Skin cancer is the most common malignancy in the United States, with one in every five North Americans expected to develop skin cancer during their lifetime. Melanoma, which only comprises 1% of the total skin cancer cases, is by far the most fatal, with more than 10,000 deaths expected this year. The current gold standard for the diagnosis of skin cancer is biopsy followed by histopathology, but this process is invasive, time consuming, and requires expert skills to both obtain and diagnose the sample. Optical tools provide the ability to address these limitations through "virtual biopsies" of skin using noninvasive optical imaging techniques. Over the past decade, progress in confocal reflectance imaging, multiphoton microscopy, and optical coherence tomography have driven new methods and abilities for melanoma and non-melanoma skin cancer diagnosis.
All-fiber optical parameteric oscillator based design
Vibrational spectroscopy-based methods offer considerable benefit in the diagnosis of skin cancer, with Raman spectroscopy being employed for the identification of actinic keratosis, as well as basal and squamous cell carcinomas. However, the weak nature of the spontaneous Raman signal has limited its use in clinical imaging applications. The stimulated nature of coherent Raman scattering (CRS) imaging methods, including coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS), overcome the weak nature of spontaneous Raman scattering for molecule-specific and label-free imaging of skin in real-time at video-rates [1,2].
To extend the applications of these toolkits for both melanoma research and dermatology, improved portable imaging instruments need to be translated and used by medical professionals. Beyond using only CARS for imaging contrast, other imaging methods (including SRS, sum-frequency absorption (SFA), and related imaging) are needed for human studies. In order to achieve the needed portability, stability, and imaging performance needed for clinical utility the LBRC has recently developed a novel, all-fiber multimodal, portable CRS clinical imaging system. The system is based on a new all-fiber optical parametric oscillator (OPO) [Fig 1 (top)] and full fiberoptic implementation for excitation and collection of signals [3]. The system has been built to eliminate as many free-space components as possible and is a portable, alignment-free imaging tool that is robust against the routine movements, vibrations, and bumps in clinical spaces. Fiber optic coupling and splicing also simplifying laser light delivery and enabling lightweight handheld scanners. This results in a small instrument that can readily fit into clinical rooms and be operated by medical staff. The construction of the portable all-fiber CRS system [Fig. 1 (bottom)] will provide scientists and clinicians alike with a new tool to study melanoma and other skin cancers in situ.