Communications – electrical: acoustic wave systems and devices – Echo systems – Speed determination
Patent
1990-02-28
1991-04-23
Lobo, Ian J.
Communications, electrical: acoustic wave systems and devices
Echo systems
Speed determination
7386125, 12866109, G01S 1500, G01F 166, A61B 806
Patent
active
050105280
DESCRIPTION:
BRIEF SUMMARY
Technical Field
The present invention relates to a Doppler flow velocity measuring apparatus and, more particularly, to a Doppler flow velocity measuring apparatus which is capable of obtaining the two-dimensional velocity distribution of a fluid on a predetermined transverse section by one beam scanning of said transverse section.
Background Art
A Doppler velocity measuring apparatus for obtaining the flow of a fluid or the movement of a moving member in an object being examined by utilizing a Doppler effect is known. By this apparatus, an ultrasonic or electromagnetic wave, especially, a pulsating burst wave is transmitted to the object being examined, and a reflected echo is obtained at each point in the direction of the beam so as to utilize a Doppler effect. This method is widely utilized as a pulse-Doppler method.
Such a velocity measurement method is useful for knowing the flow velocity vector distribution in a predetermined transverse section being observed which is composed of a plane or a curved surface by scanning the transverse section with the transmitted beam. This method is very useful for knowing the movement of clouds by using an electromagnetic wave, and the bloodstream velocity distribution in the heart of the body by using an ultrasonic wave. Especially, in the latter case, it is possible to observe the bloodstream distribution without invasion and produce excellent results on the diagnosis of the function of the heart and the like.
As is well known, according to this kind of pulse-Doppler method, since the frequency of a received signal deviates depending upon the movement of a reflecting member, the velocity distribution of a fluid along each point of the an ultrasonic beam is obtained from the deviated frequency (Doppler frequency) obtained by comparison between the frequencies of the transmitted signal and the received signal. The pulse-Doppler method, however, suffers from the serious problem that the velocity information obtained from the pulse-Doppler method only provides a velocity component in the direction of a beam.
Therefore, even if two-dimensional velocity distribution information is obtained by moving the pulse beam along a predetermined transverse section by the mechanical movement of a probe or electronic linear or sector scanning, since the information obtained only contains the component in the direction of the beam, the velocity and the acceleration distribution in the displayed image obtained from the information and the pressure distribution in the closed region obtained from the velocity information of each pixel contain a large innegligible error.
In order to obtain a component in a direction different from the direction of a beam in the transverse section plane scanned with the beam, a method of obtaining the correlation of the data in the directions of adjacent beams is conventionally investigated. However, such calculation of the correlation makes the apparatus complicated and since the processing speed is lowered, the amount of data observable per unit time is reduced.
The present inventors proposed a method of using an advective accelerating component of a fluid in order to infer the velocity component data in a direction different from the direction of an ultrasonic wave, the direction orthogonal thereto in ordinary case, in Japanese Patent Application Nos. 236919/1987 and 236920/1987.
According to the above-described related art, a plurality of burst waves are transmitted from an ultrasonic probe to a fluid at a predetermined recurrence period, the echo obtained from the fluid is received by the ultrasonic probe and the flow velocity component data (hereinunder referred to as "Doppler velocity") at each point in the direction of the beam is obtained from the received signal every moment by utilizing the above-described Doppler effect.
The Doppler velocities obtained are sequentially stored in a memory, and the points which satisfy the conditions for obtaining the advective acceleration component are obtained from the thus-stored two-dimensional informa
REFERENCES:
patent: 4744367 (1988-05-01), Kodone et al.
patent: 4759375 (1988-07-01), Namekawa
patent: 4790322 (1988-12-01), Iiuuma
Ohtsuki Shigeo
Tanaka Motonao
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