Research On Medical Applications Of Swept Source OCT System

Optical coherence tomography(OCT)is a non-invasive optical imaging technique born in the early 1990 s,which enables measurement and imaging of biological tissues with micrometer resolution and millimeter depth.It can display the structural characteristics and pathological changes of biological tissues more clearly,which is suitable for detection and diagnostic analysis in Ophthalmology,dermatology and other medical fields,and is known as " optical biopsy " figuratively.Swept source OCT(SSOCT)is a type of Fourier Domain OCT(FD-OCT),which belongs to the third generation of OCT.This thesis focuses on the setup the 1310 nm SS-OCT system,and using the system to conduct related medical application research.The specific work contents are as below:(1)Setup of 1.3 μm SS-OCT system.In the hardware part of the system,the optical path structure and the modular design of the system are completed according to the performance indicators.A-Trigger signal from the swept source is used as the synchronization time sequence of the system to achieve the synchronization and coordinated operation of multiple modules.At the same time,a new A-Scan scanning mode is designed,which solves the problem of time delay and image offset in the system,and several adapted scanning modes are designed for different application scenarios.In the software control program development,a software program is written to control the work of the hardware system,the GUI interface of the system is designed by QT,and the problem of image carton caused by data transmission between each module is solved by using multi-threading technology and thread synchronization mutex.(2)Research on large depth and real-time imaging OCT System.To solve the problem of insufficient imaging range of the system,a 500 MHz clock inside the acquisition card is used as the sampling clock instead of the k-clock from swept source,and a time domain interpolation method based on spectral phase is used to resample the data.The imaging range of the system is increased from 5 mm to 18.57 mm(in vacuum),while ensuring the stability of the system’s axial resolution at large imaging depth.Then the effects of different interpolation functions on the imaging performance of the system are compared in the resampling process,and the results show that the piecewise spline interpolation is the best.To solve the problem of slow imaging speed caused by large amount of data,using CUDA to call GPU in the data processing module to realize parallel data processing further improves the imaging speed of the system.For 1024×4160 size data,the image refresh rate can reach 14～16 frames per second.(3)Application research of OCT in ophthalmology and dermatology.In dermatology,the skin of the back of the hand was examined by imaging first,then the pathological manifestations of nail lesions in patients with psoriasis and psoriatic arthritis were explored,and three kinds of nail lesion symptoms were summarized.In ophthalmology,the artificial eye model and isolated porcine eyes were first tested for imaging,and then the anterior segment of human with normal vision and corneal refractive surgery were imaged.The objectivity and feasibility of the system were verified by comparing the results of the measurement of corneal center thickness.