1 Swept Source Frequency Domain Optical Coherence Tomography Swept Source Frequency Domain Optical Coherence Tomography Anurag Gupta University of Rochester, BS: Biomedical Engineering Dr. Zhongping Chen, Dr. Jun Zhang and Dr. Qiang Wang The University of California, Irvine Department of Biomedical Engineering Beckman Laser Institute and Medical Clinic

2 Outline 1.Define OCT 2.Clinical Applications 3.Advantage of OCT Over Other Imaging Modalities 4.Types of OCT Systems 5.Motivations for Designing an FDOCT Imaging Modality 6.Sample OCT Image 7.Acknowledgements

3 What Is Optical Coherence Tomography? As Defined in 2005 by the Inventor, Dr. James Fujimoto: “Optical coherence tomography (OCT) is an emerging imaging modality which can generate high resolution, cross-sectional images of microstructure in biological systems...by measuring the echo time delay of optical backscattering in the tissue as a function of transverse position.”

4 Ophthalmology –Diagnosing retinal diseases and other abnormalities of the eye Dermatology –Early detection of skin cancer –Diagnosing skin diseases and other problems Cardiovascular –Imaging of the blood vessels and other cardiovascular areas for early detection of diseases Clinical Applications

5 Advantage of OCT 1 mm1 cm 10 cm Penetration depth (log) 1 µm 10 µm 100 µm 1 mm Resolution (log) Ultrasound OCT Confocal microscopy Standard clinical High frequency

6 Histology Versus “Optical” Biopsy of a Normal Hamster Cheek Pouch Woonggyu Jung, Jun Zhang, Jungrae Chung, Petra Wilder-Smith, Matt Brenner, J. Stuart Nelson, and Zhongping Chen. "Advances in Oral Cancer Detection Using Optical Coherence Tomography." IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS 11.4 (2005): July-Aug

7 OCT can be designed to be: compact, portable, relatively inexpensive, and can be easily connected to any number of image acquisition scanners Size of OCT Device This is a picture of our system in final stages

8 Scanning Reference Mirror Mirror Photodetector Beam splitter SLD Sample Time Domain OCT Frequency Domain OCT Time Domain OCT Frequency Domain OCT Elimination of Scanning Mirror Stationary mirror Photodetecter Beam splitter Swept Source Sample

9 Swept Source Laser System

10 Can You Have a Signal Without Noise? Motivations NO!

11 A High SNR Ratio: Higher Image Quality –Images are more distinguishable A Low SNR Ratio: Lower Image Quality –Images are less distinguishable Signal to Noise Ratio (SNR)

12 SNR of FDOCT Versus TDOCT FDOCT: acquire signal in the time window of T Signal term # of photons = Noise term # of photons = Where N is the # of pixels per depth scan We see that the SNR of FDOCT is N times better than that of TDOCT Fei Wang EE131 Presentation at Caltech

13 Dispersion is the separation of white or compound light into its respective colors, as in the formation of a spectrum by a prism. Dispersion Control This can cause the resolution of an image to decrease. In FDOCT, Dispersion can be controlled rather easily whereas in other imaging modalities its very difficult.

14 Before Dispersion Control Before Dispersion Control µm Resolution

15 After Dispersion Control After Dispersion Control 8 µm Resolution

16 Programmed Using Microsoft Visual C++ Speed: 15 / 16 Frames Per Second –Images can be Acquired In-Vivo or Ex-Vivo This makes it a viable option for use during surgery Image Acquisition Speed Image Acquisition Speed

17 3D Image Acquisition Scanner 3D Image Acquisition Scanner This is a picture of our 3D Image Acquisition Scanner

18 3D Image Acquisition Scanner Movie 3D Image Acquisition Scanner Movie

19 3D FDOCT Movie of the Retina

20 The National Science Foundation The University of California, Irvine (UROP) Dr. Zhongping Chen, Dr. Jun Zhang, Dr. Qiang Wang, and Mr. Bin Rao The Beckman Laser Institute and Medical Clinic The Air Force Research Laboratory The IM-SURE Fellows Acknowledgments