JP3688566B2 - Ultrasonic diagnostic equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to a multistage transmission focus technique.
[0002]
[Prior art]
By performing delay control on each transmission signal supplied to the plurality of vibration elements constituting the array transducer, a transmission beam having a transmission focus point at a predetermined depth is formed. On the other hand, by performing delay addition (phased addition) on each reception signal from a plurality of vibration elements, a reception beam is formed electronically. In this case, a plurality of reception focus points are formed per reception by so-called reception multistage focus or reception dynamic focus.
[0003]
In order to perform multi-stage transmission focus, ultrasonic waves are transmitted and received a plurality of times per beam direction, that is, a plurality of transmission beams are formed while changing the depth of the transmission focus point. That is, a plurality of region-of-interest ranges are set in the depth direction, and a focus point is set for each region-of-interest range to form a sharp transmission beam, thereby capturing echo data. Although the frame rate is lowered, the image quality of the ultrasonic image is generally improved.
[0004]
[Problems to be solved by the invention]
When performing multi-stage transmission focus, the size of the transmission / reception aperture (especially the transmission aperture) is usually variably controlled. Specifically, a small transmission / reception aperture is set when the transmission focus point is shallow, and a size transmission / reception aperture is set when the transmission focus point is deep. For this reason, since the number of reception signals to be phased and added is switched between the reception signals corresponding to the transmission focus points, the signal sound pressures after the phase addition are different from each other. Therefore, conventionally, the difference in sound pressure due to the difference in the size of the transmission / reception aperture has been eliminated by gain adjustment.
[0005]
However, the sound pressure cannot be completely adjusted by the gain adjustment. For example, the sound pressure of echoes reflected according to the nature of the medium through which the ultrasonic wave passes does not change linearly.
[0006]
The present invention has been made in view of the above-described conventional problems, and an object thereof is to make it possible to form a more natural ultrasonic image when performing stepwise transmission focus.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention performs transmission / reception of an ultrasonic wave a plurality of times in each beam direction by changing the transmission focus point stepwise in the depth direction, and receives a reception signal composed of a plurality of reception signals in each beam direction. A transmission / reception control unit that acquires a signal set; a weighting synthesis unit that applies a weighted synthesis process to each received signal set and outputs a synthesized signal; and an image forming unit that forms an ultrasound image using the synthesized signal. , only contains the weighting synthesis process, for each received signal, a large weighting values are set in the main responsibility around the transmission focus point, a small weighting value according to the distance in the beam direction from the main responsibility Is set, and the main assigned ranges of the received signals constituting the received signal set are set apart from each other, and weights are set between the adjacent assigned ranges in the beam direction. A crossover range is set, and in the weighting synthesis process, all of a plurality of reception signals constituting the reception signal set are used from a shallow area to a deep area in the beam direction, and each reception signal constituting the reception signal set is used. A weighting value as a contribution is set for a range other than the main assigned range and the weighted crossover range in the beam direction .
[0008]
According to the above configuration, while switching the transmission focus point per direction (generally while switching the reception focus point in conjunction with it), the ultrasonic pulse per direction is transmitted a plurality of times, and each transmission has different characteristics. A received signal is obtained. These received signal sets are input to weighting / synthesizing means, and each received signal is weighted according to the focus point corresponding to the received signal, and each received signal after such weighting is synthesized. Therefore, unlike the prior art, it is possible to avoid the discontinuity that occurs when the received signals are divided in the depth direction and simply connected, and the image quality of the ultrasonic image can be improved. Here, the ultrasonic image is, for example, a B-mode tomographic image or a color Doppler image. The present invention is also applicable when so-called 1 transmission 2 reception is performed. Note that the transmission / reception direction may be switched sequentially in units of multiple transmissions / receptions with different focus depths, or the focus depth is changed after transmission / reception is performed in all directions without changing the focus depth. The same transmission / reception may be repeated. It is desirable that the weighting pattern (function) is appropriately adjusted according to the strength and depth of the transmission focus point, the strength and depth of the reception focus point, and the like.
[0009]
Weighting pricing function may be a linear function having a bending resistance, but may be a function that varies gently. In the above configuration, the entire range in the depth direction of each received signal is summed target. On the other hand, a partial range in the depth direction may be selectively added to each received signal. In any case, it is desirable to perform weighted addition so that the switching of the transmission focus and the reception focus is not noticeable on the image.
[0010]
Incidentally, in each transmission / reception wave, it is desirable that the depth of the transmission focus point and the depth of the reception focus point coincide, but in the present invention, they do not necessarily coincide. In addition, although the main assigned range in weighting is individually set around these focus points, the central point of the main assigned range does not have to be the focus point.
[0011]
Crossover range is overlapped range, the gradient of the weighting is an area for cross.
[0012]
Preferably, the weighting pattern for the received signal set is different between adjacent beams. If the weighting pattern is changed between adjacent beams in this way, the joint at the time of switching the focus point can be made inconspicuous.
[0013]
In order to achieve the above object, the present invention performs transmission / reception of an ultrasonic wave a plurality of times in each beam direction by changing the transmission focus point stepwise in the depth direction, and from a plurality of received signals in each beam direction. A reception signal set comprising: a transmission / reception control unit that changes the size of the transmission / reception opening stepwise in accordance with the switching of the transmission focus point; and for each reception signal that constitutes the reception signal set, Gain correction means for performing gain correction according to the size of the transmission / reception aperture, weighting synthesis means for applying a weighted synthesis process to each received signal set after the gain correction, and outputting a synthesized signal, and using the synthesized signal Te image forming means for forming an ultrasound image, only contains the weighting synthesizing process, large for each received signal, the primary contact range around the transmission focus point A weighting value is set, and a smaller weighting value is set as the distance from the main assigned range becomes farther in the beam direction, and the main assigned ranges of the received signals constituting the received signal set are set apart from each other in the beam direction. A weighted crossover range is set between adjacent main assigned ranges, and in the weighted synthesis process, all of a plurality of received signals constituting the received signal set are used from a shallow region to a deep region in the beam direction, and the received signal For each received signal constituting the set, a weighting value as a contribution is set for a range other than the main assigned range and the weighted crossover range in the beam direction .
In addition, the present invention performs transmission / reception of ultrasonic waves four times in each beam direction while changing the transmission focus point stepwise in the depth direction, and obtains a reception signal set composed of four reception signals in each beam direction. Transmission / reception control means, weighting synthesis means for applying a weighted synthesis process to four received signal sets for each received signal set and outputting a synthesized signal, and image forming means for forming an ultrasonic image using the synthesized signal In the weighting synthesis process, for each received signal, a large weighting value is set in the main assigned range centered on the transmission focus point, and the smaller the weighted value as the distance from the main assigned range is in the beam direction. Is set, and the main assigned ranges of the received signals constituting the received signal set are set apart from each other, and are set between the adjacent assigned ranges in the beam direction. A weighted crossover range is set, and in the weighted combining process, four received signals, three received signals, or two received signals in the received signal set for each region from a shallow region to a deep region in the beam direction. A signal is used to change the number of combined additions.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.
[0015]
FIG. 1 shows a preferred embodiment of an ultrasonic diagnostic apparatus according to the present invention, and FIG. 1 is a block diagram showing the overall configuration thereof.
[0016]
In FIG. 1, a probe 10 is an ultrasonic probe that is used in contact with a body surface or inserted into a body cavity. In the probe 10, an array transducer including a plurality of vibration elements is built. An ultrasonic beam is scanned by applying electronic scanning to the array transducer, thereby forming a scanning plane. Incidentally, examples of the electronic scanning method include electronic linear scanning and electronic sector scanning.
[0017]
A transmitter 10 and a receiver 14 are connected to the probe 10. The transmission unit 12 is a circuit controlled by the scanning control unit 16, and in the present embodiment, the ultrasonic pulse is transmitted a plurality of times per direction, and the transmission focus point is switched for each transmission. . That is, so-called multistage transmission focus is realized. Such transmission control is realized by the scanning control unit 16, and the transmission aperture is gradually enlarged as the transmission focus point is switched from a short distance to a long distance in a plurality of transmissions for each direction. ing. Here, the transmission aperture corresponds to the number of vibrating elements that function during transmission in the array transducer. This transmission multistage focus itself is known. Therefore, when one scanning plane has M transmission / reception azimuths, N transmissions / receptions are performed for each azimuth, and as a result, M × N transmission / receptions are performed per scanning plane.
[0018]
In the present embodiment, after N transmissions / receptions are performed per certain transmission / reception direction, the transmission / reception directions are switched, and the same N transmissions / receptions are performed, and this is repeated. However, M transmission / reception may be executed for each azimuth while the transmission focus point is fixed, after which the transmission focus point may be switched, and M transmission / reception may be executed again for each azimuth, and this may be repeated.
[0019]
The reception unit 14 is a circuit that performs so-called phasing addition on a plurality of reception signals output from the array transducer in the probe 10 and thereby electronically forms a reception beam. The operation of the receiving unit 14 is controlled by the scanning control unit 16. As described above, transmission / reception is performed N times for each transmission / reception direction, and accordingly, N reception signals (reception signals after phasing addition) are obtained for each transmission / reception direction. Sets different reception focus points for each reception. In this embodiment, the transmission focus point and the reception focus point coincide with each other. However, the focus points can be shifted from each other, and the strength of the focus can be individually set. is there. This reception multistage focus itself is known.
[0020]
FIG. 2 shows the scanning plane S. The scanning surface S is formed by electronically scanning an ultrasonic beam. FIG. 2 shows an ultrasonic beam θ1 having a specific orientation as a representative. A plurality of focus points F1 to F4 are intermittently set on the beam, and these focus points F1 to F4 are transmission focus points and reception focus points. For example, in the first transmission / reception # 1, the transmission focus control and the reception focus control are executed by setting the transmission / reception focus point to the depth determined by F1, and this is the second transmission / reception # 2 and the third transmission / reception. It is repeatedly executed while switching the focus point for each of # 3 and fourth transmission / reception # 4. Such N transmissions / receptions are executed for each transmission / reception direction.
[0021]
In FIG. 1, a scanning control unit 16 is a circuit that controls the transmission unit 12 and the reception unit 14 described above, and in particular performs electronic focus control and electronic scan control. In the present embodiment, setting control of the transmission aperture and the reception aperture in each transmission / reception is also performed. Incidentally, similarly to the transmission aperture set at the time of transmission, a reception aperture having a width corresponding to the depth of the reception focus point is set at the time of reception. Such a technique is also used in the conventional reception multistage focus.
[0022]
In the memory 20, a plurality of reception signals obtained for each direction, that is, reception signals after phasing addition are stored. Although it is possible to store all received signals in the scanning plane S in the memory 20 and then read out and perform image processing, in the present embodiment, in the memory 20, the first transmission / reception # 1 is performed. ~ Three reception signals from the third transmission / reception # 3 are stored, and when the reception signal obtained by the fourth transmission / reception # 4 is obtained, the three reception signals stored in the memory 20 are read out. These four received signals are input to the weighted addition unit 22 in parallel. Of course, such a configuration example is an example, and various configurations can be adopted as long as weighted addition described later can be performed.
[0023]
The weighting addition unit 22 sets a weighting function for each received signal as shown in FIG. 3 and executes gain adjustment according to the weighting function. The control is executed by the synthesis control unit 24, and the synthesis control unit 24 performs control such as gain adjustment in the reception unit 14, write / read control of the memory 20, in addition to the control of the weighted addition unit 22. .
[0024]
In FIG. 3, (A) to (E) show weighting functions for setting gains of reception sound rays # 1 to # 4 corresponding to the respective reception signals, that is, reception beams. As shown in the figure, in the reception sound ray # 1, a large weighting value is given in a certain range in the vicinity of the probe in correspondence with the setting of the transmission focus point and the reception focus point in the vicinity of the probe. The range is indicated by reference numeral 100 in the figure. In the reception sound ray # 2, a large weighting value is set in a range 102 slightly shifted from the range 100 in the depth direction. Further, in the reception sound ray # 3, a range 104 is set at a position further away from the range 102 in the depth direction, and a large weighting value is set in the range 104. Similarly, a large weighting value is set in the range 106 set at the deepest position in the reception sound ray # 4. These ranges 100, 102, 104, and 106 correspond to the main assigned ranges in the respective reception sound rays, and the ranges 108, 110, and 112 are set as crossing ranges, that is, overlap areas between the main assigned ranges. Has been. For example, in the range 108, the gain of the reception sound ray # 1 is gradually decreased along the depth direction, and on the other hand, the gain of the reception sound ray # 2 is gradually increased along the depth direction. ing. The same applies to the ranges 110 and 112.
[0025]
Incidentally, (E) shows the component ratio in the synthesized sound line when the received signals of those received sound lines # 1 to # 4 are synthesized. In the shallow range with respect to the probe, the received sound line # One component is dominant, and components of each reception sound ray are dominantly set step by step. Here, in this embodiment, a small weight is given to each reception sound ray other than the assigned range and the crossing range, that is, the heavy bid price is completely zero in the range other than the main assigned range and the intersecting range. A certain amount of contribution is working on the synthesized sound ray that is finally formed. According to such a configuration, from the viewpoint of spatial resolution, the received signal component in the main charge range can be used more dominantly to improve the image quality, and the sound power can be effectively utilized by using all received signals from shallow to deep areas. There is an advantage that it is possible to increase. Therefore, it is possible to improve the image quality in that sense. Of course, the four received signals from the shallow area to the deep area are not always weighted and added. For example, two or three received signals may be synthesized and added for each area.
[0026]
The synthesis control unit 24 shown in FIG. 1 sets parameters when performing weighted addition as shown in FIG. 3. For example, such synthesis addition conditions are set according to ultrasonic transmission / reception conditions and various conditions. It is also possible to variably set. Incidentally, the main control unit 18 controls the entire ultrasonic diagnostic apparatus, and the main control unit 18 controls the scanning control unit 16 and the composition control unit 24.
[0027]
The synthesized received signal output from the weighted addition unit 22 is input to a digital scan converter (DSC) 26 as in the conventional apparatus, and the DSC 26 performs coordinate conversion and interpolation processing on the received signal. As a result, a so-called B-mode tomographic image is formed, and the image data is input to the image processing unit 27, subjected to necessary image processing, and finally sent to the display unit 28. A B-mode tomographic image is displayed.
[0028]
In FIG. 1, the configuration of Doppler processing is not clearly shown, but of course the present invention can also be applied when displaying Doppler information as an image, and further forms two-dimensional images as well as three-dimensional images and M-mode images. It is also applicable in some cases. Furthermore, the present invention can be applied to the case where two reception beams are formed per transmission beam.
[0029]
According to the embodiment shown in FIG. 1, it is possible to improve the image quality by relaxing the joint between the focus points or the sections in which the focus is performed, and using all four received signals per transmission / reception direction. Since image formation can be performed, there is an advantage that the SN ratio (signal-to-noise ratio) can be improved and the image quality of ultrasound can be improved in that sense.
[0030]
In the present embodiment, the weighted addition unit 22 described above performs weighted addition of four received signals. That is, the signals having the same depth between the four received signals are added while performing predetermined weighting, thereby generating synthesized data. Such weighted addition unit 22 functions as an addition filter in a certain sense. The gain function shown in FIG. 3 has a characteristic like a broken line, but a gain function like a logistic curve with rounded corners as shown in FIG. 5 can also be used. By using such a function, there is an advantage that the boundary can be made inconspicuous and a more natural ultrasonic image can be formed. Further, as shown in FIG. 4, it is possible to further reduce the joint between the beams by alternately switching the weighting function pattern, that is, the weighting pattern, between the adjacent ultrasonic beams. That is, a weighting function as shown in FIG. 3 is applied on a certain ultrasonic beam, and each range in the function shown in FIG. 3 is shifted in the depth direction on an adjacent ultrasonic beam. By setting them alternately, the seam is made inconspicuous as a whole. Of course, such a weighting pattern can be set at random.
[0031]
Incidentally, the synthesis control unit 24 performs gain control in the reception unit 14 as described above, and specifically, gain adjustment for adjusting the level between the reception signals based on the sizes of the transmission aperture and the reception aperture. It is carried out. For example, in FIG. 3, W1 is set as the opening width for the reception sound ray # 1, and W2, W3, and W4 are set as the opening widths for the reception sound rays # 2, # 3, and # 4 in the same manner. . Therefore, if the aperture width is different, a difference occurs in the level of the received signal obtained after the phasing addition. Therefore, the synthesis control unit 24 adjusts the gain of the amplifier in the reception unit 14 according to the size of the aperture width. Yes.
[0032]
In the above embodiment, the case where the electronic sector scanning is applied has been described. However, the present invention can be used when various electronic scanning methods other than the electronic linear scanning are applied.
[0033]
【The invention's effect】
As described above, according to the present invention, there is an advantage that the image quality of an ultrasonic image can be improved.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a preferred embodiment of an ultrasonic diagnostic apparatus according to the present invention.
FIG. 2 is a diagram illustrating a relationship between a scanning plane and a focus point.
FIG. 3 is an explanatory diagram showing a gain function for each received sound ray in weighted addition.
FIG. 4 is an explanatory diagram showing a case where different weighting patterns are set between adjacent ultrasonic beams.
FIG. 5 is an explanatory diagram showing another gain function.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Probe, 12 Transmission part, 14 Reception part, 16 Scan control part, 18 Main control part, 20 Memory, 22 Weighting addition part, 24 Composition control part, 26 Digital scan converter (DSC), 27 Image processing part, 28 Display part .

Claims (5)

Transmission / reception control means for performing transmission / reception of ultrasonic waves per beam direction by changing the transmission focus point stepwise in the depth direction, and acquiring a reception signal set consisting of a plurality of reception signals for each beam direction;
Applying weighting synthesis processing for each received signal set and outputting a synthesized signal;
An image forming means for forming an ultrasonic image using the synthesized signal;
Only including,
In the weighting synthesis process, for each received signal, a large weighting value is set in the main charge range centered on the transmission focus point, and a smaller weighting value is set as the distance from the main charge range increases in the beam direction.
The main assigned ranges of each received signal constituting the received signal set are set apart from each other, a weighted crossing range is set between the main assigned ranges adjacent in the beam direction,
In the weighting synthesis process, all of a plurality of reception signals constituting the reception signal set are used from a shallow region to a deep region in the beam direction,
An ultrasonic diagnostic apparatus, wherein for each received signal constituting the received signal set, a weighting value as a contribution is set for a range other than the main assigned range and the weighted crossover range in the beam direction . The apparatus of claim 1 .
An ultrasonic diagnostic apparatus, wherein the weighting pattern for the received signal set is different between adjacent beams. The transmission focus point is changed stepwise in the depth direction to perform transmission / reception of ultrasonic waves multiple times for each beam direction, and a means for obtaining a reception signal set consisting of a plurality of reception signals for each beam direction,
A transmission / reception control means for changing the size of the transmission / reception opening stepwise according to the switching of the transmission focus point;
Gain correction means for performing gain correction in accordance with the size of the transmission / reception aperture for each reception signal constituting the reception signal set;
Applying weighting synthesis processing for each received signal set after gain correction, and outputting a synthesized signal;
An image forming means for forming an ultrasonic image using the synthesized signal;
Only including,
In the weighting synthesis process, for each received signal, a large weighting value is set in the main charge range centered on the transmission focus point, and a small weighting value is set as the distance from the main charge range increases in the beam direction. The main assigned ranges of each received signal constituting the received signal set are set apart from each other, a weighted crossing range is set between the main assigned ranges adjacent in the beam direction,
In the weighting synthesis process, all of a plurality of reception signals constituting the reception signal set are used from a shallow region to a deep region in the beam direction,
An ultrasonic diagnostic apparatus, wherein for each received signal constituting the received signal set, a weighting value as a contribution is set for a range other than the main assigned range and the weighted crossover range in the beam direction . The apparatus of claim 1.
The ultrasonic diagnostic apparatus, wherein a weighting pattern for the received signal set is different between adjacent beams. A transmission / reception control means for performing transmission / reception of ultrasonic waves four times in each beam direction by changing the transmission focus point stepwise in the depth direction, and acquiring a reception signal set composed of four reception signals in each beam direction;
Applying weighting synthesis processing for each received signal set and outputting a synthesized signal;
Image forming means for forming an ultrasonic image using the combined signal;
Including
In the weighting synthesis process, for each received signal, a large weighting value is set in the main charge range centered on the transmission focus point, and a small weighting value is set as the distance from the main charge range increases in the beam direction. The main assigned ranges of each received signal constituting the received signal set are set apart from each other, and a weighted crossing range is set between the main assigned ranges adjacent in the beam direction,
In the weighted combining process, four received signals, three received signals, or two received signals in the received signal set are used for each region from a shallow region to a deep region in the beam direction, and combined. An ultrasonic diagnostic apparatus characterized in that the addition number changes.

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