JP2006254984A - Ultrasonic doppler blood flowmeter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a doppler blood flowmeter capable of generating ultrasonic images in which striped patterns are not displayed even when it is operated by a parallel reception method. <P>SOLUTION: For the combined focuses F1 and F2 of a transmission beam TX and a reception beam, in order to equalize an angle θb from the combined focus F1 to the center of a transmission opening and an angle θa from the combined focuses F1 and F2 to the opening center 22c of reception openings 22R and 22L with the direction of the transmission beam TX as a reference, the positions of the reception openings 22R and 22L are set. By matching the directions of a transmission/reception combined beam B1 and a transmission/reception combined beam B2 with the transmission beam TX, a difference between the beams of doppler shift is eliminated. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ultrasonic Doppler blood flow meter that observes the flow of a moving object such as a blood cell.

  Conventionally, blood flow measurement technology based on the Doppler method has been used to measure the moving speed of a reflective object such as blood cells that move in a living body based on the Doppler shift frequency generated by the Doppler effect with respect to ultrasonic beam irradiation. The ultrasonic diagnostic apparatus having this blood flow measurement technique can display morphological information such as an organ in a living body, blood flow, and the like depending on the type of signal processing. In recent years, studies have been made on enhancing the harmonic component of an ultrasonic signal and evaluating blood flow dynamics by using a contrast agent that generates microbubbles.

  As a conventional ultrasonic diagnostic apparatus, a plurality of ultrasonic transducers are arranged in an array, and some of the ultrasonic transducers are operated as a set, and the set is sequentially switched, It is well known that the beam is scanned electronically. Furthermore, in order to enable real-time observation of an image with a high scanning line density, the direction of ultrasonic reception is directed to one ultrasonic transmitter. There is also known a system in which a plurality of receiving systems whose characteristics are shifted by a minute amount are provided to perform parallel reception (see, for example, Patent Document 1).

  FIG. 5 is a block diagram of a conventional ultrasonic diagnostic apparatus having a function of knowing blood flow information (hereinafter referred to as an ultrasonic Doppler blood flow meter).

  In the figure, a probe 101 converts an electric pulse generated by a transmitter 102 into an ultrasonic wave, and irradiates the ultrasonic wave into a body not shown. The ultrasonic wave irradiated here is reflected by a reflecting object (for example, an organ, a blood vessel, etc.) in the body to be inspected, and returns to the probe 101.

  The returned ultrasonic wave is received by the probe 101 and converted into an electrical signal, passed through the receiver 103 (reception means), and signal processing based on a color Doppler method, which is a method of ultrasonic Doppler blood flow measurement. Are input to the color flow signal processing unit 104 that executes the above and the B-mode signal processing unit 105 that sets the ultrasonic image display mode to the B mode.

  The signal input to the color flow signal processing unit 104 is subjected to quadrature detection by the quadrature detector 106 and is taken into the memories 107a and 107b. In this color flow signal processing, signals of the same part are accumulated several times, and blood flow information is obtained from the change in phase. Transmission / reception and quadrature detection are performed several times to about a dozen times for the same part and stored in the memories 107a and 107b.

  In addition, a signal of the same part is output from the signals accumulated in the memories 107a and 107b and input to MTI (Moving Target Indicator) filters 108a and 108b. The MTI filters 108a and 108b are a kind of high-pass filter. There are two types of signals returned from the body to be inspected: one from blood and one from blood vessel walls and organs. One from blood has a large phase change, and one from blood vessels and organs has a phase change. small. Accordingly, only blood information can be extracted by the high-pass filter.

  The outputs of the MIT filters 108a and 108b are input to the correlation calculator 109. The correlation calculator calculates the magnitude of the phase change, that is, the velocity and amplitude of the blood flow, by performing an autocorrelation calculation of the signal.

  Here, the relationship between the direction of transmission / reception with respect to the direction of blood flow and the calculated blood flow velocity will be described. As shown in FIG. If the blood flow velocity is V, the velocity V1 calculated by the correlation calculator 109 is V1 = V · cos θ. Therefore, if the ultrasonic beam and the direction of blood flow are orthogonal, V1 is always zero and blood flow is not detected.

  On the other hand, the B-mode signal processing unit 105 extracts amplitude information using the detector 110. Envelope detection is often used as the detection method here.

  The blood flow information obtained by the color flow signal processing unit 104 and the amplitude information obtained by the B-mode signal processing unit are combined into one image information by the digital scan converter (DSC) 111, and the image information is displayed on the display. 112.

  In order to construct a two-dimensional image, a method of performing transmission / reception by shifting the position of the opening little by little is used. Since the actual two-dimensional scanning is publicly known, it is omitted, but recently, a method of performing electrical switching has become mainstream.

  As described above, when obtaining blood flow information, several to dozens of signals of the same part are accumulated. In order to accumulate signals of the same part, it is necessary to perform transmission / reception for the same part as many as the number to be accumulated. If the same part is transmitted and received many times, there is a problem that it takes a long time to complete one two-dimensional scan and the real-time property is lost. A parallel reception method has been devised to solve this problem. ing. The parallel reception method is described in Patent Document 1, for example, and uses a plurality of reception beams for one transmission beam. The parallel reception method will be described with reference to FIG.

  FIG. 7 shows an example of the parallel reception method. In the figure, there are two reception beams. There is an aperture 114, and the aperture centers of transmission and reception are the same (in an actual apparatus, the transmission aperture width and the reception aperture width are often different, but here the same aperture width is used to simplify the explanation. ). A transmission beam is irradiated from the center of the aperture perpendicular to the aperture. Considering the beam formation at the point of the depth d, at the depth d, the two reception beams (RX1, RX2) are distributed to the left and right from the transmission beam in minute angles. If the focal point of the transmission beam at the depth d is Ftx and the focal points of the reception beam are Frx1 and Frx2, the transmission and reception synthetic focal points F1 and F2 are located between the transmission focal point and the reception focal point, for example, reception and transmission beam focusing. When the degree is the same, it is intermediate between the transmission focus and the reception focus.

By simultaneously receiving signals from two directions in this way, the number of transmissions / receptions required for one image can be reduced, and an image with high real-time properties can be provided.
Japanese Patent Publication No.56-20017

  However, the conventional ultrasonic Doppler blood flow meter using the parallel reception method as described above has the following problems.

  In ultrasonic Doppler blood flow measurement using a conventional parallel reception method, as shown in FIG. 8, if transmission / reception is performed using an opening 114, blood vessels run at right angles to the transmission beam and blood flows. Sometimes, the Doppler shift does not occur in the perpendicular direction, and the flow should not be detected.

  However, since the reception beams RX1 and RX2 are formed in a shape opened by a minute angle to the left and right with respect to the transmission beam TX, the composite beam 1 and the composite beam 2 intersect the blood vessel at angles of φ1 and φ2, respectively. It will be.

  φ1 is larger than 90 degrees and φ2 is small. Therefore, the detected flow is reversed between the reception beam 1 and the reception beam 2.

  Therefore, as shown in FIG. 9, if scanning is sequentially performed at each opening position, the reception beam 1 at each scanning position displays a forward flow, and the reception beam 2 displays a reverse flow. A striped image is displayed.

  An object of the present invention is to solve the above-mentioned problems and to provide a Doppler blood flow meter capable of generating an ultrasonic image in which no stripe pattern is displayed on the image even when operated by the parallel reception method. Is.

  The inventor of the present invention has reached the idea that the above-mentioned problem can be solved by moving the position of the reception beam by a predetermined interval from the transmission aperture, and has made the present invention. The position of the reception aperture is separated from the transmission aperture by a predetermined interval so that the directions of a plurality of transmission / reception combined beams are the same.

  That is, the Doppler blood flow meter of the present invention comprises receiving means for obtaining two or more receiving beams simultaneously for one transmitting beam, and the receiving means transmits and receives from the center of the transmitting aperture with respect to the direction of the transmitting beam. The position of the reception aperture is set so that the angle formed by the direction toward the synthesis focus and the angle formed by the direction from the center of the reception aperture toward the transmission / reception synthesis focus with respect to the direction of the transmission beam are equal. With this configuration, the directions of the two transmission / reception combined beams are the same at a predetermined depth.

  The Doppler blood flow meter according to the present invention further includes receiving means for obtaining two or more receiving beams simultaneously with respect to one transmission beam, and the receiving means transmits and receives from the center of the transmission aperture with respect to the direction of the transmission beam. The weight of the sensitivity of the reception aperture is set so that the angle formed by the direction toward the synthetic focus is equal to the angle formed by the direction toward the transmission / reception synthetic focus from the apparent center of the reception aperture with respect to the direction of the transmission beam. And In this case, by weighting the reception aperture, the directions of the two transmission / reception combined beams are the same at a predetermined depth.

  In the Doppler blood flow meter of the present invention, it is preferable that the receiving unit performs dynamic focusing. In this case, the directions of the two transmission / reception combined beams are the same at all depths, and stable variable depth flaw detection can be performed.

  ADVANTAGE OF THE INVENTION According to this invention, when performing ultrasonic Doppler blood flow measurement using parallel reception, it is possible to align the directions of parallel beams, prevent the generation of stripes in an ultrasonic image, and provide accurate blood flow information. An ultrasonic Doppler blood flow meter can be provided. As a result, for example, when performing diagnosis of the cervix, an ultrasonic diagnostic apparatus that can prevent damage to the subject can be realized without causing the cervical part to be compressed with excessive pressure even by an unfamiliar operator. .

  Hereinafter, a preferred embodiment of the present invention will be described with reference to FIGS.

(First embodiment)
FIG. 1 is an explanatory diagram showing the ultrasonic Doppler blood flow meter according to the first embodiment of the present invention when performing parallel reception.

  In this embodiment, the transmitter, which is a pulse signal generating means for generating a transmission beam, and the signal processing system for forming an ultrasonic image from the received reflected echo signal are shown in FIG. The probe is configured in substantially the same manner as a conventional ultrasonic Doppler blood flow meter, and the internal configuration of a probe as an inspection head including a transmission aperture and a reception aperture described below is different from the conventional example shown in FIG.

  Therefore, this difference will be described in detail below, and the signal processing system and the like will be briefly described with reference to the symbols used in FIG.

  The probe 20 constituting a part of the ultrasonic Doppler blood flow meter of the present embodiment converts the electric pulse generated by the transmitter 102 into an ultrasonic wave, and irradiates the ultrasonic wave in a not-shown body. The ultrasonic wave irradiated here is reflected by a reflecting object (for example, an organ, a blood vessel, etc.) in the body to be inspected, and returns to the probe 20. The returned ultrasonic wave is received by the probe 20 and converted into an electrical signal, and the color that executes signal processing based on the color Doppler method, which is a method of ultrasonic Doppler blood flow measurement, is passed through the receiver 103. The signals are input to the flow signal processing unit 104 and the B mode signal processing unit 105 for setting the ultrasonic image display mode to the B mode. In the color flow signal processing unit 104, the input signal is subjected to quadrature detection by the quadrature detector 106, and the signals of the same part are accumulated several times in the memories 107a and 107b, and blood information is stored in the MTI filters 108a and 108b from the accumulated information. Are extracted, and the velocity and amplitude of the blood flow are calculated by the autocorrelation calculation of the signal in the correlation calculator 109.

  As shown in FIG. 1, the probe 20 includes a transmission aperture 21 having a transmission aperture center 21c, and first and second reception apertures 22L and 22R (left and right in the drawing). The transmission beam TX is irradiated in a direction perpendicular to the transmission aperture 21 from the aperture center 21c of the transmission aperture 21. The first and second reception openings 22L and 22R are arranged on the left and right sides in the drawing with respect to the opening center 21c of the transmission opening 21, and each has an opening center 22c.

  In the following description, the description will be given by taking the reception opening 22L as any one of the reception openings 22L and 22R as an example.

  As shown in FIG. 1, the opening center 22 c of the reception opening 22 </ b> L is not at the same position as the opening center 21 c of the transmission opening 21 in the left-right direction in the drawing (an arbitrary direction along the opening surface).

  Specifically, at a predetermined depth d from the lower surface of the transmission aperture 21 in the drawing, the irradiation direction of the transmission beam TX (see FIG. 5) with respect to the first synthetic focus F1 located between the transmission focus Ftx and the reception focus Frx1. The position of the opening center 22c of the receiving opening 22L is set so that θa = θb in FIG. 1 with reference to the middle transmission / reception synthetic opening center). That is, transmission / reception synthesis is performed from the transmission aperture center 21c with respect to the direction of the transmission beam TX (downward in the figure) so as to constitute a reception means for obtaining two or more reception beams B1 and B2 simultaneously for one transmission beam TX. An angle θb formed by a direction line obliquely downward toward the focal point F1 (solid line inclined in the clockwise direction in the figure) b and a direction line (in the figure) from the reception aperture center 22c toward the transmission / reception synthetic focal point F1 with respect to the direction of the transmission beam TX. The positions of the opening centers 22c of the receiving openings 22L and 22R are set so that the angle θa formed by the solid line (a) which is inclined counterclockwise is equal to each other.

  As a result, the directions of the transmission / reception combined beams B1 and B2 at the depth d coincide with the irradiation directions of the transmission beams TX, respectively. That is, the transmission / reception combined beam B1 and the transmission / reception combined beam B2 are parallel to each other, and no difference in Doppler shift due to the angle difference occurs, and no stripe pattern is generated in the image.

  As described above, the Doppler blood flow meter of the present embodiment includes receiving means for obtaining two or more receiving beams B1 and B2 simultaneously with respect to one transmitting beam TX, and these receiving means determine the direction of the transmitting beam TX ( The angle θb formed by the direction from the transmission aperture center 21c toward the transmission / reception synthetic focal point F1 is equal to the angle θa formed by the direction from the reception aperture center 22c toward the transmission / reception synthetic focal point F1 with respect to the direction of the transmission beam TX. Thus, by setting the position of each reception aperture 22L, the directions of the two transmission / reception combined beams B1 and B2 are the same at a predetermined depth d.

  Therefore, when performing ultrasonic Doppler blood flow measurement using parallel reception, it is possible to align the directions of parallel beams, prevent the occurrence of stripes in conventional ultrasonic images, and have high accuracy. An ultrasonic Doppler blood flow meter that can provide blood flow information can be provided. As a result, when diagnosing the cervix, etc., a striped pattern is generated, so that an operator unfamiliar with the cervix is not compressed with excessive pressure, and the effect of preventing damage to the subject can be expected. .

(Second Embodiment)
FIG. 2 is an explanatory diagram showing the ultrasonic Doppler blood flow meter according to the second embodiment of the present invention when performing parallel reception.

  Also in this embodiment, a transmitter which is a pulse signal generating means for generating a transmission beam and a signal processing system for forming an ultrasonic image from a received reflected echo signal are shown in FIG. The probe is configured in substantially the same manner as the conventional ultrasonic Doppler blood flow meter, and the internal configuration of the probe as an inspection head including a transmission aperture and a reception aperture described below is different from the conventional example shown in FIG. Therefore, this difference will be described in detail below, and the signal processing system and the like will be briefly described with reference to the symbols used in FIG.

  The probe 30 that constitutes a part of the ultrasonic Doppler blood flow meter of the present embodiment converts the electric pulse generated by the transmitter 102 into an ultrasonic wave, and irradiates the ultrasonic wave into a body not shown. The ultrasonic wave returned to the probe 20 as a receiving means is received by the probe 30 and converted into an electrical signal, and the color flow signal processing unit 104 and the B-mode signal processing unit are passed through the receiver 103. 105, respectively.

  As shown in FIG. 2, the probe 30 includes a transmission opening 31, and the transmission opening 31 has an opening center 31 c. An ultrasonic transmission beam TX is irradiated in a direction perpendicular to the opening surface of the transmission opening 31 from the opening center 31 c of the transmission opening 31.

  Although only one side is shown in FIG. 2, the reception openings 32L and 32R (reception means) are located between the opening center 31c of the transmission opening 31 in the same manner as the reception openings 22L and 22R of the above-described embodiment. They are arranged symmetrically on both sides (left and right sides in the figure) with a sandwich, and each has an opening center 32c. The receiving opening 32L shown on the left side in FIG. 2 and the receiving opening 32R located on the opposite side (right side) with respect to the opening center 31c are configured in the same manner except that they are bilaterally symmetric.

  In the probe 30 of the present embodiment, the geometric centers of the left and right reception openings 32L and 32R are the same position as the opening center 31c of the transmission opening 31.

  However, the right and left reception openings 32L and 32R of this embodiment are weighted as shown above the transmission opening 31 in FIG. The center (at the time) is at a position different from the opening center 31 c of the transmission opening 31.

  Specifically, for example, the signal level ratio at the time of receiving the reception signal into the receiver 103 is set so that the sensitivity of the reception opening 32L on one side is higher or lower than the sensitivity of the other reception opening 32R.

  At a predetermined depth d, the reception aperture 32L is set so that θa = θb in FIG. 2 when the direction of the transmission beam TX is used as a reference with respect to the synthetic focus F1 positioned between the transmission focus and the reception focus. The apparent center position of 32R is set.

  Thus, the direction of the transmission / reception combined beam B1 at the depth d matches the direction of the transmission beam TX.

  That is, the transmission / reception combined beam B1 and the transmission / reception combined beam (not shown in the figure, which is not shown in the figure) are parallel to each other, and a difference in Doppler shift due to the angle difference is not generated. In other words, the striped pattern does not occur in the image.

  As described above, in the Doppler blood flow meter of the present embodiment, the receiving means for obtaining two or more reception beams at the same time for one transmission beam TX is from the opening center 31c of the transmission aperture 31 with respect to the direction of the transmission beam TX. Reception is performed such that the angle θb formed in the direction toward the transmission / reception synthetic focus F1 is equal to the angle θa formed in the direction toward the transmission / reception synthetic focus F1 from the apparent aperture center 32c of the reception apertures 32L and 32R with respect to the direction of the transmission beam TX. By setting the weighting of the sensitivity of the openings 32L and 32R, the directions of the two transmission / reception combined beams B1 and B2 become the same at a predetermined depth d.

(Third embodiment)
FIG. 3 is an explanatory diagram showing a change in the synthesized focal position depending on the depth in the case of performing parallel reception showing an ultrasonic Doppler blood flow meter according to the third embodiment of the present invention. Also in this embodiment, a transmitter which is a pulse signal generating means for generating a transmission beam and a signal processing system for forming an ultrasonic image from a received reflected echo signal are shown in FIG. The probe is configured in substantially the same manner as the conventional ultrasonic Doppler blood flow meter, and the internal configuration of the probe as an inspection head including a transmission aperture and a reception aperture described below is different from the conventional example shown in FIG. Therefore, this difference will be described in detail below, and the signal processing system and the like will be briefly described with reference to the symbols used in FIG.

  The first and second embodiments described above have a feature of how to center the receiving aperture at a specific depth, whereas they constitute a part of the ultrasonic Doppler blood flow meter of the present embodiment. The probe 40 (see FIG. 3) is characterized by how to center the receiving opening 41 at all depths.

  In the probe 40 (reception means), the transmission beam TX is focused at the depth of focus due to the nature of the probe beam TX, and the focusing degree is low at a shallower part and a deeper part. On the other hand, the left and right reception beams RX1, RX2 in the figure (only the reception beam R1 on the left side in the figure is shown as a whole, but the reception beam RX2 exists in a symmetrical position with respect to the transmission beam TX) is By adopting a dynamic focus method, that is, a variable depth flaw detection method, it is possible to focus the beam at all depths. As a result, the positions of the combined beams B1 and B2 are close to the transmission beam TX in the vicinity of the focus Ftx of the transmission beam TX, and the reception beams RX1 and RX2 (reception beams on the opposite side of RX1) are shallower or deeper than that. Close to the position.

  Here, the parallel reception process of the ultrasonic Doppler blood flow meter according to the third embodiment will be described.

  Since the composite focus F1 meanders as shown in FIG. 3, the transmission beam direction is used as a reference at each depth in accordance with the position of the composite focus F1 at each depth as shown in FIG. The positions of the receiving openings 42L and 42R (receiving means) are set so that the angles θa and θb are equal. That is, the reception opening position adjusting means 45 that can approach and separate the positions of the reception openings 42L and 42R from the opening center 41c of the transmission opening 41 is provided.

  Thus, at all depths, the direction of the transmission / reception combined beam B1 matches the direction of the transmission beam TX. That is, the transmission / reception combined beam B1 and the transmission / reception combined beam B2 are parallel to each other, and a difference in Doppler shift due to the angle difference between the beams B1 and B2 with respect to the transmission beam TX does not occur, and a stripe pattern is generated in the ultrasonic image. Is prevented.

  As described above, in the Doppler blood flow meter of the present invention, the receiving means including the receiving openings 42L and 42R uses the receiving opening position adjusting means 45 to perform dynamic focusing. Therefore, the directions of the two transmission / reception combined beams B1 and B2 are the same at each depth. As a result, stable variable depth flaw detection can be performed.

  FIG. 4 shows a dynamic focus type probe 150 of a comparative example.

  As shown in the figure, the transmission beam TX that exits from the aperture center 151 of the transmission / reception aperture 154 is narrowed in the depth of focus due to its nature, while the focusing degree is lower at shallower and deeper sites. The reception beams RX1 and RX2 can focus the beams at all depths by adopting the dynamic focus method. Therefore, the positions of the combined beams B1 and B2 are close to the transmit beam TX near the focal point Ftx of the transmit beam TX, and close to the receive beams RX1 and RX2 at shallower or deeper portions.

  However, as described in FIG. 8 as a conventional problem, the detected flow is reversed between the reception beam RX1 and the reception beam RX2, and the problem that a striped image is displayed cannot be solved.

  In contrast, the ultrasonic Doppler blood flow meter according to the embodiment of the present invention can solve such a problem.

  In the third embodiment, the directions of the transmission / reception combined beams B1 and B2 are adjusted by shifting the positions of the reception openings 42L and 42R. However, as shown in the second embodiment, left and right receptions are performed. It is also possible to move the center of the apparent reception aperture by weighting the apertures 42L and 42R, and thereby the same effect as described above for the third embodiment can be obtained.

  As described above, the present invention can align the directions of parallel beams when performing ultrasonic Doppler blood flow measurement using parallel reception, prevent the generation of stripes in an ultrasonic image, and provide accurate blood. This has the effect of providing an ultrasonic Doppler blood flow meter that can provide flow information, and is useful for all ultrasonic Doppler blood flow meters that observe the flow of moving objects such as blood cells.

It is a typical block diagram of the principal part of the ultrasonic Doppler blood flow meter which concerns on the 1st Embodiment of this invention, Comprising: The explanatory view of the parallel reception method Explanatory drawing of the parallel reception method showing an ultrasonic Doppler blood flow meter according to the second embodiment of the present invention Explanatory drawing of the parallel reception method which shows the ultrasonic Doppler blood flow meter concerning a 3rd embodiment of the present invention Explanatory drawing of the parallel reception method showing an ultrasonic Doppler blood flow meter of a comparative example Block diagram of an ultrasonic diagnostic apparatus including a conventional ultrasonic Doppler blood flow meter Explanatory drawing about measurement of conventional ultrasonic Doppler blood flow meter Illustration of parallel reception method in the conventional example Explanatory diagram of problems with the parallel reception method in the conventional example Transmission / reception aperture arrangement explanatory drawing of the conventional ultrasonic Doppler blood flow meter

Explanation of symbols

20, 30, 40 Probes 21, 31, 41 Transmitting apertures 21c, 31c, 41c Opening centers 22L, 22R, 32L, 32R, 42L, 42R Receiving apertures (receiving means)
22c, 32c, 42c Center of aperture 102 Transmitter 103 Receiver 104 Color flow signal processing unit 105 B-mode signal processing unit 106 Quadrature detector 107a, 107b Memory 108a, 108b MTI filter 109 Correlation calculator 110 Detector 111 DSC (digital scan) converter)
112 Display 113 Blood vessel 114 Opening

Claims (3)

Receiving means for simultaneously obtaining two or more receiving beams for one transmitting beam;
The receiving means has an angle (θa) formed by a direction from the center of the transmission aperture toward the transmission / reception synthetic focal point with respect to the direction of the transmission beam and a direction from the center of the reception aperture toward the transmission / reception synthetic focal point with respect to the direction of the transmission beam. An ultrasonic Doppler blood flow meter, wherein the position of the receiving opening is set so that the angle (θb) formed is equal. Receiving means for simultaneously obtaining two or more receiving beams for one transmitting beam;
The receiving means forms an angle between the direction of the transmission beam and the direction from the center of the transmission aperture toward the transmission / reception synthesis focal point and a direction from the apparent center of the reception aperture toward the transmission / reception synthesis focal point with respect to the direction of the transmission beam. An ultrasonic Doppler blood flow meter, wherein the weighting of the sensitivity of the receiving aperture is set so that the angle is equal. The ultrasonic Doppler blood flow meter according to claim 1, wherein the receiving unit performs dynamic focusing.

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