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英文誌(2004-)

Journal of Medical Ultrasonics

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1996 - Vol.23

Vol.23 No.05

Original Article(原著)

(0341 - 0348)

不等間隔超音波パルス送波による高限界速パルスドプラ計測法におけるMTIフィルタの検討

MTI Filter in Non-equally Spaced Pulse Transmission for Non-aliasing Ultrasonic Pulsed Doppler Measurement

西山 久司1, 片倉 景義2

Hisashi NISHIYAMA1, Kageyoshi KATAKURA2

1(株)日立製作所本社, 2(株)日立製作所情報通信事業部

1Head Office Hitachi, Ltd., 2Telecommunications Division Hitachi, Ltd.

キーワード : MTI filter, Non-aliasing, Nyquist frequency, Pulsed Doppler, Non-equally spaced pulse transmission

Non-equally spaced pulse transmission in pulsed Doppler ultrasonography is a method for measuring velocity of blood flow that is not subject to the Nyquist limit; transmission of non-equally spaced ultrasonic pulses to a blood vessel in vivo makes it possible to measure blood velocity that exceeds the Nyquist limit unambiguously and without aliasing. For removal of clutter from the imaged blood vessel, a new design principle, that of a moving target indication (MTI) filter capable of processing non-equally spaced pulse transmission sequences, is discussed. Two approaches toward delay time in the MTI filter are proposed: Sum-PRT-MTI and Respective-PRT-MTI; addition times and respective times between two pulse repetition times (PRT) must be applied for this purpose. A phase comparator was used to test the proposed method analytically with model Doppler signals. The method was also verified experimentally using computer-simulated Doppler signals to which white noise had been added. We then compare the proposed MTIs for color flow mapping (CFM) and discuss the characteristics of these filters.