Photoacoustic Device Enables In Vivo Melanoma Imaging

A new photoacoustic device could help doctors better diagnose and treat melanoma, one of the deadliest forms of skin cancer.

A team from Washington University in St. Louis developed a handheld instrument that uses lasers and sound waves. Used directly on a patient’s skin, it can accurately measure a melanoma tumor’s depth and details in vivo.

In the study, the researchers found that tumor cells produce more melanin than the healthy skin cells that surround them. The acoustic waves generated by the new instrument can also be used to map the entire tumor with high-resolution.

The new handheld probe; its motor, translation stage, ultrasonic transducer and optical fibers are all incorporated. Courtesy of Yong Zhou/Washington University in St. Louis.

Existing diagnostic techniques are not able to directly measure such tumors — skin scatters light, preventing high-resolution instruments from reaching deeply.

“None are really sufficient to provide the two to four millimeter penetration that’s at least required for melanoma diagnosis, prognosis or surgical planning,” said Washington biomedical engineering professor Dr. Lihong Wang, one of the researchers.

The thicker the melanoma tumor, the more likely it is to spread and the deadlier it becomes. However, the new device may allow for possible diagnosis at the time of the patient’s initial evaluation, allowing surgeries and subsequent treatment plans to be developed as soon as possible.

The researchers have also developed a technique with the new device called photoacoustic microscopy, which relies on an effect in which light is converted into vibrations. A laser beam is shined into the skin at the site of a tumor; the skin’s melanin absorbs the light and its energy is transferred into high-frequency acoustic waves.

It also delivers light around and below the tumor, which generates a bright image of the tumor's bottom and an accurate measurement of its depth. Having the ability to measure the depth of such tumors helps physicians to determine prognoses more accurately.

The device has been tested on artificial tumors as well as in live mice. Now, the researchers are conducting similar tests on humans.

In the future, the new instrument could be used to determine how a tumor’s volume relates to melanoma cancer outcomes.

The research was published in Optics Letters (doi: 10.1364/OL.39.004731).

For more information, visit www.wustl.edu.