1.7-μm swept-source OCT system for deep brain tumor margin detection

Abstract

It is difficult to distinguish a tumor from a normal tissue in brain cancer surgery, especially at the infiltrative zones. Incomplete resection often leads to recurrence of the disease and has a negative effect on survival. In order to distinguish the side boundary and depth margin of tumor, we calculated the optical attenuation coefficient along the depth direction of a sample using OCT images. The depth-resolved attenuation coefficient was used to classify the back margin of the tumor in the depth direction. A 1.7-μm SS-OCT was implemented to enhance the calculable range of the tumor depth margin. The longer wavelength of the light source was used to reduce the light scattering passing through the sample tissue. A brain tumor model (U-87MG, 3 weeks after injection) was made on a nude mouse (2 weeks). We have imaged the extracted mouse brain and compared the coefficient values by using a conventional 1.3-μm and 1.7-μm wavelength SS-OCT systems. The optical attenuation in the tumor region was 1.8 times larger in 1.3-μm SS-OCT than 1.7-μm SS-OCT. The relative ratio of the optical attenuations, between the tumor region and normal tissue region, were 1.67 in the 1.3-μm wavelength range and 2.45 in the 1.7-μm wavelength range, respectively. The proposed brain tumor imaging system with 1.7-μm SS-OCT enhanced the imaging range of the depth margin of tumor and clearly imaged the side boundary between the tumor and normal tissue regions.