JPH09187456A - Ultrasound diagnostic equipment - Google Patents

Abstract

(57) Abstract: An object of the present invention is to transmit an ultrasonic wave into a subject, receive an ultrasonic signal reflected and returned in the subject to obtain a received signal, and convert the received signal into the received signal. An ultrasonic diagnostic apparatus that displays an image based on the ultrasonic diagnostic apparatus prevents deterioration of resolution due to the thickness of a fat layer of the subject. An object of the present invention is to configure an object in an ultrasonic diagnostic apparatus having a plurality of transmission / reception channels and converging an ultrasonic beam by giving a predetermined delay to each channel when synthesizing ultrasonic signals of the respective channels. The delay amount calculated based on the sound velocity corresponding to the plurality of media is used. An operator is provided for changing the delay amount data according to the thickness of the medium of the fat layer of the subject. Also, the delay amount data is changed in association with the patient identification data. or,
Corresponding to the plurality of media, the sound velocity value of one medium is set to, for example, less than 1500 m / s, and the sound velocity value of the other medium is set to 1 above.
Over 500m / s.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention transmits an ultrasonic wave into a subject, receives the ultrasonic wave reflected and returned in the subject to obtain a reception signal, and an image based on the reception signal. The present invention relates to an ultrasonic diagnostic apparatus for displaying.

In ultrasonic diagnosis, it is important to be able to detect minute lesions in the human body, and for that purpose, images with good resolution must be obtained. The resolution is divided into a time resolution based on the ringdown time of the ultrasonic signal caused by the displacement characteristic of the transducer of the ultrasonic probe and a lateral resolution based on the ultrasonic beam width. As for the time resolution, the shorter the ringdown time, the higher the time resolution. Regarding the azimuth resolution, the shorter the ultrasonic beam width, the higher the azimuth resolution.

In order to narrow the width of the ultrasonic beam in a device that constitutes an ultrasonic beam by a plurality of transmission / reception channels, the phases of the ultrasonic signals of the transmission / reception channels must be accurately matched in the region of interest. is important. In particular, like the human body, when the sound velocity of ultrasonic waves varies depending on the medium (eg, fat layer and the like) forming the human body, the fat layer of each transmission / reception channel up to the region of interest is detected. It is necessary to selectively give a predetermined delay amount to each ultrasonic reception signal in accordance with the thickness to match the phases of the ultrasonic signals of the respective channels.

[0004]

2. Description of the Related Art FIG. 6 is a diagram for explaining a conventional ultrasonic diagnostic apparatus. As shown in FIG. 6, in an ultrasonic diagnostic apparatus that configures an ultrasonic beam by a plurality of transmission / reception channels, ultrasonic signals received by the piezoelectric element 1b of each transmission / reception channel 1a of the probe 1 are shown in the human body. Each transmit / receive channel 1a so that phasing addition is performed in the region of interest that is not
Is given an appropriate delay amount. This delay amount is determined by the speed of sound of the medium in which the ultrasonic wave is propagated.In the conventional ultrasonic diagnostic apparatus, the speed of sound in which the ultrasonic wave propagates inside the human body is about 1530 m / s as a uniform medium. The amount of delay was decided on the assumption.

In FIG. 6, the received signal from the probe 1 is received by the transmission / reception circuit 2, given the above-mentioned predetermined delay amount by the delay circuit 3, and subjected to phasing addition by the addition circuit 4,
After being detected by the detection circuit 5, the digital scan converter (DSC) 6 converts the reception signal on each scanning line from the probe 1 into a two-dimensional spatial luminance distribution, so-called M mode image, B mode. It is displayed as an image on the display device (CRT) 7.

[0006]

As described above, the sound velocity inside the living body is non-uniform, and in particular, the sound velocity value in the fat layer is 1476 m / s, which is the above-mentioned conventional assumed value (1530 m / s). s) and the liver is about 1570 m / s, which is faster than the previously assumed value. {The above-mentioned biological sound velocity data is excerpted from "Handbook of ultrasonic technology, published by Nikkan Kogyo Shimbun"}
It is considered to be close to (1500 m / s). Therefore, when the sound velocity is made uniform as in the conventional case, there is a problem that the ultrasonic beam is thickened without phased addition depending on the depth of the region of interest, resulting in deterioration of the lateral resolution.
Further, in general, in fat subjects, the fat layer is thick, in lean subjects, the fat layer is thin, and the thickness of the fat layer varies depending on the subject, and the degree of deterioration of the lateral resolution is also high. There was the problem of being different.

As a similar technique, there is "Ultrasonic Diagnostic Device" in Japanese Patent Laid-Open No. 4-158847. In summary, "Observation of reflected reception signal and detection of deviation of reception time of the reflected reception signal, To obtain accurate curve footing ", and a detection circuit for detecting the deviation of the reception time and a correction circuit for correcting the deviation detected by the detection circuit are required. It includes the problem that

As a technique developed from the above-mentioned JP-A-4-158847 "Ultrasonic diagnostic apparatus", there is JP-A-6-70928 "Delay time correction method for ultrasonic diagnostic apparatus and ultrasonic diagnostic apparatus". In principle, it is the same technique as the above-mentioned Japanese Patent Laid-Open No. 4-158847 "Ultrasonic Diagnostic Device", in summary,
"Observing the reflected reception signal, generating a map of the periodic component of the deviation of the reception time of the reflected reception signal, and based on this,
It is necessary to provide a detection circuit for detecting the deviation in the reception time and a correction circuit for correcting the deviation detected by the detection circuit.

In view of the above-mentioned conventional drawbacks, the present invention focuses on the fact that the sound velocity in a living body differs depending on the properties of the medium, sets the sound velocity corresponding to each medium in the living body, and based on the set sound velocity. It is an object of the present invention to provide an ultrasonic diagnostic apparatus capable of improving the azimuth resolution by calculating the delay amount and inserting the calculated delay amount for each transmission / reception channel.

[0010]

FIG. 1 is a diagram for explaining the principle of the present invention, and FIGS. 2-5 are diagrams showing an embodiment of the present invention. The above problems can be solved by the ultrasonic diagnostic apparatus configured as follows.

(1) An ultrasonic diagnostic system comprising a plurality of transmission / reception channels 1a, and when synthesizing ultrasonic signals of the transmission / reception channels 1a, an ultrasonic beam is converged by giving a predetermined delay amount to each transmission / reception channel 1a. The apparatus is configured to use a delay amount β calculated for each transmission / reception channel 1a based on the sound velocity corresponding to a plurality of media (for example, fat layer and liver) that constitute the subject.

(2) The ultrasonic diagnostic apparatus according to item (1) above, which is an operation for changing the delay amount β according to the thickness of a predetermined medium forming the subject. Configure to have 80 children.

(3) The ultrasonic diagnostic apparatus according to the above item (2), which corresponds to the input patient identification data section 81,
It is configured to include means for changing the delay amount β.

(4) The ultrasonic diagnostic apparatus according to item (1), (2), or (3) above, wherein a plurality of media (excluding the acoustic lens of the ultrasonic probe 1) (Fat layer and liver), the sound velocity value of a predetermined medium is less than Am / s, the sound velocity value of a medium other than the predetermined medium is Am / s or more, and the ultrasonic signals of the plurality of transmission / reception channels 1a are set. Is configured to calculate a delay amount β for synthesizing.

(5) The ultrasonic diagnostic apparatus according to the above item (1), further comprising a circuit 10 for detecting the reception wave time of the maximum amplitude of the ultrasonic transmission / reception signal, The sound velocity value is set to be less than B m / s, and the sound velocity value of the medium after the reception wave time is set to be B m / s or more.
It is configured to calculate the delay amount β for synthesizing the ultrasonic signals of.

(6) The ultrasonic diagnostic apparatus according to item (4) or (5), wherein the sound velocity value A or B is 1500 m / m2.
Configure to be s. (7) The ultrasonic diagnostic apparatus according to the item (5), wherein the electrical focal length of the ultrasonic beam is linked to the received wave time,
Alternatively, a means for changing at least one of the driving frequency of the ultrasonic piezoelectric element, the frequency filter characteristic of the ultrasonic reception signal, or the thickness opening of the ultrasonic probe is provided.

FIG. 1 is a diagram for explaining the principle of the present invention.
(a) shows the concept of the delay amount β due to the difference in sound velocity based on the type of medium inside the living body, corresponding to the delay amount α for focusing, corresponding to each transmission / reception channel of the probe 1. Fig. 1 (b) illustrates the convex probe.
An example of the delay amount β due to the difference in sound velocity based on the type of the medium inside the living body in the case of (radius of curvature 40 mm) is shown in FIG. 1 (c). The example of a principle structure of an apparatus is shown.

FIG. 1A shows, for example, a portion O having a depth of 50 mm.
In the case of focusing on, the ultrasonic signal from each transmitting / receiving channel of the probe 1 is shown in the transmitting / receiving direction corresponding to a certain scanning line A. In addition to the delay amount α required for focusing, From each transmit / receive channel 1a of the probe 1,
For example, the difference in the delay amount indicated by β occurs in the inside of the living body corresponding to the paths having different thicknesses of the fat layer.

FIG. 1B shows the above convex probe.
In the case of (curvature radius 40 mm), based on the type of the medium inside the living body, shows an example of the delay amount due to the different sound speed, the sound speed of the fat layer 1480 m / s, The difference in the delay amount at a depth of 50 mm between the case where the delay amount β is calculated and the case where the effect of the fat layer is not taken into consideration, assuming that the thickness is 20 mm and the sound velocity of the liver is 1570 m / s, is shown. It is a thing.

The farther the channel from the scanning center (scan line) A, the greater the difference. In the example shown in Fig. 1 (b), if the frequency of the ultrasonic wave used is 5 MHz, one cycle T = 1/5 MHz = 200 ns (corresponding to 360 degrees),
The channel corresponding to the right edge of the graph has a delay amount of 100 ns, which is 180 degrees from the center channel. This phase shift increases as the frequency of the ultrasonic wave used increases.

In the ultrasonic diagnostic apparatus of the present invention, as shown in FIG. 1 (c), the control circuit 8 calculates the delay amount β in each transmission / reception channel 1a and applies it to each transmission / reception channel. It is the one. Therefore, each transmit / receive channel
In 1a, since the delay amount β corresponding to the medium with different sound velocity inside the living body is given, the azimuth resolution can be obtained without using the circuit for detecting the deviation of the reception time or the correction circuit corresponding to the deviation as in the past. Can be improved.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 described above is an explanatory view of the principle of the present invention, and FIGS. 2 to 5 are views showing an embodiment of the present invention.

The ultrasonic diagnostic apparatus of the present invention is provided with a plurality of transmission / reception channels 1a as shown in FIG. 1 (c), and when synthesizing ultrasonic signals of the respective transmission / reception channels 1a, An ultrasonic diagnostic apparatus for converging an ultrasonic beam by applying a predetermined delay amount β to 1a, which is based on sound speeds corresponding to a plurality of media (for example, fat layer and liver) that compose the subject. The means (corresponding to claim 1) that uses the delay amount β calculated according to each transmission / reception channel 1a is a means necessary for implementing the present invention. Note that the same reference numerals indicate the same object throughout the drawings.

The configuration and operation of the ultrasonic diagnostic apparatus of the present invention will be described below with reference to FIGS. 2 to 5 with reference to FIG. FIG. 2 shows an example in which the ultrasonic diagnostic apparatus of the present invention is provided with an operator 80 that can arbitrarily specify the thickness of the fat layer. In the control circuit 8, the operator operates the operator 80 in response to each thickness of the fat layer in the living body to selectively specify the thickness of the fat layer.
Calculate the delay amount β to be inserted into each transmission / reception channel 1a.

At this time, the thickness of the fat layer inside the subject is
The operator, for example, visually measures from the B-mode image and operates the operator 80 according to the measured thickness of the fat layer, thereby enabling highly accurate phasing addition, and more azimuth. An image with high resolution can be obtained.

Further, as shown in FIG. 2, a plurality of delay data storage units 9 are provided, and the delay amount β corresponding to each transmission / reception channel 1a corresponding to the thickness of the fat layer inside the living body is
It is also possible to calculate and store in advance and operate the operator 80 to select an appropriate delay amount β. {Embodiment corresponding to claim 2} FIG. 3 shows an example in which a patient identification data section 81 is provided in the ultrasonic diagnostic apparatus of the present invention. In this case, for example, by operating the operator 80 to select a predetermined patient identification data from the patient identification data section 81, the patient identification data is inserted into each transmission / reception channel 1a in synchronization with the selected patient identification data. The delay amount β to be calculated can be calculated.

Therefore, with respect to a patient who has once been diagnosed, the operator again measures the thickness of the fat layer, and
This saves the trouble of selecting the delay amount β to be inserted in a. {Example corresponding to claim 3} As described above,
The fat layer in the living body has different thicknesses depending on the subject, and the sound velocity is particularly slow compared to other organs.Therefore, in consideration of the fat layer, the delay amount β corresponding to each transmission / reception channel 1a is determined. It is important to make a decision.

Since the fat layer usually has a thickness of 1 mm or more and 50 mm or less, when the delay amount is calculated and used in advance, a plurality of data are stored in this range within the plurality of delay data storage units. You can store it in 9.

Further, as described above, the sound velocity inside the living body is not uniform, and in particular, the sound velocity value in the fat layer is 1476 m / s,
It is slower than the previously assumed value (1530 m / s) and the liver is 1
About 570m / s, which is faster than the conventional assumed value.

Therefore, in the ultrasonic diagnostic apparatus of the present invention,
Of the multiple media (fat layer and liver) excluding the acoustic lens of the ultrasound probe 1, the sound velocity value of a given medium is, for example, 1500
less than m / s, the sound velocity value of the medium other than the specified medium is 150
The delay amount β for synthesizing the ultrasonic signals of the plurality of transmission / reception channels 1a is calculated at 0 m / s or more. {Examples corresponding to claims 4, 5 and 6} FIG.
Is the maximum amplitude detection circuit in the ultrasonic diagnostic apparatus of the present invention.
The example which provided is shown. As described above, since the acoustic impedance between fat inside the living body and the liver is significantly different, the amplitude of the reflected signal from the boundary is large. Therefore, as shown in FIG. 4, a maximum amplitude detection circuit 10 for detecting the reception time of the maximum amplitude of the ultrasonic transmission / reception signal is provided, and the maximum amplitude reception wave time detected by the maximum amplitude detection circuit 10 is fat Assuming layers, each of the above transmission and reception channels 1
By determining the delay amount β corresponding to a, it is possible to automatically prevent the phase shift due to the fat layer. {Embodiment corresponding to claim 5} In the ultrasonic diagnostic apparatus provided with the maximum amplitude detection circuit 10 for detecting the fat layer in the living body, the following parameters are set in association with the data of the thickness of the fat layer. By automatically changing, it becomes possible to obtain an image with higher resolution.

(1) FIG. 5 (a) shows an example in which the electrical focal length of the ultrasonic beam is adjusted to the diagnostic region according to the thickness of the fat layer. That is, in general, in the inside of the living body, for example, the liver is present at a deep position from the surface of the living body by the thickness of the fat layer inside the living body.
In the control circuit 8, the delay amount for the electric focus (the delay amount α in FIG. 1) is increased according to the thickness of the fat layer.

(2) FIG. 5 (b) shows the relationship between the ultrasonic frequency f and the amplitude R of the reflection signal.
It can be seen that the frequency characteristic shifts to a low region. Therefore, when the maximum amplitude detection circuit 10 detects that the fat layer is thick, the control circuit 8 lowers the drive frequency for the piezoelectric element in association with the thickness of the fat layer so that the deep part can be diagnosed. To do.

(3) In FIG. 5 (c), the characteristics of the bandpass filter used for increasing the S / N of the reflected signal in the ultrasonic diagnostic apparatus correspond to the thickness of the living body (thickness of fat layer). Then, it is shown that it shifts to the low range. Therefore, in the present invention, when the maximum amplitude detection circuit 10 detects that the fat layer is thick, the control circuit 8 shifts the characteristic of the bandpass filter to a low band in conjunction with the thickness of the fat layer. Let's make it possible to see deep inside.

(4) FIG. 5D shows the difference in the sound field distribution when the probe 1 used in the ultrasonic diagnostic apparatus is divided into the thickness direction and used. Generally, when the opening of the probe 1 is large, the sound field (directivity) at a short distance becomes bad as shown by the dotted line. However, if an acoustic lens is used to correct the near field, the reflected signal will be attenuated.
By dividing and using the thickness direction of, the good sound field is obtained corresponding to the thickness to the region of interest inside the living body.

Therefore, when the ultrasonic probe 1 divided in the thickness direction is used, the object with thick fat has a deep diagnostic region, so that the control circuit 8 has a large opening in the thickness direction. Also, for a subject with thin fat, since the diagnosis region is shallow, the control circuit 8 controls so that the opening in the thickness direction becomes small.

In the above embodiments, fat is taken as a part inside the human body having different sound velocities. However, the part having different sound velocities is not limited to fat, and similar control is performed also on parts such as amniotic fluid and ascites. By doing so, the lateral resolution can be improved.

As described above, the present invention has a plurality of transmission / reception channels, and when synthesizing ultrasonic signals of the respective channels, an ultrasonic diagnostic apparatus for converging the ultrasonic beams by giving a predetermined delay to each channel. In, the delay amount β calculated based on the sound velocities corresponding to the plurality of media forming the subject is used. An operator is provided for changing the delay amount data according to the thickness of the medium of the fat layer of the subject. Also, the delay amount data is changed in association with the patient identification data. Further, the sound velocity value of one medium is set to, for example, less than 1500 m / s, and the sound velocity value of the other medium is set to 1500 m / s or more, corresponding to the plurality of media. Further, in order to observe the thickness of the fat layer, a circuit for detecting the reception time of the maximum amplitude of the ultrasonic transmission / reception signal is provided, and the sound velocity of the medium before the reception time is, for example, less than 1500 m / s. The sound velocity of the medium before the reception time is controlled to be 1500 m / s or more.

[0038]

As described above in detail, according to the ultrasonic diagnostic apparatus of the present invention, in each transmission / reception channel,
Since the delay amount β corresponding to media having different sound velocities inside the living body is given, the azimuth resolution is improved without using a circuit for detecting a shift in reception time or a correction circuit corresponding to the shift as in the conventional case. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 shows an embodiment of the present invention (part 1).

FIG. 3 shows an embodiment of the present invention (part 2).

FIG. 4 shows an embodiment of the present invention (part 3).

FIG. 5 shows an embodiment of the present invention (part 4).

FIG. 6 is a diagram illustrating a conventional ultrasonic diagnostic apparatus.

[Explanation of symbols]

1 Ultrasonic probe, probe 1a Transmission / reception channel 1b Piezoelectric element 2 Transmission / reception circuit 3 Delay circuit 4 Addition circuit 5 Detection circuit 6 Digital scan converter (DSC) 7 Display device (CRT) 8 Control circuit 80 Operator 81 Patient identification Data section 9 Multiple delay data storage section 10 Maximum amplitude detection circuit

Claims (7)

[Claims] 1. An ultrasonic diagnostic apparatus comprising a plurality of transmission / reception channels, wherein when synthesizing ultrasonic signals of the respective transmission / reception channels, an ultrasonic beam is converged by giving a predetermined delay amount to each transmission / reception channel. An ultrasonic diagnostic apparatus characterized in that a delay amount β calculated based on sound speeds corresponding to a plurality of media forming the subject is used for each transmission / reception channel. 2. The ultrasonic diagnostic apparatus according to claim 1, further comprising an operator for changing the delay amount β in accordance with the thickness of a predetermined medium forming the subject. An ultrasonic diagnostic apparatus characterized by the above. 3. The ultrasonic diagnostic apparatus according to claim 2, further comprising means for changing the delay amount β in accordance with the inputted patient identification data. . 4. The ultrasonic diagnostic apparatus according to claim 1, 2, or 3, wherein a sound velocity value of a predetermined medium among a plurality of media excluding the acoustic lens of the ultrasonic probe is A A delay amount β for synthesizing the ultrasonic signals of the plurality of transmission / reception channels is calculated by setting the sound velocity value of the medium other than the predetermined medium to A m / s or more, and setting the sound velocity value to less than m / s. Sound wave diagnostic equipment. 5. The ultrasonic diagnostic apparatus according to claim 1, further comprising a circuit for detecting a reception wave time of the maximum amplitude of the ultrasonic transmission / reception signal, wherein the sound velocity value of the medium before the reception wave time is B
less than m / s, and the sound velocity value of the medium after the received wave time is Bm /
An ultrasonic diagnostic apparatus, wherein a delay amount β for synthesizing ultrasonic signals of the plurality of transmission / reception channels is calculated as s or more. 6. The ultrasonic diagnostic apparatus according to claim 4, wherein the sound velocity value A or B is 1500 m / s. 7. The ultrasonic diagnostic apparatus according to claim 5, wherein the electric focal length of the ultrasonic beam, the driving frequency of the ultrasonic piezoelectric element, or the ultrasonic wave is linked with the received wave time. An ultrasonic diagnostic apparatus comprising means for changing at least one of a frequency filter characteristic of a received signal and a thickness opening of an ultrasonic probe.