Use of coherent anti-stokes raman scattering (CARS) to meet the challenges of intraoperative imaging

A novel molecular diagnostic strategy using label-free modality has been used to handle the challenges of intraoperative imaging by combining the coherent anti-Stokes Raman scattering (CARS) optical imaging technique with a computerized image analysis system. In a CARS process, a pump field, Stokes field, and probe field interact with the samples through a four-wave mixing process. When the frequency difference is in resonance with a molecular vibration, an enhanced signal at the anti-Stokes frequency is generated in a direction determined by the phase matching conditions. By tuning the beating frequency, CARS provides chemically selective excitation of characteristic vibrational resonances, allowing imaging of particular chemical structures at will. In addition to cellular resolution, CARS allows 3-D imaging through optical sectioning. The intensity of CARS depends nonlinearly on two incident intensities; therefore CARS signals are tightly restricted to a very thin focal plan.