Laser surgery has been a novel solution for various clinical applications such as ophthalmology and dermatology. In clinics, pulsed lasers become the key light sources to provide high energies for tissue ablation or heating. However, various clinical applications are limited by the extremely high cost of pulsed lasers. Additionally, determination of the treatment region is a key issue for laser surgery. To achieve precise treatment, we developed an integration system by combining laser surgery and optical coherence tomography for the diagnosis and treatment of diseases. Since the beam size of the treatment laser ranges from tens to hundreds of micrometers, optical coherence tomography could be a potential tool for the guidance of laser surgery due to its micrometer-scale resolution. Based on the scattering property of biological tissue, a three-dimensional microstructure can be acquired with optical coherence tomography without extra contrast agents. Such microstructures can be used to determine the lesion region. Aside from the acquisition of tissue microstructure, an imaging algorithm for three-dimensional angiography is demonstrated. With the guidance of optical coherence imaging, the abnormal tissue can be identified, and the laser treatment can be noninvasively monitored. The integrated system can effectively improve treatment accuracy and simultaneously evaluate the treatment outcome. Currently, the proposed technology has been successfully demonstrated for the airway, oral cavity, brain tumors and skin tumors.

Laser surgery is an alternative solution for clinical treatment due to the advantages of less bleeding, reducing infections, and shorter recovery periods. Currently, laser surgery has been successfully applied in various applications including ophthalmology, dermatology, the gastrointestinal tract, the oral cavity including soft and hard tissues, and the spine. With laser surgery, tissue can be ablated or removed by being exposed to high optical energy. Moreover, the laser can be used for blood coagulation, which could be considered as a treatment strategy for diseases. Currently, pulsed lasers are the most popular for clinical applications because they can provide an extremely high peak energy to damage the targeted tissue without causing extra damage to the surrounding tissue. However, such short pulse lasers are typically bulky and very expensive. Additionally, the spot size of the treatment laser ranges from tens to hundreds of micrometers which can be used for treating a specific and small area. Limited to the spot size of the treatment laser, guidance with the imaging techniques will be necessary for accurate positioning and irradiation. Different imaging methods have been proposed as the guidance tools of laser surgery such as magnetic resonance imaging (MRI), computed tomography (CT), ultrasound imaging, microscopes, and endoscopes. However, since the imaging resolutions of MRI, CT, and ultrasound imaging are more than one hundred micrometers, it is difficult to identify a specific lesion for the laser surgery. Furthermore, although microscopes and endoscopes can achieve micrometer-scale resolutions, only the superficial layer of tissue can be visualized; therefore, it is difficult to investigate the thermal effect induced by the treatment laser in the deeper tissue layer. 

In our study, we aimed to develop a theranostic system combining laser surgery and optical coherence tomography (OCT). The OCT technique is similar to ultrasound imaging, but uses light waves to probe the tissue structure instead of acoustic waves. According to the backscattered intensity from various depths of the biological tissue, the three-dimensional microstructure of the tissue can be acquired. Moreover, we have developed the algorithm of label-free, OCT-based angiography (OCTA) to investigate the tissue microcirculation. Typically, the OCT resolution of our systems can reach 3-10 m in biological tissue. With OCT/OCTA, normal and abnormal tissues can be differentiated, and then, the treatment laser can be accurately positioned. Moreover, the treatment results can be in vivo monitored with OCT/OCTA. Our research topics on the development of the OCT-guided laser surgery include the following issues.