nw2007 ophthalmic oct

A brief history of OCTA brief history of OCT

Nawat Watanachai

Sir Charles Gairdner Hospital

October 2007

Nawat Watanachai

Sir Charles Gairdner Hospital

October 2007

•Huang, Hee, Fujimoto, Puliafito 1991 Huang, Hee, Fujimoto, Puliafito 1991 •1st in vivo retinal images at the MIT in 19931st in vivo retinal images at the MIT in 1993•Commercially available in 1996Commercially available in 1996

•Optical B-scans (Cross-sections)Optical B-scans (Cross-sections)•Resolution ~ 10 micronsResolution ~ 10 microns

OCT : Optical Coherence TomographyOCT : Optical Coherence Tomography

1st OCT image of the retinaResolution: 17 μmdepth ~1.5 mm into the tissue

BASIC OCTBASIC OCT

Clinical ApplicationsClinical Applications Visualization of vitreoretinal interface Cross-sectional visualization retinal pathology Nerve fiber layer analysis for glaucoma Optic nerve head analysis for glaucoma Other jobs eg. Anterior segment

Visualization of vitreoretinal interface Cross-sectional visualization retinal pathology Nerve fiber layer analysis for glaucoma Optic nerve head analysis for glaucoma Other jobs eg. Anterior segment

Does OCT make a difference?Does OCT make a difference?

Clinical Diagnosis/ Decision Making

Medical Record/ Documentation

Patient Education/ Satisfaction

Clinical Diagnosis/ Decision Making

Medical Record/ Documentation

Patient Education/ Satisfaction

Medical ProofMedical Proof OCT provides objective evidence for treatment

decisions, both to treat or not to treat, and of response to treatment

Examples: cystoid macular oedema retinal vein occlusion diabetic maculopathy Others eg fleck diseases

OCT provides objective evidence for treatment decisions, both to treat or not to treat, and of response to treatment

Examples: cystoid macular oedema retinal vein occlusion diabetic maculopathy Others eg fleck diseases

CNV and AMDMacular holePMF

Time domain OCTTime domain OCT

Current clinical OCT devices utilize time domain technology ---> limit in signal acquisition time

700-900 nm* Z Dimension: Samples tissue with 1024 data points

over 2mm depth

X-Y Dimension: Takes a sample every 5-60 microns apart, 128-512 scans

Current clinical OCT devices utilize time domain technology ---> limit in signal acquisition time

700-900 nm* Z Dimension: Samples tissue with 1024 data points

over 2mm depth

X-Y Dimension: Takes a sample every 5-60 microns apart, 128-512 scans

Time domain OCT : problemsTime domain OCT : problems 1 detector, Each A-scan requires the movement of

several mechanical parts

Excellent image quality…if device and patient are not moving

1 detector, Each A-scan requires the movement of several mechanical parts

Excellent image quality…if device and patient are not moving

Time domain OCT : problemsTime domain OCT : problems

~400 A-scan per sec take time to catch the image Can give poor image resolution

No image registration --> not easily reproduce Error in both quantitative and qualitative

measurement in some situations

~400 A-scan per sec take time to catch the image Can give poor image resolution

No image registration --> not easily reproduce Error in both quantitative and qualitative

measurement in some situations

So, what are we looking for in the newer OCTs?So, what are we looking for in the newer OCTs?So, what are we looking for in the newer OCTs?So, what are we looking for in the newer OCTs?

• Higher resolutionHigher resolution• Higher imaging speedHigher imaging speed• Image registrationImage registration• Quantitative information Quantitative information

extractionextraction

• Higher resolutionHigher resolution• Higher imaging speedHigher imaging speed• Image registrationImage registration• Quantitative information Quantitative information

extractionextraction

Newer OCTsNewer OCTs

1. Spectral domain OCT -- available

2. Other OCTs

2.1 Ultrahigh resolution OCT

2.2 Adaptive optic OCT

2.3 Hybrid machines eg OCT/SLO, HRA/OCT

3. OCT for anterior segment

1. Spectral domain OCT -- available

2. Other OCTs




3. OCT for anterior segment

1. Spectral domain OCT1. Spectral domain OCT

1. Spectral domain OCT1. Spectral domain OCT High speed high resolution OCT Frequency swept light source at around 850-1040 nm

Improved axial image resolutions (<6 microns axial resolution appears possible)

High speed high resolution OCT Frequency swept light source at around 850-1040 nm

Improved axial image resolutions (<6 microns axial resolution appears possible)


The output is measured with the use of a spectrometer (may be > 2,000 detector elements), doesn’t need moving part during scanning 16,000-75,000 scan/sec (TD-OCT ~400)

The output is measured with the use of a spectrometer (may be > 2,000 detector elements), doesn’t need moving part during scanning 16,000-75,000 scan/sec (TD-OCT ~400)


Real time display and data streaming capabilities enable video-rate imaging at more than 30fps

Real time display and data streaming capabilities enable video-rate imaging at more than 30fps

QuickTime™ and aCinepak decompressor

are needed to see this picture.

1. Spectral domain OCT1. Spectral domain OCT Can produce 3-D projection image which can be aligned with the actual

fundus image to provide pixel-to-pixel registration 3-D imaging produces layers of information

Isolation of retinal layers makes image analysis possible in a broad fashion

3-D thickness map

Can produce 3-D projection image which can be aligned with the actual fundus image to provide pixel-to-pixel registration

3-D imaging produces layers of information Isolation of retinal layers makes image analysis possible in a broad

fashion 3-D thickness map

QuickTime™ and aMicrosoft Video 1 decompressorare needed to see this picture.


Pixel-to-pixel registration Precise scan location Image reproducibility

Some machines can generate fundus imaging and register the spatial location of each OCT section image

Pixel-to-pixel registration Precise scan location Image reproducibility

Some machines can generate fundus imaging and register the spatial location of each OCT section image




Pros Higher resolution/ 3D imaging Enhanced imaging speed Pinpoint registration

Cons Signal strength and depth resolution is dependent on the

path difference between the retina and the reference mirror --> the greater the distance (myopic eye), the weaker the signal and the lower the resolution

Yes………it’s price!

Pros Higher resolution/ 3D imaging Enhanced imaging speed Pinpoint registration

Cons Signal strength and depth resolution is dependent on the

path difference between the retina and the reference mirror --> the greater the distance (myopic eye), the weaker the signal and the lower the resolution

Yes………it’s price!

2. Other OCTs2. Other OCTs







2.1 Ultra-high Resolution OCT2.1 Ultra-high Resolution OCT

First described by Drexler and Fujimoto in 2001 Broad bandwidth, 150nm femtosecond Ti-sapphire

laser source (TD-OCT 10-25 nm) 1-3 microns axial resolution

First described by Drexler and Fujimoto in 2001 Broad bandwidth, 150nm femtosecond Ti-sapphire

laser source (TD-OCT 10-25 nm) 1-3 microns axial resolution

QuickTime™ and a decompressor



Video-rate with up to 25-50 B-scans/sec3,000 axial pixels and 600 transverse pixels (OCT-3 1,024 and 512 pixels)

Video-rate with up to 25-50 B-scans/sec3,000 axial pixels and 600 transverse pixels (OCT-3 1,024 and 512 pixels)



2.1 Ultra-high Resolution OCT2.1 Ultra-high Resolution OCT Pros

Enhanced anatomic detail

Enhanced visualization of the subretinal CNV

Pros Enhanced anatomic

detail Enhanced

visualization of the subretinal CNV QuickTime™ and a

Cinepak decompressorare needed to see this picture.


Cons Slow acquisition time of 4-5 sec (OCT-3 can do

the job in 1.3 sec) Require significant technical support for day-to-

day operation Limited ability to localize scans in relation to

precise fundus landmarks Alignment of serial scans dependent on fixation is

inaccurate

Cons Slow acquisition time of 4-5 sec (OCT-3 can do

the job in 1.3 sec) Require significant technical support for day-to-

day operation Limited ability to localize scans in relation to

precise fundus landmarks Alignment of serial scans dependent on fixation is

inaccurate

2.2 Adaptive optic OCT2.2 Adaptive optic OCT

Use electromagnetic deformable mirror (adaptive optic) to improve the spatial resolution Correct chromatic aberration of the eye to get

better light pathway

Use electromagnetic deformable mirror (adaptive optic) to improve the spatial resolution Correct chromatic aberration of the eye to get

better light pathway

2.2 Adaptive Optic OCT2.2 Adaptive Optic OCT

Pixel resolution of 3µm x 3µm Very fine image : able to Imaging the retinal cells

Pixel resolution of 3µm x 3µm Very fine image : able to Imaging the retinal cells

2.2 Adaptive optic OCT2.2 Adaptive optic OCT 3D video Voxel resolution of 3µm x 3µm x 3 µm

3D video Voxel resolution of 3µm x 3µm x 3 µm



2.3 OCT/SLO : multimodal imaging2.3 OCT/SLO : multimodal imaging

Introduced by Podoleanu and Jackson in 1998

Employs OCT scan simultaneous with confocal SLO images SLO = surface detail OCT = internal detail

Introduced by Podoleanu and Jackson in 1998

Employs OCT scan simultaneous with confocal SLO images SLO = surface detail OCT = internal detail


Single illumination source with parallel detector systems ensures pixel-to-pixel correlation between views

Overlay capability permits view of internal anatomy beneath surface landmarks

Single illumination source with parallel detector systems ensures pixel-to-pixel correlation between views

Overlay capability permits view of internal anatomy beneath surface landmarks




Coronal OCT scans capture details often lost in fixation-driven B scanning

SLO channel facilitates integration of functional testing such as angiography, microperimetry, and mfERG

Coronal OCT scans capture details often lost in fixation-driven B scanning

SLO channel facilitates integration of functional testing such as angiography, microperimetry, and mfERG

2.3 OCT/SLO2.3 OCT/SLO

TD-OCT

OCT/SLO

Matching C-Scan Images Provide Linear Reference

2.3 OCT/HRA2.3 OCT/HRA

OCT + laser angiography Image registration --> precisely define the scan

location -->good for repeat measurement Record fundus image in the same time

OCT + laser angiography Image registration --> precisely define the scan

location -->good for repeat measurement Record fundus image in the same time

2.3 other multimodaling machines2.3 other multimodaling machines

Ultra-high Resolution OCT/SLO Combined Spectral Domain/ Time Domain High-

Resolution OCT/SLO

Ultra-high Resolution OCT/SLO Combined Spectral Domain/ Time Domain High-

Resolution OCT/SLO

Will you own this machine?Will you own this machine?

Keeps in mind OCT has become gold standard for some diseases

eg. PMF, MH Non invasive

limitation OCT does NOT provide dynamic information (FA

does) Depend on operator techniques Degraded in the presence of media opacity Computer can do wrong things

Keeps in mind OCT has become gold standard for some diseases

eg. PMF, MH Non invasive

limitation OCT does NOT provide dynamic information (FA

does) Depend on operator techniques Degraded in the presence of media opacity Computer can do wrong things

Which OCT is ‘the one’ for you?Which OCT is ‘the one’ for you?devices B-scan/ 3D Axial

resolutionScanning

speedNon-OCT imaging

(TD-OCT) Yes/no 10 400 Near IR

Heidelberg Spectralis HRA/OCT

Yes/yes 7 40,000 SLO, ICG, autoF

Optopol Copernicus 2

Yes/yes 6 25,000 Near IR

Optovue RTVue-1001

Yes/yes 5 26,000 Near IR

OTI OCT/SLO1 Yes/yes 5 28,000 SLO, ICG, microperimetry

Topcon 3D-OCT-10002

Yes/yes 6 18,000 Near IR/ color

Carl Zeiss Meditec Cirrus1

Yes/yes 5 27,000 LSLO

Which OCT is ‘the one’ for you?Which OCT is ‘the one’ for you?

Time domain OCT (~60,000+ AUD) Spectral domain OCT (>100,000 AUD)

ResearchersRetinal specialists who can use this

images to help with decision making in selected difficult cases

Time domain OCT (~60,000+ AUD) Spectral domain OCT (>100,000 AUD)

ResearchersRetinal specialists who can use this

images to help with decision making in selected difficult cases

Thank youThank you

nw2007 ophthalmic oct

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