1Department of Electrical Engineering, Tokyo Metropolitan College of Aeronautical Engineering, 2Department of Electronics and Computer Sciences, Meisei University Faculty of Information Science, 3East Japan Office, Goodman Corporation Limited, 4First Department of Internal Medicine, Dokkyo University School of Medicine
Intravascular ultrasound , Range-variant inverse filter , Two-dimensional point spread function
We attempted to use the intravascular ultrasound system (IVUS) to diagnose vascular diseases. The images produced by
conventional systems provide valuable clinical information. Despite the good resolution that can be obtained around the focal
point of the ultrasound beam with this system, however, resolution farther from the focal point remains insufficient, and
deciphering vascular structures in the vicinity of the catheter is especially difficult. This problem can generally be attributed to
two primary factors: First, the acoustic near-field effect of the transducer is not negligible; second, multiple echoes are
produced by a catheter sheath. To solve these problems, we desigrned a two-dimensional range-variant inverse filter by
measnring in advance the two-dimensional range-variantpoint-spread function (psf) of the measurement system with a thin
tungsten wire as a standard reflector. The application of inverse filtering to the two-dimensional IVUS echo enabled us to obtain
images of a constant high resolution equivalent to the resolution at the focal point throughout the entire image region.
Moreover, remarkable improvement in image quality was noticed in the near-field region of the transducer.