Hierarchical Enhancement of Optical Coherence Tomography Images

Optical coherence tomography (OCT) is a noninvasive imaging modality that provides cross-sectional images from microstructures of tissues. This optical imaging system works based on Michelson interferometry principle and has intermediate resolution and penetration depth which makes it appropriate for imaging thin tissues such as skin and eye. OCT images suffer from three main artifacts that make images difficult to be analyzed. The first one is small grainy structures called speckle which degrade image quality and decreases axial and lateral resolution. The second one is light intensity attenuation which is a function of depth. It happens because of absorbing and scattering nature of tissue which causes loss of information especially in the deeper parts of images. The third artifact is blurriness of image which is because of limitation in imaging electronic hardware and some other imaging limitation. This artifact also decrease image resolution and destroys image sharpness. In this paper we propose a novel hierarchical image enhancement procedure in order to remove these artifacts and make OCT images more comprehensible and useful for physicians. This procedure contains attenuation compensation, image deblurring, and speckle reduction. The results show that high level of improvement after each enhancement step, qualitatively and quantitatively can be reached. SNR and CNR of enhanced image are increased about 3 and 4 times, respectively.