Researchers at Pohang University of Science & Technology in South Korea have developed a handheld photoacoustic device that can locate sentinel lymph nodes near the armpit. The technology could help clinicians to locate the correct lymph node from which to take a biopsy when checking for breast cancer metastases. At present, this process involves using radioactive probes, and so the current system can help patients and healthcare staff to avoid radiation exposure.
The lymph system provides a handy highway through the body for metastasizing cancers. Breast cancers and melanoma often hitch a ride through the lymphatic system when establishing metastases, and so this tissue represents an important region in which to test for metastasis. A sentinel lymph node is the first node to which cancer cells are most likely to spread, usually because they are the first few nodes into which a tumor drains. Using a biopsy to test the sentinel node can give a good indication of whether a cancer has spread to the lymph system.
However, before conducting a biopsy, a clinician needs to identify the location of a sentinel node. To determine which lymph nodes represent the sentinel node(s), clinicians typically administer a radioactive tracer near the tumor, and then use a detector to determine which lymph node(s) it localizes to. This isn’t ideal, as it exposes patients and healthcare staff to radiation, and requires specialized facilities and equipment to perform the procedure.
The new technology from Pohang University is radiation-free and relies instead on the photoacoustic effect. The device combines a transparent ultrasound transducer and a solid-state dye laser. It can irradiate an area of tissue containing a colored dye with the laser to generate a photoacoustic effect, the ultrasonic waves from which are detected by the transducer. To detect a sentinel lymph node, a user would inject a non-radioactive dye near the tumor and then use the new device to assess nearby lymph nodes.
So far, the Korean researchers tested the device in mice and were successfully able to locate a sentinel lymph node in their arm. Interestingly, they also investigated the ability of the device to detect melanoma in mice, and successfully identified the tumors, suggesting that the technology can also spot colored malignant tumors near the surface of the skin.
“We believe the photoacoustic finder system we have proposed is the first portable photoacoustic sensing tool for sentinel lymph node localization,” said Chulhong Kim, a researcher involved in the study, in a press release. “This research shows great potential to be helpful in detecting sentinel lymph nodes or melanoma without using radioactive substances in the future.”
Study in journal Photoacoustics: A photoacoustic finder fully integrated with a solid-state dye laser and transparent ultrasound transducer