Laser-Induced Ultrasound Treats Melanoma

Now, investigators are developing a better detection and treatment process using laser-induced ultrasound.

"The incidence and mortality rates associated with melanoma have increased as much as 7% in recent years,” said Dr. Yubin Miao, a research assistant professor of internal medicine at the University of Missouri-Columbia (UM-C; Columbia, MO, USA). "Early melanoma tumor diagnosis and prompt surgical removal are a patient's best hope for a cure. Unfortunately, metastatic melanoma is resistant to current chemotherapy and immunotherapy regimens.”

Dr. Miao and colleagues are using radiopharmaceuticals such as technetium-99m and lasers that generate sound to identify and treat cancerous moles. They are trying to target receptors on the overexpressed cells of the melanoma and are using the technetium to visualize the moles and rhenium to treat it. Because the agents will be delivered selectively to the melanoma cells, the radiation dose to healthy tissues and organs will be negligible.

"Using a drug that would only identify deadly moles would help us immensely,” remarked Dr. Jon Dyer, assistant professor of dermatology at UM-C. "Nearly 60,000 people each year develop melanoma. The earlier we detect it the better a survival rate. A detection tool that is specific and accurate will help us fight this very dangerous problem much more efficiently.”

Once an abnormal mole is found, the next step is to create an image of the site. The scientists are using lasers to generate a high-resolution image of the affected region through photo-acoustics, which is laser-induced ultrasound but much more detailed, whereas the ultrasound generates sound waves and uses the echoes to create grainy images. The investigators used low-energy lasers to target blood vessels, generating a sound wave inside the body. A distinctive listening device then identified these sounds and created a detailed image on a computer. While an ultrasound's resolution is approximately 1 mm, the laser may create a resolution of about 10 microns.

One difference between using the laser instead of just ultrasound is that the laser can only penetrate the skin by a few millimeters. Although laser-induced ultrasound is not suitable for imaging deep organs, it is ideal for creating very detailed images of the skin's surface. These images can show dermatologists the precise size and shape of the dangerous skin cells and how far they penetrate. The specialists can then narrow in on therapeutic methods to kill the cancerous skin cells without ever touching the healthy ones.

"This research opens myriad possibilities. Currently, when we want to rid the skin of a dangerous birthmark or mole, we destroy the blood vessels in the area, but too much heat can destroy melanin and healthy skin cells. With the new technology, we will be able to target individual cells, thus reducing the damage to healthy tissue but increasing our accuracy to destroy the cancer,” said Dr. Dyer. He noted that dermatologists will also be able to treat noncancerous spots on the skin that are a result of capillary malformations, usually called port wine stains. Whereas they do not carry a risk of developing into melanoma, these stains can be a problem cosmetically. Utilizing photo-acoustics, clinicians could distinguish the moles better and have a higher success rate in treating them.

The investigators hope to start using the technology in clinical applications within the next two years. A pilot study has been planned for the summer of 2005.