PH880 Topics in Physics

Transcription

1 PH880 Topics in Physics Modern Optical Imaging (Fall 2010) KAIST PH880 11/10/2010

2 Overview of week 11 Monday: Digital Holographic Tomography Optical Coherence Tomography Wednesday: PhotoacousticTomography KAIST PH880 11/10/2010

3 Rotating the beam angle + high speed (Feld Group, MIT, Nat. Methods, 2006) KAIST PH880 11/10/2010

4 Projection (Radon) Diffraction (exact) k y f max k z SEM diffraction Radon KAIST PH880 11/10/2010

5 KAIST PH880 11/10/2010 Time-domain OCT

6 Coherence gating

7 Optical Coherence Microscopy KAIST PH880 11/10/2010 J A Izatt et al, OPTICS LETTERS / Vol. 19, No. 8 / April 15, 1994

8 Optical Coherence Microscopy OCT: Low NA b Δx x Lt Lateral resolution lti 4λ f Δ x = π d Depth of ffocus OCM: High NA b Δx 2 x b= 2z = π Δ R 2λ f=focal length d= lens diameter 8

9 Fourier-domain OCT no scanning of reference mirror the spectrum of the backscattered sample light amplitude FercherAF, HitzenbergerCK, DrexlerW, Kamp G, Strasser I, LiHC1993b Medical Optical Tomography: Functional Imaging and Monitoring vol IS 11, ed G M uller et al (Bellingham: SPIE Press) pp

10 Parallel OCT set-up with a 2D detector array Bourquin S, Seitz P and Salathe R P 2001 El Lett

11 Overview of week 11 Monday: Digital Holographic Tomography Optical Coherence Tomography Wednesday: Photoacoustic Tomography* KAIST PH880 11/10/2010 * Slides are modified from L Wang s lecture slides

12 High Relative Resolution: Depth-to-Resolution Ratio > 100 Modality Max depth Axial resolution Depth / Resolution Confocal/two-photon microscopy ~ mm ~1-2 microns >100 Optical coherence tomography ~1 mm ~10 microns >100 Magnetic resonance imaging / Ultrasonography ~ mm ~1 mm >100 X-ray CT ~200 mm ~0.1 mm >100

13 Photoacoustic imaging of cancer in vivo Melanoma Melanoma 1 mm Melanoma Histology B-scan image at 764 nm Melanoma 1 mm KAIST PH880 11/10/2010 Nature Biotech. 24, 848 (2006).

14 Photoacoustic Tomography: principle (1) Laser pulse (<ANSI limit: e.g., 20 mj/cm 2 ) (2) Local heating (~ mk) (4) Ultrasonic detection (scattering/100) (3) Ultrasonic emission (~ mbar) Physical Review E 71, (2005). Phys. Rev. Letters 92, (2004). Lihong Wang group, Washington University

15 Photoacoustic Tomography: principle 1. Short laser pulse (~ ns range) is spatially broadened and then used to irradiate biological tissue 2. Produces a temperature rise (~ mk in short time frame) 3. Thermo-elastic expansion causes emission of acoustic wave (discovered by Alexander Graham Bell) 4. Acoustic wave is measured by wideband ultrasonic transducers 5. Acquired signal is combined mathematically to reconstruct the distribution of optical energy absorption KAIST PH880 11/10/2010 V Ntziachristos et al, Nature Biotechnology, 23 3, (2005)

16 Reflection-mode Photoacoustic Microscopy: Illustration Sphere Ph hotoacousti ic signal Surface Sphere Time

17 Reflection mode Dark field Confocal Photoacoustic Microscopy: System Tunable laser Nd:YAG pump laser Motor driver Photodiode Translation stages Amplifier Optical illumination Ultrasonic transducer Conical llens Sample holder Base AD Computer Mirror Heater & temperature controller Dual lfoci Annular illumination i with a dark center Sample Optics Letters 30, 625 (2005) Nature Biotech. 24, 848 (2006).

18 Imaging Depth and Resolution in Photoacoustic microscopy 3 mm B scan of a black double stranded cotton thread embedded in rat Imaging depth: ~3 mm Axial resolution: ~15 microns Depth/resolution: ~200 pixels Lateral resolution: ~45 microns Acquisition time: 2 ms/a scan No signal averaging Optics Letters 30, 625 (2005).

19 Volumetric Imaging of Rat Microvasculature In Vivo Maximum amplitude projection onto the skin 1 mm Volume: 10 mm x 8 mm x 3 mm Optics Express 14, 9317 (2006).

20 Imaging of Skin: Burn in Pigs Acute thermal (175 o C, 20 s) burn in pig skin in vivo. Postmortem imaging at 584 nm optical wavelength. Photograph Healthy Coagulated ated tissue tissue Photoacoustic image B scan image Hyperemic bowl 1 mm 1 mm Hyperemic ring Histology Hyperemic bowl 1 mm itude [a.u.] PA ampl Burn depth ~1.7 mm Hyperemic bowl Skin surface Distance [mm] J Biomed Optics 11, (2006).

21 Imaging of Hemoglobin Oxygen Total hemoglobin concentration Saturation (SO 2 ) In Vivo SO 2 in segmented venules and arterioles Histology mm Arterial microsphere perfusion A 1 4 V Nature Biotech. 24, 848 (2006). 1 mm

22 Hemodynamics In Vivo (578, 584, 590, and 596 nm) Total hemoglobin Oxygen saturation Arteries and veins 1 mm Imaged SO Change in oxygenation Artery Vein Hypoxia Normoxia Hyperoxia Physiological states monitor SO2 change over time. Appl. Phys. Lett. 90, (2007).

23 In Vivo Genetic Imaging: Gene Expression in Gliosarcoma Tumor in Rat 1. LacZ (gene) 2. Bt Beta galactosidase t (enzyme ) 3. X gal (colorless substrate) 4. Blue product Image of blood vessels at 584 nm wavelength Image of expression of LacZ reporter gene at 635 nm wavelength Composite image 1 mm J Biomed Optics 12(2), (2007).

24 Imaging of Human Palm In Vivo Photo Maximum amplitude projection onto the skin Skin surface 0.3 mm 0.13 mm Skin surface B scan image mm Optical absorption Stratum corneum Nature Biotech. 24, 848 (2006).

25 Reading List 1. Ntziachristos i V, Ripoll J, Wang L, & Weissleder R (2005) Looking and listening i to light: the evolution of whole body photonic imaging. Nature biotechnology 23(3): KAIST PH880 11/10/2010