JPH0542137A - Ultrasonic diagnostic device - Google Patents

Abstract

PURPOSE:To secure a prescribed penetration and to hold detection sensitivity and Doppler sensitivity so as to be constant and satisfactory, even if a swing angle of a scanning beam is varied in an oblique scan, a sector scan, etc. CONSTITUTION:A linear probe 10 is connected to a linear electronic scanning part 11, this scanning part 11 is connected to a Doppler processing part 12 and a display part 14, by which the probe 10 is attached to an oblique scan, and the images of B mode, M mode and Doppler mode are displayed on a display part 14. In the linear electronic scanning part 11, an echo filter 26 for selecting a band for forming an image is inserted into its receiving system, and the center frequency of this echo filter 26 is varied by a transmission/ reception control part 13. The transmission/reception control part 13 inputs swing angle information, and as a swing angle theta becomes larger, the center frequency of the echo filter 26 is lowered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnostic apparatus, and more particularly, to an oblique scanning method for a linear probe or a sector scanning method for a sector probe in which ultrasonic transmission / reception signals are obliquely scanned with respect to a vibration surface. The present invention relates to a diagnostic device according to the method.

[0002]

2. Description of the Related Art Conventionally, as one of scanning methods of a linear probe, as shown in FIG. 4 (a), a scanning line (raster) is usually orthogonal to a transducer plane (that is, a swing angle θ = 0 degree). There is a scanning method. It has been pointed out that the device using the normal scanning method has a lack of Doppler sensitivity because the running of superficial blood vessels is often parallel to the body surface. To alleviate this lack of Doppler sensitivity, a method called oblique scanning is often used in linear probes. In this oblique scanning, as shown in FIG. 4B, the scanning line is swung by θ = θ ₁ degree in the direction orthogonal to the transducer surface, and the aperture is sequentially moved similarly to the normal scanning method. It is something to do. By adding this swing angle,
The Doppler signal can be received with high sensitivity from the blood flow running parallel to the body surface.

On the other hand, in an apparatus equipped with a sector probe, as shown in FIG. 5, sector scanning is performed in which a scanning line is scanned in a fan shape with respect to the transducer surface.

[0004]

However, at the time of diagnosis, as shown in FIG. 6, the diagnosis depth is the distance in the direction orthogonal to the transducer plane, and the sound path is the distance between the point of interest and the center of the opening. Then, when the oblique scan is performed, the swing angle θ
Since the sound path length for the same depth becomes longer as the value becomes larger, the penetration (here, “the depth at which the ultrasonic signal of the minimum energy that can be detected by the device is returned is compared to the swing angle θ = 0 degree. Is smaller). In particular, it is difficult to secure the penetration because the biological attenuation is large during high frequency driving. Schematically, comparing the swing angle θ = 0 ° and 30 ° at an ultrasonic frequency = 7.5 MHz, for example, θ = 30 when θ = 0 °
In case of degrees, "-4 dB" at a depth of 30 mm and a depth of 60
A decrease in sensitivity of "-8 dB" in mm is expected. That is,
As the swing angle θ is increased, there is a problem that not only the detection sensitivity is lowered and the diagnostic ability is lowered, but also the S / N ratio and the image quality are lowered. Further, during the sector scanning, since the sound path length changes for each scanning line of the sector scanning, there is a problem in that the detection sensitivity also changes for each scanning line and causes variations.

The present invention solves the above-mentioned problems of the prior art. When performing oblique scanning or sector scanning, a constant good penetration is maintained and stable even if the swing angle of the ultrasonic beam changes. An object of the present invention is to provide an ultrasonic diagnostic apparatus capable of ensuring detection sensitivity.

[0006]

In order to achieve the above object, an ultrasonic diagnostic apparatus according to the present invention has a plurality of transducers capable of bidirectionally converting a voltage signal and an ultrasonic signal,
A probe such as a linear probe or a sector probe, and an electronic scanning unit such as oblique scanning or sector scanning for driving the probe to scan the ultrasonic beam obliquely with respect to the transducer surface are provided. In an ultrasonic diagnostic apparatus configured to reconstruct a diagnostic image based on a received signal,
The electronic scanning unit includes a transmission / reception condition control unit that changes transmission / reception conditions of the ultrasonic beam so as to cancel a change in sound path length due to a difference in swing angle of the ultrasonic beam.

The transmission / reception condition control means may be, for example, a drive voltage for a vibrator, a drive pulse width for a vibrator, a burst number of drive pulses for a vibrator, a vibrator for transmission, a vibrator for reception, an echo filter. Is a means for controlling at least one of the center frequency, the mixing frequency of frequency conversion in the signal processing process, the center frequency of phase control in signal delay, and the reference frequency in the Doppler method.

The transmission / reception condition control means, for example, when controlling the center frequency of the echo filter, when the center frequency of the echo filter when the swing angle θ = 0 degree is f (0), the swing angle When θ = θn, the center frequency f (θn) of the echo filter is f (θn) = f
(0) · cos Set to θn.

Further, the transmission / reception condition control means, for example, when controlling the mixing frequency of the frequency conversion, when the mixing frequency is f (0) when the swing angle θ = 0 degree, the swing angle θ = Θn, the mixing frequency f (θn) is f (θn) = f (0) · cos
Set to θn.

[0010]

According to the present invention, the transmission / reception condition control means in the electronic scanning section changes the transmission / reception conditions of the ultrasonic beam such as lowering the center frequency of the echo filter of the receiving circuit as the swing angle of the ultrasonic beam increases. With this, when the swing angle in the living body becomes large, the penetration becomes large by lowering the reception beam frequency,
An almost constant penetration is secured regardless of the swing angle.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

First Embodiment A first embodiment will be described with reference to FIGS.

In the figure, reference numeral 1 indicates a partial cross section of a living body to be diagnosed, and reference numeral 2 indicates a linear electronic scanning type ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus 2 is a composite apparatus of the tomography method and the Doppler method, and is a linear probe 10 that transmits and receives ultrasonic signals to and from the living body 1, and a linear electronic scanning unit 11 that commands the probe 10 to perform oblique scanning. A Doppler processing unit 12 that obtains a Doppler signal that uses the received signal of the linear electronic scanning unit 11, a transmission / reception control unit 13 that controls transmission / reception conditions of the linear electronic scanning unit 11, and a linear electronic scanning unit 1
1 and a display unit 14 that receives the processing results of the Doppler processing unit 12 and displays them on a monitor. Here, the linear electronic scanning unit 11 and the transmission / reception control unit 13 form an electronic scanning unit.

The probe 10 uses a piezoelectric element as a vibrator,
N transducers 10a, ..., 10a are arranged in a strip shape.

The linear electronic scanning unit 11 comprises a reference oscillator 20 for generating a reference pulse signal, a delay line 21 for delay, which constitutes a transmission system upon receiving the output pulse signal of the reference oscillator 20, and a pulser for driving a probe. 22 and an electronic switch 23 for switching between transmission and reception. The electronic switch 23 can electrically and selectively connect the plurality of input / output terminals connected to the probe 10 and the plurality of input / output terminals connected to the pulser 22 for each scan.

A receiving system is also provided on the side of the electronic switch 23 to which the transmitting system is connected. In addition to the electronic switch 23, this receiving system includes a preamplifier 24 for amplification, a delay line 21, an adder 25, an echo filter 26, and a detector 27. The electronic switch 23 and the delay line 21 are used for both transmission and reception. Delay line 2
1 and the adder 25 form a reception beam having a directivity of a predetermined scanning angle (swing angle) θ by delaying and adding (phasing addition) the reception signals converted into voltage signals. The addition output value of the adder 25 is the intensity of the reception beam in the θ direction.

The echo filter 26 is a filter for selecting in which frequency band of the received signal an image is reconstructed, and the center frequency of the selected band (the center frequency of the pass band) is controlled by the transmission / reception control unit 13. It has become so. Specifically, when the center frequency of the echo filter 26 at the swing angle θ = 0 degrees is f (0), the swing angle θ
The center frequency f (θn) when θ = θn is set to f (θn) = f (0) · cos θn (1) and the frequency is lowered by “f (0) (1-cos θn)”. This equation (1) will be proved using FIG. If the biological attenuation is α (dB / MHz · mm), the point of interest x in Fig. 2
In order to have the same sensitivity for (0) and x (θ), α · f (0) · 2r (0) = α · f (θ), where r (0) and r (θ) are the sound paths, respectively.・ 2r (θ) r (0) = r (θ) ・ cos θ must be established, and therefore r
By deleting (0), f (θ) = f (0) · cos θ is obtained.

The transmission / reception control unit 13 is formed, for example, by mounting a microcomputer, inputs information on the swing angle θ set by the operator, calculates the center frequency f (θ) based on the above equation (1), and A control signal corresponding to the calculated value is supplied to the echo filter 26. In this embodiment, the transmission / reception control unit 13 and the echo filter 26 form transmission / reception condition control means.

On the other hand, the Doppler processing unit 12 uses the adder 2
The two mixers 30a and 30b and the low-pass filter 31 for receiving the phasing addition output signal of FIG.
a and 31b, sample and hold circuits 32a and 32b for extracting only Doppler signals having a certain depth, band filters (Doppler filters) 33a and 33b for removing unnecessary low-frequency Doppler signals, and A / D converters. 34a, 34b
And FFT (Fast Fourier Transform) 35 for frequency analysis
It has a conventionally well-known configuration in which the and are provided as shown in FIG.
In the figure, reference numeral 36 is a phase shifter that gives a phase difference of π / 2.

Further, the display unit 14 inputs the B mode and M mode image signals output from the linear electronic scanning unit 11 and the Doppler spectrum signal output from the Doppler processing unit 12 to display each image. Then, it is equipped with a digital scan converter, a D / A converter, a TV monitor and the like which are not shown.

Next, the function and effect of the above embodiment will be described.

When transmitting, the linear electronic scanning unit 11 gives different delay times in the delay line 11 so that the wavefronts from the respective transducers 10a coincide in the scanning angle θ direction, and the N arrayed transducers 10a, ..., The driving is performed while sequentially shifting a predetermined number of 10a. As a result, the synthesized ultrasonic transmission beam propagates in the living body in a direction oblique to the orthogonal direction of the transducer surface by the swing angle θ and is scanned in the azimuth direction (transducer array direction). Further, upon reception, an arbitrary number of all transducers 10a, ...
The received signal is received by a, and the received signal is input to the delay line 21 and the adder 25 via the preamplifier 24 to perform phasing addition. As a result, a reception beam having a predetermined observation direction and position is formed by calculation, and image data related to the beam having a strong directivity is obtained as the output of the adder 25.

The signal corresponding to the added reception beam is filtered by the echo filter 26 into a signal in the frequency band set at that time, and then the detection circuit 2
Sent to 7. At this time, the larger the scanning angle (deflection angle) θ of the oblique scanning instructed by the operator, the lower the center frequency of the echo filter 26 is based on the equation (1). For example, when a large swing angle θ is commanded, the frequency band of the reception beam is shifted to the lower frequency side, so that the amount of biological attenuation is reduced, the penetration is increased, and sensitivity deterioration is compensated. On the contrary, when the swing angle θ is set small, the frequency band of the reception beam shifts to the high frequency side, and the penetration is adjusted to a predetermined value. In this way, even if the sound path length changes with the change of the swing angle θ, the B-mode penetration is kept at the desired optimum value and the resolution changes, but high detection sensitivity is maintained. The S / N ratio is also improved and the diagnostic ability is improved. Further, it is possible to eliminate the trouble of setting the swing angle to 0 degree in order to examine the deep part and then swinging the beam to take the Doppler image, and to shorten the examination time.

The output of the adder 25 is the Doppler processing unit 1.
Also sent to 2. Since the Doppler processing unit 12 extracts the Doppler signal and sends the spectrum signal to the display unit 14, the display unit 14 displays the Doppler image together with the B-mode and M-mode images of linear scanning.

In the above embodiment, the shift amount of the center frequency of the echo filter 26 is based on the equation (1), and in addition to this equation, a factor considering the frequency characteristic of the transmission / reception system is set. May be.

Further, in the above embodiment, when the frequency conversion of the received signal is performed by the linear electronic scanning unit 11 to shift the band to the low frequency side, the mixing frequency is calculated based on the equation (1). Similarly, the mixing frequency when the swing angle θ = 0 degree is f (0), and the mixing frequency when the swing angle θ = θn is f (θn), the same control may be performed.

Further, although the transmission / reception condition control means in the above embodiment is formed by the echo filter 26 and the transmission / reception control section 13, the present invention is not limited to this. For example, first, the transmission / reception control unit 13 controls at least one of the number of elements (number of transducers) at the time of transmission and the number of elements (number of transducers) at the time of reception of the electronic switch 23 according to the swing angle θ. May be. In other words, when the number of elements is increased during transmission, a strong ultrasonic beam is emitted, and when the number of elements is increased during reception, a strong echo beam is obtained.
When the swing angle θ is increased, by increasing the number of elements to be driven at one time, a predetermined penetration of the B-mode image can be maintained, a certain detection sensitivity can be ensured, and the Doppler sensitivity can be stabilized.

Secondly, the transmission / reception control unit 13 may control the pulsar 22 in accordance with the swing angle θ to change the drive voltage, that is, the voltage at which the voltage of the oscillator is excited. When the crest value of the drive voltage is increased, the radiated ultrasonic wave is intensified, so that a certain penetration of the B-mode image is secured when the swing angle θ is increased,
The detection sensitivity can be kept good and the Doppler sensitivity can be kept stable.

Thirdly, the transmission / reception controller 13 may change the drive pulse width for exciting the oscillator in accordance with the swing angle θ. When the width per pulse is narrowed, the excitation energy shifts to the high frequency side, and when it is widened, it has a low frequency component. Therefore, when the swing angle θ is large, the drive pulse width is widened to lower the frequency. The biological attenuation is reduced, a predetermined penetration of the B-mode image is secured, the increase in the sound path length is covered, and the detection sensitivity is not lowered. In addition, the Doppler sensitivity can be stabilized.

Fourthly, the transmission / reception control unit 13 may control the pulsar 22 in accordance with the swing angle θ to change the burst number of the drive pulse. If you increase the number of bursts,
Since the band is narrowed, the ultrasonic energy is concentrated, and the penetration can be increased, so that the constant penetration of the B-mode image can be maintained, the detection sensitivity can be kept good, and the Doppler sensitivity can be stabilized.

Fifth, although not shown, in the case of a system in which the received signal is converted to an intermediate frequency by the heterodyne method and then processed, or in the system in which the quadrature detection is performed for each channel, the mixing frequency is May be controlled. That is, when the swing angle θ becomes large and the sound path length becomes long, the mixing frequency is controlled so as to be an intermediate frequency on the lower frequency side, so that a certain penetration is maintained and the detection sensitivity is increased. Prevent deterioration.

Sixth, in the case of performing the phase control for the signal delay, the center frequency may be changed to the lower frequency side as the swing angle θ becomes larger to prevent the deterioration of the detection sensitivity and stabilize the Doppler sensitivity. ..

Further, seventhly, in the case where the Doppler method is mainly used, the reference frequency (transmission frequency) is changed to a lower frequency side as the swing angle θ becomes larger, and the penetration is kept constant. , Doppler sensitivity can be stabilized.

Of course, the transmission / reception conditions may be appropriately combined and controlled according to the swing angle θ.

Second Embodiment A second embodiment will be described with reference to FIG. The second embodiment is applied to a sector electronic scanning type ultrasonic diagnostic apparatus, and the same reference numerals are used for the same components as in the first embodiment, and the description thereof will be simplified or omitted.

The ultrasonic diagnostic apparatus 40 shown in the figure diverts a sector probe 41 for sector scanning, a sector electronic scanning unit 42 for instructing the probe 41 to perform sector scanning, and a reception signal of the sector electronic scanning unit 42. A Doppler processing unit 12 for obtaining a Doppler signal, a transmission / reception control unit 13 for controlling transmission / reception conditions of the sector electronic scanning unit 42, and a display unit for receiving and displaying the processing results of the sector electronic scanning unit 42 and the Doppler processing unit 12 on a monitor. 14 and. The sector electronic scanning unit and the transmission / reception control unit 13 form the electronic scanning unit of the invention.

Among them, the sector electronic scanning section 42 is not equipped with the electronic switch for switching the vibrator in the first embodiment, but is directly connected to the pulsar 22 of the transmission system and the preamplifier 24 of the reception system. And the reference oscillator 2
The sector scanning can be commanded by being biased by the reference pulse signal from 0. In addition, the sector electronic scanning unit 4
The center frequency of the echo filter 26 in 2 is controlled by the transmission / reception control unit 13. The transmission / reception control unit 13 inputs the swing angle θ information which is sequentially changed from “+ θm” to “−θm” in the sector scan, calculates the center frequency using the information and the equation (1), and calculates the calculated value. The center frequency of the echo filter 26 is controlled for each scanning line.

The Doppler processing unit 12 and the display unit 14 have the same structure as in the first embodiment.

In the sector electronic scanning of the second embodiment, the sound path length, the element factor, and the lens attenuation amount change for each scanning line. Even in that case, the transmission / reception control unit 13 is also available.
Changes the signal pass band of the echo filter 26 (raises and lowers) to change the penetration, canceling out the change in penetration due to the sound path length, element factor, and lens attenuation. For this reason, even if the swing angle θ changes for each scanning line, the degree of sensitivity variation between each scanning becomes extremely small, and a uniform image can be obtained and S / N.
The ratio is improved and good diagnostic ability can be exhibited.

The transmission / reception condition control means (formed by the echo filter 26 and the transmission / reception control unit 13) of the second embodiment also has the same function as the first embodiment, depending on the swing angle θ during sector scanning. Drive voltage, drive pulse width, number of drive pulse bursts, number of transducers for transmission and reception, mixing frequency during frequency conversion, center frequency when performing phase control with signal delay, or reference frequency when using the Doppler method It may be configured to control. Further, the control may be performed by combining arbitrary conditions such as combining the frequency of the echo filter and the driving voltage.

[0041]

According to the present invention, the transmission / reception condition control means provided in the electronic scanning section for instructing the oblique scanning or the sector scanning, for example, becomes larger as the swing angle of the scanning line increases.
Change the transmission / reception conditions of the ultrasonic beam so as to cancel the change in the sound path length between the diagnostic position and the difference in the swing angle of the ultrasonic beam, such as lowering the center frequency of the echo filter or the mixing frequency of frequency conversion. Therefore, even if the swing angle of the scanning line changes, a certain penetration is ensured, so that, for example, during oblique scanning, the detection sensitivity hardly changes due to the swing angle, and the S / N ratio is improved. In addition, the Doppler sensitivity is stabilized, the diagnostic ability is improved, and the examination time is shortened. Also,
At the time of sector scanning, the same effect as described above can be obtained, and the sensitivity variation between the scanning lines can be suppressed, and a uniform image can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an ultrasonic diagnostic apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram for calculating a center frequency of an echo filter corresponding to a swing angle θ.

FIG. 3 is a block diagram showing a schematic configuration of an ultrasonic diagnostic apparatus according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a swing angle associated with linear scanning,
(A) is an explanatory view during normal scanning (θ = 0), and (b) is an explanatory view during oblique scanning.

FIG. 5 is an explanatory diagram illustrating a swing angle associated with sector scanning.

FIG. 6 is an explanatory diagram showing a relationship between a diagnosis depth and a sound path length during oblique scanning.

[Explanation of symbols]

 1 Living Body 2 Linear Electronic Scanning Ultrasonic Diagnostic Device 10 Linear Probe 11 Linear Electronic Scanning Unit 13 Transmission / Reception Control Unit 26 Echo Filter 40 Sector Electronic Scanning Ultrasonic Diagnostic Device 41 Sector Probe 42 Sector Electronic Scanning Unit

Claims (6)

[Claims] 1. A probe having a plurality of transducers capable of bidirectionally converting a voltage signal and an ultrasonic signal, and an electron for driving the probe to scan an ultrasonic beam obliquely with respect to a transducer surface. In an ultrasonic diagnostic apparatus that includes a scanning unit and reconstructs a diagnostic image based on a reception signal of the electronic scanning unit, the electronic scanning unit includes a sound path length associated with a difference in swing angle of the ultrasonic beam. An ultrasonic diagnostic apparatus including a transmission / reception condition control means for changing transmission / reception conditions of an ultrasonic beam so as to cancel the change of 2. The probe is a linear probe,
The ultrasonic diagnostic apparatus according to claim 1, wherein the electronic scanning unit is configured to perform oblique scanning. 3. The probe is a sector probe,
The ultrasonic diagnostic apparatus according to claim 1, wherein the electronic scanning unit is configured to perform sector scanning. 4. The transmission / reception condition control means, the drive voltage of the oscillator, the drive pulse width of the oscillator, the burst number of drive pulses of the oscillator, the number of oscillators during transmission, the number of oscillators during reception, an echo filter. 3. A means for controlling at least one of a center frequency of, a mixing frequency of frequency conversion in a signal processing process, a center frequency of phase control in signal delay, and a reference frequency in Doppler method.
Alternatively, the ultrasonic diagnostic apparatus according to 3 above. 5. The transmission / reception condition control means is means for controlling the center frequency of the echo filter, and when the center frequency of the echo filter is f (0) when the swing angle θ = 0 degree, The center frequency f (θn) of the echo filter when the swing angle θ = θn is f (θn) = f
The ultrasonic diagnostic apparatus according to claim 2 or 3, wherein (0) · cos θn is set. 6. The transmission / reception condition control means is means for controlling a mixing frequency of the frequency conversion, and the mixing frequency when the swing angle θ = 0 degree is f (0).
The ultrasonic diagnostic apparatus according to claim 2, wherein the mixing frequency f (θn) when the swing angle θ = θn is set to f (θn) = f (0) · cos θn.