JPH0360492B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic diagnostic apparatus, and particularly to an improvement in an ultrasonic diagnostic apparatus that diagnoses a subject by transmitting and receiving an ultrasonic beam toward the subject.

In recent years, ultrasonic diagnostic devices that perform diagnosis using ultrasound have been widely used. This ultrasonic diagnostic apparatus utilizes the fact that tissues and organs within the body have different acoustic characteristics. In other words, when an ultrasound beam is repeatedly emitted into the body at a fixed period, a portion of the ultrasound is reflected at the boundaries of different tissues as it propagates through the body, and these reflected echoes are detected and displayed on a cathode ray tube. If so, it is possible to display the distribution of acoustic characteristics of internal tissue. At that time, if the ultrasound beam is scanned along a predetermined region of the subject, a predetermined tomographic plane of the subject will be displayed on the cathode ray tube, and healthy tissue and tumor tissue have different acoustic characteristics. Therefore, the presence or absence of an abnormality within the tissue and its location can be determined from the pattern displayed on the cathode ray tube.

In order to display good diagnostic images by transmitting and receiving ultrasound beams in such ultrasound diagnostic equipment, it is necessary to appropriately adjust the focal length of the ultrasound beams that are transmitted and received into the subject. be. For this reason, conventional diagnostic equipment divides the observation area within the subject by depth, and transmits and receives ultrasound beams with a focal length that corresponds to the depth of the observation area. It was forming an image. Therefore, the obtained tomographic image of the subject shows good azimuth resolution even in the depth direction, and when using this diagnostic device to diagnose internal organs, etc., it is difficult to obtain reliable diagnostic information. It was possible.

However, in conventional diagnostic devices, the focus of the ultrasound beam is adjusted by selectively controlling each dividing element of a transducer that is divided into multiple parts in the ultrasound beam scanning direction. Although it is possible to adjust the focus in the direction, it is not possible to adjust the focus in the width direction perpendicular to the scanning plane, and the focus is fixed at a constant depth by an acoustic lens laminated on the transducer surface. It was fixed.

For this reason, diagnostic images obtained by transmitting and receiving ultrasound beams exhibit extremely good width-direction azimuth resolution in the depth region of the width-direction focal length;
The drawback is that the resolution is relatively reduced in depth regions other than this.

The present invention has been made in view of these conventional problems, and its purpose is to adjust the focal length of an ultrasound beam that is transmitted and received toward a subject, not only in the scanning direction of the ultrasound beam but also in this scanning plane. It is an object of the present invention to provide an ultrasonic diagnostic apparatus that also allows adjustment in the width direction orthogonal to the width direction and can obtain good diagnostic images in the depth direction of the subject.

To achieve this objective, the device of the present invention includes a plurality of vibrators that are divided and formed in a scanning direction in which electronic scanning is performed and a width direction perpendicular to the scanning direction, and an excitation voltage of the vibrator is changed as the focal length becomes longer. Therefore, an excitation voltage generation circuit that generates excitation voltage pulses of a plurality of different levels by setting a high level, and an excitation voltage generation circuit that selects the excitation voltage pulse according to the focal length and outputs it from the excitation voltage generation circuit to output a transmission timing pulse. a transmission control circuit that charges the voltage of the excitation voltage pulse; and a switching element that inputs the transmission timing pulse and switches the transmission pulse according to the excitation voltage pulse charged in accordance with the switching. A transmission pulse generation circuit that outputs a discharge, a first excitation circuit that receives the transmission pulse output from the transmission pulse generation circuit and excites the vibrator only in the center, and inputs the transmission pulse output from the transmission pulse generation circuit. and a second excitation circuit that compares the transmitted pulse with a predetermined reference value and excites vibrators other than the central portion as the predetermined voltage level becomes higher than the reference value level. The circuit excites only the central part of the plurality of transducers in the width direction, and the second excitation circuit excites the transducers in the width direction as the predetermined voltage level becomes higher than the reference value level. and a selection circuit that performs selection control to increase the number of oscillators selected in the scanning direction and the transducers selected in the width direction by the selection circuit to perform focus adjustment in the depth direction of the subject. It is characterized by forming one ultrasonic beam.

Next, a preferred embodiment of the ultrasonic diagnostic apparatus of the present invention will be described based on the drawings.

FIG. 1 shows a preferred embodiment of the transducer used in the ultrasonic diagnostic apparatus of the present invention, and the transducer 10 of the embodiment is n
It is formed divided into columns.

The ultrasonic diagnostic apparatus of the embodiment transmits and receives ultrasound beams from the transducer surface by sequentially selecting and controlling each divided element of the transducer 10 divided into n columns in this way and controlling the excitation. It's on. and,
The ultrasonic beam is transmitted and received sequentially from one side to the other side along the vibrator surface of the divided vibrator 10, and the object to be cut by this ultrasonic beam scanning surface is The tomographic image of the specimen is displayed on a monitor's cathode ray tube in almost real time.

Here, in order to improve the resolution of tomographic images, the ultrasound diagnostic equipment divides the observation area by depth.
Ultrasonic beams whose focal lengths are adjusted according to the depth of each observation area are transmitted and received, and a tomographic image is formed using reflected echoes obtained from the observation areas at each depth. Therefore, the tomographic image displayed on the cathode ray tube exhibits extremely good azimuth resolution in the scanning direction with respect to the depth direction of the subject.

The ultrasonic diagnostic apparatus of this embodiment adjusts the focal length of the ultrasonic beam in the depth direction as described above.
As shown in Figure 2, this is happening. That is, when setting the focal length in the short distance region f ₁ , excitation control is applied to the four divided elements, and when setting the focal length in the intermediate distance region f ₂ , the excitation control is applied to the six divided elements simultaneously. When controlling and setting the focal length in the long distance region _f3 , the excitation of eight divided elements is controlled at the same time.

However, with this type of focal length adjustment, the focal length of the ultrasound beam can only be adjusted in the ultrasound beam scanning direction; It is not possible to adjust the focal length in the depth direction of the object.

The ultrasonic diagnostic apparatus of the present invention was developed with attention to these points, and its feature is that the transducer is divided into a plurality of pieces in the width direction perpendicular to the scanning plane of the ultrasonic beam. The excitation voltage of the vibrator is set according to the focal length, and selection control is performed to increase the number of vibrators to be excited in the width direction according to the predetermined voltage level. The object of the present invention is to form one ultrasonic beam whose focus is adjusted in the depth direction of the subject by using the transducer selected in the width direction and the transducer.

In the embodiment, the vibrator 10 is divided into three equal parts A, B, and C in the width direction, and depending on the depth of the observation area, only the central divided element A is excited and controlled, or these divided elements A, Excitation control is applied to both B and C. In the vibrator 10, by selectively controlling the divided elements to be excited and controlled in this manner, the third
As shown in the figure, when controlling the excitation of only the central dividing element A, the widthwise focal length of the ultrasonic beam is set to the short distance area _f4 , and dividing elements A, B, C
When excitation is controlled for all at the same time, the focal length in the width direction of the ultrasonic beam is in the far range f ₅ (f ₂ < f ₅ < f ₃ )
It will be set to .

Here, it is necessary to adjust the focal length of the ultrasonic beam in the depth direction in the scanning direction and the width direction at the same time, and in the embodiment, when the focal length in the scanning direction is set to f ₁ , the focal length in the width direction is set to f ₄ ,
If the focal length in the scanning direction is set to f ₂ or f ₃ , the focal length in the width direction is
f set to ₅ .

In the embodiment, the transducer 10 is shown divided into three equal parts in the width direction, but if necessary, if the transducer 10 is divided into even smaller parts, the ultrasonic waves transmitted and received by controlling the excitation of the transducer 10 can be It becomes possible to more finely adjust the focal length of the beam in the width direction.

FIG. 4 shows a vibrator 10 formed in this way.
A control circuit for the focal length in the width direction is shown.

When transmitting and receiving ultrasound beams toward a subject, the ultrasound beam is attenuated as it propagates within the subject. Must be set to high level. Conversely, when observing a short-distance area where the influence of such attenuation is small, if the excitation voltage of the transducer 10 is set to a high level, it becomes necessary to set the dynamic range of the receiving system to a wide band. Furthermore, it is necessary to prevent multiple reflections between the transducer surface, the subject, and each interface within the subject. Therefore, when observing a short distance area, it is necessary to set the excitation voltage of the vibrator to a low level.

Therefore, in the embodiment, the power supply circuit 20 serves as an excitation voltage generation circuit that sets the excitation voltage of the vibrator 10 to a higher level as the focal length becomes longer.
is provided, and is set to an appropriate value depending on, for example, the focal length in the width direction. This power supply circuit 20 is connected to the selector 22 by a transmission voltage switching signal from the transmission control section 38.
The excitation voltages V1, V2, V3, .

This transmission pulse generation section 26 is formed with a resistor 28, a switching element 30, and a capacitor 34, and the switching element 30 is on/off controlled by a trigger pulse output from the transmission trigger generation section 32, which is input from the power supply circuit 20. A pulse waveform with a peak value approximately equal to the voltage excitation signal voltage is input to the selection circuit 36 via the capacitor 34.

Here, the selector 22 of the power supply circuit 20 and the trigger circuit 32 are controlled by the transmission control section 38' while maintaining constant synchronization.
A transmission voltage switching signal is input from 8 to the selector 22, and after charging of the capacitor 34 is completed, a transmission timing signal is input to the trigger generation section 32. Therefore, the voltage instructed by the transmission control unit 38 is output from the power supply circuit 20, and the capacitor 34
After charging is completed, a trigger pulse is outputted from the transmission trigger generation section 32 to the switching element 30, and the pulse waveform has a peak value that is approximately equal to the voltage excitation signal voltage outputted from the power supply circuit 20, and the first excitation circuit and the first excitation circuit Selection circuit 3 consisting of two excitation circuits
6 will be input.

The selection circuit 36 inputs the excitation signal voltage output from the power supply voltage circuit 20, and selectively controls the number of vibrators to be excited in the width direction to increase as the predetermined voltage level becomes higher. . In this way, the predetermined divided elements A, B, and C of the vibrator 10 are selected and switched according to the pulse voltage of the input excitation pulse. Then, the selected predetermined divided element is excited and controlled using the transmission pulse outputted from the transmission pulse generator 26.

Here, since this selection circuit 36 connects the output end of the transmission pulse generation section 26 and the electrode surface of the dividing element A formed at the center of the vibrator 10 through a diode 40, the transmission pulse generation section 26 When a transmission pulse is output from the first excitation circuit, the central divided element A is selected regardless of its voltage level, and the central divided element A is excited and controlled using the pulse voltage. . Further, this selection circuit 36 uses a second excitation circuit to connect the output terminal of the transmission pulse generator 26 and the diodes 42 and capacitor 44 of the dividing elements B and C of the vibrator 10.
This diode 42
The anode side of is connected to the power supply terminal of the threshold voltage _VTHRE via a resistor 46. For this reason,
Unless the transmission pulse generator 26 outputs a transmission pulse exceeding the absolute value of the threshold voltage V _THRE , the diode 42 will not be rendered conductive. Therefore, the divided elements B and C of the vibrator 10 receive the threshold voltage from the transmission pulse generator 26.
Excitation control is performed only when a transmission pulse exceeding the absolute value of V _THRE is output.

As a result, when the transmission pulse output from the transmission pulse generation section 26 is smaller than the threshold voltage V _THRE , only the divided element A located at the center of the vibrator 10 is controlled to excite, and the transmission pulse output from the transmission pulse generation section 26 is controlled to excite. When a transmission pulse having a voltage greater than the absolute value of the threshold voltage V _THRE is output, all of the divided elements A, B, and C of the vibrator 10 are controlled to excite.

As described above, according to the present invention, one ultrasonic beam with focus adjustment is formed in the depth direction of the object by the transducer selected in the scanning direction and the transducer selected by the selection circuit. do. That is, in the ultrasonic diagnostic apparatus of this embodiment, the divided elements A, whose excitation is controlled on the transducer 10,
The selection switching between B and C is performed according to the voltage absolute value of the transmission pulse output from the transmission pulse generator 26, and the excitation voltage is controlled according to the focal length. It becomes possible to obtain good diagnostic images with high resolution over a long distance.

Furthermore, the ultrasonic diagnostic apparatus of this embodiment employs a structure in which the selection circuit 36 is activated by the output voltage of the power supply circuit 20 that sets the excitation voltage of the transducer 10. The excitation voltage can be set at the same time, and the circuit configuration can be simplified.

FIG. 5 shows a timing chart showing the operation of the ultrasonic diagnostic apparatus configured as described above. The focal length of the beam in the scanning direction is adjusted in conjunction.

That is, as described above, the apparatus of the embodiment divides the observation area of the object into three parts according to the depth, and
To form the scanning lines of a book, ultrasonic beams with focal lengths set according to these depths are transmitted and received three times, and the resulting diagnostic images have high resolution in any observation area. .
In the apparatus of this embodiment, the focal length of the ultrasonic beam in the scanning direction is adjusted to the short distance f ₁ in accordance with the transmission and reception of the ultrasonic beam three times forming one scanning line.
When the scanning direction focal length of the ultrasonic beam is set to the middle distance _f2 , the voltage level is controlled to be output to the selection circuit ₃₆ . is controlled to output a transmission pulse of voltage level V ₂ to the selection circuit 36, and when the scanning direction focal length of the ultrasound beam is set to a long distance f ₃ , the selection circuit outputs a transmission pulse of voltage level V ₃ . 36.
Here, voltage V ₁ is the threshold voltage
It is set smaller than the absolute value of V _THRE , and the voltage
V ₂ and V ₃ are set larger than the absolute value of the threshold voltage V _THRE , and the absolute value of V ₃ is set larger than the absolute value of V ₂ .

Therefore, when the focal length of the ultrasound beam in the scanning direction is set to a short distance _f1 , the selection circuit 36
Since a transmission pulse of voltage V ₁ is input to , only the divided element A located at the center of the vibrator 10 is excited and controlled, and its focal length in the width direction is also set to a short distance f ₄ .

Also, the focal length of the ultrasound beam in the scanning direction is medium distance.
When set to f ₂ , a transmission pulse of voltage V ₂ whose absolute voltage value is larger than the absolute value of _{the threshold} voltage V The divided element A is at voltage level _V2 , and the divided elements B and C are at voltage level V2.
The excitation will be controlled by V ₂ − |V _THRE |. This allows, in addition to adjusting the focal length in the scanning direction,
Its widthwise focal length is also set to a medium distance _f5 .

Also, the focal length of the ultrasound beam in the scanning direction is long.
When set to f ₃ , the threshold voltage is sent from the transmission pulse generator 26 to the selection circuit 36.
A transmit pulse with a voltage level V ₃ higher than V _THRE is input. Therefore, the dividing element A on the vibrator 10 is at the voltage level V ₃ , and the dividing elements B and C are at the voltage level V ₃
Since the excitation is controlled by the transmission pulse of -| _THRH |, the focal length of the ultrasound beam in the width direction is set to a middle distance _f5 in accordance with the focal length in the scanning direction.

In this way, in the apparatus of this embodiment, the width direction focal length of the ultrasound beam is adjusted in conjunction with the scanning direction focal length adjustment, and high-resolution received echoes can be obtained from each observation region. A diagnostic image of the subject formed based on these received echoes has extremely high resolution.

In addition, in the device of this embodiment, as the focal length of the ultrasound beam is set to short, middle, or long distances, the excitation voltage on the transducer surface is reduced to a low level voltage.
Since V ₁ is sequentially switched to high-level voltages V ₂ and V ₃ , the ultrasonic beam scanned toward the subject is set to be weak at a short distance, and set to be strong as the distance increases. As a result, it becomes possible to transmit and receive ultrasound beams that take into account the attenuation that the ultrasound beam receives when propagating inside the subject, and it is possible to obtain received echoes of similar strength from observation areas at all depths. Therefore, it is possible to set the dynamic range of the receiving mechanism to be narrow. Furthermore, during short-range observation, the received echoes are rarely so strong that multiple reflections occur between the transducer surface, the object, and the interfaces within the object. Furthermore, the sound pressure of the ultrasound beams transmitted and received toward the subject is always set at an appropriate level, so for example, when diagnosing a pregnant woman, the sound pressure of the ultrasound beam may be too high and hit the subject. It doesn't have any negative impact either.

FIG. 6 shows the calculation results of the widthwise focal length of the ultrasonic beam transmitted and received by the apparatus of the present invention. In the graph shown in FIG. 6, the horizontal axis represents the depth of the observation region of the subject, and the vertical axis represents the beam diameter in the width direction of the ultrasound beam. Note that the calculation was performed by forming the width of each divided element A, B, and C of the vibrator 10 to be 6 mm, and setting the focal length on the vibrator surface.
This is done using a stack of 100mm acoustic lenses.

In the figure, the characteristic curve 100 corresponds to the central dividing element A.
The characteristic curve 200 shows the characteristics when the excitation of the divided elements A, B, and C is simultaneously controlled. As is clear from this figure,
When only the central dividing element A is excited and controlled,
The focal length is set for the depth of the observation area of about 35 mm, and all the divided elements A,
When the excitation of B and C is controlled, the focal length of this ultrasonic beam is set at a depth of approximately 87 mm. Therefore, if an ultrasonic transducer with the characteristics shown in Fig. 6 is used, and the resolution in the width direction is set to 4 mm, the depth will be approximately 150 mm.
It becomes possible to obtain good diagnostic images up to a certain area.

In order to compare with the data shown in FIG. 6, FIG. 7 shows calculation results of the widthwise focal length of an ultrasound beam transmitted and received by a conventional diagnostic device. The calculations are performed assuming that the width of the transducer surface is 10 mm, and that an acoustic lens with a focal length of 70 mm is stacked on the transducer surface.

As is clear from both the data shown in FIGS. 6 and 7, the ultrasonic diagnostic apparatus of the present invention is capable of obtaining good diagnostic images over a wide range of areas from short distances to long distances.

As explained above, the ultrasonic diagnostic apparatus of the present invention can also focus the ultrasonic beam in the width direction perpendicular to the scanning plane. When diagnosing a specimen, a good diagnostic image can be obtained regardless of the depth of the specimen. In particular, by adjusting the focal length of the ultrasound beam in the width direction in conjunction with the adjustment of the focal length of the ultrasound beam in the scanning direction,
Clearer diagnostic images can be obtained, for example,
When diagnosing a living body or the like, it becomes possible to obtain accurate and detailed diagnostic information from a subject.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a transducer used in the ultrasonic diagnostic apparatus of the present invention, and FIGS. 2 and 3 are illustrations of this first transducer.
4 is a circuit diagram showing an example of the excitation circuit of the oscillator shown in FIG. 1, and FIG. 5 is a timing chart of the circuit shown in FIG. 4. , FIG. 6 is a characteristic diagram showing the characteristic curve of the focal length in the width direction of the ultrasonic diagnostic apparatus of the present invention, and FIG. 7 is a characteristic diagram showing the characteristic curve of the focal length in the width direction of the conventional ultrasonic diagnostic apparatus. 10... vibrator, 20... power supply circuit, 36...
Selection circuit, A, B, C...dividing elements.

Claims (1)

[Scope of Claims] 1. In an ultrasonic diagnostic apparatus that electronically scans an ultrasound beam in a predetermined direction while controlling excitation of a plurality of transducers and adjusting focus in the depth direction, a scanning direction in which the electronic scanning is performed and a scanning direction; A plurality of vibrators are divided and formed in orthogonal width directions, and an excitation voltage generation circuit that sets the excitation voltage of the vibrators to a higher level as the focal length becomes longer, and generates excitation voltage pulses of a plurality of different levels. a transmission control circuit that selects the excitation voltage pulse according to the focal length and causes the excitation voltage generation circuit to output the transmission timing pulse; and a transmission control circuit that selects the excitation voltage pulse according to the focal length and outputs the transmission timing pulse. a transmission pulse generation circuit that discharges and outputs a transmission pulse corresponding to the excitation voltage pulse charged according to the switching, including a switching element that inputs and switches; and a transmission pulse generation circuit that inputs the transmission pulse output from the transmission pulse generation circuit. The first oscillator excites only the central part of the oscillator.
A transmission pulse outputted from an excitation circuit and the transmission pulse generation circuit is input, and the transmission pulse is compared with a predetermined reference value, and as the predetermined voltage level becomes higher than the reference value level, a second excitation circuit that excites the vibrators of the plurality of transducers; the first excitation circuit excites only the central vibrators among the plurality of widthwise vibrators; a selection circuit that selectively controls the number of vibrators to be excited in the width direction to increase as the level becomes higher than the level, the vibrators selected in the scanning direction and the selection circuit selected in the width direction. An ultrasonic diagnostic apparatus characterized in that a single ultrasonic beam whose focus is adjusted in the depth direction of a subject is formed using a transducer.