Hitachi Medical Corporation

Hitachi, Ltd.

Hisashi Nishiyama

Kageyoshi Katakura

Toshio Ogawa

Shizuo Ishikawa

Hiroshi Kanda

Satoshi Tamano

Koji Tanabe

Shinichiro Umemura

Ryuichi Shinomura

Yasuhiro Hashimoto

Mashio Kodama

Ishikawa Shizuo

An ultrasonic flow mapping apparatus transmits and reflects waves from sampling points on a two-dimensional cross-section. The waves are detected while transmitting repeatedly ultrasonic pulses. The phase shifts of different reflected waves are calculated, and displayed in color to show a distribution of blood flow velocity. Artifact due to reflected waves from body organs, which remain even by using MTI filters, is detected from phase signals, which have not passed through the MTI filters, and the artifact is removed by lowering display brightness for a sampling point corresponding to a relevant detection output.

Apparatus for ultrasonic color flow mapping

A flow meter for detecting a flow speed in such a manner that an ultrasonic pulsed continuous wave is repeatedly transmitted toward an object at predetermined intervals T, a phase vector indicative of the phase of a reception signal due to the reflected wave is produced at the predetermined intervals, the phase difference between the present phase vector and the preceding phase vector is detected, and a Doppler frequency is calculated from the average value of a plurality of phase difference values to obtain the speed of the object. The phase difference values are classified into a first group consisting of position phase difference values and a second group consisting of negative phase difference values, the cosine and sine values of the central angle of the positive phase difference values and the cosine and sine values of the central angle of the negative phase difference values are calculated, and the argument of a vector indicated by the weighted sum of cosine values and the weighted sum of sine values is calculated to be used as an average phase angle.

Ultrasonic Doppler flow meter

The present invention relates to a pulse Doppler measuring apparatus using the so-called acceleration method. In order to prevent production of a secondary aliasing (where a phase vector is subjected to an aliasing), the apparatus is provided with an MTI filter, which decomposes a first phase vector of a reflected wave obtained by mixing a reflection signal with a reference signal into a real part and an imaginary part, obtains a first regression line for variations of each of the parts and extracts a second phase vector corresponding only to the high frequency component of the reflected wave by calculating differences of the real part and the imaginary part from the first regression line; and/or an angular component .DELTA..theta. of the phase difference vector is obtained; a second regression line is obtained for this phase difference angle .DELTA..theta.; and the phase difference angle .DELTA..theta. is corrected by using this second regression line, to prevent the production of a secondary aliasing.

Pulse doppler measuring apparatus

A flow meter for detecting the average speed of an object in such a manner that an ultrasonic pulsed continuous wave is repeatedly transmitted toward the object to obtain a phase vector from the reception signal of the wave reflected from the object, the phase difference between consecutive ones of phase vectors obtained at an interval T equal to the period of transmitted wave is detected, a plurality of phase difference values are added and averaged to obtain an average phase difference value, and a Doppler frequency is calculated from the average phase difference value to obtain the average speed of the object, in which in order to remove an error caused by aliasing of an angle in the course of the arithmetic operation for obtaining the average phase difference value, a plurality of presumed average phase difference values having the error are calculated from the average phase difference value, the difference between the change of a phase caused by adding the phase difference values successively and the change of phase based upon each of the presumed average phase difference values is estimated to select the most appropriate one of the presumed average phase difference values, and the selected average phase difference value is used as a corrected average phase difference value.

Ultrasonic doppler flow meter

In a pulse Doppler flow speed meter in which ultrasonic wave pulses are transmitted repetitively at transmission intervals T and thereafter transmitted repetitively at transmission intervals (T+Ts), phases of reflected waves due to reflection of individual transmission pulses are measured sequentially to provide phase signals and the phase signals are subjected to frequency analysis to determine speed distributions, distributions of phase differences between phase signals corresponding to transmission pulses transmitted at the transmission intervals T and distributions of phase differences between phase signals corresponding to transmission pulses transmitted at the transmission intervals (T+Ts) are determined. A value of center of gravity of the former phase difference distributions and a value of center of gravity of the latter phase difference distributions are determined and then a phase difference between the two values of center of gravity is determined. Obtained from the phase difference are values of Doppler shift angle, according to which the former and latter phase difference distributions are shifted so as to be compensated for their aliasing.

Pulse doppler flow speed meter

A pulse doppler apparatus transmits a ultrasonic sound wave at transmission intervals T and T+Ts alternately and iteratively, detects the phase difference attributable to the doppler shift in the reflected sound wave signal at the interval T and the phase difference in the reflected signal at the interval T+Ts sequentially, detects the difference between both phase differences, and transforms the difference into a doppler frequency. The apparatus includes an MTI filter which exerts the same filtering characteristics on the reflected sound signals at both intervals T and T+Ts.

A flow meter, in which pulsed continuous ultrasonic wave is transmitted towards an object at predetermined intervals T to obtain a phase vector from a reception signal of wave reflected by the object and which calculates a Doppler frequency from the average value of phase differences between phase vectors at the sampling interval T to obtain a signal indicating the speed of the object, comprising a phase difference calculator by the auto-correlation method, by which a plurality of phase difference vectors indicating phase differences between phase vectors are added, the argument of the sum vector thus obtained representing the average phase difference, or a phase difference calculator by the 2-axial-component method, by which a phase difference is divided into 2 axial components, a cosine value and a sine value, and the average phase difference is obtained by using the average value for each of the components, and a phase difference calculator by the phase difference averaging calculator, by which a plurality of phase differences are added, as they are, to obtain the average thereof, in order to obtain a phase difference average value having small errors by switching them.

A ultrasonic Doppler meter for measuring the speed of a moving body by measuring the phase shift due to the Doppler effect on received signals, comprising a transmitting/receiving unit transmitting ultrasonic bursts with a constant time interval towards the moving body and receiving reflected waves; a unit for measuring a phase difference vector representing a difference between phases of received signals corresponding to two successive transmitted pulses; a unit for calculating a difference between phase differences on the basis of two successive phase difference vectors stated above; and an accumulation unit for adding the difference between phase differences to a preceeding phase difference vector so as to obtain the speed of the moving object.

Ultrasonic doppler meter

A phase difference comparison type of ultrasonic velocity meter repeatingly transmitting acoustic waves in the form of pulses at alternate time intervals: T-T.sub.S and T+T.sub.S, receiving reflected waves generated by the transmission of these waves and reflected on an object, forming first and second mixed waves by mixing the reception signal obtained from the reflected waves with two reference waves having phases shifted 90 degrees from each other, detecting the phase difference between the present vectors representing the first and second mixed waves and similar vectors which have been obtained with respect to the preceding pulse transmission, detecting the phase difference Q between the phase difference caused in relation to the time interval T-T.sub.S and the phase difference caused in relation to the time interval T+T.sub.S with respect to a phase difference obtained each time a pulse is transmitted, and calculating the Droppler shift angle frequency .omega.d from .omega.d=Q/2T.sub.S.

Growing community of inventors

Tokyo, Japan

Hisashi Nishiyama