JP3974842B2 - X-ray bone density measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for measuring a bone density distribution of a subject using X-rays.
[0002]
[Prior art]
An X-ray bone density measuring device that calculates bone density by transmitting X-rays through a subject has been conventionally used in many medical institutions for bone disease diagnosis and prevention. As is well known, bones are composed of minerals such as calcium (bone mineral) that attenuate X-rays, and the bone density per unit area is calculated by calculating the amount of attenuation (attenuation rate) during X-ray transmission. Is done. Bone is covered with soft tissues such as muscles and fats, and X-ray attenuation also occurs in those parts. In order to eliminate the influence of such soft tissue, two types of energy X-rays are used in the conventional bone density measuring apparatus. In this method, the attenuation of each bone part and soft tissue is specified by solving simultaneous equations based on the attenuation calculated for each energy. This method is called a double X-ray absorption measurement method (DXA method). The principle of bone density calculation by the DXA method will be described with reference to FIG. FIG. 5 shows the distribution of attenuation when X-rays of two types of high and low energy are transmitted through the subject 10 whose soft tissue 14 covers the periphery of the bone part 12 as shown in FIG. Shown in (a). As can be seen from the figure, the attenuation of bone and soft tissue is higher in low energy X-rays than in high energy X-rays, but the ratio of attenuation between the two energies is clear between bone and soft tissues. Different. Therefore, in the DXA method, the ratio α of the attenuation amount of the low energy X-ray to the attenuation amount of the high energy X-ray with respect to the soft tissue is obtained, and α is added to the attenuation amount of the high energy X-ray from the attenuation amount of the low energy X-ray. By subtracting the multiplied value, the attenuation amount of only the bone portion is obtained and converted into the bone density (in this case, the amount of bone mineral per unit area). Patent Documents 1 and 2 show an example of a bone density measuring apparatus using such a technique.
[0003]
In this type of bone density measuring device, for example, the bone density at each point when the subject is two-dimensionally projected is obtained by detecting by irradiating X-rays from above to below the subject lying on the bed. This two-dimensional distribution can be displayed.
[0004]
In addition, some conventional DXA bone density measuring apparatuses can display not only bone parts but also soft tissues for the purpose of easily grasping the outer shape and the like of a subject. That is, in the general bone density calculation, the ratio α is used so that the value of the soft tissue becomes 0 as described above. However, if the value of α is a smaller value, the soft tissue also has a positive value. Therefore, if a display image is formed using such a small α, a display that also represents a soft tissue can be obtained.
[0005]
[Patent Document 1]
Japanese Patent No. 2735507
[Patent Document 2]
Japanese Patent No. 3256667
[0006]
[Problems to be solved by the invention]
In recent years, an X-ray bone density measuring device has also been used for confirmation of drug effects using animals such as rats and mice. For example, an example of measuring a bone density distribution using an X-ray bone density measuring device is known in order to examine the influence of changes in the amount of muscle and fat caused by a thinning drug on bones. In this application, it is very convenient to know the relationship between the distribution of body fat percentage and the bone density distribution. However, there is no conventional bone density measuring device having a function of displaying both such distributions in association with each other.
[0007]
Here, the soft tissue display shown in the above prior art can display not only the bone density distribution but also the soft tissue around the bone part to some extent. The value of the soft tissue shown in this display is an X-ray by the soft tissue. The amount of attenuation is converted to a bone density scale and does not represent body fat percentage. For example, the body fat percentage generally tends to be higher in the body side part (flank, etc.), but since the body side part has a small body thickness, the attenuation of X-rays becomes small. Becomes a small value equivalent to that of the outside of the subject and does not represent the state of body fat percentage.
[0008]
This invention is made | formed in view of such a problem, and it aims at providing the X-ray bone density measuring apparatus which can show the relationship between a bone density and a body fat percentage in an easy-to-understand manner.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, an apparatus according to the present invention detects X-rays transmitted through a subject and obtains a two-dimensional distribution of X-ray attenuation based on the detection results, A discriminating means for discriminating between a bone part and a soft tissue of a subject; a bone density calculating means for obtaining a bone density distribution of the bone part from the two-dimensional distribution; and a body fat percentage distribution of the soft tissue from the two-dimensional distribution. Body fat percentage calculation means to be obtained; and synthesis means for synthesizing and outputting the bone density distribution of the bone part and the body fat percentage distribution of the soft tissue into one image.
[0010]
In this configuration, a bone density distribution is obtained for the bone part and a body fat percentage distribution is obtained for the soft tissue from the two-dimensional distribution of attenuation, and both are combined to generate one image. Therefore, since the user can list the bone density distribution and the body fat percentage distribution by the image, it becomes easy to analyze the relationship between the bone density and the body fat percentage.
[0011]
In a preferred aspect, the measurement means obtains a two-dimensional distribution of the attenuation amount for each of two different energy X-rays, and the bone density calculation means calculates the two-dimensional distribution from the two-dimensional distribution for the X-rays of each energy. A bone density distribution is obtained according to a heavy X-ray absorption measurement method, and the body fat percentage distribution calculating means has information on the correspondence between the ratio of X-ray attenuation of each energy and the body fat percentage, and the two-dimensional The body fat percentage distribution is obtained by obtaining a ratio between X-ray attenuation amounts of each energy at each point from the distribution and obtaining a body fat percentage corresponding to the ratio from the information of the correspondence relationship.
[0012]
In another preferred aspect, the synthesizing unit assigns different display form ranges to the bone density distribution and the body fat percentage distribution, and sets the bone density and the body fat percentage within the corresponding display form ranges. Expressed in display form. According to this aspect, it is possible to generate an image in which the bone density and the body fat percentage can be easily distinguished from each other.
[0013]
In still another preferred aspect, the body fat percentage distribution calculating means calculates the ratio of the X-ray attenuation of each energy at each point from the two-dimensional distribution. Among these, the attenuation value of the two-dimensional distribution for the X-ray having the lower energy is corrected. According to this aspect, it is possible to perform appropriate attenuation correction that matches the characteristics of the soft tissue.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.
[0015]
The X-ray bone density measuring apparatus of the present embodiment has a function of obtaining a bone density distribution and a body fat percentage distribution of a subject, and combining and displaying them on a single image. This device may have almost the same hardware configuration as the conventional DXA method bone density measuring device, and the calculation of the body fat percentage distribution and the generation of the composite image are typically realized by software ( Of course, it is not impossible to make a part or all of the calculation and image generation processing into a hardware circuit).
[0016]
First, the hardware configuration of the X-ray bone density measuring apparatus to which the simultaneous display system of bone density and body fat percentage according to the present invention is applied will be described with reference to FIG.
[0017]
This bone density measuring device is a measuring device that measures the bone density distribution of the trunk of a subject 10 such as a rat, and the subject 10 is placed on a bed 16 that is fixedly arranged. Actually, there is a mechanism for fixing the small animal to the bed 16, but the illustration is omitted in the figure to avoid complication. The subject 10 is a living body, and the bone 12 is covered with a soft tissue 14 made of muscle or fat. In the present embodiment, an X-ray generator 18 is provided below the bed 16, and an X-ray detector 22 is disposed above the bed 16. The X-ray generation device 18 is a device that generates high energy X-rays or low energy X-rays as required, and the X-ray detection device is a device that detects the X-rays 100 that have passed through the subject 10. The X-ray generator 18 and the X-ray detector 22 are driven in the horizontal direction integrally by the scanning device 24. For example, the entire body of the subject is scanned by zigzag scanning to detect transmitted X-rays.
[0018]
The control unit 26 controls the operation of the apparatus, and executes various calculations described later. Processing such as calculation of bone density and body fat percentage, generation of a composite display image, and the like are also realized by arithmetic processing of the control unit 26. The storage unit 30 stores various programs and data for control / arithmetic processing of the control unit 26. The storage unit 30 is composed of, for example, an EEPROM. The display 32 displays the calculation result in the control unit 26 and the like.
[0019]
As shown in FIG. 1, when measuring the subject 10, the subject 10 is first placed on the bed 16, and then the X-ray generator 18 and the X-ray detector 22 are moved in the horizontal direction by the scanning device 24. For example, high-energy X-rays and low-energy X-rays are irradiated alternately at a predetermined cycle of, for example, several milliseconds. By detecting this with the X-ray detection device 22, the count rate (Ih) of the high energy X-ray transmitted through the subject 10 and the count rate (Il) of the low energy X-ray transmitted through the subject 10 for each point in the horizontal plane. Each is required. The amount of attenuation at each point is represented by the natural logarithm of the measured count rates Ih and Il divided by the reference count rates Ioh and Iol, respectively. That is, the attenuation amount Rh of the high energy X-ray is obtained by ln (Ioh / Ih), and the attenuation amount R1 of the low energy X-ray is obtained by ln (Iol / Il). The reference count rates Ioh and Iol are obtained when high energy X-rays and low energy X-rays are irradiated from the X-ray generator 18 to the position where there is no subject on the bed 16 under the same conditions as when the subject is actually measured. The count rate obtained from the detection result of the X-ray detector 22 can be used. The attenuation amounts of the high energy X-rays and the low energy X-rays thus obtained become raw data of measurement by this apparatus. Hereinafter, the bone density and body fat percentage of each point are calculated based on this raw data.
[0020]
Here, the calculation of the bone density may be performed in accordance with the well-known DXA method algorithm, so the description thereof will be omitted, and the calculation method of the body fat percentage will be described with reference to FIG.
[0021]
For the calculation of body fat percentage, calibration is performed using a phantom that simulates soft tissue with respect to X-ray transmission, and an attenuation ratio-body fat percentage function indicating the relationship between the attenuation ratio and the body fat percentage is obtained. . For this calibration, phantoms corresponding to two different body fat percentages are used. For example, two types of phantoms (referred to as phantom Fat0) corresponding to a body fat percentage of 0% (that is, muscle 100%) and phantoms (referred to as phantom Fat100) corresponding to a body fat percentage of 100% (muscle 0%) are used. . Then, a phantom Fat0 with a body fat percentage of 0% is placed on the bed 16 and irradiated with high energy X-rays and low energy X-rays, the respective attenuation amounts Rh and Rl are calculated, and the ratio Rl / Rh between them is calculated. To do. This ratio is called an attenuation ratio. The attenuation ratio obtained for the phantom Fat0 is shown as RR0 in FIG. FIG. 2 shows the relationship between the body fat percentage on the vertical axis and the attenuation ratio on the horizontal axis, and the point corresponding to the body fat percentage of 0% is indicated by A. Similarly, the phantom Fat100 is measured to determine the attenuation ratio RR100 corresponding to the body fat percentage of 100%. The point corresponding to this is shown as point B in FIG. The range excluding two points of body fat percentage 0% and 100% is approximated by a function using these two points as parameters. This function is called a conversion function f. The example of FIG. 2 is an example in the case of approximating between these two points with a linear conversion function f. Of course, a more appropriate conversion function may be found and used by experiments or the like. In any case, the calibration process may be performed using the number of phantoms having different body fat percentages necessary for specifying the conversion function to be used.
[0022]
The conversion function f obtained in this way is stored in the storage unit 30 and used. In calculating the body fat percentage, the subject 100 is actually measured to obtain the attenuation ratio RRx, and this RRx is substituted into the conversion function f to obtain the body fat percentage value F. The conversion function may be stored as a set of parameters that define the function form as described above, but may be implemented in the form of a table or the like in which values of body fat percentage corresponding to each attenuation ratio are registered. Of course.
[0023]
Next, with reference to FIG. 3, a procedure of processing performed by the apparatus according to the present invention will be described.
[0024]
First, the X-ray generation device 18 and the X-ray detection device 22 are scanned as described above to obtain attenuation amounts Rh and Rl of high energy X-rays and low energy X-rays at each point of the subject 100 (S10). Based on the measurement results, maps representing the two-dimensional distributions of Rh and Rl are created (S12). This map has a value of attenuation (Rh or Rl) for each pixel of the image. A set of these maps becomes the raw data of the measurement results. Thereafter, the bone density measurement process and the body fat percentage measurement process are executed based on the set of maps.
[0025]
In both the bone density measurement and the body fat percentage measurement, the attenuation ratio RR = Rl / Rh is calculated for each pixel from the raw attenuation data (S14 and S20). However, the calculation of the attenuation amount ratio does not simply take the ratio between the attenuation amounts of the high and low energy in the raw data, but in the case of bone density measurement (S14) and body fat percentage measurement (S20), respectively. Appropriate correction calculation is added. This correction calculation is for correcting a shift in measurement results (bone density or body fat percentage) due to a difference in body thickness (also called body thickness correction). Here, the body thickness is the length that the X-rays pass through the subject. Ideally, even if the body thickness is different, when the same bone density (or body fat percentage) is measured, The same attenuation ratio RR should be obtained (that is, the relationship between the two is a linear proportional relationship), but in reality this is not the case and the relationship between the two becomes non-linear. Therefore, the Rh and Rl raw data are corrected so as to be as close to ideal as possible, and the ratio between the two is taken. However, in the case of the bone density measuring apparatus of the DXA method, the body thickness of each part of the subject cannot be measured due to the structure of the apparatus (a dedicated measuring mechanism may be provided for measuring the body thickness, but in terms of cost. Therefore, a configuration is adopted in which the attenuation amount of the raw data is simply converted into the attenuation amount corrected for the body thickness. That is, the attenuations Rh and Rl change monotonously although they are not proportionally related to the body thickness, so that it can be assumed that the raw attenuation value itself has a one-to-one correspondence with the body thickness. Such a conversion method is possible. For this conversion, prepare multiple phantoms of the same material and different thicknesses, measure them with high and low energy X-rays, and make the attenuation ratio Rl / Rh as uniform as possible regardless of the body thickness. Then, a correction value of Rh or Rl is obtained.
[0026]
This body thickness correction is also performed in the conventional DXA method bone density measuring device. However, in the conventional device, a good body thickness correction can be performed by correcting the attenuation amount Rh for high energy X-rays. It has been realized. However, this is a good body thickness correction for the bone density measurement, and according to the experiment of the present inventor, a good result was not obtained even when the same correction was applied to the body fat percentage measurement. Therefore, when a body thickness correction method suitable for the body fat percentage was examined by experiment, it was found that it was preferable to correct the attenuation amount Rl for low energy X-rays. Although the exact theoretical clarification has not yet been made on this point, the rough mechanism is considered as follows. That is, since the attenuation of X-rays by bone is much larger than that by soft tissue, high-energy X-rays are sufficiently attenuated in the bone part (that is, the part where bone is included in the X-ray transmission path). The amount of attenuation of high energy X-rays is dominant in bone density. For this reason, it is thought that favorable body thickness correction | amendment is attained by correct | amending the attenuation amount of a high energy X-ray. On the other hand, since soft tissue has a small attenuation of X-rays, a difference in attenuation due to a difference in body thickness is small in a soft tissue portion (that is, a portion where bone is not included in an X-ray transmission path). Of these, high energy X-rays are more permeable, so differences due to differences in body thickness are less likely to appear than low energy X-rays. In addition, the difference in attenuation amount of X-rays is small between fat and muscle of soft tissue, and the change in attenuation amount is extremely small even when the body fat percentage is changed in high energy X-rays having a large transmission power. On the other hand, the amount of attenuation of low energy X-rays having a smaller transmission power reflects the difference in attenuation between fat and muscle more than that of high energy X-rays. Therefore, in body fat percentage calculation for soft tissue parts, it is considered that a suitable body thickness correction can be achieved by correcting the attenuation amount of low-energy X-rays that is more sensitive to the ratio of fat to muscle. .
[0027]
In order to obtain a specific conversion function (or conversion table) for correcting body thickness, first, a plurality of phantoms having different thicknesses are prepared for bone density and body fat percentage, as described above. Measurement is performed with X-rays of each energy, and attenuation amounts Rl and Rh corresponding to each body thickness are obtained. In the measurement result, the correction value Rh ′ of the attenuation Rh corresponding to each thickness of the high-energy X-ray is used for the bone density measurement so that the attenuation ratio Rl / Rh is as uniform as possible regardless of the thickness of the phantom. For the measurement of body fat percentage, correction values R1 ′ of attenuation R1 corresponding to the thicknesses of the low energy X-rays are obtained. For bone density measurement, a function that approximates the correspondence between Rh and Rh 'for each thickness is determined as a conversion function. For body fat percentage measurement, a function that approximates the correspondence between Rl and Rl' for each thickness. Is determined as a conversion function. The body thickness correction conversion function determined in this way is stored in advance in the storage unit 30.
[0028]
Accordingly, in S14, body thickness correction is performed on the Rh of each pixel of the raw data by a conversion function for bone density, and in S22, body thickness correction is performed on the Rl of each pixel of the raw data by a conversion function for body fat percentage. After that, the attenuation ratio Rl / Rh is calculated for each pixel using the correction result.
[0029]
After the attenuation ratio map having been corrected for the bone portion is created in S14, each pixel of this map is then converted into the bone portion (the portion including the bone in the X-ray transmission path) according to the attenuation ratio value of the pixel. ), Soft tissue (portion not including bone in the X-ray transmission path but including soft tissue), and air layer (portion where the X-ray transmission path is only the air layer). Since the attenuation ratio Rl / Rh differs greatly between the bone part, the soft tissue, and the air layer, these three types can be distinguished by threshold discrimination. As the discrimination threshold at this time, the values of the attenuation ratio that separates the bone portion and the soft tissue and the attenuation ratio that separates the soft tissue and the air layer may be obtained in advance by experiments or the like. According to this discrimination, each pixel is necessarily classified into one of bone, soft tissue, and air layer.
[0030]
By this S16, a classification map indicating which pixel corresponds to the bone part and which pixel corresponds to the soft tissue in the attenuation map obtained in S12 and the attenuation ratio map obtained in S14 and S22 is obtained. It is done.
[0031]
In S18, only the pixels of the bone part are extracted with reference to the classification map, and the value of the pixel in the attenuation ratio map obtained in S14 is extracted for each pixel of the bone part, and based on this value. The bone density of the pixel is calculated according to a well-known DXA method.
[0032]
In this way, when the bone density of each pixel of the bone portion is obtained, the bone density distribution is obtained by converting the bone density of each pixel into a gradation value of a predetermined first color for each pixel. The image is formed (S20). A conversion function (or table) indicating the relationship between the bone density and the gradation value is registered in the storage unit 30 in advance.
[0033]
Thus, an image of the bone density distribution is completed. On the other hand, in the body fat percentage measurement process, after the process of S22, each pixel of the soft tissue is extracted with reference to the classification map determined in S16, and the attenuation amount determined in S22 for each pixel of the soft tissue. The value of the pixel in the ratio map is taken out, and based on this value, the body fat percentage of the pixel is calculated according to the above-described body fat percentage calculation method (S24).
[0034]
When the body fat percentage of each pixel of the soft tissue is obtained in this way, the body fat percentage of that pixel is then determined for each pixel by a predetermined first color different from the first color assigned to the bone density display. An image of the body fat percentage distribution is formed by converting the tone value of the color 2 (S26). Here, a conversion function (or table) indicating the relationship between the body fat percentage and the gradation value is registered in the storage unit 30 in advance.
[0035]
In S28, the bone density distribution image generated in S20 and the body fat percentage distribution image generated in S26 are combined to generate one output image. In this synthesis, the classification table created in S16 is referred to, the value of the corresponding pixel in the bone density distribution is adopted for the pixel corresponding to the bone part, and the corresponding pixel in the body fat percentage distribution is adopted for the pixel corresponding to the soft tissue. Adopt value.
[0036]
The first color assigned to the bone density and the second color assigned to the body fat percentage may be selected from primary colors of the display output mechanism, for example. For example, in the case of an RGB display device, G (green) is selected as the first color, and R (red) is selected as the second color. In addition, a method is also conceivable in which the bone density is expressed by a black and white gray scale whose correspondence with the bone is intuitively easy to understand, and the body fat percentage is expressed by a gradation of a chromatic color (for example, red). Of course, these are examples, and any combination of colors can be used for the first color and the second color as long as the difference between the two can be distinguished even if the gradation is changed. Can do.
[0037]
Then, the composite image generated in this way is displayed and output on, for example, the display 32 or printed out from a printer (not shown) (S30).
[0038]
FIG. 4 schematically shows an example of a composite image of the bone density distribution and the body fat percentage distribution output from the apparatus of the present embodiment. Since the color cannot be expressed in the figure, the first color is indicated by hatching, the second color is indicated by cross hatching, and the bone density and the body fat percentage are expressed by hatching density. As shown in this figure, in the vicinity of the composite image 200 of the bone density distribution and the body fat percentage distribution, a scale 210a representing the correspondence between the gradation of each color and the value (or magnitude) of the bone density or body fat percentage. , 210b. In this figure, the number of gradations is reduced in order to avoid complexity, but the gradation can be further reduced in an actual output image.
[0039]
As described above, according to the apparatus of the present embodiment, the composite image 200 showing the bone density in the portion corresponding to the bone portion of the subject and the body fat percentage in the portion corresponding to the soft tissue is created. Can be output. Since the user can list the distribution of the bone density and the distribution of the body fat percentage by using the synthesized image 200, it becomes easy to grasp the relationship between the body fat percentage and the bone density. Further, in the present embodiment, since the calculation method and the body thickness correction method suitable for the body fat percentage are used, unlike the soft tissue display described in the prior art, highly reliable body fat percentage information is provided. be able to.
[0040]
In the present embodiment, since the bone density and the body fat percentage are expressed by gradations of the first color and the second color different from each other, each pixel on the composite image 200 has a bone density (bone part). Or body fat percentage (soft tissue).
[0041]
Note that the image expression method in which the bone density and the body fat percentage are expressed by gradations of the first color and the second color different from each other is merely an example. In principle, a display form range that does not overlap each other may be assigned to the bone density and the body fat percentage. The display form range includes a gradation range of one color as in the above-described example. In this case, for example, the “first color” is one display form range, and a color having a certain gradation within the first color range is one display form within the display form range. A range on a hue circle such as a cold color or a warm color is also a kind of display form range. That is, for example, a hue gradation in the cold color range is assigned to the bone density, and a hue gradation in the warm color range is assigned to the body fat percentage. 4 is also a kind of display form range, and in this case, each type of hatching (downward slanted hatching or cross hatching) corresponds to one display form range. A hatching of a certain density in the hatching type corresponds to one display form within the display form range. In any case, the display form ranges respectively assigned to the bone density and the body fat percentage are easily distinguished from each other on the composite image 200 regardless of the values of the bone density and the body fat percentage from the upper limit to the lower limit. It is desirable to be.
[0042]
In the embodiment shown in FIG. 1, the X-ray generation device 18 and the X-ray detection device 22 are driven in the horizontal direction. As is apparent from the above description, the bone density distribution and the body fat percentage distribution in the present embodiment. The simultaneous display does not depend on the configuration of such a detection system. For example, the X-ray generator 18 and the X-ray detector 22 may be fixedly arranged and the bed 16 may be driven in the horizontal direction. In this case, the bed 16 is driven by the scanning device 24, whereby the subject 10 itself is scanned. As a detection system, a pencil beam focused on one point may be output from the X-ray generator 18 and detected by the X-ray detector 22 comprising one detector. A fan beam extending in a fan shape from 18 may be output, and this may be detected by the X-ray detection device 22 having an array in which a plurality of detectors are arranged in a line. Moreover, the structure using the cone beam which spreads conically from X-ray generator 18 may be sufficient. In the above example, high-energy X-rays and low-energy X-rays are alternately irradiated at short intervals. Instead, broadband X-rays are irradiated, and the X-ray detection device 22 detects the wave height of the detection signal. A configuration may be used in which discrimination is performed and the detection signal corresponding to the high energy X-ray and the detection signal corresponding to the low energy X-ray are discriminated and individually counted.
[0043]
【The invention's effect】
As described above, according to the present invention, the bone density distribution of the subject bone part and the body fat percentage distribution of the subject soft tissue can be combined and displayed in one image, so that the user This makes it easier to understand the relationship between body fat percentage and bone density.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of an X-ray bone density measuring apparatus according to an embodiment.
FIG. 2 is a diagram for explaining the principle of measuring body fat percentage according to the embodiment.
FIG. 3 is a diagram for explaining a processing flow of the apparatus according to the embodiment;
FIG. 4 is a diagram schematically illustrating an example of an output image of the apparatus according to the embodiment.
FIG. 5 is a diagram for explaining the principle of bone density measurement by the DXA method.
[Explanation of symbols]
10 subjects, 12 bones, 14 soft tissues, 16 beds, 18 X-ray generators, 22 X-ray detectors, 24 scanning devices, 26 control units, 30 storage units, 32 displays.

Claims (4)

Measuring means for detecting X-rays transmitted through the subject and obtaining a two-dimensional distribution of X-ray attenuation based on the detection results;
Discriminating means for discriminating the bone and soft tissue of the subject from the two-dimensional distribution;
Bone density calculating means for obtaining a bone density distribution of the bone part from the two-dimensional distribution;
A body fat percentage calculating means for obtaining a body fat percentage distribution of the soft tissue from the two-dimensional distribution;
Synthesis means for synthesizing and outputting the bone density distribution of the bone part and the body fat percentage distribution of the soft tissue in one image;
An X-ray bone density measuring apparatus including: The measurement means obtains a two-dimensional distribution of the attenuation for each of two different energy X-rays,
The bone density calculating means obtains a bone density distribution according to a double X-ray absorption measurement method from the two-dimensional distribution of the X-rays of each energy,
The body fat percentage distribution calculating means has information on the correspondence between the ratio of the attenuation amount of X-rays of each energy and the body fat percentage, and the attenuation of the X-rays of each energy at each point from the two-dimensional distribution. Obtain the body fat percentage distribution by obtaining the ratio between the amounts, and obtaining the body fat percentage corresponding to the ratio from the information of the correspondence relationship,
The X-ray bone density measuring apparatus according to claim 1. The synthesizing unit assigns different display form ranges to the bone density distribution and the body fat percentage distribution, and expresses the bone density and the body fat percentage in display forms within the corresponding display form ranges, respectively. The X-ray bone density measuring apparatus according to claim 1 or 2. The body fat percentage distribution calculating means determines the ratio of the X-ray attenuation of each energy at each point from the two-dimensional distribution. The X-ray bone density measuring apparatus according to any one of claims 1 to 3, wherein a value of an attenuation amount of the two-dimensional distribution with respect to a line is corrected.

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