降矢 典雄¹, 八木 晋一², 西村 政利³, 小川 研一⁴, 飯塚 昌彦⁴

Norio FURUYA¹, Shinichi YAGI², Masatoshi NISHIMURA³, Kenichi OGAWA⁴, Masahiko IIZUKA⁴

¹東京都立航空工業高等専門学校電子工学科, ²明星大学電子情報学科, ³（株）グッドマン, ⁴獨協医科大学第1内科

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

キーワード : 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.