JP3366872B2 - Ultrasound diagnostic equipment - Google Patents

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 ultrasonic image filtering.

[0002]

2. Description of the Related Art For example, various filters have been conventionally used to improve the image quality of ultrasonic images such as two-dimensional tomographic images and two-dimensional Doppler images. For example, spatial smoothing and temporal smoothing with a low-pass filter,
Noise removal using a median filter (median extraction filter) is known. In particular, various types of filtering have been performed in order to eliminate image dropouts (so-called black dropouts) that occur in ultrasonic images.

However, if filtering such as smoothing is simply performed, even if the black voids are compensated for, the edges are blunted and the sharpness of the image is impaired. That is, there are problems of image blurring and sharpness reduction.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to prevent image blur while only compensating for black spots.

Another object of the present invention is to prevent image blur while excluding high luminance noise.

Further, another object of the present invention is to realize image processing with a configuration as simple as possible.

[0007]

(1) In order to achieve the above-mentioned object, the present invention provides a transmitting / receiving means for acquiring echo data by transmitting / receiving an ultrasonic wave, and the respective echo data as attention data. Extraction means for extracting a plurality of reference data included in a reference area of a certain range centered on the data, difference calculation means for calculating a difference between the value of the target data and the value of each reference data, and the difference is predetermined. Replacement means for replacing the value of the reference data smaller than the threshold value with the value of the data of interest, and a median value extraction process is executed for all the echo data in the reference area after the replacement, and the median value is used as the data of interest. And a median value extracting means for setting the value of.

According to the above configuration, the difference between the value of the data of interest and the value of each reference data around it is calculated. If the difference is small, the value of the reference data is replaced with the value of the data of interest, and the center Prior to the value extraction processing, the number of values of the data of interest can be increased and the values can be weighted. That is, as a preprocessing of the median value extraction, it is determined whether or not the data of interest is irregular such as black spots, and if it is irregular data, it is left as it is and excluded in the median value extraction process. So that while,
In other cases, the data of the same value is increased so that the value is selected as the median value as much as possible.

For example, in the case of interpolating only a black defect, the difference value obtained by subtracting the value of the data of interest from the value of the reference data has a positive value, and the difference value is a threshold value. Data replacement may be performed only when it is smaller.
For example, when targeting blackouts and high-intensity isolated noise, the absolute value of the difference value obtained by subtracting the value of the target data from the value of the reference data is calculated, and only when the absolute difference value is smaller than the threshold value. Data replacement may be performed.

According to the present invention, as preprocessing for extracting the median value, the value of the data of interest is weighted to prevent black spots and the like and prevent edge blunting.

(2) In order to achieve the above object,
The present invention is a transmission / reception means for acquiring echo data by transmitting / receiving ultrasonic waves, and a plurality of reference data included in a reference area within a certain range centered on the attention data with each echo data as the attention data. Extraction means for extracting,
When the median value extraction means for executing the median value extraction process for all the echo data in the reference area is compared with the extracted median value and the value of the attention data, and the difference is larger than a predetermined threshold value. And update determination means for maintaining the median value as the value of the data of interest and maintaining the value of the data of interest as it is when the difference is smaller than a predetermined threshold value.

According to the above arrangement, the median value extraction process is first executed, and as a process thereafter, the median value or the value of the original data of interest is selected. For example, if the difference value obtained by subtracting the value of the data of interest from the median value is positive, and if the difference value is larger than the threshold value, there is a high possibility of blackout, so the median value is adopted as the value of the data of interest. , Otherwise, the original value of the data of interest is maintained.

According to the present invention, as the post-processing of the median value extraction, it is possible to prevent the black spots and the like and prevent the rounding of the edges by performing the median value acceptance / rejection determination.

(3) Preferably, it includes means for variably setting the threshold value. The degree of processing can be adjusted by changing the threshold value. Further preferably, at least one of a first mode in which the absolute value of the difference is compared with the threshold value and a second mode in which the difference itself is compared with the threshold value are provided. More preferably, it includes means for selecting the first mode and the second mode.

(4) The above preprocessing method will be described by using an actual example.

First, for example, 3 × 3 echo data is extracted from an ultrasonic image as shown below. Here, the data in the center is the data of interest to be filtered (d22), and the data around it is the reference data.

[0017]

[Equation 1] For each reference data, the value of the data of interest is subtracted from the value of the reference data to obtain a difference value, and the absolute value thereof is further obtained. Then, it is determined for each absolute difference value whether it is equal to or less than the threshold value T. If the condition is satisfied, the value of the reference data is replaced with the value of the data of interest. That is, the reference data
If it is dij, it is processed as follows.

[0018]

[Equation 2] According to the above processing, in addition to black spots having an extremely small echo value, noise having an extremely large echo value is also processed.
On the other hand, if only the black spots are processed, the difference value itself may be used as the determination standard. That is, it is processed as follows.

[0019]

[Equation 3] When the explanation is given along with a specific example, for example, the following (a)
When there is a data group such as, the matrix obtained by subtracting the value of the data of interest from the value of each reference data is expressed as shown in (b) below, and each difference value and the threshold value T which are its constituent elements When (for example, T = 10) is compared and the data is replaced, the following (c) is obtained. This (c)
When median extraction processing (median processing) is performed on
31 is determined as the processing result, that is, the updated value of the data of interest.

[0020]

[Equation 4] On the other hand, if the data group is (e) below,
The difference is calculated as in (f) below, and data replacement is performed as in (g) below. On the other hand, when the median value is extracted, 22 is obtained, and as a result, the original value of the data of interest is maintained.

[Equation 5]

(5) Next, a simplified example of the above post-processing method will be described. In the case where the following data group (i) exists, when the median value is extracted, the median value (31) is obtained, and the acceptance / rejection determination is performed. Specifically, the difference value obtained by subtracting the original value from the median value is obtained, and when the difference value is larger than the threshold value T, the median value is adopted. The median is adopted in the following example.

[0022]

[Equation 6] On the other hand, in the case of (j) below, the median value is not adopted because the difference value from the original value is smaller than the threshold value T, and the original value (22) is maintained. become.

[0023]

[Equation 7] Incidentally, also in this case, the absolute difference value can be used as a reference.

Although the processing results of the above-mentioned pre-processing method and post-processing method may be slightly different from each other, they are common in terms of effects. Especially, in the latter case, the circuit configuration is simple, so that there is an advantage that the device cost can be reduced.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention to which the above principle is applied will be described below with reference to the drawings.

FIG. 1 shows a preferred embodiment of the ultrasonic diagnostic apparatus according to the present invention, and FIG. 1 is a block diagram showing the overall structure thereof.

In FIG. 1, the probe 10 functions as a wave transmitting / receiving means for transmitting / receiving ultrasonic waves, and is used, for example, in contact with the surface of a living body or inserted in a body cavity. An array transducer including a plurality of vibrating elements is provided in the probe 10, and an ultrasonic beam is electronically scanned by electronically scanning the array transducer. As a result, a two-dimensional data acquisition area is formed.

The transmitter / receiver 12 is a circuit that supplies a transmission signal to the probe 10 and processes a reception signal from the probe 10. The transmitter / receiver 12 forms a transmission beam and a reception beam. The signal processing unit 14 is a circuit that performs predetermined signal processing such as detection. Incidentally, the signal processing includes signal processing for B-mode image formation and signal processing for Doppler image formation. The scan converter 16 is configured as, for example, a digital scan converter (DSC), and the scan converter 16 has a function of converting the coordinate system of echo data. That is, for example, echo data captured according to the polar coordinate system is output according to the orthogonal coordinate system on the display screen. A frame memory is provided in the scan converter 16, and echo data for one B-mode image is stored in the frame memory.

The difference detector 18 is a circuit that subtracts the value of the data of interest from the value of the reference data to calculate the difference value, and further compares the difference value with a threshold value. The threshold setting device 20 is
This is a circuit for setting a threshold value by the user, and the threshold value can be appropriately changed by using the threshold value setting device 20. For example, the effect of the filter can be increased or decreased by changing the threshold value. The data converter 22 is a circuit that replaces the value of the reference data with the value of the data of interest when the difference value is smaller than the threshold value.

As is well known, the median filter 24 is a circuit that determines the median value from a plurality of echo data and uses it as the value of the data of interest. The filtered ultrasonic image is output to the image display 26. Incidentally, each processing from the difference detection to the filtering described above is executed for each echo data, that is, for each target data.

FIG. 2 shows a concrete configuration example of the difference detector 18 and the data converter 22. Scan converter 1
Three data memories 34 are connected in parallel to the output side of 6. For example, when filtering is performed in units of 3 × 3 echo data, three echo data are stored in each of the three data memories 34.
Here, the middle echo data in the central data memory 34 corresponds to the data of interest. As described above, each data memory 34 stores the echo data string in the horizontal scanning direction of the display or along the ultrasonic beam, and the number and capacity of the memories can be appropriately changed according to the size of the filter window. do it. Incidentally, each time the target data is changed, the value in the data memory 34 is changed one by one or all.

The data comparator 36 is provided in each data memory 34.
Is a circuit that subtracts the value of the target data from the value of the reference data output from to obtain a difference value, and outputs the comparison result obtained by comparing the difference value and the threshold value. The data replacement circuit 38 determines whether to maintain each reference data as it is or replaces its value with the value of the data of interest based on each comparison result, and executes the determination. Then, after the data replacement process, for example, 3
Median filter 24 performs median value extraction processing on the echo data of × 3.

Therefore, according to the configuration shown in FIG.
Since processes such as data comparison and data replacement can be executed in parallel, there is an advantage that real-time performance can be improved.

Although the configuration examples shown in FIGS. 1 and 2 are based on the above-described pre-processing method, a configuration example according to the post-processing method will be described below. The same components as those described above are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 3, a median filter 30 is provided after the scan converter 16. A difference detector 18 for calculating the difference between the original value and the median value of the data of interest and comparing the difference value with the threshold value is provided at the subsequent stage. The data selector 32 determines whether to adopt the value of the original data of interest or the median based on the comparison result. The filtered image is sent to the image display 26 as described above.

FIG. 4 shows a specific example after the scan converter 16 shown in FIG. After the scan converter 16,
Similar to the configuration example shown in FIG. 2, three data memories 40 are provided in parallel, and the median filter 3 is provided at the subsequent stage.
0 is provided. Further, in the subsequent stage, the median value and the value of the target data are compared, and if the difference value is larger than a predetermined threshold value, the median value is adopted, and if the difference value is smaller, the value of the original target data is adopted. A data comparison / replacement circuit 42 is provided. This circuit 42 corresponds to the difference detector 18 and the data selector 32 shown in FIG.

FIGS. 5 and 6 are flowcharts showing data processing according to the above-described preprocessing method and postprocessing method.

First, in FIG. 5, in S101, for example, 3 × 3 echo data is extracted. In S102, S
The difference between the value of the data of interest and the value of the reference data is calculated for the echo data group extracted in 101. Specifically, although the value of the data of interest is subtracted from the value of the reference data, it goes without saying that the value of the reference data may be subtracted from the value of the data of interest.

In S103, the processing mode is selected. Here, the first mode is a mode intended to eliminate black spots and noise, and the second mode is basically a mode intended to eliminate black spots. If it is determined in S103 that the first mode is selected, S104
In step S102, the absolute value of the difference value, that is, the absolute difference value is obtained. On the other hand, when the second mode is selected, the difference value calculated in S102 is used as it is.

In S105, it is determined whether or not the difference value is larger than 0 and equal to or smaller than the threshold value T. Here, if the condition is satisfied, the value of the reference data is replaced with the value of the data of interest in S106. That is, data replacement is performed to increase the control rate of the value of the data of interest and weight it. On the other hand, if the condition of S105 is not satisfied, the data of interest is not replaced because the data of interest needs to be actively processed. In S107, it is determined whether or not the processing has been completed for all the reference data in the echo data group extracted in S101, and if not completed, the reference data as the calculation target is changed in S108, and the above-described processing is performed. Is repeatedly executed. In S109, a process of extracting the median value is executed for the echo data group extracted in S101. That is, the processing by the median filter is executed. Then, in S110, for example, it is determined whether or not the above-mentioned processing is completed for each echo data forming the B-mode image, that is, all the attention data. If the processing is not completed, one attention data is changed in S111. The above steps are repeatedly executed.

FIG. 6 is a flowchart showing the processing steps according to the above-mentioned post-processing method. In S201, the echo data group is extracted as in S101 above,
After that, the median value extraction processing is executed in S202. In S103, the difference value is calculated by subtracting the original value from the median value.

In S204, the processing mode is determined, and when the first mode is selected here, the absolute value is calculated for the difference value in S205. That is, the absolute difference value is obtained.

In S206, it is judged whether or not the difference value or the absolute difference value obtained in S203 is less than or equal to the threshold value T, and if the condition is satisfied, the original value is obtained in S208 to prevent the edge from becoming blunt. The value of the attention data is adopted as it is. On the other hand, if the condition of S206 is not satisfied, the median value is adopted as the value of the data of interest in S207 in order to eliminate black spots and noise.

In S209, it is judged whether or not the processing has been completed for all the data of interest. If not, S2
At 10, the attention data is changed by one, and the above steps are repeatedly executed.

As described above, according to the present embodiment, the median value extraction processing is selectively applied, and as a result, it is possible to remove the black spots and the like while preventing the edges from becoming dull. Further, by selecting the mode, it is possible to set only the black voids as the processing target or both the black voids and the noise as the processing target, so that there is an advantage that an appropriate processing mode can be selected according to the state of the ultrasonic image. is there.

The above principle is not limited to B-mode images and the like, but may be applied to two-dimensional Doppler images and the like. Further, if the threshold value is variably set by the user as described above, there is an advantage that the effect of the filter can be controlled.

[0047]

As described above, according to the present invention,
It is possible to remove only black spots while preventing image blur. Further, according to the present invention, there is an advantage that image blur can be prevented while excluding high-luminance noise.

[Brief description of drawings]

FIG. 1 is a block diagram of an ultrasonic diagnostic apparatus according to a first embodiment.

FIG. 2 is a diagram showing a specific example of a difference detector and a data converter.

FIG. 3 is a block diagram of an ultrasonic diagnostic apparatus according to a second embodiment.

FIG. 4 is a diagram showing a specific example of a difference detector and a data converter.

FIG. 5 is a flowchart showing each step of the pretreatment method.

FIG. 6 is a flowchart showing each step of the post-processing method.

[Explanation of symbols]

10 probe, 12 transceiver, 14 signal processor, 1
6 scan converter, 18 difference detector, 20 threshold setter,
22 data converter, 24,30 median filter, 26 image display.

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Claims (5)

(57) [Claims] 1. A transmission / reception means for acquiring echo data by transmitting / receiving ultrasonic waves, and each echo data as attention data, and a plurality of references included in the attention data and a reference area of a certain range centered on the attention data. Extracting means for extracting data, difference calculating means for calculating the difference between the value of the target data and the value of each reference data, and replacing the value of the reference data with the difference smaller than a predetermined threshold value with the value of the target data And a median value extraction unit that performs median value extraction processing on all echo data in the reference area after the replacement, and that median value is the value of the data of interest. Ultrasonic diagnostic equipment. 2. A transmission / reception unit for acquiring echo data by transmitting / receiving ultrasonic waves; a plurality of echo data as attention data, and a plurality of attention data and a plurality of reference areas centered around the attention data. Extraction means for extracting the reference data, the median value extraction means for performing a median value extraction process for all the echo data in the reference area, comparing the extracted median value and the value of the attention data,
The median value is set as the value of the data of interest when the difference is larger than a predetermined threshold value, and the update determination means that maintains the value of the data of interest when the difference is smaller than the predetermined threshold value is included. And ultrasonic diagnostic equipment. 3. The ultrasonic diagnostic apparatus according to claim 1, further comprising means for variably setting the threshold value. 4. The apparatus according to claim 1, wherein at least one of a first mode in which the absolute value of the difference is compared with the threshold value and a second mode in which the difference itself is compared with the threshold value. An ultrasonic diagnostic apparatus having. 5. The ultrasonic diagnostic apparatus according to claim 4, further comprising means for selecting the first mode and the second mode.