JP4716792B2 - Ultrasonic diagnostic equipment - Google Patents

Description

  The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to an ultrasonic diagnostic apparatus used for diagnosis of hard tissue such as bone.

  In order to diagnose bone metabolic diseases such as osteoporosis, determination of easy fracture, and quantitative diagnosis of bone healing after fracture treatment, simple and quantitative measurement of mechanical properties such as bone strength is desired. Yes.

  Evaluation of bone formation and bone union greatly depends on X-ray photographs, but it is difficult to quantitatively diagnose bone strength with X-ray photographs. Although a strength test of a sample bone to be measured is known as a conventional method for measuring bone strength, a sample bone removal operation is required and is invasive. Further, as a method for measuring bone mass and bone density, use of general-purpose X-ray CT, a DXA (dual energy absorption measurement method) apparatus, and the like have been put into practical use. However, these are merely means for measuring bone mass, and bone strength cannot be evaluated. Moreover, it cannot be said that it is noninvasive in the point which irradiates an X-ray.

  Other attempts to quantitatively evaluate bone strength include a strain gauge method in which a strain gauge is attached to an external fixator and the strain of the fixator is measured, and vibration that evaluates the natural frequency by applying external vibration to the bone. Examples of the existing method include a wave method and an acoustic emission method for detecting a sound wave generated from a bone having yield stress. However, these methods still have problems in terms of the limitation of applicable treatment methods, the need to invade bones, and evaluation accuracy.

  Against this background, the inventors of the present application have proposed an ultrasonic diagnostic apparatus that non-invasively and quantitatively evaluates the mechanical characteristics of bone (see Patent Document 1).

JP 2004-298205 A

  The ultrasonic diagnostic apparatus described in Patent Document 1 forms a plurality of ultrasound beams on a bone, acquires a plurality of echo signals corresponding to each ultrasound beam, and corresponds to the bone surface for each echo signal. A surface point to be identified is specified, and bone surface shape data is generated based on a plurality of surface points obtained from a plurality of echo signals. Then, the mechanical characteristics of the bone are evaluated based on the change in the shape data when an external action is applied to the bone. This is an epoch-making technique in which the mechanical characteristics of bone in a living body can be evaluated noninvasively and quantitatively from the shape data of the bone surface based on the echo signal.

  The inventors of the present application have further improved the epoch-making technique described in Patent Document 1 described above, and have been researching a technique for evaluating the mechanical properties of hard tissues such as bones with higher accuracy.

  The present invention has been made in such a background, and an object thereof is to provide an ultrasonic diagnostic apparatus capable of diagnosing hard tissue such as bone with higher accuracy.

  In order to achieve the above object, an ultrasonic diagnostic apparatus according to a preferred aspect of the present invention includes a wave transmitting / receiving unit that forms a plurality of ultrasonic beams on a hard tissue, and a surface point corresponding to the surface of the hard tissue. Surface detection means for detecting each ultrasonic beam and detecting a plurality of surface points from the plurality of ultrasonic beams, and displacement of the surface points when an external action is applied to the hard tissue for each ultrasonic beam A displacement measuring means for measuring a plurality of displacements corresponding to a plurality of surface points, and a characteristic evaluating means for evaluating the mechanical properties of the hard tissue based on the measured plurality of displacements. Features.

  In the above configuration, the displacement of the surface point is measured for each ultrasonic beam. For example, an echo tracking technique is used for detecting the surface point. For this reason, the surface point is accurately detected for each ultrasonic beam, and a minute movement (for example, several micrometers to several tens of micrometers) of the surface point can be measured. That is, in the above configuration, a plurality of displacements corresponding to a plurality of surface points are measured with high accuracy, and as a result, it becomes possible to evaluate mechanical characteristics of hard tissue such as bone with high accuracy.

  Incidentally, in the technique described in Patent Document 1, shape data of the bone surface is generated based on a plurality of surface points, and the mechanical characteristics of the bone are evaluated based on changes in the shape data. On the other hand, in the above configuration of the present application, in order to take advantage of the characteristics of the apparatus that can detect the surface point with high accuracy for each ultrasonic beam, the displacement of the surface point with high accuracy for each ultrasonic beam. After measurement, the mechanical properties are evaluated based on the multiple displacements measured with high accuracy. For this reason, in the said structure of this application, a mechanical characteristic can be evaluated with a still higher precision than the technique described in patent document 1. FIG.

  Desirably, the characteristic evaluation means includes a beam position of each ultrasonic beam and its ultrasonic beam in a coordinate system composed of an axis corresponding to the beam position of the ultrasonic beam and an axis corresponding to the displacement of the surface point. Based on a plurality of actual measurement points obtained as points corresponding to the measured displacement, an interpolation line connecting the plurality of actual measurement points is generated, and the mechanical characteristics are evaluated from the degree of bending of the interpolation line. It is characterized by that.

  Preferably, the characteristic evaluation means obtains a degree of bending of the interpolation line based on a comparison between a straight line connecting two end points of the plurality of measured points and the interpolation line. With this configuration, even when the surface of a hard tissue such as a bone is accompanied by an overall movement, a straight line connecting two end points of the measured points and the interpolation line are compared. You can cancel and know the degree of bending of the interpolation line. For example, even if there is an overall rotational component of the surface, the rotational component can be canceled.

  Preferably, the characteristic evaluation unit is configured as the mechanical characteristic based on a distance between a maximum displacement point, which is a point on the interpolation line existing at a position farthest from a straight line connecting the two end points, and the straight line. It is characterized in that the elastic amount of the bone is calculated. Preferably, the image forming apparatus further includes image forming means for forming an image obtained by combining the straight line connecting the two end points, the interpolation line, and the maximum displacement point.

  In order to achieve the above object, an ultrasonic diagnostic apparatus according to a preferred embodiment of the present invention includes a transmission / reception unit that forms a plurality of ultrasonic beams on a bone in a subject, and each ultrasonic beam. A surface point corresponding to the bone surface is identified, and tracking means for tracking each surface point from a loadless state in which no load is applied to the bone to a loaded state in which a load is applied; Displacement measuring means for measuring a plurality of displacements corresponding to a plurality of surface points by measuring the displacement of the surface points up to a loaded state for each ultrasonic beam, and bone mechanics based on the plurality of measured displacements Characteristic evaluation means that evaluates the physical characteristics, the characteristic evaluation means in a coordinate system comprising an axis corresponding to the beam position of the ultrasonic beam and an axis corresponding to the displacement of the surface point Based on a plurality of actual measurement points obtained as points that associate the beam position of the ultrasonic beam and the displacement measured by the ultrasonic beam, an interpolation line connecting the plurality of actual measurement points is generated, and the interpolation line is generated. The amount of elasticity of the bone is calculated as the mechanical characteristic from the degree of bending.

  The present invention makes it possible to diagnose hard tissues such as bones with higher accuracy.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

  FIG. 1 shows a preferred embodiment of an ultrasonic diagnostic apparatus according to the present invention, and FIG. 1 is a block diagram showing the overall configuration thereof. The probe 10 is preferably an ultrasonic probe that is used in contact with the body surface of the subject 50. Of course, an ultrasonic probe used by being inserted into the subject may be used. The probe 10 forms the ultrasonic beam 40 toward the bone 52 in the body of the subject 50. As the probe 10, a linear electronic scan probe (linear probe) that electronically scans the ultrasonic beam 40 is suitable, but a method such as sector electronic scan may be used. The bone 52 to be diagnosed is, for example, a tibia or a rib. The tracking point 42 set on the bone 52 will be described in detail later.

  The transmission / reception unit 12 controls the probe 10 to electronically scan the ultrasonic beam 40 within the tomographic plane (the cut surface of the subject 50 shown in FIG. 1). When the probe 10 is a linear probe, for example, 120 ultrasonic beams 40 (FIG. 1 shows only five ultrasonic beams for echo tracking, which will be described in detail later) are electronically scanned one after another. An echo signal is acquired for each ultrasonic beam 40. The acquired plurality of echo signals are output to the tomographic image forming unit 18, and the tomographic image forming unit 18 forms a tomographic image (B-mode image) of the bone based on the plurality of echo signals.

  The echo signal acquired by the transmission / reception unit 12 is also output to the echo tracking processing unit 20. The echo tracking processing unit 20 performs a so-called echo tracking process of extracting and tracking a bone surface part from each echo signal. For the echo tracking process, for example, a technique detailed in Japanese Patent Laid-Open No. 2001-309918 is used. For example, five tracking echo signals are used for the echo tracking process. The tracking echo signal may be selected from echo signals used for tomographic image formation (for example, 120 echo signals), or five tracking echoes separately from the tomographic image forming beam. A signal may be formed.

  Each of the five ultrasonic beams 40 shown in FIG. 1 is a beam for acquiring a tracking echo signal. The inspector inputs an instruction regarding transmission / reception of ultrasonic waves to the transmission / reception control unit 14 via the operation panel 16, and the transmission / reception control unit 14 controls the transmission / reception unit 12 based on the instruction of the inspector. As a result, the ultrasonic beam 40 for acquiring the tracking echo signal is transmitted to the diagnostic site on the bone surface based on the instruction of the examiner. In ultrasonic transmission / reception, a strong reflected wave is acquired from the bone surface. Therefore, each echo signal acquired from within the subject is acquired with a large amplitude in a portion corresponding to the bone surface portion.

  FIG. 2 is a schematic diagram showing a bone surface portion of each echo signal. As shown in FIG. 2, each echo signal indicates a range 60 where the amplitude is large at a portion corresponding to the bone surface. When the bone surface portion is simply regarded as a portion having a large amplitude, it is unclear which portion in the range 60 corresponds to the surface portion, and as a result, an extraction error of about the range 60 occurs. In the echo tracking process, the zero-cross point 62 is detected as a representative point of each echo signal, and the extraction accuracy is greatly improved by tracking the detected zero-cross point 62.

  The zero-cross point 62 is detected as a timing at which the polarity of the echo signal is inverted from positive to negative or from negative to positive in the tracking gate period 64. In FIG. 2, the zero cross point 62 is a timing at which the polarity of the echo signal is inverted from positive to negative. When the zero-cross point 62 is detected, a tracking gate is newly set around that point. Then, in the echo signal acquired from the same part next time, the zero cross point 62 is detected within the newly set tracking gate period 64. In this way, the zero cross point 62 is tracked as a surface point for each echo signal.

  FIG. 3 is a diagram for explaining a state of tracking of the bone surface portion by five echo signals. In the evaluation of the mechanical characteristics of bone using the ultrasonic diagnostic apparatus of the present invention, the displacement of the surface point between a state in which no load is applied to the bone (no load) and a state in which a load is applied (with load) Is measured for each echo signal (for each ultrasonic beam).

  FIG. 3A shows a state of tracking for the bone 52 without load. Each echo signal 68 corresponding to each of the five ultrasonic beams 40 directed to the bone 52 shows a large amplitude (amplitude maximum portion 69) in a portion corresponding to the bone surface. The five ultrasonic beams 40 are given beam numbers 1 to 5 in order from the top of the figure. Since the zero cross point (reference numeral 62 in FIG. 2) is detected as a surface point in the amplitude maximum portion 69 for each ultrasonic beam, the bone surface position is specified with extremely high accuracy.

  FIG. 3B shows a state of tracking for the bone 52 with load. As in FIG. 3A, the shape of the bone surface can be grasped based on the echo signals 68 corresponding to each of the five ultrasonic beams 40. Note that due to the influence of the load, the bone 52 in FIG. 3B is more distorted (the degree of bending of the bone) than the bone 52 in FIG. Although FIG. 3 shows an example in which the number of echo signals for echo tracking is five, it is possible to measure a plurality of signals other than five.

  Returning to FIG. 1, in the echo tracking processing unit 20, a surface point tracked for each echo signal, that is, for each ultrasonic beam 40 is a tracking point 42. The displacement measuring unit 22 measures the displacement of the surface point (tracking point 42) between the unloaded state and the loaded state for each ultrasonic beam 40, and the surface point from each of the five ultrasonic beams 40. Measure the displacement. That is, for each ultrasonic beam from beam number 1 to beam number 5 shown in FIG. 3, the movement amount of the zero cross point between no load and with load is measured. As a result, displacements for five points on the bone surface are obtained.

  Further, the displacement relating to the five points on the bone surface is pointed as an actual measurement point in a coordinate system composed of an axis indicating the beam position of the ultrasonic beam 40 and an axis indicating the displacement of the surface point. Then, an interpolation line connecting a plurality of actually measured points is generated in the interpolation line generation unit 24, and further, the elastic amount of the bone for evaluating the mechanical characteristics of the bone in the elastic amount calculation unit 26 from the degree of bending of the interpolation line. Is calculated.

  Therefore, the operation from the displacement measuring unit 22 to the elastic amount calculating unit 26 will be described in detail. In the following description, the reference numerals in FIG. 1 are used for the portions shown in FIG.

  FIG. 4 is a diagram for explaining a method for calculating the elastic amount of bone. FIG. 4 shows a coordinate system in which the beam position of the ultrasonic beam 40 is the vertical axis and the displacement of the surface point is the horizontal axis. On the coordinate system, five actually measured points 70 are pointed as points in which the position of each ultrasonic beam is associated with the displacement measured by the ultrasonic beam. The beam position is the position of each ultrasonic beam for echo tracking (the height of each ultrasonic beam 40 in FIG. 1), and the beam numbers from beam number 1 to beam number 5 in order from the top (from the highest). Specified by.

  Then, an interpolation line 72 that connects the five actual measurement points 70 is generated by the interpolation line generation unit 24. The interpolation line 72 can be obtained by curve interpolation of the five actual measurement points 70 using, for example, spline interpolation or least square interpolation.

  Further, the degree of bending of the interpolation line 72 is evaluated by the elastic amount calculation unit 26 based on a comparison between the straight line 74 connecting the two end points of the five actual measurement points 70 and the interpolation line 72. Specifically, based on the distance d between the maximum displacement point 80 that is the point on the interpolation line 72 that is farthest from the straight line 74 and the straight line 74, for example, from the length L and the distance d of the straight line 74. Ε = d / L is calculated as an index value indicating the amount of elasticity of the bone. The index amount ε is called a strain.

  It should be noted that the elastic amount calculation unit 26 is supplied with a measurement result of a load value accompanying pressurization on the bone 52 from the load measuring device 36. For this reason, the elastic quantity calculation unit 26 can obtain a measurement result in which the strain ε is associated with the load value at that time.

  In the elastic amount calculation method described with reference to FIG. 4, a straight line 74 connecting two end points of the five actual measurement points 70 is used. However, there is a method for obtaining the distance d without using the straight line 74.

  FIG. 5 is a diagram for explaining a method for calculating the distance d without using a straight line connecting two end points. Each of FIGS. 5A and 5B shows a coordinate system in which the beam position of the ultrasonic beam is the vertical axis and the displacement of the surface point is the horizontal axis, as in FIG. On the coordinate system, five actual measurement points are pointed as points in which the position of each ultrasonic beam is associated with the displacement measured by the ultrasonic beam.

  In each of FIGS. 5A and 5B, among the five measured points, the distance d is obtained as a displacement difference between the maximum point 70L having the maximum displacement and the minimum point 70S having the minimum displacement. Yes. However, when the distance d is obtained by the method shown in FIG. 5, there is a problem that the distance d is overestimated when the bone surface is accompanied by a rotation component in the tomographic plane.

  That is, when (A) and (B) in FIG. 5 are compared, (B) in FIG. 5 corresponds to the case where the bone surface is accompanied by a rotation component in the tomographic plane, which is different from (A) in FIG. As a result, the displacement measurement results are generally tilted. For this reason, in FIG. 5B, the distance d is overestimated compared to FIG. 5A due to the influence of the overall rotational component of the bone surface.

  On the other hand, the elastic amount calculation method described with reference to FIG. 4 uses the straight line 74 connecting the two end points of the five actual measurement points 70, so that the entire rotation of the bone surface is temporarily assumed. Even if there is a component, the straight line 74 is tilted following the rotational component, so that the rotational component is canceled. As a result, the distance d can be accurately calculated without being influenced by the rotational component. . Further, even when there is an overall translational component on the bone surface, the translational component is also canceled because the straight line 74 is obtained by following the translational component. For this reason, the calculation method described with reference to FIG. 4 makes it possible to accurately calculate the elastic amount by removing the entire translational component and rotational component of the bone surface.

  Next, a display example of measurement results in the present embodiment will be described. 6 to 9 show display image examples of measurement results formed in the display image forming unit 32 and displayed on the display 34.

  FIG. 6 is a graph showing time (time) as a horizontal axis and load as a vertical axis. That is, it is a graph showing the load value at each time measured by the load measuring device 36. Incidentally, the load value (113 Newton) corresponding to the position of the cursor that the user moves through the operation panel 16 is displayed numerically.

  FIG. 7 is a graph showing time (time) as a horizontal axis and distortion (strain) as a vertical axis. That is, it is a graph showing the strain ε at each time measured by the elastic quantity calculation unit 26 for the bone in a state where the load value shown in FIG. 6 is applied at each time. In addition, the distance d (refer FIG. 5) calculated | required without using the straight line which connects two end points is used for calculation of the strain (epsilon) in FIG. For this reason, the strain ε is calculated in a state where the rotation component of the entire bone is not canceled. Incidentally, a strain (6177 microstrain) corresponding to the position of the cursor is numerically displayed.

  FIG. 8 is a graph showing the time (time) as the horizontal axis and the strain (strain) as the vertical axis, as in FIG. That is, it is a graph showing the strain ε at each time measured by the elastic quantity calculation unit 26 for the bone in a state where the load value shown in FIG. 6 is applied at each time. In addition, in the calculation of the strain ε in FIG. 8, a method for calculating the distance d (see FIG. 4) using a straight line connecting two end points is used. That is, in FIG. 8, the translational component and rotational component of the entire bone are canceled, and the strain ε is calculated with high accuracy. For this reason, in FIG. 8, the change of the strain ε following the change of the load shown in FIG. 6 can be read. For example, corresponding to the three peaks in the change in load shown in FIG. 6, three peaks can be read in the change in the strain ε shown in FIG.

  Incidentally, in FIG. 7, since the strain ε is not obtained with high accuracy due to reasons such as the fact that the rotation component of the entire bone is not canceled, a subtle strain change cannot be detected, and FIG. It is difficult to read a clear correspondence even in comparison with the change in load shown in.

  In FIG. 8, the strain (262 microstrain) corresponding to the position of the cursor is also displayed numerically. In addition, the structure by which a cursor is set to the maximum value of a strain by an apparatus may be sufficient.

  FIG. 9 is a graph showing the displacement on the horizontal axis and the beam position on the vertical axis. In other words, it corresponds to the image display of the coordinate system shown in FIG. 4, and five measured points (small black circles), a straight line connecting the two end points (broken line), an interpolation line (solid line), and a maximum displacement point (large black circle) are combined. The displayed image. Furthermore, the distance Max (17.4 micrometers) and the strain (434 microstrain) between the maximum displacement point and the straight line are numerically displayed.

  The display image described with reference to FIGS. 6 to 9 is formed in the display image forming unit 32 and displayed on the display 34. Each image shown in FIGS. 6 to 9 may be displayed on the display 34 alone, or may be displayed in a state where a plurality of images are arranged. Further, the tomographic image formed by the tomographic image forming unit 18 and the images shown in FIGS. 6 to 9 may be displayed in a state of being arranged.

  As mentioned above, although preferred embodiment of this invention was described, embodiment mentioned above is only a mere illustration in all the points, and does not limit the scope of the present invention.

1 is a block diagram showing an overall configuration of an ultrasonic diagnostic apparatus according to the present invention. It is a schematic diagram which shows the bone surface part of each echo signal. It is a figure for demonstrating the mode of tracking of a bone surface part. It is a figure for demonstrating the calculation method of the elastic amount of a bone. It is a figure for demonstrating the method of calculating the distance d. It is the graph display which showed the load on the vertical axis with time as the horizontal axis. It is the graph display which showed time on the horizontal axis and the strain on the vertical axis. It is the graph display which showed time on the horizontal axis and the strain on the vertical axis. It is a graph display in which the horizontal axis represents displacement and the vertical axis represents beam position.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Probe, 20 Echo tracking process part, 22 Displacement measurement part, 24 Interpolation line production | generation part, 26 Elasticity calculation part, 32 Display image formation part.

Claims (6)

Transmitting and receiving means for forming a plurality of ultrasonic beams on the hard tissue;
A tracking means for detecting a surface point corresponding to the surface of the hard tissue for each ultrasonic beam and tracking the surface point for each ultrasonic beam;
Displacement measuring means that measures the amount of movement of the surface point for each ultrasonic beam when an external action is applied to the hard tissue, and obtains a plurality of amounts of movement corresponding to the plurality of surface points from the plurality of ultrasonic beams. When,
A property evaluation means for evaluating mechanical properties of hard tissue based on a plurality of movement amounts obtained from a plurality of ultrasonic beams ;
Having
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1,
The characteristic evaluation means is measured with the beam position of each ultrasonic beam and the ultrasonic beam in a coordinate system composed of an axis corresponding to the beam position of the ultrasonic beam and an axis corresponding to the amount of movement of the surface point. Based on a plurality of actual measurement points obtained as points associated with the amount of movement, an interpolation line connecting the plurality of actual measurement points is generated, and the mechanical characteristics are evaluated from the degree of bending of the interpolation line.
An ultrasonic diagnostic apparatus. Transmitting and receiving means for forming a plurality of ultrasonic beams on the hard tissue;
Surface detecting means for detecting a surface point corresponding to the surface of the hard tissue for each ultrasonic beam and detecting a plurality of surface points from the plurality of ultrasonic beams; and
A displacement measuring means for measuring a plurality of displacements corresponding to a plurality of surface points by measuring the displacement of the surface points when an external action is exerted on the hard tissue for each ultrasonic beam;
A property evaluation means for evaluating mechanical properties of the hard tissue based on the plurality of measured displacements;
Have
The characteristic evaluation means is measured with the beam position of each ultrasonic beam and the ultrasonic beam in a coordinate system composed of an axis corresponding to the beam position of the ultrasonic beam and an axis corresponding to the displacement of the surface point. Based on a plurality of actual measurement points obtained as points corresponding to the displacement, an interpolation line connecting the plurality of actual measurement points is generated, and a straight line connecting two end points of the plurality of actual measurement points and the interpolation line And determining the degree of bending of the interpolation line based on the comparison with the evaluation of the mechanical characteristics from the degree of bending of the interpolation line,
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 3.
The characteristic evaluation means is characterized by the elasticity of the bone as the mechanical characteristic based on the distance between the maximum displacement point, which is a point on the interpolation line that is located farthest from the straight line connecting the two end points, and the straight line Calculate the quantity,
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 4,
An image forming unit that forms an image obtained by combining the straight line connecting the two end points, the interpolation line, and the maximum displacement point;
An ultrasonic diagnostic apparatus. Transmitting and receiving means for forming a plurality of ultrasonic beams on the bone in the subject;
The surface point corresponding to the bone surface is identified for each ultrasonic beam, and the surface point is tracked for each ultrasonic beam from the unloaded state where no load is applied to the bone to the loaded state where the load is applied. Tracking means to
A displacement measuring means for obtaining a plurality of moving amount of the moving amount of the surface points is measured for each ultrasound beam, the corresponding plurality of ultrasonic beams in a plurality of surface points from the load-free state until the load chromatic state,
A property evaluation means for evaluating mechanical properties of bone based on a plurality of movement amounts obtained from a plurality of ultrasonic beams ;
Have
The characteristic evaluation means is measured with the beam position of each ultrasonic beam and the ultrasonic beam in a coordinate system composed of an axis corresponding to the beam position of the ultrasonic beam and an axis corresponding to the amount of movement of the surface point. Based on a plurality of actual measurement points obtained as points corresponding to the movement amount , an interpolation line connecting the plurality of actual measurement points is generated, and the elasticity of the bone is determined as the mechanical characteristic from the degree of bending of the interpolation line. Calculate the quantity,
An ultrasonic diagnostic apparatus.

Images