Digital signal processing in optical coherence tomography

Optical coherence tomography (OCT) is a novel medical imaging modality which utilizes coherence ranging to perform high resolution (approximately 10 micrometer) non-invasive sub- surface imaging of biostructures. We have developed an OCT system consisting of a low-coherence interferometer and a calibration interferometer allowing sub-micron interferogram acquisition accuracy. We propose some digital signal processing strategies for image enhancement in optical coherence tomography. A linear shift invariant system model is presented for describing coherent light-tissue interactions in optical coherence tomography. In this model, the electric field backscattered from a target specimen is treated as a convolution of the incident field and a postulated tissue impulse response which describes the profile of scattering sites within the specimen. Based on this model, a novel technique for enhancing the sharpness of optical coherence tomographic images of biological structures using digital deconvolution is demonstrated. Using this approach, resolution improvement by a factor of greater than 2.2 is achieved in the longitudinal direction.