed sentinel lymph nodes with those of photoacoustic tomography needle biopsies. If the methods are equally as accurate, the next step will be disseminating the new technique.

“It would be a matter of making it so everyone understands how to use it,” says Margenthaler. “That shouldn’t be much of an obstacle because breast cancer specialists are already very comfortable with ultrasound technology.”