JPH082358B2 - Ultrasonic Doppler blood flow meter - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic Doppler blood flow meter capable of simultaneously performing ultrasonic imaging and pulse Doppler velocity measurement.

2. Description of the Related Art Recently, an ultrasonic Doppler blood flow meter that simultaneously displays a Doppler sonargram and a tomographic image in real time by combining the ultrasonic pulse Doppler measurement method and the pulse reflection method has been actively used for diagnosis of a biological cardiovascular system. It has come to be used. This ultrasonic Doppler blood flow meter is disclosed, for example, in JP-A-55-549.
The configuration described in No. 41 is known. Hereinafter, a conventional ultrasonic Doppler blood flow meter will be described with reference to FIG.

FIG. 9 is a diagram showing the basic principle of the ultrasonic Doppler blood flow meter. In FIG. 9, 90 is a probe, 91 is a transmission scanning circuit, 92 is a reception scanning circuit, 93 is a phase detection circuit, 94 is a frequency analyzer, 95 is an amplitude detection circuit, 96 is a display section, and 97 is a control section. .

Next, the operation of the above conventional example will be described. The drive pulse generated by the transmission scanning circuit 91 is applied to the probe 90, and a sound wave is transmitted in the directions of directivity m ₁ , m ₂ , ..., M _n .
Receiving scanning circuit 92 same directivity m ₁ and transmission, m _2, the receiving sensitivity in the direction of ... it is controlled to be higher. In the Doppler mode, the directivity is fixed in a fixed direction, for example, the directivity is fixed in the m _d direction, transmission and reception are repeated, and the I and Q signals, which are Doppler shift data obtained by phase detection of the received signal, are subjected to frequency analysis. The moving speed of the blood flow in the sample is calculated and displayed on the display unit. In the B mode, transmission / reception is sequentially performed in the directivities m ₁ , m ₂ , ..., And the received signals obtained are subjected to envelope detection by the detection circuit and displayed as a tomographic image on the display unit. The control unit 97 determines whether to select the Doppler mode or the B mode. Normally, when blood flow information and B-mode tomographic image at the sample volume S are simultaneously obtained in the m _d direction, m _j (j
= 1 to n) direction, the control unit 97 alternately performs the Doppler operation in the m _d direction after the B mode operation. Hereinafter, such an operation mode is referred to as a B / D mode.

When the repetition frequency of the transmitted ultrasonic pulse in the Doppler mode is fr, the repetition frequency of the Doppler operation decreases to fr / 2 in the B / D mode, which causes a problem that the measurable maximum blood flow velocity becomes half.

In order to solve this problem, a method for obtaining a B-mode image without lowering the Doppler sampling frequency has been devised. As an example of such a method, the method described in JP-A-61-25534 is known. In this method, for example, in a device having a configuration as shown in FIG. 9, transmission / reception in the Doppler mode is repeated three times, transmission / reception in the B mode is performed once, and interpolation is performed on the I and Q signals of the phase detection output that has passed once. This is based on the principle that the sampling frequency of the Doppler shift data is not lowered by performing the above.

However, the interpolation method used in this method was devised for the processing of speech signals, and frequency components approaching 1/2 of the sample frequency such as Doppler shift data were used. It was not suitable for the interpolation of the included signal. Fig. 10 shows transmission in B mode after repeating transmission in Doppler mode twice.
FIG. 7 shows the state of interpolation by the conventional method in the case of Doppler shift data having a frequency component close to 1/2 of the repetition frequency fr of the transmission pulse.

As shown in FIG. 10, the result of interpolation is completely different from the expected value, and there is a problem that the frequency shifts to a low frequency and correct frequency analysis cannot be performed.

The present invention solves the above problems of the prior art, and is 1/2 of the repetition frequency of the transmission pulse of the Doppler mode.
The purpose of the present invention is to enable accurate interpolation even for Doppler shift data approaching.

Means for Solving the Problems In order to achieve the above object, the present invention provides a control means for suspending Doppler transmission / reception for a certain period after performing ultrasonic Doppler transmission / reception for obtaining a Doppler shift signal at least twice. Doppler signal detecting means for detecting a Doppler shift signal, phase angle interpolating means for interpolating the phase angle of the complex Doppler signal during the idle period of the Doppler transmission / reception using the Doppler signals before and after the idle period, and the same Doppler signal. An ultrasonic Doppler blood flow meter provided with an absolute value interpolating means for interpolating an absolute value of a complex Doppler signal during a transmission / reception pause period using Doppler signals before and after the pause period.

Effect The present invention has the above-described configuration to transmit and receive Doppler pulses two or more times in succession, suspend Doppler pulse transmission and reception for one Doppler sample period or more, and convert Doppler data during the Doppler pulse pause period to actual Doppler data before and after the pause period. The above object is achieved by accurately performing interpolation calculation from the phase angle and the absolute value of, and generating a Doppler data sequence that is almost equivalent to the original Doppler data sequence sampled at equal time intervals.

Examples Examples of the present invention will be shown below.

FIG. 1 is a block diagram of the embodiment. In FIG. 1, a solid line shows a signal flow, and a dotted line shows a control flow. The probe 101 receives the transmission pulse from the transmission scanning circuit 102, transmits an ultrasonic pulse to the subject, converts the scattered ultrasound from the subject into an electric signal, and sends it to the reception scanning circuit 103. Transmission scanning circuit 102, reception scanning circuit 103
Performs B-mode scanning and Doppler scanning in time division according to an instruction from the control unit 104. The switch 105 is instructed by the control unit 104 to send the ultrasonic echo signal from the reception scanning circuit 103 to the detection unit 106 during tomographic image scanning and to the mixer 10 during Doppler scanning.
Send to 7,108. The mixer 107 mixes the ultrasonic echo signal from the switch 105 and the signal from the oscillator 109,
The mixer 108 is a Doppler signal detecting means for mixing the ultrasonic echo signal from the switch 105 and the signal obtained by phase-shifting the signal from the oscillator 109 by the 90 ° phase shifter 110. The sample hold circuits 111 and 112 receive a gate signal corresponding to the Doppler inspection region from the control unit 104 and sample the Doppler signals from the mixers 107 and 108. The interpolation unit 113 interpolates Doppler data from the Doppler signals from the sample and hold circuits 111 and 112 during the Doppler transmission / reception pause period instructed by the control unit 104, and inserts it into the Doppler signal during the Doppler transmission / reception period so that the time intervals are equal. Generate a Doppler signal data string,
It is sent to the frequency analysis unit 114. The frequency analysis unit 114 performs Fourier analysis, etc., and displays the result as a Doppler image signal.
Send to 115. The display unit 115 simultaneously displays the tomographic image signal from the detection unit 106 and the Doppler image signal from the frequency analysis unit 114 under the control signal from the control unit 104.

The operation of each unit will be described in detail together with the operation timing.

FIG. 2 shows the operation timing of the embodiment of claim 2 in which Doppler scanning is repeated twice and B-mode scanning is repeated twice. (A) is a transmission pulse in the transmission scanning circuit 102, (A) is the state of the switch 105, and D is the mixer 107/108.
B indicates that the input is connected to the detection unit 106. (C) is the output of the detection unit 106, (D) is a Doppler gate signal from the control unit 104 that controls the sample and hold circuits 111 and 112, and (E) is a vector in which the outputs of the sample and hold circuits 111 and 112 are real and imaginary parts. In the figure, (F) shows the output of the interpolation unit 113 in a vector diagram.

The transmission scanning circuit 102 transmits the Doppler pulse D or B mode pulse B to the probe 101 at the timing indicated by the transmission pulse (A). The switch 105 sends the output of the reception scanning circuit 103 to the mixers 107 and 108 during the periods P ₁ and P ₃ (Doppler scanning period) and the detection unit 106 during the period P ₂ (B mode scanning period) as shown in (a). Send to. B mode scanning period P ₂
In step (c), information on two scanning lines forming the B-mode tomographic image is sampled, and the detection unit 106 performs envelope detection. During the Doppler scanning periods P ₁ and P ₃ , the quadrature detection outputs from the mixers 107 and 108 are output by the sample and hold circuits 111 and 112 according to the Doppler gate signal (d).
As shown in, sampling is performed at Doppler sampling times t ₁ , t ₂ , t ₅ , and t ₆ . The interpolator 113, as shown in (f), shows the Doppler signal at the Doppler sampling times t ₃ and t ₄ when the B-mode scanning period P ₂ is the Doppler scanning period.
_{3, 4} and _{t 1, t 2, t 5} , to interpolate based on the Doppler data at t _6.

FIG. 3 shows a first configuration example of the interpolation unit 113. The A / D 31 converts the analog signal from the sample hold into a digital signal. The r-θ converter 32 converts the orthogonal data from the A / D 31 into polar coordinate components. The Doppler data converted into the polar coordinate component is the absolute value interpolation calculation unit 33, the phase angle interpolation calculation unit
The signal is sent to 34, and Doppler data interpolation is performed during the B mode scanning period. The result is sent to the synthesizing unit 35, and the directly measured Doppler signal and the interpolation data are output in the correct time order.

An example of the interpolation calculation will be described. As in the timing shown in FIG. 2, it is assumed that the Doppler sample has two cycles and the B-mode scanning period has two cycles.

Time t _i sent from the sample hold circuits 111 and 112
The Doppler data (complex vector) at (i = 1,2,5,6) is z _i = a _i + jb _i . z _i is A / D is quantized by the transducer 31 r-theta conversion unit 32 by z _i = r _i ejθ _i become polar component (absolute value r _i, the phase angle _{θ i, -π <θ i ≦} π) When converted, the missing Doppler data ₃ = r at times t ₃ and t ₄
The interpolation calculation of ₃ ejθ ₃ , ₄ = r ₄ ejθ ₄ is performed as follows.

Interpolation calculation of the absolute value interpolation operation unit 33: the absolute value, the period from time t ₂ to time t ₅ by linear _{interpolation, r 3 = (2r 2 +} r 5) / 3 (1) r 4 = (r ₂ + 2r ₅ ) / 3 (2)

Calculation of Phase Angle Interpolation Calculation Unit 34: Consider also linear interpolation in the phase angle from time t ₂ to time t ₅ . However, since there is a time difference that is three times the sampling period between time t ₂ and time t ₅ , the phase angle may change by π or more, and the true phase angle difference θd between time t ₂ and time t ₅ may change. Is θd = (θ ₅ −θ ₂ ) + 2πn (3) where n is multiplied by an integer. On the other hand, the average ω of the phase difference between time t ₁ and t ₂ and the phase difference between time t ₅ and t ₆ is ω = {(θ ₂ −θ ₁ ) + (θ ₆ −θ ₅ )} / 2 (4) Therefore, if we consider the phase difference ω between time t ₂ and t _3, between time t ₃ and t _{4, and} between time t ₄ and t ₅ , then θd = ω · 3 (5) Since it should be, from equations (3) and (5), 3ω = (θ ₅ −θ ₂ ) + 2πn (6) n = {3ω − (− θ ₂ )} / 2π (7), where n is an integer Therefore, n = ROUND {[3ω- (θ ₅ −θ ₂ )] / 2π} (8) However, ROUND (x) is expressed as a value obtained by rounding x. By substituting the calculated n, θd can be obtained. From this θd, θ ₃ = θ ₂ + θd / 3 (9) θ ₄ = θ ₂ + 2θd / 3 (10) is calculated. Note that the interpolation calculation method is not limited to the example given here, and there are various methods for calculating the absolute value, for example, the absolute value of the last measured Doppler data is directly used as the interpolation value.

A second configuration example of the interpolation unit 113 is shown in FIG. This is an absolute value interpolation calculation unit 33, a phase angle interpolation calculation unit 34, and a synthesis unit.
The orthogonal converter 41 is inserted between the frequency converter 35 and
This is the same as the first configuration example of the interpolation unit 113 in FIG. 3 except that the orthogonal coordinate component of Doppler data is sent to 114.

Further, FIG. 5 shows a third configuration example of the interpolation unit 113. This is obtained by adding a low-pass filter 51 to the first configuration example of the interpolation unit 113 in FIG. 3, and by doing so, the clutter component can be removed.

A fourth configuration example of the interpolation unit 113 is shown in FIG. This is a digital filter (low-pass filter 61) used as the low-pass filter for the clutter component in the third configuration example of the interpolation unit 113 in FIG.

Thus, according to the ultrasonic blood flow meter of the first embodiment, B /
Since the missing Doppler data in the B mode scanning period is correctly interpolated in the D mode, it has a blood flow velocity detection ability equal to the maximum blood flow velocity detection ability in the Doppler mode alone, and the Doppler scanning time and the B mode scanning time are By setting the ratio to 1: 1, it is possible to reduce the decrease in the frame rate of the B-mode tomographic image and provide a real-time B-mode image.

Next, the operation timing in the second embodiment of the present invention will be described with reference to FIG. The device configuration in the second embodiment can be realized by the same configuration as that described in the first embodiment.

The transmission scanning circuit 102 transmits the Doppler pulse D twice and the B mode pulse B once during the two Doppler pulse repetition periods at the timing indicated by the transmission pulse (X). The switch 105 outputs the output of the receiving circuit 103 during the period P _{1 as} shown in (h).
・ In P ₃ (Doppler scanning period), send mixers 107 and 108,
In period P ₂ (B mode scanning period), the signal is sent to the detection unit 106. In the B-mode scanning period P ₂ , information on one scanning line forming the B-mode tomographic image shown in (X) is collected, and the envelope detection is performed in the detection unit 106. The scanning line information in this case has double the depth information as compared with that in the first embodiment. In Doppler scan period P ₁ · P _3, a mixer
The quadrature detection output from 107/108 is sampled and held by the sample hold circuits 111/112 according to the Doppler gate signal (U).
Doppler sampling time t ₁ , t ₂ , t ₃ , t ₅ ,
Sampling is performed at t ₆ . The interpolator 113, as shown in (4), shows the Doppler signal at the Doppler sampling times t ₃ and t ₄ when the B-mode scanning period P ₂ is the Doppler scanning period.
₃ and ₄ are interpolated based on the Doppler data at t ₁ , t ₂ , t ₅ and t ₆ .

Thus, according to the ultrasonic blood flow meter of the second embodiment, B /
In the D mode, it has a blood flow velocity detection ability equal to the maximum blood flow velocity detection ability in the Doppler mode alone, and the inspection depth of the B mode tomographic image can be doubled. Further, since the time from the transmission of the B-mode pulse to the transmission of the next Doppler pulse becomes long, the residual echo of the B-mode pulse affecting the Doppler signal becomes small, so that the Doppler signal has a good S / N ratio.

Further, as the operation timing in the third embodiment of the present invention in FIG. 8 shows, the interpolation unit 113 does not use the Doppler data z ₄ immediately after the Doppler scan suspension period P ₂ for interpolation, and also generates z ₄ by interpolation. The configuration of substituting the generated data can reduce the influence of the transient response of the device.

EFFECTS OF THE INVENTION As is clear from the above examples, according to the present invention, B /
In D mode, the missing Doppler data in the B mode scanning period is correctly interpolated by the Do phase angle and the absolute value. Therefore, the ultrasonic Doppler having the blood flow velocity detection ability equal to the maximum blood flow velocity detection ability in the Doppler mode alone. A blood flow meter can be provided.

Further, even when the doppler scan pause period is a long period of two Doppler sample periods or more, the missing Doppler data during that period can be correctly interpolated. Therefore, it is restricted by effectively using the long-term Doppler scan pause period. It can be an ultrasonic Doppler blood flow meter that provides a low B / D mode.

[Brief description of drawings]

1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a timing diagram showing the operation of each block of FIG. 1 in the first embodiment of the present invention, and FIG. 3 is a first diagram of an interpolating means. FIG. 4 is a block diagram showing a configuration example, FIG. 4 is a block diagram showing a second configuration example of the interpolation means, FIG. 5 is a block diagram showing a third configuration example of the interpolation means, and FIG. FIG. 7 is a block diagram showing an example of the configuration of FIG. 7, FIG. 7 is a timing diagram showing the operation of each block of FIG. 1 in the second embodiment of the present invention, and FIG. 8 is a first diagram in the third embodiment of the present invention. FIG. 9 is a timing chart showing the operation of each block, FIG. 9 is a diagram showing the configuration of a conventional device, and FIG. 10 is a diagram explaining an interpolation method of a conventional example. 101 ... probe, 102 ... transmission scanning circuit, 103 ... reception scanning circuit, 104 ... control unit, 105 ... switch, 106 ...
Detection unit, 107,108 …… Mixer, 109 …… Transmitter, 110 …… 9
0 ° phase shifter, 111,112 …… Sample hold circuit, 11
3 ... Interpolation unit, 114 ... Frequency analysis unit, 115 ... Display unit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Yunao Nakanaka, 4-3-1, Tsunashima-higashi, Kohoku-ku, Yokohama-shi, Kanagawa Matsushita Communication Industrial Co., Ltd. (56) Reference JP-A-61-25534 A)

Claims (2)

[Claims] 1. A moving speed of a scatterer in the subject based on scattered ultrasonic waves from the ultrasonic transmission / reception by the transmission / reception while transmitting and receiving an ultrasonic pulse in the subject to obtain tomographic information in the subject. An ultrasonic Doppler blood flow meter main body for obtaining information, a control unit for suspending Doppler transmission / reception for a certain period after performing ultrasonic Doppler transmission / reception for obtaining a Doppler shift signal, and detecting the Doppler shift signal Doppler signal detecting means, phase angle interpolating means for interpolating the phase angle of the complex Doppler signal during the doppler transmission / reception pause period using Doppler signals before and after the pause period, and similarly during the doppler transmission / reception pause period An ultrasonic Doppler blood flow meter, comprising: an absolute value interpolating means for interpolating the absolute value of the Doppler signal using the Doppler signals before and after the rest period. 2. The Doppler transmission / reception suspension period of the control means is 2
The ultrasonic Doppler blood flow meter according to claim 1, which has a Doppler sample period or more.