JPS6232004Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This idea relates to an improvement in an ultrasonic tomography device that can send ultrasonic pulses inside a living body and use the time delay of the reflected waves to observe tomographic images of internal organs, especially the heart and abdomen, and their dynamics. . Ultrasonic tomography equipment has no radiation damage compared to computer cross-sectional imaging equipment that uses X-rays, etc.
It is also said to be highly safe and provide a lot of information for its low price, and is widely used for its ability to obtain real-time tomographic images, especially for diagnosis of the heart and abdominal circulatory system, as well as observation of fetal dynamics. ing. This device produces 2~
A so-called pulse in which the same piezoelectric element receives echoes of 3MHz ultrasonic pulses that return from the interface between two substances due to impedance mismatch due to the different acoustic impedances (density x speed of sound) unique to each organ in the living body. This is a device version of the B-mode diagnostic method, which is one of the reflection methods. In this B mode, a thin ultrasonic beam emitted from a probe detects the echoes returned from each interface of each organ of the living body using the same probe, and the intensity of the echoes is measured using an oscilloscope (hereinafter referred to as a CRT). By applying so-called luminance modulation, which changes the brightness and darkness of the emission line of the
Display on the scanning line. Next, move the probe and
The ultrasound pulse is emitted again, the echo is received, and its position is displayed on another scan line of the oscilloscope. Repeating this, the vertical axis is the depth and the horizontal axis is the width, and the connection of scanning spots of different brightness and darkness on the scanning line forms a tomographic image. The movement of the probe is essentially to mechanically or electronically move or scan the direction of the ultrasonic beam itself at high speed in order to correspond to the fast movements of a living body, particularly the heart. This beam scanning method is classified into linear scanning in which the beam is shifted in parallel, sector scanning in which the beam is shifted in a fan shape around one point, and also depending on whether these scannings are performed mechanically or electronically. Among them, the most popular and developed type is the electronic sector scanning type, which uses beams of 1/30 to 1/3
This method involves swinging an angle of about 70 to 80 degrees in a short period of 20 seconds, and scanning every 0.6 to 0.7 degrees during that time. This type of device stops the deflection of the beam at an arbitrary angle, scans the echoes from each organ at fixed time intervals, and uses M mode to photograph the dynamics of the heart valves.
So-called Ultrasonic Cardiogram (UCG) can also be performed at the same time. However, when diagnosing a patient with this device capable of B-mode and M-mode tomography, if you want to enlarge the area of interest, that is, use the B-mode described above with a standard depth of field of 0.2 m, as shown in Figure 1. Suppose that a tomographic image 1 of a certain organ is displayed on the entire CRT screen 2. At this time, when the operator notices an abnormality in the area 1A above the center of the tomographic image 1 and wants to enlarge it and observe it in detail, the focal length of the ultrasound beam (depth of field)
Change the setting to 0.1m. This operation will cause the CRT
As shown in FIG. 1, the region of interest 1A is enlarged four times in area and displayed as 1A', filling the entire screen 2 of the screen. This is because the X-axis and Y-axis sweep speeds for displaying the position of the echo from the region of interest 1A on the scanning line of the CRT are doubled. However, doubling the sweep speed should correspond to the echo intensity.
The brightness of the CRT fluorescent surface is reduced by about half, and the tomographic image becomes dark and unclear. Therefore, the surgeon must operate the CRT's brightness controller each time to adjust the brightness of the image appropriately. This adjustment operation is not only troublesome for the surgeon, but also when the region of interest is a fast-moving organ, the state of the organ has often changed by the time the brightness is adjusted to an appropriate level. This makes diagnosis difficult, and recording camera film taken after adjustment is wasted, necessitating re-examination. In order to improve the diagnostic accuracy of the region of interest, the surgeon frequently changes the depth of field, but each time
If it is necessary to adjust the brightness of the CRT, the brightness will be uneven, and the exposure conditions must also be adjusted when shooting with the camera. Like this CRT
The brightness is manually adjusted as the depth of field changes, allowing you to observe the fast-moving circulatory system in real time with clear images.
This seriously impairs the feature of this device, which is to take pictures.
The current situation is a major obstacle to improving diagnostic efficiency. This idea was developed in view of the above-mentioned current situation. Regardless of the examination conditions such as B mode or M mode of the ultrasonic tomography device, the operator can change the depth of field of view for diagnosis, that is, the focal length of the ultrasonic beam. This is an improvement to the device that aims to improve diagnostic accuracy and efficiency by automating the means to suppress changes in the brightness of CRT tomographic images when the brightness changes and to maintain optimal and constant brightness at all times. That is, an ultrasonic pulse is emitted into the subject, and the intensity distribution of the reflected pulse is displayed on a cathode ray display tube to obtain a tomographic image of the subject. In an ultrasonic tomography apparatus that changes the screen sweep speed, the signal amplification factor of the reflected pulse signal is controlled in proportion to the screen sweep speed of the cathode ray display tube, which is changed in response to changes in the depth of field. The present invention relates to an ultrasonic tomography apparatus constructed as follows. DESCRIPTION OF THE PREFERRED EMBODIMENTS An ultrasonic tomography apparatus according to an embodiment of this invention will be explained in detail below with reference to the drawings. Figure 2 is a basic configuration block diagram of the embodiment device.
The pulse signal (Sp) from the clock pulse generator of block 5 in the array of individual transducers enters the transmission/reception controller, controls the transmitter and the delay time controller of the delay line of block 5, and drives each transducer. By controlling the timing of the drive voltage S _D , the ultrasonic beam B emitted by the probe is swung in a fan shape. This is an electronic sector scanning system, and linear scanning is also performed using this electronic control system. Next, the ultrasonic pulse (usually around 3 wavelengths) emitted into the living body is received as an echo E by the same transducer 3, and this electric signal S _E is sent to an amplifier via a receiver controlled by a reception controller. The amplified signal is input to the display controller 6. The configuration up to this point is the same as the conventional device, but the device of this invention is included in the area surrounded by the dotted line.
It is characterized by a CRT brightness automatic adjustment circuit 7. S _Z is a brightness modulation signal proportional to the intensity of the echo signal, and this S _Z is branched into two circuits at a branch point 8. 10 is an amplifier (or attenuator), 11 is a signal selection circuit generally called a multiplexer, which is made of a semiconductor, and selects its two input signals (0Z),
(1Z) and outputs to the output terminal (OUT). (+B) is a bias voltage of, for example, 5 VDC, R is a resistor, and 9 is a control switch for a signal selection circuit 11 that is interlocked with a field of view switch (not shown) of the apparatus. E is earth. An X/Y display (CRT) is an oscilloscope with three input terminals (X), (Y), and (Z), and the monitor surface is usually about 6 inches or 8 inches (diagonal size). This is a CRT that can be deflected in any direction by controlling its bright spot using horizontal (X-axis) and vertical (Y-axis) deflection voltages. The above is the configuration of this device, and its operation will be explained next. Figure 3 is an explanatory diagram of B-mode diagnosis. The figure is a pulse emission time chart of ultrasound beam B. (Ta) is the pulse interval, that is, a constant time determined by the field of view depth setting. Since the speed is 1500 m/s excluding bones, if the field of view depth L is 0.2 m, then Ta =
2L/1500 (sec) is 267μs. The figure shows the waveform of echo E, and the figure shows the scanning spot on the CRT screen synchronized with (S _{E )} in FIG. This is a CRT
This is the brightness modulation. The figure shows the waveform of the CRT's X-axis sweep (deflection) voltage _VX , which increases linearly from (t ₁ ) to (t ₂ ). Its inclination angle (θ') is proportional to the bright spot deflection speed, and (V _x ') is, for example, the scanning line (P ₀
−P ₂ ) is proportional to the deflection distance (X ₂ ). The figure shows the waveform of the Y-axis sweep voltage (V _Y ) of the CRT, which is also proportional to the deflection distance (Y ₂ ) in the figure. (V _X ″) and (V _Y ″) in the diagram are arrow A
As scanning is performed in the direction, the deflection distance of the (X) axis decreases over time, and that of the (Y) axis increases. Next, when the field of view depth L is set to 0.1 m, pulses are emitted from (t ₃ ) to (t ₄ ) as shown in (B'), and the pulse interval is halved and b =
It becomes 133μS. The echo signal E enters the CRT from (t ₁ ) to (t ₃ ). At this time, as shown in the figure
The sweep voltages _of the CRT are both ( _V This means that the speed has been doubled.For this reason, in the conventional device, as mentioned above, the size of the scanning spot shown in the figure is halved.This means that even though the strength of the electron flow from the CRT cathode is the same, it is difficult to reach the fluorescent surface. This is because the time it takes to create a bright spot is halved, and the only way to return it to its original size is to manually increase the voltage of the CRT's control grid.This invention improves on this point. Returning to Figure 2, when the field of view depth L is 0.2 m, the switch 9 is turned on and the voltage (+B) is grounded, so the control signal to the multiplexer 11 is (0), and the switch 9 is turned on and the voltage (+B) is grounded. The brightness signal (S _Z ) of the display controller 6 is output as is (0Z) by the selection action and inputted to the (Z) terminal of the CRT.This becomes the time chart of (Ta) in Fig. 3, and the brightness signal is modulated. A bright image is imaged as shown in the figure.Next, when the operator changes the field of view depth L to 0.1m, switch 9 in Figure 2 is turned OFF.
The voltage (+B) becomes signal 1, controls the multiplexer 11, selects its input (1Z), and outputs it to the output terminal (0). (1Z) input is S
Since _Z is amplified twice by 10 amplifiers,
Even if the CRT control grid voltage is left as is, the brightness signal will be the same as above (0Z), and the brightness of the image will not change. That is, by reducing the depth of field L, the CRT sweep speed is increased and the amplification factor of the CRT's luminance signal _SZ is increased. Block 10 is not limited to the above amplifier, but may also be an attenuator using a voltage divider or the like. When using an attenuator, adjust the gain so that the brightness is appropriate when the depth of field L is 0.1m, and when switching to a depth of field L of 0.2m, that is, if you want to cover a wide area of interest, reduce S _Z by 1/2. If the control signals 1 and 0 are exchanged so that the signal is attenuated, it operates on exactly the same principle as described above. In this way, the block 10 may be selected depending on the method of use of the device and other conditions. It goes without saying that voltage dividers are cheaper than amplifiers. Although the above explanation deals with two-stage switching of the field of view depth, it is easy to implement three or more stages of switching based on the same principle. Next, the operation during M mode diagnosis will be explained with reference to FIG. The figure shows the X-axis scanning time (T) for example.
The standard field of view depth L is 0.2m as above, and the case where this is changed to 0.1m will be described.
When L=0.2 m, if the scanning spot (I) of the CRT is, for example, a diagram, an image as shown in the diagram will be displayed on the CRT screen, and the scanning line interval (X) can be changed arbitrarily with a time setting device. As a result of this change, ( _V
510sec). The combination of this and the change in the inclination angle (θ') to (θ'') of (V _Y ') in the figure results in the second
The brightness signal (S _Z ) automatic adjustment circuit 7 shown in the figure is configured as shown in FIG.
Insert 10B and 10C, respectively. The selection control of the multiplexer 11 is performed by a control circuit (not shown).
By combining the signals from A and B as shown in the table below,

[Table] Regardless of the time axis (X-axis) sweep speed of the CRT, a constant brightness is maintained when the depth of field L is changed. The above is the M mode, that is, the above-mentioned CRT automatic brightness adjustment in UCG shooting, and the electronic sector scanning method was explained along with the B mode described above, but this invention also applies to the linear scanning method, as can be seen from the configuration in Figure 2. The same applies. Furthermore, the same applies to devices in which scanning is mechanical. This device is configured as described above, so it automatically adjusts the changes in brightness on the CRT monitor surface due to changes in the depth of field of interest in the region of interest during diagnosis using an ultrasound tomography device, and is always optimal. It provides clear tomographic images under constant exposure conditions, improves diagnostic accuracy through observation and recording, and eliminates the operator's need to manually adjust brightness, resulting in stable images.
This provides a device that is expected to improve diagnostic work efficiency.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of an ultrasound tomographic image according to the depth of field in B-mode diagnosis, Fig. 2 is a block diagram of the configuration of an ultrasound tomography apparatus according to an embodiment of this invention, and Fig. 3 is an embodiment of the apparatus. FIG. 4 is a time chart illustrating the operation during B-mode photography, FIG. 4 is a time chart illustrating the operation during M-mode photography, and FIG. 5 is a block diagram of another embodiment of the automatic brightness adjustment circuit shown in FIG. 2. 1... Organ tomographic image (B mode), 1A... Region of interest to be enlarged, 2... CRT monitor surface, 3...
Piezoelectric vibrator, B... Ultrasonic beam, E... Ultrasonic echo, Sp... Clock pulse signal, S _D ... Vibrator drive signal, S _E ... Echo signal, 5... Delay time control circuit, 7... ... CRT (cathode ray display tube) brightness automatic adjustment circuit, 9 ... ON/OFF switch linked with viewing depth setting device, 10 ... amplifier or attenuator, 11 ... signal selection circuit (multiplexer), S _Z ... Luminance signal (reflected pulse signal), 0or
1... Control signal, V _X ... X-axis sweep voltage of CRT,
V _Y ...Y-axis sweep voltage of CRT, L...Ultrasonic focal length (depth of field) (m), _P0 ...Probe position in B mode, Ta...compatible with field of view depth of 0.2m Time, Tb…
...Time corresponding to field of view depth 0.1m (Ta/2), θ',
θ″...Increasing slope angle of sweep voltage (proportional to sweep speed), t...Time, T...M mode observation setting time (sec), I...CRT scanning spot (bright spot), 1
0A, 10B, 10C...Amplifier or attenuator.

Claims (1)

[Scope of utility model registration request] Ultrasonic pulses are emitted into the subject, and the intensity distribution of the reflected pulses is displayed on a cathode ray display tube to obtain a tomographic image of the subject. When changing the depth of field, the cathode ray display tube In the ultrasonic tomography apparatus, the signal amplification factor of the reflected pulse is controlled in proportion to the screen sweep speed of the cathode ray display tube, which is changed in response to changes in the depth of field. An ultrasonic tomography apparatus characterized in that: