JPH0215027B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an ultrasonic tomographic imaging device, and in particular, a device having a plurality of ultrasonic transducers in the same probe and mechanically rotating the transducers. The present invention also relates to a code conversion circuit for using an electronic circuit to compensate for low mechanical precision in mounting a transducer in an apparatus that obtains tomographic images by changing the transmission and reception direction of an ultrasonic beam by swinging the transducer.

[Prior art to the invention]

Conventionally, as an example of incorporating a plurality of transducers into the same probe, for example, as shown in FIG. There is one in which two oscillators A and B are arranged in parallel. When these transducers are rotated to change the direction of ultrasonic transmission and reception as shown in Figure 1b, and the direction of the display scanning line on the display is changed in accordance with the direction of transmission and reception, a fan-shaped display as shown in Figure 1c is created. A scan line is obtained. At this time, the direction of ultrasonic beam transmission and reception is determined by attaching a rotary encoder 2 to the rotating shaft 1, which has slots S1 arranged at equal intervals on the circumference and slots S2 indicating the reference position, as shown in FIG. 1d, for example. By operating the counter using the output of the optical slot detection circuit that generates a pulse for each slot as the clock,
It can be obtained as a counter value. It goes without saying that this counter may be initialized to a specific value each time the rotary encoder rotates once, using the output of the reference position slot detection circuit.
The present invention will be described in detail below, taking as an example a mechanical rotary probe using a rotary encoder type position detection mechanism shown in FIG.

Assume now that two vibrators A and B are mechanically accurately mounted around a rotating shaft as shown in FIG. 2a. At this time, for example, if there are targets T1 and T2 lined up on a straight line passing through the center of rotation as shown in the same figure, the tomographic images produced by transducers A or B will be as shown in Figure 2 b or c, respectively, and these two Even if tomographic images are superimposed, the target image will not shift.

On the other hand, as shown in Figure 3a, for example, if we consider a case where transducer A is correctly attached but transducer B is attached at an incorrect angle, the tomographic image produced by transducer A is The correct result is obtained as shown in Figure b. However, as shown in Figure 3c, the image produced by transducer B is based on the display scanning line number (i in the figure) obtained from the encoder output and the actual ultrasound beam transmission/reception direction (display scanning line number). A deviation (ΔN when converted to a scanning line number) occurs between i−ΔN). As a result, the image that should actually be displayed in the direction of the broken line in FIG. 3c is displayed in the direction of the solid line. Figures d and e also show similar examples when the rotation angle changes; in the end, the image produced by transducer B becomes as shown in figure f, and the target is △ from the display scanning line that should be displayed.
The image is displayed on display scanning lines shifted by N lines. Therefore, when the images from oscillators A and B are superimposed,
As shown in Figure 3g, the target will appear double.

Although this problem can be solved by sufficiently improving the mechanical precision when attaching the vibrator, it may be difficult to do so due to the cost.

[Purpose of the invention]

The code conversion circuit according to the present invention solves the problem when using the two oscillators A and B described above, for example.
No modification is made to the display scanning line number of A, but the value obtained by subtracting △N from the value output from the encoder pulse count circuit is used as the display scanning line number of B. The image in Fig. 3 f is corrected as shown in Fig. 3 h, so that even if it is superimposed on the image of the vibrator A as shown in Fig. 3 B, it will not appear double.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to FIG.

In FIG. 4, the counter 4 is initialized (for example, set to 0) by an initialization pulse obtained by shaping the reference slot pulse of the rotary encoder 2, and then initializing the pulse P2 by shaping the circumferential slot pulse of the rotary encoder. is used as the clock to generate the display scanning line number M' before correction.

The scanning line number determination circuit 5 calculates, from the counter value,
Determine which of the two transducers A and B in FIG. 3a is used for transmitting and receiving the ultrasound beam,
A judgment output S is generated. The signal S becomes a selection input to the data selector 6, and selects either OFFSET A or OFFSET B of the offset amounts specified by SWA and SWB.

Taking the case of Figure 3 as an example, the correction amount OFFSET A for oscillator A is the correction amount for 0 oscillator B.
OFFSET B is -ΔN. Data selector 6
The modified output ΔM selected in is sent to the adder 9,
It is added to the scanning line number M' before correction to obtain the display scanning line number M'=M'+ΔN after correction. △N, that is, the value of the offset amount is SWA in Fig. 4,
It is determined by determining the SWB settings so that the image shift is minimized.

In addition, in the case of the method described above, for example, Fig. 3 e
If we consider the case of , as shown in Figure 5, if we use K-△N instead of K as the display scanning line number, the direction of the display scanning line will be expressed correctly, but the direction of the display scanning line will be The starting point moves to Q instead of the starting point P of the actual ultrasound beam (broken line in Figure 5).

As a result, as shown in FIG. 5, there is an error of ΔX in the horizontal direction and ΔY in the vertical direction with respect to the position where it should originally be displayed. In other words, although the direction of the display scanning line is corrected, the position will include an error. When △N is small, this error is negligible, but when △N becomes large,
Display scan line starting point correction information must be generated for each scan line and sent to the deflection signal generator. FIG. 6 shows a configuration diagram at this time. Numbers 2 to 9 in FIG. 6 represent the same items as the corresponding numbers in FIG. 6th
In the figure, a code converter 10 is added. ΔX and ΔY in FIG. 5 depend on both the value M' of the display scanning line number and the correction amount ΔM by the encoder. The code converter 10 shown in FIG. 6 is for generating ΔX and ΔY from M' and ΔM, and is realized using, for example, ROM or PLA. M,
ΔX and ΔY are sent to a deflection signal generation circuit (in the case of an XY display) or sent to a coordinate calculation circuit and used to calculate a memory address (in the case of a TV system).

In the explanation of Fig. 3, it is assumed that transducer A is mechanically installed correctly, but as shown in Fig. 7a, the mounting angles of transducers A and B are converted into display scanning line numbers. It is clear that if the display scanning line numbers of transducers A and B are shifted by △N _A and △N _B , respectively, then it is sufficient to give an offset amount of -△N _A and -△N _B , respectively, but △N _A , △N _B
For example, if the image by transducer A is used as a reference, the display scanning line number of transducer B is -(△N _B -
It goes without saying that if the image is displayed as shown in FIG. 7d with an offset of ΔN _A ), it will almost overlap with the image obtained by the vibrator A shown in FIG. 7b.

If this method is used, the image will no longer appear double, but the image will be displayed in a position that is shifted from the position where it should be displayed as a whole. If this is inconvenient, after giving only the offset amount (in the case of Figure 7 - (△N _B - △N _A ) to the above-mentioned oscillator B, give the same amount ( In the case of Fig. 7, it is sufficient to give an offset amount of −△N _A ).The configuration when this method is used is shown in Fig. 8. In Fig. 8, 2 to 9 are the same as those with the same numbers in Fig. 4. Since we are considering the case where the transducer A is the standard, the switch 7 in FIG. 4 is removed and a constant offset amount (0) is given to the transducer A.9 If the output of is used as the display scanning line number as it is, an image obtained by superimposing images b and d in FIG.
This is for creating ΔN _A , and by adding this and the output of adder 9 in adder 12, an image as shown in FIG. 7e is obtained.

The advantages of setting the offset amount in two stages in this way are as follows.

First, it is only necessary that the images produced by the plurality of vibrators overlap without deviation. In this case, fewer adjustments are required than when offsets are given to all the vibrators individually so that they are displayed in their original positions. Second, after the images of one and all the transducers are superimposed, the offset of the scanning line number relative to the entire image can be adjusted by adjusting only one location.

Although the above explanation was given only for the case where two transducers are included in one probe, the case where three or more transducers are included in one probe is also explained as shown in Fig. 4. The output from the scanning line number determination circuit 5 is set to 2 bits or more, the offset amount setting SW is further added from the two 7 and 8, and the data selector 6
It is clear that this can be easily achieved by increasing the number of input ports.

Also, the above explanation was given only for the case where a rotary encoder is used as a position detection mechanism, but it is also possible to detect an angle using a potentiometer or convert rotational motion into linear motion and then use a differential transformer. It can also be applied to cases where position detection is performed by detecting an angle. In these cases, the detected angle signal (analog) is
When performing D conversion, in the configuration shown in FIG. 4, instead of the output of the counter 4, the output of the A/D converter or the output obtained by appropriately converting the code and converting the output into a display scanning line number may be used. When processing the analog signal as it is, use the output of a potentiometer or differential transformer in place of the counter 4, a voltage comparator and appropriate comparison voltage source in place of the transducer number determination judgment circuit 5, and the data selector 6. Use an analog multiplexer instead, switches 7 and 8
A variable voltage source may be provided in place of the digital adder 9, and an analog adder may be provided in place of the digital adder 9.

〔Effect of the invention〕

As described above, according to the present invention, when it is difficult to obtain a certain level of mechanical accuracy when incorporating a plurality of transducers into one probe,
Lack of mechanical precision can be remedied inexpensively using a circuit.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams explaining the operation of a general probe.
FIG. 3 is an explanatory diagram of the operation of an embodiment of the present invention, FIG. 4 is a block diagram of an embodiment of the invention, and FIGS. 5 and 6 are explanatory diagrams of the operation of a second embodiment of the invention, respectively. FIGS. 7 and 8 are an operational explanatory diagram and a block diagram, respectively, of a third embodiment of the present invention.

Claims (1)

[Claims] 1 Transmitting and receiving ultrasonic waves while mechanically rotating or swinging a plurality of ultrasonic transducers within a single probe,
In an ultrasonic tomographic imaging device that displays tomographic images on a display by brightness modulation or color modulation, a mechanical or optical encoder or a mechanical or optical encoder or In an ultrasonic tomography apparatus that detects by a mechanical position detection mechanism such as a differential transformer or a potentiometer and determines the position or direction of a display scanning line, or both, directly from the output of the mechanical position detection mechanism. Information regarding the position and/or direction of the display scanning line for each vibrator is obtained by adding an arbitrary offset amount independently for each vibrator to the information regarding the position and/or direction of each vibrator obtained in the above process. A code conversion circuit for an ultrasonic tomographic imaging device, which is characterized by correcting. 2. If a mechanical error in the mounting accuracy of multiple ultrasonic transducers causes a deviation in tomographic images obtained by different transducers, the offset amount described in paragraph 1 shall be To determine the position and/or direction of the display scanning line of a transducer other than the transducer based on the amount of offset such that the tomographic image produced by another transducer exactly overlaps the reference tomographic image using the image as a reference. A code conversion circuit for an ultrasonic tomographic imaging apparatus according to claim 1, characterized in that: 3. If the vibrator itself, which is based on the above standard, includes a mechanical error in its installation, the amount of offset that should be added to the display scanning line number in order to correct the mechanical error is
3. The code conversion circuit for an ultrasonic tomographic imaging apparatus according to claim 2, wherein the code conversion circuit applies the same voltage to all the transducers in the probe.