Optical coherence tomography Lecture 3 – Parametric ... · Optical + Biomedical Engineering...

Optical coherence tomography Lecture 3 – Parametric contrast, and delivery

systems: endoscopes and needles David Sampson

Optical + Biomedical Engineering Laboratory School of Electrical, Electronic and Computer Engineering,

& Centre for Microscopy, Characterisation & Analysis

The University of Western Australia

Abbe School of Photonics, 11 June 2013 Sampson, Lecture 3, OCT

Take home messages •  Basic imaging technology in place

-  Speed and sensitivity have enabled 3D

•  3D opens up many possibilities

•  Imaging protocols – take care to avoid artefacts

•  Accurate comparison with histology is vital but still rare

•  Many impediments, but two stand out… -  Scattering contrast is low

-  Speckle corrupts image

•  Speckle – the interplay of wavefront aberration and multiple scattering not well understood


Roadmap for what OBEL does •  Medical microscopy

Optical coherence tomography

•  What you can do on the surface “Atlas” studies: lymph nodes, parametric methods: attenuation, PS-OCT, lymph nodes, burns vasculature

•  What you can do with catheters Human upper and lower airways

•  What you can do with needles Needle design, OCT+fluorescence multimodality, animal airways, tumour margins: breast cancer

•  Elastography – alternative contrast Emerging methods, phantoms, modelling, breast cancer


How much does the scattering coefficient of tissues typically vary by?

μs = 2-20 mm-1

…which is a mean free path 50-500 μm

Scattering contrast is modest

Contrast, contrast, contrast


OCT of human axillary lymph nodes Involved lymph node - ductal carcinoma

–  Well delineated metastasis –  Remainder of node is uninvolved –  T: tumour, C: cortex, PC: paracortex, M: medulla

Histology (H&E stain) OCT

McLaughlin et al., Cancer Research 79, 2579-2584, 2010


Involved lymph node − ductal carcinoma –  Diffuse malignant cells –  T: Tumour, dark in OCT –  C: Residual cortex, light grey in OCT

Histology (H&E stain) OCT

OCT of human axillary lymph nodes McLaughlin et al., Cancer Research 79, 2579-2584, 2010


•  How can we get more constrast?

•  If we have 3D, try imaging an optical parameter, parametric imaging

•  This trades off depth for enhanced sensitivity

•  Flavours of optical properties include:

-  Scattering and absorption – μs, μa, g

-  Birefringence – Δn = ne – no



Parametric OCT imaging to enhance contrast

McLaughlin et al., MICCAI 2009: Proc. Medical Image Computing and Computer-assisted Intervention; Lecture Notes in Computer Science 5762:657-664, 2009; and J. Biomed. Opt. 15, art. 046029, 2010

OCT Parametric OCT H&E histology

1mm 1mm 1mm

Cancer

Map A scan slope –  Measures local attenuation –  Info in 3D volume mapped to

2D to improve sensitivity to…


Cancerous lymph node –  Parametric images show better contrast of healthy vs cancerous

tissue –  Circled areas show residual healthy cortex

H&E histology μ parametric image OCT en face – best match

McLaughlin et al., “Parametric imaging of cancer with optical coherence tomography”, Journal of Biomedical Optics, 15(4):046029, 2010

Scale bar 1mm

Parametric OCT – qualitative contrast

Optical pathlength 0.5 mm


Cancerous lymph node –  Cancerous areas – high attenuation (bright) –  Healthy cortex – low attenuation (dark)

H&E histology Parametric image OCT en face – best match

McLaughlin et al., “Parametric imaging of cancer with optical coherence tomography”, Journal of Biomedical Optics, 15(4):046029, 2010

500 m

•  Images shown are qualitative – reflectance not calibrated •  Can we convert parametric imaging to a quantitative modality?

Parametric OCT – qualitative contrast

Optical pathlength 0.5 mm


Contrast mechanism – attenuation in depth –  Given a 3D data set, estimate μt at each x,y over a range z –  If tissue is homogeneous, single scattering will follow

modified “Beer’s Law”

Core idea: Condensing 3D data to 2D to enhance sensitivity to detecting cancer

Parametric attenuation

image

Parametric OCT – quantitative contrast

McLaughlin et al., MICCAI 2009: Proc.

Medical Image Computing and

Computer-assisted Intervention; Lecture

Notes in Computer Science 5762:657-664,

2009

R(z) = ρe-2μtz

loge R(z)

Slope μt


How to generate parametric attenuation images

Parametric image − extract μ (x,y)

Moving window (x,y)

Assume homogenous: apply fit over (e.g., 200 μm) window


Moving window (x,y)

Parametric image − extract μ (x,y) Assume homogenous: apply fit over (e.g., 200 μm) window



Moving window (x,y)

Select depth(z)





Moving window (x,y)

Select depth(z)



Method to extract attenuation coeffiction μt

1. A-scan 2. Reflectance profile R(z)

Pre-processing+

Fit to model Calibration

+Correction

3. Extract μt

Abbe School of Photonics, 11 June 2013 Sampson, Lecture 3, OCT 17

Method: Axial calibration and correction Confocal axial response CCCCCCCCoonnffooccaall aaxxiiaaaaaaaaaa

Reference scan function

OCT objective lens focus function

Reference arm coupling efficiency

Microsphere suspension,

0.46 μm diameter,

μs ≈ 0.7 mm-1, g = 0.7

Correction profiles


Quantitative parametric OCT - Signatures •  Healthy lymph node •  Calibrated reflectance profile

R(z) •  Extract absolute μt

240 μm

μt

H&E histology OCT (en face)

•  Pathologist identifies pure

tissue types –  Paracortex –  Medullary sinuses –  Fibrous capsule


Axillary lymph node   Paracortex   Medullary sinuses

  Fibrous capsule   Inactive primary follicular tissue

Scale bars: 1 mm

OCT

Quantitative μt(x,y) Segmented by μt(x,y) H&E histology


Axillary lymph node, Example #2   Paracortex   Medullary sinuses

  Necrosis   Calcification

Histology OCT μt(x,y)

  Fibrous capsule   Cortex

Scale bars: 1 mm


Lymph node – measured attenuation coefficients

Lymphoid tissues can be distinguished with quantitative parametric imaging of the attenuation coefficient

L. Scolaro et al. “Parametric imaging of the local attenuation coefficient in human axillary lymph nodes assessed using optical coherence tomography” Biomed. Opt. Express 3(2), 366–379, (2012)


OCT (en face)

  Paracortex   Medullary sinuses   Fibrous capsule

Scale bars: 1 mm

Quantitative μt(x,y) Segmented by μt(x,y)

Quantitative parametric OCT L. Scolaro et al. “Parametric imaging of the local attenuation coefficient in human axillary lymph nodes assessed using optical coherence tomography” Biomed. Opt. Express, vol. 3, no. 2, pp. 366–379, (2012)

Take home: Promising, not yet convincing


Parametric attenuation imaging of burn scars

•  Removing effect of vessels important •  Scars are more transparent than normal skin •  Because their collagen contains more water









•  How can we get more constrast?

•  If we have 3D, try parametric imaging

•  Trade off depth for enhanced sensitivity

•  Flavours of optical properties include:





What can PS-OCT be used for?

•  Birefringence – magnitude and orientation –  Large-scale information on “micro-order of nanostructure”

Examples –  Nerve fibre layer in the retina (glaucoma) –  Collagen: Scarring in skin, cornea; in atherosclerotic plaque,

abnormality in the cornea, organisation in cartilage –  Muscle: dystrophies, airways

•  Scattering (less evidence)

–  Small-scale information about scatterers and their local environment

Examples –  Dental caries –  Oesophagus – distinguishing normal, neoplastic and scar tissue


Musculoskeletal tissues exhibit birefringence

Jacoby et al., Development, 2009, 136, 3367-3376

Normal, undamaged, muscle

Necrotic muscle

Decreases when disease processes damage tissue


•  Duchenne muscular dystrophy (DMD)

•  Can we characterise tissue necrosis or regeneration in the mdx mouse model in vivo?

•  If so, a single animal could be tracked in time – needs fewer animals, less variability

•  Can we characterise DMD in humans?

C57 control mouse

Collaboration: Grounds Lab School of Anatomy, Physiology & Human Biology, The University of Western Australia

Normal Dystrophic

100μm 100μm

The Jackson Laboratory www.jax.org

DMD patient 12 years

mdx dystrophic mouse

Optical coherence tomography imaging of muscle


Klyen et al., J. Biomed. Opt., 13(1) 011003, 2008

EDL

EDL

TA

TA

x

x y

y

Histology:

Haematoxylin and Eosin-stained 5-μm tissue section

Optical coherence tomography:

en face, from 3D section

TA EDL

Tissue damage model – whole muscle autograft


100μm

250μm

500μm

Autograft surgical model of muscle damage

B. R. Klyen et al., JBO, 13(1): 011003 (2008)


mdx mouse model of muscular dystrophy – bulk

z

y x

B. R. Klyen et al., J. Biomedical Optics 16(7), 076013, 2011

Photograph 3D-OCT H&E-histology EBD-fluorescence

histology

Necrotic lesion

Disruption region EBD

accumulation

EBD fluorescence

EBD-fluorescence Microscopic indication of

permeable (leaky or necrotic) myofibres


Does the degree of polarisation change? –  DOP is a measure of the amount of polarised versus

unpolarised light –  If we illuminate with polarised light and detect single

backscattering, the DOP should remain unity –  Affected by many factors, but especially multiple scattering

Polarisation-sensitive OCT

What affects the polarisation state? –  Birefringence along optical path –  Scattering

Typical retardation over image – few radians, a small effect Δn = 10-3, λ = 1 μm, l = 1 mm, 2kΔnl = 4π

Orientation of axis of birefringence can also be important


Some points –  Stokes formalism or Jones calculus can be used –  To determine retardation/birefringence need only two independent measurements –  To determine birefringent axis orientation need another two

Could be full set of Stokes parameters

Could be amplitude and phase in orthogonal polarisations

–  To determine parameters at a given depth assumes parameters at shallower depths are known

Scenarios –  Determine full Müller matrix of tissue

•  Requires 16 independent measurements

–  Determine Stokes parameters of received light knowing Stokes parameters of input light

•  Requires 4 independent measurements

–  Determine Jones matrix •  Requires 4 independent measurements

How is polarisation described? Jones calculus ⎥

⎦

⎤⎢⎣

⎡=

in

inin

,

,

y

x

EE

Ε

⎟⎟⎟⎟⎟

⎠

⎞

⎜⎜⎜⎜⎜

⎝

⎛

=

in

in

in

in

in

VUQI

SStokes calculus

⎥⎦

⎤⎢⎣

⎡=

43

21in path, JJ

JJJ =in path,M

⎥⎥⎥⎥

⎦

⎤

⎢⎢⎢⎢

⎣

⎡

44434241

34333231

24232221

14131211

MMMMMMMMMMMMMMMM

Jscatterer Mscatterer

out path,out path, MJininpath,scattereroutpath,out ΕJJJΕ =

Sout = Mpath,outMscattererMpath,inSin


Poincaré sphere

Polarisation state described by Stokes parameters Q,U,V Normalised Stokes vectors lie on the unit (Poincaré) sphere Linear states on the equator, circular states at the poles


Polarisation on the Poincaré sphere •  Jones vector representation: complex amplitude and phase

•  Stokes vectors: Relative intensities Normalised

•  We can represent as a point in 3-D space – the Poincaré sphere

[ ]I,Q,U,V=S[ ]V,U,QI ˆˆˆˆ == SS

⎥⎦

⎤⎢⎣

⎡=

⎥⎥⎦

⎤

⎢⎢⎣

⎡=⎥

⎦

⎤⎢⎣

⎡Δ

−−

−

θ

θφ

φφ

φ

sincosi

ii

y

ix

y

x

eae

eaea

EE

xy

x

S

Partiallypolarised

1ˆ <S

Elliptical polarisationFully polarised

1ˆ =S

Right circularpolarisation


Instrumentation •  Ref path – equal signal on

both detectors •  Sample – independent of

axis orientations

{ }( ){ }⎟

⎟⎠

⎞⎜⎜⎝

⎛

−−−

−=

θδπδ

δδ

2expsinexpcos

S jj

RE

nretardatio=δnorientatio axis=θ What is the difficulty with a

fibre? Unknown polarisation state Varies with time

•  What happens in an ordinary OCT system and a birefringent sample?

•  Intensity modulation with retardation – why??


Polarisation-sensitive OCT – fibre optics

PBS: Polarising beam splitter PC: Polarisation controller PD: Photodetector

Co- (left) and cross- (right) polarised signal components

Be aware that there are various approaches trading off complexity with completeness in polarisation state


OCT v PS-OCT B-scan images OCT Retardance

φ(z) =2πn

λ2zΔn

•  Polarisation sensitive OCT B scan intrinsically an integral from the surface

•  A natural fit for parametric imaging


•  Straight OCT does not have enough contrast

•  In muscle tissue, try imaging birefringence

•  Birefringence depends on disease

•  Try parametric imaging of birefringence

Parametric polarisation-sensitive OCT


Parametric imaging requires automation

•  Clinical motivation – muscular dystrophy

•  PS-OCT to measure birefringence –  Undamaged muscle high birefringence –  Necrotic muscle low birefringence

•  Automated quantification algorithm –  Calculates percentage of necrotic tissue –  Addresses issues of:

• Phase wrapping • Phase noise

•  Pre-clinical validation


Birefringence Rate of change of phase retardation, φ, with depth, z

Phase retardation Angle between points on the Poincaré sphere

Birefringence from changes in polarisation

Δn =φ(z)

2z

λ2πn

Phase retardation, ϕ(z)

Stokes vector at depth z

Stokes vector at depth z0

φ(z) =2πn

λ2zΔn


Phase retardation •  Does not increase

monotonically with depth •  Wraps between [0, π]

Phase retardation – phase wrapping


Phase retardation, ϕ(z1)

Phas

e re

tard

atio

n, ϕ

(z)



Phase retardation, η(z2)

z0 z2z1 z4z3

z3

η(z3)

z4z8

z5 z6 z7 z8

z5

ϕ(z5)

z6

η(z6)

z7

η(z7)

Depth into tissue, z

Stifter et al., Opt. Express, 2010, 18, 25712-25725

Unwrap using a Hilbert-transform based technique


Phase precision Variance of phase retardation inversely related to OCT SNR

Noise reduction Averaging with kernel K(size m, n, o)Weighting by

Phase retardation – phase noise

)(SNR/2)(2 zz ≈φσ

)(/1)( 2 zzw φσ=

)),,(SNR/(22av zyxKmno ⊗×≈σ

Park et al., Opt. Lett., 2005, 30, 2587-2589


Quantification algorithm

For each A-scan in the imaging volume •  Spatially average Stokes vectors •  Calculate the phase-retardation •  Hilbert transform recover phase •  Perform phase unwrapping •  Weighted least squares linear fit

slope of phase with depth •  Calculate birefringence

Applying this over the whole volume gives a 2D map of birefringence

Δn =φ(z)

z

λ4π


•  Birefringence depends on health/pathology of muscle •  Can differentiate necrotic from undamaged tissue

Polarisation-sensitive OCT on muscle

Necrotic

Undamaged

Necrotic

Undamaged

Necrotic

Undamaged

Mdx mouse model, left gluteus L. Chin, X. Yang, R. A. McLaughlin, P. B. Noble, D. D. Sampson, “En face parametric imaging of tissue birefringence using polarization-sensitive optical coherence tomography”, J. Biomedical Optics, 2013


Polarisation-sensitive OCT on muscle


2D colour-coded map of birefringence •  Undamaged muscle high

birefringence •  Necrotic muscle low

birefringence

Threshold to distinguish between undamaged and necrotic

47

Calculation of percentage of necrotic tissue


Percentage area of muscle necrosis agrees well

48

Results from dystrophic mdx and control C57 mice: quadriceps (1, A), triceps (2, 3, 4, B, C) and tibialis anterior (5, D, E) muscles


•  Muscles – birefringence

•  Burn scars – birefringence and attenuation

•  Access – combine PS in a needle

Where are we going next in this area?


30G OCT needle images of muscle

Tendon Tendon

Connective tissue

Connective tissue

Myofiber Myofiber

@1300 nm

OCT Histology


30G OCT needle images of muscle

Myofibers Tendon

Connective tissue


•  OCT needle probes have limited resolution

•  Can we improve the resolution using confocal?

Confocal microscope in a needle


Confocal microscope in a needle

Imaged at 15-mm depth in bovine muscle tissue with 700 nm resolution

Pillai et al., Optics Express 19, 7213, 2011 Laser

488 nm

PMTBS

SMF (angle cleaved) Band-pass

filter

GRIN microendoscope

Scan actuator xy

GRIN fiber

Notch filter

Microscope objective

Sample

22 G needle Guiding needle

350 μm-diameter optics in a 22-gauge needle (700 μm diameter) Deep tissue – ultimate resolution

Low-NA/high-NA GRIN doublet with proximal GRIN fibre scanning

10 μm


•  We can get more constrast from parametric imaging

•  We need 3D, and we trade off depth resolution – new problem

•  Flavours of optical properties:



•  Need to target applications, not just be empirical










•  Upper airway

–  Obstructive sleep apnea

–  Asthma

•  Lower airway

–  Obstruction - stenoses, lung cancer, COPD

–  Airway remodelling - asthma, COPD, bronchomalacia, bronchiectasis

Anatomical optical coherence tomography

J. J. Armstrong et al., Opt. Express 11 (1817-1826) 2003 J. J. Armstrong et al., Am J. Respir. Crit. Care Med. 173 (226-233) 2006

Internal dimensions of hollow organs


•  Scanning Michelson interferometer

• Long range low-coherence axial sectioning

•  Rotational point beam scanning

•  Elastic single back-scattering

(Anatomical) optical coherence tomography


•  Long radial range

•  Pullback axial scanning

(Anatomical) optical coherence tomography


Anatomical OCT – Upper airway anatomy


Armstrong et al., Am. J. Respir. Crit. Care Med., p. 226, 2006

Clinical measurements – Pullback scan


Able to quantitatively observe sleep apnoea events – previously not routinely possible

Leigh et al., IEEE Trans. Biomed. Eng., p. 1438, 2008

Clinical measurements – Apnoea events


Respiratory phase gating in the pharynx

–  Images show movement of airway wall with respiratory phase

–  Threshold loading used to increase inspiratory effort

–  Greater inspiratory effort → larger movement

–  First examples of OCT breath-gated images

–  Important for 3D acquisitions

Deep breathing

Breathing against inspiratory threshold load of 20 cm H2O

Oropharynx

Velopharynx

See also VJBO, Vol. 4, Issue 6, 26 May 2009, cover

R. A. McLaughlin, J. J. Armstrong, S. Becker, J. H. Walsh, A. Jain, D. R. Hillman, P. R. Eastwood, D. D. Sampson, Respiratory gating of anatomical optical coherence tomography images of the human airway , Opt. Express, vol. 17, no. 8, pp. 6568-6577, 2009.


Clinical sleep research


Why is it useful?

–  Stent size selection in tracheo-bronchial disease

–  Airway patency beyond obstructing lung cancers/tumour extent

–  Quantifying tracheobronchomalacia

–  Regional compliance - research tool in airway diseases

Delivered through bronchoscope working channel (3 mm)

Trachea

Middle lobe

Main broncus

Lower lobes

J. J. Armstrong, S. Becker, R. A. McLaughlin, M. S. Leigh, J. H. Walsh, D. R. Hillman, P. R. Eastwood, and D. D. Sampson, Anatomical optical coherence tomography – a safe and effective tool for quantitative long-term monitoring of upper airway

size and shape, Proc. SPIE 6842, 68421N (2008).

Trachea to intermediate size

airways (3-4 mm)

aOCT in the lower airway


J. P. Williamson et al, Measuring airway dimensions during bronchoscopy using optical coherence tomography , Eur. Respir. J. 35(1), 34-41, 2010

P. B. Noble et al., Distribution of airway narrowing responses across generations and at branching points, assessed in vitro by anatomical optical coherence tomography , Respiratory Research 11, doi:10.1186/1465-9921-11-9, 2010

P. B. Noble et al., Airway narrowing assessed by anatomical optical coherence tomography in vitro: Dynamic airway wall morphology and function , J. Appl. Physiol.108, 401-411, 2010

Validation in a pig model


•  Operating theatre •  Through bronchoscope

operation - working channel

Human lower airway – bronchoscopy suite


aOCT-CT validation –  Pre-operative CT –  Intra-operative aOCT –  Strong correlation in

airway diameter

–  Data available online –  See Optics Express website

http://www.opticsinfobase.org/oe/

R. A. McLaughlin et al, Applying anatomical optical coherence tomography to quantitative 3D imaging of the lower airway , Optics Express, 16(22), 2008

Axial

Coronal

Human lower airway – CT data



aOCT-CT validation –  Pre-operative CT –  Intra-operative aOCT –  Strong correlation in airway

diameter



3D reconstruction of trachea using OSA s Interactive Science Publishing

VolView (VTK based from Kitware, NY)

Human lower airway – aOCT data



Intra-operative imaging –  Imaging from larynx to trachea –  Surgical instrument visible in

scan –  Laryngeal mask

(Used to introduce bronchoscope into airway)



aOCT – larynx to trachea


Clinical history –  51 yo female previously intubated

during severe asthma attack –  Prolonged ventilation via a

tracheostomy –  One month later developed

breathing problems

Imaging CT scan revealed subglottic tracheal stenosis

Case study – stenosis


CT/aOCT cross-comparison shows good correlation

Pre-op CT reconstruction 3D aOCT reconstruction

Outcome - Enabled accurate intraoperative stent sizing

Case study – stenosis


Question Had the airway completely collapsed? Problem CT may be out of date Unable to push bronchoscope past stenosis Solution Image with anatomical OCT probe

Bronchoscopic view of a tumour in the proximal left main bronchus as viewed from above the main carina

The aOCT probe was advanced between the tumour and airway wall into the left lower lobe

Case study – tumour occlusion


Left main bronchus obstructed by tumour; a patent airway, distal to the tumour, is seen

Left main bronchus, now fully patent, following endoscopic tumour resection and chemoradiotherapy

–  Follow-up bronchoscopy two months later –  Airway free of tumour

J. P. Williamson et al., Using optical coherence tomography to improve diagnostic and therapeutic bronchoscopy , Chest 136(1), 272-276, 2009

Tumour occlusion – outcome


In vivo human airway local compliance – aOCT Elastic Properties of the Central Airways in ObstructiveLung Diseases Measured Using Anatomical OpticalCoherence Tomography

Jonathan P. Williamson1,2, Robert A. McLaughlin3, William J. Noffsinger1, Alan L. James1,4, Vanessa A. Baker1,4,Andrea Curatolo3, Julian J. Armstrong3, Adrian Regli5, Kelly L. Shepherd2,4, Guy B. Marks6, David D. Sampson3,7,David R. Hillman1,4,5, and Peter R. Eastwood1,2,4

Central Airway Compliance in AsthmaUp or Down? Good or Bad?

In this issue of the Journal, Williamson and coworkers (pp. 612–619) report on the use of anatomical optical coherence tomogra-phy (OCT) to measure the luminal area of central intrathoracicairways (generations 0–5) (1). By coupling this dynamic, in vivomeasurement with simultaneously measured transpulmonary pres-sure, they derived area–pressure relationships of these airwaysand calculated airway compliance (Caw) and specific compliance(sCaw). They then compared these values in control subjects andthose with obstructive lung diseases: asthma, chronic obstructivepulmonary disease (COPD), and bronchiectasis. This is an excit-ing use of a new technology, and their results are surprising.

March 2011

First measurements of local airway elastic properties in situ shows surprising findings in lung disease









In vivo microscopy in medical imaging

Deep-tissue microscopy requires: – Optical sectioning

– Current best is a few millimetres in depth

–  Endoscopic delivery in hollow organs

– Needle delivery in solid tissues


OCT microscope-in-a-needle

23-gauge

Mirror

Optical adhesive

SMF No-core fiber

GRIN fiber

30-gauge 23-gauge

30-gauge

140 μm hole drilled with fs-laser

0.31 mm

125 μm

GRIN NCF SMF


3D OCT-in-a-needle imaging engines 840-nm SD-OCT System:

–  840-nm SLD, 6.2 μm axial resolution –  Spectrometer-based, 140 kHz Basler Sprint –  Common-path sample arm

1300-nm SS-OCT System: –  1310-nm Axsun swept source, 12 μm

axial resolution, 50-kHz sweep rate –  High sensitivity, >110 dB –  Common-path and dual-arm probes


Sheep lung scanning Alveoli and bronchioles

–  In-tact lung, saline filled –  23-gauge needle, 0.64 mm hole

–  Marked areas excised for histology

Quirk et al., J Biomedical Optics, Art. 0036009, 2011

Haematoxylin and eosin-stained

histology


Sheep lungs – 3D views


Breast tumour margin – OCT and histology

R. A. McLaughlin, B. C. Quirk, A. Curatolo, R. W. Kirk, L. Scolaro, P. Robbins, B. A. Wood, C. M. Saunders, D. D. Sampson, “Imaging of breast cancer with optical coherence tomography needle probes: Feasibility and initial results”, IEEE J. Selected Topics on Quantum Electronics, In press

H&E section

OCT









Take home messages •  3D opens up possibilities to explore new contrast

•  Parametric imaging offers niche opportunity

•  Attenuation requires nothing new

•  Birefringence requires polarisation sensitive-OCT

•  Endoscopy with OCT presents many opportunities

•  Anatomical OCT presents opportunities in airways

•  Needle-based OCT opens up many possibilities

-  For much more on this see my Friday colloquium 2pm

• 

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