JP5839709B2 - Bone mineral content measuring apparatus and method - Google Patents

Description

  The present invention relates to a bone mineral content measuring apparatus and method, and more particularly to an apparatus and method for measuring a bone mineral density using a radiographic image obtained by imaging a bone part.

  Conventionally, for the diagnosis of osteoporosis and the like, a method of measuring the amount of bone mineral using a radiographic image obtained by photographing a bone part is known. Among such methods for measuring bone mineral content, an MD (Microdensitometry) method is known as one method that can be carried out relatively easily. The MD method basically irradiates radiation generated from a radiation tube simultaneously to a bone part to be measured and a standard substance having a plurality of parts having different radiation transmission characteristics, and transmits through the bone part and the standard substance. The radiographic image showing the bone part and the standard substance is obtained by detecting the detected radiation with a radiation detector such as an X-ray film. In this radiographic image, the radiation transmission characteristics of the part of the standard substance showing the same concentration as the bone part to be measured Based on the above, the bone mineral content of the bone part is obtained.

  Here, an aluminum scale whose thickness varies continuously is generally used as the standard substance. When such an aluminum scale is used, the thickness of the aluminum scale corresponding to the radiation transmission characteristics is often defined as an index indicating the amount of bone mineral.

  In addition, among the MD methods, a DIP (Digital Image) that uses a radiation detector that can obtain a digital image signal representing a radiographic image and processes the digital image signal to obtain a bone mineral content. Processing) method is widely known (see, for example, Patent Documents 1, 2, and 3). Measurement of the amount of bone mineral by the DIP method is becoming widespread because it is easy to operate and can be performed in a short time.

  In the measurement of the amount of bone mineral using a radiographic image as in the DIP method, the radiographic image is subjected to image processing for removing scattered radiation contained in the radiographic image to be measured or changing the density and contrast. (Patent Documents 4, 5, etc.). By performing image processing on the radiographic image in this way, it is possible to improve the accuracy of bone mineral content measurement and appropriately diagnose the displayed radiographic image.

On the other hand, in the measurement of bone mineral content, generalization of the measurement results can be compared with other measurement results, or compared with past measurement results accumulated for diagnosis of osteoporosis etc. Has been done. Thus, in order to compare with the past measurement results, the bone mineral content is measured by defining a certain part of a certain bone as a measurement region . In general, this region is a predetermined range of the second metacarpal bone of the left hand, that is, the metacarpal bone of the index finger (for example, a range covering a length of 1/10 of the total length of the bone at the center position in the longitudinal direction of the second metacarpal bone) ) In many cases. It is also conceivable to set a predetermined range of the second metacarpal bone of the right hand, not limited to the left hand.

  As described above, in order to measure the bone mineral density using the predetermined range of the second metacarpal bone of the left hand or the right hand as the measurement region, it is first necessary to specify the measurement region in the radiographic image. For this reason, conventionally, a user of a measurement apparatus designates a feature point such as an end of a measurement target part on a radiographic image displayed on a monitor, for example, by operating a mouse or the like, and a measurement region based on the designation input There are many things to identify. In addition, a method for automatically detecting feature points and specifying a measurement region has been proposed.

JP 2006-334046 A No. 2008-044439 JP 2010-200844 A JP 2011-245117 A JP 2010-233880 A

  By the way, in the method of automatically specifying the measurement region as described above, there are cases where feature points are detected with variations. In this case, bone mineral content may be measured at a site that is slightly different from the site that should be measured, and the measurement results obtained in this way are compared with past measurement results for diagnosis. If this is the case, a false diagnosis may be made. For this reason, it is preferable that the user confirms whether or not the position of the feature point and the measurement region are appropriate by displaying a radiographic image to which the detected feature point is added on a monitor or the like.

  However, since the displayed radiographic image has been subjected to image processing so as to be suitable for diagnosis as described above, the density and contrast of the area around the automatically detected feature point is the feature point. It may be inappropriate to confirm the position of the user, and it may be difficult for the user to determine whether the detected feature point is appropriate. In such a case, the user may change the image processing conditions for the image around the feature point by manual operation to improve the visibility so that the detected feature point and the measurement region can be easily confirmed. . However, performing such image processing manually is a heavy burden on the user.

  The present invention has been made in view of the above circumstances, and makes it easy to confirm the detection result of a measurement region or the like without placing a burden on the user when displaying a radiographic image used for measuring bone mineral content. Objective.

The bone mineral content measuring device according to the present invention is a bone mineral content measuring device that measures the bone mineral content of a bone part based on a radiographic image obtained by imaging the bone part.
An extraction means for extracting a measurement region in a bone to be measured for measuring bone mineral content from a radiographic image using a feature point in the bone to be measured ;
Image processing conditions for image processing applied to a partial image that is an image of a partial region so that the visibility of the partial region including the feature point of the bone to be measured in the radiographic image is higher than that of the region other than the partial region. Condition setting means to be set;
And image processing means for performing image processing on at least a partial image based on the set image processing conditions.

  “Applying image processing to at least a partial image” includes performing image processing not only on a partial image but also on an image including the partial image, for example, the entire radiation image.

  In the bone mineral content measuring apparatus according to the present invention, the image processing condition may be at least one of the spatial resolution, density, contrast, frequency enhancement degree, and display position of the partial image.

  Further, in the bone mineral content measuring apparatus according to the present invention, the condition setting means increases the spatial resolution, and corrects the average value of the pixel values of the partial images with respect to the density to a value near the middle of the display dynamic range, Means for setting the image processing conditions so that the maximum value and the minimum value of the pixel values of the partial image with respect to the contrast fall within the display dynamic range and the frequency enhancement degree is increased.

  The bone mineral content measuring apparatus according to the present invention may further include display control means for displaying the partial image and the radiographic image subjected to image processing on the display means.

  In the bone mineral content measuring apparatus according to the present invention, the display control means may be means for displaying a partial image in a portion other than the bone portion in the radiographic image.

  In the bone mineral content measuring apparatus according to the present invention, when the radiographic image includes a standard substance, the display control means may be a means for displaying a partial image in a portion other than the standard substance in the radiographic image.

  In the bone mineral content measuring apparatus according to the present invention, the display control means may be a means for enlarging and displaying the partial image.

  In the bone mineral content measuring apparatus according to the present invention, the display control means may be means for giving information indicating the position of the partial region to the radiation image.

Further, in the bone mineral content measuring device according to the present invention, the extraction means, bone specifying means for specifying the bone to be measured in the radiographic image,
Feature point detection means for detecting feature points in the bone;
Measurement area specifying means for specifying a measurement area in the bone based on the feature point may be provided.

Further, in the bone mineral content measuring device according to the present invention, in the radiographic image obtained by photographing the hand, the bone specifying means is a means for specifying the second metacarpal bone of the left hand as the bone to be measured,
The feature point detection means is a means for detecting points at both ends of the second metacarpal as feature points,
Means for specifying the measurement area specifying means as an area corresponding to 1/10 of the length of the second metacarpal bone in the central portion in the length direction of the second metacarpal bone based on the feature points It is good.

The bone mineral content measuring method according to the present invention is a bone mineral content measuring method for measuring the bone mineral content of a bone part based on a radiographic image obtained by imaging the bone part.
Extract the measurement area in the measurement target bone for measuring bone mineral content from the radiographic image using the feature points in the measurement target bone ,
Image processing conditions for image processing applied to a partial image that is an image of a partial region so that the visibility of the partial region including the feature point of the bone to be measured in the radiographic image is higher than that of the region other than the partial region. Set,
Image processing is performed on at least the partial image based on the set image processing conditions.

According to the present invention, with respect to a partial image that is an image of a partial region, the visibility of the partial region including the feature point of the bone to be measured in the radiographic image is higher than that of the region other than the partial region in the radiographic image. The image processing conditions of the image processing to be applied are set, and at least the partial image is subjected to image processing based on the set image processing conditions. For this reason, even if the user does not give an instruction to perform image processing, it is possible to make the partial area in the radiographic image easy to see, and thus the feature point and the measurement area are appropriate without imposing a burden on the user. It will be possible to confirm whether or not. Therefore, it is possible to improve the workflow when performing the bone mineral content measurement work.

Also, by displaying an enlarged partial image, the confirmation of the feature point can be easily performed.

  In addition, when a radiographic image is displayed by displaying a partial image on a part other than the bone part, or in a part other than the standard substance when the standard substance is included, the bone part or the standard substance in the radiographic image is It can prevent being disturbed.

  Further, by adding information indicating the position of the partial region to the radiographic image, it becomes easy to grasp the positional relationship between the partial region and the entire radiographic image.

The figure which shows schematic structure of the bone mineral content measuring system provided with the bone mineral content measuring apparatus by embodiment of this invention. Schematic showing an example of a radiographic image taken for bone mineral content measurement The figure explaining the measurement field where a radiographic image is extracted for bone mineral content measurement Diagram showing an example of the density profile of the radiation image in the measurement area Schematic block diagram showing the configuration of the part extraction unit Flowchart of processing for specifying a measurement region performed in the part extraction unit Flow chart of processing performed in this embodiment Diagram for explaining the setting of partial area The figure which shows the state which displayed the radiographic image and the partial image

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram illustrating a schematic configuration of a bone mineral content measurement system including a bone mineral content measurement device according to an embodiment of the present invention. The bone mineral content measurement system according to the present embodiment measures the bone mineral content by the above-described DIP method, and as shown in FIG. 1, by photographing a subject including a bone part that is a bone mineral content measurement target. The imaging device 10 that acquires the radiographic image G0 of the subject, the signal processing unit 20 that includes the bone mineral content measuring device according to the present embodiment that calculates the bone mineral content based on the radiographic image G0, and the signal processing unit 20 include various types. An input unit 30 for giving an instruction and a display unit 40 for displaying a bone mineral content measurement result and the like are included.

  The imaging apparatus 10 includes a radiation tube 12 that irradiates a subject H with radiation R, an imaging control unit 13 that controls driving of the radiation tube 12, and an imaging table 14 on which the subject H is placed. The imaging table 14 is provided with a radiation detector 11 that outputs a radiation detection signal of the subject H. The radiation detector 11 outputs a radiation detection signal corresponding to the energy level of irradiation radiation for each pixel arranged in a matrix. The detection signal is subjected to A / D conversion processing, and the radiation image G0 of the subject H is output. Is output as a digital image signal.

  As the radiation detector 11, for example, as described in JP-A-7-72253, a scintillator that emits visible light upon irradiation with radiation and a solid-state light detecting element that detects the visible light are used. What is laminated or has a radiation photoconductive layer that outputs an electrical signal corresponding to its energy upon irradiation with radiation, as described in, for example, JP-A-2010-206067 Can be applied.

  The signal processing unit 20 includes a preprocessing unit 21 to which a digital image signal representing the radiation image G0 is input, a site extraction unit 22 sequentially connected to the subsequent stage, a concentration analysis unit 23, a bone mineral content measurement unit 24, and a display control unit. 25, a storage unit 26, a condition setting unit 27, and an image processing unit 28.

  The input unit 30 includes, for example, a keyboard 31 and a mouse 32, and inputs various instructions from the user to the signal processing unit 20.

  The display unit 40 is composed of, for example, a liquid crystal display, a CRT display, or the like, and displays a bone mineral content measurement result and a radiographic image of the photographed subject as necessary.

  The signal processing unit 20, the input unit 30, and the display unit 40 described above can be configured from a computer system such as a general personal computer.

  Next, radiographic imaging for bone mineral content measurement will be described with reference to FIG. In capturing a radiographic image, the radiation detector 11 is placed on the imaging table 14 of the imaging apparatus 10, and the left and right hands of the subject who is the subject are placed on the radiation detector 11. Aluminum scale as material is placed. This aluminum scale is an aluminum plate-like member whose thickness changes continuously. Instead of this type of aluminum scale, an aluminum plate member whose thickness changes stepwise may be used.

  By operating the imaging control unit 13 in this state, the radiation tube 12 is driven, and the radiation R is irradiated to the radiation detector 11 through the left hand, the right hand, and the aluminum scale. In the DIP method, the radiation tube 12 is usually imaged with a tube voltage of 50 kV. In this embodiment, the tube voltage is set to 50 kV by the imaging control unit 13 as well. However, since the effective tube voltage tends to decrease with time, the effective tube voltage may not reach 50 kV even if it is set as described above. For this reason, in this embodiment, as will be described later, measurement errors are prevented from occurring.

  When imaging is completed, a digital image signal representing the radiation image G0 is acquired from the radiation detector 11. This radiation image G0 can be reproduced and displayed on the display unit 40, and when displayed, the radiation image is as shown in FIG. As shown in FIG. 2, in the displayed radiation image G0, the left hand LH, the right hand RH, and the aluminum scale AS of the subject who is the subject are recorded. The aluminum scale AS is set on the radiation detector 11 such that the aluminum scale AS becomes gradually thinner in the fingertip direction (upward in FIG. 2) of the left hand LH and the right hand RH.

  The radiation image G0 is input to the preprocessing unit 21 of the signal processing unit 20. When the image capturing apparatus 10 performs image capturing, the image capturing control unit 13 obtains identification information indicating the image capturing apparatus 10, tube voltage information, identification information indicating the radiation detector 11, information indicating the image capturing order, subject ID, and the like. The included imaging information Sc is input to the preprocessing unit 21 and the bone mineral content measurement unit 24 of the signal processing unit 20.

  Next, processing performed by the signal processing unit 20 will be described. The radiation image G0 input to the signal processing unit 20 is first subjected to radiation for processing and diagnosis in the preprocessing unit 21 for correcting signal value fluctuations caused by radiation irradiation unevenness, detection unevenness of the radiation detector 11, and the like. Image processing for improving the image quality of the image G0 and other processing appropriately performed as necessary are input to the part extraction unit 22. The radiation detector 11 is specified based on identification information indicating the radiation detector 11 included in the imaging information Sc. The image processing is performed using the maximum value, the minimum value, and the average value of the pixel values of the radiation image G0. For example, with respect to the density, image processing conditions are set and image processing is performed so that the average value of the pixel values is a value near the middle of the display dynamic range of the display unit 40. For contrast, a gradation curve is set as an image processing condition so that the maximum value and the minimum value of the pixel value are within the display dynamic range, and image processing is performed.

  The site extraction unit 22 specifies a site for bone mass measurement from the radiographic image G0 automatically by image processing or based on an instruction from the input unit 30. In the DIP method, since the bone mineral content is usually measured for the left second metacarpal bone B2L shown in FIG. 2, the second metacarpal bone B2L of the left hand is also specified in this embodiment. More specifically, an h / 10 measurement region (a region indicated by hatching in FIG. 3) in the central portion of the entire length of the left hand second metacarpal bone B2L is specified. In the present embodiment, the measurement area is automatically specified. The measurement area specifying process will be described later.

  Next, the concentration analysis unit 23 obtains an average concentration in the measurement region. More specifically, the concentration analysis unit 23 obtains a concentration profile in the direction crossing the left hand second metacarpal bone B2L in the measurement region. When this density profile is shown using luminance instead of density, it becomes as shown by a curve Q in FIG. Note that D shown in FIG. 4 is the bone width. Such a concentration profile is first obtained for, for example, about a dozen or so places distributed over the length direction of the bone in the measurement region, and then obtained by calculating an average profile thereof.

  The concentration in the average concentration profile is directly converted to the thickness of the aluminum scale (aluminum thickness). That is, the thickness of the aluminum scale portion having the same density as each point density of the profile in the radiation image G0 is obtained, and the integrated value (shaded portion in FIG. 4) ΣGS of the aluminum thickness converted value is divided by the bone width D. ΣGS / D [unit: mmAL (aluminum)] is calculated as a DIP value indicating the amount of bone mineral. Regarding the DIP value, for example, the Japanese bone metabolism society has published a standard value for each gender and age group, and the bone mineral content is in the normal range if it falls within the range of 100 to 80% of the standard value. It is supposed to be lowered.

  However, the above DIP value = ΣGS / D is different from the case where the same bone part is obtained as described above even when the effective bone voltage at the time of photographing is other than 50 kV. May indicate a value. The reference value described above is determined for the DIP value when the radiation detector 11 is used and the tube voltage is set to 50 kV and a radiographic image is taken. If a diagnosis relating to the amount of salt is made, it is necessary to correct the DIP values indicating different values as described above so as to correspond to the DIP values when the tube voltage is set to 50 kV.

  The bone mineral content measuring unit 24 calculates DIP value = ΣGS / D from the input digital image signal of the radiation image G0. That is, the bone mineral content measuring unit 24 converts the density in the average density profile (Q in FIG. 4) indicated by the radiation image G0 into the thickness of the aluminum scale (aluminum thickness), and the integrated value of the aluminum thickness converted value. A value ΣGS / D obtained by dividing ΣGS by the bone width D is calculated as a DIP value. If necessary, the DIP value is corrected according to the tube voltage included in the imaging information Sc, and the characteristic of the imaging device 10 is obtained based on the identification information of the imaging device 10, and the DIP value is determined according to this characteristic. to correct. The bone mineral content measurement unit 24 inputs information indicating the DIP value = ΣGS / D measured in this way to the display control unit 25. The display control unit 25 displays this DIP value on the display unit 40.

  In accordance with the DIP value displayed on the display unit 40 as described above, the display of the diagnosis result based on the comparison with the reference value, for example, the display of the ratio to the reference value, or the display of “no fear of osteoporosis”, etc. You may make it carry out together.

  Next, a method for specifying the measurement region indicated by hatching in FIG. 3 will be described. FIG. 5 is a schematic block diagram showing the configuration of the part extracting unit 22.

  As shown in FIG. 5, the part extracting unit 22 detects a bone specifying unit 50 that specifies a second metacarpal bone that is an example of a bone to be measured, and a feature point in the specified second metacarpal bone. A feature point detection unit 51 and a measurement region specifying unit 52 that specifies a measurement region based on the feature points are provided.

  FIG. 6 is a flowchart of processing for specifying a measurement region performed in the part extraction unit 22. When the measurement target radiation image G0 that has been preprocessed by the preprocessing unit 21 is input to the part extraction unit 22, the bone specifying unit 50 specifies the left hand from the measurement target radiation image G0 (step ST1). As shown in the radiation image G0 in FIG. 2, the left hand is identified by image processing in accordance with a rule at the time of photographing that the aluminum scale AS is arranged so that the cutout portion CC faces the left hand LH. This is performed by recognizing the hand facing the notch CC of the scale AS as the left hand.

  Here, a method for recognizing the position and orientation of the aluminum scale AS will be described with an example. For example, if the shape pattern of the aluminum scale AS is stored in the storage unit 26 and a known pattern recognition process is applied, the presence or absence of the aluminum scale AS and the position when the presence of the aluminum scale AS is confirmed can be recognized. it can. The direction of the aluminum scale AS, that is, the direction in which the cutout portion CC is directed is determined by applying a positioning method including the pattern of the cutout portion CC, or the two long sides of the aluminum scale AS. Can be specified by applying a method in which the longer total length of the edges is the longer side having the cutout portion CC.

  Next, the bone specifying unit 50 specifies the second metacarpal bone B2L (see FIG. 2) from the plurality of bones included in the specified left hand (step ST2). For this specification, a template search method using linear alignment such as affine transformation, or non-linear alignment such as morphing, in particular, a model based on multi-resolution alignment as described in Japanese Patent Application Laid-Open No. 2011-255060. It can be performed by applying a template search method or the like by fitting.

  The above-mentioned multi-resolution alignment is a conventionally known method, but the outline will be described in accordance with the procedures (1) to (5) described below.

(1) First, a template image (an image including the first and second metacarpal bones in the present embodiment) and a reference image (an image of the left hand in the radiation image G0 in the present embodiment) are each decomposed into a plurality of resolutions. (Laplacian pyramid, wavelet transform, etc.)

(2) For each resolution image, a shift vector is obtained by selecting a location having a maximum cross-correlation coefficient while searching for pixels.

(3) When obtaining the shift vector, the shift vector is calculated using the cross-correlation or the like in the lowest resolution (coarse) image, and the next lowest resolution image is the position of the shift vector used in the lowest resolution image. Is an initial value, and similarly, a shift vector for the next lower resolution image is calculated by cross-correlation or the like.

(4) The shift vectors for all the pixels of the target image are calculated by repeating the processes (1) to (3) up to a predetermined resolution.

(5) Further, based on the shift vector calculated at each resolution, each resolution image (either a template image or a reference image) to be deformed is deformed and reconstructed to obtain a deformed image. In the present embodiment, it is more convenient to deform the template image in order to ensure the accuracy of bone mineral content measurement. As another method, there is a method of deforming an image with the shift vector finally obtained in (4). As such a method, for example, as shown in the following reference, a final shift vector may be modified collectively.

《References》
GJ Gang, CA Varon, H. Kashani, S. Richard, NS Paul, R. Van Metter, J. Yorkston, JH Siewerdsen, "Multiscale deformable registration for dual-energy x-ray imaging," Medical Physics 36: 351-363 (2009).
As described above, the template image including the first and second metacarpal bone images is searched with respect to the image of the left hand extracted from the radiation image G0, and the template is deformed and aligned. The portions of the first and second metacarpal bones in the image can be identified.

  Next, the feature point detector 51 detects a feature point in the second metacarpal bone B2L (step ST3). In the present embodiment, this feature point is, for example, the center point, both end points, or the center of gravity point of the second metacarpal bone B2L shown in FIG. Such feature points are identified by using, for example, a region including the second metacarpal bone and the first metacarpal bone of the left hand as a template, adding a landmark to the template, and a landmark that becomes a predetermined feature point by deformation. And a method of assigning a model (contour of bone) to a template and deforming the contour to identify a feature point can be applied.

  Here, an outline of the technique using the landmark will be described. For example, when the feature point is a center point, the center point is defined as a landmark in the template of the second metacarpal bone, and the center point (one of the ones based on the shift vector obtained between the template and the radiation image G0 is defined. It can be specified by moving (specific pixel position). Similarly, if both end points (different specific pixel positions) are defined as landmarks, the two pixel positions are moved based on the calculated shift vector, and become the two end points of the second metacarpal bone in the reference image. Further, when the contour line of the second metacarpal bone of the template is defined as a landmark, the contour line is moved and deformed by the shift vector to become the contour line of the second metacarpal bone of the reference image. When obtaining the center of gravity as a feature point from here, the center of gravity of this contour line (closed curve) is obtained.

  As described above, when the region including the second metacarpal bone and the first metacarpal bone of the left hand is used as a template, the two metacarpal bones form an angle of a predetermined angle (for example, 20 °) or more. It is preferable to recognize the first metacarpal bone and the second metacarpal bone based on the fact that As a result, this recognition is correctly performed with a very high probability.

  In the present embodiment, the measurement region (the region indicated by hatching in FIG. 3) may be specified based on the feature points detected as described above, but in this embodiment, the measurement region is higher. In order to specify with accuracy, both end points of the second metacarpal bone B2L are detected as two feature points, and a measurement region is specified based on the two feature points. Hereinafter, this process will be described.

  The feature point detection unit 51 detects both ends of the second metacarpal bone B2L specified in step ST2 as feature points. This feature point is detected by detecting the most distant point on the joint surface, for example. More specifically, in consideration of the shape of the second metacarpal bone B2L, a standard model of the joint surface with a convex shape on the fingertip side and a concave shape on the wrist side is applied, and the standard model shape is The two most distant points of the joint surface, that is, the second metacarpal bone, are obtained by a model fitting technique in which the deformation is fitted to the joint of the radiation image G0 while being constrained (maintained) and the correspondence between the model and the image is obtained. Both ends of B2L are detected as feature points. Here, among the detected feature points, the feature point on the fingertip side is the distal point Pd, and the feature point on the wrist side is the proximal point Pp. Note that, as the model fitting method, specifically, the above-described model fitting by multi-resolution alignment or the like can be applied.

  Then, the region extraction unit 22 determines the midpoint of the second metacarpal bone B2L, which is the midpoint between the two feature points Pd and Pp (step ST4). This midpoint is for obtaining the center line CL in the bone length direction shown in FIG.

  Based on the midpoint, the measurement region specifying unit 52 specifies a region indicated by hatching in FIG. 3 as a measurement region (step ST5). This specification is performed, for example, by a method of obtaining a center line CL in the length direction of the bone from the midpoint, and setting an area of h / 20 from the center line CL to both ends of the bone.

  In the present embodiment, the detected feature point is displayed on the display unit 40 together with the radiographic image of the left hand including the second metacarpal bone B2L, and it is possible to confirm whether the feature point is correctly detected. Become. Further, the displayed feature points may be moved based on an instruction from the input unit 30 in FIG. 1, or the outline of the bone part and the ROI may be deformed.

  At this time, in the present embodiment, image processing for facilitating confirmation of feature points is performed. Hereinafter, processing performed in the present embodiment including this image processing will be described. FIG. 7 is a flowchart of processing performed in the present embodiment. When the radiation image G0 is input from the imaging apparatus 10 to the signal processing unit 20, the preprocessing unit 21 performs preprocessing (step ST11), and the region extraction unit 22 specifies the measurement region as described above (step ST12). .

Here, in the present embodiment, the preprocessing unit 21 performs image processing (hereinafter referred to as first image processing) for improving the image quality on the radiation image G0. The processing is image processing for facilitating diagnosis. As described above, the measurement area is Oite identified in the second metacarpal bone, the shape of the bone, particularly since the shape of the joint is complicated, feature points as in the present embodiment of the second metacarpal bone When detecting at both ends, the position of the feature point may be difficult to confirm even if the radiation image G0 subjected to the first image processing is displayed on the display unit 40.

For this reason, in this embodiment, when the part extraction part 22 specifies a measurement area | region, the condition setting part 27 will make the partial area | region containing the feature point of the 2nd metacarpal bone of the measurement object in the radiographic image G0 into the radiographic image G0. Set (step ST13). In the present embodiment, since the two feature points Pd and Pp are detected, as shown in FIG. 8, the partial region A1 including the distal point Pd and the partial region A2 including the proximal point Pp are set. Partial region A1 includes the second metacarpal bone B2L and soft tissue near the distal point Pd, and partial region A2 includes the second metacarpal bone B2L and soft tissue near the proximal point Pp.

  The condition setting unit 27 then displays the partial images in order to increase the visibility of the images of the partial areas A1 and A2 (hereinafter referred to as partial images B1 and B2) more than the areas other than the partial areas A1 and A2 in the radiation image G0. Image processing conditions for image processing (hereinafter referred to as second image processing) performed on B1 and B2 are set (step ST14). The image processing conditions may include at least one of the spatial resolution, density, contrast, frequency enhancement degree, and display position of the partial images B1 and B2. In the present embodiment, all of these image processing conditions are included. Shall be set.

  Specifically, the condition setting unit 27 sets the image processing conditions so as to increase the spatial resolution for the spatial resolution. Increasing the spatial resolution means increasing the spatial resolution of the partial images B1 and B2 than the radiation image G0 displayed on the display unit 40. For this reason, when the whole radiation image G0 is displayed on the display part 40, partial image B1, B2 will be expanded rather than partial area A1, A2 in radiation image B0 by making spatial resolution high.

  On the other hand, for the density, an average value of pixel values of each pixel included in the partial images B1 and B2 is calculated, and the partial image is set so that the average value is a value near the middle of the display dynamic range of the display unit 40. A correction amount for correcting the pixel value of each pixel of B1 and B2 is set as an image processing condition. Even in the first image processing, the correction amount of the pixel value is set so that the average value of the pixel values becomes a value near the middle of the display dynamic range for the density, but the average value of the pixel values is calculated. It differs from the second image processing in that the target is the entire radiation image G0.

  As for the contrast, the gradient of the gradation curve is set as the image processing condition so that the maximum value and the minimum value of each pixel of the partial images B1 and B2 are within the display dynamic range of the display unit 40. In the first image processing as well, for the contrast, the gradient of the gradation curve is set so that the maximum and minimum pixel values are within the display dynamic range, but the maximum and maximum pixel values are The second image processing is different from the second image processing in that it is the radiation image G0.

  As for the frequency enhancement level, since the feature points in the second metacarpal are included in the partial images B1 and B2, it is confirmed whether or not the feature points are located on the edge of the second metacarpal. It is important to do. For this reason, the frequency enhancement degree is set so as to emphasize the relatively high frequency spatial frequency components corresponding to the edges of the partial images B1 and B2.

Measurement for the display position, the left hand to the radiation image G0, includes right hand and aluminum scales, measurement area is Oite identified in the second metacarpal bone of the left hand, the aluminum scale for bone mineral density measurement A comparison is made with the bone concentration in the area. Therefore, when displaying the partial images B1 and B2 for confirmation, if the partial images B1 and B2 overlap the left hand and the aluminum scale in the radiation image G0, the density of the bone part and the density of the aluminum scale in the measurement region Cannot be compared. For this reason, the display position is set such that the partial images B1 and B2 are displayed so as not to overlap the left hand and the aluminum scale in the radiation image G0.

  When the image processing conditions are set in this way, the image processing unit 28 performs image processing on the partial images B1 and B2 according to the set image processing conditions (step ST15). Of the image processing conditions, the display position is not applied to the partial images B <b> 1 and B <b> 2, and information on the image processing conditions is output to the display control unit 25. Then, the display control unit 25 displays the partial images B1 and B2 on which the image processing has been performed on the display unit 40 by superimposing them on the set display position on the radiation image G0 (partial image display, step ST16).

  Here, the partial images B1 and B2 have a higher proportion of bone parts than the radiographic image G0, and thus include a large number of high-luminance pixel values. For this reason, as described above, by setting the image processing conditions of the spatial resolution, density, contrast, and frequency enhancement degree, the edges of the bone parts included in the partial images B1 and B2 are emphasized, and the bone parts with higher brightness are further enhanced. Therefore, in the partial images B1 and B2, the shape of the bone part and the positions of the feature points detected at both ends of the bone part can be easily confirmed.

  FIG. 9 is a diagram showing a state in which the radiation image G0 and the partial images B1 and B2 are displayed. As shown in FIG. 9, partial images B1 ′ and B2 ′ are displayed on the display unit 40 so as to be superimposed on the radiation image G0 in a portion that does not overlap the left hand LH and the aluminum scale AS in the radiation image G0. Here, the partial images B1 ′ and B2 ′ are enlarged than the partial areas A1 and A2 because the image processing is performed so as to increase the spatial resolution. The partial images B1 ′ and B2 ′ may be further enlarged and displayed. Further, on the left hand LH, a rectangular frame indicating the partial areas A1 and A2 is displayed as information indicating the positions of the partial areas A1 and A2. In order to make it easy to understand which partial area corresponds to which partial image, the color of the frame of the corresponding partial area may be the same. For example, the frames of the partial area A1 and the partial image B1 ′ may be changed to red, and the frames of the partial area A2 and the partial image B2 ′ may be changed to green.

  The user can confirm whether or not the feature point is properly detected by viewing the partial images B1 ′ and B2 ′ displayed in this way. If necessary, the position of the feature point can be corrected using the input unit 30. For this reason, the signal processing unit 20 determines whether or not a feature point correction instruction has been issued (step ST17). When step ST17 is affirmed, in order to set a measurement region again with the corrected feature point, The process returns to step ST12. If step ST17 is negative, the bone mineral content measurement unit 24 calculates a DIP value based on the specified measurement region (step ST18), and the display control unit 25 displays the DIP value on the display unit 40 (step ST18). ST19) The process is terminated.

As described above, in the present embodiment, the partial image is configured so that the visibility of the partial areas A1 and A2 including the feature points of the bone to be measured in the radiographic image is higher than that of the area other than the partial area in the radiographic image G0. Image processing conditions for image processing performed on B1 and B2 are set, and image processing is performed on partial images B1 and B2 based on the set image processing conditions. For this reason, even if the user does not give an instruction to perform image processing, the partial areas A1 and A2 in the radiation image G0 can be made easier to see than the other areas. It is possible to confirm whether the feature points and the measurement area are appropriate. Therefore, it is possible to improve the workflow when performing the bone mineral content measurement work.

Further, since the partial images B1 and B2 are enlarged and displayed, the feature points can be easily confirmed.

  In addition, since the partial images B1 and B2 are displayed in a portion other than the bone portion and a portion other than the aluminum scale AS, the bone portion or the standard substance in the radiation image G0 is disturbed by the partial images B1 and B2. Can be prevented.

  In addition, by adding a rectangular frame to the partial area in the radiation image G0, it becomes easy to grasp the positional relationship between the partial area and the entire radiation image.

  In the above embodiment, the enlarged partial images B1 'and B2' are displayed superimposed on the radiation image G0, but image processing for increasing the spatial resolution is not performed on the partial images B1 and B2. Alternatively, the radiation image G0 may be displayed by replacing the partial areas A1 and A2 shown in FIG. 8 with the partial images B1 and B2 subjected to the image processing. In this case, since the image quality of the part in which the partial images B1 and B2 in the radiation image G0 are replaced is different from the surrounding areas, a frame is added to the partial areas A1 and A2 and the partial areas A1 and A2 as in the above embodiment. It is preferable to make the position of the intelligible.

  In the above embodiment, image processing is performed only on the partial images B1 and B2 according to the image processing conditions set by the condition setting unit 27. However, the condition setting unit 27 is applied to the entire radiation image G0. The image processing may be performed according to the image processing conditions set by. In this case, the radiographic image G0 that has been subjected to image processing is not suitable for diagnosis because the feature points are easily confirmed. For this reason, when making a diagnosis after confirming a specific point, it is preferable to display on the display unit 40 a radiation image G0 that has not been subjected to image processing based on the image processing conditions set by the condition setting unit 27.

  Moreover, in the said embodiment, although the frame is provided to partial area A1, A2 in the radiographic image G0, if it is the information showing the position of partial area A1, A2, it will not be limited to a frame, For example, An arrow or the like may be displayed instead of the frame.

  Moreover, in the said embodiment, although partial area A1, A2 containing each of the detected two feature points is set, you may set one partial area containing two feature points.

  In the above embodiment, the image processing conditions are set and image processing is performed on the partial images B1 and B2 after the measurement region is specified. After the feature points before the measurement region is specified, the partial image is detected. The image processing conditions for B1 and B2 may be set and image processing may be performed.

  Moreover, in the said embodiment, although the point of the both ends of 2nd metacarpal B2L is detected as a feature point, you may detect the center point or gravity center point of 2nd metacarpal as a feature point. In this case, the partial region is a region including the center point or the center of gravity of the second metacarpal bone.

  In the above embodiment, the measurement region in the second metacarpal bone B2L of the left hand is specified, but the measurement region in the second metacarpal bone of the right hand can also be specified. .

  Furthermore, this embodiment can also be applied when the bone to be measured is a bone other than the second metacarpal bone. That is, for example, if landmarks such as center points and both end points are defined in the bone portion to be measured on the template, the positional relationship between the first metacarpal bone and the second metacarpal bone as described above. Therefore, it is possible to correctly identify bones to be measured other than the second metacarpal bone by accurately recognizing these and other fingers and deforming and moving the landmarks.

  In the above-described embodiment, the bone mineral content is measured using the radiographic image acquired by the imaging apparatus 10 that captures the radiographic image of the subject using the radiation detector 11, but JP-A-8-266529 is disclosed. A radiation image obtained by accumulating and recording radiation image information of a subject on a stimulable phosphor sheet as a radiation detector shown in Japanese Patent Application Laid-Open No. 9-24039, etc., and photoelectrically reading from the stimulable phosphor sheet Of course, the present invention can also be applied when measuring the amount of bone mineral.

  In addition, as described above, a procedure for specifying a measurement region, a procedure for setting image processing conditions for a partial image, and a procedure for performing image processing on a partial image based on the set image processing conditions Can be recorded on a computer-readable recording medium, and each procedure can be executed by the computer using the recording medium.

DESCRIPTION OF SYMBOLS 10 Imaging apparatus 11 Radiation detector 12 Radiation tube 13 Imaging control part 14 Imaging stand 20 Signal processing part 21 Pre-processing part 22 Site extraction part 23 Concentration analysis part 24 Bone salt amount measurement part 25 Display control part 26 Storage part 27 Condition setting Unit 28 image processing unit 30 input unit 40 display unit 50 bone specifying unit 51 feature point detecting unit 52 measurement region specifying unit

Claims (11)

In the bone mineral content measuring device for measuring the bone mineral content of the bone part based on the radiographic image obtained by imaging the bone part,
The measurement area in the bone to be measured for measuring the pre-Symbol bone mineral density, and extracting means for extracting from the radiation image using the feature points in the bone of the measurement object,
In the radiographic image, performs the visibility of the partial area including the feature point of the bone of the measurement target, for the previous SL to increase than the region other than the partial region, the partial image is an image of the partial area image Condition setting means for setting image processing conditions for processing;
An apparatus for measuring the amount of bone mineral, comprising: image processing means for performing image processing on at least the partial image based on the set image processing conditions.   The bone mineral content measuring apparatus according to claim 1, wherein the image processing condition is at least one of a spatial resolution, a density, a contrast, a frequency enhancement degree, and a display position of the partial image. The condition setting means increases the spatial resolution, corrects the average value of the pixel values of the partial image with respect to the density to a value near the middle of the display dynamic range, and sets the pixel value of the partial image with respect to the contrast. like the maximum and minimum values and fits into the display dynamic range, so as to increase the frequency enhancement degree, according to claim 1, wherein it is a means for setting the image processing conditions Bone mineral content measuring device.   The bone mineral content measuring apparatus according to any one of claims 1 to 3, further comprising display control means for displaying the partial image and the radiographic image subjected to the image processing on a display means.   The bone mineral content measuring apparatus according to claim 4, wherein the display control means is means for displaying the partial image in a portion other than the bone portion in the radiographic image.   6. The bone mineral according to claim 4, wherein, when the radiographic image includes a standard substance, the display control means is a means for displaying the partial image in a portion other than the standard substance in the radiographic image. Quantity measuring device.   The bone mineral content measuring apparatus according to any one of claims 4 to 6, wherein the display control means is means for enlarging and displaying the partial image.   The bone mineral content measuring apparatus according to claim 6 or 7, wherein the display control means is means for giving information indicating a position of the partial region to the radiation image. The extracting means includes a bone identifying means for identifying bone of the measurement object in the radiation image,
A feature point detection means for detecting the feature points in the bone,
The bone mineral content measuring device according to any one of claims 1 to 8, further comprising a measurement region specifying unit that specifies a measurement region in the bone based on the feature point. In the radiographic image obtained by photographing the hand, the bone specifying means is a means for specifying the second metacarpal bone of the left hand as the bone to be measured,
The feature point detection means is means for detecting points at both ends of the second metacarpal as feature points,
The measurement region specifying unit is configured to measure a region corresponding to 1/10 of the length of the second metacarpal bone in a central portion in the length direction of the second metacarpal bone based on the feature point. The bone mineral content measuring device according to claim 9, wherein the bone mineral content measuring device is a means for specifying the region. In the bone mineral content measuring method for measuring the bone mineral content of the bone part based on the radiographic image obtained by imaging the bone part,
The measurement area in the bone to be measured for measuring the pre-Symbol bone mineral density, with the characteristic points in the bone of the measurement target is extracted from the radiation image,
In the radiographic image, performs the visibility of the partial area including the feature point of the bone of the measurement target, for the previous SL to increase than the region other than the partial region, the partial image is an image of the partial area image Set the image processing conditions for processing,
A bone mineral content measuring method, wherein image processing is performed on at least the partial image based on the set image processing conditions.

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