Wide-field multispectral photoacoustic imaging of human melanomas in vivo

Cutaneous melanoma accounts for only 5% of skin cancer, but it is as dangerous as it is associated with 75% skincancer-related deaths. Clinical decision-making and prognosis is the thickness of melanoma into the tissue. Another feature is that the cancer that can occur anywhere on the body, including the face, chest, thigh, soles, and groin, and its size is also very diverse. Here, we developed a hand-held scanner and obtained 3D photoacoustic images of in vivo human melanoma by using multispectral real-time clinical photoacoustic and ultrasound imaging system with the scanner. The scanner allowed wide-field scanning of 3.8 cm (transducer aperture size) × 3 cm (scanning range). Four patients were recruited to obtain photoacoustic melanoma images of various sites (thigh, sole, etc.), types (in situ, invasive, etc.) and sizes (sub-mm to cm). Five wavelengths were used to perform spectral unmixing. The penetration depth of melanoma was successfully confirmed by the multispectral photoacoustic images. The melanoma depth measured by photoacoustic imaging was significantly similar to histopathologic results obtained after excision (mean absolute error = 0.6 mm). In this study, we acquired small-to-large size and various types of melanoma multispectral photoacoustic images in vivo. We hope that this study will be an additional criterion for histopathological results that may have a positive impact on the diagnosis, treatment, and prognosis of melanomas.