阅读说明：本技术 超声波解析装置、超声波解析方法及存储介质 (Ultrasonic analysis device, ultrasonic analysis method, and storage medium ) 是由 喜屋武弥 黑木裕士 中川泰彰 向井章悟 于 2019-06-06 设计创作，主要内容包括：提供一种不伴有被辐射而对软骨下骨的病变进行评价的超声波解析装置、超声波解析方法及存储介质。超声波解析装置(3)连接在收发装置(2),该收发装置(2)朝向处于被检体(9)的内部的包括软骨下骨(94)在内的骨及软骨发送超声波、接收从被检体(9)的内部反射的回波信号,超声波解析装置(3)具备：图像数据生成部(331),根据回波信号生成超声波图像数据；表面位置检测部(332),根据超声波图像数据检测软骨下骨(94)的表面位置；区域设定部(333),以软骨下骨(94)的表面位置为基准,在超声波图像数据中设定解析对象的区域；以及特征量计算部(334),计算区域中的纹理特征量。(provided are an ultrasonic analysis device, an ultrasonic analysis method, and a storage medium, which evaluate a lesion in subchondral bone without being accompanied by irradiation. An ultrasonic analysis device (3) is connected to a transmission/reception device (2), the transmission/reception device (2) transmitting ultrasonic waves to bones including subchondral bone (94) and cartilage in a subject (9) and receiving echo signals reflected from the inside of the subject (9), the ultrasonic analysis device (3) comprising: an image data generation unit (331) that generates ultrasound image data from the echo signal; a surface position detection unit (332) that detects the surface position of the subchondral bone (94) from the ultrasonic image data; an area setting unit (333) that sets an area to be analyzed in the ultrasound image data, with the surface position of the subchondral bone (94) as a reference; and a feature value calculation unit (334) for calculating a texture feature value in the region.)

1. An ultrasonic analysis device connected to a transmission/reception device that transmits ultrasonic waves to a bone and a cartilage including a subchondral bone inside a subject and receives an echo signal reflected from the inside of the subject, the ultrasonic analysis device being characterized in that,

the disclosed device is provided with:

An image data generating unit that generates ultrasonic image data from the echo signal;

A surface position detecting unit that detects a surface position of the subchondral bone based on the ultrasonic image data;

an area setting unit that sets an area to be analyzed in the ultrasonic image data with reference to the surface position of the subchondral bone; and

And a feature amount calculation unit for calculating the texture feature amount in the region.

2. An ultrasonic analysis apparatus according to claim 1,

The texture feature amount includes at least one of entropy and correlation in texture analysis of the image data.

3. An ultrasonic analysis apparatus according to claim 2,

The region setting unit sets a plurality of the regions so as to be adjacent to each other in a direction along a sound axis of the ultrasonic wave from the surface position of the subchondral bone;

The feature value calculation unit calculates the texture feature value for each of the plurality of regions.

4. an ultrasonic analysis apparatus according to claim 3,

The regions include a 1 st region corresponding to a superficial portion of the subchondral bone and a 2 nd region located deeper than the 1 st region.

5. An ultrasonic analysis apparatus according to claim 4,

The thickness of the 1 st region along the direction is in the range of 0.3mm to 0.45 mm;

the thickness of the 2 nd region along the direction is in the range of 0.3mm to 0.45 mm.

6. An ultrasonic analysis apparatus according to claim 4 or 5,

The feature value calculation unit calculates the entropy for the 1 st region and calculates the correlation for the 2 nd region.

7. The ultrasonic analysis apparatus according to any one of claims 1 to 6,

The image data generating unit rearranges the ultrasonic image data so that the surface of the subchondral bone is flat.

8. The ultrasonic analysis apparatus according to any one of claims 1 to 7,

The image processing apparatus further includes an output unit that outputs the texture feature amount.

9. An ultrasonic analysis method is characterized in that,

The method comprises the following steps:

Transmitting ultrasonic waves to a bone including subchondral bone and cartilage in an object and receiving an echo signal reflected from the inside of the object;

Generating ultrasonic image data from the echo signal;

Detecting a surface position of the subchondral bone from the ultrasonic image data;

Setting a region to be analyzed in the ultrasonic image data based on the surface position of the subchondral bone; and

And calculating the texture feature quantity in the region.

10. A storage medium characterized in that,

The storage medium stores an ultrasonic analysis program for causing a computer connected to a transmission/reception device that transmits ultrasonic waves to bones including subchondral bone and cartilage in a subject and receives echo signals reflected from the inside of the subject to execute:

Generating ultrasonic image data from the echo signal;

Detecting a surface position of the subchondral bone from the ultrasonic image data;

Setting a region to be analyzed in the ultrasonic image data based on the surface position of the subchondral bone; and

And calculating the texture feature quantity in the region.

Technical Field

the present invention relates to an ultrasonic analysis device, an ultrasonic analysis method, and an ultrasonic analysis program for analyzing the inside of a subject by ultrasonic waves.

Background

osteoarthritis (OA) is a disease in which a joint is deformed due to wear of cartilage, inflammation occurs in the joint, or pain occurs. If osteoarthritis develops, the natural smooth motion of the joint is impeded and the range of motion is also limited. In particular, if cartilage of the knee joint is worn, it is difficult to perform daily operations such as standing up and walking, and the quality of life is significantly reduced.

As an apparatus for analyzing the state of cartilage, for example, there is an ultrasonic analysis apparatus described in patent document 1. The ultrasonic analysis device described in patent document 1 transmits an ultrasonic signal from an ultrasonic probe in contact with the surface of the knee, and receives an echo signal reflected inside the knee by the ultrasonic probe. The ultrasonic analysis device analyzes the state of the cartilage from the received echo signal.

In recent years, attempts have been made to evaluate lesions of subchondral bone located in a lower layer of cartilage in order to find osteoarthritis at an early stage. From measurements performed by an X-ray Micro CT (Micro-CT, Micro computer tomography) device, it is known that a change occurs in the microstructure of a bone as a lesion of subchondral bone associated with osteoarthritis. Examples of the micro CT parameters of the subchondral bone indicating the change in the microstructure of the bone include the porosity in the subchondral bone plate, the thickness of the subchondral bone, and the bone density in the cancellous bone region. As a technique for evaluating the subchondral bone based on the amplitude of the echo signal of the ultrasonic probe, for example, the techniques of non-patent documents 1 and 2 are known.

Disclosure of Invention

Problems to be solved by the invention

Measurements made by X-ray CT are accompanied by irradiation of the joints. The measurement by the ultrasonic probe is not accompanied by irradiation of the joint, but the absolute amplitude of the ultrasonic wave from the cartilage-subchondral bone boundary is affected by attenuation in the upper tissues such as cartilage and soft tissues located above the subchondral bone, and therefore, the absolute amplitude is insufficient as a parameter reflecting the lesion of the subchondral bone in terms of accuracy. In addition, if the ultrasonic wave amplitude from the cartilage-subchondral bone boundary as the average value is considered in consideration of the ultrasonic wave attenuation amount in the upper tissue, it is considered that the amplitude is suitable as a parameter reflecting the lesion of the subchondral bone, but is not an optimal parameter reflecting the distribution characteristics of the microstructure of the bone such as the cancellous bone region located further below the subchondral bone.

The invention provides an ultrasonic analysis device, an ultrasonic analysis method and an ultrasonic analysis program for evaluating a lesion of a subchondral bone without being accompanied by irradiation.

Means for solving the problems

an ultrasonic analysis device according to the present invention is an ultrasonic analysis device connected to a transmission/reception device that transmits ultrasonic waves to a bone and a cartilage including a subchondral bone inside a subject and receives an echo signal reflected from the inside of the subject, the ultrasonic analysis device including: an image data generating unit that generates ultrasonic image data from the echo signal; a surface position detecting unit that detects a surface position of the subchondral bone based on the ultrasonic image data; an area setting unit that sets an area to be analyzed in the ultrasonic image data with reference to the surface position of the subchondral bone; and a feature amount calculation unit that calculates a texture feature amount in the region.

According to the ultrasonic analysis device of the present invention, it is possible to evaluate a lesion in subchondral bone without being accompanied by irradiation. The texture feature amount calculated by the ultrasonic analysis device for the subchondral bone region reflects the change in the microstructure of the bone (cancellous bone). Thus, the user can evaluate the lesion of the subchondral bone based on the texture feature amount, and can find osteoarthritis at an early stage.

The ultrasonic analysis method according to the present invention includes: transmitting ultrasonic waves to a bone including subchondral bone and cartilage in an object and receiving an echo signal reflected from the inside of the object; generating ultrasonic image data from the echo signal; detecting a surface position of the subchondral bone from the ultrasonic image data; setting a region to be analyzed in the ultrasonic image data based on the surface position of the subchondral bone; and calculating the texture feature amount in the region.

An ultrasonic analysis program according to the present invention causes a computer connected to a transmission/reception device that transmits ultrasonic waves to a bone and a cartilage including a subchondral bone in a subject and receives an echo signal reflected from the inside of the subject to execute: generating ultrasonic image data from the echo signal; detecting a surface position of the subchondral bone from the ultrasonic image data; setting a region to be analyzed in the ultrasonic image data based on the surface position of the subchondral bone; and calculating a texture feature amount in the region. The ultrasonic analysis program according to the present invention may be recorded on a non-transitory computer-readable tangible recording medium such as a CD-ROM.

Effects of the invention

according to the present invention, it is possible to provide an ultrasonic analysis device, an ultrasonic analysis method, and an ultrasonic analysis program for evaluating a lesion of a subchondral bone without being accompanied by irradiation.

Drawings

Fig. 1 is a block diagram of an ultrasonic analysis system according to an embodiment of the present invention.

Fig. 2 is a diagram schematically showing an internal structure of a knee as a subject and an ultrasonic probe.

Fig. 3 is a functional block diagram of the signal processing section.

Fig. 4 is a diagram schematically illustrating a method of detecting the surface position of subchondral bone using an amplitude intensity image.

fig. 5 is a diagram schematically showing two-dimensional amplitude intensity images (regions deeper than the subchondral bone surface) aligned on the subchondral bone surface.

Fig. 6 is a flowchart showing a flow of processing relating to the ultrasonic analysis method of the present embodiment.

Fig. 7 is a diagram schematically showing a three-dimensional amplitude intensity image aligned on the subchondral bone surface.

description of the reference symbols

1 ultrasonic analysis system; 2, a transceiver; 3 an ultrasonic analysis device; 4, a driving mechanism; 9 a subject; 21 an ultrasonic probe; 22 a pulse generator/receiver; 23 a conversion unit; 31 an input section; 32 a control unit; 33 a signal processing unit; 34 an output unit; 51 analyzing the target region (surface layer portion); 52 analyzing the target region (deep part); 91 cartilage; 92 bone (cancellous bone); 93 soft tissue; 94 subchondral bone; 95 knee surface; 331 an image data generating unit; 332 a surface position detecting section; 333 region setting unit; 334 feature amount calculating unit.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description and the drawings, the same reference numerals denote the same or similar components, and thus, redundant description of the same or similar components will be omitted.

In an embodiment of the present invention described below, the inside of a human knee is used as an analysis target as an example of a subject, and a two-dimensional cross-sectional image of the inside of the knee is acquired as an ultrasonic image used for the analysis. Further, amplitude intensity data of the ultrasonic echo signal is acquired as data representing the ultrasonic image. In addition, the embodiments of the present invention described below are examples, and in the present invention, the joints of the subject are not limited to the knee, the ultrasound image is not limited to the two-dimensional cross-sectional image, and the data representing the ultrasound image is not limited to the amplitude intensity data.

Fig. 1 is a block diagram of an ultrasonic analysis system 1 according to an embodiment of the present invention. Fig. 2 is a diagram schematically showing an internal structure of a knee as a subject and an ultrasonic probe.

An ultrasonic analysis system 1 according to an embodiment of the present invention includes a transmission/reception device 2, an ultrasonic analysis device 3 connected to the transmission/reception device 2, and a drive mechanism 4. The drive mechanism 4 can have any configuration according to the configuration of the transmission/reception device 2.

The transmission/reception device 2 is a device that transmits ultrasonic waves to bones including subchondral bones and cartilage inside the subject 9 and receives echo signals reflected from the inside of the subject 9, and includes an ultrasonic probe 21, a pulse generator/receiver 22, and an a/D conversion unit 23.

The ultrasonic probe 21 is a single-element probe in the present embodiment, and mechanically scans one-dimensionally (in the x direction or y direction shown in fig. 2) along the surface of the knee as the subject 9. In the present embodiment, it is assumed that the ultrasonic probe 21 is scanned in the x direction shown in fig. 2. The transducer transmits ultrasonic waves from the surface of the subject 9 toward the inside of the subject 9 at predetermined time intervals. The transmitted ultrasonic wave is reflected inside the subject 9, and the transducer receives the reflected echo signal.

As shown in fig. 2, the ultrasonic probe 21 has an end surface on the transmission/reception surface side brought into contact with the knee surface 95 (the surface of the soft tissue 93), transmits ultrasonic waves from the end surface on the transmission/reception surface side, and searches the interior of the knee. The soft tissue 93 is a part present on the front surface side of the subject 9 with respect to the cartilage 91. Cartilage 91 is attached to subchondral bone 94 to be analyzed, and subchondral bone 94 is a tissue that is bonded to bone (spongy bone) 92. In the following description, the direction from the knee surface 95 toward the inside of the bone 92 side is referred to as the depth direction, and the depth direction is the z direction (the direction orthogonal to the x direction and the y direction) described above in the orthogonal coordinate system. In addition, the position in the depth direction z may be represented by a distance traveled by the ultrasonic wave traveling inside the subject 9 within the time t. The transformation between the depth direction z and the time t may be performed using, for example, an assumed sound velocity of 1540m/s for the soft tissue 93 and an assumed sound velocity of 1620m/s for the cartilage 91.

The ultrasonic waves transmitted in the depth direction from the transducers of the ultrasonic probe 21 are reflected by the inside of the subject 9 (for example, by the soft tissue 93, the bone 92, or the like). The transducer of the ultrasonic probe 21 receives the reflected echo signal. The ultrasonic analysis device 3 generates amplitude intensity data D (ultrasonic image) of the inside of the subject 9 including the subchondral bone 94 and the like based on the echo signal received by the ultrasonic probe 21. The ultrasonic analysis device 3 outputs an ultrasonic image indicating the amplitude intensity of the echo signal to the output unit 34 and the like, and enables the user to confirm the state of the subchondral bone 94 in the image.

The pulse generator/receiver 22 generates a transmission pulse by shaping a transmission waveform composed of frequencies of an ultrasonic frequency band into a pulse shape, and outputs the generated transmission pulse to the ultrasonic probe 21. Thereby, the ultrasonic wave is transmitted from the transducer of the ultrasonic probe 21 in the depth direction of the subject 9. The pulse generator/receiver 22 receives an echo signal from the inside of the subject 9 received by the transducer of the ultrasonic probe 21.

the a/D converter 23 performs analog-to-digital conversion on the echo signal transmitted from the pulse generator/receiver 22, and transmits the converted signal to the ultrasonic analysis device 3.

The ultrasonic analysis device 3 includes an input unit 31, a control unit 32, a signal processing unit 33, and an output unit 34.

In the present embodiment, the ultrasonic analysis device 3 is configured by a well-known personal computer, and includes, as a hardware configuration, a processor such as a CPU that performs data processing, a memory used by the processor in a data processing work area, a recording unit that records processed data, a bus that transfers data between the respective units, and an interface unit (hereinafter, referred to as an I/F unit) that performs input and output of data with an external device. As an optional function, the ultrasonic analysis device 3 may be connected to an external server via a network such as the internet.

The input unit 31 receives an input from a user. For example, the input unit 31 may be constituted by a keyboard, a mouse, a touch panel, or the like.

In the present embodiment, the functional blocks of the control unit 32 and the signal processing unit 33 are realized by software by a processor executing a computer program recorded in advance in a recording unit or a memory, but may be realized by hardware by a logic circuit formed on an integrated circuit.

The control unit 32 is a functional block that controls the operation of the entire ultrasonic analysis system 1. For example, when receiving an instruction to execute the ultrasonic analysis processing from the user via the input unit 31, the control unit 32 transmits a control signal to the transmission/reception device 2, the ultrasonic analysis device 3, and the drive mechanism 4, and controls the operations of these respective units. Each unit connected to the control unit 32 operates in conjunction with an instruction from the control unit 32.

the signal processing unit 33 is a functional block that takes in the echo signal converted into a digital format from the transmission/reception device 2, executes various processes described later, and outputs a texture feature amount in the region to be analyzed. The details of the signal processing unit 33 will be described later with reference to fig. 3.

The output unit 34 outputs the texture feature value output from the signal processing unit 33. For example, the output unit 34 may be constituted by a monitor, a printer, or the like.

The drive mechanism 4 receives a control signal from the control unit 32 and mechanically scans the ultrasonic probe 21.

Fig. 3 is a functional block diagram of the signal processing unit 33. The signal processing unit 33 includes an image data generating unit 331, a surface position detecting unit 332, an area setting unit 333, and a feature value calculating unit 334.

The image data generation unit 331 generates ultrasound image data US inside the subject 9 based on the echo signal data generated by the transmission/reception device 2. In the present embodiment, the ultrasonic image data US (x, z) is amplitude intensity data D (x, z) of the echo signal. The amplitude intensity data D (x, z) shows the intensity of the amplitude of the echo signal for each coordinate indicated by the depth direction z and the scanning direction x inside the subject 9.

The image data generation unit 331 performs discrete data conversion by sampling the data of the echo signal transmitted from the a/D conversion unit 23 at predetermined time intervals. The echo signal after the discrete data processing is echo data. This makes it possible to obtain echo data obtained by sampling data at predetermined intervals in the depth direction of the subject 9. Further, the image data generation unit 331 generates amplitude intensity data D (x, z) by applying envelope detection processing and log compression processing to the obtained echo data. The generated amplitude intensity data D (x, z) is recorded in, for example, a recording unit.

In the present embodiment, the image data generator 331 can perform rearrangement processing of the amplitude intensity data D (x, z). The thicknesses of the soft tissue 93 and the cartilage 91 are different for each part of the knee joint, and the depth from the knee surface 95 to the surface position of the subchondral bone 94 is also different for each position in the scanning direction x. The image data generation unit 331 rearranges the amplitude intensity data D (x, z) so that the surface of the subchondral bone 94 is flat, based on the surface position of the subchondral bone 94 detected by the surface position detection unit 332 to be described later. By rearranging the amplitude intensity data D (x, z) based on the thicknesses of the soft tissue 93 and the cartilage 91 that vary for each part of the knee joint, the user can evaluate the lesion of the subchondral bone based on the analysis result with higher accuracy. Further, since the coordinates in the depth direction of the amplitude intensity data D (x, z) are changed by the rearrangement processing, the amplitude intensity data after rearrangement is expressed as the amplitude intensity data D (x, z'). Similarly, the rearranged ultrasonic image data is expressed as ultrasonic image data US (x, z').

The surface position detector 332 detects the surface position of the subchondral bone 94 in the z direction along the x direction, which is the scanning direction of the ultrasonic probe 21, from the generated amplitude intensity data D (x, z). The surface position of the subchondral bone 94 is the boundary position between the cartilage 91 and the subchondral bone 94. A method of detecting the surface position of the subchondral bone 94 in the z direction corresponding to the x direction will be described below.

Fig. 4 is a diagram schematically illustrating a method of detecting the surface position of subchondral bone using an amplitude intensity image. In the present embodiment, the surface position detection unit 332 detects the surface position of the subchondral bone 94 in the depth direction by creating a cost map (costmap) by the method described below using the amplitude intensity data D (x, z). As shown in fig. 4, the surface position detector 332 sets 2 regions Nfw and Nbw adjacent to each other in the depth direction. Region Nbw is located on the skin side in the depth direction, and region Nfw is located further inward (bone 92 side) than region Nbw. The size of the set regions Nfw and Nbw may be changed as appropriate.

Each of the regions Nfw and Nbw includes a plurality of amplitude intensity data D (x, z). First, the surface position detecting unit 332 calculates the average value of the amplitude level for each of the regions Nfw and Nbw from the amplitude intensity data D (x, z) in the regions Nfw and Nbw. Next, the surface position detector 332 subtracts the average value of the amplitude levels in the region Nbw from the average value of the amplitude levels in the region Nfw, and records the calculation result as a cost value in a recording unit, for example. The surface position detection unit 332 generates a cost map by repeating the process of calculating the cost value while changing the positions of the regions Nfw and Nbw in the depth direction, and records the generated cost map in, for example, a recording unit.

When transmitting ultrasonic waves to the knee as the subject 9, the ultrasonic waves are not reflected by the soft tissue 93 and the cartilage 91, and the obtained echo signals are minute or none. On the other hand, the amplitude of the echo signal reflected by the subchondral bone 94 increases. Therefore, for example, when one of the 2 regions Nfw, Nbw is located in the subchondral bone 94, the difference in the average value of the amplitude levels is large. In contrast, when both of the 2 regions Nfw and Nbw are not located in the subchondral bone 94, the difference in the average amplitude level is small. Using this characteristic, the surface position detection unit 332 detects the positions of the regions Nfw, Nbw having a large difference in amplitude level as the surface position of the subchondral bone 94 in the depth direction from the cost map recorded in the recording unit.

Further, in the present embodiment, the region setting unit 333 sets the region to be analyzed in the amplitude intensity data D (x, z) with reference to the surface position of the subchondral bone 94.

fig. 5 is a diagram schematically showing two-dimensional amplitude intensity images (regions deeper than the subchondral bone surface) aligned on the subchondral bone surface. Fig. 5 shows analysis target regions 51 and 52 for which texture feature values are to be calculated.

In the present embodiment, the region setting unit 333 sets a plurality of analysis target regions having a predetermined thickness in a direction along the acoustic axis of the ultrasound from the surface position of the subchondral bone 94. In the present embodiment, as shown in fig. 5, a 1 st region 51 corresponding to the surface layer portion of the subchondral bone 94 and a 2 nd region 52 located deeper than the 1 st region 51 are set.

An exemplary thickness of the 1 st region 51 is preferably in a range of approximately 0.3mm to approximately 0.45 mm. If 3635m/s (cortical bone sound velocity) is used as the value of the assumed sound velocity, the time t for the ultrasonic echo to travel is preferably approximately 0.15 μ s to approximately 0.25 μ s. Further, an exemplary thickness of the 2 nd region 52 is preferably in a range of approximately 0.3mm to approximately 0.45 mm. If 2500m/s (average bone marrow sound velocity) is used as the value of the assumed sound velocity, the time t for the ultrasonic echo to travel is preferably in the range of approximately 0.25 μ s to approximately 0.35 μ s. The thicknesses of the set 1 st region 51 and 2 nd region 52 can be changed as appropriate.

The feature value calculation unit 334 performs texture analysis of the amplitude intensity image, and calculates a texture feature value for the region to be analyzed set by the region setting unit.

The texture feature value is a value representing a feature regarding the texture (texture) of an image as an object. In the present embodiment, texture feature quantities based on a Gray Level Co-occurrrence Matrix (GLCM) are calculated. Examples of the texture feature include Entropy (Entropy), Correlation (Correlation), variance (SumVariance), Contrast (Contrast), and Average (sumaverage). These texture feature amounts can be calculated from image data, for example, by referring to 3 documents (Albregtsen 2008, Conners, et al 1984, Haralick, et al 1973) exemplified below. Further, as a well-known software module for calculating the texture feature amount from the image data, MATLAB (registered trademark) provided by MathWorks (registered trademark) corporation in the united states, for example, can be cited.

the exemplary documents are:

Albregtsen F.，“Statistical texture measures computed from gray level coocurrence matrices”，Image Processing Laboratory，Department of Informatics，University of Oslo，2008；5.

Conners RW，Trivedi MM，Harlow CA.，“Segmentation of a high－resolution urban scene using texture operators，Comp Vis Graph Image Process、1984，Vol.25，pp273－310.

Haralick RM，Shanmugam K，Dinstein IH.，“Textural features for image classification”，Systems Man Cybernetics IEEE Transactions，1973，pp610－21.

In the present embodiment, the entropy and correlation (correlation) among these various texture feature amounts are calculated. The feature value calculation unit 334 calculates the entropy ENT for the 1 st region 51 in the amplitude intensity data D (x, z)_L1And related COR_L1For region 2, the entropy ENT is calculated_L2And related COR_L2。

The entropy represents an information amount of the target image as a texture feature amount, and the correlation represents a correlation between a plurality of pixels adjacent to each other in the target image. In the amplitude intensity data D (x, z), the meaning of these texture feature quantities is as follows.

That is, in the region to be analyzed in the amplitude intensity data D (x, z), the change in the entropy value reflects the change in the porosity, and the change in the correlation value reflects the continuity of the echo signal. More specifically, the entropy ENT of the 1 st region 51_L1an increase in (b) indicates an increase in the porosity of the superficial portion of the subchondral bone 94. Correlation COR of region 2 52_L2a decrease in (b) indicates an increase in the thickness of the subchondral bone plate and an increase in the bone density of the cancellous bone region located posterior to the deep portion of the subchondral bone 94.

These texture feature quantities reflect changes in the microstructure of the bone (cancellous bone) 92. Thus, the user can evaluate the lesion of the subchondral bone 94 based on the texture feature amount, and can find osteoarthritis at an early stage.

Fig. 6 is a flowchart showing a flow of processing in the ultrasonic analysis method according to the present embodiment.

In the present embodiment, when the control unit 32 receives an instruction to start the analysis process via the operation of the input unit 31, the ultrasonic analysis system 1 executes the process shown in fig. 6.

In step S1, the transmission/reception device 2 transmits an ultrasonic wave from the transducer of the ultrasonic probe 21, and receives an echo signal reflected inside the subject 9 by the transducer of the ultrasonic probe 21. The transceiver 2 digitally converts the received echo signal and transmits the converted echo signal to the signal processing unit 33 of the ultrasonic analyzer 3.

When transmitting the ultrasonic waves into the subject 9, it is preferable that the contact angle (angle of the acoustic axis) of the ultrasonic probe 21 is adjusted so that the ultrasonic probe 21 contacts the knee surface 95 so that the acoustic axis of the ultrasonic waves is substantially perpendicular to the surface of the cartilage 91 or the surface of the subchondral bone 94 or within a predetermined angle range.

In step S2, the image data generator 331 of the signal processor 33 generates amplitude intensity data D (x, z) (i.e., the ultrasonic image data US (x, z)) from the echo signal, and records the generated amplitude intensity data D in, for example, a recording unit.

In step S3, the surface position detector 332 detects the surface position of the subchondral bone 94 using the amplitude intensity data D (x, z) generated in step S2. First, the surface position detection unit 332 creates a cost map (costmap) using the amplitude intensity data D (x, z), and records the created cost map in, for example, a recording unit. Next, the surface position detection unit 332 detects a position where the difference in amplitude level is large as the surface position of the subchondral bone 94 based on the created cost map, and records the detected surface position of the subchondral bone 94 in, for example, a recording unit.

In step S4, the image data generator 331 rearranges the amplitude intensity data D (x, z) so that the surface of the subchondral bone 94 is flat, based on the surface position of the subchondral bone 94 detected in step S3. The rearranged amplitude intensity data D (x, z') is recorded in, for example, a recording unit.

In step S5, the region setting unit 333 sets a region to be analyzed in the amplitude intensity data D (x, z') with reference to the surface position of the subchondral bone 94. As an example of the regions to be analyzed, as illustrated in fig. 5, the 1 st region 51 corresponding to the surface layer portion of the subchondral bone 94 and the 2 nd region 52 located deeper than the 1 st region 51 are illustrated.

In step S6, the feature value calculator 334 performs texture analysis of the amplitude intensity data D (x, z'), and calculates a texture feature value for the region to be analyzed set in step S5. The texture feature amount calculates at least one of entropy and correlation in texture analysis of the image data.

In step S7, the output unit 34 outputs the calculated texture feature amount. Preferably, the output unit 34 outputs (for example, displays on a monitor in a superimposed manner) the texture feature amount in association with the amplitude intensity data D (x, z') together with the information of the region to be analyzed, as illustrated in fig. 5, for example. Further, the output unit 34 preferably outputs a standard value of the texture feature amount measured in advance together with the texture feature amount of the subject 9 calculated in step S6 (for example, the standard value and the calculated texture feature amount are displayed in a line on the same screen). The standard value of the texture feature value is obtained by measuring in advance the normal subject 9 for which it is confirmed that no lesion has occurred in the subchondral bone 94, and may be recorded in advance in a recording unit, for example. The user can grasp that the porosity of the surface portion of the subchondral bone increases according to the increase in entropy, and can grasp that the bone density of the cancellous bone region located behind the surface portion of the subchondral bone increases according to the increase in correlation.

As described above, according to the ultrasonic analysis device 3 of the ultrasonic analysis system 1 according to the present invention, it is possible to evaluate a lesion of the subchondral bone 94 without being accompanied by irradiation. The texture feature amount calculated by the ultrasonic analysis device 3 for the subchondral bone 94 region reflects the change in the microstructure of the bone (cancellous bone 92). Thus, the user can evaluate the lesion of the subchondral bone 94 based on the texture feature amount, and can find osteoarthritis at an early stage.

The present invention has been described above with reference to specific embodiments, but the present invention is not limited to the above embodiments.

In the above embodiment, the surface position detection unit 332 detects the surface position of the subchondral bone 94, but may detect the surface position of the cartilage 91 in addition to the surface position of the cartilage 94, thereby detecting the surface position of the subchondral bone 94 with higher accuracy. Inside the soft tissue 93 and inside the cartilage 91, the sound velocity is different. Thus, if the surface position of the cartilage 91 is detected, the surface position of the subchondral bone 94 can be detected using more accurate assumed sound velocity for each of the region of the soft tissue 93 and the region of the cartilage 91. As the assumed sound velocity inside cartilage 91, 1620m/s, for example, can be used. The method for detecting the surface position of cartilage 91 by surface position detector 332 is the same as the method for detecting the surface position of subchondral bone 94. That is, the surface position detecting unit 332 creates a cost map and detects the boundary position between the cartilage 91 and the soft tissue 93.

This is explained in detail with reference to fig. 4. The surface position detection unit 332 extracts and uses the amplitude intensity data D (x, z) included in the predetermined region from the recording unit. The predetermined region is a region having a thickness Th from the surface position of the subchondral bone 94 detected by the surface position detecting unit 332 toward the soft tissue 93 in the depth direction. Thickness Th is the maximum value of the thickness of the measurement site (cartilage 91) of a human that is generally assumed. Surface position detecting unit 332 determines the search range in the depth direction based on the maximum value of the thickness of cartilage 91 assumed. The surface position detection unit 332 sets 2 regions (for example, indicated by Cfw and Cbw) from the amplitude intensity data D (x, z) in the extracted region, as described with reference to fig. 4. The surface position detection unit 332 calculates the difference between the average values of the amplitude levels for each of the 2 regions Cfw and Cbw, and records the calculation result as data of the cost map in the recording unit.

As described above, the ultrasonic wave is not reflected by the cartilage 91, and the obtained echo signal is not small or absent. Thus, as in the method of detecting the surface position of the subchondral bone 94, the surface position detection unit 332 determines the positions of the regions Cfw, Cbw having a large difference in amplitude level as the surface position of the cartilage 91 in the depth direction from the cost map recorded in the recording unit.

further, it is also possible to perform more accurate estimation of the ultrasonic wave incident angle in consideration of the refraction of the ultrasonic wave in the 3-layer model of the soft tissue 93, the cartilage 91, and the subchondral bone 94, together with the detection of the surface position of the cartilage 91. The surface position detector 332 may estimate the incident angle of the ultrasonic wave, for example.

Furthermore, a region within a predetermined range of incident angles may be selected and used based on a directional characteristic (for example, -6 dB directional angle) determined by the sound field characteristic of the ultrasonic probe 21. For example, the surface position detector 332 calculates an angle between the normal direction of the surface of the cartilage 91 (or the surface of the subchondral bone 94) at the position at which the ultrasonic wave is transmitted and the acoustic axis of the ultrasonic wave. That is, the surface position detecting unit 332 calculates a normal vector at a surface position corresponding to the position at which the ultrasonic wave is transmitted, and calculates an angle formed by the calculated normal vector and the acoustic axis of the ultrasonic wave transmitted by the ultrasonic probe 21. The surface position detecting unit 332 calculates an angle θ x of the normal vector with respect to the depth direction z. The angle θ x is the angle of incidence of the acoustic axis of the ultrasound wave with respect to the cartilage surface (or subchondral bone surface). For example, the image data generation unit 331 selects data included in the amplitude intensity data D (x, z) within a range of the angle θ x within a range of-6 dB, for example, and uses the selected data as the amplitude intensity data D (x, z) with higher accuracy. The method of selecting a region within the range of the predetermined incident angle based on the directivity characteristics determined by the sound field characteristics of the ultrasonic probe 21 can be applied to the three-dimensional amplitude intensity data D (x, y, z') as described later.

Further, the characteristics of the sound field formed by the ultrasonic probe 21 may be corrected. For example, the basic acoustic characteristics of the ultrasonic probe 21 in a uniform medium such as water may be measured in advance, and characteristics in which the amplitude intensity or the echo spectrum changes depending on the depth may be excluded. This reduces the amplitude characteristic dependent on the measurement system.

in the above-described embodiment, the two-dimensional cross-sectional image is acquired as the amplitude intensity image used for the analysis, but a three-dimensional cross-sectional image may be acquired and analyzed. There are various methods for analyzing a three-dimensional sectional image.

Fig. 7 is a diagram schematically showing a three-dimensional amplitude intensity image aligned on the subchondral bone surface. For example, as shown in fig. 7, a plurality of two-dimensional amplitude intensity data D (x, z ') may be created by cutting out the acquired three-dimensional amplitude intensity data D (x, y, z') in parallel with the x-z 'plane, and the texture feature amount may be calculated by setting the region to be analyzed for each of the plurality of two-dimensional amplitude intensity data D (x, z') thus cut out. In this case, a region within a predetermined range of incident angles may be selected and used based on the directional characteristics determined by the sound field characteristics of the ultrasonic probe 21 as described above, using a two-dimensional sectional image as an example. That is, for example, the image data generating unit 331 selects, as the amplitude intensity data D (x, z ') with higher accuracy, data included in the range of the angle θ x within the range of-6 dB, for example, from among the amplitude intensity data D (x, z') for each of the plurality of two-dimensional amplitude intensity data D (x, z ') extracted from the three-dimensional amplitude intensity data D (x, y, z').

Further, for example, the plurality of two-dimensional amplitude intensity data D (x, z') may be cut out so as to pass through the y-axis in the figureAre superimposed and averaged in the direction, and the averaged two-dimensional amplitude intensity data D_AVE(x, z') the texture feature is calculated by setting the region to be analyzed. The direction of overlapping for averaging is not limited to the y-axis direction in the drawing. In this case, a region within a predetermined range of incident angles may be selected and used based on the directional characteristics determined by the sound field characteristics of the ultrasonic probe 21 as described above, using a two-dimensional sectional image as an example. That is, the averaged two-dimensional amplitude intensity data D_AVE(x, z'), for example, the image data generation unit 331 generates the amplitude intensity data D_AVE(x, z') selecting, as amplitude intensity data D of higher accuracy, data included in a range of an angle 0x in a range of-6 dB, for example_AVE(x, z') used.

There are various methods for acquiring a three-dimensional sectional image. For example, a single-element probe may be used, and the probe may be scanned in the x-direction and the y-direction by the drive mechanism 4. For example, a probe for a two-dimensional cross-sectional image may be used, and the probe may be scanned in the x direction or the y direction by the drive mechanism 4 so as to be orthogonal to the scanning direction of the probe. Further, for example, a configuration may be adopted in which a probe for three-dimensional imaging is used without using the drive mechanism 4.

In the above embodiment, 2 regions, i.e., the 1 st region 51 and the 2 nd region 52, are set in the direction along the acoustic axis of the ultrasonic wave as the regions to be analyzed, but the number of the regions to be analyzed is not limited to 2. At least 1 region to be analyzed may be set in the direction along the acoustic axis of the ultrasonic wave.

In the above embodiment, the 2 feature quantities of entropy and correlation are calculated as the calculated texture feature quantities, but the number of calculated texture feature quantities is not limited to 2. At least 1 texture feature amount may be calculated from the number of regions to be analyzed.

In the above embodiment, the two-dimensional cross-sectional image is acquired by mechanically scanning the single-element probe drive mechanism 4 in one dimension, but the configuration for acquiring the two-dimensional cross-sectional image is not limited to this. For example, a probe for a two-dimensional cross-sectional image having a plurality of transducers arranged in one direction (for example, the x direction shown in fig. 2) may be used. In this case, the drive mechanism 4 may be omitted from the configuration of the ultrasonic analysis system 1.

The image data generation unit 331 may further process the amplitude intensity data D (x, z), and in the subsequent process, use the amplitude intensity data D (x, z) subjected to the process exemplified below instead of the amplitude intensity data D (x, z).

For example, the image data generation unit 331 may generate the smoothed amplitude intensity data Dm (x, z) by taking a moving average of the amplitude intensity data D (x, z). Even when the continuity of the amplitude intensity data in the scanning direction and the depth direction is poor, the detection accuracy of the surface position of the subchondral bone 94 can be improved by the smoothing processing.

Further, the image data generation unit 331 may generate the amplitude intensity data Dcomp (x, z) in which the signal intensity exceeding a predetermined threshold level is suppressed to be equal to or lower than the threshold level, from the smoothed amplitude intensity data Dm (x, z). By this compression processing, unnecessary high echo amplitude such as noise can be suppressed.

In order to shorten the processing time of the calculation, the surface position detection unit 332 may remove the number of data from the amplitude intensity data D (x, z) and use the removed amplitude intensity data D (x, z) for analysis.

In the above embodiment, the surface position detection unit 332 detects the surface position of the subchondral bone 94 by setting the adjacent 2 regions Nfw and Nbw in the depth direction, but may detect the surface position of the subchondral bone 94 by using Dijkstra (Dijkstra)) method instead. For example, a case where position detection is performed in the order of a plurality of positions x1, x2, and x3 different from each other in the x direction is considered. For example, when the position detection is performed at the position x2, a predetermined range is set in the depth direction from the surface position of the subchondral bone 94 detected at the position x1 before the position, and the surface position of the subchondral bone 94 is detected within the set range. This can shorten the search time and suppress erroneous detection.

In the above embodiment, the ultrasonic analysis device 3 and the transmission/reception device 2 are directly connected, but they may be communicably connected by a wired or wireless network. Similarly, the drive mechanism 4 may be communicably connected to the ultrasonic analysis device 3 by a wired or wireless network.

In the above-described embodiment, the ultrasonic analysis device 3 is implemented as an integrated device, but the ultrasonic analysis device 3 need not be an integrated device, and a processor, a memory, a recording unit, and the like may be disposed in different places and connected by a wired or wireless network. The input unit 31 and the output unit 34 do not necessarily have to be disposed in the same place as the processor, the memory, the recording unit, and the like, and may be disposed in different places and communicably connected to each other by a wired or wireless network.

In the above embodiment, the respective functional blocks of the control unit 32 and the signal processing unit 33 of the ultrasonic analysis device 3 are executed by a single processor, but these functional blocks do not necessarily have to be executed by a single processor, and may be distributed by a plurality of processors. Instead of the processor, the processor may be processed by an fpga (field Programmable Gate array), or a gpu (graphics Processing unit), for example, may be used as an accelerator to assist the processor in parallel arithmetic Processing. That is, the processing performed by the processor means processing performed by the processor or the FPGA using an accelerator such as a GPU.

In the above-described embodiment, the amplitude intensity data D of the ultrasonic echo signal is acquired by using the ultrasonic probe 21, and the texture feature amount is calculated for the region of the analysis target set in the amplitude intensity data D. The texture feature amount may be calculated by setting a region to be analyzed in an ultrasonic image acquired in a mode other than the exemplified amplitude mode. Alternatively, although radiation is received to the joint, a two-dimensional or three-dimensional cross-sectional image of the joint may be acquired by X-ray CT without using the ultrasonic probe 21, and a region to be analyzed may be set to calculate the texture feature amount.