Non-invasive optical biopsy of skin lesions by multimodal system with OCT, ultrasound, photoacoustics and Raman spectroscopy

The incidence of skin cancer, including melanoma, has been steadily increasing over the past decades. Early-stage melanoma often exhibits minimal symptoms, making it challenging to detect. However, when it progresses to later stages and spreads to the lymph nodes, the chances of survival significantly decrease. The current diagnostic gold standard involves invasive and time-consuming procedures, such as visual examination, excision, and histological examination of tissue samples. As an alternative, we developed a new multimodal optical system that addresses these challenges by integrating ultrasound (US), photoacoustic tomography (PAT), optical coherence tomography (OCT) and Raman spectroscopy (RS) into a single measurement unit. The optical coherence tomography OCT delivers detailed structural and depth information for thin skin lesions, while US and PAT enable the assessment of penetration depth in thicker lesions, and Raman spectroscopy analyzes the chemical composition of skin lesions, aiding in the differentiation between benign and malignant cases. The US and PAT are seamlessly integrated using an acoustical reflector inside a custom-made water tank, enabling C-mode measurements at the same position as OCT and RS without the need to switch scanning heads. Our system offers a fast and non-invasive approach to measure the dignity and maximal depth of skin lesions, which can help the dermatologists to make informed decisions regarding excision margins. The exemplary imaging capabilities of the presented multimodal setup are demonstrated in vivo on human nevus, which was excised after the measurement. The obtained results are compared with corresponding histological images for comprehensive evaluation.