Ultrasound-Aided High-Resolution Biophotonic Tomography

Transcription

1 Ultrasound-Aided High-Resolution Biophotonic Tomography 1 cm Lihong V. Wang, PhD Gene K. Beare Distinguished Professor Optical Imaging Laboratory Department of Biomedical Engineering Washington University in St. Louis LHWang@biomed.wustl.edu Presented at IMI Workshop, Montreal, Canada, May 4,

2 Credits to to Lab Members CURRENT MEMBERS H. Fang A. Garcia-Uribe S. Hu X. Jin R. Kothapalli C. Kim G. Ku C. Li L. Li Y. Li K. Maslov M. Pramanik K. Song L. Song E. Stein M. Todorovic X. Xu X. Yang R. Zemp H. Zhang FORMER MEMBERS J. Ai, PhD D. Feng, MS J. Hollmann S. Jiao, PhD J. Li, PhD M. Li, PhD G. Marquez, PhD M. Mehrubeoglu, PhD J. Oh, PhD Y. Pang, MS S. Sakadzic, PhD M. Sivaramakrishnan, MS E. Smith, MS H. Sun, PhD X. Wang, PhD Y. Wang, MS FORMER MEMBERS X. Xie, MS M. Xu, PhD Y. Xu, PhD G. Yao, PhD W. Yu, MS X. Zhao, MS

3 Credits to to Collaborators Texas A&M University (Animal study): G. Stoica, DVM UT MD Anderson Cancer Center (Clinical study & molecular contrast agents): M. Duvic, MD B. Fornage, MD K. Hunt, MD C. Li, PhD V. Prieto, MD Nanospectra (Nanoshells): P. O Neal, PhD J. Schwartz, PhD D. Payne

4 Outline Motivation and challenges Ultrasound-modulated optical tomography (UOT) Laser-induced photoacoustic tomography (PAT) RF-induced thermoacoustic tomography (TAT) Summary

5 Motivation for Optical Imaging Safety Non-ionizing radiation: photon energy is ~2 ev. Physics Related to the molecular conformation of tissue. Optics High intrinsic contrast: Optical absorption: Angiogenesis, hyper-metabolism, apoptosis, necrosis, and exogenous contrast agents. Optical scattering: Size of cell nuclei. Optical polarization: Collagen, muscle fibers. Physiology Functional imaging of physiological parameters: Oxygen saturation of hemoglobin Total hemoglobin concentration (related to blood volume) Enlargement of cell nuclei Orientation of collagen Denaturation of collagen Blood flow (Doppler) Physiology Molecular imaging (exogenous contrast agents)

6 Challenges in in Optical Imaging OM, SNOM 1 mm CFM, 2PM, SHM, etc. Soft limit = ~l t Hard limit = ~10 δ = ~5 cm OCT DOT, UOT, PAT OM: Optical microscopy SNOM: Scanning near-field optical microscopy CFM: Confocal microscopy 2PM: Two-photon microscopy Simulation software MCML SHM: Second harmonic microscopy available from OCT: Optical coherence tomography DOT: Diffuse optical tomography UOT: Ultrasound-modulated optical tomography PAT: Photoacoustic tomography

7 Outline Motivation and challenges Ultrasound-modulated optical tomography (UOT) Laser-induced photoacoustic tomography (PAT) RF-induced thermoacoustic tomography (TAT) Summary

8 Motivation for Combining Light with Ultrasound Properties Diffuse optical tomography Ultrasonic imaging Ultrasoundmodulated optical tomography Contrast Excellent (functional) Poor in early cancers Excellent (= DOT) Resolution Poor (~5-10 mm) Excellent & scalable Excellent (= US) Imaging depth Good (~5 cm) Good & scalable Good Speckle artifacts None Strong None Scattering coefficient Strong (~100 /cm) Weak (~0.3 /cm)

9 Power Spectrum of of Ultrasound-modulated Light US 0.8 Without Ultrasound With Ultrasound Laser Scattering Medium Detector Intensity [a.u.] Modulationdepth: M = I I I1/I0= Frequency [MHz] Physical Review Letters 87, (2001). Physical Review E 72, (2005) Physical Review Letters 96, (2006)

10 Ultrasound-modulated Optical Tomography Sample Laser CCD Camera Ultrasonic Transducer Function Generator Power Amplifier Computer

11 Image of of 4.5-cm Thick Biological Tissue y 2 mm x Applied Optics 42, 4088 (2003)

12 Ultrasound-modulated Optical Computed Tomography: Experimental Configuration (Reflection detection) (Transmission detection) CCD Biological sample CCD Ultrasonic beam Laser Object Rotation z x y Linear scan Ultrasonic transducer

13 Ultrasound-modulated Optical Computed Tomography: Tomogram vs. Photograph 2 mm z x Applied Physics Letters 84, 1597 (2004)

14 Frequency Encoding along Ultrasonic Axis (z) (z) Snapshot of frequency z Ultrasonic Transducer f 1 f 2 f 2 Laser f 1 Ultrasonic Absorber z Analogous to MRI

15 Image of of Biological Tissue Acquired with Frequency Sweeping (Chirping) Ultrasonic axis z Lateral dimension x Optics Letters 25, 734 (2000)

16 Ultrasound-modulated Virtual Light Source Observed with Frequency Sweeping (Chirping) Courtesy of Atlan M, Forget BC, Ramaz F and Boccara AC (2003)

17 Axial Resolution by by Pulsed Ultrasound Modulated intensity [AU] Ultrasonic axis z Optics Letters 29, 2770 (2004)

18 Outline Motivation and challenges Ultrasound-modulated optical tomography (UOT) Laser-induced photoacoustic tomography (PAT) RF-induced thermoacoustic tomography (TAT) Summary

19 Orthogonal-mode Photoacoustic Tomography (1) Laser pulse (<ANSI limit: e.g., 20 mj/cm 2 ) (2) Local heating (~ mk) (4) Ultrasonic detection (scattering/100) Physical Review E 71, (2005). Phys. Rev. Letters 92, (2004). (3) Ultrasonic emission (~ mbar)

20 Photoacoustic Wave Equation: Delta-pulse Excitation ( v s p 0 : 2 ( r) A( r) :spatial Γ( r) speed of = 1 v 2 s A( r) Γ( r) : 2 s / C β : the isobaric C p = βv t 2 2 : : the specific ) p( r, t) = sound initial absorption p p0( r) 2 v stress function Gruneisen coefficient volume expansion coefficient heat in J/(K Kg) s dδ ( t) dt distribution

21 Photoacoustic Forward Solution in in an an Infinite Medium: Time Domain p( r p( r v s p 0 : 0 0 ( r) A( r) :spatial Γ( r) 1, t) = 2 4πv t, t) : speed of = A( r) Γ( r) : / C β : the isobaric C p = βv measured signal 2 s s sound absorption function p : V ' dr' r r' initial stress Gruneisen coefficient volume expansion coefficient : the specific heat in J/(K Kg) 0 p 0 ( r') δ ( t r 0 distribution r' v s )

22 Photoacoustic Forward Solution in in an an Infinite Medium: Plane Wave

23 Photoacoustic Forward Solution in in an an Infinite Medium: Spherical Wave

24 Photoacoustic Forward Solution in in an an Infinite Medium: Frequency Domain Fourier transformation: ~ p ( r k = + 0, ) p( r k = ω / c; t = ct 0, t )exp( ikt ) dt Measured pressure at k (forward solution): ~ ~ ( ( out) p r0, k) = ik dr' G ( r', r0 ) p0( r') V k Green s function (outgoing monochromatic spherical wave): ~ ( ) G out k ( r, r ) = exp( ik r r ) (4π r r )

25 Photoacoustic Inverse Solution in in an an Infinite Medium: Frequency-domain Reconstruction Planar, cylindrical, and spherical detection surfaces: p 1 ~ ~ *( s ( out) ( r') = + dk dr0 p r0, k)[ n0 0Gk ( r', 0)] π S ( b) 0 r Time reversal Dipole radiation Green s function (outgoing monochromatic spherical wave): ~ ( ) G out k ( r, r ) = exp( ik r r ) (4π r r ) Phys. Rev. E 71 (1): (2005)

26 Photoacoustic Inverse Solution in in an an Infinite Medium: Time-domain Reconstruction Planar, p r ( ) cylindrical, 2 Ω r and spherical [ p( r, t) t p( r, t) / t] 0 0 r detection surfaces : = r r 0 0 dω t= v s 0 0 Beamforming High-frequency contribution dω 0 :solid angle subtended by detection element Physical Review E 71, (2005). Physical Review Letters 92, (2004)

27 Experimental Setup of of Orthogonal-mode Photoacoustic Tomography Nd:YAG Dye-laser z Trigger Step motor y x Computer Concave lens Ground glass Oscilloscope Water tank Transducer Amplifier

28 (cm) 1.5 Non-invasive Transcranial Photoacoustic Image of of a Rat Brain with a Lesion PAT image Open-skull photograph MF V L V 0 RH LH (cm) Min Optical absorption Max Nature Biotech. 21, 803 (2003). L: Lesion LH: Left hemisphere MF: Median fissure RH: Right hemisphere V: Blood vessel

29 Functional Imaging of of Rat Whisker Stimulation In In Vivo PAT image (left stimulation) PAT image (right stimulation) 0.5 (cm) (cm) (cm) (cm) 0 Min Differential absorption Max Nature Biotech. 21, 803 (2003). Min Differential absorption Max

30 Non-invasive Transcranial Photoacoustic Image of of a Mouse Brain: 3D Imaging PAT image (5 mm deep) Histology (cm) CB FT HC FL CT OL (cm) Optics Letters 28, 1739 (2003). Max Optical absorption Min CB HC CT FT FL OL CB: Cerebellum CT: Cortex cerebri FL: Fissura longitudinalis cerebri FT: Fissura transversa cerebri HC: Hippocampus OL: Olfactory lobes

31 Photoacoustic Angiography of of Rat Brains In In Vivo (A) Without ICG-PEG (B) With ICG-PEG 0 Min 1 2 Optical absorption (cm) 3 Max Min Optical absorption (cm) 3 Max Speckle free High resolution: 60 μm High sensitivity: ~fmol (C) B A (D) Openskull photo (cm) 3 Min Differential absorption Max Optics Letters 8, 608 (2004)

32 Monitoring of of Dynamic Optical Absorption of of Nanoshells Absorption (a.u.) rd inj. 2nd inj. 1st inj. Baseline Time (min) Nano Letters 4, 1689 (2004)

33 80% Max Functional Photoacoustic Imaging of of Tumor Hypoxia: Nude mouse with a U87 glioblastoma xenograft in in the brain 1cm 60% 40% 20% Hemoglobin oxygen saturation (SO 2 ) Total hemoglobin concentration (HbT) 80 Normal Tumor 80 Normal Min SO 2 (%) SO 2 (%) Tumor Animal number Total hemoglobin concentration

34 Molecular Photoacoustic Imaging of of Integrin Planar fluorescence imaging 1 cm Max Fluorescence Min Molecular photoacoustic tomography Max 1 cm Molecular contrast (IRDye800 + peptide) Photograph Microfluorescence image ~3 mm below scalp surface Min Histology 1 cm

35 Spatial Resolution versus Bandwidth in in Photoacoustic Tomography (a) (b) (c) (d) Center freq.: 3.5 MHz 10 MHz 20 MHz Open-skull photo Resolution: 210 μm 60 μm 30 μm Physics in Med. Biol. 49, 1329 (2004)

36 Deeply Penetrating Photoacoustic Tomography with NIR Excitation & ICG Contrast 5.2 cm deep 5 mm Optics Letters 30, 507 (2005)

37 Reflection-mode Confocal Photoacoustic Microscopy: Illustration Sphere Photoacoustic signal Surface Sphere Time

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

39 Laser Tunability: nm Repetition rate: 10 Hz Pulse width: 6.5 ns System Parameters Optical fiber: 0.6 mm diameter Energy per pulse: 0.2 mj Energy density at focus: ~6 mj/cm 2 <20 mj/cm 2 (ANSI safety limit) High-frequency ultrasound transducer Center frequency: 50 MHz Nominal bandwidth: 70% of 50 MHz NA:

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

41 Dark-field Confocal Photoacoustic Microscopy: Multi-wavelength Functional Imaging nm nm Y axis [mm] Y axis [mm] nm nm Y axis [mm] Y axis [mm] X axis [mm] X axis [mm]

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

43 Imaging of of Tumor Angiogenesis In In Vivo 7 days post subcutaneous inoculation of CT26.WT tumor in a 20-g BALB/c mouse Tumor 1 mm

44 Longitudinal Imaging of of Tumor Angiogenesis In In Vivo Pre inoculation 3 rd day post inoculation 6 th day 1 mm Subcutaneously inoculated BR 7 C 5 tumor in a 200-g Sprague-Dawley rat

45 Imaging of of Skin Burn in in Pigs Acute thermal (175 o C, 20 s) burn in pig skin in vivo. Postmortem imaging at 584-nm optical wavelength. Photograph Healthy tissue Coagulated tissue Photoacoustic image B-scan image Hyperemic bowl 1 mm 1 mm Hyperemic ring Histology Hyperemic bowl 1 mm PA amplitude [a.u.] J Biomed Optics 11, (2006). 0 Burn depth ~1.7 mm Hyperemic bowl Skin surface Distance [mm]

46 Imaging of of Skin Burns of of Various Depths Acute thermal (150 o C, various times) burn in pig skin in vivo. Postmortem imaging at 584-nm optical wavelength. 5 s 10 s 1 mm 20 s 30 s J Biomedical Optics 11, (2006)

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

48 Total hemoglobin Hemodynamics In In Vivo (578, 584, 590, and 596 nm) Oxygen saturation Arteries and veins 1 mm Change in oxygenation Imaged SO 2 1 Artery 0.8 Vein 0.6 Hypoxia Normoxia Hyperoxia Physiological states Appl. Phys. Lett. In press (2007)

49 Photograph Melanoma Imaging of of Melanoma In In Vivo Composite photoacoustic image acquired at 584 and 764 nm Melanoma B-scan image at 764 nm Melanoma Histology 1 mm Melanoma Movie 1 mm Surface rendering Contrasts: Vessel: 13 Melanoma: 69 z x y Skin surface 3 mm Nature Biotech. 24, 848 (2006). 8 mm 8 mm

50 In In Vivo Genetic Imaging: Gene Expression in in Gliosarcoma Tumor in in Rat 1. LacZ (gene) 2. Beta-galactosidase (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 in press (2007)

51 Imaging of of Nanoshells around a Tumor In In Vivo 0 Original image 0 Focusing enhanced image (SAFT+CF) 1 1 y (mm) Vessels Tumor y (mm) Nanoshells x (mm) x (mm) In collaboration with Nanospectra

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

53 Deep Reflection-Mode Photoacoustic Imaging System: Schematic Prism Y X Z Concave lens Spherical conical lens Optical condenser US transducer Sample (A) Schematic Laser source: Wavelength: 804 nm Pulse width: <15 ns Repetition rate: 10 Hz (B) Light path Transducer: Frequency: 5 MHz or 10 MHz Focal length: 1 Aperture: 0.75 diameter f-number:

54 SNR and Resolution versus Depth SNR [db] (A) SNR vs imaging depth 10 MHz 5 MHz Depth [mm] Object: Human hair (50 μm) (B) Axial resolution vs imaging depth (C) Imaging depth Medium: 1% Intralipid with porcine gelatin (μ s =10 cm -1 ) Pixel count (depth/resolution): 5 MHz transducer: 127 (19.5 mm/153 μm) 10 MHz transducer: 150 (19.5 mm/130 μm) Photoacoustic microscope: 200 (3 mm/15 μm) Axial resolution [μm] MHz 10 MHz Depth [mm] 38 mm 30 mm 17 mm 30mm 23mm Surface Horse Horse hair hair Rubber rubber In chicken tissue SNR: 37 db (17 mm) 24 db (30 mm) SAFT 30 times average 5 MHz transducer

55 In In Vivo Photoacoustic Image of of Brain Cortex of of a Rat: En Face Image (A) Noninvasive photoacoustic image Fissura transversa (B) Invasive photo of brain cortex Fissura transversa Blood vessels Blood vessels Blood vessels Middle cerebral artery Middle cerebral artery 2mm 2mm

56 Noninvasive Photoacoustic Image of of a Rat Spleen: Depthwise En Face Images (A) Noninvasive MAP image of spleen (B) Invasive photo of spleen (B) Spleen Stomach Spleen Stomach 2mm 2mm (C) B-scan image (C) Organs Stomach Spleen Spleen D Stomach 2mm 2mm

57 Noninvasive Photoacoustic Image of of a Rat Spleen: Depthwise En Face Images Spleen A B C Spleen Spleen Depth: 2mm Depth: ~2mm Depth: ~2.6mm D E F Spleen Spleen Depth: ~3.2mm G Depth: ~3.8mm Invasive photo Depth: ~4.4mm

58 Modern High-resolution Optical Microscopy (Depth // Resolution > 100) Modality Year Depth Contrast Confocal microscopy 1970s ~0.5 mm Scattering, fluorescence Two-photon microscopy 1990s ~0.5 mm Fluorescence Optical coherence tomography 1990s ~1 mm Scattering, polarization Dark-field confocal photoacoustic microscopy 2005* ~3-30 mm, scalable Absorption Optics Letters 30, 625 (2005). Nature Biotech. 24, 848 (2006)

59 Photoacoustic Tomography with Optical Sensing of of Pressure Paul Beard s Group, UCL

60 Photoacoustic Imaging of of the Breast (Fairway Medical): Photograph of of System Alexander Oraevsky s Group

61 Photoacoustic Imaging of of the Breast (Fairway Medical): Schematic of of System LASER BEAM IMAGE LOIS DISPLAY Data acquisition Image reconstruction

62 Photoacoustic Imaging of of the Breast: (Fairway Medical): Images X-ray Mammogram Tumors detected: 29/

63 Photoacoustic Imaging of of the Breast (University of of Twente) aperture to accommodate breast ultrasound detector + electronics light delivery system + scanning system laser remote controller laser power supply laser safety curtain laser Srirang Manohar et al Phys. Med. Biol. (2005) 50, PC carrying DAQ cards, DIOT cards, serial ports etc

64 Instrument Specifications Light source: Nd:YAG laser; 1064 nm; 5 ns pulse widths; 10 Hz rep rate Detector: 590 elements; 1 element activated at a time;1 MHz central freq.; BW 130 % Image reconstruction: Phased array (delay and sum); voxel size 0.5 mm; surface signal kept out. Resolution is 3.2 (axial) and 3.4 (lateral) at a depth of 30 mm S. Manohar et al Phys. Med Biol. (2005) 50, S. Manohar et al J. Biomed. Opt. (2004) 9,

65 Case Case11 MIP image top view Tumor extent is 35 x 30 mm Pathologically determined cancer size: 32 mm Srirang Manohar et al., in preparation. S. Manoharhttp://oilab.seas.wustl.edu et al manuscript in preparation (2007) -- 65

66 Slices starting at at 9 mm in in steps of of 2 mm S. Manohar et al manuscript in preparation (2007)

67 Outline Motivation and challenges Ultrasound-modulated optical tomography (UOT) Laser-induced Photoacoustic tomography (PAT) RF-induced thermoacoustic tomography (TAT) Summary

68 Deeply Penetrating Thermoacoustic Tomography 40 Rotating Transducer 10 cm 6 cm Muscle Imaging plane Fat Horizontal axis y (mm) Two Absorbers 12 cm RF Horizontal axis x (mm) Deep penetration 0.5 mm resolution No speckle artifacts

69 Experimental System for Thermoacoustic Tomography Water tank Ultrasonic transducers Stepper motor Waveguide Microwave generator Amplifiers and scope

70 RF Penetration 100 Normal breast tissue Penetration depth (cm) 10 1 Malignant breast tissue Muscle Fat Frequency (MHz)

71 Thermoacoustic Image of of a Mastectomy Specimen 1 cm Intensity (a.u.) x axis (cm) 11 cm diam. X 9 cm thick ~5:1 contrast Invasive lobular carcinoma Tech. in Cancer Res. & Treatment 4, 559 (2005)

72 Hemispherical Detection Geometry RF pulse Breast with tumor Coupling fluid Arc Array Robert Kruger s Group

73 Summary Physically combining ultrasonic and electromagnetic waves (light & RF) provides improved spatial resolution compared with optical/rf imaging, new contrast mechanisms compared with ultrasound imaging. Spatial resolution is determined by the ultrasonic parameters. Spatial resolution is scalable with the ultrasonic parameters. Contrast is provided by the electromagnetic properties. Deep (~cm) tissue imaging can be achieved. Speckle artifacts do not exist. Functional imaging can be accomplished with endogenous contrast. Molecular imaging can be accomplished with exogenous contrast agents. Non-ionizing radiation is used. Costs are comparable with those of ultrasound systems

74 Funding Sources ACTIVE NIH/NCI R01 CA R33 CA R01 CA NIH/NIBIB R01 EB NIH/NINDS R01 NS46214 (BRP) RECENTLY COMPLETED NIH CA83760 CA71980 CA68562 EB NSF US Army Whitaker Foundation

75 Chapters 1. Introduction to biomedical optics 2. Single scattering: Rayleigh theory and Mie theory 3. Monte Carlo modeling of photon transport 4. Convolution for broad-beam responses 5. Radiative transfer equation and diffusion theory 6. Hybrid model of Monte Carlo method and diffusion theory 7. Sensing of optical properties and spectroscopy 8. Ballistic imaging and microscopy 9. Optical coherence tomography 10. Mueller optical coherence tomography 11. Diffuse optical tomography 12. Photoacoustic tomography 13. Ultrasound-modulated optical tomography

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