Melanoma tumors are typically easy to access, yet while they are typically found on the skin it’s still a challenge to measure how deep they are. This presents a challenge for physicians deciding on an optimal treatment route, as the depth of the tumor defines which therapies it’s most susceptible to. Optical methods aren’t effective because light doesn’t penetrate tumors very well, while ultrasound just doesn’t produce enough contrast to see the tumors against healthy tissue. MRI and PET scans are expensive and suffer from their own limitations.
Researchers at Washington University in St. Louis have now developed a device that utilizes the photoacoustic effect to visualize melanoma tumors from the surface of the skin. The device is positioned over a tumor and a laser beam is activated to shine light onto and around the tumor. The tumor absorbs the energy from the laser, in turn vibrating in relation to the amount of melanin present, the chemical that reacts strongly to light. Since melanoma tumors produce more melanin compared to healthy skin, the returning signal can be analyzed to identify their shape and volume.
From the study abstract in Optics Letters:
We show that melanomas with 4.1 and 3.7 mm thicknesses can be successfully detected in phantom and in in vivo experiments, respectively. With its deep melanoma imaging ability and handheld design, this system can be tested for clinical melanoma diagnosis, prognosis, and surgical planning for patients at the bedside.
Study in Optics Letters: Handheld photoacoustic microscopy to detect melanoma depth in vivo…