阅读说明：本技术 超声波摄像装置以及图像处理方法 (Ultrasonic imaging apparatus and image processing method ) 是由 岸本彩 藤井信彦 于 2019-10-31 设计创作，主要内容包括：本发明提供一种超声波摄像装置以及图像处理方法,能够同时满足斑纹的去除和组织构造的清晰化这2个要求。上述图像处理方法,去除超声波图像的噪声,对噪声去除后的图像实施形态学处理。形态学处理包括进行膨胀/腐蚀的第一运算和进行开/闭的第二运算,并使用对噪声去除后的图像进行第一运算而得的结果,确定在形态学的第二运算中使用的构造要素的值。(The invention provides an ultrasonic imaging apparatus and an image processing method, which can simultaneously meet 2 requirements of speckle removal and tissue structure clarification. The image processing method removes noise from the ultrasonic image, and performs morphological processing on the noise-removed image. The morphological processing includes performing a first operation of dilation/erosion and performing a second operation of opening/closing, and the values of the structural elements used in the second operation of morphology are determined using the result of performing the first operation on the noise-removed image.)

1. An ultrasonic imaging apparatus is characterized by comprising:

an ultrasonic measurement unit that transmits ultrasonic waves to an inspection object and receives ultrasonic waves as reflected waves to acquire ultrasonic signals;

an image generating unit that generates an ultrasonic image of the inspection object using the ultrasonic signal acquired by the ultrasonic measuring unit; and

an image processing unit for processing the ultrasonic image created by the image creating unit,

the image processing unit includes:

a noise removing unit that removes noise from the ultrasonic image;

a morphological processing unit configured to perform morphological processing on the noise-removed image generated by the noise removing unit; and

and a structural element specifying unit that specifies a value of a structural element used for the morphological processing, using the noise-removed image.

2. The ultrasonic imaging apparatus according to claim 1,

the morphological processing unit includes:

a first arithmetic unit that performs at least one of expansion and corrosion using a first structural element;

a second calculation unit that performs at least one of an opening process and a closing process using a second structural element,

the component specifying unit specifies a value of the second component using the noise-removed image.

3. The ultrasonic imaging apparatus according to claim 2,

the structural element specifying unit specifies the value of the second structural element based on a difference between the image subjected to the expansion process and the image subjected to the erosion process by the first arithmetic unit.

4. The ultrasonic imaging apparatus according to claim 2,

the first arithmetic unit performs expansion and corrosion using the first structural element,

the second calculation unit performs a closing calculation using the second structural element on the expansion result using the first structural element and performs an opening processing on the corrosion result using the first structural element,

the morphological processing unit adds a difference between a closed operation result using the second structural element and a closed operation result using the first structural element, and a difference between an open processing result using the second structural element and an open processing result using the first structural element to the noise-removed image, thereby generating a morphologically processed image.

5. The ultrasonic imaging apparatus according to claim 1,

the noise removing unit removes noise using an edge-preserving smoothing filter.

6. The ultrasonic imaging apparatus according to claim 1,

the ultrasonic imaging apparatus further includes: a coordinate conversion unit for converting the coordinates of the ultrasonic image from polar coordinates to orthogonal coordinates,

the coordinate conversion unit performs coordinate conversion on the ultrasonic image before the processing by the morphological processing unit.

7. The ultrasonic imaging apparatus according to claim 1,

the ultrasonic imaging apparatus further includes: a coordinate conversion unit for converting the coordinates of the ultrasonic image from polar coordinates to orthogonal coordinates,

the coordinate conversion unit performs coordinate conversion on the ultrasonic image after the processing by the morphological processing unit.

8. The ultrasonic imaging apparatus according to claim 1,

the image processing unit further includes: and a size determining unit that determines the size of the structural element.

9. The ultrasonic imaging apparatus according to claim 8,

the size determining unit determines the size of the structural element based on the resolution and sampling interval of the ultrasonic image.

10. The ultrasonic imaging apparatus according to claim 9,

the image processing unit further includes: a storage unit for storing a table showing a relationship between imaging conditions for ultrasonic measurement and a resolution of an ultrasonic image,

the size determining unit refers to the table stored in the storage unit and determines the size of the structural element.

11. The ultrasonic imaging apparatus according to claim 8,

the size determining unit determines the size of the structural element for each pixel position of the ultrasonic image.

12. The ultrasonic imaging apparatus according to claim 8,

the size determination unit calculates the size of the structural element for each pixel position of the ultrasound image, and determines any one of a maximum value, a minimum value, and an average value thereof as the size of the structural element.

13. The ultrasonic imaging apparatus according to claim 1,

the ultrasonic imaging apparatus further includes: and a user interface section that receives a selection of the processing by the morphological processing section.

14. An ultrasound imaging apparatus that inserts a puncture needle into an examination subject and captures an auxiliary image of a path for guiding the puncture needle, the ultrasound imaging apparatus comprising:

an ultrasonic measurement unit that transmits ultrasonic waves to an inspection object and receives ultrasonic waves as reflected waves to acquire ultrasonic signals;

an image generating unit that generates an ultrasonic image of the inspection object using the ultrasonic signal acquired by the ultrasonic measuring unit; and

an image processing unit for processing the ultrasonic image created by the image creating unit,

the image processing unit includes:

a noise removing unit that removes noise from the ultrasonic image created by the image creating unit;

a morphological processing unit configured to perform morphological processing on the noise-removed image generated by the noise removing unit;

a structural element specifying unit that specifies a value of a structural element used in the morphological processing unit using the noise-removed image,

the auxiliary image is generated so that the boundary between the puncture needle and the other tissue is emphasized.

15. An image processing method for processing an ultrasonic image generated using an ultrasonic signal received by an ultrasonic imaging apparatus, comprising:

removing noise from the ultrasonic image;

a step of performing morphological processing on the noise-removed image; and

and a step of determining a value of a structural element used for the morphological processing using the noise-removed image.

16. The image processing method of processing an ultrasonic image according to claim 15,

the morphological treatment includes at least one of expansion and corrosion using the first structural element and opening and closing using the second structural element,

and determining a value of the second structural element based on a difference between the expanded image and the eroded image.

17. The image processing method according to claim 15,

before the noise removal or morphological processing, a coordinate transformation step of transforming the coordinates of the ultrasonic image from polar coordinates to orthogonal coordinates is further included.

18. The image processing method according to claim 15,

after the morphological processing, a coordinate transformation step of transforming the coordinates of the ultrasonic image from polar coordinates to orthogonal coordinates is further included.

19. The image processing method according to claim 15,

further comprising the step of determining the dimensions of the structural elements used in the morphological processing.

20. The image processing method according to claim 19,

the step of determining the size of the structural element determines the size using the resolution and sampling interval of the ultrasonic image.

Technical Field

The present invention relates to an ultrasonic imaging apparatus, and more particularly, to image processing for an ultrasonic image obtained by an ultrasonic imaging apparatus.

Background

An ultrasonic imaging apparatus is an apparatus capable of acquiring and displaying an image of an examination object simply and in real time, and is widely used in the medical field and the like. However, an image obtained by ultrasonic imaging has a lower resolution than a medical imaging apparatus such as a CT apparatus, and thus, depending on the skill of an examiner, a difference is likely to occur in the structure of an examination object and diagnosis. In addition, as a cause of deterioration in the image quality of an ultrasonic image, there is noise called speckle generated by interference between reception signals of ultrasonic waves. The speckle has a shape and a size that are different in an image, such as a slender shape and a size, as the depth is deeper, and the size of the speckle is equal to the structure of the living body, and therefore, the speckle is difficult to remove by a noise removal technique such as a general filtering process. Therefore, there is a problem that the speckle remains in the image and is difficult to distinguish from the tissue structure.

As one of techniques for improving the image quality of such an ultrasonic image, a technique using morphological techniques has been proposed (non-patent document 1 and patent document 1). In morphology, the original image is processed by combining 4 processes of Dilation (Dilation), Erosion (Erosion), opening, and closing, and the edge that is the boundary of the structure can be emphasized. The open processing is processing for expanding the image after erosion, and the close processing is processing for eroding the image after expansion. In these processes, a function called a structural element is used to determine a pixel value of an image to be processed using pixel values of surrounding pixels. The size of the structural element is the size of a region including surrounding pixels with the processing target pixel as the center, and a desired edge enhancement effect can be obtained by applying pixels of an appropriate size and value to each pixel of the original image and performing dilation and erosion.

Non-patent document 1 discloses a technique in which, when the above morphological technique is applied to an ultrasonic image, a structural element used for opening/closing after expansion/erosion is made different depending on the position of the ultrasonic image. Specifically, a high edge enhancement effect is achieved by changing the value of the structural element in accordance with whether the position of the image to be processed is an edge region or a uniform region. In order to determine the value of a structural element, the luminance variance information in the structural element is used flexibly, utilizing the tendency that the luminance variance is larger at the tissue boundary (edge region) than in other regions.

Patent document 1 discloses a method of multiplying a first group of weighting coefficients set in accordance with a position within a mask region to expand the image processing that is less likely to generate artifacts when the speckle reduction processing is performed, and multiplying the result by a second group of weighting coefficients to erode the image processing. This technique is a method of multiplying an input image by a weighting coefficient, and the value of a structural element is the same regardless of the position within the image.

In the technique described in non-patent document 1, the value of the structural element for opening and closing is changed depending on the position of the pixel, thereby achieving high edge emphasis and effectively removing speckle noise in the smoothing section, but when the difference between the structure and the speckle is insufficient, the edge of the speckle may be emphasized, and the smoothing effect may be limited.

In the technique described in patent document 1, the same processing is performed regardless of whether the edge region or the uniform region is present, and therefore the obtained edge enhancement effect is limited.

Non-patent document 1: "2-fold" reconstruction element による ultrasound image data コントラスト to cushion へ "in IEEJ trans. eis, dokun well meaning, vol.124, No.9, 2004

Patent document 1: japanese patent laid-open publication No. 2005-205199

Disclosure of Invention

The subject of the invention is: provided is a technique which can satisfy 2 requirements for speckle removal and tissue structure definition at the same time by adaptively determining the values of structural elements from a post-noise-removal image.

In order to solve the above problem, the present invention performs noise processing on an ultrasonic image, and performs morphological processing on the noise-processed image using a structural element whose value is determined from the expansion result and the erosion result of the image.

That is, the ultrasonic imaging apparatus of the present invention includes: an ultrasonic measurement unit that transmits ultrasonic waves to an inspection object and receives ultrasonic waves as reflected waves to acquire ultrasonic signals; an image generating unit that generates an ultrasonic image of the inspection object using the ultrasonic signal acquired by the ultrasonic measuring unit; an image processing unit that processes the ultrasonic image created by the image creating unit, wherein the image processing unit includes: a noise removing unit that removes noise from the ultrasonic image; a morphological processing unit configured to perform morphological processing on the noise-removed image generated by the noise removing unit; and a structural element specifying unit that specifies a value of a structural element used for the morphological processing, using the noise-removed image.

Further, an image processing method of the present invention is an image processing method for processing an ultrasonic image generated using an ultrasonic signal received by an ultrasonic imaging apparatus, the image processing method including: removing noise from the ultrasonic image; a step of performing morphological processing on the noise-removed image; and a step of determining a value of a structural element used for the morphological processing using the noise-removed image.

The present invention can perform processing for discriminating the feature of a structure in an ultrasonic image from noise unique to the ultrasonic image, and can obtain an ultrasonic image in which the noise is reduced and the structure of an inspection target is clarified.

Drawings

Fig. 1 is a diagram showing an overall configuration of an ultrasonic imaging apparatus according to an embodiment.

Fig. 2 is a flowchart showing an outline of image processing.

Fig. 3 is a block diagram showing a configuration of an image processing unit of the ultrasonic imaging apparatus according to the first embodiment.

Fig. 4 is a flowchart showing the processing of the image processing section according to the first embodiment.

Fig. 5 is a diagram illustrating morphological processing.

Fig. 6 (a) to (e) are diagrams illustrating image processing results.

Fig. 7 (a) to (d) are diagrams illustrating the effects of the first embodiment.

Fig. 8 (a) is a diagram showing the processing result of the first embodiment, and fig. 8 (b) is a diagram showing the processing result of the conventional method.

Fig. 9 is a block diagram showing a configuration of an image processing unit of the ultrasonic imaging apparatus according to the second embodiment.

Fig. 10 is a flowchart showing an outline of image processing according to the second embodiment.

Fig. 11 is a flowchart showing the processing of the image processing section according to the second embodiment.

Fig. 12 is a diagram showing an example of a UI of the ultrasonic imaging apparatus according to the third embodiment.

Description of the reference numerals

100: an ultrasonic imaging device; 10: an ultrasonic measurement unit; 20: an image generation unit; 30: an image processing unit; 31: a noise removal unit; 32: a coordinate transformation unit; 33: a morphological processing unit; 33A: a first arithmetic unit; 33B: a second arithmetic unit; 35: a structural element determination unit; 37: a synthesis unit; 39: a size determination section; 40: a control unit; 50: a storage unit; 60: a display unit; 70: an input section; 80: an ultrasonic probe.

Detailed Description

Embodiments of an ultrasonic imaging apparatus and an image processing method according to the present invention will be described below with reference to the drawings.

First, an ultrasonic imaging apparatus to which the present invention is applied will be briefly described. As shown in fig. 1, the ultrasonic imaging apparatus 100 includes, as main components: an ultrasonic measurement unit 10 that transmits ultrasonic waves to an inspection object and receives ultrasonic waves as reflected waves to acquire ultrasonic signals; an image generating unit 20 that generates an ultrasonic image of the examination object using the ultrasonic signal acquired by the ultrasonic measuring unit 10; and an image processing unit 30 for processing the ultrasound image created by the image creating unit 20. As an accessory, an ultrasonic probe (ultrasonic probe) 80 that makes contact with an object to be examined and transmits and receives ultrasonic waves is provided. The ultrasonic imaging apparatus 100 further includes a control unit 40 for controlling operations of the respective units of the apparatus, an input unit 70 for a user to input instructions such as measurement conditions and start/end of measurement, a storage unit 50 for storing images created by the image generation unit 20 or the image processing unit 30, data necessary for calculation by the image processing unit 30, and the like, a display unit 60 for displaying images, GUI (graphical user interface), and the like, and a scan converter (not shown), and the like.

The ultrasonic measurement unit 10 has the same configuration as a known ultrasonic imaging apparatus, and includes a transmission BF unit 11 for performing beam forming of a transmission signal for transmitting an ultrasonic wave of a predetermined frequency from the ultrasonic probe 80 to a target internal region of an inspection target, a reception BF unit 12 for receiving an ultrasonic signal which is a reflected wave from the internal region of the inspection target and performing amplification/equalization processing, a transmission/reception switching unit 13 for switching transmission/reception, and the like. Some of these elements may be provided in the ultrasonic probe 80 (probe).

The image generating unit 20 acquires the ultrasonic signal from the reception BF unit 12, performs luminance conversion, frequency analysis, and the like to generate an image to be displayed on the display unit 60, and includes a signal processing unit 21, a tomographic image calculating unit 23 that generates image data such as a B-mode image, and the like.

The image processing unit 30 generates an image after image processing by performing processing such as noise removal and edge enhancement on the image (tomographic image) generated by the image generating unit 20, and includes a noise removing unit 31 that removes noise of an ultrasonic image, a morphological processing unit 33 that morphologically processes the noise-removed image generated by the noise removing unit 31, and a coordinate transforming unit 32 that transforms coordinates of image data, and further, the image processing unit 30 of the present embodiment includes: and a structural element specifying unit 35 that specifies a value of a structural element used for morphological processing using the noise-removed image. The coordinate transformation unit 32 transforms the coordinates of the image from polar coordinates (r- θ coordinates) having the depth direction r of the ultrasonic beam as the vertical axis and the angular direction θ as the horizontal axis into coordinates (x-y orthogonal coordinates) in real space. The coordinate conversion unit 32 may be located at a stage before the noise removal unit 31 or may be located at a stage after the morphological processing unit 33.

The main functions of the control unit 40 and the image processing unit 30 in the ultrasonic imaging apparatus described above can be realized by a computer having a CPU, a GPU, and a memory, but a part or all of the functions of the image processing unit 30 may be realized by a computer different from the ultrasonic imaging apparatus, and the present invention also includes such an embodiment. Further, a part of functions realized by software of the computer may be realized by hardware such as ASIC and FPGA.

Fig. 2 shows an outline of the processing of the ultrasonic imaging apparatus having the above-described configuration. As shown in the figure, if the reception BF unit 12 receives the ultrasonic signal via the ultrasonic probe 80, the image generation unit 20 stores the signal of 1 frame as image data in the memory (S21). Image data of 1 to a plurality of frames are accumulated in the memory, and the memory is updated every time a frame is updated.

When the image data of each frame is input to the image processing unit 30, the image processing unit 30 performs noise removal processing on the input image data (S22), and performs morphological processing using an adaptive structural element in which a structural element value is determined, on the basis of the noise-removed image (S23, S24). The adaptive structural element is a structural element that is applied while changing at least one of a value and a size of the structural element in accordance with a pixel position of an image to be processed. By performing such morphological processing, an image with clear tissue structure without pseudo-emphasis of speckle is obtained. The morphologically processed image data is converted into real space coordinates (x-y coordinates) by the coordinate conversion unit 32 (S25), converted into a display image by the scan converter 70, and displayed on the display unit 60 together with additional information such as imaging conditions and subject information (S26).

In fig. 2, although step S24 of specifying the structural element is shown before morphological processing S25, step S24 may be performed during morphological processing S25.

In fig. 2, the case where the process S25 of converting the image coordinates is performed after the morphological process is illustrated, but the image conversion process S25 may be performed before the noise process, or may be performed before the noise process and after the morphological process.

Hereinafter, the configuration of the image processing unit 30 and the respective embodiments of the image processing method will be described based on the configuration and operation of the ultrasonic imaging apparatus.

< first embodiment >

The present embodiment is characterized in that: the structural element specifying unit 35 specifies the value of the structural element using the result of the morphological first operation.

As shown in fig. 3, the image processing unit 30 of the present embodiment includes a morphological processing unit 33 including a first computing unit 33A that performs at least one of expansion and erosion using a first structural element and a second computing unit 33B that performs at least one of opening and closing using a second structural element, and a structural element specifying unit 34 specifies a value of a second structural element used in the second computing unit 33B using a noise-removed image. In the present embodiment, the component specifying unit 35 is referred to as a component value specifying unit. Further, the image processing apparatus further includes a combining unit 37 for generating a morphologically processed output image using the processing results of the first and second arithmetic units 33A and 33B. Note that, in fig. 3, the coordinate conversion unit 32 is not shown.

As shown in fig. 4, the image processing unit 30 of the present embodiment acquires image data generated by the image generating unit 20, and sequentially performs noise processing (S22), first operation of morphological processing (S241), structural element identification (S23), second operation of morphological processing (S242), and synthesis processing (S243). In the morphological processing, structural elements are set adaptively to the image, and in the first calculation, dilation and erosion are performed, and in the second calculation, opening and closing are performed for 4 processes in total. In the structural element determining step, a structural element used for the second operation is determined.

The following describes the details of each process of the image processing unit 30.

[ noise removal processing: s22)

Noise removal is performed on image data (original image) using a predetermined filter. As the noise removal filter, an edge preserving type smoothing filter that performs noise removal while suppressing blurring in the edge region is desirable. Specifically, the multi-resolution analysis may be particularly preferable, for example, a weighted average filter for weighted averaging the pixel values of a local region centered on a target pixel with a large weighting coefficient of the target pixel, a direction-dependent filter for detecting a directional component of a structure such as an edge and performing one-dimensional smoothing in the direction, or a multi-resolution analysis for expanding input image data according to a scaling function and expanding the result to a wavelet function of different resolutions.

Morphological processing (first operation): s241]

The noise-removed image data (noise-removed image) is subjected to respective processes of dilation and erosion. In this process, a structural element having a fixed size and a fixed value is used. The treatment contents are the same as those of the known expansion and erosion, and can be expressed by the formula (1) and the formula (2), respectively.

In the formula, f denotes image data as input data, x denotes a position in the image data, g denotes a structural element, and u denotes a position of the structural element, and symbols enclosing "+" and "-" with ○ denote operators of expansion and erosion processing of the image data f using the structural element g, respectively.

That is, as shown in fig. 5, for example, a structural element g (in the figure, the dimension is 3 × 3, the value is 1) having a fixed value is applied to each pixel of the input image f, and the pixel value of the pixel to be processed is determined according to the equations (1) and (2). by this, the value of the structural element of the corresponding pixel is added to the expansion, the maximum value is taken as the pixel value of the pixel to be processed, the value of the structural element of the corresponding pixel is subtracted from the erosion, and the minimum value is taken as the pixel value of the pixel to be processed.A one-dimensional graph as shown in fig. 6 shows the result of the expansion as a broken line in fig. 6 (b), and the result of the erosion as a dashed-dotted line, and the dimension of the structural element g is shown in the lower part of fig. 6 (a).

[ structural element determination: s23)

The structural element specifying unit 35 specifies the structural element used in the subsequent second calculation using the result of the first calculation. The structural element of the second operation is an adaptive structural element whose value is different depending on the position of the pixel to be processed, and the value of the structural element is determined so that the value is large in the edge region and small in the uniform region. Therefore, a difference is calculated between the result (output) Yd of expansion and the result (output) Ye of corrosion in step S241.

g′＝Yd-Ye (3)

As a result of the difference, as shown by a thick line in fig. 6 (b), the value becomes larger in the edge region, which is a region where the pixel value changes rapidly, and becomes smaller in the uniform region. In the present embodiment, the component g' having a value as a function of the difference as a component value is specified. The size of the structural element may be the same as or different from that of the structural element of the first calculation.

Morphological processing (second operation): s242)

Using the structural element g' determined in step S23, the expansion result and the corrosion result in step S241 are subjected to closing processing and opening processing, respectively. The open state is a process of performing the dilation after the erosion, and the closed state is a process of performing the erosion after the dilation, and can be expressed by the formula (4) and the formula (5) using an operator expressing the dilation and the erosion.

The example shown in fig. 6 (b) shows the results of opening and closing in fig. 6 (c) and (d), respectively. As shown in the figure, these processes are performed on both sides of the boundary region, so that the boundary region is steeper than the original image and the edge is emphasized.

In the present embodiment, the opening and closing using the structural element g used in the first calculation are performed separately from the opening and closing using the adaptive structural element g'. The result can be used in the subsequent synthesis process.

[ Synthesis treatment: s243

Finally, the combining section 37 combines the processing result of step S242 and the input image according to the formula (6).

f_out＝f+fο(g，g′)-fοg+f·(g，g′)-f·g (6)

The result of the synthesis is shown in fig. 6 (e).

In this example, the difference between the open result using the adaptive structural element g 'and the open result using the structural element g, and the difference between the closed result using the adaptive structural element g' and the closed result using the structural element g are added to the input image to obtain an output image. This can improve the edge enhancement effect and obtain an image with smoothed noise.

However, the method of synthesis is not limited to the formula (6), and for example, only the difference between the open result using the adaptive structural element g ' and the open result using the structural element g, only the difference between the closed result using the adaptive structural element g ' and the closed result using the structural element g may be added to the input image, or the open result using the adaptive structural element g ' and the closed result may be added without taking the difference.

The processing of the image processing section 30 (S23, S24 in FIG. 2) is completed through the above-described steps S241 to S243. The synthesized image is displayed on the display unit 60 or stored in the storage unit 50 as an output image.

The effect of the present embodiment will be described with reference to fig. 7. Fig. 7 (a) is a diagram schematically showing an input image. When the morphological processing is directly applied to the input image and the edge is emphasized, the edge portion is also emphasized as shown in fig. 7 (b), but when there is a spot that is not suitable for the structural element, the spot of the uniform portion (flat portion) may be simultaneously emphasized. Therefore, even if smoothing such as noise removal is performed thereafter, a pseudo-emphasized patch remains, and cannot be distinguished from a boundary of a tissue or the like. In contrast, in the present embodiment, as shown in fig. 7 (c) and (d), since morphological processing is performed on the basis of the image after the noise removal processing (fig. 7 (c)), an image in which only the edge to be emphasized is emphasized can be obtained (fig. 7 (d)).

Fig. 8 shows an image (a) obtained by performing the processing according to the present embodiment on an image actually acquired by an ultrasonic imaging apparatus, and an image (b) obtained by performing morphological processing without performing noise removal processing. As can be seen from this figure, by performing the processing of the present embodiment, it is possible to clearly distinguish between the tissue in the center of the image and the tissue in the periphery of the image while removing the speckle.

As described above, according to the present embodiment, by performing morphological processing using adaptive structural elements on an image in which an original image has been subjected to noise removal processing, it is possible to achieve sufficient noise removal for a uniform region and obtain a high edge enhancement effect for an edge region. This can prevent the image quality from being degraded by speckle noise.

< second embodiment >

In the first embodiment, the value of the adaptive structural element used for morphology is determined using the morphological first calculation result, but in the present embodiment, structural elements different in size in accordance with the position are determined and used.

In general, since morphological processing has a function of smoothing components in the structural elements, it is preferable to set the size of the structural elements to a size corresponding to the size of the patches. The size of the patch differs for each image depending on the kind of the ultrasonic probe used for imaging, the frequency of the ultrasonic signal, imaging conditions, and the like. In addition, the size of the speckle also varies depending on the depth, sampling interval, and the like, and therefore varies depending on the position even within the same image. In the present embodiment, speckle noise is effectively removed by determining the size of the structural element in accordance with the imaging conditions.

The configuration of the image processing unit of the present embodiment is basically the same as that of the image processing unit of the first embodiment, but a size specification unit 39 is added as shown in fig. 9. In fig. 9, the same elements as those in fig. 3 are denoted by the same reference numerals, and redundant description thereof is omitted. In fig. 9, the coordinate conversion unit 32 is not shown.

As shown in fig. 10, the image processing unit 30 of the present embodiment acquires ultrasound image data (S41), acquires information (e.g., imaging parameters) necessary for determining the size of a structural element to be used for the subsequent morphological processing (S42), and determines the size (S43). Then, noise removal processing, morphological processing (first operation, second operation) (S44), and image conversion processing are performed.

The following describes the processing of the size determination unit 39, which is a feature of the present embodiment.

The size specifying unit 39 acquires information on the resolution of an image and a sampling interval according to imaging conditions and the like when acquiring image data, the resolution of the image differs depending on the depth and orientation, and is determined by conditions such as an ultrasonic probe, a frequency, a focal position, and an imaging mode, and the relationship between the depth and the resolution is obtained in advance for each type of the ultrasonic probe and imaging conditions by sound field numerical calculation, image simulation, actual measurement, and the like, and the resolution can be obtained from the depth determined by the parameters of the image.

The sampling interval is the distance in real space of the data interval adjacent on the input image (of the r-theta coordinate system or the x-y coordinate system), and this information can be directly obtained from the input image. For example, when the input image is an r- θ coordinate system (before coordinate conversion) and the data interval in the θ direction on the input image is 1 degree, the sampling interval Δ s in the θ direction at which r is 30mm is set to be

Δs＝30[mm]×(1/180×π)＝0.5[mm]。

If the resolution is R and the sampling interval is Δ s, the size determination unit 39 determines the size N of the structural element, for example, according to the following equation (7).

N＝R/Δs (7)

The resolution R varies depending on the position of the pixel, and therefore the size can be changed in accordance with the pixel position, but a statistical value such as the maximum value, the minimum value, or the average value of "R/Δ s" obtained for all pixels may be calculated, and any one may be determined as the size of the structural element. Alternatively, all pixels may be divided into a plurality of groups according to the value of "R/Δ s", and an average value of "R/Δ s" (═ N) of each group may be calculated, for example, and the average value may be set as the size N of the structural elements applied to each group. Instead of the average value, the maximum value and the minimum value may be applied.

The determined dimensions of the structural elements may be applied to the structural elements used in both the first and second operations of the morphological processing. The morphological operation is the same as that of the first embodiment. The first arithmetic unit 33A of the morphological processing expands and erodes the noise-removed image using the structural elements of the size determined by the size determination unit 39. Next, the second arithmetic unit 33B performs opening and closing using the structural elements of the size determined by the size determination unit 39. Finally, the open/close result and the input image are synthesized according to the above formula (6).

Alternatively, when the structural element value specifying process (S23) of the first embodiment is not performed, one of the expansion result Yd and the erosion result Ye obtained by the first calculation may be weighted and selected for each pixel so as to be close to the original image, and the selected one may be combined.

The value of the structural element used for each calculation may be a fixed value, or may be different depending on the position. When the image processing unit 30 of the present embodiment includes the same structural element specifying unit 35 as the image processing unit 30 of the first embodiment, as shown in fig. 11, a structural element g '(S23) whose value changes depending on the position of the pixel may be specified using the difference between the expansion result Yd and the corrosion result Ye in the first operation (S241) of the morphological processing, and the second operation (S242) may be performed using such an adaptive structural element g'. In this case, as shown in equation (6), the difference between the open result using the same structural element g as the first operation and the open result using the adaptive structural element g 'and the difference between the close result using the same structural element g as the first operation and the close result using the adaptive structural element g' are added to the noise-removed image, and the final image is created.

In the present embodiment, the process of converting the image coordinates may be performed either before or after the morphological process. When image conversion is performed after morphological processing, the resolution for determining the size of the structural element is a value of the resolution of the r- θ coordinate.

According to the present embodiment, in addition to the effect of edge emphasis and smoothing in which the false emphasis of the speckle is prevented by performing the morphological processing on the noise-removed image in the same manner as in the first embodiment, the edge emphasis of the edge region and the smoothing of the uniform region can be appropriately performed with the influence of the speckle noise minimized by using the structural elements having the size corresponding to the speckle size for the morphological processing, and an image with good image quality can be obtained.

Further, according to the present embodiment, when the adaptive structural element (the structural element that changes the value in accordance with the position) of the first embodiment is used, the edge enhancement effect in the edge region and the smoothing in the uniform region can be further improved. However, the present embodiment also includes a case where such an adaptive structural element is not used.

In the first and second embodiments, the ultrasonic image to be subjected to the image processing may be not only a B-mode image but also a THI (tissue harmonic image), a tomographic image including blood flow information, or the like.

< third embodiment >

The present embodiment is characterized in that: a configuration is added in which the user can select the determination of the value and size of the structural element. Therefore, as shown in fig. 1, the ultrasonic imaging apparatus according to the present embodiment includes, for example, a UI (user interface) unit in the control unit 40.

The UI unit displays a Graphic UI (GUI) selectable by the user on the display unit 60, accepts operations such as keys on the GUI in accordance with operations of an input device such as a mouse, a keyboard, or a touch panel provided in the input unit 70, and specifies processing of the image processing unit 30 in accordance with the accepted user instruction.

Fig. 12 shows an example of the GUI. In this example, a selection is received from the user as to whether or not the morphological processing of the first embodiment or the second embodiment is performed on the noise-removed image. Specifically, the screen 600 of the display unit 60 includes an image display block 610 for displaying an image, a parameter display block 620 for displaying imaging conditions and parameters, and a receiving unit 630 for displaying keys operable by the user. For example, if a noise-removed B-mode image is displayed on the image display block 610, the user operates the switch key for the edge enhancement processing displayed on the receiving unit 630 to turn "off" when determining that sufficient information for diagnosis is obtained from the image or when determining that further image processing is not desired. When it is determined that the edge enhancement processing is necessary, the edge enhancement processing is set to on. Thus, the morphological processing unit 33 performs, for example, morphological processing according to the first embodiment on the noise-removed image, and displays the resulting image on the image display block 610. In this case, the noise-removed image before the processing and the processed image may be displayed in parallel.

Further, an adjustment dial or an adjustment bar for adjusting the degree of "smoothing" (L evel: horizontal) may be provided, and the size of the structural element may be adjusted in accordance with the degree of smoothing received.

According to the present embodiment, the degree of freedom of the processing can be increased by the user, and more appropriate image processing can be performed by comparing the degree of adjustment before and after the edge enhancement processing.

< fourth embodiment >

The present embodiment is an embodiment in which the configuration of the image processing unit of each of the above embodiments is specifically applied to an ultrasound imaging apparatus that inserts a puncture needle into an examination subject and captures an auxiliary image of a path for guiding the puncture needle.

In an ultrasound imaging apparatus in which a puncture instrument is displayed on a screen together with a biological tissue, the puncture needle is recognized by drawing the puncture needle as a point having a relatively higher brightness than the biological tissue on an ultrasound image, but the puncture needle inserted into the living body sometimes has insufficient recognizability because a reflected wave from the needle returns in a direction opposite to the direction of an incident wave. Therefore, when performing puncture under ultrasound guidance, noise removal and edge enhancement based on adaptive structural elements using the result are applied to the input image, thereby obtaining an ultrasound image in which speckle noise is reduced and the edge component of the puncture needle is clearer.

That is, the ultrasound imaging apparatus of the present embodiment is an ultrasound imaging apparatus that images an auxiliary image of a path through which a puncture needle is guided, and includes: an ultrasonic measurement unit that transmits ultrasonic waves to an inspection object and receives ultrasonic waves as reflected waves to acquire ultrasonic signals; an image generating unit that generates an ultrasonic image of the inspection object using the ultrasonic signal acquired by the ultrasonic measuring unit; and an image processing unit that processes the ultrasonic image created by the image creating unit. The image processing unit includes: a noise removing unit that removes noise from the ultrasonic image created by the image creating unit; a morphological processing unit that performs morphological processing on the noise-removed image generated by the noise removing unit; and a structural element specifying unit that specifies a value of a structural element used in the morphological processing unit using the noise-removed image, wherein an auxiliary image in which a boundary between the puncture needle and the other tissue is emphasized is generated.

The configurations of the ultrasonic measurement unit, the image generation unit, and the image processing unit (noise removal unit, morphological processing unit, and structural element identification unit) are the same as those of the ultrasonic imaging apparatus according to the first embodiment, and the flow of image processing is the same as that described with reference to fig. 4. The image processing unit may include a size determination unit 39 (fig. 9) for determining the size of the structural element in accordance with the imaging conditions (resolution and sampling interval of the image), and the flow of the image processing in this case may be the same as that described with reference to fig. 10 or 11. Further, a known puncture needle enhancement process using a direction-dependent smoothing process or the like may be added as necessary.

According to the present embodiment, by applying the image processing according to the present invention to the ultrasound imaging apparatus for assisting puncture guide, it is possible to provide an ultrasound image in which the edge component of the puncture needle is clearer, and it is possible to improve the needle visibility at the time of puncture.

Although the embodiments of the ultrasonic imaging apparatus and the image processing method according to the present invention have been described above, the present invention may include some of the elements described in the embodiments omitted or a known configuration added thereto.