Cellular-Resolution Optical Coherence Tomography. Sheng-Lung Huang. Institute of Photonics and Optoelectronics National Taiwan University

Transcription

1 Cellular-Resolution Optical Coherence Tomography Sheng-Lung Huang Institute of Photonics and Optoelectronics National Taiwan University Outline - OCT introduction - In vitro single cell analysis - Ex vivo tissue imaging - In vivo human skin diagnosis 5/6/2014@Abbe Center of Photonics

2 Optical Coherence Tomography (OCT)- a low coherence interferometry Scattered light Specimen E ( ) E( t) E( t ) 1 D 2 D 3 D Axial position (Depth)

3 High-Dynamic-Range Imaging Broadband interference - Why Interference? Homodyne detection - Phase sensitive (i.e. optical path sensitive) - At least 3-dB advantage on S/N compared with direct PD detection - Insensitive to unwanted background - Broadband light source while narrow band detection Axial resolution ln o 3

4 S/N Ratio in OCT System Signal: I [ P r P s 2 P r P s cos( k 0 l )] I s 2 P P cos( k 0 l ) r s Noise: I 2 2 Shot noise: Due to random arrival of photons 2 sh 2qI dc B Excess intensity noise: Due to different wavelength Thermal noise: Electronic noise 2 re 4k B TB L 2 ex 2 I dcb SNR 2 8B ( / 4) P R 0 r [2q P0 ( / 4) P R 0 2 r Rr (1 V 2 ) / ] (4k B T / ) L Ref: A. F. Fercher, W. Drexler, C. K. Hitzenberger, and T. Lasser, Optical coherence tomography-principles and applications, Rep. Prog. Phys., 66, 239 (2003). 4

5 SNR (db) S/N Ratio Simulation Parameter 130 SNR SN sh R P mw 120 SN ex R SN th R Light source nm 25 nm V Photon detector NEP B W 100 khz 0.8 A/W Beam splitter ratio is 0.5. log R r If system is shot-noise-limited: P0 SNR 4 qb 5

6 Speckle Definition: Speckle appears in a signal when that signal is imposed of a multitude of independently phased additive complex components. i.e. random walks Largely constructive addition Largely destructive addition Ref: J. W. Goodman, Speckle phenomena in optics- theory and applications,

7 Spatial Resolution Axial resolution Lateral resolution E ( ) E( t) E( t ) Rayleigh criterion Sparrow criterion lc : ( ) FWHM of E Axial resolution l C 2 2ln 2 2 o r o 0.61 NA r 0.46 o NA 7

8 Resolution (micron) Required NA for isotropic resolution Isotropic Resolution Required NA for isotropic resolution High axial resolution needed Objective 20x 10x High lateral resolution needed Isotropic resolution needed Bandwidth (nm) 8

9 OCT vs. Confocal Microscopy l C ln c OCM can image with high transverse resolution at much lower numerical aperture than confocal microscopy because it does not depend on high axial resolution for optical sectioning. Ref. J. Fujimoto 2005 report 9

10 Penetration Depths and Ranges of Lateral Dimensions AFM: atomic-force microscopy AOH: all-optical histology BL: bioluminescence FL: fluorescence microscopy at visible wavelengths MEG: magnetoencephalography MRI: functional magnetic resonance imaging OCT: optical coherence tomography PET: positron emission Tomography TIR-FM: total internal reflection fluorescence microscopy Imagining imaging s future, Nature Reviews of Molecular Cell Biology, US: ultrasound. 10

11 Light Sources Used in OCT Light source c (nm) c (mm) Coherence power SLD (super luminescent light diode) 675 nm mw 820 nm mw 820 nm mw 930 nm mw 1300 nm mw 1550 nm mw Ti:sapphire femtosecond laser 810 nm mw Cr:forsterite femtosecond laser 1280 nm mw Yb-doped fiber 1064 nm mw Er-doped fiber 1550 nm mw Tm-doped fiber 1800 nm mw fs laser + Photonic crystal fiber 1300 nm nm mw Thermal tungsten halogen 880 nm mw 11

12 Norm. spectral density (a.u.) CW and Bright Broadband Sources DCF cross section - LCD devices - Ocular applications - OCT+confocal - Ophthalmology - Dermatology - Other biomedical organs - Semiconductor devices (IC, solar cell) - Moisture sensing SAED of DCF core l C 2 Ti 3+ :sapphire Ce 3+ :YAG Cr 4+ :YAG 2ln 2 2 o Wavelength (nm)

13 Axial resolution (mm) Intensity (a.u.) Glass-Clad Crystal Fibers base OCT Ultra-broad band Wavelength= 0.56 micron 1.5 Gaussian-like spectrum Wavelength= 0.84 micron Wavelength= 1.15 micron Wavelength= 1.31 micron Wavelength= 1.38 micron 1.0 Point spread function in air Bandwidth (nm) - Higher resolution - Less speckle Path length (mm) - Less image-pixel cross talk - Power independent resolution 13 - CW and cost effective - Satisfy FDA regulation: 20 mj/cm 2

14 Side Lobe Influence on Image Quality (large side lobe) Onion measured using CF light source Multi-layer Single layer 2 (small side lobe) A. C. Akcay, J. P. Rolland, and J. M. Eichenholz, Spectral shaping to improve the point spread function in optical coherence tomography, Opt. Lett. vol. 28, p. 1921,

15 OCT Schemes τ Reference arm OCT = Broadband light source + Michelson interferometer + scanning Source arm ω DUT 3D tomography Source arm Reference arm Detection Scan PD/CCD/CMOS Time-domain OCT Δω τ(t) 2 D 0 D Spectral-domain OCT Δω τ o 2 D 1 D Sweep source OCT ω(t) τ o 2 D 0 D Spatial-domain OCT Δω τ o 2 D 1 D Full-field OCT Δω τ(t) 0 D 2 D 15

16 CW Crystal Fiber Light Source Ce:YAG crystal fiber emission spectrum Point spread function Axial image crosstalk Pixel number AIC (db) 1 st adjacent nd adjacent rd adjacent -61 Theoretical analysis Out of a 70-μm crystal fiber Out of a 200-μm MMF Power and luminous flux 16

17 Outline - In vitro single cell analysis - Ex vivo tissue imaging - In vivo human skin diagnosis

18 Google on Cell Image 18

19 Cell Tomography Technologies Frozen cell by X-ray In vitro with tissue staining 20-μm Yeast cell: 5-μm diameter C. A. Larabell and M. A. Le Gros, X-ray tomography generates 3-D reconstructions of the yeast, Saccharomyces cerevisiae, at 60-nm resolution, Molecular Biology of the Cell, 15, pp ,

20 Skin Cells Tomography using Full-Field OCT Skin cells En face Cross section Keratinocyte Mature keratinocyte Melanocyte 20

21 Intra-cellular Organelle Imaging of BCC Basal cell carcinoma cell line BCC number: Matrigel dilution: 5X Matrigel volume: 50 μl 24hrs after seeding BCCs Microscope 2D image (50x objective ) Feature of the Week, J. W. Tjiu, NTU Hospital

22 Signal average (a.u.) Single Cell 3D Tomography Analysis Normal BCC Apoptotic BCC Sum SMF Free space Cell boundary Normal P < Apoptotic Normal group, ± Apoptotic group, ± The measured signal average & cell density of single cells show statistically significant difference between normal & apoptotic BCC cells. 22

23 Cell Segmentation Raw image w/ Gaussian filter w/ bilateral filter 3D segmented cell 4

24 HaCaT Tomography 10 µm Axial resolution= 0.9 µm Lateral resolution= 0.9 µm Frame rate: 10 fps Axial step per frame= 0.84 µm

25 Skin Cell Identification Parameters been considered: Signal average, signal dynamic range, signal variance, cell density, cell volume Cell volume Signal average Fibroblast (Hs68) Melanoblast (M5) Keratinocyte (HaCaT) Fibroblast (Hs68) P= P= Melanoblast (M5) P= P= Keratinocyte (HaCaT) P= P=

26 Ca 2+ Induced Keratinocyte Differentiation Increased [Ca 2+ ] results Rapid redistribution of molecules from the cytosol to the membrane in the formation of intercellular contacts Formation of cornified envelope by crosslinking loricine, involucrine and other proteins (Mol Cell Endocrinol 2001; 177: ) These subcellular changes results in alteration in back-scatting signals and might be detected by ultrahigh resolution OCT. Br. J. Dermatol. 1994; 130: Formation of desmosome 24 hours after increase Ca 2+ level to 1.2 mm (1550x) (Cell 1980; 19: )

27 Cell Discrimination: Keratinocyte in Differentiation States Epidermis structure Treated (1.2mM CaCl 2 in keratinocyte-sfm for 6 days) Epidermis cells from newborn BALB/c mice Keratinocytes begin in the basal layer as undifferentiated cells, the daughter cells lose proliferative ability and give rise to differentiated cells comprising the spinous, granular, and cornified layers. Control (in normal keratinocyte-sfm for 6 days) 6

28 Features Extraction/Reduction Features and components Components Skew Kurt SA_dB SV_dB Skew_dB Kurt_dB ADR VDR Skew-DR Kurt-DR TDR CD Cell_pixel CV SA_mask SV_mask SA SV H L % 90% 80% 70% 60% SVM analysis 5

29 A-scan of Primary Melanocyte T-mode en-face image Point A Point A Melanocyte Point B Point B Point C Point C Point D Immature keratinocyte Point D

30 Water Distribution in Cell: Simulation Model A-scan B-scan Collaboration with Prof. Snow Tseng

31 Impact of Rough Boundary a = 2 n 2 n 1 + n 2 b = 2 n 1 n 1 + n 2 n 3 = a b n 2 E i n 2 E back E back + a b E i n 3 =

32 Melanoma Cell Line 3D OCT cross sections 2D microscope 32 Cell size: ~ 30 μm

33 Outline - In vitro single cell analysis - Ex vivo tissue imaging - In vivo human skin diagnosis

34 Ex Vivo Anatomic Imaging of Skin FF-OCT cross section Skin schematic Stratum corneum Stratum lucidum Stratum granulosum Epidermis Stratum spinosum Stratum basale 20 μm Dermis wiki/epidermis_(skin) Incident power: 3 mw En face frame rate: > 10 frame/s 34

35 Aging Evaluation Female 1963 / inner arm Female 1923 / inner arm 20 mm 20 mm Male 1945 / face SC SS 30 mm 30 mm

36 Skin Quality Evaluation OCT cross-sectional image Layer number and total thickness 20 μm With hydration Total thickness: 33.8 mm Layer number: 12 Average layer thickness: 2.82 mm Expansion of hydration: 40% Total thickness (μm) # of layers Average layer thickness (μm) Maximum Minimum Average SD

37 Optical Biopsy? In vivo Mirau based OCT Skin histology 37

38 OCT Endface and Biopsy Comparison Nude mouse biopsy Epidermis Stratum corneum Stained biopsy OCT endface Dermis Hair follicle Hair follicle Fat cell 38

39 In-Vivo Fish Cornea Stroma Observation Conventional OCT Ce:YAG DCF based OCT Normal Clinical significance? Fuchs Keratoconus : Feature of the Week, 2010.

40 Time Evolution of Fish Cornea Time= 0 minute Time= 30 minutes Average thickness: 2.69 mm Standard deviation: 1.49 mm Time= 60 minutes Time= 90 minutes

41 Outline - In vitro single cell analysis - Ex vivo tissue imaging - In vivo human skin diagnosis

42 In Vivo Skin Diagnosis at Forearm 42

43 Melanin Cap z=176 En face Cross sections (max projection) x-z plane y-z plane z=192 z= x100 μm x100 μm 2 In vivo, forearm, 35-year-old male

44 Water refractive index Refractive Indices of Bio Specimen Tissue Index Epidermis 1.34 Dermis 1.41 Organelle --- Mitochondria 1.42 Nucleus 1.39 Ingredient --- Collagen 1.43 Keratin 1.51 Melanin 1.70 Protein DNA Extracellular fluid 1.35 cytoplasm 1.37 Lymphocyte 1. Plasma membrane (lipid): n=1.48, < 1% volume 2. Cytoplasm (protein & water): n=1.35, 49% volume 3. Nucleus (protein & water): n=1.39, 48% volume 4. Average: n=1.37 Breast cell 1. Normal cell: water content: %, average n= Cancer cell: water content 80 %, average n= Wavelength (µm) - V. A. Loiko, et al, Conference on Light Scattering by Non-spherical Particles,105 (2007). -

45 OCT on Deterministic Biometry? Melanin cap in epidermis 45

46 Dispersion and Extinction Coeff. Measured by OCT Validation T. S. Ho, P. Yeh, C. C. Tsai, K. Y. Hsu, and S. L. Huang, Spectroscopic measurement of absorptive thin films by spectral-domain optical coherence tomography, Optics Express, 22, No. 5, pp , 2014.

47 From Epidermis to Dermis En face Cross section In vivo flow cytometry?

48 30 mm Toward In Vivo Flow Cytometry: RBC Detection 30 mm mm Red blood cell - Typical dimension Diameter: 6.2~8.2 mm Thickness: 2~2.5 mm - Measured dimension Diameter: 7.2 mm Thickness: 1.8 mm

49 30 mm Toward In Vivo Flow Cytometry: White Blood Cell 30 mm mm White blood cell - Typical dimension (lymphocyte) Diameter: 7~15 mm - Measured dimension Diameter: 10.0 mm

50 Blood Flow Measurement at Forearm OCT cross section Real-time blood flow monitoring Orthogonal polarization imaging 50

51 On-Line Database 51

52 Change From Cellular Resolution Tomography to Early Disease Diagnosis Disconnect between structure and function in bio system. Function Beyond anatomy Severity of disease Structure - Necrosis/ apoptosis - Cellular interaction High resolution OCT Cellular signaling path - Activation/ pathway - System coordination - Disease diagnosis Broadband spectroscopic OCT, Raman,.. 52

53 Take home message - Full-field OCT with high resolution, high speed, and low image pixel cross talk could enable real-time cellular diagnosis of skin during clinics or in surgical operation. - It is crucial to link OCT tomogram features with clinical meaning, and OCT validation is ongoing in worldwide laboratories. - The integration of OCT (cellular-level resolution) with molecular-level spectroscopy could be extremely powerful in clinics for early disease and cancer diagnosis. 53

54 Acknowledgment NTU Hospital: MD Jeng-Wei Tjiu MD Chang-Hao Yang MD Chia-Tung Shun MD Yu-I Li NTU GIPO: Prof. Snow Tseng Taipei Veterans General Hospital: MD Chang-Youh Tsai MD Yen-Bo Tsao Dr. William Wang Dr. C. P. Chuang Dr. Mason Yen Dr. C. K. Wei Dr. R. T. Ueng 54

55 Vielen Dank für Ihre Aufmerksamkeit.