JPS6129736B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multi-beam synchronous scanning type real-time ultrasonic tomography apparatus,
In other words, it is intended to enable high-resolution display of POIs of objects that are moving at relatively high speeds, such as heart valves.

A scanning method called the compound method is used to increase the resolution of medical ultrasound tomographic imaging devices, but recently a method called the multi-beam simultaneous scanning method has been proposed to perform this in real time. This method uses multiple ultrasound beams to perform scanning in parallel.
As a simple example, FIG. 1 shows the scanning principle of a compound type electronic real-time tomographic imaging apparatus that uses two ultrasound beams simultaneously. There are various types of scanning by ultrasonic beams, such as linear scan and sector scan. Figure 1 shows an example of sector scan, in which two ultrasonic beams are transmitted and received at different origins O _A and O _B. Pulsed ultrasonic beams A ₀ to _{A N-1} and
B ₀ to B _N ′ _-1 are fan-shaped tomographic fields (sectors).
Form A and B. Sectors A and B intersect their visual field central axes C _A and C _B at an angle θ, so that some areas overlap.

As for the scanning procedure, at time t= _t1 , the beam
A ₁ and B ₁ are simultaneously transmitted and received, and at t=t ₂ , beams A ₂ and B ₂ are simultaneously transmitted and received, and one frame is completed by repeating this operation. Note that the number of scans N of beam A and the number of scans of beam B
It does not necessarily have to be equal to N'. Furthermore, the beams do not necessarily need to be transmitted and received simultaneously, and a slight time lag is allowed. Therefore, since the object POI located within the overlapping area of sectors A and B will be observed from two directions, it is expected that the resolution will be improved compared to a tomographic imaging apparatus that uses only one of sectors A or B. In other words, if only sector A is used, if an obstacle exists between the origin O _A and the object POI, the POI part that will be in the shadow of the obstacle will not be observed, and the outline of the POI will be uneven. If this is the case, the shadowed part seen from the origin O _A will not be observed at all or very well, but if sector B is used in conjunction with this, the POI can be observed from different angles, so such obstacles can be removed or It is hoped that this will not become a problem. However, if the beam scanning order is fixed as A ₀ to B ₀ , A ₁ to B ₁ , etc. as described above, a problem will arise for moving objects. To explain this with reference to FIG. 2, for example, at time t
An image (part of) of the shape shown in the figure a is captured and displayed by the beam A _i at =ti at time t = tj
In this case, the image will be displayed as (a part of) an image as shown in the figure b by the beam _Bj (because it moves, it will be in a dotted line state or a solid line state). This does not fully utilize the advantage of the compounding method, which ``displays a high-resolution image by simultaneously scanning and overlapping the same image from multiple directions.'' This tendency becomes more noticeable as the POI moves at higher speeds, and in the worst case, there is no point in displaying the video signals obtained by the beams A _i and B _j overlappingly on the same surface of the display device.

For example, the present invention can be applied to a beam
Instead of simultaneous scanning of A ₀ and B ₀ , beam A ₁ and B ₁ , ……………, beam A _i-1 and beam B _j-1 , beam A _i and beam B _j , By making both beams of the POI part scan simultaneously, such as beam A _i+1 and beam B _j+1 , ......, the compound method can be used even for moving POIs. The object of the present invention is to provide an ultrasonic tomographic imaging device that can exhibit advantages. In order to achieve this object, the present invention provides a multi-beam scanning type ultrasonic wave transmitter/receiver that scans a predetermined tomographic field of view with an ultrasonic beam, and is provided with at least two ultrasonic transducers that overlap a part of each tomographic field of view. In the ultrasound imaging device, the ultrasound transmission timing of each ultrasound transducer is adjusted so that the ultrasound beams from each ultrasound transducer are synchronized at any observation target site within the overlapping area of the tomographic field of view. It is characterized in that it is provided with an adjusting means for making it intersect, and this will be explained in detail below with reference to the illustrated embodiment.

FIG. 3 shows an embodiment of the present invention applied to an electronic sector scan system, in which a two-beam system is used as in FIG. 1, and the CRT display is assumed to be of a one-electron gun system. In the same figure, KA and
KB is a counter for specifying the beam number of sector A and sector B, respectively, and DEF is not shown.
A circuit for generating X-axis and Y-axis deflection signals X and Y for the CRT display, SW1 and SW2 are panel switches for specifying the number i of beam A _i and the number j of beam B _j to be crossed at the POI, SW3 is the beam A _k (k=0 to N-1) and beam B _k
'(k' = 0 to N'-1), the switch for selecting numbers k and k' (this is the scanning line number for scanning by the electron beam on the display side), SUB is (j-i). A subtraction circuit for calculation, COMP is a comparator for detecting that the value of counter KA has reached i specified by panel switch SW1, and TC is a clock for counters KA and KB.
A timing circuit for generating CK and preset command PST, and a switching signal SLCT for switching the display display between sector A and sector B for each scanning line.ANGL is for two sectors during compound scan. Angle between A and B (first
Z is a brightness modulation circuit that outputs a signal Z' that applies brightness modulation to the electron beam on the display side that is deflected by the deflection signals X and Y. The input of the brightness modulation circuit Z is the video signal VDO obtained by reflection of each ultrasonic beam and the coincidence output (control signal) D of the comparator COMP.Normally, it gives a brightness modulation output according to the video signal VDO, but the marking switch When SW _M is turned on, a bright line is displayed on the display at that timing in response to the coincidence output D.

Preset command generated by timing circuit TC
PST is a frame synchronization signal that defines sectors A and B, and with this signal PST, the counter KA is set to "0".
However, the counter KB is also preset with (ji) from the subtraction circuit SUB. On the other hand, the clock signal CK generated by the timing circuit TC becomes a line simultaneous signal of the ultrasound beam, and this clock signal CK
Counters KA and KB count up at the same time each time . Therefore, when the count value of the counter KA is i, the count value of the counter KB is j-i+i, that is, j. Although not shown in FIG. 3, the ultrasonic beams A _i and B _j in _FIG.
and B _j-1 , A _i and B _j , A _i+1 and B _j+1 , . . . are scanned simultaneously. CRT not shown
The display is based on the output of the switch (multiplexer) SW ₃ , which receives the signal SLCT with twice the frequency of the clock CK and alternately passes the counts (numbers that specify the scanning lines) of the counters KA and KB. The display is similar to , that is, each ultrasonic beam is replaced with each electron beam. This means that the electron beam deflection circuit is previously set to A _i (i=0, 1, 2...
), and when the angle θ is input, it is rotated by the angle θ and outputs B _i (i=0, 1, 2………). You can easily achieve this by doing as follows.
If the CRT display is of the single electron gun type, the scanning speed of the electron beam should be twice that of the ultrasonic beam. Note that in terms of fan-shaped scanning, the ultrasonic beam side and the electron beam side are the same, so in the following explanation, the first
Each signal in the figure may be shared by the ultrasound beam and the electron beam.

When the count value of the counter KA reaches i, the comparator COMP sends the aforementioned control signal D to the brightness modulation circuit Z.
The beams A _i and B _j on the display are made to shine brightly during that period, that is, during one cycle of the clock CK. This allows the observer to know where A _i and B _j are, and switches SW1 and SW2.
By changing i and j according to , it is possible to simultaneously make the two beams of sector A and sector B intersect at any POI on the display. For example, operate the digital switch SW1 to determine i so that the brightly shining beam A _i crosses a POI, and then operate the digital switch SW2 so that the bright beam B _j crosses the same POI.

In the above explanation, two counters, KA and KB, were used, but it is also possible to use only one counter, KA, and use a circuit for calculating (value of KA) + (j-i) instead of counter KB. good. Also, the scanning line number is sequentially +1 (incremented)
However, by placing a code conversion circuit after the counter etc., it can also be applied to the case where scanning is performed in random order, and the desired beams A _i , B _j
By showing the beam as an emission line, it is easy to make multiple beams intersect at the same time at the POI. Furthermore, as shown in FIG. 4, if beams A _i and B _j coincide at point x, beams A _i-1 and B _j-1 become beam A _i at point y.
₊₁ and B _j+1 match at point z, and the locus of the POI can be found. In this way, the locus of this POI can also be displayed by performing calculations using the beam scanning line number and the compound angle θ as information.

As a method of specifying POI, here we use switch SW
1. A method is used in which the numbers of the scanning lines A _i and B _j are specified using SW2. (1) For example, a point on the screen is specified using a light pen, and multiple ultrasound waves are A method of specifying scanning line numbers within the device so that the beams intersect at the same time, and illuminating the entire display beam passing through the specified POI or only that POI portion. (2) For example, in the case of two-beam simultaneous scanning sector scanning. , for sector A and sector B
Set up switches SWA and SWB, and
As shown in the figure, when you want to specify a POI, among the display beams of sectors A and B, each (arbitrary) display beam A _i and B _j corresponding to the simultaneously emitted ultrasound beams is displayed brightly. For example,
While the SWB is closed, the brightly displayed display beam _Bj of sector B will automatically move sequentially at an appropriate speed, and when the SWB is opened at an appropriate location, the brightly displayed display beam Bj of sectors A and B will move automatically at an appropriate speed. A possible method is to use the intersection of two display beams as the POI. Furthermore, although the embodiment relates to a sector scan method, it is obvious that the present invention can also be applied to a linear scan method, and it goes without saying that the same idea can be developed to a simultaneous scan method using three or more beams.

By the way, in medical ultrasonic tomographic imaging apparatuses, the Doppler shift of the ultrasonic frequency is used to measure blood flow speed in the body, movement speed of heart valves, and the like. By the way, the problem with the compound method is the part that moves quickly, so using the above technology, the fastest moving part of the observation object is automatically detected as a POI, and the resolution of that part is determined as in the previous example. It is possible that this could be improved. FIG. 6 shows another embodiment of the present invention applied to an ultrasonic tomographic imaging apparatus having such an ultrasonic Doppler shift measuring means, and similarly to FIG. 3, an electronic sector scanning system using two beam simultaneous scanning is used. This is an example. However, to simplify the explanation, the deflection section, the vibrator vibrating section, etc. are omitted. XA and XB are ultrasonic transducers, and these are the origins O _A and O _B in Figure 1.
will be placed in The ultrasonic waves (reflected waves transmitted by the ultrasonic transducer) received by the transducers XA and XB are processed by two circuit blocks.
FIG. 7 shows the signal waveforms of various parts regarding XA. The operation shown in FIG. 6 will be explained below with reference to FIG.

The signal received by the transducer XA undergoes predetermined processing (delay addition, equalization, amplification, etc.) in the receiving circuit RA, and then is sent to the Doppler shift detection circuit DPA. The detection circuit DPA produces a larger output voltage as the Doppler shift becomes larger. The output of the detection circuit DPA when it receives the reflected waves of the ultrasonic beams A _l , A _l+1 , A _l+2 of the sector beam A shown in Fig. 1 is as shown in Fig. 1 b. Suppose that A _l in a of the same figure, A _l+1 ,
A _l+2 indicates the transmission and reception period of the ultrasonic beams A _l , A _l+1 , and A _l+2 . Figure c shows the peak value hold circuit PHA.
Assume that the output of the circuit holds a certain value (3 in the figure) before receiving the reflected wave of the beam A _l . Comparator COMP _A connects DPA output x
When the PHA output y becomes x>y, the transmission gate TGA is turned on, but since x<y between the scanning lines of A _l , the gate TGA is not turned on. Since x≧y in the scanning line period A _l+1 , the gate TGA is on during this period, and the output of the hold circuit PHA exhibits a value equal to the output of the detection circuit DPA. At the same time, while x>y, the value l+1 of the counter KA indicating the number of the scanning line is loaded into the latch LA. When the output of the detection circuit DPA starts to decrease, the output of the hold circuit PHA remains at the peak value 4 of the output of the detection circuit DPA, so x<
y, and l+1 is held in latch LA.
Since x<y always holds in the subsequent scanning line A _l+2 , neither the output of the hold circuit PHA nor the contents of the latch LA change. If the same operation is continued, the contents of the latch LA will hold the number of the scanning line (hereinafter referred to as i) in which the maximum Doppler shift exists among the sector beams.
The timing circuit TC provides a clock CK for changing the scanning line number to the counter KA, and also provides a control signal INIT for initializing the counter KA and the hold circuit PHA at the beginning of the frame. This control signal INIT causes the content of the counter KA to become "0", and the output voltage of the hold circuit PHA to be the initial value (for example, 1V).

The above operation is based on the series of ultrasonic transducer XTB,
In other words, receiver RB, Doppler shift detection circuit
The same applies to DPB, transmission gate TGB, peak value hold circuit PHB, comparator COMP _B , and latch LB. Let j be).

Therefore, in order to make the two beams intersect at the same time at the point POI where the Doppler shift is maximum in both sectors A and B, switch SW shown in Fig. 3 must be set.
1.Instead of SW2, use the latch shown in Figure 7.
It is sufficient to make LA and LB correspond and to preset the output ji of the subtraction circuit SUB into the counter KB at the timing when the counter KA is initialized to "0". The beam deflection circuit (not shown) receives the contents of the counter KA (referred to as m) as the scanning line number of the sector beam A, and the contents of the counter KB (n=m+j-) as the scanning line number of the sector beam B.
i) can be given.

In the circuit example shown in Fig. 6, sectors A and B include areas faster than the heart valves, etc. to be observed.
For example, if there is a blood vessel with a high blood flow velocity, that blood vessel can be set as POI.
There is a risk that it will be designated as FIG. 8 shows a third embodiment of the present invention, showing only the configuration to be added to the circuit of FIG. 6 in order to solve this problem. The circuits that need to be added are the comparator COMP′ _A and the AND gate AND _A for the transducer XA series (same for the XB side), and the output of the receiver RA is connected to the comparator COMP′ _A.
It is constantly compared with an appropriate reference voltage V _rA . The comparator COMP′ _A opens the AND gate AND _A only when (RA output) ≧ V _rA .
Pass the output of COMP _A. Therefore, if the intensity of the reflected wave is below the level specified by V _rA , the sixth
No matter how large the output of the Doppler detection circuit DPA shown in the figure is, no change occurs in the hold circuit PHA and latch LA. If we limit the observation range of Doppler shift based on the absolute level of the reflected wave,
Even if the velocity of blood flow in a blood vessel is greater than the velocity of a moving heart valve, the valve can be reliably designated as a POI.

Also, the speed of a moving object may differ depending on the viewing angle. For example, if the central part of a membrane whose periphery is suppressed moves in a round direction, a large Doppler shift will occur in the direction perpendicular to the membrane, and the detection output will be large, but the Doppler shift will be large in the direction parallel to the membrane. Not much deviation occurs and the detection output is small. In such a case, the ultrasound beams A _i , B _i (i=0, 1,
The high-speed moving objects detected by 2......) may not be the same object. In such a case, it is preferable to set one of the ultrasonic beams A _i and B _i so that the high-speed object is detected, and the other ultrasonic beam to simultaneously scan the high-speed object using the method explained in FIG.

As described above, according to the present invention, a plurality of beams passing through any one point in the overlapping area of the tomographic field of view formed by each beam can be simultaneously intersected in a multi-beam simultaneous scanning type ultrasonic tomographic imaging apparatus. Therefore, it is possible to take full advantage of the advantage of the compound method in which the same image is simultaneously scanned from multiple directions, and to increase the resolution of the observation target region.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the scanning principle of a sector scan type two-beam simultaneous scanning tomographic imaging device, Fig. 2 a and b are partially enlarged views of Fig. 1, and Fig. 3 shows an embodiment of the present invention. 4 and 5 are explanatory diagrams of a modification of FIG. 3, FIG. 6 is a block diagram showing another embodiment of the present invention, and FIG. 7 is a signal waveform diagram of each part of FIG. 6. FIG. 8 is a main part block diagram showing a different embodiment of the present invention. In the figure, A and B are tomographic fields of view, A _i and B _i are ultrasound beams, POI is the observation target, XA and XB are ultrasound transceivers, Z is the brightness modulation circuit, and TGA, PHA, and COMP _A are maximum value detection It is a circuit.

Claims (1)

[Claims] 1. Multi-beam scanning type ultrasound imaging in which at least two ultrasonic transducers that scan a predetermined tomographic field of view with ultrasonic beams are arranged so that a part of each tomographic field of view overlaps. In the apparatus, the ultrasonic transmission timing of each ultrasonic transducer is adjusted so that the ultrasonic beams from each ultrasonic transducer synchronously intersect at any observation target site within the overlapping area of the tomographic field of view. 1. A multi-beam synchronous scanning ultrasonic tomography apparatus, characterized in that it is equipped with an adjusting means for adjusting the angle of the image. 2. A brightness control circuit is added to a display device that receives the scanning output of an ultrasonic beam and displays an image by performing the same scanning as the ultrasonic beam with an electron beam. A multi-beam synchronous scanning ultrasonic tomography apparatus according to claim 1, characterized in that: 3. The multi-beam synchronous scanning ultrasonic tomographic imaging apparatus according to claim 1 or 2, characterized in that it has a Doppler shift detection means, and the maximum point of the Doppler shift is set as a beam intersection point. 4 Claims characterized in that the beam intersection point is the maximum point of the Doppler shift in a region where the reflected wave intensity is at a certain level or above, which includes a reflected wave intensity detection means in addition to the Doppler shift detection means. 3. The multi-beam synchronous scanning ultrasonic tomography apparatus according to 3.