Automated tissue type imaging with OCT Ton van Leeuwen DJ Faber, DM - - PowerPoint PPT Presentation

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Automated tissue type imaging with OCT

Ton van Leeuwen

DJ Faber, DM de Bruin, NM Weiss, DV Nguyen, SM Jansen, M Almasian, AL Post, L Wilk, MCG Aalders, Berrend Muller, A Swaan (AMC), X Attendu (PolyMtl), J Kalkman (TUD) Academic Medical Center, University of Amsterdam, Biomedical Engineering & Physics: T.G.vanLeeuwen@amc.uva.nl www.amc.nl/BMEP

Gustav Strijkers Ed van Bavel Henk Marquering Maurice Aalders

• Physics of

– Interaction of light with tissue – Development of instrumentation

• Application of light

– Therapeutic – Diagnostic

• Monitoring / function
• Imaging / morphology

Optical imaging and sensing of functioning biological systems (cells/organs) Relation between optical properties (µa, µs, g) and status of the tissue or tissue type

introduction dependent scattering multiple scattering conclusion

OCT is the “Harlem Oil” of Biomedical Optics

introduction dependent scattering multiple scattering conclusion

See http://www.haarlemmerolie.nl

One drop of OCT solves all the problems…

introduction dependent scattering multiple scattering conclusion

Velocity (mm/sec)

What kind of tissue are we looking at?

introduction dependent scattering multiple scattering conclusion

One drop of OCT solves all the problems…

introduction dependent scattering multiple scattering conclusion

• OCT signal dependent on:

– Depth of focus – Position of the focus – Amount of back scattering – Attenuation coefficient

( ) ( )

z P P z h c zn z i

s NA b sample ref med

µ µ g h 2 exp ) ( 2 Re

, det

• Ä

þ ý ü î í ì ÷ ø ö ç è æ =

DJ Faber, et al.Optics Express 2004, 12: 4353-4365

introduction dependent scattering multiple scattering conclusion

Single scattering approximation

• OCT signal dependent on:

– Depth of focus – Position of the focus – Amount of back scattering (amplitude of the OCT signal) – Attenuation coefficient

( ) ( )

z P P z h c zn z i

s NA b sample ref med

µ µ g h 2 exp ) ( 2 Re

, det

• Ä

þ ý ü î í ì ÷ ø ö ç è æ =

800 nm OCT of rat aorta

introduction dependent scattering multiple scattering conclusion

• OCT signal dependent on:

– Depth of focus – Position of the focus – Amount of back scattering – Attenuation coefficient (‘slope’ of the OCT signal)

( ) ( )

z P P z h c zn z i

s NA b sample ref med

µ µ g h 2 exp ) ( 2 Re

, det

• Ä

þ ý ü î í ì ÷ ø ö ç è æ =

Kodach et al, Biomedical Optics express 2010, Optics Express 2011

introduction dependent scattering multiple scattering conclusion

Velocity (mm/sec)

application of µtextraction

Van der Meer et al, IEEE TMI, 2005, 24, 1369-1376 Lasers Med Science 2005, 20, 45-51

Cardiovascular tissues

• OCT signal dependent on:

– Depth of focus – Position of the focus – Amount of back scattering – Attenuation coefficient

( ) ( )

z P P z h c zn z i

s NA b sample ref med

µ µ g h 2 exp ) ( 2 Re

, det

• Ä

þ ý ü î í ì ÷ ø ö ç è æ =

• Is it so simple to measure !" (!$%& ≈ !")?
• How to verify that (e.g. for large !")?

– !"~*+,*-,./0.1+, – !2~*+,*-,./0.1+, – !"~!2 –

34 35 = *+,7.0,.

introduction dependent scattering multiple scattering conclusion

Velocity (mm/sec)

All μOCTfor Intralipid

• @ 600, 800, 1300 & 1600 nm (single scattering model)

introduction dependent scattering multiple scattering conclusion

Why is the attenuation coefficient saturating for higher concentrations IL?

5 10 15 20 5 10 15 20 25 30

600 nm 800 nm 1300 nm 1600 nm scattering coefficient (mm

• 1)

Intralipid concentration (%)

g » 0.8 g » 0.7 g » 0.3 g » 0.4

μOCT (mm-1)

Velocity (mm/sec)

Dependent scattering for all beads

Corrected for dependent scattering with structure factor by Percus-Yevick model

μs for high concentrations

Nguyen et al Optics Express 2013

0.00 0.05 0.10 0.15 0.20 0.25 0.30 5 10 15 20 25 30 35 µs (mm

• 1)

volume fraction

Æ 1215 nm Æ 906 nm Æ 759 nm Æ 0.376 nm

introduction dependent scattering multiple scattering conclusion

!" ≁ $%&$'&()*(+%&

OCT signal analysis: amplitude

!" ~ $%&$'&()*(+%& Amplitude Amplitude

M Almasian, et al.J BiomOptics, 2015, 20: 121314

introduction dependent scattering multiple scattering conclusion

OCT signal analysis: amplitude

back scattering coefficient/scattering coefficient

Mitra Almasian et al, Scientific Reports 2017

∅ ≈ # $% 2

introduction dependent scattering multiple scattering conclusion

'( ≁ '*

Velocity (mm/sec)

• Picking up multiple scattered light will reduce µOCT using

the single scattering model

• higher scattering values, deeper into the tissue, dependent
• n g and NA optics
• Extended Huygens Fresnel (EHF) model

Effect of multiple scattering…

• D. Levitz et al., Optics.Express 2004, 12, 249-259

( ) ( ) ( ) ( ) [ ] ( ) [ ]

2 1 2 2 2 2 2

exp 1 1 exp 1 exp 2 2 exp 1 ú û ù ê ë é

• +

+

• +
• µ

s h s h s s s s h d

W W z W W z z z W z i µ µ µ µ

introduction dependent scattering multiple scattering conclusion

Velocity (mm/sec)

OCT: dependent (PY) and multiple (EHF)scattering

Æ = 0.70 µm gMie+PY= 0.71-0.56 Æ = 0.47 µm gMie+PY= 0.39-0.06 Æ = 0.91 µm gMie+PY= 0.79-0.67 Æ = 1.6 µm gMie+PY= 0.91-0.87

introduction dependent scattering multiple scattering conclusion

Velocity (mm/sec)

• Blood, µOCT measured by 800 nm OCT

Effect of chosen (fixed) g in EHF model g = 0.995 g = 0.8

Spheres, Intralipid, g>0.8, so what?

Faber et al, OL 2009

introduction dependent scattering multiple scattering conclusion

phantom B-scan plane Flow channel Solid TiO2 phantom Whole blood flow 400 μm channel, 20 mm/sec Solid TiO2 phantom

Forward scattering of blood

• Whole blood flowing through

static sample: flow on!

SM Jansen et al, Sensors 2018

Velocity (mm/sec)

• Fitting both µOCT and g in EHF: no convergence
• Setting g correctly results in:

Effect of NA (PSF) on µOCT

M Almasian, in progress

introduction dependent scattering multiple scattering conclusion

!" 13%& 20%& 51%& %* (&&,-) g %/01 (&&,-) %/01 (&&,-) %/01 (&&,-) 5.4 0.91 6 7 10 14 0.89 22 23 24 21 0.87 40 33 55

• Better model needed?

Velocity (mm/sec)

• Fitted PSF (and Roll-of) for 4 C7 Dragonflytm

Intravascular Imaging Probe (St. Jude Medical,

• St. Paul, Minnesota, USA)

But NA (PSF) is more or less constant..

introduction dependent scattering multiple scattering conclusion

Velocity (mm/sec)

• It is not as simple as Harlem Oil

– "# ≁ %&'%(')*+),&' – "- ~ %&'%(')*+),&' – "# ≁ "-

• correctly fitted PSF (and Roll-of)

– NA can differ between catheters

• If / ≾ 0.8: "567 ≈ "#

– For larger g, more multiple scattered light contributes to the OCT signal

• automated tissue type imaging with OCT:

– be carefull – other contrast mechanisms – The eye…

Discussion

introduction dependent scattering multiple scattering conclusion

Velocity (mm/sec)

What kind of tissue are we looking at?

introduction dependent scattering multiple scattering conclusion

Velocity (mm/sec)

What kind of tissue are we looking at?

introduction dependent scattering multiple scattering conclusion

OCT during restauration of Rembrandt painting Marten at Rijksmuseum, see https://www.rijksmuseum.nl/nl/marten-en-oopjen

Velocity (mm/sec)

• It is not as simple as Harlem Oil

– "# ≁ %&'%(')*+),&' – "- ~ %&'%(')*+),&' – "# ≁ "-

• correctly fitted PSF (and Roll-of)

– NA can differ between catheters

• If / ≾ 0.8: "567 ≈ "#

– For larger g, more multiple scattered light contributes to the OCT signal

• automated tissue type imaging with OCT:

– be carefull – other contrast mechanisms – The eye…

Discussion

introduction dependent scattering multiple scattering conclusion