IVUS Image Features:

Unlike X-ray angiography, IVUS creates a cross-sectional view of the coronary artery. As the sound waves penetrate the vessel wall, a unique representation of the coronary artery lumen as well as the wall composition is obtained.

Graphic below illustrates the typical features visible in an ultrasound image.

In a diseased coronary vessel wall, three distinct vessel structures are present. The innermost structure called the intima defines the vessel lumen and thereby lumen cross-sectional area. The second structure is an echolucent zone (in part comprised of muscular media) and appears as a dark structure. The third structure is adventitia and contributes a strong echo. In normal arteries, the intima and media are thin (300-400 microns) and the total vessel area (area enclosed by the media-adventitia interface; also called the EEM area) is almost equal to the lumen area (area enclosed by the luminal boundary which is defined by the blood-intima interface). In the case of atherosclerotic vessels, plaque formation typically takes place within the intima resulting in reduction in the lumen cross-sectional area. Figure A is an IVUS image in a normal (minimally diseased) arterial segment. Notice that the intima and media are near each other. In the normal portion of the image (From 12:00 to 3:00 o’clock position) there is only one clear edge boundry which results from the echo contributed by the adventitia. Figure B is an image of a stenotic site. The three wall structures along with the luminal narrowing can now easily be seen. Figure C illustrates a stent. Notice the bright echoes observed from the stent struts. Notice that in addition to the luminal narrowing, IVUS also has the ability to directly visualize and quantify the plaque cross-sectional area (enclosed between the luminal boundary and the media-adventitia interface; also called the plaque plus media (P&M) area). This unique feature of IVUS has made it an important clinical tool.

TeachIVUS

This interactive teaching software guides the user through quantitative and qualitative image analysis steps. The user is asked to perform the following analysis tasks:

• Identification of the proper region for analysis.
• Identification of Lumen Diameter,
• Identification of Vessel Diameter,
• Identification of Lumen Area,
• Identification of Vessel Area,
• Identification of Arcs of Calcium,
• Image Interpretation (identification of image features and plaque morphology).

The software is developed keeping in mind the needs of beginners, intermediate level users as well as advanced users. The user can select a learning level from the menu.

The images may be further classified using the drop down menus for manufacturer, type of procedure and the like. A brief clinical history is displayed during image loading. When reviewing the IVUS images, the typical display is a pullback starting distally in the vessel and progressing proximally. In some cases, associated images (usually angiograms) are available for review.

The user should try to perform the analysis tasks described above at each region of the vessel noted on the gold tabs at the top of the display. These regions will vary depending on the case selected. The user analysis visually and quantitatively is compared to an embedded expert analysis. To see the expert interpretation the user can click on the “Show Expert” button at the end of his/her interpretation. In the image interpretation section, the user may be asked to graphically label the image feature identified (i.e., a branch.) A report of the user's performance is available.

Note: Expert analysis is performed by a well-recognized interventional cardiologist with over 15 years of experience in the area of IVUS imaging.