JPH02206446A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

PURPOSE:To obtain an ultrasonic image of high image quality by reducing speckles by mounting a control means changing over each transmission signal of a transmission circuit and each band filter of the receiving circuit corresponding to each transmission signal in connection with each other at every ultrasonic raster. CONSTITUTION:A receiving circuit 3 provided with a plurality of different BPFs 31, 32 inputting the receiving signals s3, s4 reflected from a living body through a switch 33 and filtering the said signals at center frequencies f3, f4 to output the same through a switch 34 and a controller 4 changing over switches 23, 33, 34 in connection with each other at every ultrasonic rasters so as to select the respective BPFs 31, 32 of the receiving circuit 3 corresponding to the respective transmission signals s1, s2 of a transmitting-receiving circuit 2 are provided. The respective transmission frequencies f1, f2 in the respective transmission signals s1, s2 are changed at every ultrasonic rasters and said signals are received at the center frequencies f3, f4 of the BPFs 31, 32 corresponding thereto. That is, since frequencies are different between the respective ultrasonic rasters, the interferences between the ultrasonic rasters are different and correlation is eliminated. As a result, the correlation of the speckle patterns between the ultrasonic rasters is eliminated and speckles can be reduced and, by this method, an ultrasonic image of high image quality can be obtained.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention transmits ultrasonic waves from an ultrasonic probe to a subject and collects signals reflected from the subject. The present invention relates to an ultrasonic diagnostic apparatus that detects a received signal and displays a B-mode image of the subject.

(Prior art) Ultrasonic diagnostic methods use anatomical information, typically represented by B-mode images, movement information of in-vivo organs, typically represented by M-mode images, and the Doppler effect, typically represented by blood flow imaging. The functional information associated with the movement of moving objects within the living body is used for diagnosis.

Further, a typical example of a method of scanning an inside of a living body using ultrasound waves is electronic scanning and mechanical scanning. Here, the electronic scanning method will be explained.

In other words, in the case of linear electronic scanning using an array-type ultrasonic probe (probe) equipped with multiple ultrasonic transducers, one unit is a number of ultrasonic transducers, and one unit of ultrasonic This is a method of transmitting an ultrasonic beam by exciting a sonic oscillator. For example, by sequentially shifting the pitch by one oscillator and excitation so that the position of each unit of element changes one after another. This is a method of electronically shifting the transmission point position of the ultrasound beam.

Then, so that the ultrasound beam is focused as a beam, the excited ultrasound transducers are shifted in excitation timing between those located in the center of the beam and those located on the sides, and the ultrasonic transducers generated thereby The reflected ultrasound waves are focused (electronically focused) using the phase difference between the sound waves generated by the vibrator.

The reflected ultrasound is then received by the same vibrator that was excited and converted into an electrical signal, and the echo information from each transmitted and received wave is formed, for example, as a tomographic image, and the image is displayed on a cathode ray tube or the like.

In addition, in the case of sector scanning, the excitation timing of each transducer is set so that the transmission direction of the ultrasonic beam sequentially changes in a fan shape for each pulse of the ultrasonic beam for one unit of excited ultrasonic transducers. It is changed in accordance with a desired direction, and the subsequent processing is basically the same as the linear electronic scanning described above.

In addition to the above-mentioned linear and sector electronic scanning, there is also mechanical scanning in which a transducer (probe) is attached to a scanning mechanism and ultrasonic scanning is performed by moving the scanning mechanism.

On the other hand, in the imaging method, in addition to a B-mode image in which signals based on ultrasonic transmission and reception are combined to form a tomographic image, an M-mode image based on fixed scanning in the same direction is typical.

This represents the temporal change in the ultrasonic wave transmitting/receiving site, and is particularly suitable for diagnosing moving organs such as the heart.

Further, the ultrasonic Doppler method, of which blood flow imaging is a typical example, is a method of obtaining functional information accompanying the movement of a moving object within a living body and visualizing it, and this will be explained below. That is, the ultrasonic Doppler method utilizes the ultrasonic Doppler effect in which when an ultrasonic wave is reflected by a moving object, the frequency of the reflected wave shifts in proportion to the moving speed of the object.

Specifically, if an ultrasonic rate pulse (or continuous wave) is transmitted into a living body and the frequency shift due to the Doppler effect is obtained from the phase change of the reflected wave echo, the Motion information of moving objects can be obtained. According to this, it is possible to know the state of blood flow such as the direction of blood flow at a certain position in the living body, the state of the flow (disturbed or regular), the flow pattern, the velocity value, etc.

Next, the device will be explained. That is, in order to obtain blood flow information from ultrasonic echoes, ultrasonic pulses are repeatedly transmitted a predetermined number of times in a certain predetermined direction, and phase information is extracted by phase-detecting the received echoes. This signal is digitized and passed through a digital filter to remove non-moving or slow-moving components, or clutter components. The signal that has passed through the filter is then subjected to frequency analysis.

The frequency analyzed by this is the Doppler shift frequency caused by the movement of the moving object, and is superimposed on the lj-only or B-mode image or M-mode image as two-dimensional blood flow information indicating the direction and velocity of blood flow. to be displayed.

(Problems to be Solved by the Invention) Incidentally, a mottled pattern called "speckle" appears in the B-mode image of the above-mentioned ultrasonic diagnostic apparatus. As shown in FIG.
, B are incident on a minute scatterer Q, each reflected wave from this minute scatterer Q interferes with each other and is generated, and the generation of speckles is due to the coherent nature of the ultrasonic waves. . In other words, since the ultrasonic pulses that enter the living body are coherent, that is, the phases are aligned, the reflected waves from the many scatterers that exist inside the living body cause interference on the receiving surface of the ultrasound probe 1. Resulting in. Therefore, the amplitude of the received signal fluctuates, and this fluctuation causes a mottled pattern, ie, speckle, on the B-mode image described above. This speckle is caused by interference,
There was a problem in that it did not display the tissue structure inside the living body, and the image quality deteriorated.

Therefore, as one of the improvement methods, it has already been proposed in J. Med Ultrasonic, Vol. 13 N.
Ultrasonic tomographic image (
There is a real-time method for reducing speckle noise in B-mode images. In this method, the received signal detected for each image is passed through multiple filters to perform a spatial compound scan, and then an equalized frequency compound scan is performed by detecting the envelope and adding it. This reduces speckle noise in real time. Here, in order to reduce speckle noise, it is sufficient to superimpose multiple images with small correlations, but a method of obtaining images with small correlations by changing the position of the ultrasound probe 1 is the spatial compound scan described above. It is. According to this, incoherent addition in the distance direction is performed, speckle noise is significantly reduced, and a high-quality B-mode image is obtained.

However, the spatial resolution of the above method is limited.

In particular, there was a problem in that the resolution in the depth direction deteriorated.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an ultrasonic diagnostic apparatus that can reduce speckles and obtain high-quality ultrasonic images.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems and achieve the objects, the present invention takes the following measures. That is, the present invention transmits ultrasonic waves from an ultrasound probe to a subject, receives a signal reflected from the subject, detects this received signal, and detects the B of the subject.
In an ultrasound diagnostic apparatus that displays a mode image, a transmission circuit generates a plurality of transmission signals corresponding to different transmission frequencies and outputs each transmission signal to the ultrasound probe for each ultrasound raster, and this transmission circuit a receiving circuit provided with a plurality of different bandpass filters that filter each received signal reflected from the subject by a corresponding frequency band when each transmission signal is transmitted to the subject for each ultrasonic raster; The apparatus includes a control means for switching each transmission signal of the transmission circuit and each bandpass filter of the reception circuit corresponding to each transmission signal in conjunction with each ultrasonic raster.

(Effects) By taking such measures, the following effects are achieved. Each transmission frequency in each transmission signal is changed for each ultrasonic raster, and each transmission signal is received by each band filter corresponding to each transmission frequency. That is, since the frequencies are different between the ultrasonic rasters, the interference between the ultrasonic rasters is different, so there is no correlation between the ultrasonic rasters. As a result, the correlation between speckle patterns between ultrasound rasters is eliminated, and speckles can be reduced, thereby making it possible to obtain a high-quality ultrasound image.

(Embodiment) FIG. 1 is a schematic block diagram showing an embodiment of the ultrasonic diagnostic apparatus according to the present invention, and FIG. 2 shows each BPF (
FIG. 3 is a diagram showing a state in which ultrasonic beams A and B are transmitted from the ultrasound probe 1 using transmission signals having different transmission frequencies.

The feature of this embodiment is that different transmission frequencies fl
, f2.

A transmitting circuit 2 which outputs the transmitting signals 81,82 to the ultrasonic probe 1 via the switch 23 for each ultrasonic raster; When each transmission signal sl, s2 is transmitted to a living body for each ultrasonic raster, each reception signal s3 . s
4 manually through the switch 33, and the corresponding frequency band, that is, the center frequency fif3. A plurality of different B P filtered by f4 and outputted via switch 34
F31.32 A receiving circuit 3 provided with a (bandwidth filter), each transmitting signal sl, s2 of the transmitting circuit 2, and each BP of the receiving circuit 3 corresponding to each transmitting signal Sl, 92.
A controller 4 is provided as a control means for switching the switches 23, 33, 34 in conjunction with each other for each ultrasonic raster so as to select F3[, 32.

The present device also includes a B-mode detection section 5. which performs envelope detection of the received signal from the reception circuit 3. D converting the detection signal from the B-mode detection unit 5 from an ultrasonic scan to a TV scan
It is provided with a TV display section 7 that inputs TV signals from the SC 6 and the DSC 6 and displays a B-mode image.

The operation of the embodiment configured as described above will be explained with reference to the drawings. First, in a certain ultrasonic raster, that is, ultrasonic beam A, when a control signal cl is input from the controller 4 to the transmitting circuit 2 and the receiving circuit 3, the switch 2
3.33.34 are interlocked with contacts at, a2. Switched to a3. Then, a transmission signal sl having a transmission frequency fl (for example, 3.5 MHz) is sent from the generator 21 in the transmission circuit 2 to the probe 1 via the switch 23, and the ultrasound beam A is transmitted into the living body. Ru. The received signal s3 reflected from the living body is received by the probe l, and further inputted to the BPF 31 via the switch 33. That is, in this BPF 3L, as shown in FIG.
The received signal s3 has a frequency close to this center frequency. Therefore, the received signal s3 is
31 and input to the B mode detection unit 5 via the switch 34.

Next, in the ultrasonic raster, that is, the ultrasonic beam B,
Since the control signal c2 from the controller 4 is input to the transmitting circuit 2 and the receiving circuit 3, the switches 23, 33, 34 operate in conjunction with the contacts bl, b2 . Switched to b3. Then, the transmitting frequency f2 is transmitted from the generator 22 in the transmitting circuit 2.
A transmission signal s2 having a frequency of 2.5 MHz (for example, 2.5 MHz) is sent to the probe l via the switch 23, and an ultrasound beam B is sent into the living body. The received signal s4 reflected from the living body is received by the probe l, and further inputted to the B P F 32 via the switch 33. In other words, this B
At P F 32, the transmission signal s2 is transmitted as shown in FIG.
The received signal s4 has a frequency close to this center frequency. Therefore, the received signal s4 is
32 and input to the B-mode image detection section 5 via a switch 34.

Furthermore, in the ultrasonic raster (not shown), switches 23, 33, and 34 are switched for each ultrasonic raster, and transmission signals sl having different transmission frequencies fl and f2 are transmitted.

Received signal s3.s2 that differs depending on s2. s4 and different band frequencies f3. The received signal is filtered by f4 and input to the B mode detection section 5. Envelope detection is then performed by the B-mode detection section 5, and the detection signal is written into a frame memory (not shown) by the DSC[i, converted to TV scan, and displayed on the TV display section 7 as a B-mode image.

As described above, according to this embodiment, each transmission frequency fl, f2 in each transmission signal 51.82 is changed for each ultrasonic raster, and each BPF 31 corresponding to each transmission frequency fl, f2 is changed.
．． 32 center frequencies f3°f4. That is, since the frequencies are different between the ultrasonic rasters, the interference between the ultrasonic rasters is different, so there is no correlation between the ultrasonic rasters. As a result, the correlation between speckle patterns between ultrasound rasters is eliminated, and speckles can be reduced, thereby making it possible to obtain a high-quality ultrasound image.

Note that the present invention is not limited to the embodiments described above, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] According to the present invention, there is provided a transmission circuit that generates a plurality of transmission signals corresponding to different transmission frequencies and outputs each transmission signal to the ultrasound probe for each ultrasound raster, and this transmission circuit. a receiving circuit provided with a plurality of different bandpass filters that filter each received signal reflected from the subject by a corresponding frequency band when each transmission signal is transmitted to the subject for each ultrasonic raster; a control means for switching each transmission signal of the transmission circuit and each bandpass filter of the reception circuit corresponding to each transmission signal in conjunction with each ultrasonic raster;
, the transmission frequency of each transmission signal is changed for each ultrasonic raster, and each transmission frequency is received by each bandpass filter corresponding to each transmission frequency.

That is, since the frequencies are different between the ultrasonic rasters, the interference between the ultrasonic rasters is different, so there is no correlation between the ultrasonic rasters. As a result, the correlation between speckle patterns between ultrasound rasters is eliminated, and speckles can be reduced.
Thereby, it is possible to provide an ultrasonic diagnostic apparatus that obtains high-quality ultrasonic images.

[Brief explanation of the drawing]

Fig. 1 is a schematic block diagram showing an embodiment of the ultrasonic diagnostic apparatus according to the present invention, Fig. 2 is a diagram showing the band characteristics of each BPF (band pass filter) in the receiving circuit, and Fig. 3 is a diagram showing the band characteristics of each BPF (band pass filter) in the receiving circuit. FIG. 4 is a diagram showing a state in which each ultrasonic beam A and B is transmitted from an ultrasound probe using a transmission signal having a frequency, and FIG. 4 is a diagram showing a state in which each ultrasonic raster generates speckles due to a scatterer. be. l... Ultrasonic probe, 2... Transmission circuit, 3... Receiving circuit, 4... Controller, 5... B mode detection section, 6... DSC17... TV display section, 21.22・
... Generator, 31, 32... B P F, 23.3
3.34...Switch. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] Ultrasonic diagnosis that transmits ultrasonic waves from an ultrasound probe to a subject, receives signals reflected from the subject, detects the received signals, and displays a B-mode image of the subject. The device includes a transmission circuit that generates a plurality of transmission signals corresponding to different transmission frequencies and outputs each transmission signal to the ultrasound probe for each ultrasound raster, and a transmission circuit that generates each transmission signal for each ultrasound raster from this transmission circuit. a receiving circuit provided with a plurality of different bandpass filters that filter each received signal reflected from the subject when a signal is transmitted to the subject in a corresponding frequency band; An ultrasonic diagnostic apparatus comprising: control means for switching each bandpass filter of the receiving circuit corresponding to each transmitted signal in conjunction with each ultrasonic raster.