SHAPE Society

1. Editorial Slides
VP Watch, January 15, 2003, Volume 1, Issue 2
Can OCT Catheter See Plaque Macrophages?!

2. –Optical coherence tomography
(OCT) is analogous to ultrasound,
measuring the intensity of back-
reflected light (near infrared light)
rather than sound (acoustical waves).
–An OCT image represents a cross
sectional picture of the optical
reflectance properties of tissue. 4
–OCT originally developed to image
the transparent tissue of the eye with
unprecedented resolution.

3.  Brezinski, Tearney, Bouma,
Fujimoto, and colleagues in
1997 discussed the advantages
of OCT as following:
• High resolution,
• Broad dynamic range, and
• Ability to be delivered through
intravascular catheters 2

4. –In vitro studies have shown that the
resolution of OCT (10-20 micron) can
resolve the thin fibrous caps thought to
be responsible for plaque vulnerability. 1
–Catheter-based diagnostic techniques
can provide structural information with
higher resolution than non-invasive
methods. OCT achieves at least 10
times higher resolution than IVUS, and
can be adapted for catheter-based
imaging of vulnerable plaque. 3

5. IVUS OCT
Coronary IVUS vs Coronary OCT
Tearney, Boma, Chang et

6.  Tearney, Jang, and colleagues
showed that in vivo OCT imaging of
normal coronary arteries, intimal
dissections, and deployed stents in
swine is feasible, and allows
identification of clinically relevant
coronary artery morphology with high-
resolution and contrast. 4

7. • As highlighted in VP Watch of this
week, Tearney and colleagues showed
OCT can characterize structure of
atherosclerotic plaque ex-vivo.5
• They further showed that macrophage
content of plaque cap can be identified
by OCT. 5

8. • Ex vivo studies
– Plaque characterization
– Cap thickness
– Macrophage density
• In vivo studies
– Feasibility
– Post-MI
Fibrous
Calcific
LIPID
Yabushita, Tearney et al. Circulation, 2002

9. Plaque Characterization Study
• Evaluate diagnostic potential (lipid pools)
• Methods
– 357 diseased arterial segments from 90 cadavers
• 78 Coronary; 86 Carotid; 143 Aorta
– OCT imaging, histology processing, registration
– Correlation of OCT with histology
– Develop OCT criteria for characterization (training set,
n=50)
– Prospectively test OCT criteria (validation set, n = 307)
– Two OCT readers and two pathologists
Yabushita, Tearney et al. Circulation, 2002

10. Plaque Characterization
lp
lp
Homogeneous,
Signal-rich
Fibrous Lipid pool
Echolucent,
Diffuse Borders
Echolucent,
Sharp Borders
Calcific
OCT Criteria, training set (n=50)
500 µm

11. Plaque Characterization Results
SENS .79
SPEC .97
SENS .95
SPEC .97
SENS .90
SPEC .92
• Accuracy Statistics
• Fibrous
• Calcific
• Lipid pool
Interobserver κ = 0.88, Intraobserver κ = 0.91
Yabushita, Tearney et al. Circulation, 2002

12. • Technology development
• Ex vivo studies
– Plaque characterization
– Cap thickness
– Macrophage density
• In vivo studies
– Feasibility
– Post-MI
– Epidemiology
– Prospective trials
*Mφ produce proteases
Degrade collagen and matrix
Impair structural integrity of cap
CD68 Immunoperoxidase
Cap
Lipid
Tearney, Bouma et al. Circulation, 2003

13. Macrophage Study
• Can OCT quantify macrophage content?
• Methods
– 26 diseased arterial segments from 17 cadavers
• 7 Carotid; 19 Aorta
– OCT imaging
– Histology processing - CD68, SMA, trichrome
– Correlation of OCT with histology
– 500x125 µm ROI
– Histology - automatic segmentation - % area staining
– OCT - quantitative image analysis
NSD=
σ
Smax−Smin( )
Tearney, Bouma et al. Circulation, 2003

14. Macrophage Study
250 µm
OCT
CD68
Low Mφ High Mφ
Tearney, Bouma et al. Circulation, 2003

15. Linear NSD vs. CD68
CD68 % area > 10 % - NSD cutoff 6.2%
R = 0.84
P < 0.0001
Tearney, Bouma et al. Circulation, 2003

16. Human Coronary Artery In Vivo
P
G
L
F
G
2x
m
a
i
ieleel
F
OCT IVUS
Tearney, Bouma et al. Circulation, 2003

17. Calcified Plaques In Vivo
OCT IVUS
Tearney, Bouma et al. Circulation, 2003

18. Lipid-rich Plaque In Vivo
OCT IVUS
Tearney, Bouma et al. Circulation, 2003

19. Thrombus In Vivo
OCT IVUS
Tearney, Bouma et al. Circulation, 2003

20. Conclusion:
• Intracoronary OCT represents a new
technology for microscale imaging of
atherosclerotic plaque.
• In exvivo studies OCT can identify
macrophage intensity in plaque cap.
• Given above, OCT can be an important
addition to cardiovascular cat labs, may
completely replace IVUS catheter.

21. Questions:
I. Presence of blood induces artifacts
for OCT imaging, knowing the time
constraint in cath labs, the question
is how practically OCT catheter can
be utilized for screening vulnerable
plaques throughout total coronary
arteries?

22. Questions:
• Assuming the limited use of IVUS
(<20%) for plaque characterization in
cath labs is due to cost issue, would
OCT with equal price be cost effective?
• With the trend towards non-invasive
diagnosis, and using invasive
procedure only for therapy, how will
OCT be greeted by interventional
cardiologists?

23. ReferencesReferences
1- Fujimoto JG, Boppart SA, Tearney GJ, Bouma BE, Pitris C, Brezinski ME.; High resolution
in vivo intra-arterial imaging with optical coherence tomography.; Heart. 1999
Aug;82(2):128-33.
2- Brezinski ME, Tearney GJ, Weissman NJ, Boppart SA, Bouma BE, Hee MR, Weyman AE,
Swanson EA, Southern JF, Fujimoto JG.; Assessing atherosclerotic plaque morphology:
comparison of optical coherence tomography and high frequency intravascular
ultrasound. Heart. 1997 May;77(5):397-403.
3- Ik-Kyung Jang, Brett E. Bouma, Dong-Heon Kang, Seung-Jung Park, Seong-Wook Park, Ki-
Bae Seung, Kyu-Bo Choi, Milen Shishkov, Kelly Schlendorf, Eugene Pomerantsev et al.;
Visualization of coronary atherosclerotic plaques in patients using optical coherence
tomography: comparison with intravascular ultrasound, Pages 604-609 ; Journal of the
American College of Cardiology 2002; Volume 39(4): 604-609
4- Tearney GJ, Jang IK, Kang DH, Aretz HT, Houser SL, Brady TJ, Schlendorf K, Shishkov M,
BoumaBE. Porcine coronary imaging in vivo by optical coherence tomography. Acta
Cardiol. 2000 Aug;55(4):233-7.
5- Quantification of Macrophage Content in Atherosclerotic Plaques by Optical Coherence
Tomography Tearney Guillermo , Yabushita Hiroshi , Houser Stuart , Aretz H , Jang
Ik-kyung , Schlendorf Kelly , Kauffman Christopher , Shishkov Milen , Halpern Elkan ,
Bouma Brett ,
Circulation. 2003;107:113