Flexible fiberoptic catheter used for light delivery OCT enhances imaging resolution that may permit the evaluation of clinical (e.g., luminal measurements during PCI) and research (e.g., fibrous cap thickness and strut levelanalysis) parameters for the interventional cardiologist.

1. DR NILESH TAWADE
JHRC MUMBAI

2. INTRODCUTION
OPTICAL

LIGHT
COHERENCE 
SPECEFIC
PROPERTY OF
LIGHT
(MONOCHROMATC
LIGHT )
TOMOGRAPHY 
LOOKING THE TISSUE
IN SLICES
(CROSS SECTIONS )

3. Optical Coherence Tomography (OCT) is an optical
imaging modality that uses to
create high-resolution images of tissue microstructure.
•  Subsurface imaging
•  High tissue contrast
•  Safe, non-ionizing radiation
•  Micrometer-level resolution
Key
Features:

4. Milestones in OCT Development
White light
interferometry
demonstrated
(1881)
Single-mode
fiber invented
(1970)
1st commercial OCT
eye scanner
(1997)
1st OCT images of
biomedical tissue
reported (1991)
Fiber-optic OCDR
introduced for telecom
(1987)
High-speed
endoscopic OCT
(1998)
Doppler OCT
Polarization-sensitive- OCT
1st clinical application
of intravascular OCT
(2002)
1st commercial FD-OCT
scanner introduced
(2007)

5. Intravascular OCT
 Flexible fiberoptic catheter
used for light delivery
 Catheter rotates to create
image frames
 Catheter pulls back to map
vessel segment
 Lesion analysis, stent
planning, post-stent
assessment, follow-up

6.  Measure echo time delay of
reflected light waves
 One pixel  5 x 19 um
 One axial line  1024 pixels
 One frame  500 axial lines
 Optical resolution  15um axial,
20 to 40 um transverse
6

7.  One pullback  270 frames

8. “L-Mode”
longitudinal view
“B-Mode”
cross-sectional view

9. 9

10.  Light is too fast for direct echo measurement  interferometry
 Compare path length between known “reference arm” and sample
 Mechanical reference arm motion limits imaging speed
10
intensity
axial distance
Demod Amp
Broadband
Source
D
Tissue
Mirror
Reflections

11.  Measurement of interference
pattern spectrum + Fourier
transform
 Signal generated from all
depths simultaneously
 Faster image acquisition
without loss of quality
Swept Laser
`
D
λ
intensity
intensity
distance
FFT
Amp

12. + =
Optical fields summed at detector
(ES+ER)
(delayed) optical field
from sample arm
resulting intensity (power) on detector
I= (ES+ER)2
optical field from
reference arm
ES
ER

13. TD-OCT FD-OCT

14. 14
C7XR
M3
Dr. Francesco Prati, San Giovanni-Addolorata Hospital, Rome, Italy.
Prof. Eliosa Arbustini, Centro Malattie Genetiche Cardiovasc.
Lab. di Anat. Pat.-Area Trapiantologica, Pavia, Italy
100 fps, 20 mm/s pullback 20 fps, 1 mm/s pullback
Postmortem, formalin fixed artery

15. Parameter Determines Controlled By C7XR Value
Imaging Speed  Acquisition time
 Required flush volume
 Laser sweep rate
 Catheter rotation rate
 Pullback speed
100Hz
50,000 axial lines/s
20 mm/s
Sensitivity  Minimum detectable tissue
reflection
 Image contrast
 Electrical and optical system
design
Better than -100 dB
Imaging Range  Maximum vessel diameter  Laser linewidth
 Electrical and optical system
design
10 mm (in contrast)
Resolution  Minimum detectable tissue
feature
 Speckle size and image
granularity
 Laser tuning range (axial)
 Catheter focusing optics
(lateral)
15 mcm (axial
20 – 40 mcm (lateral)
Tissue Penetration  Visible depth into vessel wall  Scattering and absorption of
tissue
1 – 2 mm
15

16. Time Domain OCT (TD-OCT)
Mechanically scans a reference mirror
Slow imaging, moderate image quality
Frequency Domain OCT (FD-OCT)
Electronically scans the laser wavelength
Fast imaging, exceptional image quality
16

17. Performance Evolution
1999-2001
PTCA balloon + ImageWireTM
R&D prototypes
Not commercially
available
Inside PTCA balloon
‘Snapshot’ flush
imaging
2007
M3 System
CE mark
20 fps / 240 lines
Occlusion + flush
2004
Soft occlusion balloon + ImageWireTM
M2 System
CE mark
15 fps / 200 lines
Occlusion + flush
2009 C7XR™ System
CE mark, FDA
cleared
100 fps / 500
lines
Occlusion-free DragonflyTM
NO OCCLUSION

18.  Balloon occlusion not required
 Fast flush, spiral pullback acquisition
 5 cm arterial segment in 2.5 sec
 Rapid exchange (Rx) imaging catheter
20
100 frames/s, 500 lines/frame
15 mm axial resolution
10 mm scan diameter

19. DR NILESH TAWADE
JHRC MUMBAI

20. Pre-
Intervention
Plaque characterization
(lipid, calcium, fiberous, cap
thickness, thrombus)
Intervention planning
and stent sizing
(lesion diameter, length)
Post-
Intervention
Stent strut
malapposition
Intimal dissection
Follow-Up
Assessment
Neointimal growth (no
coverage, thin coverage,
restenosis)
In-stent
thrombosis
22

21. FD-OCT vs IVUS
23
 Edge dissection during
stent implantation
 Neointimal growth on
previously implanted stent
at follow-up

23. Axial Resolution 12 - 15 mm 100 - 200 mm
Beam Width 20 – 40 mm 200 – 300 mm
Frame Rate 100 frames/s 30 frames/s
Pullback Speed 20 mm/s 0.5 - 1 mm/s
Max. Scan Dia. 10 mm 15 mm
Tissue Penetration 1.0 - 2.0 mm 10 mm
Lines per Frame 500 256
Lateral Sampling (3mm Artery) 19 mm 225mm
Blood Clearing Required Not Required
IVUSC7XR

25.  In all the new generation of OCT systems the optical probe is integrated in a
catheter
 The profile ranges from 2.4 Fr to 3.2 Fr but all of them are compatible with 6 Fr
guiding catheter.
 The usable length is around 140 cm.
 The position and number of the radiopaque markers varies for the different
systems
 During the pullback the optic fiber probe is pulled along the catheter sheath
 All the systems have dedicated pullback devices and consoles that allow the
processing and storage of the data.

26. 1. Prepare the catheter purging it with saline
2. Calibrate the optical probe.
3. Advance the catheter over 0.014” guidewire till the optical
probe is distal to the region of interest. The different systems
have different radiopaque markers to guide the catheter
positioning
4. Start contrast or diluted contrast injection through the
guiding catheter (with a pump injector).
5. Begin pullback when vessel is visible in OCT image.

27. Image Interpretation And
Tissue Characterization

28.  Backscatter
 The reflection of light waves off the tissue and back to the Dragonfly catheter
 High backscatter means a brighter pixel  Also described as a “signal rich” region
 Low backscatter means a darker pixel Also described as a “signal poor” region
 Attenuation
 The reduction in intensity of the light waves as they pass through tissue due to
absorption or scattering
 High attenuation means the light cannot penetrate very deep
 Low attenuation means the light can pass through to allow visualization of deeper
tissue

31.  Composition
 Homogeneous
 Uniform in structure
 Heterogeneous
 Structure consists of dissimilar elements
 Texture
 Coarse
 Fine
33

32. Normal coronary artery
 Uniform silhouette
 3 layers visible in vessel wall
Data on file at LLI
Imaging
catheter
Guidewire
shadow
Adventitia
Media
Intima
34

33.  Edge/Border
 The creation of a border is due to the interface between different tissue
types
 One of the parameters used to differentiate plaque types
Calcium Lipid

34. 36
Homogeneous
• signal rich
• brighter pixel
High
backscatter
Finely textured
• deeper tissue can
be visualized
Low
attenuation

35. Sharp edges
Heterogeneous
• signal poorLow backscatter
• deeper tissue can
be visualized
Low attenuation
37Data on file at LLI

36. • low tissue
penetration
High
attenuation
Diffuse
shadowy
edges
High
backscatter
on surface
Low
backscatter
deeper
38Data on file at LLI

37. Fibrous Bright pixels Finely textured Deep penetration Homogeneous
Lipid Dark pixels Diffuse edge Low penetration Homogeneous
Calcium Dark pixels Sharp edge Deep penetration Heterogeneous
Fibrous Lipid
Calcium
39

39. Edge dissection
A disruption of the
vessel luminal surface in
the edge region
Easy to interpret using
cross-sectional and
longitudinal views
41

40. Intimal tear
 Clear
visualization of
even small
irregularities
42
Data on file at LLI

41. Thrombus – red
 Absorbs near-infrared light
 High backscatter on
surface due to signal
attenuation
 Appears as a bright mass
 Shadow (cannot see
behind it)
43
Data on file at LLI
Red thrombus
Data on file at LLI

42. White thrombus
Thrombus – white
 High backscatter
 Low attenuation
 Able to see behind it
44
Data on file at LLI

43. In-stent
restenosis
Thick layer
between stent
struts and lumen
45
Data on file at LLI Stent struts

44. Post Stent Implantation – Overlapping Stents
48 Not to be distributed or reproduced

46. Blood in Dragonfly Imaging catheter lumen
52
Data on file at LLI
Blood in catheter lumen Catheter lumen purged of blood.

47.  Red blood cells
mixed into flush
fluid
 Flush contrast
diluted with saline,
less viscous, does
not flush all RBC
Data on file at LLI

48. >> ΔArea < +/- 1%. No discernible effect of blood on lumen area measurements when boundary of vessel wall is visible
Swirls Speckles
Data on file at LLI

50. Data on file at LLI
Guidewire Shadow

51. Original position
of artery
Shifted position
of artery
Radial scan
lines
Image
Cause: Rapid movement
of the artery or Dragonfly
during a single frame
Effect: Slight elliptical
distortion with visible
‘stitch’.
Data on file at LLI

52. Ghost images
of stent strut
Actual stent strut
 Cause
 Light reflected multiple times
between two surfaces
 Effect
 Blurry replica appears at a fixed
distance away from the primary
image of an object
 High reflecting objects, like metallic
stent struts, can produce a series of
ghost reflections
Data on file at LLI

53.  Diagnostic assessment of coronary atherosclerosis.
 80% of clinically evident plaque rupture originates within an inflamed thin-
capped fibroatheromas
 Thin-capped fibroatheromas are characterized by 3 essential
components: a lipid core, inflammatory cell cap infiltration, and a thin
fibrous cap
 While OCT does not currently have the depth to quantify large lipid cores,
its
high resolution allows precise visualization and quantification of the thin
fibrous cap

54. A proposed 3-point classification defines stent strut apposition
 as embedded (when the leading edge is buried within the intima by more than one-half
its thickness),
 protrusion (when the stent strut is apposed but not embedded),
 malapposed (when there is no intimal contact)
 Another classification, pertinent for follow-up studies examining the degree
of neointima formation, describes whether or not the stent strut appears
covered with tissue, and whether struts are well apposed or malapposed

56. Stent struts are, therefore, classified
as
1) well apposed and covered;
 2) well apposed and not covered;
3) malapposed and not covered; and
4) malapposed but covered

57. Tissue prolapse
Tissue prolapse, or protrusion of tissue between stent struts
without apparent surface disruption, is defined as occurring if the
depth of protrusion is > 50 mcm .
This high frequency is similar to postmortem findings (94%) ,but
significantly higher than IVUS-verified prolapse of 18% to 35%.
suggesting OCT is both sensitive and specific.
The clinical significance of such prolapse is, however, unclear,
given that it occurs so frequently, and has not been associated
with early clinical events nor examined in relation to late clinical
events

63. The future of OCT will include advancements in anatomical and
functional assessment of lesions for the interventional
cardiologist.
 Anatomical assessment:
 An advanced edge detection algorithm that enables automated stent strut identification
 Texture analysis of OCT images may also help facilitate tissue characterization,
 Functional assessment.
Detection of Doppler-like signals may permit integration of
physiology and anatomical assessment using a single device.

64.  OCT enhances imaging resolution that may permit the evaluation of clinical (e.g., luminal
measurements during PCI) and research (e.g., fibrous cap thickness and strut level
analysis) parameters for the interventional cardiologist.
 The versatility of the physical properties of light position OCT as an imaging modality could be useful
for improving our understanding of the vascular biology of atherothrombosis. and assisting in our
performance of PCI procedures.
 However, routine clinical use of OCT will require further clinical trials to validate the technology,
establish standard definitions/measurements, and to test its safety and utility in improving clinical
outcomes like IVUS