OCT System In Laser Cardiac Ablation And Dual-function Fiber-based Catheter

Catheter radio-frequency ablation is the common treatment for cardiac arrhythmia nowadays.There are some problems and shortcomings in the process of catheter radio-frequency ablation.Laser ablation and optical coherence tomography system is introduced.Laser ablation can achieve precise ablation with the thermal field controlled more precisely.It can also reduce heat diffusion and thermal damage with its advantage of energy concentration.Optical coherence tomography(OCT)technology is a non-invasive,high-resolution medical imaging technology,and it can image the inner structure of the biology tissues in vivo,which makes OCT popular among the doctors and researchers.OCT has been applied in detecting ophthalmic diseases successfully and widely,and it is hopefully used in dermatology,dentistry,cardiovascular and other biological tissue imaging.The main contents include: the principle of laser ablation,the principle and system of the swept source OCT,the design and produce of the GRIN fiber probe and the dual-function catheter,the ablation and imaging experiment and the characteristics of OCT images before and after ablation.The main work and achievement can be summarized as following:1.The swept-source OCT system with swept source is introduced and developed.The OCT system mainly consists of the swept source,the interferometer(including the reference arm and the sample arm)and the balanced detector.The swept source is based on MEMS tunable filter fast sweeping with the 1301 nm center wavelength.The tunable range of wavelength is 142 nm,and the sweep rate is 49.96 kHz with light average power of 14.3mW.A balanced detector is used in the system where relative intensity noise can be reduced while reducing the common mode noise.The detector is helpful to suppress self-coherent signals from the inner layers of the sample,the surface of the optical element,swept inside the light source device.The axial resolution of the system is 4 ?m(axial resolution of the experiment was measured 5.2 ?m),the maximum depth of imaging to 6.7 mm(when n = 1 in air),the maximum signal to noise ratio is 46.6 dB.2.The fiber-optic probe is designed and developed for the endoscopic OCT,which is based on the GRIN fiber.The single-mode fiber(SMF)and graded-index(GRIN)fiber are selected and fused.And the exit surface of the GRIN fiber is polished to a certain angle(10°),in order to scan and reduce the noise signal.The exit angle of the OCT probe is 170°,and the beam waist position is 0.9mm.The ablation fiber is for 1064 nm,with the core of 200?m,coating layer of 400?m,and NA of 0.22.The dual-function catheter consists of two channels,a channel for the OCT scanning probe and the other channel for the ablation fiber.3.The laser cardiac ablation OCT system consists of swept source OCT system,1064 nm laser ablation device,and the dual-function,and it is able to achieve the purpose of the ablation process with real-time monitoring and guidance of OCT imaging.OCT imaging system can image the tissue with high resolution and certain penetration depth in real time in the ablation process.Ablation laser energy and time can be controlled timely and precisely with the guidance of OCT images and the ablation position can be more accurate.The laser cardiac ablation OCT system can improve the safety of ablation,and reduce the suffering of patients with precise ablation.4.At the same time,OCT images of the cardiac tissue were collected in the ablation procedures,and the image characteristics were analyzed.It was found that,before ablation,the structure of cardiac tissue is highly organized and is birefringent,showing as a dark band in the OCT image.With the gradual ablation process and laser energy delivery,moisture of cardiac tissue reduced and the interference signal became weaker.The highly organized structure was destroyed,and birefringence and the dark band disappeared.Based on these characteristics,the ablation process can be accesses and guided better.