Editorial Slides VP Watch, February 13, 2002, Volume 2, Issue 6

OCT Catheter on Its Way to Cat Lab?

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.

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

Brezinski, Tearney, Bouma, Fujimoto, and colleagues in 1997 discussed the advantages of OCT as following:

I. High resolution, II. Broad dynamic range, and III. Ability to be delivered through intravascular

catheters 2

LightLab Imaging, LLC.© 2000,2001 LightLab Imaging, LLC.

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

IVUS (A) and OCT (B) images of the stented right coronary artery are shown. Although IVUS showed a well-deployed stent, the detailed structure around the stent struts is not

well visualized. In addition, OCT clearly visualized tissue prolapse between the stent struts (12 to 3 o’clock). The tissue prolapse occurred mainly in an area with lower OCT signal

intensity, which is suggestive of a plaque with a large lipid content. 5

Visualization of Tissue Prolapse Between Coronary Stent Struts by OCT

Visualization of Tissue Prolapse Between Coronary Stent Struts by Optical Coherence Tomography: Comparison With Intravascular Ultrasound ; Ik-Kyung Jang, Guillermo Tearney, and Brett Bouma

Circulation 2001 104: 2754.

As highlighted in VP Watch of this week, Jang and colleagues showed the feasibility and the ability of intravascular OCT to visualize the components of coronary plaques in living patients. 3

They found that compared with IVUS, OCT images provide additional morphologic information, which could be used to improve plaque characterization. 3

Echolucent coronary plaque imaged in vivo by OCT (A) and intravascular ultrasound (IVUS) (B). (A) This plaque demonstrates a homogeneous, signal-poor region (inset, arrow) by OCT that extends near the vessel lumen at the shoulder of the plaque (inset, arrowheads), possibly representing a

vulnerable shoulder region. The minimum cap thickness at this region measured 20 ± 3 m by OCT. (B) The echolucent region (arrow) is also identified in the IVUS image from the same site; but the cap

is difficult to visualize, and its thickness cannot be measured. Tick marks, 1 mm.

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

Comparing echolucent coronary plaque imaged in vivo by OCT and IVUS

Jang, Tearney, and their colleagues also compared the OCT and IVUS images of the signal-rich band overlying the echolucent regions and showed the potential for OCT to measure cap thickness with a greater degree of precision than IVUS. 3

They also identified two additional plaques by OCT with similar characteristics that were not definitely identified by IVUS. 3

Conclusion:

I. OCT represents a new technology for intracoronary imaging because of its high resolution, broad dynamic range, and ability to be delivered through intravascular catheters.

II. The OCT images of human coronary atherosclerotic plaques (in vivo) provide additional, more detailed structural information than IVUS.

Conclusion:

III. The unique capability of OCT to resolve micrometer-scale features of coronary plaques in patients suggests that this new technique holds promise for identifying features of coronary plaques at risk for rupture.

Questions:

I. Knowing that presence of blood induces major artifact for OCT imaging, the question is how practically OCT catheter can be utilized for screening vulnerable plaques throughout coronary arteries?

II. Knowing the widespread prevalence of atherosclerotic plaque in healthy population, and plaques with similar morphology may have different outcome, the question is how OCT can identify active inflamed vulnerable plaques?

Questions:

III. Knowing the need for imaging both structure and activity of plaque, would it be feasible to combine OCT and thermography or OCT and near infra red spectroscopy?

IV. Assuming the limited use (<20%) of IVUS for plaque characterization in cat labs is due to cost issue, would OCT or combination of OCT and thermography/ spectroscopy be cost effective?

Suggestion:

VP.org Editorial Suggestion:

- Please email your thoughts to:

Discussion-Group@VP.org or DG@VP.org

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) Visualization of Tissue Prolapse Between Coronary Stent Struts by Optical Coherence Tomography: Comparison With Intravascular Ultrasound ; Ik-Kyung Jang, Guillermo Tearney, and Brett Bouma Circulation 2001 104: 2754.

References