JPH01276063A - Orthography display method by ultrasonic return circuit transmission method and orthography device for performing method concerned - Google Patents

Abstract

PURPOSE:To govern a two-dimensional scan by only the time for reconstituting received data and to shorten the time required by executing a simultaneous irradiation without executing the focusing at the time of transmission and making a screen by data which has been obtained substantially from the whole surface of an object area at the time of reception. CONSTITUTION:In a two-dimensional transducer 1 of an orthography device, long pulses of no-focus are transmitted simultaneously at an irradiation angle for covering all of desired solid angles at the time of transmission, and scanned and received by adjusting a focus to an object area 2 at the time of reception. By an echo generating part 4 which has been placed in the rear of this object area 2, a transmitting ultrasonic wave is reflected, passes through the object area 2 again and made incident on the transducer 1. A space 3 of this device takes a long distance to some extent since a view angle is limited in order to make an orthogonal projection image. At the time point when a reflected wave returns from the generating part 4, a hologram is derived in the transducer 1, therefore, a two-dimensional scan is governed by only the time for reconstituting received data, the time required can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an orthographic display method using an ultrasonic transmission method and an apparatus therefor for analyzing and displaying data from ultrasonic waves transmitted through a target area.

(Prior art) The transmission orthographic display method is a method of displaying an image by analyzing signals that come from behind the target object and passing through the target object, rather than receiving reflected waves from the target object. . Conventionally, the mainstream of transmission orthography has been to transmit waves from the other side of the target object. There are methods to do this, such as the water immersion method and the ice bag method on both sides, but the equipment is large and difficult to handle, so no conflicts have been achieved.

Instead, like a B-mode imager using the normal reflection method, the target area is focused while being accessed through a single large aperture, and the signal is received at a time when reflected waves from behind the target area are received. Transmission orthography was developed.

This scans a two-dimensional plane of θ, φ or x, v and displays an image using the data. In other words, the reflected wave from the rear becomes image information including attenuation in the target area on the outward and return trips, and information on the target area is extracted by focusing on the target area. Here, since the reflected wave source at the rear is out of the focal plane of the array transducer, the image of the reflecting object is so-called out of focus in terms of image data, and although this results in shading on the image display, it is difficult to see the target object. It does not interfere with the image display. Further, such shading can be reduced by lengthening the section in which reflected waves are captured.

(Problem to be Solved by the Invention) However, in the transmission method described above, since both transmission and reception are focused in two dimensions, it is necessary to scan in two dimensions to obtain image data. Even if one dimension can be done in about 1/30 seconds using a regular mechanical sector scan II or a phased array, the other dimension is about 100 times longer and takes several seconds to more than 10 seconds. , can't be faster.

The present invention has been made in view of the above points, and its purpose is to realize an orthographic display method and apparatus using an ultrasonic return transmission method, which can shorten the acquisition time of image data and make it real-time. It is in.

(Means for solving the problem) 1 above! The present invention solves the problem by transmitting ultrasound signals from a two-dimensional array transducer to fill the entire field of view of a target object in an orthography display method using the return transmission method in which ultrasound is transmitted and received from the same direction to obtain an orthography image. The waves are transmitted without focusing all at once, transmitted through the target area and reflected from the echo generating part behind the target area, and received while being scanned by the array transducer focused on the target area. The present invention is characterized in that the image is reconstructed based on information on attenuation caused by transmission through the target area.

(Function) When transmitting waves, the beam is irradiated all at once without focusing, and when receiving waves, an image is essentially created from data obtained from the entire surface of the target area, so two-dimensional scanning reconstructs the received wave data. The time required is reduced because it is governed only by time and not by the time it takes to essentially repeat each scan.

(Example) Embodiments of the method of the present invention will be described below with reference to the drawings.

Figure 1 is an explanatory diagram of one embodiment of the method of the present invention. In the figure, 1 is a non-focal long pulse that is emitted at an illumination angle that roughly covers the entire desired angle of view (solid angle) during wave transmission. It is a two-dimensional array transducer that transmits waves all at once and scans and receives waves while focusing on a target area 2 when receiving waves, and a space 3 that is long enough to obtain an orthogonal projection image is provided. 4 is an echo generating part for reflecting the transmitted ultrasonic waves from the two-dimensional array transducer 1 located behind the target area 2, and it is designed to have a hazy feel so as not to produce a clear reflected wave of an image. desirable.

Next, a method of creating an orthogonal projection image obtained by ultrasonic waves transmitted and received in the arrangement as described above will be explained. The two-dimensional array transducer 1 covers the entire field of view.
For example, a long pulse of about 30 to 50 μS at 2 MHz is transmitted toward the target area 2 . The transmitted ultrasonic wave passes through the target area 2, is reflected by the echo generator 4, passes through the target area 2 again, and reaches the two-dimensional array transducer 1. Sky@3 has a limited angle of view to create an orthogonal projection image, so the distance is as long as possible.

A hologram is obtained in the two-dimensional array transducer 1 at the time when the reflected wave returns from the echo generator 4. Since the pulse width is long, it can be considered as a CW mode, and the received data becomes one piece of complex data for each element of the two-dimensional array transducer 1. To be more specific, the echoes from the echo generator 4 are sent to the target area 2 in a way that matches the interval width and sending timing of the transmitted long pulse.
Coherent detection is performed on the data for each element, and the data separated into in-phase and quadrature components is integrated separately to obtain the complex complex of the element. The received wave data is collected and the data of all elements are collected to form a complex hologram. Store this data in your computer's memory.

Based on this two-dimensional hologram, using the Fresnel approximation method or Kirchhoff's exact solution method, the propagation length to the target region 2 is determined while specifying the relevant aperture internal partial region each time if necessary, and the propagation term is solved. Complex data of the target area 2 is obtained by a wavefront backpropagation algorithm. This part of the calculation is basically an inverse Fresnel transform, and can be implemented by adding a phase correction term to the inverse Fourier transform, as is known. The SN ratio can be improved by collecting the holograms for several transmissions and averaging them for each element of the two-dimensional array transducer 1. Conversely, if you perform the process of extracting changes in the time axis direction, IMT
I (Moving Object Indication) system.

The timing of wave transmission and reception is illustrated in FIG. 2.

In the figure, (a) is the timing of wave transmission, and 5 is the 2MH
This is the time during which the ultrasonic signal of z is transmitted as a long pulse with a pulse width of 50 μs.

(b) is the wave reception timing, and during wave transmission m5, wave reception is biased to a prohibited state. Once the wave transmission ends, wave reception starts. 6 is the time width of the inspection section in which the target area 2 is passed back and forth. Substantially, the round trip to the echo generator 4 is also included, but it is shorter than the pulse width.

FIG. 3 is a block diagram of an embodiment showing only the receiving section of a device implementing the above method. The wave transmitting part transmits waves simultaneously from all elements and is no different from a normal device, so only the wave receiving part for one channel is shown.

In the figure, a signal received by an array transducer 1 is amplified by an amplifier 11. 12 is a range gate for extracting only the data of the target area 2; 13 is a range gate for coherently detecting the output data of the range gate 12 and detecting the in-phase signal i.
This is a detector that outputs a q signal that is orthogonal to the signal. 14
is a RAM 15 that stores complex holograms, and a digital signal processor (hereinafter referred to as DS) that performs inverse Fourier transform operations.
(referred to as P)16. It is an image reconstruction arithmetic device consisting of a FROM 17 that stores software such as instructions related to arithmetic processing of the DSP 16, and a RAM 18 that stores data of arithmetic results. A digital scan converter (hereinafter referred to as DSC) 19 converts the input signal into a television format, and displays the converted data on the TV 20.

The operation of the device configured as above will be explained.

Reflected wave signals received based on the transmitted wave signals emitted all at once from the array transducer 1 are amplified by the amplifier 11. The range gate 12 passes data in a time period corresponding to the distance from the time of transmission when the wave is reflected by the echo generator 4 and transmitted through the target area 2. The data passing through the range gate 12 is coherently detected in the detector 13 and outputs a complex signal separated into a 1 signal and a q signal, which is sent to an image reconstruction device! 114, first the RAM 15
is stored in The data stored in the RAM 15 is a complex hologram of all elements. This two-dimensional hologram is subjected to the image reconstruction calculation described in the above method by the DSP 16 based on instructions from the FROMI 7, and the resulting data is stored in the RAM 18. The data stored in the RAM 18 is read out sequentially, and T
It is converted into V image data and displayed as TM01.

As described above, when transmitting waves, the entire field of view is irradiated at the same time, and when receiving waves, it is scanned only, so that an orthogonal projection image can be obtained by the return transmission method in a short time, and stones and stones inside the subject can be It can be used in a similar manner to X-ray photography to detect other foreign bodies or fractures.

Note that the present invention is not limited to the above embodiments.

(+>If a range gate is provided at the time of the echo from the target area 2, an image of normal reflection source intensity can be obtained, and reflection method orthography can be realized.

(ii) Array transducer elements are 64X
In 64, the number of elements is huge and the number of channels is 3.
000 to 4,000, but it is fully feasible if the method described in Japanese Patent Application No. 61-203460 "Ultrasonic Holography Apparatus" previously filed by the present inventor is used.

(iii) FIG. 4 is a diagram of a two-dimensional array transducer in which transmitting and receiving elements are separated. In the figure, 21
2 is a convex disk transducer dedicated to transmitting waves, and 22 is a mosaic array transducer dedicated to receiving waves. Figure (a) shows a rectangular transducer, and figure (b) shows a circular transducer. When the transducers for transmitting and receiving waves are separated in this way, each element of the array transducer and its four paths can be used exclusively for receiving waves, and signal processing is then performed. It goes without saying that this transducer can also be used for the reflection method orthography.

(iv) In the array transducer shown in FIG. 4, the number of elements is reduced in the central transmitting transducer part of the 64×6411 elements, but the number of elements is still large. (0) Even if it is circular as shown in the figure, there are still quite a lot of elements, so reduce the number of elements to about 16 x 16 x π/4'F200 and set the solid angle of the viewing angle to about 1/4 ( (apex angle of about -10 to 15 degrees), it is possible to facilitate image reconstruction calculations. In this case, a practical method is to mechanically swing the array transducer 1 in a two-dimensional three-dimensional space by an amount corresponding to the reduced viewing angle, and to take images for each part. If it is mechanically difficult to shake a heavy array transducer, use a reflector mounted on a gimbal or rotate 2f! It is best to use a prism type.

(Effects of the Invention) As described in detail above, according to the present invention, orthography by the return transmission method using ultrasound can be obtained in a short time,
The imager according to the above method can be practically realized, and the practical effects are great.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of an embodiment of the method of the present invention, Fig. 2 is a timing chart of wave transmission and reception, Fig. 3 is a block diagram of an embodiment of a device implementing the method of the present invention, and Fig. 4 is an explanatory diagram of an embodiment of the method of the present invention. 1 is a diagram of an embodiment of an array transducer used in the device of the present invention; FIG. 1... Two-dimensional transducer 2... Target area 4... Echo generator 12... Range gate 13... Detector 14
...Image reconstruction calculation unit 15.18...RAM 16...DSP1
7...PROM 19...DSC20
...TV

Claims (8)

[Claims] (1) In an orthography display method using the return transmission method in which ultrasound is transmitted and received from the same direction to obtain an orthography image, ultrasound signals are focused from a two-dimensional array transducer all at once to cover the entire angle of view of the target object. The wave is transmitted through the target area and reflected from the echo generating part behind the target area, and the wave is received while scanning by the array transducer focused on the target area, and the wave is transmitted through the target area. An orthography display method using an ultrasonic return transmission method, characterized in that an image is reconstructed based on information from received attenuation. (2) The orthographic display method using the ultrasonic return transmission method according to claim 1, characterized in that data obtained by transmitting and receiving the ultrasonic waves a large number of times is averaged. (3) The orthographic display method using the ultrasonic return transmission method according to claim 1, wherein data obtained by transmitting and receiving ultrasonic waves a large number of times is subjected to a process of extracting changes in the time axis direction. (4) The orthographic display method using the ultrasonic return transmission method according to claim 1, wherein a pulse modulated ultrasonic signal as long as a continuous wave is used for transmission in order to increase the average power. (5) The transmission and reception of waves by the two-dimensional array transducer is as follows:
2. An orthographic display method using an ultrasonic return transmission method according to claim 1, wherein said two-dimensional array transducer and a mechanical sector scanning device are used in combination. (6) It has multiple elements, and when transmitting waves, it sends waves non-focally to a range that covers the required angle of view, and receives the reflected signal from the echo generating part behind the target area, passing through the target area again. A two-dimensional array transducer that sometimes focuses on the target area and receives data, a distance setting unit that extracts received data regarding the target area, and a unit that reconstructs an image from the received data extracted by the distance setting unit. An orthography apparatus implementing an orthography display method using an ultrasonic return transmission method, characterized in that: (7) The orthography apparatus according to claim 6, wherein the distance setting means is configured to also receive a reflected signal from the target area. (8) The orthography apparatus according to claim 6, wherein the two-dimensional array transducer comprises a single convex transducer for transmitting waves and an array transducer for receiving waves.