Quantitative and Qualitative Image Comparison Between Intravascular Ultrasound and Optical Coherence Tomography

Nicholas J. Miele, Olivia Manfrini, Barry L. Sharaf, Edward McNamara, Lynne L. Johnson, David O. Williams Rhode Island Hospital, Providence, RI; Brown University Medical School, Providence, RI

Background: Optical coherence tomography (OCT) represents a promising new technology for intracoronary imaging. The aim of this study was to compare OCT to intravascular ultrasound (IVUS) imaging in vivo porcine coronary arteries. Methods: A new retro-flush OCT catheter was used to obtain images. A 50% contrast and 50% lactated ringers solution was injected to remove blood from the field of view. Both OCT and IVUS pictures were obtained with digital acquisition systems. We compared 13 images: 2 left main coronary artery, 5 left anterior descending artery (LAD), 2 diagonal, and 4 right coronary artery). For each image run multiple measurements and qualitative analysis were performed. Results: Imaging runs with the retro-flush catheter were similar in duration to those from IVUS. Both cross-sectional and longitudinal views were obtained. Both devices tracked the guide wire easily. 26 paired measurements of external elastic membrane diameter were compared between IVUS and OCT. There were no differences between IVUS 3.31mm ± 0.68mm and OCT 3.46mm ± 0.75mm, p = 0.48. Layers of the arterial wall were more distinguishable with OCT than with IVUS. OCT allowed for better localization of the side branch origin as well as better visualization of the distal arterial features. Additionally, peri-arterial venous structures not seen with IVUS were identifiable by OCT. An induced wire dissection was not detected by IVUS but was readily identifiable by OCT. There were no complications with either the IVUS or OCT imaging acquisition. Conclusions: OCT provided comparable quantitative image measurements with IVUS but defined qualitative vessel features more precisely.

Abstract

BackgroundOptical Coherence Tomography (OCT) is a new modality for high-resolution, cross-sectional intravascular imaging. OCT utilizes near-infrared light instead of ultrasound to capture images of the vessel structures. Image resolution is at least one order of magnitude higher than that of Intravascular Ultrasound (IVUS), allowing for a more detailed analysis of the arterial features. Inability to image through a blood signal, however, is a potential limitation. While there are many published studies regarding OCT, little data exists on in vivo coronary imaging and no comparative information is available.

Results

Conclusions1. Values of EEM were similar between OCT and IVUS.

2. Qualitative features were more clearly identified and defined by OCT and similar between the two catheter systems.

3. Image acquisition was not limited by the development of ischemia.

4. There was less variability in repeated measurements of OCT compared with those of IVUS.

IVU

S E

EM

OCT EEMY = .207 + .925 * X; R2 = .868; p < 0.0001

2.8

3.0

3.2

3.4

3.6

3.8

4.0

4.2

4.4

4.6

4.8

3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5

Comparison Between IVUS and OCT Measurement of External Elastic Membrane (EEM)

There was no difference in mean EEM OCT (3.94 ± 0.47mm) vs. IVUS (3.85 ± 0.47mm)(p=0.428).

During imaging runs there were no differences in the prevalence or degree of ischemia with either device.

There were no differences in either image quality, imaging times, or quantitative measurements between the two OCT catheter systems.

There were no difference in duration of pullback times between OCT (mean 35.4 ± 1.1 sec.) vs. IVUS (mean 43.6 ± 2.5 sec.) (p = 0.10)

There was a significant difference in reproducibility between OCT and IVUS. Variability was less with OCT, 0.01mm vs. 0.03mm, p = 0.015; Coefficient of Variation 0.29% vs. 0.85%.

AimsThe aim of this study was to compare quantitatively and qualitatively in vivo images obtained by OCT to those of IVUS.

MethodsTwo separate swine models (3 normal, 2 balloon injury / lard fed) (n=5) were used to compare intracoronary images obtained by both IVUS and OCT (Fig. A.). Images runs were begun in the same vessel location (3 left main, 7 left anterior descending, 2 diagonal, 3 left circumflex, and 6 right coronary arteries) for both devices, for a total of 128 paired measurements. Angiographic features such as side branches and lesion characteristics were used as landmarks for catheter positioning and measurements of vessel size. Both systems utilized automated pullbacks at 0.5mm per second. Quantitative measurements, pullback duration, and tolerance to the device were compared between the two systems. Two different types of OCT catheters were used for the imaging wire: 1) a retro-flush system (50%/50% lactated ringers(LR)/contrast in animal # 1, 100% LR subsequently) in the first three animals; and 2) a Toaki occlusion balloon catheter (also accompanied by a LR flush) in the last two (Figs. B. & C.).

A. LightLab OCT System B. Retro-flush Imaging Catheter

with internal imaging wireC. Imaging wire delivered

through Toaki balloon catheter

B.

C.

Computer

PatientInterfaceUnit

OpticalEngine

A.

Results

1 mm

IVUS OCTPeri-Arterial Venous Structures

IVUS OCT

Image Comparisons

Coronary Dissection

Quantitative Comparison

OCTIVUS

3.57 3.72