JP2760550B2 - Ultrasound diagnostic equipment - Google Patents

Description

The present invention relates to an ultrasonic diagnostic apparatus for obtaining a tomographic image of a living body using ultrasonic waves, and particularly relates to an ultrasonic tomographic method and a Doppler method. The present invention relates to an ultrasonic diagnostic apparatus that is implemented almost simultaneously.

(Prior art) An ultrasonic diagnostic method that radiates an ultrasonic pulse into a living body and obtains biological information from reflected waves from each tissue has no irradiation obstacle such as X-rays, and furthermore, diagnoses soft tissue without a contrast agent. And real-time images can be easily obtained. In ultrasonic diagnostic methods, there are known a B-mode method (so-called ultrasonic tomography method) for imaging reflection intensity in a living body and a Doppler method for measuring the velocity and direction of blood flow using the Doppler effect. In the latter case, a two-dimensional blood flow velocity display method (blood flow imaging method) has recently been developed in addition to the one-point Doppler method which has been widely used in the past, and this method has been widely used in clinical settings together with the B-mode method. Used.

In the diagnosis by the blood flow imaging method, first, an observation section of the heart or blood vessel is positioned by a B-mode image, and then a Doppler signal obtained by scanning the same section is detected to measure the direction and velocity of the blood flow. That is, it is desirable that the B-mode image and the blood flow imaging are obtained almost at the same time, and for that purpose, measurement is performed using the same ultrasonic probe and the same transmission / reception circuit.

When displaying a tomographic image, it is necessary to narrow the beam width in order to increase the resolution of the image. However, if the beam width is reduced according to this requirement, side lobes are generated, and therefore, in blood flow imaging, it is important to reduce artifacts on the blood vessel wall and heart wall caused by the side lobes. This is because the intensity of the reflected wave from the blood cell from which the Doppler signal is obtained is extremely weak, and it becomes difficult to obtain the Doppler signal when the artifact is mixed with the reflected signal from the blood cell.

As described above, although the optimum beam shapes used for the B-mode method and the blood flow imaging method are different, the optimization of the beam shape in each display mode has not been conventionally performed.

(Problems to be Solved by the Invention) In the conventional ultrasonic diagnostic apparatus, although the optimum conditions of the ultrasonic beam shape in the B-mode method and the blood flow imaging method are different, each scan is performed with the same beam shape. Therefore, the image quality was degraded in either the B-mode image or the blood flow image.

The present invention has been made in view of the above-described problems, and has as its object to provide an ultrasonic beam shape under optimum conditions corresponding to each of the B-mode method and the blood flow imaging method. Is to provide an ultrasonic diagnostic apparatus that is selected and used.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an array type ultrasonic transducer for transmitting and receiving ultrasonic waves, a transmission circuit for driving the transducer, A receiving circuit for adding a predetermined delay time to the received signal from the vibrator and adding the detected signal, a detecting means for detecting the amplitude and a Doppler signal of the signal from the receiving circuit, and a tomographic image and a tomographic image based on a detection result of the detecting means. An ultrasonic diagnostic apparatus comprising a display means for displaying blood flow information, comprising a transmission signal amplitude control circuit for changing a gain of the transmission circuit, and obtaining ultrasonic transmission and the blood flow information to obtain the tomographic image. In this case, the transmission directivity characteristics are different in ultrasonic transmission for the purpose.

(Operation) With this configuration, in the transmission circuit,
The configuration is such that the gain of the transmission circuit is controlled so that an optimal ultrasonic beam shape is obtained for each of obtaining a tomographic image and obtaining blood flow information. In the case of obtaining the same, the optimum conditions are provided despite the use of the same ultrasonic probe and transmission / reception circuit, and a high-resolution tomographic image can be obtained, and the blood flow signal can be obtained with high sensitivity. Can be measured.

(Embodiment) When an ultrasonic pulse is radiated into a living body, it is desirable to radiate an ultrasonic wave having a narrow beam width only in a predetermined direction. A weak ultrasonic beam called a so-called radiated ultrasonic beam is emitted, and these side lobes lower the S / N of a tomographic image or generate an artifact, which is a major cause of deteriorating image quality.

A weighting method is well known as one of the methods for suppressing the side lobe. First, the weighting method will be described with reference to FIG. As shown by the characteristic curve (a) in the figure, when the sound source is approximated by a flat plate (a one-dimensional model is used in this case) and the transmission and reception sensitivities of the respective parts are uniform, this transducer is used. As for the transmission (reception) directivity characteristics at a sufficiently distant position, about 20% of side lobes exist around the main lobe as shown by the characteristic curve (a) shown by the solid line in FIG. On the other hand, if the transmission (reception) sensitivity at the center is higher than that at the end as shown by the characteristic curve (b) in FIG.
As shown in the characteristic curve (b) in the figure, the main lobe is slightly widened, but the side lobe can be reduced. Therefore, by electronically controlling the degree of the weighting, that is, the magnitude of the transmission (reception) sensitivity, the shape of the ultrasonic beam can be changed at a high speed. In the most widely used electronic scanning apparatus today, an array type transducer is used as an ultrasonic transducer (hereinafter referred to as an ultrasonic transducer). In this device, the width of the ultrasonic beam and the size of the side lobe can be controlled by controlling and weighting the delay time of each drive signal or received signal of the ultrasonic transducer.

A description will be given of a sector electronic scanning ultrasonic diagnostic apparatus according to an embodiment of the present invention with reference to FIG. In the figure, a pulse generator 1 for outputting a reference repetition pulse for emitting an ultrasonic pulse into a living body is connected to a plurality of transmission delay circuits 2-1 to 2-N, respectively. Each of these transmission delay circuits has a predetermined delay time determined by the radiation direction and the convergence point of the transmission ultrasonic wave. The transmission delay circuits 2-1 to 2-N are connected to a plurality of variable gain oscillator drive circuits 3-1 to 3-N, respectively. An amplitude control signal from the transmission signal amplitude control circuit 4 is applied to each gate circuit of these oscillator driving circuits, and the gain of the circuit is controlled according to the control signals. Oscillator drive circuit 3
-1 to 3-N represent a plurality of array type ultrasonic transducers 5 respectively.
-1 to 5-N.

A plurality of variable gain preamplifiers 6-1 to 6-N are connected to these transducers 5-1 to 5-N. A gain control signal from the reception signal gain control circuit 7 is given to each gate of these preamplifiers, and the gain of the circuit is controlled according to the control signals. Preamplifier 6-1
6-N are connected to the plurality of reception delay circuits 8-1 to 8-N, respectively. Each of these delay circuits has a predetermined delay time determined by the reception direction and reception convergence point of the received ultrasonic wave. Reception delay circuits 8-1 to 8-
N outputs are all connected to the adder 9. The output of the adder 9 is connected to a tomographic image processing circuit 10 and a blood flow signal processing circuit 11, respectively. The tomographic image processing circuit 10 includes a logarithmic amplifier 12, an envelope detection circuit 13, and an A / D converter 14. on the other hand,
The blood flow signal processing circuit 11 is composed of a quadrature phase detection circuit for mixing (quadrature phase detection) between the output of the adder 9 and a reference signal having substantially the same frequency as the ultrasonic signal. That is, a phase detection circuit 15-1, 15-2, an analog filter (LPF) 16-1, 16-2, an A / D converter 17-1, 17-2, a digital filter (BPF) 18-1, 18 -2 are provided as a pair. The outputs of the digital filters 18-1 and 18-2 are supplied to a computing unit 19, where they are subjected to, for example, frequency analysis and then the center or spread (dispersion) of the spectrum.
Is calculated. In the figure, reference numeral 20 denotes a high-frequency power supply that outputs a reference signal having the same frequency as the ultrasonic signal, and reference numeral 21 denotes a phase shifter that shifts the output phase of the high-frequency power supply 20 by π / 2.

The output signal of the tomographic image processing circuit 10, that is, the output signal of the A / D converter 14, is stored in the tomographic image memory area of the image memory 22,
The output signal of the blood flow signal processing circuit 11, that is, the output signal of the arithmetic unit 19 is stored in the blood flow signal memory area of the image memory 22.
A tomographic image is displayed on the TV monitor 23 based on the former signal stored in the image memory 22, and blood flow information based on the blood flow imaging method or the one-point Doppler method based on the latter signal.

Next, the operation of the above embodiment will be described. In FIG.
The repetition pulse output from the pulse generator 1 for determining the interval between the ultrasonic pulses emitted into the living body is determined by the transmission delay circuits 2-1 to 2-N from the radiation direction and the convergence point of the transmission ultrasonic wave. Is done. After a predetermined delay time is given, the pulse is sent to the transducer driving circuits 3-1 to 3-N, and the transmission signal amplitude control circuit 4 forms a driving pulse weighted and amplified to a predetermined magnitude. The N array ultrasonic transducers 5-1 to 5-N are driven by the driving pulse, and the ultrasonic waves are emitted into the living body.

On the other hand, the ultrasonic beam reflected from the inside of the living body is received by the array type ultrasonic transducers 5-1 to 5-N, and is converted into a control signal from the reception signal gain control circuit 7 in the preamplifiers 6-1 to 6-N. After being weighted and amplified to a predetermined size on the basis of the signal, the signal is sent to the reception delay circuits 8-1 to 8-N. Here, similarly to the transmission delay circuits 2-1 to 2-N, after a delay time determined by the reception direction and the reception convergence point is given, the adder 9 adds the reception signal from another oscillator to the reception signal. Is done. One of the output signals of the adder 9 is supplied to the tomographic processing circuit 10 and the other is supplied to the blood flow signal processing circuit.
The signal is sent to 11 and subjected to predetermined signal processing.

In the tomographic image processing circuit 10, logarithmic conversion of the signal amplitude and envelope detection of the received signal are performed in the logarithmic amplifier 12 and the envelope detection circuit 13, and A / D conversion is performed by the A / D converter 14. Is stored. On the other hand, in the blood flow signal processing circuit 11, the output of the adder 9 is mixed (quadrature phase detection) between the frequency of the ultrasonic signal and a reference signal having substantially the same frequency, and after the A / D conversion, the digital filter ( BPF) 1
By 8-1 and 18-2, signals (clutter signals) from the heart and blood vessels with extremely small Doppler frequency deviation are removed, and only minute signals from blood cells are separated and detected. The signal is subjected to, for example, frequency analysis in the arithmetic circuit 19, and then the center or spread (variance) of the spectrum is calculated, and the value is stored in the blood flow signal memory area in the image memory 22.

In this manner, the tomographic image signal and the blood flow signal obtained by electronically scanning the ultrasonic beam are temporarily stored in the image memory 22, and the tomographic image is based on the tomographic image signal, and the tomographic image is also based on the blood flow signal. Blood flow information based on a blood flow imaging method, a one-point Doppler method, or the like is displayed on the TV monitor 23. In such an electronic scanning device, side lobes in the directional characteristics in the scanning direction (transducer array direction) can be relatively easily reduced by appropriately weighting the transmission and reception signals of each transducer as described above. .

Next, regarding the optimization of the ultrasonic beam for each display mode, a combination of the B-mode scanning and the blood flow information scanning, particularly the blood flow image scanning, will be described with reference to FIG. The figure shows a time chart when a B-mode image and a blood flow image are obtained almost simultaneously. In general, a blood flow image is displayed simultaneously in a color image on a black-and-white image. In the case where one such image is formed, a predetermined location may be scanned only once for the B mode. As a scan for a blood flow image (D mode), the same place must be scanned back and forth at least ten times in order to calculate the blood flow velocity at the predetermined place. FIG. 2 shows a case where the ratio of the number of B-mode scans to the number of D-mode scans is 1: 4. That is, the pulse shown in (a) indicates the timing at which the ultrasonic wave is emitted into the body, and among these, p-1, p-6, p-11 ... Used for B-mode scanning, and as shown in (c), p-2 to p-5, p-7 to p-10,
are used for scanning for a blood flow image. In this case, in the scanning for the B mode, weighting for obtaining a beam shape suitable for the B mode (that is, weighting such that the main beam width is relatively narrow) is performed in the transmitting circuit, the receiving circuit, or both the transmitting circuit and the receiving circuit. The signal obtained at this time is sent to the tomographic image processing circuit 10 and temporarily stored in the image memory 22. On the other hand, at the time of scanning for a blood flow image, weighting for obtaining a beam shape suitable for this mode (that is, weighting for reducing the side lobe value) is performed in one or both of the transmission and reception circuits, and the blood flow signal processing circuit The image data is stored in the image memory 22 as a blood flow image signal via 11. Next, the image memory 22
Are displayed on the same CRT of the television monitor 23 as a B-mode signal and a blood flow image signal as a color image.

As described above, in the present invention, the signal obtained in the B-mode beam shape is used only for the B-mode display, and the signal obtained in the beam shape controlled for the blood flow image is used only for the blood flow image. Can be Therefore, as compared with the conventional method using the B-mode signal as a part of the blood flow image signal, the time required to obtain one image (B mode / blood flow image) becomes longer (that is, within a unit time). The number of displayed images is reduced, and the images tend to flicker.) However, as described above, the number of scans for the B mode is 1/10 or less as compared with the number of scans for the blood flow image.

Although the above embodiment has been described in connection with a case where a blood flow image is handled, the present invention is not limited to this, and can be applied to, for example, a one-point Doppler method widely used in the past. Further, the vibrator is not limited to the linear array type, and it is needless to say that the vibrator can be widely applied to a manual array type.

[Effects of the Invention] As described above, according to the present invention, in the transmission circuit, the gain of the transmission circuit is obtained so that the optimum ultrasonic beam shape can be obtained when obtaining a tomographic image and when obtaining blood flow information. Is configured to be controlled, so that a tomographic image,
In the case of obtaining any of the blood flow information, despite using the same ultrasonic probe and transmission / reception circuit,
As the optimum conditions are provided, a high-resolution tomographic image can be obtained, and a blood flow signal can be measured with high sensitivity.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention,
2 (a) to 2 (c) are time charts for explaining the operation of the embodiment, FIG. 3 is an explanatory diagram showing sensitivity characteristics of the ultrasonic transducer, and FIG. 4 is a directional characteristic of the ultrasonic beam. FIG. 1 pulse generator 2-1 to 2-N transmission delay circuit 3-1 to 3-N vibrator drive circuit 4 transmission signal amplitude control circuit 5-1 to 5- N: Array type vibrator, 6-1 to 6-N: Preamplifier, 7: Reception signal gain control circuit, 8-1 to 8-N: Reception delay circuit, 9: Adder, 10 ... ... Tomographic image processing circuit, 11 ... Blood flow signal processing circuit, 22 ... Image memory, 23 ... TV monitor

Claims (2)

(57) [Claims] An ultrasonic transducer for transmitting and receiving ultrasonic waves; a transmitting circuit for driving the vibrator; a receiving circuit for adding a predetermined delay time to a signal received from the vibrator; An ultrasonic diagnostic apparatus comprising: a detection unit that detects an amplitude of a signal from a reception circuit and a Doppler signal; and a display unit that displays a tomographic image and blood flow information based on a detection result of the detection unit. A transmission signal amplitude control circuit for changing a gain, wherein ultrasonic transmission for obtaining the tomographic image and ultrasonic transmission for obtaining the blood flow information have different transmission directivity characteristics. Ultrasound diagnostic device. 2. A transmission signal amplitude control circuit according to claim 2, wherein said transmission circuit amplitude control circuit reduces the side lobe value of the directional characteristic of the transmitted ultrasonic wave when obtaining said blood flow information as compared with the case where said tomographic image is obtained. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein the gain control is performed electronically.