Frequency Domain Optical Coherence Tomography (FDOCT) Joon S Kim IMSURE Summer Research Fellow At Beckman Laser Institute University of California at Irvine Irvine, CA

OCT Optical Coherence Tomography –New field of imaging technology that can complement conventional imaging techniques –Based on interference of EM wave –Provide high spatial resolution cross-sectional view of tissues without excision –Endless potential biomedical applications Non-invasive Diagnostics

OCT vs. Conventional Imag. Tech 1 mm1 cm10 cm Penetration depth (log) 1  m 10  m 100  m 1 mm Resolution (log) OCT Confocal microscopy Ultrasound Standard clinical High frequency

Two kinds of OCT TDOCT –Time Domain OCT –Use of Scanning Mirror FDOCT –Fourier (Frequency) Domain OCT –Use of laser source over band of optical frequency –Advantages over TDOCT

My research experience with FDOCT are in 2 phases… First phase: –Understanding and Replicating FDOCT experimental setting from scratch Second phase: –Learning the physical and mathematical reasoning behind the magical DSP algorithm which extract images out of OCT data!

Part 1 FDOCT experiment set up Swept source Phase Modulator Sample Probe Detector1 Detector2 2 x 2 Coupler Grating Mirror Collimator Attenuator Fiber Fabry-Perot interferometer

Current FDOCT System No human intervention required Everything controlled from execution module in host computer Host computer –houses NI-6112: A2D Conversion of OCT data –performs digital signal processing –controls peripherals

Scanning sample Surface of sample is divided into imaginary grid. Each block in grid: Pixel Scanning in X direction –Lateral scan Scanning in Z direction –A scan Z X Y

Scanning sample (cont.) 1600 samples / A-scan (pixel) 400 A-scan / Lateral scan Lateral scanning Frequency: 2 KHz A-scanning Frequency: 10 MHz –Limited by A2D converter (NI-6112) Pixel size: 10 micron Slow process => not applicable in Vivo

With NI-5122 Max. Sampling Frequency: 100 MS/sec A-scanning Frequency: 100 MHz –More time for DSP –Boost lateral scanning frequency to 20 KHz –One step closer to in Vivo application of FDOCT