JPS5922076A - Ultrasonic holography device - Google Patents

Abstract

PURPOSE:To obtain a tomographic image of a living body with invariable excellent resolution regardless of distance, by storing pieces of picture information differing in depth and performing convolution processing on the basis of a reference signal. CONSTITUTION:L units of vibrators 1-1-1-N are selected by switches 2-1-2-N and their receive signals are multiplied by the signal of an oscillator 3 and a signal obtained by shifting 11 the signal of the oscillator 3 by pi/2 in mixers 4-1 and 4-2. The outputs of the mixers are stored 8-1 and 8-2 through sample holding circuits 6-1 and 6-2 and A/D converters 7-1 and 7-2. Those stored values are supplied to a signal processing circuit 9 to put the pieces of information differing in depth together properly and the convolution calculation based on the reference signal in a storage 16 is performed. The result is supplied to a monitor 15 and an X-ray film 17 through a frame 14.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an ultrasonic diagnostic apparatus that obtains a tomographic image of a living body using ultrasonic waves. The present invention relates to an ultrasonic device that can obtain image quality with excellent resolution. .

[Technical background of the invention and its problems]

Ultrasonic testing, in which ultrasound pulses are emitted into the body and information about the body is obtained from the signals reflected from the boundaries of tissues with different acoustic characteristics, can be performed non-invasively, so It doesn't cause any pain. Furthermore, compared to X-ray examinations, it has the advantage of causing fewer radiation exposure injuries and being able to obtain tomographic images of soft tissue without using a contrast agent, and has become rapidly popular in recent years.

In conventional devices, the ultrasound beam must be focused to obtain images with good resolution. In this case, in the array type ultrasonic probe used in the electronic scanning device, beam focusing in the array direction is performed electronically, and in a direction perpendicular to this, an acoustic lens is used. However, in these methods, the focused ultrasound is limited to the vicinity of the focal point,
Good images could only be obtained in this area.

[Purpose of the invention]

The present invention has been made in view of these problems, and an object of the present invention is to provide an ultrasonic diagnostic apparatus in which the resolution of tomographic images does not depend on distance (depth) and good images can always be obtained. 1. [Paper packaging of the invention] The present invention is an application of the aperture synthesis method used in the radar field to an ultrasonic device, and the principle thereof is shown in FIG. A predetermined portion of the arrayed ultrasonic transducers is selected by an electronic switch and transmits and receives ultrasonic waves in the Z-axis direction.

Now, a reflective object (reflection coefficient is γ) is placed at point Pn (Xn, Zn).
1), then m′ of the array transducer
The signal (Sr) radiated from the th (Xm' + 0), radiated at Pn, and received again by the transducer is Sr if the transmitted wave (St) is f(t) m wot.
= r(1((t −tn) sin(2πfo(t −t
n)) ...(11. However, fo: Ultrasonic frequency r(t): Transmission pulse envelope ■: Ultrasonic velocity in the medium The received signal is a reference signal approximately equal to the ultrasonic frequency fO Synchronous detection is performed using sin wot and cas wot, and a high frequency component (2fo) is further removed by a filter.

In other words, the signal (S) at this time is becomes.

Convolution is performed between Pn and an image of Pn is constructed on the SZ plane.

Figure 2 shows one target at position W'-”n(Xn Zn
) is a hologram obtained when In the pulse reflection method using ultrasonic waves, the pulse width is around 1 mm (1.5 nm).
It is desirable that the convolution (correlation) process between the sec) and the extremely thin reference signal be performed along the broken line in the figure. That is, in this case, the output when the correlation is taken along the broken line (b) centered on (Xn Zn,) is the largest. However, if such a processing method is used when the transducer makes one stop at a cross section of a certain depth, such as in C-mode image display, a large amount of memory is required not only in the x+Y direction but also in the Z direction. Become. .

In addition, in FIG. 2, the shaded area indicates negative polarity.

The present invention has been carried out for the purpose of obtaining substantially the same performance (resolution) with a smaller memory capacity in the case of C mode display, for example.

Figure 3 shows the case where the signals used for processing are extracted linearly (in the direction of the arrow) from the hologram, but since the hologram is hyperbolic, even if the beam width emitted from each transducer element is large, However, the amount of data extracted for processing is limited and therefore good resolution cannot be obtained.

〔Effect of the invention〕

FIG. 4 is a detailed explanation of the present invention. For example, two images with different depths are stored in the memory,
These are direct kOB centered around (Xn + Zn)
Convolution is performed along OCn.

However, before convolution, the data of An Cn is converted to Bn
Addition is added at both ends.

FIGS. 5(a) and 5(b) show the hologram amplitudes at Bn and 8000, and FIG. 5(C) shows the hologram amplitudes after addition.

As shown in Figure 5, the synthesized hologram (C) is the second
It is possible to create a hologram amplitude approximately equivalent to that obtained along the hyperbola shown in the figure, and therefore, by performing convolution using this composite hologram, resolution can be improved.

Figures 5(a) and 5(b) show reconstructed patterns obtained by the method in Figure 3, and Figure 5(C) shows reconstructed patterns obtained by a composite hologram, in which the beam width is reduced by 50%. It is possible to make it thinner.

As in the present invention, by discretely recording a plurality of hologram data at a certain distance from the transducer, adding and synthesizing these data, and then convolving them with the reference signal, the memory capacity can be reduced from 115 to 1000 yen. It is possible to reduce it.

[Embodiments of the invention]

FIG. 7 shows an embodiment of the present invention.

Of the N vibrators (1) arranged, first (1-1) to (
L pieces of 1-L) are electronic switches (2-1) to (2-N)
selected by The received signal at this time is sent to two mixers (4-1) and (4-2), and multiplied with the signal from the oscillator (3). In this case, the signal of the oscillator (3) is sent directly to the mixer (4-1) and also to the mixer (4-2).
) is sent after being phase shifted by 72 by a phase shifter Ql).The output of the mixer is passed through a low-pass filter (5-1).
After the high side wave component (near 2ro) is removed in ~(5-2), the Zumble hold circuit (6-1), (
6-2), analog-to-digital converter (7-1), (7
-2) through the storage circuit (8-1).

(8-2).

Next, the transducer selects each of (1-1) to (1-L) when transmitting, and each of (1-2) to (1-LH) when receiving, and the signals obtained at this time are the same as above. The data is stored in the memory circuits (8-1) and (8-2) through the process of.

Thereafter, similar operations are repeated until vibrators 1-(N-L+1) to 1-H are selected.

The received signal stored as a digital value is processed by a signal processing circuit (9
), after appropriately adding and synthesizing the information with different depths as described above, convolution calculation is performed with the reference signal Sc stored in advance in the memory circuit (161), and the result is temporarily stored in the frame memo IJH. After being stored, it is displayed on a monitor (15) or recorded on an X-ray film α1 or the like.

[Brief explanation of drawings]

Figure 1 is a diagram showing the principle of the aperture synthesis method, Figure 2 is a diagram showing a general method of convolution processing, Figure 3 is a diagram showing the conventional C-mode convolution method, Figures 4 and FIG. 5 is a diagram for explaining the principle of the convolution method of the present invention, FIG. 6 is a diagram showing simulation results according to the present invention, and FIG. 7 is a block diagram of one embodiment of the present invention. 1-1~1-N... Ultrasonic transducer 2-1~2
-N... Electronic switch 3... Oscillator
4-1.4-2...Mixer 6-1.6-2...
...Sample hold circuit 7-1.7-2...
・・Analog-digital converter 8-1.8-2・・・・
...Memory circuit 9...Signal processing circuit 1
1... Phase shifter 14... Frame memory 15... Monitor 16...
・Memory circuit TL 17...X-ray film agent Patent attorney Nori Chika Kensuke (and 1 other person) Figure 2 Figure 3 Figure 5 Figure 6 Figure 6 2a 1lfi Gogumon

Claims (1)

[Claims] An electroacoustic transducer consisting of one or more electroacoustic transducers, means for mechanically moving or electronically switching the electroacoustic transducers, and an oscillator having one frequency substantially equal to the resonant frequency of the electroacoustic transducer. , comprising means for performing phase detection between the signal obtained by the electroacoustic transducer and the output of the oscillator, means for performing convolution processing on the detected output, and means for displaying or recording the result, The ultrasonic holography apparatus is characterized in that the signal used for the convolution is once synthesized by adding the detected output according to a predetermined rule.