JP2000041982A - Ultrasonograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a higher quality diagnostic image by providing a dynamic two-dimensional filter that varies the frequency passing band of an echo signal in the two directions of the sending and receiving direction of an ultrasonic beam and the scanning direction of the ultrasonic beam. SOLUTION: A control circuit switches a read address of a filter factor on the basis of address information in the vector direction R and the lateral direction θ of an ultrasonic beam. In response thereto, reads a filter factor corresponding to the address information is read, and given to a two-dimensional filter operation circuit, echo signal data are weighted on the basis of the data, computed and filtered for the vector direction R and the lateral direction θ. Echo signal data passing the dynamic two-dimensional filter 12, is interpolated between R and θ in an R and θ interpolation circuit 14, converted to a fan- shaped display image in accordance with the sector scan of ultrasound, stored in an image memory 16 as image data, and ultimately output on a monitor 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to a technique for filtering an echo signal when a diagnostic image is created from an echo signal obtained based on the transmission and reception of an ultrasonic beam. .

[0002]

2. Description of the Related Art Generally, the attenuation characteristics of an ultrasonic echo change in accordance with the depth in a subject. That is, there is little attenuation in the shallow part, so that there are many high frequency components, and in the deep part, there are many low frequency components due to the attenuation. Therefore, if only echo signals of the same frequency component are always extracted, an appropriate image cannot be obtained. For this reason, the following measures are taken in the prior art.

For example, when the sector scanning type shown in FIG. 4 is used, a polar coordinate system centered on a sound source O is assumed, the transmitting and receiving direction of the ultrasonic beam is set to the vector direction R, and the scanning direction of the ultrasonic beam is set to the vector direction R. Assuming the lateral direction θ, for each ultrasonic beam along the vector direction R, a so-called dynamic filter that temporally changes the frequency passband of the echo signal according to the change in the frequency component of the ultrasonic wave is used. This is used to always obtain an echo signal of appropriate intensity without being affected by depth.

[0004]

As described above, in the prior art, the noise component is suppressed in the vector direction R of the echo signal by using a dynamic filter. That is, conventionally, only a one-dimensional dynamic filter is used.

However, in the case of the sector scanning shown in FIG.
The linear density of the ultrasonic beam differs depending on the depth. In other words, the linear density is high in a shallow part close to the sound source, and low in the deep part. For this reason, the sampling frequency seen two-dimensionally differs between the shallow part and the deep part. In other words, even when the echo signal is sampled at a constant sampling frequency along the vector direction R, the line density is lower in the lateral direction θ as it goes deeper, so that the sampling frequency becomes lower accordingly. . If the sampling frequency in the lateral direction θ is low and the sampling theorem is not satisfied and an unnecessary signal component is included, the signal of the unnecessary component is removed by the conventional dynamic filter processing only in the vector direction R. It cannot be removed sufficiently.

The above description is for the sector scanning type, but the situation is the same for the convex type.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and is not limited to the transmitting / receiving direction (vector direction) of an ultrasonic beam, but also to the scanning direction (lateral direction) of an ultrasonic beam. An object of the present invention is to make it possible to perform appropriate filter processing in accordance with the depth so that a diagnostic image with higher image quality than before can be obtained.

[0008]

The present invention adopts the following constitution in order to solve the above-mentioned problems.

That is, according to the present invention, the echo signal obtained based on the transmission / reception of the ultrasonic beam has two directions, ie, the transmission / reception direction of the ultrasonic beam and the scanning direction of the ultrasonic beam. A dynamic two-dimensional filter for changing a frequency pass band is provided.

As a result, the filter processing can be performed in accordance with the depth, so that the image quality is further improved as compared with the related art.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In this embodiment, a sector scanning type ultrasonic diagnostic apparatus is assumed, but the present invention is not limited to this.
It is also applicable to convex type and linear scanning type.

FIG. 1 is a block diagram showing the overall configuration of an ultrasonic diagnostic apparatus according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes an ultrasonic probe for transmitting and receiving an ultrasonic wave and extracting an echo signal based on the ultrasonic wave; 2, a transmission control circuit for controlling the transmission of the ultrasonic wave; Is a beamformer 3 that synthesizes (beam-forms) the echo signals obtained by each of the transducers and outputs an echo signal corresponding to each ultrasonic beam. Reference numeral 4 denotes a vector processor that performs processing such as detection and A / D conversion on each echo signal after beamforming, 6 denotes a scan converter that creates image data based on the echo signal data obtained by the vector processor 4, and 8 denotes a scan converter. CRT or LC for displaying image data
D and the like.

The scan converter 6 comprises a frame memory 10, a dynamic two-dimensional filter 12, an Rθ interpolation circuit, and an image memory 16.

The frame memory 10 stores echo signal data generated corresponding to each ultrasonic beam from the vector processor 4 for one frame required for image display.

The dynamic two-dimensional filter 12 is a kind of digital filter that changes a frequency pass band of an echo signal obtained based on transmission and reception of ultrasonic waves in two directions, that is, a vector direction R and a lateral direction θ. As shown in FIG. 1, the control circuit 20 includes a control circuit 20, a RAM 22, and a two-dimensional filter operation circuit 24.

The control circuit 20 switches the read address of the filter coefficient based on the address information in the vector direction R and the lateral direction θ. Also, RA
M22 stores filter coefficients corresponding to the address information in the vector direction R and the lateral direction θ, and reads out the filter coefficients in accordance with the address designation from the control circuit 20. Further, the two-dimensional filter operation circuit 24 performs a weighting operation on the echo signal data based on the data of the filter coefficient read from the RAM 22 to perform a filtering process.

The Rθ interpolation circuit 14 is provided in the frame memory 10
Then, the echo signal data read through the dynamic two-dimensional filter 12 is subjected to Rθ interpolation to convert the echo signal data into a fan-shaped display image corresponding to the sector scanning of the ultrasonic wave.

The image memory 16 stores echo signal data after Rθ interpolation as image data.

Next, the operation of the ultrasonic diagnostic apparatus having the above configuration will be described.

Ultrasonic waves are transmitted and received by the ultrasonic probe 1,
In response to this, an echo signal is extracted. At this time, the transmission direction of the ultrasonic beam is controlled by the transmission control circuit 2. The echo signals obtained by the respective transducers constituting the ultrasonic probe 1 are phase-synthesized by the beam former 3, and the echo signals corresponding to the respective ultrasonic beams are output.

The vector processor 4 performs processing such as detection and A / D conversion on each of the echo signals after the beam forming, and the echo signal data is sent to the scan converter 6 and stored in the frame memory 10 for image display. One frame of required echo signal data is stored.

The dynamic two-dimensional filter 12 performs a filtering process by changing a frequency pass band of an echo signal obtained based on transmission and reception of ultrasonic waves in two directions, that is, a vector direction R and a lateral direction θ.

That is, the control circuit 20 switches the read address of the filter coefficient based on the address information of the ultrasonic beam in the vector direction R and the lateral direction θ. In response, the filter coefficients corresponding to the address information are read from the RAM 22 and supplied to the two-dimensional filter operation circuit 24. Two-dimensional filter operation circuit 24
Performs a weighting operation on the echo signal data based on the filter coefficient data read from the RAM 22 to perform a filtering process not only in the vector direction R but also in the lateral direction θ. That is, the vector direction R of the ultrasonic beam
Are temporally changed, and also in the lateral direction θ, a weighting operation is performed on echo signal data corresponding to mutually adjacent ultrasonic beams.

Thus, the dynamic two-dimensional filter 1
The echo signal data passing through 2 is subjected to Rθ interpolation by the Rθ interpolation circuit 14 and further converted into a fan-shaped display image corresponding to the ultrasonic scanning of the sector (conversion from the Rθ coordinate system to the orthogonal coordinate system), This is stored as image data in the image memory 16 and finally output to the monitor 8.

In the above embodiment, the echo signal data stored in the frame memory 10 is subjected to the two-dimensional filtering by the dynamic two-dimensional filter 12 before the Rθ interpolation circuit 12 performs the Rθ interpolation. 3
As shown in (2), a dynamic two-dimensional filter 12 is provided between the image memory 16 and the monitor 8, and two-dimensional filtering is performed on the echo signal data after Rθ interpolation by the Rθ interpolation circuit 14 and storage in the image memory 16. Processing can also be performed. Dynamic 2 in this case
The dimensional filter 12 performs a weighting operation on the echo signal data in two directions, that is, the x direction (which matches the raster direction) and the y direction orthogonal to the orthogonal coordinate system.

Also, as in this embodiment, the dynamic two-dimensional filter 12 is provided on the read side of the frame memory 10.
, A dynamic two-dimensional filter may be provided on the writing side of the frame memory 10. further,
Instead of providing the dynamic two-dimensional filter 12 on the reading side of the image memory 16 as shown in FIG. 3, the dynamic two-dimensional filter 12 may be provided on the writing side of the image memory 16.

[0028]

According to the present invention, not only the conventional dynamic filtering processing in the vector direction of the ultrasonic beam, but also the dynamic filtering processing in the lateral direction or the raster direction is performed, so that the image quality is further improved than in the prior art. Excellent diagnostic images can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main configuration of an ultrasonic diagnostic apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a specific configuration of a dynamic two-dimensional filter used in the apparatus of FIG.

FIG. 3 is a block diagram showing a modification of the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a relationship between a transmitting / receiving direction (vector direction) of an ultrasonic beam and a scanning direction (lateral direction) in a sector scanning type ultrasonic diagnostic apparatus.

[Explanation of symbols]

6 ... scan converter, 10 ... frame memory, 12
... Dynamic two-dimensional filter, 14 ... Rθ interpolation circuit,
16 Image memory.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yutaka Shimizu 1 Shiwazu Nishinokyo Kuwaharacho, Nakagyo-ku, Kyoto, Japan Inside the Sanjo Plant, Shimadzu Corporation (72) Inventor Hideki Okazaki 1 Shiwazu Nishinokyo Kuwaharacho, Nakagyo-ku, Kyoto, Japan F term in Sanjo factory (reference) 4C301 AA02 BB01 BB02 BB40 EE07 HH51 HH60 JB03 JB32 JB42 JC01 JC06 LL02 LL07 5B057 BA05 CE06 CH09 CH11

Claims (1)

[Claims] An echo signal obtained based on transmission / reception of an ultrasonic beam, the transmission / reception direction of the ultrasonic beam,
An ultrasonic diagnostic apparatus comprising: a dynamic two-dimensional filter that changes a frequency pass band of an echo signal in two directions of an ultrasonic beam scanning direction.