ARTIFACTS IN INTRAVASCULAR ULTRASOUND IMAGING - ANALYSES AND IMPLICATIONS

The ability of an intravascular ultrasound catheter to give cross-sect ional images of vessel walls and surrounding tissues, and the behavior of ultrasound in heterogeneous media, are at the origin of degradatio n of image quality. Qualitative and quantitative analyses of in vivo s tudies are then operator-dependent and are limited by artifacts. We in vestigated these limitations by an in vitro study on plexiglass phanto ms and segments of fresh arteries. We used a 20 MHz transducer mounted on the tip of a 4.8 F catheter and an interventional ultrasound syste m. The ultrasound beam is reflected onto the rotating transducer at 60 0 rotations per minute (RPM), creating 360-degrees real-time images (1 0 images/second). We then observed, analyzed and interpreted the most specific reasons for image artifacts: geometric distortions, multiple echoes, the point spread function (PSF) of the imaging system, near-fi eld effects, ''petal-shaped'' effect, and ultrasound speckle. Various practical implications have resulted from this study. Only a thorough knowledge of how to avoid some of the most obvious pitfalls will enabl e the user to obtain maximum benefits from intravascular ultrasound im aging, and to appreciate its limitations.