JPH044897B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a linear compound scan type ultrasonic diagnostic apparatus.

[Technical background of the invention and its problems] As shown in FIG. 1, there are two scanning methods for the ultrasonic beam transmitted from the ultrasonic probe 1: linear scan (in the direction of arrow 1a) and compound scan (in the direction of arrow 1b). ) A compound scan, ie, a linear compound scan, is conventionally performed. FIG. 2 shows the configuration of a conventional ultrasonic diagnostic apparatus using this linear compound scan method.

Figure 2 2 inputs the ultrasound data (data converted into a digital signal) ECHO received by the ultrasound probe 1 shown in Figure 1, and outputs the gradation data GRAD and its address ADDR for each pixel. pixelization means, 7 average processing (for example, arithmetic mean processing or geometric mean processing) of the gradation data GRAD output from the pixelization means 2;
8 is an average processing means (to be described in detail later) that performs averaging processing between the previously captured ultrasound data ECHO and the newly captured ultrasound data ECHO according to the number of accesses for each screen configuration period; This image display means displays an ultrasound image based on the gradation data averaged by the average processing means 7.

The average processing means 7 applies, for example, to the gradation data GRAD outputted before the pixelization means 2,
A first calculation means 3a that sequentially adds (during arithmetic mean processing) or successively multiplies (during arithmetic mean processing) the newly outputted gradation data GRAD, and an output (calculation) of the first calculation means 3a. an image memory 4 that stores the result), an access count memory that has a memory capacity of the same number of pixels as this image memory 4, and stores the number of accesses of all pixels in one screen for each screen; By adding 1 to the output of the number of times memory 5 and writing the addition result to the number of accesses memory 5 again,
+1 addition means for updating the number of accesses; and a second means for dividing the output data of the image memory 4 by the output of the access number memory 5 (in the case of arithmetic mean processing) or calculating a route (in the case of geometric mean processing). It is configured to include calculation means 3b.

Note that the write/read control of the image memory 4 and the access count memory 5 is performed using, for example, a write pulse WE output from a memory control means (not shown).
The addressing is performed by the address signal output from the pixelization means 2.
Done by ADDR.

Next, the operation of the conventional device configured as described above will be explained with reference to FIG. 3, which shows the timing of the main parts.

Note that RAS in FIG. 3 is a memory address access signal that is output at a predetermined cycle.

When the ultrasound data ECHO collected by the linear compound scan is input to the pixelization means 2, the pixelization means 2 generates the gradation data GRAD and its address for each pixel.
ADDR is output. This gradation data GRAD is
It is written into the image memory 4 at address ADDR via the first calculation means 3a. This writing is performed, for example, at the rising edge of the write pulse WE,
At the same time, the same address is specified in the image memory 4 for the access count memory 5, and 1 outputted from the +1 addition means 6 is stored.

Next, when the light pulse WE becomes a "low" level, the image memory 4 and the access number memory 5
Therefore, the gradation data and the number of accesses are 1, respectively.
The second calculation means 3 reads out the data as a set of data.
In b, the gradation data is divided by the number of accesses (in the case of arithmetic mean processing) or a route is calculated (in the case of geometric mean processing). Furthermore, the gradation data read out from the image memory 4 is returned to the first calculation means 3a and added to the gradation data GRAD newly output from the pixelization means 2 (during arithmetic averaging processing). Or multiplication (during geometric averaging)
After that, it is written into the image memory 4 again. At the same time as this writing, 1 is also added to the access count memory 5 by the +1 addition means 6 to the updated access count at the same address as the image memory 4, that is, to the access count read out earlier. will be written. Then, the gradation data and the number of accesses are read out as a set of data from the image memory 4 and the access number memory 5, respectively, and are subjected to calculation by the second calculation means 3a.

In this way, arithmetic averaging processing (or geometric averaging processing) is performed on the gradation data GRAD, and the averaged gradation data is provided for image display (real-time display) on the image display means 8.

The series of operations described above is performed using new ultrasonic data using linear compound scan.
Repeats each time an ECHO is collected.

By the way, according to the above-mentioned ultrasonic diagnostic apparatus, stripes with different S/N ratios and resolutions, that is, moire stripes, may occur on the obtained ultrasound images.

According to the simulation results conducted by the inventor of the present application, the cause of the occurrence of the moire fringes was the process of pixelization of the sampling data. That is,
As shown in Figure 4, on the pixel matrix,
When the ultrasound beam is scanned in the direction of arrow 9, the actual sampling position will be the position indicated by the x mark.
The difference between the depth component interval of the sampling point and the pixel interval in the depth direction is (1-cos θ) pixels (where θ is the angle between the scanning direction 9 of the ultrasound beam and the depth direction 10), and ○ Although the pixel indicated by the mark is accessed once, the pixel indicated by the mark ◎ is accessed twice consecutively. This is due to operations such as rounding off, rounding down, or rounding up during pixelization in the pixelization means 2, and 1/(1-
cos θ) causes moiré fringes at each pixel interval.

FIG. 5 shows an example of linear compound scan (scanning angles of -15°, -5°, +5°, +15°) and pixelization. In the same figure, the area indicated by a is an area where pixels are accessed once, the area indicated by b is an area where pixels are accessed twice, the area indicated by c is an area where pixels are accessed three times, and the area indicated by d is an area where pixels are accessed three times. This is a region that has been accessed four times, and moiré fringes 11 are generated at every pixel interval (1/(1-cos θ) pixel interval, which is about 29 pixels) shown by arrow e. This is because, for the reason mentioned above, the location marked with a circle in the figure is accessed the number of times indicated by the number inside the circle at each interval indicated by the arrow e, which is greater than the number of accesses indicated by a to d. This is to become. (Means that the same pixel is accessed consecutively).

[Object of the Invention] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an ultrasonic diagnostic apparatus that can obtain ultrasonic images without moiré fringes.

[Summary of the Invention] The outline of the present invention for achieving the above object is as follows: pixelization means for inputting ultrasonic data captured by a linear compound scan and outputting gradation data and its address signal for each pixel; The averaging process of the gradation data output from this pixelization means is performed between the previously captured ultrasound data and the newly captured ultrasound data.
An ultrasonic diagnostic apparatus that has an averaging processing means that performs processing according to the number of accesses for each screen configuration cycle, and obtains an ultrasound image based on averaged gradation data,
The present invention is characterized by comprising access control means for preventing the averaging means from accessing the same pixel multiple times in succession based on the access signal output from the pixelization means.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 6 is a block diagram showing the configuration of an ultrasonic diagnostic apparatus according to the present invention.

Components having the same functions as those of the conventional ultrasonic diagnostic apparatus shown in FIG. 2 will be denoted by the same reference numerals, and detailed explanation thereof will be omitted.

The device shown in FIG. 6 differs from the device shown in FIG. 2 in that access control is performed in the averaging means 7 to prevent multiple consecutive accesses to the same pixel based on the address signal ADDR output from the pixelization means 2. The point is that the means 12 is provided.

This access control means 12 successively compares, for example, a latch 13 and a latch 14 connected in series with an output A of the latch 13 and an output B of the latch 14, and sets a "low" level when A=B is established. It is configured to include a comparing means (for example, a comparator) 15 that outputs an output, and an AND means 16 that outputs a logical product C of the output of the comparing means 15 and the write pulse WE.

Note that the address signal ADDR output from the pixelization means 2 is input to the latch 13,
Further, the output C of the AND means 16 is inputted to the image memory 4 and the access count memory 5 as a write/read control signal (write pulse). Further, a latch pulse LP for controlling the latch operation is inputted to the latch 13 and the latch 14.

Next, the operation of the ultrasonic diagnostic apparatus configured as described above will be explained with reference to FIG. 7.

The latch pulse LP input to the latch 13 and the latch 14 has a cycle equal to, for example, the address access signal RAS of the memory, and every time this latch pulse LP is input, the latch 13 and the latch 1
4 becomes latched at the same time.

Here, the address signal ADDR output from the pixelization means 2 is first held in the latch 13 by the first latch pulse LP. When the next latch pulse LP is input, the holding state of the latch 13 is now held by the latch 14, and the latch 13 receives the next input address signal.
ADDR is retained.

Therefore, the comparison means 15 receives the input address signal ADDR earlier than the pixelization means 2.
(output B of latch 14) and the newly input address signal ADDR (output A of latch 13). When the previously input address signal ADDR and the newly input address signal ADDR match (A=B holds), a "low" level signal is output. When the output of this comparison means 15 becomes a "low" level, the output C of the AND means 16 becomes a "low" level regardless of the presence or absence of the write pulse WE (state change), and therefore the image at the address Writing to the memory 4 and access count memory 5 is not performed.

In this way, in the comparing means 15, when A=B is established, writing to the image memory 4 and the access count memory 5 is not performed.
This means that the gradation data and the number of accesses at the address are not updated continuously, and therefore, it is possible to prevent the averaging means from accessing the same pixel multiple times in succession. To explain this with reference to FIG. 7, for example, within the constituent period Tf of one screen shown by waveform A, one RAS cycle among arbitrary pixelization accesses shown by waveform B
Continuous x-marked data in Tr is logical product means 16
is not accessed because its output C does not go to the "high" level.

Therefore, moire fringes do not occur.

In the comparison means 15, if A=B does not hold, that is, if the same pixel cannot be accessed multiple times in succession, the output of the comparison means 15 becomes a "high" level, so the logical product means 16 The logical product condition of is satisfied in response to the light pulse WE, and therefore, the averaging means 7 can process the pixelization means 2 by means of the conventional device (FIG. 2), as already explained.
Average processing will be performed on the gradation data GRAD output from the gradation data GRAD.

Although one embodiment of the present invention has been described above,
It goes without saying that the present invention is not limited to the above-mentioned embodiments, and can be modified as appropriate within the scope of the gist of the present invention.

Next, other embodiments of the present invention will be described.

FIG. 8 is a block diagram showing a modification of the apparatus shown in FIG. 6.

Components having the same functions as those of the device shown in FIG. 6 are given the same reference numerals, and detailed explanation thereof will be omitted.

The device shown in FIG. 8 differs from the device shown in FIG. 6 in the configuration of the access control means 12.
The access control means 12 in the figure is a storage means that stores an ideal access pattern in advance, such as a ROM.
(Read-only memory) 17 and this ROM
17, the ideal access count G read at address ADDR and the access count F of the access count memory 5 are successively compared, and the output F of the access count memory 5 becomes greater than or equal to the ideal access count G ( F≧G), a comparison means 18 that outputs a "low" level, and a theoretical product means 16 that outputs a theoretical product C of the output of this comparison means 18 and the light pulse WE.
It consists of:

With this configuration, the number of accesses becomes equal to the ideal number of accesses stored in the ROM 17, and it is possible to prevent the occurrence of stripes with different numbers of accesses. To explain this with reference to FIG. 9, for example, within the constituent period Tf of one screen shown by waveform A, among the accesses to any pixel shown by waveform B, the data marked with an x mark has the output C of the AND means 16 as " (This is because the access count F output from the access count memory 5 does not reach the ROM17 level in the same access.)
(meaning that the number of accesses has exceeded the ideal number of accesses G), and is not accessed.

Therefore, moire fringes do not occur.

[Effects of the Invention] According to the present invention described above, it is possible to control the number of accesses in the averaging process by the access control means and prevent multiple consecutive accesses to the same pixel, so that an ultrasound image without moiré fringes can be obtained. It is possible to provide an ultrasonic diagnostic device that provides the following.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram for explaining linear compound scan, Fig. 2 is a block diagram showing the configuration of a conventional ultrasonic diagnostic device using the linear compound scan method, and Fig. 3 is the main part of the device shown in Fig. 2. FIG. 4 and FIG. 5 are explanatory diagrams for explaining the cause of moiré fringes in the apparatus shown in FIG. 2. FIG. 7 is a timing diagram for explaining the operation of the device shown in FIG. 6, FIG. 8 is a block diagram showing a modification of the device shown in FIG. 6, and FIG. 9 is a timing diagram for explaining the operation of the device shown in FIG. FIG. 3 is a timing diagram for explaining the operation of the shown device. 2...Pixelization means, 4...Averaging means,
12...Access control means, GRAD...gradation data, ADDR...address signal.

Claims (1)

[Claims] 1 A pixelization means that inputs the ultrasonic data captured by the linear compound scan and outputs gradation data and its address signal for each pixel, and averages the gradation data output from this pixelization means first. Between the captured ultrasound data and the newly captured ultrasound data,
an address output from the pixelization means in an ultrasonic diagnostic apparatus that obtains an ultrasound image based on averaged gradation data, the ultrasound diagnostic apparatus having an averaging processing means that performs processing according to the number of accesses per screen configuration period; An ultrasonic diagnostic apparatus comprising: access control means for preventing the average processing means from accessing the same pixel multiple times in succession based on a signal.