JPH0228871B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image processing apparatus that scans a medium whose physical state differs depending on its position in polar coordinates using pulse waves and displays the state of the medium as an image.

A sector scanning ultrasonic diagnostic apparatus is known as a specific example of this type of image processing apparatus. This device deflects ultrasonic pulses emitted into the body into a fan shape and performs polar coordinate scanning called sector scanning to extract and display tomographic image signals that indicate the internal state of the body. Because it can perform scanning by emitting sound wave pulses, it is mainly used to display tomographic images of the heart.

By the way, television format is generally the most suitable display format for image processing systems. Firstly, it is possible to directly connect a variety of television-related equipment and take advantage of their functions, and in particular, it is possible to arbitrarily record and play back images using a relatively inexpensive VTR.Secondly, television monitors are used in many fields. The reason for this is that it is widely used and has high reliability as a display device.

Now, in order to display the image signal obtained by the polar coordinate scanning described above on a television monitor, a process called scan conversion is required. Various types of scan converters have been considered for performing this processing, and as one of them, a digital scan converter using a digital memory as an image memory will be described.

Figure 1 schematically shows an image memory that can store image signal data for one screen of a television monitor. It has many image areas (cells) with different addresses. In this case, it is appropriate to set the number of cells in both the X and Y directions to about 512 to match the 525 scanning lines of a television monitor. Further, each cell is often about 4 or 5 bits because it is necessary to express the image signal data of each pixel in gradation.

Data is read from the image memory in synchronization with the scanning of the television monitor and according to the same scanning method (television scanning method). That is, when reading data to be displayed on a certain scanning line of a television monitor, the Y coordinate is fixed at the value for that scanning line, and the X coordinate is changed by 1 according to the sweep on the television monitor. By incrementing each address, the contents of each address are sequentially read out. The data string read out from the image memory in this way is
The data is converted into analog data by a D/A converter and input to a television monitor. Note that in order to function as a scan converter, the writing and reading operations of the image memory need to be apparently independent, but this can be achieved by switching these operations at high speed in a time-division manner.

On the other hand, the image signal data to be written into this image memory is an image signal obtained by polar coordinate scanning, in the previous example, each reflected signal of a pulse wave by sector scanning is sampled at a constant cycle by an A/D converter and digitized. obtained by doing. To write these image signal data to the image memory,
It is necessary to specify the address at which each data is to be written, that is, both the X and Y coordinates, but these are determined by the deflection angle in the polar coordinate scan at which the data was obtained, and the time position at which this data is sampled (this means that the reflected signal is When extracted as a signal, it corresponds to the time from the time the pulse wave is emitted until the reflected signal is received), that is, the number of the data in the series of data obtained at that deflection angle. It can be calculated by calculation. Second
The figure schematically shows how image signal data is stored in the image memory in this way, and the shaded area is the image obtained by scanning at deflection angles of θ _i and θ _i+1 in polar coordinate scanning. Indicates the address to which signal data is to be written. Then, an image signal is written to each of these addresses as data having gradation according to the amplitude of the image signal, which is read out using the television scanning method and displayed on a television monitor as described above.

Two problems arise here. First, the part that should be displayed as a single diagonal line on the screen is
Since an image is made up of pixels, it cannot be expressed as a single continuous line.Secondly, the pattern of polar coordinate scanning spreads farther away and the scanning lines become rougher, causing the image memory to become rougher. The problem is that there are addresses in which no image signal data is written. As a result, the final image displayed on the television monitor is of very poor quality.

One possible solution to this problem is to reduce the pitch of the deflection angle of polar coordinate scanning to such an extent that there are no addresses in the image memory where no image signal data is written. However, this method requires a long time to construct one image, which poses a problem when imaging something that moves quickly, such as the heart.

This invention has been made in view of the above points, and its purpose is to provide an image processing device that can display an image signal obtained by polar coordinate scanning such as sector scanning as a high-quality image on a television monitor. .

First, an outline of the invention will be explained. The above-described problem can be solved by equivalently eliminating addresses (cells) in which no image signal data is stored in the image memory. In this case, instead of reducing the pitch of the deflection angle of polar coordinate scanning as described above, a way to equivalently eliminate such addresses without image signal data is to Based on the data stored in the image memory, the data to be written to that address, so-called interpolation data, is approximately obtained, and it is placed at the position in the data string to be read from the image memory where the contents of that address are to be read. It is appropriate to insert it.

However, when performing such interpolation processing, the problem is how to detect the position where interpolation data should be inserted, that is, the address in the image memory where no image signal data is stored. The first possible way to do this is to sequentially add the data string read from the image memory to a level detector, and if the detected level is below a certain value, no data is stored at the address corresponding to that timing. This is a method of determining. However, in reality, the values of the image signal data stored at each address are not necessarily all above a certain value, and some are close to 0, so this method also replaces such data with interpolated data. This inconvenience arises.

In order to avoid such inconveniences, the present invention provides means for accumulating information indicating the presence or absence of image signal data at each address of the image memory, so that the image signal data of the data string read from the image memory is accumulated. This system is designed to reliably detect a position where the contents of an address that has not been read is read, and to correctly insert interpolated data only at that position.

Hereinafter, this invention will be explained in detail with reference to Examples.

FIG. 3 shows an embodiment in which the present invention is applied to a sector scanning type ultrasonic diagnostic apparatus. In the figure, reference numeral 1 denotes an ultrasonic probe, which is composed of an array transducer in which a large number of ultrasonic transducers are arranged in a line. By controlling the timing of driving each of the transducers, the beam of ultrasonic pulses emitted from the ultrasonic probe into the body is deflected in a fan shape, resulting in so-called sector scanning. The transmitter/receiver circuit 2 is driven by each transducer of the ultrasonic probe 1 and the system controller 9 in accordance with a constant period pulse signal that determines the emission timing of ultrasonic pulses and data that determines the deflection angle. The received reflected waves from various parts of the body are converted into electrical signals and extracted as image signals.

A series of reflected wave signals (image signals) extracted from the transmitting/receiving circuit 2 by one emission of an ultrasonic pulse from the ultrasonic probe 1 are processed by the sampling clock pulse from the system controller 9 in the A/D converter 3. It is sampled and digitized at a fixed period according to the following.

The image signal data digitized by the A/D converter 3 is sequentially written and stored in the image memory 4 under the control of the system controller 9. In this case, as described above, the address consisting of orthogonal coordinates in the image memory 4 where each image signal data is written is the deflection angle in polar coordinate scanning (monitor scanning) when the data is obtained, and the A/ D
The address information is determined by the time position of sampling in the converter 3 and is given to the image memory 4 from the system controller 9 in synchronization with the input of image signal data.

The contents of this image memory 4 are read out using the television scanning method. That is, the contents of all addresses are sequentially read out regardless of the presence or absence of image signal data.

The data string read out from the image memory 4 in this way is input to the interpolation processing unit 6, where the interpolated data is inserted into the position where the content of the address where no image signal data is stored is read out from the image memory 4. .

In this case, in the data string read out from the image memory 4, the portion where there is no image signal data, that is, the position where the content of the address where no image signal data is stored is read out is based on the information stored in the sector pattern memory 5. detected by.

Like the image memory 4, the sector pattern memory 5 has the same number of cells (for example, 512 x 512) as the image memory 4, each having a large number of cells having addresses made up of orthogonal coordinates, and each address corresponds to an address in the image memory 4. Information indicating the presence or absence of image signal data is stored in advance. That is, when writing image signal data to the image memory 4 via the A/D converter 3, if the center in sector scanning and the deflection angle of each scanning line are constant, the data can be written to which address in the image memory 4. Since it is known in advance whether the image signal data will be written into the image memory 4, information "1", for example, is written in the address of the sector pattern memory 5 corresponding to the address of the image memory 4 where the image signal data is written, and the other Image memory 4 into which signal data is written
Information "0" different from this is written in the address of the sector pattern memory 5 corresponding to the address. Specifically, such sector pattern memory 5 can be constituted by a ROM. The contents of the sector pattern memory 5 are sequentially read out in synchronization with the readout from the image memory 4 and delayed one by one in the X coordinate direction from the readout address of the image memory 4, and sent to the interpolation processing section 6. Supplied. That is, when reading from the sector pattern memory 5, address information obtained by decrementing the read address information given to the image memory 4 by one address in the X coordinate direction is given to the sector pattern memory 5.
The interpolation processing section 6 performs interpolation processing on the data string read out from the image memory 4 according to the information read out from the sector pattern memory 5.

Note that 1 bit is sufficient for one cell in the sector pattern memory 5, and the readout time can be made equal to or shorter than that of the image memory 4. Therefore, the interpolation processor 6 receives information as to whether or not the content of an address without image signal data has been read out from the image memory 4 at a speed sufficient to perform interpolation processing on the data string read out from the image memory 4; In other words, it is possible to transmit information as to whether or not interpolation processing is necessary. Furthermore, the address control system for the sector pattern memory 5 can be the same or almost the same as that for the image memory 4.

The interpolation processing unit 6 interpolates data by linear approximation, for example, but in this embodiment,
A one-dimensional linear approximation in direction (horizontal scanning direction of television scanning) is sufficient. In other words, the beam width of the ultrasonic pulse emitted from the ultrasound probe 1 cannot be made as narrow as the pulse width in the direction of propagation at the current technological level, so the resolution of the obtained image is Compared to the resolution (distance resolution), the resolution in the direction perpendicular to it (vertical resolution) is worse. This indicates that the density of an image at a certain point has a greater correlation with the image density of a neighboring point in the perpendicular direction than with the neighboring image density in the direction of propagation of the ultrasonic wave. In other words, the data to be stored at each address in the image memory 4 has a higher correlation with data at addresses adjacent in the X direction than with data at addresses adjacent in the Y direction. It means that is large. Therefore, in such a case, a high-quality image can be obtained even by one-dimensional linear approximation in the X direction in the interpolation process.

A specific example of the configuration of such an interpolation processing section 6 is shown in FIG. In the figure, a data string read out from the image memory 4 is input to the terminal T ₁ , and each data of this data string is inputted from the system controller 9 to the terminal T ₂ in synchronization with the reading of data from the image memory 4. It is first stored in the first latch 11 by the clock pulse applied. The contents of the first latch 11 are further transferred to the second latch 12 by the next clock pulse, at which time the next data is stored in the first latch 11. The input data α to the terminal _T1 and the output data γ of the second latch 12 are input to the averaging section 13,
Their additive average value is calculated.

Now, as shown in Figure 5, the data α and γ are
Image signal data whose Y coordinates are located at the same address in the image memory 4, that is, the same scanning line of television scanning, and these two in the image memory 4
It is assumed that no image signal data is stored in the addresses (X _n , Y _o ) between the two addresses. In this case, the contents of this address ((X _n , Yo ₎ of the data string read out from the image memory 4 are inserted as interpolated data at the read position, as if it were the address (X _n , _Yo ) from the beginning. The image signal data that should be displayed as having been accumulated in the averaging section 1
The output data of 3 is (α+γ)/2. On the other hand, if image signal data is stored at the address (X _n , Y _o ) of the image memory 4, the output data β of the first latch 11 becomes the data to be displayed. The terminal determines which data (α+γ)/2 or β should be output as data to be displayed.
The selection is made by the selector 14 based on the information from the sector pattern memory 5 input to _T3 . That is, as described above, when reading the sector pattern memory 5, address information obtained by decrementing the read address information given to the image memory 4 by one address in the X coordinate direction is given to the sector pattern memory 5, so that the sector pattern The contents of the memory 5 are sequentially read out at timings shifted by one in the X-coordinate direction of the read address of the image memory 4. Therefore, the information read from the sector pattern memory 5 temporally corresponds to the output data of the first latch 11, which is data obtained by delaying the data read from the image memory 4 by one address. When the information input from the sector pattern memory 5 to the terminal _T3 is "0", the selector 14 outputs the output data β of the first latch 11 at that time because the image signal data in the image memory 4 is stored. The output data (α+γ)/2 of the averaging section 13 is selected as data read from an address that does not exist (therefore, the data value is 0) and output as interpolated data. Also, terminal T ₃
When the information input to is "1", the output data β of the first latch 11 at that time is stored in the image memory 4.
The selector 14 selects this data β and outputs it as it is, assuming that the image signal data is read from the address where it is stored.

In this way, the interpolation processing unit 6
Interpolated data is inserted into the position where image signal data is missing in the data string read from the data string. The image signal data output from the interpolation processing unit 6 is converted into an analog signal by a D/A converter 7 under the control of a system controller 9, and then
The signal is mixed with a synchronizing signal for television scanning supplied from the television monitor 8 and then supplied to the television monitor 8. In this way, an image showing the internal state of the body, that is, a tomographic image obtained by sector scanning, is displayed on the television monitor 8. In this case, the displayed image is
Even in the far and lateral parts of the sector scan, there is no blurring due to the interpolation of the image based on the interpolation data, and the overall quality is very high and easy to see.

In addition, in the above explanation, the sector pattern memory 5
Although ROM was used, RAM was used and image memory 4
When writing image signal data to, for example, information "1" is written to the address of the corresponding sector pattern memory 5.
may be written. In this way,
Even if the position of the data written in the image memory 4 is moved, this can be easily accommodated.

Furthermore, the sector pattern memory 5 does not necessarily need to be provided separately from the image memory 4, and some bits (one bit is sufficient) in each address of the image memory 4 are used to store the image signal in that address. Information indicating the presence or absence of data may be stored. This configuration is very effective if the image memory 4 has sufficient capacity.

Furthermore, the present invention is not limited to sector-scanning ultrasonic diagnostic apparatuses, but can generally be applied to apparatuses in which an image signal obtained by polar coordinate scanning is displayed as an image on a television monitor via a digital scan converter.

Furthermore, the specific method of interpolation processing in the present invention is not limited to the method of using the averaging section as interpolation data as explained using FIGS. 4 and 5, but also interpolation processing using various linear approximations such as weighted addition. In some cases, it is also possible to use data stored in an address in the image memory where no data exists and, for example, in an address adjacent in the X direction, as is as interpolation data.

As explained above, according to the present invention, image signals obtained by polar coordinate scanning such as sector scanning are stored in an image memory having addresses made of orthogonal coordinates, and then read out using the television scanning method and displayed on a television monitor. When displaying, a high quality image can be displayed by interpolating the lack of data caused by coarse scanning mainly in the far part of polar coordinate scanning.

In particular, since the present invention is provided with a means for accumulating the presence or absence of image signal data at each address in the image memory, it is possible to reliably detect the position where the contents of an address without image signal data are read from the image memory, and therefore the interpolation process It has the advantage that it can be performed correctly only at positions where data is missing.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing an image memory with an orthogonal coordinate configuration, FIG. 2 is a diagram showing how image signal data of two scanning lines in sector scanning is written to the image memory, and FIG. A diagram showing the configuration of an image processing apparatus according to an embodiment of the present invention, FIG. 4 is a diagram showing a specific configuration example of the interpolation processing section in the embodiment, and FIG. 5 shows an interpolation processing mode in the embodiment. It is a figure for explaining.

Claims (1)

[Scope of Claims] 1. Means for obtaining an image signal by scanning a medium whose physical state differs depending on the position using pulse waves in polar coordinates, and an A/C for sampling and digitizing the image signal to output image signal data a D converter; the image signal data is stored in an address consisting of orthogonal coordinates determined based on the deflection angle of the pulse wave in the polar coordinate scanning and the time position of the sampling, and the contents thereof are converted into data by a television scanning method; an image memory that is read out as a column; a means for accumulating information indicating the presence or absence of image signal data in each address of the image memory; Data from an address with data is output as is, and data from an address without image signal data is output from an address with image signal data near the address without image signal data at the position where the data is read. an interpolation processing means for inserting and outputting the interpolation data obtained from the interpolation processing means; a D/A converter for converting the image signal data outputted from the interpolation processing means into analog; An image processing device comprising: a television monitor that displays an image of the state of a medium. 2. The means for accumulating information indicating the presence or absence of image signal data in each address of the image memory has an address consisting of orthogonal coordinates corresponding to each address of the image memory, and stores the above information in each address in advance. An image processing apparatus according to claim 1, wherein the image processing apparatus is characterized in that: 3. A patent claim characterized in that the means for accumulating information indicating the presence or absence of image signal data in each address of the image memory is such that the information is written when image signal data is written to the image memory. The image processing device according to item 1. 4. A patent claim characterized in that the means for accumulating information indicating the presence or absence of image signal data in each address of the image memory accumulates the information in some bits of each address of the image memory. The image processing device according to item 3.