Ultrahigh Speed OCT And Its Applications In Clinical And Forensic Study

Optical coherence tomography(OCT)is an emerging optical imaging modality in biomedical research and other studies because it enables high resolution,non-contact,and non-invasive visualization of tissue inner structure in a high speed manner.In this dissertation,to solve the practical problems in clinical and forensic field,three OCT systems,including a time domain OCT(TD-OCT),a spectral domain OCT(SDOCT)and a swept-source OCT(SS-OCT)were developed.Port wine stains(PWS)is a common skin disease resulting from capillary dilation and malformation in the upper dermis of skin.Quantitative measurements of vascular structural and skin characteristic parameters obtained non-invasively by the TD-OCT system were useful in PWS diagnosis and might aid the optimal Photodynamic therapy(PDT).The 3D SD-OCT system was employed to exploit its ability in forensic science.The results demonstrated that SD-OCT was favorable for automotive paint identification,recovery of the hidden internal-damaged scratching of repainted paint,detection of latent fingerprint hidden beneath adhesive tape,determinations of death using pathological examination,and visualization of hair follicles for individual identification via a non-destructive and fast manner.The SS-OCT system was used for imaging defects and wall thickness of ex vivo root canal in real time.The crack on the root canal wall caused by the endodontic files and reamers during root canal therapy could be assessed in the cross-section OCT images.Imaging speed is one of the most important parameters that define the performance of OCT system.Thus,increasing OCT imaging speed is an important research direction since OCT was first introduced.First of all,we proposed an ultrahigh speed SS-OCT system based on time-stretch swept source that had advantages of all-fiber design and linear wavenumber output.Biomedical OCT images were obtained at 40 MHz A-line rate without any A-line averaging.Furthermore,in order to break the bottleneck of massive data real time processing in ultrahigh speed OCT system,we developed optical computing OCT(OC-OCT)by utilizing a new concept of optical real time Fourier transform as a substitute for fast Fourier transform(FFT)of digital signal,and employed an all-optical OC-OCT system with the real time A-line processing speed up to 10 MHz,which was 3 times faster than the highest record using SS-OCT.Last but not least,we combined the concepts of dispersion compensation and frequency mixer with OC-OCT and proposed an updated OC-OCT system,called as dispersion optimized frequency mixing OC-OCT(DOFM-OC-OCT).The DOFM-OC-OCT could achieve significant improvement in performance of signal-to-noise ratio(SNR)and axial resolution while had much lower cost than the original OC-OCT.The experimental results demonstrated that the DOFM-OC-OCT was capable of 17.3 Volumes/s(VPS)real-time 3D OCT image speed.The results of this dissertation show that OCT imaging has great potential in clinical and forensic applications.In addition,DOFM-OC-OCT,based on the innovative optical computing theory with dispersion optimizing and frequency mixing,has bring real time OCT imaging speed to new heights.We believe DOFM-OC-OCT has potential to be the next generation of ultrahigh speed OCT and will offer a valuable methodology for clinical applications,e.g.,real-time surgery guidance using 3D mixed reality.