Plaque Characterization With Optical Coherence Tomography
Debra Stamper, PhD*, ,
Neil J. Weissman, MD, FACC and
Mark Brezinski, MD, PhD*,,a,*
* Department of Orthopedic Surgery, Brigham & Women’s Hospital, Boston, Massachusetts
Harvard Medical School, Boston, Massachusetts
Cardiovascular Research Institute, Washington Hospital Center, Washington, DC
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Figure 1 (A) Photograph of an ocular coherence tomography (OCT) device. This is a photograph of the Lightlab (Westford, Massachusetts) imaging engine. (B) Photograph of an OCT catheter. This figure is a photograph of a 0.017-inch OCT imaging catheter/guidewire consisting of relatively simple fiber optics. This includes a gradient index (GRIN) lens, single mode optical fiber, prism, and speedometer cable. (C) Schematic of a traditional OCT system. Ocular coherence tomography works via the technique of low coherence interferometry as described in the text.
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Figure 2 Thin intimal cap. (A) The OCT image. (B) The histopathology normal, native, in vitro human artery. The plaque is on the left, the relatively normal tissue is on the right. Bar is 500 µm. The most important feature is the shown by the arrow, where the intima is <50 µm in diameter. Reprinted, with permission, from Brezinski et al. (1).
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Figure 3 Plaque instability. The image in panel A shows a large collection of lipid, shown by the dark area, with a thin layer of intima above it from a native in vitro coronary artery. The arrow shows a small area of intima <50 µm in diameter that is susceptible to rupture. The image in panel B shows another unstable plaque with fissuring to the intimal medial border (arrows). Bar is 500 µm. Reprinted, with permission, from Brezinski et al. (1).
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Figure 4 Intravascular ultrasound (IVUS) versus ocular coherence tomography (OCT) comparison (smooth muscle proliferation). (A) An IVUS image (30 MHz) of an in vitro aortic plaque. In the OCT image (B), in addition to the plaque on the left, a layer of smooth muscle proliferation is seen (red arrow). The smooth muscle proliferation is confirmed by the histopathology (C). The bar in the OCT image is 500 µm. Reprinted, with permission, from Brezinski et al. (8).
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Figure 5 Intravascular ultrasound (IVUS) versus ocular coherence tomography (OCT) comparison (intimal hyperplasia). This image demonstrates an OCT image (A) and IVUS image (30 MHz) (B). Both images were generated with 2.9-F catheters. The IVUS catheters were not reused. In the OCT image the intimal hyperplasia is seen, whereas in the IVUS image, it is difficult to detect. The bar in the OCT image is 500 µm. Reprinted, with permission, from Tearney et al. (6).
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Figure 6 Intravascular ultrasound (IVUS) (40 MHz) versus ocular coherence tomography (OCT) comparison. The images in A and C are OCT images, whereas the images in B and D are IVUS (40 MHz) of a native in vitro coronary artery. The IVUS catheters were not reused. In the OCT images, not only is structure better defined but OCT can penetrate completely through the near occlusive vessel to the media. Limitations of OCT penetration depth described in detail in the text. Reprinted (modified), with permission, from Patwari et al. (9).
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Figure 7 In vivo imaging of rabbit aorta—at 4 frames/s through a 2.9-F ocular coherence tomography (OCT) imaging catheter. The OCT image is in panel A, the histology is in panel B. The OCT image was performed in the presence of saline flush (2 to 4 cc/s). Arrow indicates clot. A = adventitia; M = media; V = vena cava. Reprinted, with permission, from Fujimoto et al. (10).
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Figure 8 Presence of an in vivo intimal flap. In this patient, an intimal flap is identified with the ocular coherence tomography imaging guidewire. Reprinted, with permission, from LightLab and Prof. Grube et al. (15). A demonstrates the entire artery while B is an enlargement of the square in A.
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Figure 9 In-stent restenosis. In this patient, in-stent restenosis is noted as imaged with the 0.014-inch imaging guidewire. IVUS = intravascular ultrasound; OCT = ocular coherence tomography. Reprinted, with permission, from LightLab and Prof. Grube et al. (15).
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Figure 10 Qualitative proof of mismatch as the source of scattering. In the top image, saline is being circulated over a reflector. The top line is the inner layer of the tubing. The second line is the reflector. Saline is between them. In the middle image, blood is being circulated rather than saline through the system. The reflector is no longer seen. In the bottom image, blood has been removed, lysed, and reintroduced into the system. The signal off the reflector returned to values not significantly different than the control subject. Reprinted, with permission, from Circulation 2001;103:2000–4.
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Figure 11 (A) Increased penetration with index matching. In this figure, the difference in penetration after addition of compounds or control is seen. The saline control had no significant effect (7 ± 3%). Dextran resulted in a 69 ± 12% increase in penetration. Intravenous (IV) contrast resulted in a 45 ± 4% increase. Both were significantly different than the control. (B) Influence of compounds on hematocrit and red cell counts. There was no significant difference between the effects of dextran and saline on either hematocrit and red cell count. Therefore, the improved penetration was not due to either a change in cell size or number. There was a slight but significant difference in red cell size after IV contrast compared with saline control. This might have contributed slightly to the effect. Reprinted, with permission, from Circulation 2001;103:2000–4.
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Figure 12 Examining intima boundary sharpness as a marker for lipid. In this figure, the yellow arrows demonstrate the cap-lipid interface that is diffuse and is covered by a highly scattering cap (yellow reflections). The white arrow, which is also over lipid, identifies cap with lower scattering, and the cap-lipid interface is sharply defined. Finally, the black arrow shows the intimal-elastic layer interface (no lipid present) that is diffuse with an intima that is highly scattering. The reason for the diffuse nature of the intimal-elastin border is likely that multiple scattering is obscuring, owing to high scattering within the intima. It is unclear, therefore, whether the lipid interface is diffuse because of the core composition, as previously suggested, or multiple scattering from the cap. Reprinted (modified), with permission, from Circulation 1996;93:1206–121.
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Figure 13 Single detector polarization-sensitive ocular coherence tomography (PS-OCT) imaging. This image illustrates the principles behind single detector PS-OCT. In the trichrome stained section (A) of this in vitro coronary artery, the artery appears relatively homogeneous. In the picrosirius stained section (B), where brightness identifies organized collagen, it can be seen that the artery is heterogeneous by PS-OCT. The PS-OCT images (C and D), at two different polarization states, show different changes in backreflection intensity in different areas of the arteries. This is consistent with the heterogeneity of the picrosirius section. The largest OCT changes had a positive predictive power for collagen of 0.889, whereas the smallest change had a negative predictive power of 0.929.
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