JPWO2014103512A1 - Soft tissue cartilage interface detection method, soft tissue cartilage interface detection device, and soft tissue cartilage interface detection program - Google Patents

Abstract

Non-invasive detection of an interface between soft tissue and cartilage accurately. Echo data is acquired in a first state and a second state (S101, S102). From the echo data of the first state and the second state, the echo data of the subchondral bone 911 in the first state and the second state is detected (S103). A movement vector of the subchondral bone echo data is detected from the subchondral bone echo data in the first state and the second state (S104). Based on the movement vector, alignment of sample data to be compared between the echo data in the first state and the echo data in the second state is performed (S105). A correlation coefficient between the echo data in the first state and the echo data in the second state that are the same comparison target sample positions by the alignment is calculated (S106). A region having a high correlation coefficient is defined as cartilage, and a region having a low correlation coefficient is determined as soft tissue, and these boundary surfaces are detected (S107). [Selection] Figure 4

Description

  The present invention relates to a soft tissue cartilage boundary detection method for detecting a boundary surface between cartilage and soft tissue with an ultrasonic wave from the outside.

  Conventionally, various devices for generating information for diagnosing the state of cartilage have been devised. For example, in the ultrasonic diagnostic apparatus of Patent Document 1, a probe that transmits and receives ultrasonic waves is brought into contact with the surface of the knee, and the state of the cartilage is diagnosed with an echo signal from the inside of the knee obtained by the probe. . That is, the ultrasonic diagnostic apparatus of Patent Document 1 diagnoses the state of cartilage noninvasively. And in the ultrasonic diagnostic apparatus of patent document 1, the cartilage is detected from the level (intensity) difference of the echo signal of a depth direction.

JP 2010-305 A

  However, in the apparatus and method of Patent Document 1, the cartilage surface is detected from the difference between the echo signal level of soft tissue (muscle or skin) and the echo signal level of cartilage. Therefore, if there is no difference in the level of the echo signal between soft tissue and cartilage, the cartilage surface cannot be detected accurately.

  In general, with conventional ultrasonic signals, the echo signal level does not change suddenly and accurately at the interface between the soft tissue and the cartilage surface, and there is no significant difference in the echo signal level at this interface. For this reason, the conventional method cannot accurately detect the cartilage surface.

  An object of the present invention is to provide a soft tissue cartilage interface detecting method capable of accurately detecting a soft tissue and cartilage surface interface non-invasively.

  The present invention relates to a soft tissue cartilage interface detecting method for detecting a soft tissue / cartilage interface and has the following features. The soft tissue cartilage boundary surface detection method includes a first echo signal transmission / reception step, a second echo signal transmission / reception step, a subchondral bone detection step, a movement vector detection step, and a boundary surface detection step.

  In the first echo signal transmission / reception step, an ultrasonic signal is transmitted into the body to be detected in the first state to obtain a first echo signal. In the second echo signal transmission / reception step, an ultrasonic signal is transmitted into the body to be detected in the second state to obtain a second echo signal.

  The subchondral bone detection step detects the subchondral bone echo signal in the first state from the first echo signal, and detects the subchondral bone echo signal in the second state from the second echo signal.

  The movement vector detection step detects a movement vector of the subchondral bone from the first state to the second state from the subchondral bone echo signal in the first state and the subchondral bone echo signal in the second state. .

  The boundary surface detection step detects the boundary surface between the soft tissue and the cartilage by correcting the sample positions of the echo signals in the first state and the second state based on the movement vector.

  This method utilizes the fact that the cartilage is attached to the subchondral bone, and the soft tissue is not attached to the cartilage and the soft tissue can slide on the cartilage surface.

  When a probe that transmits an ultrasonic signal is moved in contact with the body to be detected, soft tissue follows and cartilage and subchondral bone do not follow. Therefore, the position change of the subchondral bone with respect to the probe and the position change of the cartilage correspond to the movement vector, but these position changes do not match the position change of the soft tissue with respect to the probe. In addition, even if the detected body side where soft tissue, cartilage, and cartilage are bent is bent while the probe is in contact with the detected object, the change in the position of the subchondral bone relative to the probe and the change in the position of the cartilage are similar. The change in the position of the subchondral bone relative to the probe does not match the change in the position of the soft tissue.

  Therefore, if the sample position of the echo signal in the first state and the sample position of the echo signal in the second state are corrected by the movement vector, and the echo signal at each sample position is compared, the comparison result is soft tissue and cartilage (and Different from subchondral bone). By utilizing this different point, it is possible to distinguish soft tissue and cartilage and to detect the boundary surface between soft tissue and cartilage.

  In the soft tissue cartilage boundary surface detection method of the present invention, the subchondral bone detection step sequentially acquires the signal intensity of the first echo signal along the depth direction, and the signal intensity equal to or higher than the threshold for subchondral bone detection The signal in the range in which is detected is detected as a subchondral bone echo signal in the first state. The subchondral bone detection step detects the similarity between the subchondral bone echo signal in the first state and the second echo signal, and uses the echo signal having the highest similarity as the subchondral bone echo signal in the second state. To detect.

  In the soft tissue cartilage boundary surface detection method of the present invention, the subchondral bone detection step sequentially acquires the signal intensity of the first echo signal from the deep side along the depth direction, and is equal to or greater than the threshold for subchondral bone detection. A signal in a range where the signal intensity is detected is detected as a subchondral bone echo signal in the first state. The subchondral bone detection step detects the similarity between the subchondral bone echo signal in the first state and the second echo signal, and uses the echo signal having the highest similarity as the subchondral bone echo signal in the second state. To detect.

  These methods show specific detection methods for subchondral bone.

  According to the present invention, an ultrasonic signal is transmitted from the outside of a detected body such as a knee, and the boundary surface between the soft tissue and the cartilage surface is accurately detected while receiving the echo signal outside the detected body. Can do. Thereby, the echo from the cartilage can be accurately detected, and can be effectively used for diagnosis of cartilage.

1 is a block diagram showing a configuration of a soft tissue cartilage boundary detection device 10 according to an embodiment of the present invention. It is a figure which shows the installation aspect with respect to the to-be-detected body of the probe 100 of the soft tissue cartilage boundary detection apparatus 10 which concerns on embodiment of this invention. It is a figure for demonstrating the detection concept of the cartilage surface which concerns on embodiment of this invention. It is a flowchart of the soft tissue cartilage interface detection method which concerns on embodiment of this invention. It is a figure which shows the example of a waveform of each echo signal in 1st state [T1] and 2nd state [T2]. It is a wave form diagram for demonstrating the detection concept of the movement vector which concerns on this embodiment. It is a figure which shows the definition of the movement vector concerning this embodiment. It is a figure which shows the distribution state of the movement vector which concerns on this embodiment. FIG. 6 is a waveform diagram for explaining a method (first method) for detecting whether echo data belongs to cartilage 901 or soft tissue 903; FIG. 6 is a waveform diagram for explaining a method (second method) for detecting whether echo data belongs to cartilage 901 or soft tissue 903; It is a figure which shows the detection structure by the mechanical scan which moves a vibrator | oscillator.

  A soft tissue cartilage boundary surface detection method and a soft tissue cartilage boundary surface detection apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a soft tissue cartilage boundary detection apparatus 10 according to an embodiment of the present invention. FIG. 2 is a diagram showing an installation aspect of the probe 100 of the soft tissue cartilage boundary detection device 10 according to the present embodiment with respect to the detection target, and FIG. 2 (A) shows a case of the first state (t = T1), FIG. 2B shows the case of the second state (t = T2). In the following description, an example in which the probe 100 is moved has been shown, but the following method and configuration can also be applied when moving the detection target. For example, the present invention can be applied to a case where the probe 100 is brought into contact with and fixed to the knee, which is the detection target, and the knee is bent and stretched. In other words, any method and configuration that can change the positional relationship between soft tissue and cartilage in the first state [T1] and the second state [T2] can be applied.

  FIG. 3 is a diagram for explaining the detection concept of the soft tissue cartilage boundary surface according to the present embodiment. FIG. 3 (A) shows the first state [T1] (t = T1), and FIG. 3 (B). Indicates the second state [T2] (t = T2). FIG. 3 is a view in which the surface of an area where an ultrasonic signal is transmitted and the area in the vicinity thereof are replaced with a flat plane.

  The soft tissue cartilage boundary surface detection apparatus 10 includes an operation unit 11, a transmission control unit 12, an echo signal reception unit 13, a data analysis unit 14, and a probe 100. The transmission control unit 12, the echo signal receiving unit 13, and the probe 100 correspond to the “transmission / reception unit” of the present invention.

  The operation unit 11 receives a user operation input. For example, the operation unit 11 includes a plurality of operation elements (not shown), and instructs the transmission control unit 12 to start execution of processing for detecting the cartilage surface from a user operation on the operation elements.

  The transmission control unit 12 generates an ultrasonic signal obtained by shaping a carrier wave having an ultrasonic frequency into a pulse shape. The transmission control unit 12 generates an ultrasonic signal in each of the first state [T1] and the second state [T2].

  The transmission control unit 12 outputs an ultrasonic signal to the probe 100. The probe 100 includes a plurality of transducers arranged in a direction parallel to the transmission / reception surface (see FIG. 3). The direction in which the transducers are arranged is the scanning direction. Each transducer transmits an ultrasonic signal having a predetermined transmission beam angle toward the body to be detected. Each transducer transmits an ultrasonic signal at a predetermined time interval and receives the reflected echo signal.

  Specifically, as shown in FIG. 2, the probe 100 is arranged such that the end surface on the wave transmitting / receiving surface side is in contact with the surface of the soft tissue 903 of the knee that is the detection target. Here, as shown in FIG. 3, the soft tissue 903 is a part of the body including skin and muscles, and is a part that is present on the surface side of the body to be detected with respect to the cartilage 901. The cartilage 901 is attached to the subchondral bone 911, and the subchondral bone 911 is a tissue connected to the bone (cancellous bone) 902.

  While the probe 100 is in contact with the surface of the soft tissue 903 as shown in FIG. 2A, the probe 100 is moved along the surface as shown in FIG. Thereby, as shown in FIG. 2, the soft tissue 903 moves according to the probe 100 while sliding on the surface of the cartilage 901. The state of FIG. 2A before the probe 100 is moved is the first state (t = T1), and the state of FIG. 2B after the probe 100 is moved is the second state (t = T2). ). At this time, the probe 100 is moved along the arrangement direction (scanning direction) of the transducers.

  Each transducer transmits an ultrasonic signal toward the body to be detected in each of the first state [T1] and the second state [T1]. At this time, each transducer of the probe 100 transmits an ultrasonic signal so that the direction orthogonal to the surface of the soft tissue 903 is the direction of the central axis of the transmission beam.

  Each transducer of the probe 100 receives an echo signal in which the ultrasonic signal is reflected by the soft tissue 903, the cartilage 901, and the subchondral bone 911 in the body to be detected, and outputs the echo signal to the echo signal receiving unit 13. The probe 100 includes a first echo group SW [T1] composed of echo signals obtained by each transducer in the first state [T1] and a first echo group SW [T1] composed of echo signals obtained by each transducer in the second state [T2]. The two echo signal groups SW [T2] are output to the echo signal receiving unit 13, respectively.

  The echo signal receiving unit 13 performs a predetermined amplification process on each echo signal and outputs it to the data analysis unit 14. The echo signal receiving unit 13 individually amplifies each echo signal of the first echo group SW [T1] and each echo signal of the second echo group SW [T2], and outputs the amplified signal to the data analysis unit 14.

  The data analysis unit 14 includes an AD conversion unit 141, a storage unit 142, and a determination unit 143. The AD conversion unit 141 converts the echo signal into discrete data by sampling at predetermined time intervals. The echo signal converted into discrete data becomes echo data. Thereby, echo data sampled at predetermined intervals in the depth direction for each sweep can be obtained. That is, echo data distributed in a two-dimensional region in the scanning direction and the depth direction can be obtained. Hereinafter, this echo data group is simply referred to as two-dimensional distribution echo data. The AD conversion unit 141 outputs each echo data to the storage unit 142.

  The storage unit 142 stores each echo data output from the AD conversion unit 141. The storage unit 142 has a capacity for storing the two-dimensional distribution echo data obtained in the first state and the two-dimensional distribution echo data obtained in the second state.

  Although a specific processing method will be described later, the determination unit 143 detects the boundary surface between the soft tissue and the cartilage according to the flow shown in FIG. FIG. 4 is a flowchart of the soft tissue cartilage boundary surface detection method according to the embodiment of the present invention.

  The determination unit 143 reads and acquires the two-dimensional distribution echo data obtained in the first state and the two-dimensional distribution echo data obtained in the second state, which are stored in the storage unit 142 (S101). , S102).

  The determination unit 143 obtains echo data of the subchondral bone 911 in the first state (corresponding to the “subchondral bone echo signal in the first state” of the present invention) from the echo data of the two-dimensional distribution in the first state. To detect. The determination unit 143 obtains echo data of the subchondral bone 911 in the second state (corresponding to the “subchondral bone echo signal in the second state” of the present invention) from the two-dimensional distribution echo data in the second state. Detect (S103).

  The determination unit 143 detects a movement vector of the subchondral bone echo data from the subchondral bone echo data in the first state and the subchondral bone echo data in the second state (S104).

  The determination unit 143 aligns the sample data to be compared between the echo data of the two-dimensional distribution in the first state and the echo data of the two-dimensional distribution in the second state based on the movement vector (S105).

  The determination unit 143 calculates a correlation coefficient between the echo data in the first state and the echo data in the second state that become the same comparison target sample position by the alignment. Specifically, the determination unit 143 sets a comparison target region including a region having a predetermined width in the depth direction including the comparison target sample position. The determination unit 143 calculates a correlation coefficient between the waveform composed of the first state echo data in the comparison target region and the waveform composed of the second state echo data in the comparison target region (S106).

  The determination unit 143 detects a region where comparison target sample positions with a high correlation coefficient are gathered and a region where comparison target sample positions with a low correlation coefficient are gathered, and detects a boundary between these two regions (S107). .

  As described above, the cartilage 901 has the same movement mode as the subchondral bone 911, and the soft element 903 has a different movement mode from the subchondral bone 911. For this reason, after the alignment by the movement vector, the echo data of the soft tissue 901 having the same movement mode as the subchondral bone 911 has a high correlation coefficient. On the other hand, after the alignment by the movement vector, the echo data of the soft tissue 901 having a movement mode different from that of the subchondral bone 911 has a low correlation coefficient. Therefore, the boundary surface detected in step S107 is a boundary surface between the soft tissue 903 and the cartilage 901. As described above, the boundary surface between the soft tissue 903 and the cartilage 901 can be detected by using the above-described processing.

  When the surface of the cartilage 901 (the boundary surface between the soft tissue 903 and the cartilage 901) is detected, a cartilage diagnosis information generation unit (not shown) can be used for diagnosis of cartilage degeneration based on the cartilage 901 partial echo data. Generate information. Specifically, the information generation unit for cartilage diagnosis acquires a set of echo data near the cartilage surface and echo data of the subchondral bone at a plurality of different times. The cartilage diagnosis information generation unit may detect the amount of change due to the degeneration of the cartilage surface from the transition of the composition of these echo data sets in the time period. The cartilage diagnosis information generation unit outputs the detection result as information that can be used for diagnosis of cartilage degeneration.

  Next, the method for detecting the boundary surface between soft tissue and cartilage executed by the data analysis unit 14 will be described more specifically with reference to the drawings. In order to simplify the explanation, the movement distance Δx of the probe 100 (each transducer) between the first state [T1] and the second state [T2] matches the arrangement interval of the transducers. Will be described.

  First, as the first state [T1], for example, the probe 100 is brought into contact with the surface of the knee in a state where the knee as the detection target is bent at the first angle. In other words, the probe 100 is brought into contact with the surface of the soft tissue 903. This is the state of FIG.

  The plurality of transducers arranged on the probe 100 are arranged at predetermined intervals in a direction parallel to the surface of the soft tissue 903 (scanning direction parallel to the transmission / reception surface). The plurality of transducers transmit ultrasonic signals in a direction orthogonal to the scanning direction. In the example of FIG. 3, five transducers are arranged at equal intervals along the scanning direction in the probe 100, and as shown in FIG. The vibrator transmits an ultrasonic signal in a direction orthogonal to the surface of the soft tissue 903. The ultrasonic signals transmitted from the respective arrangement positions are reflected at respective depth positions of the soft tissue 903, the cartilage 901, and the subchondral bone 911, received by each transducer, and sampled by the data analysis unit 14. The echo data group of the echo data SWT11, SWT12, SWT13, SWT14, and SWT15 received in the first state [T1] becomes the first echo group SW [T1].

  Next, with the probe 100 kept in contact with the soft tissue 903, the probe 100 is moved by a distance Δx in a direction parallel to the surface of the soft tissue 903 and in a direction parallel to the scanning direction. This state is the second state [T2], which is the state shown in FIG.

  At this time, the soft tissue 903 moves following the movement of the probe 100. Therefore, the relative positional relationship between the wave transmitting / receiving surface of the probe 100 and each position in the scanning direction of the soft tissue 903 does not change without depending on the movement of the probe 100.

  On the other hand, since the cartilage 901 is fixed to the bone 902 through the subchondral bone 911, the cartilage 901 does not move even if the probe 100 moves. Accordingly, the relative positional relationship between the wave transmitting / receiving surface of the probe 100 and the positions of the cartilage 901 and the soft tissue 911 in the scanning direction changes according to the movement of the probe 100.

  After entering the second state, as shown in FIG. 3B, an ultrasonic signal is transmitted from each transducer of the probe 100 in a direction orthogonal to the surface of the soft tissue 903 (a direction orthogonal to the transmission / reception surface (scanning direction)). Send. The ultrasonic signals transmitted from the respective arrangement positions are reflected at respective depth positions of the soft tissue 903, the cartilage 901, and the subchondral bone 911, received by each transducer, and sampled by the data analysis unit 14. The echo data group of the echo data SWT21, SWT22, SWT23, SWT24, and SWT25 received in the second state [T2] becomes the second echo group SW [T2].

  As described above, the first echo group SW [T1] including the plurality of echo data SWT11, SWT12, SWT13, SWT14, and SWT15 is acquired before the probe 100 is moved. Then, after the probe 100 is moved, a second echo group SW [T2] including a plurality of echo data SWT21, SWT22, SWT23, SWT24, and SWT25 is acquired.

  FIG. 5 is a diagram illustrating examples of echo waveforms in the first state [T1] and the second state [T2]. In FIG. 5, the distance (movement amount) Δx that the probe 100 has moved is assumed to be equal to the interval between the transducers, that is, the interval between the scanning positions, in order to easily illustrate the features of the present invention. In the following, detection of the soft tissue cartilage boundary surface will be described under this condition.

  (I) Cartilage 901 and subchondral bone 911 Even if the probe 100 moves, the cartilage 901 and subchondral bone 911 do not move. Therefore, when the probe 100 moves by the distance Δx, the positional relationship between the position of each transducer of the probe 100 (each scanning position) and each position of the cartilage 901 and the subchondral bone 911 is the movement amount Δx along the scanning direction. Shift.

  In this case, as shown in each echo waveform in the first state [T1] and each echo waveform in the second state [T2] in FIG. 5, regions of the cartilage 901 and the subchondral bone 911 in the first echo group SW [T1] The echo data SWT11 of the second echo group SW [T2] does not match the waveforms of the cartilage 901 and subchondral bone 911 regions of the echo data SWT21 of the second echo group SW [T2], and the cartilage of the echo data SWT22 of the second echo group SW [T2] 901 and the subchondral bone 911 regions substantially match the waveform.

  Similarly, the waveforms of the cartilage 901 and subchondral bone 911 areas of the echo data SWT12 and the cartilage 901 and subchondral bone 911 areas of the echo data SWT23 substantially match. The waveforms of the cartilage 901 and subchondral bone 911 areas of the echo data SWT13 and the areas of the cartilage 901 and subchondral bone 911 areas of the echo data SWT24 substantially match. The waveforms of the cartilage 901 and the subchondral bone 911 in the echo data SWT14 and the areas of the cartilage 901 and the subchondral bone 911 in the echo data SWT25 are substantially the same.

  Therefore, within the cartilage 901 and the subchondral bone 911, the echo data at each scanning position is the movement amount Δx in the first state [T1] and the second state [T2], that is, the scanning position is the arrangement interval of the transducers. It is almost the same with the state shifted by one. That is, within the cartilage 901 and the subchondral bone 911, the sample position of each echo data based on the probe 100 changes by the movement amount Δx between the first state [T1] and the second state [T2]. Thus, the cartilage 901 and the subchondral bone 911 are in the same movement mode.

  (Ii) Soft Tissue 903 As described above, the probe 100 is in contact with the surface of the soft tissue 903, and the soft tissue 903 is not fixed to the surface of the cartilage 901. Therefore, when the probe 100 moves by the movement amount Δx, the soft tissue 903 also moves by the movement amount Δx following the movement of the probe 100.

  In this case, as shown in each echo waveform of the first state [T1] and each echo waveform of the second state [T2] in FIG. 5, the echo data SWT11 of the soft tissue 903 region of the first echo group SW [T1] is The waveform of the echo data SWT21 in the soft tissue 903 region of the second echo group SW [T2] is substantially the same.

  Similarly, the waveforms of the soft tissue 903 area of the echo data SWT12 and the soft tissue 903 area of the echo data SWT22 are substantially the same. The waveforms of the soft tissue 903 area of the echo data SWT13 and the soft tissue 903 area of the echo data SWT23 are substantially the same. The waveforms of the soft tissue 903 area of the echo data SWT14 and the soft tissue 903 area of the echo data SWT24 are substantially the same. The waveforms of the soft tissue 903 area of the echo data SWT15 and the soft tissue 903 area of the echo data SWT25 are substantially the same.

  Therefore, in the soft tissue 903, the echo data at each scanning position is substantially the same in the scanning direction with respect to the probe 100 in the first state [T1] and the second state [T2]. That is, in the soft tissue 903, the sample position of each echo data with the probe 100 as a reference does not change between the first state [T1] and the second state [T2]. For this reason, the movement mode of the echo data of the soft tissue 903 is different from the movement mode in which the sample position of the echo data changes according to the movement of the probe 100 such as the cartilage 901 and the subchondral bone 911 described above.

  As described above, the sample position with respect to the probe 100 of the echo data reflected at the specific position (the same in the first state [T1] and the second state [T2]) in the subchondral bone 911 and the cartilage 901 is the first state. [T1] and the second state [T2] move along the scanning direction by the movement amount Δx.

  On the other hand, the sample positions of the echo data reflected at a specific position in the soft tissue 903 (the same in the first state [T1] and the second state [T2]) as a reference are the first state [T1] and the second state. [T2] does not change.

  Using this characteristic, the soft tissue cartilage boundary surface detection apparatus according to the present embodiment detects the movement vector of the echo data of the subchondral bone 911 as shown in step S104 described above. Then, as shown in step S105 described above, this movement vector is used to align the sample position of the echo data in the first state [T1] and the sample position of the echo data in the second state [T2]. . In other words, the combination of the sample position of the echo data in the first state [T1] and the sample position of the echo data in the second state [T2] to be compared is determined.

  At this time, first, echo data of the subchondral bone 911 is detected as shown in step S103 described above. As shown in FIG. 4, the echo data of the subchondral bone 911 has a high echo level (amplitude). The echo level of the cartilage 901 is high on the cartilage surface, but the echo level is low in the region between the cartilage surface and the subchondral bone 911.

  Therefore, first, the echo levels of the echo data SWT11 to SWT15 of the first echo group SW [T1] are sequentially acquired along the depth direction. Then, it is detected that the echo level is lower than the subchondral bone detection threshold over a predetermined depth (appropriately set according to the thickness of the cartilage), and then an echo level equal to or higher than the subchondral bone detection threshold is detected. Thereby, the part after this sample position can be detected as echo data of the subchondral bone 911.

  Next, the acquisition of echo data of the subchondral bone 911 in the second state [T2] and the movement vector of the echo data of the subchondral bone 911 from the first state [T1] to the second state [T2] are detected. FIG. 6 is a waveform diagram for explaining the concept of detecting a movement vector according to the present embodiment. The waveform itself is the same as the waveform diagram of FIG.

A region of interest Z _T1CS is set for the echo data group of the subchondral bone 911 acquired in the first state [T1]. In this case, the attention area Z _T1CS is defined by the length in the depth direction (time direction). Specifically, for example, as shown in FIG. 6, in the two-dimensional area composed of the scanning direction and the depth direction determined by the respective echo data SWT11 to SWT15, in the depth direction (time direction) of one echo data. A predetermined range along is set as the attention area Z _T1CS . Next, the echo data included in the attention area Z _T1CS is extracted. In other words, this corresponds to the waveform of the echo data group cut out in the attention area Z _T1CS .

Next, the echo data SWT21-SWT25 the second echo group SW [T2], sets the search region _{Z R1.} The search area Z _R1 is determined so as to include echo data in a wider range than the attention area Z _T1CS with reference to the position of the attention area Z _T1CS with respect to the probe 100.

Specifically, in the second state [T2], the same position as the region of interest _ZT1cs is _set with respect to the probe 100 by a region expanded by a predetermined range in both the depth direction and the scanning direction with the center in the depth direction and the scanning direction. Is done. For example, as shown in FIG. 6, in the depth direction, when the center of the attention area Z _T1cs is set at the depth position P1cs of the echo signal SWT12, the search is performed at the depth position P1cs of the echo signal SWT22 in the second state [T2]. The center of the region Z _R1 is set. Then, a range longer than the depth direction length of the region of interest is set as the depth direction range of the search region _ZR1 . Incidentally, the depth position P1cs, if within the search region _{Z R1,} may not be the center of the search area _{Z R1.}

When the attention area Z _T1CS is set in the echo data SWT12 in the scanning direction, the search area Z _R1 is included so as to include the echo data SWT21, SWT22, and SWT23 so that the center in the scanning direction is the echo data SWT22. Set the range in the scanning direction.

Next, the lower bone comparison target region Z _T2CS is set for the echo data group of the subchondral bone 911 acquired in the second state [T2]. At this time, as shown in FIG. 6, the lower bone comparison target region _ZT2cs selects one echo signal and sets it as a region having a predetermined length in the depth direction. The depth direction length of the lower bone comparison target region Z _T2cs is set to match the depth direction length of the attention region Z _T1cs .

Comparison regions Z _T2CS for the lower bone is set to span the entire search area Z _R1 which is set as described above. Echo data is acquired for each lower bone comparison target region _ZT2CS set in this way.

Next, a correlation coefficient is calculated by performing a correlation process on the echo data of the attention area Z _{T1CS and} the echo data of the lower bone comparison target area Z _T2CS .

And echo data of the region of interest _{Z T1CS,} calculation of the correlation coefficient between the echo data of the comparison regions _{Z T2CS} for the lower bone, while sequentially changing the position of the comparison area _{Z T2CS} for the lower bone, the search area _{Z R1} Perform over the entire area.

The calculation of the correlation coefficients for such a region of interest Z _T1CS, be performed on the entire search area Z _R1.

Next, a correlation coefficient for each region of interest _{Z T1CS} detects a comparison regions _{Z T2CS} for the lower bone becomes maximum. This corresponds to the most similar region in the subchondral bone 911 region, and becomes echo data of the subchondral bone 911 in the second state [T2]. In this manner, the echo data of the subchondral bone 911 in the second state [T2] is detected from the similarity of the echo signals.

  Next, the movement vector (movement direction, movement amount) of the echo data of the subchondral bone 911 from the first state [T1] to the second state [T2] is detected.

Here, the movement vector can be defined as follows. FIG. 7 is a diagram showing the definition of the movement vector according to the present embodiment. FIG. 7 shows a case where the attention area and the lower bone comparison target area are used. Moving vector v _m is defined from the position of the representative point of the representative point and the lower bone for comparison regions of the region of interest is determined to be most similar to each other. Moving vector v _m as a starting point a representative point of the region of interest, a vector and terminating the representative point of the comparison regions for the lower bone, is defined by the moving direction and the moving amount.

  Specifically, for example, in the example of FIG. 7, the representative point of the region of interest exists on the echo signal SWT11, that is, at a predetermined depth position in the scanning direction position P1. In addition, the representative point of the lower bone comparison target region exists on the echo signal SWT22, that is, in the scanning direction position P2, at a predetermined depth position. The depth position of the representative point of the attention area is the same as the depth position of the representative point of the lower bone comparison target area.

In this case, the movement vector v _m is a vector in which the scanning direction is the movement direction and the distance Δx between the scanning positions P1 and P2 is the movement amount.

  Such movement vector calculation may be performed on all echo data of the subchondral bone 911 or may be performed on one or more representative echo data. When performing with all echo data or a plurality of echo data, the average of the movement vectors calculated for each may be used as the movement vector of the subchondral bone 911.

  When the movement vector is calculated in this way, the movement vector of each echo data of the cartilage 901 and the soft tissue 903 has a distribution as shown in FIG. FIG. 8 is a diagram showing a distribution state of movement vectors according to the present embodiment. As shown in FIG. 8, when the movement vector vm of the echo data in the subchondral bone 911 region is Δx, the movement vector vm of the echo data in the cartilage 901 region is also Δx. However, the movement vector vm of the echo data of the soft tissue 903 is 0, which is different from the movement vectors of the subchondral bone 911 and the cartilage 901.

  Using this characteristic, whether each echo data belongs to cartilage 901 or soft tissue 903 is detected by the following method. FIG. 9 is a waveform diagram for explaining a method (first method) for detecting whether echo data belongs to cartilage 901 or soft tissue 903.

A first comparison target area _ZT1n is set for the echo data group acquired in the first state [T1] (n is an integer determined from the number of sample positions along the depth direction). In this case, the first comparison target region _ZT1n is defined by the length in the depth direction (time direction). As a specific example, for example, as shown in FIG. 9, the depth direction (time direction) of one echo data with respect to a two-dimensional region composed of a scanning direction and a depth direction determined by each echo data SWT11-SWT15. ) _Is set to the first comparison target area _ZT11 . Next, the echo data included in the first comparison target area _ZT11 is extracted. In other words, this corresponds to the waveform of the echo data group cut out in the first comparison target area _ZT11 . Note that the first comparison target region _ZT11 may be set by excluding the region of the subchondral bone 911, and may be set by excluding the region of the cartilage 901 that is close to the subchondral bone 911 and has a low echo level.

Next, a second comparison target region _ZT2n is set for the echo data group acquired in the second state [T2] (n is an integer determined from the number of sample positions along the depth direction). In this case, the second comparison target region Z _T2n is set at a position where the first comparison target region Z _T1n is moved by the movement vector.

More specifically, it is the same as the first comparison target region Z _{T1n in} the second state [T2] by the same transducer that has obtained the echo data of the first comparison target region Z _T1n in the first state [T1]. Detect depth region. Then, the depth region in the second state [T2] obtained by moving this region with the movement vector is set as the second comparison target region _ZT2n . That is, the sample position of the echo data in the first state [T1] to be compared and the sample position of the echo data in the second state [T2] are aligned by the movement vector.

As a specific example, when the movement vector Δx that moves only in the scanning direction as described above is obtained, as shown in FIG. 9, the first state [T1] echo data SWT12 is set to a predetermined depth position P11. When one comparison region _{Z T11} is set at a predetermined depth position P21 of the echo data SWT23 moved by the movement vector Δx from the echo data SWT22 obtained in the second state [T2] of the same vibrator second comparison regions Z _T21 is set.

Similarly, as shown in FIG. 9, when the first comparison target region Z _T12 is set at the predetermined depth position P12 of the echo data SWT12 in the first state [T1], the same transducer causes the second state [T2]. the predetermined depth position P22 of the echo data SWT23 from echo data SWT22 obtained moved by movement vector Δx setting the second comparison regions _{Z T22.}

Next, a correlation coefficient between the echo data of the first comparison target region Z _{T1n and} the echo data of the second comparison target region Z _T2n is calculated.

Here, as described above, the cartilage 901 moves with the same movement vector as the subchondral bone 911, and the movement mode is the same. Therefore, the correlation coefficient between the echo data of the first comparison target region Z _{T1n and} the echo data of the second comparison target region Z _T2n aligned by the movement vector is approximately 1. That is, the correlation coefficient becomes high.

On the other hand, since the soft tissue 903 does not move in the same manner as the cartilage 901 and the subchondral bone 911, the movement mode is different. Therefore, the correlation coefficient between the echo data of the first comparison target region Z _{T1n and} the echo data of the second comparison target region Z _T2n aligned by the movement vector approaches zero. That is, the correlation coefficient is low.

For example, as shown in FIG. 9, the echo data of the first comparison target region _{ZT12 and} the echo data of the second comparison target region _ZT22 set in the cartilage 901 have the same waveform, and the correlation coefficient is high. On the other hand, the echo data of the first comparison target region Z _{T11 and} the echo data of the second comparison target region Z _T21 set in the soft tissue 903 have different waveforms, and the correlation coefficient is low.

  Thus, it can be determined that the echo data of the comparison target region having a high correlation coefficient is the echo data in the cartilage 901, and the echo data of the comparison target region having a low correlation coefficient is the echo data in the soft tissue 903. It can be judged.

Accordingly, by calculating the correlation coefficient between the echo data of the first comparison target region Z _T11 and the second comparison target region Z _T21 for each echo data other than the region of the subchondral bone 911, each echo is calculated. Whether the data is in soft tissue 903 or cartilage 901 can be detected. The boundary surface between the soft tissue 903 and the cartilage 901 can be detected by detecting the boundary between the echo data group determined to be within the soft tissue 903 and the echo data group determined to be within the cartilage 901.

  As described above, by using the configuration and processing of this embodiment, it is possible to accurately detect the boundary surface between soft tissue and cartilage in a non-invasive manner. As a non-invasive method, all echo data is set in a region of interest, a comparison target region having a high correlation coefficient is searched and detected in each region of interest, and the movement mode between the region of interest and the comparison target region It is also possible to detect the interface between soft tissue and cartilage. However, by using the configuration and processing of the present embodiment, it is not necessary to perform search processing for all regions, so that the boundary surface between soft tissue and cartilage can be detected at higher speed.

  In the above description, the example in which the sample area of the echo data acquired in the second state [T2] is moved by the movement vector to set the comparison target region is shown. However, the sample is acquired in the first state [T1]. The comparison target area may be set by moving the sample position of the echo data based on the movement vector.

  FIG. 10 is a waveform diagram for explaining a method (second method) for detecting whether echo data belongs to cartilage 901 or soft tissue 903. In the second method, the echo data acquired in the second state [T2] is used as a reference.

A second comparison target region _ZT2n is set for the echo data group acquired in the second state [T2] (n is an integer determined from the number of sample positions along the depth direction). As a specific example, for example, as shown in FIG. 10, the depth direction (time direction) of one echo data with respect to a two-dimensional region composed of a scanning direction and a depth direction determined by each echo data SWT21-SWT25. ) _Is set in the second comparison target area _ZT21 . Next, echo data included in the second comparison target region _ZT21 is extracted. In other words, this corresponds to the waveform of the echo data group cut out in the second comparison target region _ZT21 .

Next, the first comparison target region Z _T1n is set for the echo data group acquired in the first state [T1] (n is an integer determined from the number of sample positions along the depth direction). In this case, the first comparison target area Z _T1n is set to a position where the second comparison target area Z _T2n is moved in the direction opposite to the movement vector and according to the magnitude of the movement vector, based on the movement vector. .

More specifically, it is the same as the second comparison target region Z _{T2n in} the first state [T1] by the same transducer that has obtained the echo data of the first comparison target region Z _T2n in the second state [T2]. Detect depth region. Then, the depth region in the first state [T1] obtained by moving this region based on the movement vector is set as the first comparison target region _ZT1n . That is, the sample position of the echo data in the first state [T1] is aligned with the sample position of the echo data in the second state [T2] to be compared based on the movement vector.

As a specific example, when the movement vector Δx that moves only in the scanning direction as described above is obtained, as shown in FIG. 10, the second state [T2] echo data SWT22 in the predetermined depth position P21 When 2 comparison regions _{Z T21} is set, the first compared to a predetermined depth position P11 of the echo data SWT11 moved only in the opposite direction movement vector Δx from the echo data SWT12 which the same oscillator obtained in the first state [T1] The target area _ZT11 is set.

Similarly, as shown in FIG. 10, when the second comparison regions _{Z T22} is set to a predetermined depth position P22 of the echo data SWT22 the second state [T2], in the first state [T1] by the same oscillator from the echo data SWT12 obtained by the movement vector Δx sets a first comparison area _{Z T12} at a predetermined depth position P12 of the echo data SWT11 which moves in the opposite direction.

Next, a correlation coefficient between the echo data of the second comparison target region Z _{T2n and} the echo data of the first comparison target region Z _T1n is calculated.

  Even if such processing is performed, the boundary surface between the soft tissue and the cartilage can be accurately detected non-invasively.

In the above description, an example is shown in which soft tissue and cartilage are discriminated from the correlation coefficient between the echo data of the first comparison target region Z _{T1n and} the echo data of the second comparison target region _T1n . However, the similarity between the waveform of the echo signal of each sweep in the first state [T1] and the waveform of the echo signal of each sweep in the second state [T2] is detected by another method. And cartilage may be distinguished.

  As a specific example, there is a method using a norm. The norm Norm can be defined by the following equation.

Here, Ddzt1 (i) is an echo data value of a point at the position i in the depth direction of the first comparison target region _ZT1n . Ddzt2 (i) is the echo data value at the point in the depth direction position i of the second comparison regions _{Z T 2 n.} k corresponds to the resolution of the first comparison area _{Z T1n} and second comparison regions _{Z T 2 n,} the total number of echo data contained in the first comparison region _{Z T1n} and second comparison regions _{Z T 2 n.} m is an appropriately set constant.

In this way, the norm Norm _raises the absolute value of the difference between the echo data at the same position in the first comparison target region Z _T1n and the second comparison target region Z _T2n to the nth power, and adds the nth power value over the entire region. , 1 / nth power. Accordingly, a first comparison area _{Z T1n} and the second comparison region _{Z T 2 n} norm Norm higher similarity decreases, the more the norm Norm similarity is low is increased.

Accordingly, the first comparison target region Z _T1n and the second comparison target region Z _T2n having a small norm correspond to a case where the correlation coefficient is high, and can be determined to be within the cartilage 901. The first comparison target region Z _T1n and the second comparison target region Z _T2n having a large norm correspond to the case where the correlation coefficient is low, and can be determined to be in the soft tissue 903.

Such a method using the norm can also be used when detecting the movement vector of the subchondral bone 911. Specifically, to detect the most norm Norm small for the lower bone comparison regions _{Z T2CS} for the target region _{Z T1CS.} The movement vector can be detected by calculating a vector starting from the representative position of the attention area Z _T1CS of the combination having the minimum norm Norm and starting from the representative position of the lower bone comparison target area Z _T2CS. it can.

  In the above description, an example in which each process for cartilage surface detection is realized by a plurality of functional blocks is shown. However, the above-described cartilage surface detection process may be programmed and stored, and the program may be read and executed by a computer.

  In the above description, an example is shown in which the probe 100 is brought into contact with the surface of the soft tissue 903 of the knee, which is the detection target, and the probe 100 is moved in the scanning direction. However, the relative positional relationship between the probe 100 and the soft tissue 903, the cartilage 901, and the subchondral bone 911 may be changed by fixing the probe 100 and bending the knee with a jig or the like.

  In the probe described above, the transducers are arranged and arranged along only one direction of the scanning direction. However, the transducers may be arranged at a predetermined interval in a two-dimensional region of the scanning direction and the direction orthogonal to the scanning direction and the depth direction.

  Alternatively, a configuration may be adopted in which one transducer is used and the transducer is moved in the scanning direction. FIG. 11 is a diagram showing a detection configuration by mechanical scanning for moving the transducer.

  The mechanical scan type probe 100A includes a transducer having a transducer. The transducer is installed so as to be movable along the scanning axis. The transducer moves along the scan axis. The transducer of the transducer transmits an ultrasonic signal in a direction orthogonal to the scanning direction. While moving this transducer in the scanning direction, it stops at a plurality of scanning positions, transmits an ultrasonic signal, and receives the echo signal, thereby obtaining the same echo signal as the probe 100 having a plurality of transducers. be able to.

  In the above description, the case where each sample position of the cartilage 901 and the subchondral bone 911 with respect to the probe 100 is moved only in the scanning direction is described. Such a configuration and processing can be applied.

  In addition, as described above, the subchondral bone detection method in the first state [T1] is not limited to the method of comparing the echo level with the threshold value in order from the depth side, but the echo level is set in order from the depth side. A method of comparing with a threshold value may be used. Specifically, since the echo attenuation amount is large inside the bone inside the subchondral bone, the echo level is substantially zero. Therefore, the threshold value is set to a predetermined value larger than approximately zero. Then, the echo level is compared with a threshold value from the deep side, that is, the inside of the bone, and echo data at a position where the echo level is equal to or higher than the threshold value is acquired as echo data of the subchondral bone.

  In the above description, as an example of the subchondral bone detection method in the second state [T2], the similarity with the echo signal in the first state [T1] is used. However, the second state [T2] Similarly to the detection of the subchondral bone echo signal in the first state [T1], the subchondral bone echo signal may be compared with a threshold value.

10: soft tissue cartilage boundary surface detection device, 11: operation unit, 12: transmission control unit, 13: echo signal reception unit, 14: data analysis unit, 100, 100A: probe, 141: AD conversion unit, 142: storage unit, 143: determination unit, 901: cartilage, 902: bone, 903: soft tissue, 911: subchondral bone

Claims (17)

A soft tissue cartilage interface detection method for detecting a soft tissue / cartilage interface,
A first echo signal transmitting / receiving step of transmitting an ultrasonic signal in the detected body to obtain a first echo signal in the first state;
A second echo signal transmitting / receiving step of transmitting an ultrasonic signal into the body to be detected in the second state to obtain a second echo signal;
A subchondral bone detection step of detecting a subchondral bone echo signal in a first state using the first echo signal and detecting a subchondral bone echo signal in a second state using the second echo signal. When,
A movement for detecting a movement vector of the subchondral bone from the first state to the second state from the subchondral bone echo signal in the first state and the subchondral bone echo signal in the second state A vector detection process;
A boundary surface detection step of correcting a sample position of the echo signal of the first state and the second state based on the movement vector and detecting a boundary surface of the soft tissue and the cartilage;
A method of detecting a soft tissue cartilage boundary surface. The soft tissue cartilage boundary surface detection method according to claim 1,
The boundary surface detection step includes
With the movement vector, each sample position of the first echo signal is aligned with each sample position of the second echo signal,
Detecting an interface between the soft tissue and the cartilage based on an echo signal at the same sample position after alignment;
Soft tissue cartilage interface detection method. The soft tissue cartilage boundary surface detection method according to claim 2,
The boundary surface detection step includes
Detecting the similarity between the first echo signal and the second echo signal at each sample position after the alignment, and detecting the boundary surface from the similarity;
Soft tissue cartilage interface detection method. The soft tissue cartilage boundary surface detection method according to claim 3,
The boundary surface detection step includes
Calculating the correlation coefficient between the first echo signal and the second echo signal of the comparison target region including the sample position as the similarity, and detecting the boundary surface based on the correlation coefficient;
Soft tissue cartilage interface detection method. The soft tissue cartilage boundary surface detection method according to claim 3,
The boundary surface detection step includes
As the similarity, a norm is calculated from the first echo signal and the second echo signal of the comparison target region including the sample position, and the boundary surface is detected based on the norm.
Soft tissue cartilage interface detection method. The soft tissue cartilage boundary surface detection method according to any one of claims 1 to 5,
The movement vector detection step includes
Detecting a first subchondral bone echo signal using the first echo signal, detecting a second subchondral bone echo signal using the second echo signal;
Detecting a movement vector of the subchondral bone from the first state to the second state from the first subchondral bone echo signal and the second subchondral bone echo signal;
Soft tissue cartilage interface detection method. The soft tissue cartilage boundary surface detection method according to claim 6,
The movement vector detection step includes
Setting a region of interest for the first subchondral bone echo signal;
A lower bone comparison target region is set for the second subchondral bone echo signal,
Detecting the lower bone comparison target region having a high similarity to the attention region as a similar region, and detecting the movement vector from a positional relationship between the attention region and the similar region;
Soft tissue cartilage interface detection method. The soft tissue cartilage boundary surface detection method according to claim 7,
The movement vector detection step includes
For the second subchondral bone echo signal, set a lower bone search area larger than the region of interest, and set the lower bone comparison target area in the lower bone search area,
Soft tissue cartilage interface detection method. The soft tissue cartilage boundary surface detection method according to claim 7 or 8,
The movement vector detection step includes
Calculating the correlation coefficient of the first subchondral bone echo signal and the second subchondral bone echo signal as the similarity, and detecting the similar region based on the correlation coefficient;
Soft tissue cartilage interface detection method. The soft tissue cartilage boundary surface detection method according to claim 7 or 8,
The movement vector detection step includes
Calculating the norm of the first subchondral bone echo signal and the second subchondral bone echo signal as the similarity, and detecting the similar region based on the norm;
Soft tissue cartilage interface detection method. A soft tissue cartilage boundary surface detection method according to any one of claims 1 to 10,
The subchondral bone detection step includes
The signal intensity of the first echo signal is sequentially acquired from the surface side along the depth direction, and after detecting that the signal intensity is less than a subchondral bone detection threshold over a predetermined depth, the cartilage Detecting a signal in a range in which a signal intensity equal to or greater than a threshold value for detecting a lower bone is detected as a subchondral bone echo signal in the first state;
Detecting the similarity between the subchondral bone echo signal in the first state and the second echo signal, and detecting the echo signal having the highest similarity as the subchondral bone echo signal in the second state;
Soft tissue cartilage interface detection method. A soft tissue cartilage boundary surface detection method according to any one of claims 1 to 10,
The subchondral bone detection step includes
The signal intensity of the first echo signal is sequentially acquired from the deep side along the depth direction, and a signal in a range in which a signal intensity equal to or greater than the threshold value for detecting the subchondral bone is detected as the cartilage in the first state. Detect as lower bone echo signal,
Detecting the similarity between the subchondral bone echo signal in the first state and the second echo signal, and detecting the echo signal having the highest similarity as the subchondral bone echo signal in the second state;
Soft tissue cartilage interface detection method. A soft tissue cartilage interface detecting device for detecting an interface between soft tissue and cartilage,
In the first state, an ultrasonic signal is transmitted into the body to be detected and a first echo signal is output. The superposition is different in the second state in which the positional relationship between the soft tissue and the cartilage is different from the first state. A transmission / reception unit for transmitting a sound wave signal into the body to be detected and outputting a second echo signal;
Using the first echo signal to detect the subchondral bone echo signal in the first state, using the second echo signal to detect the subchondral bone echo signal in the second state, and A movement vector of the subchondral bone from the first state to the second state is detected from the subchondral bone echo signal in the first state and the subchondral bone echo signal in the second state; Based on this, the sample positions of the first echo signal and the second echo signal are corrected, and the interface between the soft tissue and the cartilage is detected from the corrected first echo signal and the second echo signal. A data analysis unit to
A soft tissue cartilage boundary surface detection device comprising: The soft tissue cartilage interface detecting device according to claim 13,
The transmission / reception unit includes a plurality of transducers arranged along a scanning direction,
Cartilage surface detection device. The soft tissue cartilage interface detecting device according to claim 13,
The transmission / reception unit includes a plurality of transducers two-dimensionally arranged in a region defined by the scanning direction and a direction orthogonal to the scanning direction and the transmission direction of the ultrasonic signal.
Soft tissue cartilage interface detection device. The soft tissue cartilage interface detecting device according to claim 13,
The transmission / reception unit includes a single vibrator and a moving mechanism that moves the vibrator in the scanning direction.
Soft tissue cartilage interface detection device. The soft tissue cartilage interface detecting device according to any one of claims 13 to 16,
The scanning direction is a direction in which the relative position of the soft tissue and the cartilage is changed.
Soft tissue cartilage interface detection device.

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