Spectral domain optical coherence tomography setup and small artery detection based on it

Non-contact, non-invasive, high-resolution tomographic 3D detection of has been widely demanded in various fields of scientific research and engineering applications. Optical coherence tomography (OCT) is an emerging three-dimensional and non-destructive detective technology. Based on low coherence interference (LCI). OCT, with its relatively high axial resolution and deep detection depth, is unique in non-destructive detection field. OCT uses the distinctive feature that low coherence length of broadband light source to achieve accurate positioning in the tissue under test, and then form a three-dimensional tomography by horizontal scanning. OCT boasts great potential in bio-medicine field. At the moment, OCT has been used in clinical application of ophthalmology, but it is still remain in the immature research stage in other medical detection fields. For exploring the possibility of OCT in detecting cardiovascular and cerebrovascular diseases, we formulated a complete frequency domain OCT (FD-OCT) system by using 850 nm low coherence light source with the conditions in laboratory. Our system is built under the theory of spectral domain OCT (SD-OCT), an important subclass of FD-OCT. The system establishment can be divided into four parts. First, interference optical path setup: a fiber-optic Michelson type interferometry is used in this system. Second, the acquisition of signal, in FD-OCT, the broadband interference is acquired with spectrally separated detectors, the optical path and adjustment mechanism of the spectrometer are designed by our own self, and a CCD scientific camera is used to acquire signals. Third, three-dimensional image restoration, the depth scan can be calculated by a Fourier-transform form the acquired spectra, we use Matlab to complete signal process, furthermore we use rolling guidance filter to improve the signal to noise ratio (SNR) after the depth signal is restored. Last, beam scanning, a 2-axis motion stage is used to acquire three dimensional information. The imaging performance of this OCT system has also been calibrated through the cover glass experiment. The system has been used for completing the tomographic detection of onion and human skin. It has been shown that varieties of cardiovascular and cerebrovascular diseases can be detected earlier under the test of blood vessel. With the system that mentioned before, we have successfully conducted the real-time tomography of human upper arm on the basis of single point detection and obtained various information such as cardiac pulse map at multilayer location under skin of upper arm, heart rate signal in different tissue under skin, depth and diameter width of small artery, blood flow velocity, providing a new possibility for clinical detection.