JP2007050096A - Bone evaluating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bone evaluating apparatus which evaluates the inner structure of the bone with a simple configuration. <P>SOLUTION: The bone 30 is scanned by an ultrasonic beam 50 to acquire a distribution of property values 52. The property values are, for example, an attenuation value of an ultrasonic wave. The distribution of property values 52 reflects the distribution of bone beams in the bone 30 and generally has an M shape. By analyzing the shape of the distribution, the distribution of the bone beams within the bone 30 is estimated and the mechanical structure of the bone is evaluated. In the method, X rays can substitute for ultrasonic waves. Normalization operation using the bone thickness can also be applied to the method. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a bone evaluation apparatus, and more particularly to measurement of bone strength.

  The bone evaluation apparatus is an apparatus that evaluates bone properties using X-rays or ultrasonic waves. In the case of bone evaluation using X-rays, the amount of bone mineral is determined from the amount of attenuation for X-rays that are irradiated with X-rays to the measurement site and transmitted through the measurement site. In the case of bone evaluation using ultrasonic waves, ultrasonic waves are transmitted to the site to be measured, and the sound characteristics and structural characteristics of the bone are observed by observing the speed of sound and attenuation of the ultrasonic waves that have passed through the site to be measured. An evaluation value representing the characteristic is calculated. Patent Document 1 discloses a bone evaluation apparatus that evaluates bone properties by combining X-ray measurement and ultrasonic measurement. Patent Document 2 discloses that ultrasonic attenuation, in particular, the inclination of attenuation characteristics is used for bone evaluation. Patent Document 3 discloses a mechanism for positioning an ultrasonic beam.

  Conventionally, the property value is measured for the entire target bone, and the spatial distribution (shape) of the property value is not actively analyzed and evaluated. In Patent Documents 4 and 5, the distribution of scattered ultrasonic waves generated by scattering of ultrasonic waves generated in the bone is measured. However, the distribution does not reflect the change in the property value at each position of the bone, but reflects the structural properties of the entire bone. FIG. 5 of Patent Document 6 shows a sound velocity distribution having an M shape. However, it is only for determining the measurement position, and its own shape is not evaluated. Patent Document 7 describes processing of an ultrasonic reception signal (A mode waveform) that has passed through a bone. Patent Document 8 describes that a trabecular image is formed based on X-ray measurement.

JP-A-6-22960 JP 7-31612 A JP-A-7-204205 JP-A-8-117225 JP-A-9-84788 JP-A-9-224935 JP 2001-95797 A JP-A-8-164129

  As described above, conventionally, the property value of the whole bone or the property value of the bone at a specific position has been measured, and the spatial distribution (shape) of the property value has been actively analyzed and evaluated. Is not done. It is possible to perform two-dimensional or three-dimensional structural analysis of bone using an X-ray CT apparatus or the like, but such an apparatus is very expensive and requires a large scale of the apparatus, making it easy to make a diagnosis. difficult. There is also a problem that the amount of exposure is large. Bone strength is thought to be greatly influenced by its internal structure (particularly the trabecular distribution pattern), and it is desirable to measure the difference in bone strength due to the difference in internal structure with a simple mechanism. Yes.

  An object of the present invention is to simply measure bone strength. Another object of the present invention is to simply measure the density distribution of trabecular bone.

(1) A bone evaluation apparatus according to the present invention includes a beam scanning unit that scans a subject with a physical wave beam, and a bone at each beam scanning position based on a reception signal obtained by scanning the physical wave beam. A property value calculating means for calculating a property value of the object, a property value distribution generating means for generating a property value distribution from the property value of the bone at each beam scanning position, and a bone strength based on the property value distribution. Evaluation value calculating means for calculating an evaluation value.

  Bone strength (or ease of fracture) depends on the composition and structure of the bone. As will be described later, the trabecular bone directly affects the rigidity of the bone. If the total amount of the trabecular bone is the same, it is considered that the strength of the bone changes depending on the state of trabecular distribution. The above property value distribution reflects changes in the internal structure of the bone in the beam scanning direction. If there is a density (density change) in the trabecular distribution within the bone, it will appear in the property value distribution. become. Therefore, it is possible to estimate the state of trabecular distribution by obtaining the property value distribution and quantitatively analyzing it by some method, that is, obtaining one evaluation value that indicates the strength of the bone. It becomes possible.

  Therefore, in the above configuration, a physical wave beam is scanned with respect to a subject having a bone, and a property value reflecting the property (property or state) of the bone is calculated for each beam scanning position. Then, an evaluation value related to bone strength is calculated based on the property value distribution generated from them. The evaluation value is basically positioned as a trabecular distribution evaluation value viewed from the viewpoint of trabecular distribution. In addition to such evaluation values, other evaluation values may be considered together as necessary, and thereby the bone may be comprehensively diagnosed.

  The physical wave is preferably an ultrasonic wave from the viewpoint of exposure, but may be an X-ray. The physical wave beam is preferably linearly one-dimensionally scanned, but may be two-dimensionally or three-dimensionally scanned. The scanning may be performed mechanically or electronically. The property value can be an attenuation amount of ultrasonic waves, a sound velocity value, an attenuation amount of X-rays, or the like. A property value distribution may be formed by mapping the property values acquired at each beam scanning position as they are, or by applying a normalization operation to each property value and mapping the calculation results. A property value distribution may be formed. An evaluation value is calculated by analyzing the property value distribution. The property value distribution may be displayed on a display. The evaluation value may be obtained by combining the analysis result of the property value distribution with the standard evaluation value obtained statistically. As a method for analyzing the property value distribution, various methods can be considered as described later.

  Preferably, the physical wave beam is an ultrasonic beam, the beam scanning means is a means for mechanically or electronically scanning the ultrasonic beam, and the property value relates to attenuation of ultrasonic waves or sound velocity. Value. If ultrasonic waves are used, the problem of exposure can be avoided. However, it is possible to use X-rays instead of ultrasonic waves, and it is also possible to use both ultrasonic waves and X-rays. In any case, a large rotation mechanism such as an X-ray CT apparatus is not necessary, and one or a plurality of mechanisms for linearly scanning a physical wave beam are provided.

  Preferably, the evaluation value calculating means calculates the evaluation value based on the shape of the property value distribution. In general, it is considered that the trabecular distribution within the bone is reflected in the property value distribution. Therefore, by analyzing the shape, it is possible to evaluate the risk of fracture from the viewpoint of the trabecular structure.

  Desirably, the said evaluation value reflects the height difference of the center part and edge part in the said property value distribution. Preferably, the evaluation value reflects an M-shaped degree of the property value distribution. Although depending on the bone to be measured, in general, in a one-dimensional property value distribution, it is possible to recognize a tendency that the property value continuously changes from the center to both ends of the bone. In order to easily analyze the shape of the property value distribution, it is desirable to refer to several representative values in the shape, such as the central value, the edge value, the maximum value, and the minimum value. , Slope etc. For example, in the case where the attenuation value of ultrasonic waves is a property value, when the property value distribution is observed, it exhibits a M-shape that is more or less, and more trabecular bones are unevenly distributed around the bone. The M-shaped degree becomes stronger (the central part is further lowered and both end parts are further raised). Therefore, by evaluating the degree of the M-shape, it is possible to estimate the degree of uneven distribution of the trabecula, and as a result, one index value for the strength of the bone can be obtained.

  Preferably, a database in which standard values are registered is included, and the evaluation value calculation means calculates the evaluation values by comparing a result value of shape analysis for the property value distribution with a standard value registered in the database. To do. The standard value may have a certain width. It is desirable to provide a deviation amount from the standard value as an evaluation value. In the database, it is desirable to manage various attributes relating to the subject as key items and compare the actually measured values with standard values under the same conditions.

  Preferably, it includes means for measuring the bone thickness at each beam scanning position, and the property value distribution generating means standardizes the bone property value at each beam scanning position by the bone thickness at each beam scanning position. To generate the property value distribution. According to such normalization, at least the influence of the individual difference regarding the thickness can be eliminated, and the shape change of the property value distribution resulting from the trabecular distribution can be grasped more accurately and objectively.

  Preferably, the means for measuring the thickness of the bone includes means for determining the bone surface position by transmitting an ultrasonic wave to the bone surface and receiving a reflected wave from the bone surface. The ultrasonic transducer for outer shape measurement and the ultrasonic transducer for property value measurement can be configured by separate ultrasonic transducers, or can be configured by the same ultrasonic transducer. According to the latter, the apparatus configuration can be simplified.

(2) A bone evaluation apparatus according to the present invention includes a first beam scanning unit that scans a subject with a first physical wave beam along a first direction, and a second direction that intersects the first direction. Along the second beam scanning means for scanning the subject with the second physical wave beam and each beam scanning position in the first direction based on the received signal obtained by scanning the first physical wave beam. First property value calculating means for calculating a first property value of each bone, and a first property value distribution for generating a first property value distribution from the first property value of the bone for each beam scanning position in the first direction. Generating means; second property value calculating means for calculating a second property value of bone for each beam scanning position in the second direction based on a received signal obtained by scanning of the second physical wave beam; and For each beam scanning position in the second direction Second property value distribution generating means for generating a second property value distribution from the second property value, and calculating an evaluation value related to bone strength based on the first property value distribution and the second property value distribution Evaluation value calculation means.

  According to the above configuration, the first property value distribution and the second property value distribution can be acquired for the first direction and the second direction intersecting each other, and the evaluation value is calculated based on them. It is also possible to estimate the two-dimensional distribution of trabecular bone from the first property value distribution and the second property value distribution, and it is also possible to calculate the following predetermined moment values from such a two-dimensional distribution. . Desirably, the first direction and the second direction are in an orthogonal relationship. The scanning of the first physical wave beam and the scanning of the second physical wave beam are executed simultaneously or in time division. In order to estimate the two-dimensional distribution of the trabecular bone, it is desirable to measure the outer shape of the target bone if necessary. It is also possible to scan the ultrasonic beam three-dimensionally. The target bone is preferably a rib, but may be other bones.

  Preferably, the evaluation value calculating means calculates the evaluation value as a predetermined moment value defined from a spatial trabecular distribution inside the bone based on the first property value distribution and the second property value distribution. To do. Predetermined moment values include cross-section secondary moment, minimum cross-section secondary moment, cross-section secondary pole moment, moment around the center of gravity, etc. Any other physical quantity may be used as long as it quantitatively indicates the strength of the bone from the body. In addition, when the two-dimensional distribution of the trabecular bone can be estimated, an image schematically representing it may be formed and displayed.

  As described above, according to the present invention, the strength of the bone can be easily measured. Alternatively, the density distribution of trabecular bone can be easily measured.

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

  First, the principle of bone evaluation according to the present embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 (A) shows a bone structure model. This bone structure model is created for explaining the principle, and does not directly reflect the actual bone structure. In the bone structure model shown in (A), reference numeral 10 indicates a soft tissue, and a bone 11 as an evaluation target exists in the soft tissue 10. The bone 11 is, for example, a rib, but the bone targeted by the present invention is not limited thereto. The bone 11 is roughly divided into a cortical bone 12 as an outer portion and a cancellous bone 14 existing inside the bone. (B) shows an enlarged view of the partial region 16 shown in (A). The cancellous bone 14 is composed of a trabecular bone 18 that is mainly composed of calcium or the like, and a bone marrow 20 that exists between the trabeculae. Here, the trabecular bone is solid and has rigidity. On the other hand, bone marrow is gelatinous and itself contributes little to rigidity.

  FIG. 2 shows two types of bone structure models. (A) shows a uniform model, and (B) shows an uneven distribution model. Here, the uniform model shown in (A) represents that the trabecular bone shown as a black dot is uniformly present throughout the cancellous bone 14A. The uneven distribution model shown in (B) shows that the density of the trabecular bone is higher in the peripheral part (see 14B) than in the central part (see 14C) in the cancellous bones 14B and 14C. Incidentally, in the uniform model shown in (A) and the uneven distribution model (B), the schematic drawing is performed so that the total amount of bone is the same. In each model, black dots represent trabecular bone as described above, and white portions as gaps between them are bone marrow. In contrast between (A) and (B), the total area of black spots and the total area of white portions are the same. The amount of cortical bone is also the same.

  When these two models are compared structurally, it can be said that the unevenly distributed model shown in (B) is more difficult to break than the uniform model shown in (A). That is, generally, if the amount of bone is the same, the drag when the external force is applied becomes larger when the trabecular bone exhibiting rigidity is more distributed in the peripheral portion of the bone. This is more apparent when structural mechanics, that is, mathematical analysis is performed. For example, the cross-sectional secondary moment or the cross-sectional secondary moment is calculated. As described above, each model in FIG. 2 is also for explaining the principle of the invention, and the structure in the actual bone exhibits diversity, but in any case, the trabecular distribution is related to the rigidity of the bone. It can be understood that this is one major factor that has an impact.

  Therefore, as described in detail below, the trabecular distribution is estimated from the form of the property value distribution by scanning the bone with an ultrasonic beam or an X-ray beam and thereby obtaining the property value. As a result, it is possible to evaluate the strength of the bone from the structural mechanical viewpoint. Of course, other factors such as bone mineral content and cortical bone thickness may be considered in considering the rigidity of the bone, but in the present embodiment, focusing on the trabecular distribution, the soundness of the bone from that viewpoint. As an index value for diagnosing the above, the evaluation value described in detail below is calculated. Therefore, in order to comprehensively diagnose bones, other evaluation results may be considered in addition to the evaluation results obtained by the bone evaluation apparatus according to the present embodiment.

  FIG. 3 shows the overall configuration of the bone evaluation apparatus according to the first embodiment. The bone evaluation device includes a measurement unit 22 and a calculation control unit 24.

  The measurement unit 22 includes a first measurement unit 32 and a second measurement unit 34 provided on both sides of the subject 26. In the subject 26, a bone 30 to be measured exists in the soft tissue 28. The first measurement unit 32 and the second measurement unit 34 have transducers 36A and 36B and scanning mechanisms 38A and 38B, respectively. In this embodiment, the transducers 36A and 36B are configured as ultrasonic transducers that transmit or receive ultrasonic waves. The ultrasonic transducer may be a single transducer or a one-dimensional or two-dimensional array transducer. In any case, an ultrasonic wave is emitted from the transducer 36A, and an ultrasonic beam 50 is formed by applying an acoustic lens or an electronic focusing technique. The ultrasonic beam 50 passes through the bone 30. The transmitted ultrasonic wave is received by the transducer 36 </ b> B, and a reception signal generated by the reception is output to the transmission / reception unit 40.

  The scanning mechanisms 38A and 38B include rails extending in the Y direction in the drawing, and the transducers 36A and 36B can be linearly moved along the rails by a driving mechanism (not shown). The scanning of the transducer 36A and the transducer 36B is controlled so that they are always positioned at the same position in the Y direction. Incidentally, in the illustrated example, the ultrasonic beam 50 is formed along the X direction.

  The calculation control unit 24 includes two transmission / reception units 40 and 42, a control unit 44, a calculation unit 46, a database (DB) 47, and the like. In this embodiment, the transmission / reception unit 42 supplies a transmission signal to the transducer 36A. As a result, ultrasonic waves are radiated from the transducer 36A as described above. The transceiver unit 40 is connected to the transducer 36B. As described above, the reception signal output from the transducer 36 </ b> B is input to the transmission / reception unit 40. As described above, in the configuration example shown in FIG. 3, the transmission / reception unit 42 functions as a transmission circuit, and the transmission / reception unit 40 functions as a reception circuit. Each of the transducers 36A and 36B may perform both transmission and reception of ultrasonic waves. In that case, the transmission / reception units 40 and 42 each function as a transmission / reception circuit. The control unit 44 controls the operation of the two transmission / reception units 40 and 42 described above. In particular, the control unit 44 outputs a transmission control signal to the transmission / reception unit 42 and receives a reception signal output from the transmission / reception unit 40. Then, after performing necessary signal processing on the received signal, the received signal is passed to the arithmetic unit 46. The control unit 44 controls the operation of the scanning mechanisms 38A and 38B. As described above, the control unit 44 performs the scanning control so that the two transducers 36A and 36B are always maintained in the facing relationship.

  The arithmetic unit 46 is a unit that calculates an evaluation value representing bone strength by analyzing a received signal. This calculation unit 46 has a function of calculating bone property values from received signals at each beam scanning position, a function of generating a one-dimensional property value distribution based on these property values, and analyzing the shape of the property value distribution. Has a function of calculating an evaluation value. The database 47 is referred to when calculating the evaluation value, which will be described in detail later.

  In the configuration example shown in FIG. 3, the subject 26 and the two transducers 36A and 36B are immersed in a water tank or the like in order to ensure good propagation of ultrasonic waves between the transducer 36A and the transducer 36B. You may make it make it. Alternatively, a coupling medium such as a water bag may be provided between the surface of the subject 26 and each of the transducers 36A and 36B. In the configuration example described above, the scanning of the ultrasonic beam 50 is performed using the scanning mechanisms 38A and 38B. However, the ultrasonic beam is scanned electronically using a 1D array transducer or a 2D array transducer. It may be. If a two-dimensional array transducer is used, a two-dimensional property value distribution can be obtained.

  Next, the evaluation value calculation method will be described with reference to FIG. As described above, a state in which the ultrasonic beam 50 is scanned in the Y direction is shown in FIG. The property value is calculated by analyzing the received signal acquired at each scanning position. The property value is, for example, the attenuation amount of ultrasonic waves, or the speed of sound of ultrasonic waves. Alternatively, other physical quantities may be used. In any case, it is desirable to use, as a property value, a physical quantity that changes due to the transmission of ultrasonic waves to the bone 30, especially a physical quantity that reflects the density of the trabecular bone.

  (B) shows a mapping of ultrasonic attenuation as such a property value. That is, the property value distribution 52 is obtained by mapping the attenuation amount at each scanning position, and the attenuation amount corresponds to the amount of bone mineral on the beam. Incidentally, the bone 30 is represented as a model as described above, and the property value distribution 52 shown in (B) is a simulation result when the model is assumed. When an actual bone is observed, the property value distribution 52 has a greater or smaller M shape. That is, since both ends of the property value distribution 52 correspond to cortical bone, the amount of attenuation there is very large. On the other hand, since there are generally not many trabeculae in the center, the amount of attenuation in the center is compared. Low value.

  FIG. 5 shows the distribution of property values for the two models shown in FIG. That is, reference numeral 54 corresponds to the uniform model shown in FIG. 2, and reference numeral 56 corresponds to the uneven distribution model shown in FIG. The property value distribution indicated by reference numeral 54 does not have an M-shaped form, but as described above, the actual measurement result has a more or less M-shaped form.

  What should be noted in FIG. 5 is that the form of the property value distribution differs depending on the state of trabecular distribution, that is, whether it is uniformly distributed or unevenly distributed in the periphery. More specifically, if more trabeculae are present in the periphery, the degree of the M-shape increases. That is, the central portion in the property value distribution is lower and both end portions are higher. Therefore, in this embodiment, by analyzing the shape of the property value distribution, the trabecular distribution within the bone, that is, the evaluation value of the bone strength is obtained from the property value distribution.

  There are several methods for quantitatively evaluating the degree of the M-shape in the property value distribution. For example, the attenuation value at each position is normalized by dividing it by the maximum value (maximum attenuation value) in the property value distribution, and the ratio between the maximum value in the result and the minimum value that appears in the center is considered as the evaluation value. It is done. In this case, if the evaluation value is defined as the maximum value / minimum value, it is evaluated that the larger ratio is the bone that is hard to break on the structural surface. On the other hand, an average value is obtained for the property value distribution, and based on the average value, how far the maximum value in the property value distribution is or how far the minimum value is separated, that is, such a difference It is also possible to use the value as an evaluation value. In any case, the bone strength can be evaluated by quantifying the height difference or gradient between the central portion and the end portion of the property value distribution in some form. In the normalization calculation, the division by the maximum value is performed in the above description. However, the normalization can be performed by the area of the property value distribution, for example. Incidentally, the minimum value and the maximum value can be easily discriminated by using a known peak search technique. In addition to a method of evaluating the shape based on some representative values in the property value distribution, it is also possible to directly evaluate the shape of the property value distribution itself using a pattern fitting method or the like. In that case, the target property value distribution can be classified into any pattern, and the strength of the bone can be evaluated as a pattern to which the property value distribution belongs.

  It is also possible to perform a more objective evaluation using the database 47 shown in FIG. In that case, according to the method of analyzing the shape of the property value distribution, one or a plurality of attributes relating to the subject may be used as key items, and standard values that are statistically determined for each combination may be registered. . That is, when a shape analysis result is obtained for a certain subject, the analysis result is compared with a standard value having the same attribute as that of the subject, and an evaluation value (relative evaluation value) is obtained as the comparison result. You may make it calculate. As the attribute, first, the type of the target bone can be mentioned. Examples of this include bone types such as ribs, ribs, lumbar vertebrae, femoral neck, and femoral long tube. Moreover, it is good also considering the kind of organisms, such as a human and an animal, as an attribute. In addition, it is possible to set subjects such as race as attributes for humans, and it is desirable to manage age and sex as attributes in particular. If such a database is used, there is an advantage that the evaluation value can be obtained based on how much the actually measured value deviates from the standard value under the same conditions.

In FIG. 5, L ₁ and L ₂ indicate both ends of the property value distribution. L ₀ indicates the center position. The influence of cortical bone is large at both ends in the property value distribution, and in order to more accurately evaluate the trabecular distribution, it is also preferable to calculate the evaluation value by excluding that portion. As the center or reference, for example a central position L ₀ in the case, the entire range W1 without setting the partial region W2 as the window, the maximum value within that range, the minimum value, be observed average value Good. Here, Q ₂ indicates the minimum value that appears in the center of the property value distribution 56. Q ₁ indicates the maximum value in the entire range W ₁ in the property value distribution 56. When the range W2 is set as the window, the maximum value is specified within the range. In determining the maximum value, if it is determined that the error factor is large, a gradient or the like may be used instead of the maximum value. In any case, it is desirable to determine an evaluation value calculation method so that objective evaluation can be performed. In the above database, a standard value having a certain width can be registered.

6 and 7 show a modification of the above-described embodiment. That is, in the above-described embodiment, the property value or the evaluation value is calculated without considering the bone thickness. In this modification, as shown in FIG. 6, the outer shape of the bone is measured on both sides of the bone 30. Specifically, the transducers 36A and 36B transmit and receive ultrasonic waves, respectively. That is, after the ultrasonic wave is transmitted, the reflected wave reflected on the surface of the bone 30 is received. By measuring the time interval between transmission and reception, the distance can be determined from the speed of sound. That is, the distances L ₁ and L ₂ between the transducers 36A and 36B and the bone surface can be obtained. Then, if the above L ₁ and L ₂ are subtracted from the total path length L of the known ultrasonic beam 50, the bone thickness D at the scanning position can be obtained as a result.

  FIG. 7 shows the property value distribution after the normalization calculation. Here, the property value distribution indicated by reference numeral 62 corresponds to the uniform model shown in FIG. 2, and the property value distribution indicated by reference numeral 64 corresponds to the uneven distribution model shown in FIG. In any property value distribution, the horizontal axis represents the attenuation per unit thickness, that is, the value after normalization is mapped. Thus, if the property value or the evaluation value is obtained in a form that excludes the variation due to the thickness of the subject, there is an advantage that a more objective and reliable evaluation can be performed. In other words, even if there is a variation in shape as an individual difference for the target bone, an objective evaluation result can be obtained, so that there is an advantage that comparison of evaluation values between individuals can be performed more accurately. Of course, in such a modified example, the evaluation value may be obtained by comparison with a standard value registered in the database. In addition, when an effective reflected wave cannot be obtained at the end portion of the bone having roundness, the portion may be excluded from the analysis target of the property value distribution. That is, a window (W2) that defines an analysis range as shown in FIG. 5 may be set, and shape analysis may be performed within the range.

  Next, the bone evaluation apparatus according to the second embodiment will be described with reference to FIGS. 8 and 9. In addition, the same code | symbol is attached | subjected to the structure similar to the structure shown in FIG. 3, and the description is abbreviate | omitted.

  The bone evaluation apparatus shown in FIG. 8 is roughly composed of a measurement unit 22 and a calculation control unit 24. The measurement unit 22 includes four measurement units 32, 34, 66, and 68 in the configuration example shown in FIG. Each of the measurement units 32, 34, 66, and 68 includes transducers 36A, 36B, 36C, and 36D as ultrasonic transducers, and scanning mechanisms 38A, 38B, 38C, and 38D. As shown in the figure, the measurement units 32 and 34 form an ultrasonic beam 50 along the X direction, and the ultrasonic beam 50 is scanned in the Y direction. On the other hand, the measurement units 66 and 68 form an ultrasonic beam 70 along the Y direction as shown in the figure, and the ultrasonic beam 70 is scanned in the X direction.

  The arithmetic control unit 24 includes four transmission / reception units 76, 77, 78, 79, a control unit 82, an arithmetic unit 84, a database 85, and the like. The four transducers 36A, 36B, 36C, and 36D are connected to the transmission / reception units 76, 77, 78, and 79, respectively. The transducers 36A and 36B also transmit and receive ultrasonic waves in the X direction as indicated by reference numerals 58 and 60, whereby the bone surface shape is observed along the Y direction. Similarly, the transducers 36C and 36D transmit and receive ultrasonic waves in the Y direction as indicated by reference numerals 72 and 74, whereby the bone surface shape of the bone 30 is observed along the X direction. . Incidentally, the formation of the ultrasonic beams 50 and 70 can be performed simultaneously or in a time-sharing manner, and this also applies to the transmission and reception of ultrasonic waves for measuring the surface shape. That is, as long as there is no ultrasonic interference between the transducers, it is possible to simultaneously observe the shape.

  FIG. 9 shows the operation of the bone evaluation apparatus according to the second embodiment. When the ultrasonic beam 50 is scanned in the Y direction and the ultrasonic beam 70 is scanned in the X direction, the property value distributions 86 and 88 can be acquired in the respective directions. Here, the above-described normalization calculation based on the bone thickness is applied to each of the property value distributions 86 and 88, that is, each property value corresponds to an attenuation per unit thickness.

  According to the second embodiment, since the property value distribution can be acquired from two directions, it is possible to evaluate the bone strength based on each property value distribution, as will be described below. In addition, it is possible to estimate the internal structure of the target bone 30.

The outer shape of the bone 30 can be specified by the outer shape measurement as described above. Introducing the assumption that there is a cancellous bone with a certain trabecular space inside, assuming the outer shape, and estimating the diameter of the trabecular bone existing at each coordinate point in the model assuming such a model Is possible. For example, a value given to each coordinate point (grid point) and P (x, y), the weight of the property values in the x direction and w _x, if the weight of the attribute value in the y-direction and w _y, for example, P It can be defined as (x, y) = w _x × w _y . That is, the diameter of the trabecular bone at each lattice point can be given by such a calculation formula. However, the trabecular space in this case is constant.

  According to such an estimation calculation, a value can be given to an unknown parameter in the model, and the model can be imaged or a predetermined moment or the like can be calculated based on the model. That is, the evaluation value can be calculated as a predetermined moment from the two-dimensional distribution of the trabecular bone itself. In the above calculation, the diameter of the trabecular bone is a variable parameter. However, it is also possible to set the trabecular interval as a variable parameter on the assumption that the diameter of the trabecular bone is constant. It is also possible to set both the diameter and interval of the trabecular bone as variable parameters. In that case, when defining a trabecular space, a trabecular diameter, and the like, a necessary value may be given to the model based on the database as described above. Further, as described above, it is also possible to form a two-dimensional tomographic image as a schematic diagram according to the model and provide it to the user.

  As the predetermined moment, a cross-sectional secondary moment, a minimum cross-sectional secondary moment, a cross-sectional secondary pole moment, or the like known in the field of material mechanics can be used. Alternatively, other parameters that can indicate the degree of uneven distribution of physical quantities may be used.

  In the above-described embodiment, the ultrasonic beam may be further scanned along the Z direction orthogonal to the X direction and the Y direction, and the property value distribution may be acquired in the direction. It is also possible to obtain a predetermined moment including the result obtained thereby. In that case, the center of gravity calculation may be performed to calculate the moment around the center of gravity.

  In the above embodiment, the attenuation amount of the ultrasonic wave is used as the property value, but the sound speed of the ultrasonic wave and other information may be used instead. In measuring the property value, X-rays may be used instead of ultrasonic waves. Even in that case, it is possible to obtain the evaluation value using the same calculation principle as described above. When X-rays are used, ultrasonic measurements may be used in conjunction with the bone shape.

  According to each of the above-described embodiments, it is possible to measure information related to the internal structure of the bone with a simple configuration and a simple method without performing a measurement that generates a large exposure dose without using a large amount of X-ray CT apparatus or the like. That is, it is possible to obtain an evaluation value from a structural mechanical viewpoint for bone. In the case of a human subject, the target bone is preferably a rib containing a large amount of cancellous bone, but other bones may be used as the target bone. The trabecular model is also described in Patent Document 4 and Patent Document 5 described above, and the diameter and interval of the trabecular bone can be varied as described above based on the trabecular model described in such a document. You may make it handle as a parameter.

It is a figure for demonstrating a bone structure model. It is a figure for comparing and explaining a uniform model and an uneven distribution model. It is a figure which shows the whole structure of the bone evaluation apparatus which concerns on 1st Embodiment. It is a figure for demonstrating the effect | action in 1st Embodiment. It is a figure for demonstrating the analysis method regarding the shape of property value distribution. It is a figure for demonstrating the modification about 1st Embodiment. It is a figure for demonstrating the effect | action of the modification shown in FIG. It is a figure which shows the whole structure of the bone evaluation apparatus which concerns on 2nd Embodiment. It is a figure for demonstrating the effect | action of the bone evaluation apparatus which concerns on 2nd Embodiment.

Explanation of symbols

  10 soft tissue, 12 cortical bone, 14 cancellous bone, 18 trabecular bone, 20 bone marrow, 22 measuring unit, 24 arithmetic control unit, 36A, 36B transducer (ultrasonic transducer), 44 control unit, 46 arithmetic unit, over 50 Sonic beam,

Claims (10)

Beam scanning means for scanning a subject with a physical wave beam;
Based on a received signal obtained by scanning the physical wave beam, a property value calculating means for calculating a bone property value for each beam scanning position;
A property value distribution generating means for generating a property value distribution from the property values of the bone for each beam scanning position;
Evaluation value calculation means for calculating an evaluation value related to bone strength based on the property value distribution;
The bone evaluation apparatus characterized by including. The apparatus of claim 1.
The physical wave beam is an ultrasonic beam;
The beam scanning means is a means for mechanically or electronically scanning the ultrasonic beam,
The bone property evaluation apparatus is characterized in that the property value is a value related to ultrasonic attenuation or sound velocity. The apparatus of claim 1.
The said evaluation value calculating means calculates the said evaluation value based on the shape of the said property value distribution, The bone evaluation apparatus characterized by the above-mentioned. The apparatus of claim 3.
The bone evaluation value is characterized in that the evaluation value reflects a difference in height between a central portion and an end portion in the property value distribution. The apparatus of claim 3.
The bone evaluation apparatus characterized in that the evaluation value reflects an M-shaped degree of the property value distribution. The apparatus of claim 1.
Including a database where standard values are registered,
The said evaluation value calculating means calculates the said evaluation value by comparing the result value of the shape analysis about the said property value distribution with the standard value registered into the said database, The bone evaluation apparatus characterized by the above-mentioned. The apparatus of claim 1.
Means for measuring bone thickness at each beam scanning position;
The property value distribution generating means generates the property value distribution by normalizing a bone property value at each beam scanning position with a bone thickness at each beam scanning position. . The apparatus of claim 7.
The means for measuring the bone thickness includes means for obtaining a bone surface position by transmitting an ultrasonic wave to the bone surface and receiving a reflected wave from the bone surface. . First beam scanning means for scanning a subject with a first physical wave beam along a first direction;
Second beam scanning means for scanning the subject with a second physical wave beam along a second direction intersecting the first direction;
First property value calculating means for calculating a first property value of bone for each beam scanning position in the first direction based on a received signal obtained by scanning the first physical wave beam;
First property value distribution generating means for generating a first property value distribution from the first property value of the bone for each beam scanning position in the first direction;
Second property value calculating means for calculating a second property value of the bone for each beam scanning position in the second direction based on a reception signal obtained by scanning of the second physical wave beam;
Second property value distribution generating means for generating a second property value distribution from the second property value of the bone for each beam scanning position in the second direction;
Evaluation value calculation means for calculating an evaluation value related to bone strength based on the first property value distribution and the second property value distribution;
The bone evaluation apparatus characterized by including. The apparatus of claim 9.
The evaluation value calculating means calculates the evaluation value as a predetermined moment value defined from a spatial trabecular distribution inside the bone based on the first property value distribution and the second property value distribution. A bone evaluation device.

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