PHOTOACOUSTIC TOMOGRAPHY: Ultrasonically Breaking …

OILAB.SEAS.WUSTL.EDU -- 1

© 7/19/2012, LV WANG

Lihong V. WangGene K. Beare Distinguished Professor

Optical Imaging LaboratoryDepartments of Biomedical Engineering,

Radiology, andElectrical & Systems EngineeringWashington University, St. Louis

PHOTOACOUSTIC TOMOGRAPHY:Ultrasonically Breaking through the Optical Diffusion Limit

PHOTOACOUSTIC TOMOGRAPHY:Ultrasonically Breaking through the Optical Diffusion Limit

Email: [email protected]


© 7/19/2012, LV WANG

Financial Interest Disclosure and Funding SourcesFinancial Interest Disclosure and Funding Sources

FINANCIAL INTEREST• Microphotoacoustics, Inc.• Endra, Inc.

ACTIVE GRANTS• NIH/NCI

U54 CA136398/NTR Ctr: SLN PA R01 CA134539: Chemo TAT/PAT R01 CA157277: PA endoscopy

• NIH/NIBIB R01 EB000712: PAM R01 EB008085: DOT/PAT R01 EB010049: Brain TAT

COMPLETED GRANTS• NIH

R21 CA83760: SLT R01 CA71980: UOT R29 CA68562/FIRST: UOT R21 EB000319: MOCT R01 EB000712: PAM R33 CA094267: UOT R01 CA092415: OCT R01 NS46214/BRP: PACT R01 CA106728: OIR

• NSF BES-9734491/CAREER: UOT

• DOD Breast Program DAMD17-00-1-0455: TAT

• Whitaker Foundation RG-96-0221: OIR


© 7/19/2012, LV WANG

OutlineOutline

• Motivations and challenges

• Photoacoustic computed tomography

Circular geometry

Linear geometry

• Photoacoustic microscopy

Acoustic resolution

Optical resolution

• Discussion and summary


© 7/19/2012, LV WANG

Motivations for Biomedical OpticsMotivations for Biomedical Optics• Safety — Non-ionizing, non-carcinogenic (hν ~ 2 eV)• Physics — Molecular interaction• Optics — Light probes essentially all molecules

Nucleic acids: DNA & RNA Carbohydrates: Glucose, cellulose Lipids: Fat Proteins: Oxy- & deoxy-hemoglobin, cytochrome c Others: Melanin, water, dye, nanoparticles

• Imaging — Functional, metabolic, and molecular contrasts Concentration of hemoglobin (angiogenesis) Oxygen saturation of hemoglobin (hyperoxia, normoxia, or hypoxia) Cell nuclei (label-free in vivo histology) Blood flow (Doppler) Metabolic rate of oxygen (hyper-metabolism) Biomarkers: Integrin, VEGF, HER2, etc. Reporter genes

• Manipulation — Controlled activation Optogenetics Nerve stimulation

• Therapeutics — Low systemic toxicity Photodynamic therapy (PDT) Photothermal therapy


© 7/19/2012, LV WANG

Fundamental Challenges in High-resolutionOptical Imaging: Diffraction and Diffusion

Fundamental Challenges in High-resolutionOptical Imaging: Diffraction and Diffusion

• Diffraction (wave phenomenon)

Limits the spatial resolution of ballistic imaging (planar, confocal,

& two-photon microscopy, optical-coherence tomography).

Has been overcome for super-resolution imaging (PALM/STORM).

• Diffusion (scattering phenomenon)

Limits the penetration of ballistic imaging to ~1 mm in skin.

Has been overcome for super-depth imaging (PAT).

Diffusion limit ~ 1 mm(Transport mean free path)

Laser

Ballistic decay constant ~ 0.1 mmDiffuse decay constant ~ 10 mm


© 7/19/2012, LV WANG

Short-pulsed Laser-induced Initial Photoacoustic PressureShort-pulsed Laser-induced Initial Photoacoustic Pressure

in /mt coefficien absorption Optical

rise] re[Temperatu

pressure] ticphotoacous [Initial 0

a

T

p


© 7/19/2012, LV WANG

OutlineOutline



Circular geometry

Linear geometry


Acoustic resolution

Optical resolution



© 7/19/2012, LV WANG

Object

Photoacoustic Computed Tomography in Circular GeometryPhotoacoustic Computed Tomography in Circular Geometry

(1) ns laser pulse (<ANSI limit: e.g., 20 mJ/cm2)

(4) Ultrasonic detection(optical scatter/1000)

(3) Ultrasonic emission (~ mbar)

(2) Light absorption & heating (~ mK)

X Wang et al, Nature Biotech 21, 803, 2003

1 mK 8 mbar= 800 Pa!


© 7/19/2012, LV WANG

Non-invasive Functional Photoacoustic Imaging of RatWhisker Stimulation In Vivo: Hemodynamic Response

Non-invasive Functional Photoacoustic Imaging of RatWhisker Stimulation In Vivo: Hemodynamic Response

Left-whisker stimulation

0 0.5 1.0 2.0

2.0

1.5

1.0

0

(cm)

(cm

)

Differential absorption MaxMin

0.5

1.5 0 0.5 1.0 2.0 2.

0 1.

5 1.

0 0

(cm)

(cm

) 0.

5 1.5

Right-whisker stimulation

X Wang et al, Nature Biotech 21, 803, 2003

Through intact scalp and skullIn-plane resolution: 0.2 mm


© 7/19/2012, LV WANG

Growth of Photoacoustic Tomography:Data from Conference on Photons plus Ultrasound

Chaired by Oraevsky and Wang

Growth of Photoacoustic Tomography:Data from Conference on Photons plus Ultrasound

Chaired by Oraevsky and Wang

*

* Largest in 20,000-attendee Photonics West


© 7/19/2012, LV WANG

Multiscale Photoacoustic Tomography In Vivo with Consistent ContrastMultiscale Photoacoustic Tomography In Vivo with Consistent Contrast

LA: Linear arrayPA: PhotoacousticCT: Computed

tomography

AR: Acoustic resolutionMac: Macroscopy

PAM: PA microscopyOR: Optical resolutionSM: Sub-micronSW: Sub-wavelength

W, Nature Phot 3, 503, 2009W, S Hu, Science 335, 1458, 2012

1. Enable systems biology research at multiple length scales

2. Accelerate translation of microscopic lab discoveries to macroscopic clinical practice

Lateral resolutionAxial resolution

SM-PAM

OR-PAM

AR-PAM

LA-PACTAR-PAMac

SW-PAM

Depth-resolution ratio = 200!

Organelle Cell Tissue Organ

10-1 100 101 102 10310-2

10-1

100

101

102

Resolution (m)

Pene

trat

ion

in ti

ssue

(mm

)


© 7/19/2012, LV WANG

512-Element Ring Ultrasonic Array512-Element Ring Ultrasonic Array

J Xia, unpublished. Collaboration: Q Zhu@UConn


© 7/19/2012, LV WANG

In VivoWhole‐body Photoacoustic Computed Tomography of a MouseIn VivoWhole‐body Photoacoustic Computed Tomography of a Mouse

Bar: 3 mm

J Xia et al, unpublished.

Bar: 5 mm

KidneyKidney

Spleen

Intestine Intestine

Spinal cord

Vena cave

Colon Portal vein

Backbone muscle

In-plane resolution:100 microns


© 7/19/2012, LV WANG

OutlineOutline



Circular geometry

Linear geometry


Acoustic resolution

Optical resolution



© 7/19/2012, LV WANG

Hand-held Photoacoustic/Ultrasonic Imaging Probeusing Modified Clinical Ultrasound Scanner

Hand-held Photoacoustic/Ultrasonic Imaging Probeusing Modified Clinical Ultrasound Scanner

US probe

Fiber bundles

US Scanner

Patient bed

US system

DAQPA

imageUSimage

Hand-held PA/US probe

C Kim, T Erpelding et al, Biomed Opt Exp 1, 278, 2010Collaboration: Philips Research


© 7/19/2012, LV WANG

Multiscale Photoacoustic Tomography In Vivowith Consistent Contrast



tomography




SM-PAM

OR-PAM

AR-PAM

LA-PACTAR-PAMac

SW-PAM

Depth-resolution ratio = 200


10-1 100 101 102 10310-2

10-1

100

101

102

Resolution (m)

Pene

trat

ion

in ti

ssue

(mm

)



© 7/19/2012, LV WANG

Azimuth (cm)

Dep

th (c

m)

-1 0 1

0

1

2

3

4

5

6 0

5

10

15

20

In Vivo Photoacoustic Image of Human Breast:Pre-Injection of Methylene Blue

In Vivo Photoacoustic Image of Human Breast:Pre-Injection of Methylene Blue

Erpelding, Garcia-Uribe, Jiang, Appleton, Margenthaler et al, unpublished. Collaboration: Philips Research

Wavelength: 650 nmLaser fluence: 10 mJ/cm2

(1/2 ANSI safety limit)

Tumor


© 7/19/2012, LV WANG

In Vivo Photoacoustic Tomography of Sentinel Lymph Node (SLN) in Human Breast: Post Injection of Methylene Blue

In Vivo Photoacoustic Tomography of Sentinel Lymph Node (SLN) in Human Breast: Post Injection of Methylene Blue

Erpelding, Garcia-Uribe, Appleton, Margenthaler et al, unpublished. Collaboration: Philips Research

Clip

Photoacoustic (PA) Ultrasonic (US)

Radiographic

US

PA


© 7/19/2012, LV WANG

OutlineOutline



Circular geometry

Linear geometry


Acoustic resolution

Optical resolution



© 7/19/2012, LV WANG

Dark-field Confocal Photoacoustic Microscopy:3 mm Penetration at 50-MHz Ultrasonic FrequencyDark-field Confocal Photoacoustic Microscopy:

3 mm Penetration at 50-MHz Ultrasonic Frequency

yz

x

Sample holder

Motor driverTranslation stages

Base

Photodiode

Amplifier

Heater & temperature controller

AD

Computer

Tunable laser

Conical lens

Mirror

Ultrasonic transducer

Dual foci

Sample

Optical illumination

Annular illumination with a

dark center

Nd:YAG pump laser

K Maslov et al, Optics Letters 30, 625, 2005H Zhang, K Maslov et al, Nature Biotech 24, 848, 2006H Zhang, K Maslov, W, Nature Protocols 2, 797, 2007


© 7/19/2012, LV WANG




tomography




SM-PAM

OR-PAM

AR-PAM

LA-PACTAR-PAMac

SW-PAM



10-1 100 101 102 10310-2

10-1

100

101

102

Resolution (m)

Pene

trat

ion

in ti

ssue

(mm

)



© 7/19/2012, LV WANG

In Vivo Photoacoustic Microscopy of Human Skin and MelanomaIn Vivo Photoacoustic Microscopy of Human Skin and Melanoma

Photo En face PAM

B-scan PAM @ 584 nm

C Favazza et al, J Biomed Opt 16, 016015, 2011W Xing, unpublished.Collaboration: L. Cornelius

Epidermis

Epiderm.-derm. junction

Dermis Subpapillary plexus

Stratum corneum

1 mm1 2

3 4 5

1 mm

123

45 PAM of

melanoma


© 7/19/2012, LV WANG

In Vivo Molecular Photoacoustic Imaging of B16 Melanomain a Rat Using Targeted Gold Nanocages (AuNCs)

In Vivo Molecular Photoacoustic Imaging of B16 Melanomain a Rat Using Targeted Gold Nanocages (AuNCs)

C Kim et al, ACS Nano 4, 4559, 2010. Nature Mat 8, 935, 2009. Collaboration: Y Xia

[Nle4,D-Phe7]-α-MSH-AuNCs 38 ± 3 (%) at 6 hr (3X control)

PEG-AuNCs 13 ± 1 (%) at 6 hr

Sensitivity :~ 5000 AuNCs / voxel

MSH: melanocyte-stimulating hormone

2mm

0 h 3 h

Tumor

6h

Tumor

0 h 3 h Tumor 6 h Tumor Incr

ease

in P

A s

igna

l [%

]

0

10

20

30

40

50


© 7/19/2012, LV WANG

Photoacoustic Endoscopy of Rabbit Esophagus In VivoPhotoacoustic Endoscopy of Rabbit Esophagus In Vivo

Optical fiber

Scanningmirror

NS N

S

MagnetsUltrasonictransducer

Micromotor

Photoacoustic

Ultrasonic

Axial resolution: 55 micronsLateral resolution: 80 micronsDiameter of probe: 3.8 mm or 2.5 mmUltrasonic frequency: 36 MHz

Lung Trachea

J Yang, Nature Med, acceptedJ Yang et al, Optics Letters 34, 1591, 2009Collaboration: Zhou & Shung @ USC


© 7/19/2012, LV WANG

OutlineOutline



Circular geometry

Linear geometry


Acoustic resolution

Optical resolution



© 7/19/2012, LV WANG

Optical Resolution PhotoacousticMicroscopy: 1.2 mm Penetration

Optical Resolution PhotoacousticMicroscopy: 1.2 mm Penetration

CL: Condenser lensPH: PinholeOL: Objective lensUT: Ultrasonic transducerDL: De-aberrating lensIP: Isosceles prismAL: Acoustic lens

CL

PH

OLDL

AL

UTIP

LightSound

• Optic NA = 0.1• Lateral resolution = 2.6 µm

• Acoustic NA = 0.45• Center f ~ 85 MHz• Axial resolution < 15 µm

K Maslov et al, Optics Letters 33, 929, 2008

Light transmitting & sound reflectinginterface


© 7/19/2012, LV WANG




tomography




SM-PAM

OR-PAM

AR-PAM

LA-PACTAR-PAMac

SW-PAM



10-1 100 101 102 10310-2

10-1

100

101

102

Resolution (m)

Pene

trat

ion

in ti

ssue

(mm

)



© 7/19/2012, LV WANG

In Vivo Optical-Resolution Photoacoustic Microscopyof Mouse Ear: 2.6 Micron Lateral Resolution

In Vivo Optical-Resolution Photoacoustic Microscopyof Mouse Ear: 2.6 Micron Lateral Resolution

500 µm

5 mm x 5 mm x 0.45 mm

Oxygen saturation of hemoglobin

1

0

Capillary bed

RBCs

50 µm

S Hu et al, Optics Lett 36, 1134, 2011


© 7/19/2012, LV WANG

In Vivo Photoacoustic Microscopy of Human Finger CuticleIn Vivo Photoacoustic Microscopy of Human Finger Cuticle

S Hu et al, unpublished

0.3

1.0

sO2Capillary

loop

Eponychium 0.5 mm

1 mm

Cross section


© 7/19/2012, LV WANG

Photoacoustic Microscopy ofSingle Red Blood Cells and Oxygen Release In Vivo

Photoacoustic Microscopy ofSingle Red Blood Cells and Oxygen Release In Vivo

LD Wang & K Maslov et al, unpublished.

Hemoglobin (20 volumetric images/second)Oxygen saturation of hemoglobin (sO2)

1 H

z B

-sca

n

20 H

z B

-sca

n


© 7/19/2012, LV WANG

OutlineOutline



Circular geometry

Linear geometry


Acoustic resolution

Optical resolution



© 7/19/2012, LV WANG

Time-reversed Ultrasound-encoded (TRUE) Optical FocusingTime-reversed Ultrasound-encoded (TRUE) Optical Focusing

X Xu et al, Nature Photonics 5, 154, 2011

1. Virtual guide star2. Arbitrary focal

position3. Label free4. Applications in

• Imaging (fluorescence)

• Sensing(oxygenation)

• Manipulation(opto-genetics)

• Therapy(photodynamic therapy)

PCM: phase conjugate mirror DC: un-modulated lightTR: time-reversedUE: ultrasonic encoding


© 7/19/2012, LV WANG

ConclusionsConclusions1. Optical excitation and ultrasonic detection integrated2. Diffusion limit (~1 mm) broken: depths up to 7 cm reached3. Single capillaries, cells, and organelles resolved in vivo (220 nm res)4. Multiscale imaging achieved by scaling depth and resolution5. Background-free detection built-in (no absorption, no signal)6. Sensitivity to optical absorption maximized to 100%7. Either non-fluorescent or fluorescent pigments detected8. Multiple chromophores resolved spectrally9. Functional imaging derived from endogenous chromophores10. Molecular imaging enabled by targeted contrast agents11. Reporter genes imaged12. Doppler imaging of flow demonstrated13. Data acquired fast: 1 s for 1.5 mm depth; 100 s for 15 cm depth14. Speckle artifacts avoided15. Non-ionizing radiation used16. Costs kept relatively low


© 7/19/2012, LV WANG

ChallengesChallenges

• Ultrasound reflection by gas cavities and bones• Ultrasound attenuation by lung parenchyma• Ultrasound attenuation and aberration by adult skulls• Insensitivity to optical scattering contrast• Light delivery at even greater depths

Scattering does not destroy photons Ballistic decay constant (1/e) ~ 0.1 mm Diffuse decay constant (1/e) ~ 1 cm Absorption decay constant (1/e) ~ 10 cm


© 7/19/2012, LV WANG

Credit to Lab MembersCredit to Lab Members

CURRENTAlejandro Garcia-UribeAmos DanielliAmy Winkler Arie KrumholzBin HuangBin RaoChi ZhangChris FavazzaDa Kang YaoGuo LiHaixin KeHonglin LiuJoon Mo YangJun XiaJunjie YaoKonstantin Maslov

RECENT ALUMNIChanghui LiChul-Hong KimHao ZhangHui FangKwanghyun SongLiang SongManojit PramanikMinghua XuRoger Zemp Xueding Wang Yuan Xu

Washington U

BME Dept

CURRENTLidai WangLiming NiePuxiang LaiRameez ChatniRobert BerrySong HuWenxin XingXiao XuXin CaiYan LiuYu WangYuchen YuanYuta SuzukiZhen JiangZhun XuZijian Guo


© 7/19/2012, LV WANG

ChaptersChapters1. Introduction to biomedical optics2. Single scattering: Rayleigh theory and

Mie theory 3. Monte Carlo modeling of photon

transport4. Convolution for broad-beam responses5. Radiative transfer equation and

diffusion theory6. Hybrid model of Monte Carlo method

and diffusion theory7. Sensing of optical properties and

spectroscopy8. Ballistic imaging and microscopy9. Optical coherence tomography10. Mueller optical coherence tomography11. Diffuse optical tomography12. Photoacoustic tomography13. Ultrasound-modulated optical

tomography

2007

Homework solutions provided for instructors

Joseph W. Goodman Book Writing Award

Source codes


© 7/19/2012, LV WANG

• JOB OPENINGS: Postdoctoral Predoctoral

• Recorded presentations available on our web

• Please visit our web athttp://oilab.seas.wustl.edu


© 7/19/2012, LV WANG

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PHOTOACOUSTIC TOMOGRAPHY: Ultrasonically Breaking …