JP2983421B2 - Bone measurement method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bone measuring method and a bone measuring device. More specifically, the present invention relates to an inter-facility difference in a device for measuring bone morphology and the like using an image of a test bone on an X-ray film, or an influence of a temporal change occurring after a certain period of time in the same facility. Is provided.

[0002]

2. Description of the Related Art As an application example of image reading on an X-ray photographic film, the density of a shadow image on the film is measured by a microdensitometer using an X-ray photographic film obtained by irradiating a test bone with X-rays. MD method for bone measurement by using a method ("Bone Metabolism" Vol. 13, pp. 187-195 (1980)
Year), Vol. 14, pages 91-104 (1981), etc.). Note that the MD method is easy to adopt in that it uses an X-ray photographic film that can be easily obtained using an X-ray image photographing device that is widely used as a device for diagnosing a fracture, etc. I have.

[0003] In the past, bone measurement by the MD method had a lot of manual operations as follows. In other words, X
Using a radiographic film obtained by irradiating the X-ray, the reference point required for bone measurement by the MD method is first determined manually for the image of the bone on the film, and further determined using the reference point. In this manner, a site where bone measurement is to be performed in detail (for example, a site on a transverse line at the midpoint of the long axis of the second metacarpal) is selected. Then, while scanning the microdensitometer for the selected site,
The intensity of transmitted light obtained by irradiating the portion with light is measured, and a diagram of the intensity or absorbance of the transmitted light corresponding to the scanned portion is written on a predetermined chart paper. Further, the microdensitometer was scanned on the vertical line of the image on the film of the aluminum stepped standard material (hereinafter referred to as the aluminum step) which was radiographed together with the test bone, and the intensity or absorbance of the obtained transmitted light was measured. The diagram is also described on the chart paper. The thus obtained diagrams of the absorbance of the test bone and the absorbance of the aluminum step on the chart paper are input to a computer using a digitizer, and the absorbance of the test bone is converted into the number of steps of the aluminum step at each point. Various indices representing the bone morphology at the target site are calculated in the computer using the diagram obtained by the conversion in this way, and the calculation results are output.

Japanese Patent Application Laid-Open No. Hei 3-215256 discloses an image reading apparatus for such an MD method or the like. Here, for example, an LED (Light Emittin) is used as a light generating means for irradiating an X-ray photographic film.
g Diode) and a CCD (Cha) for reading the amount of light transmitted through the X-ray film.
An image sensor such as RGed Coupled Device) is used. The transmitted light amount is converted into an analog electric signal by the sensor, and further converted into a digital signal by AD conversion. The transmitted light amount signal from the bone to be examined is converted into an MPU (Mic) using a transmitted light amount signal of a standard material read in advance.
(Ro Processing Unit) to convert to a standard material thickness, and calculate the bone mineral content after pattern processing.

[0005] However, bone measurement by the conventional bone measurement method involving X-ray imaging is caused by fluctuations in X-ray imaging conditions, X-ray intensity unevenness, and film development processing conditions when an X-ray photographic film is used. However, there is a problem that the measurement results are different. Due to this difference, even when the same subject is measured, a difference may occur in the measurement result between the facilities or when the measurement is performed after a certain time or more in the same facility.

[0006]

SUMMARY OF THE INVENTION The present invention is intended to reduce differences between facilities due to differences in conditions and performance of processing apparatuses such as an X-ray imaging apparatus and a developing apparatus, or differences in measurement results within a facility after a certain period of time or more. The purpose is to reduce and reduce the accuracy of comparison and examination of measurement results within a facility or between facilities.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, have previously derived a correction equation using one or two or more types of reference phantoms. The present inventors have found that it is possible to reduce the difference between the facilities or the difference within the facility after a certain period of time or more by converting the measurement result of each facility again based on the correction formula, and arrived at the present invention.

That is, according to the present invention, a photoelectric signal based on an image of a subject bone radiographed with a reference material having a varying thickness is converted into a photoelectric signal based on the thickness of the reference material using computer means. In a bone measurement method in which the characteristic is converted by an inverse function or an approximate function thereof to measure the bone to be examined, a reference phantom is radiographed together with the reference material in place of the bone to be examined, and a predetermined bone measurement method is used. Based on the measurement results at the time of measurement, the correction formula for reducing the difference between facilities or correcting the aging change in the facility is obtained in advance,
Another object of the present invention is to provide a bone measurement method characterized in that the correction formula is used when measuring a test bone. The radiation here
Includes γ-rays and X-rays.
Line. Examples of the standard substance include an aluminum slope and a step.

In the bone measurement method of the present invention, (1) when one type of the reference phantom is used, and when the correction formula includes an offset correction term, (2) the reference phantom has a different measurement result. When two or more types are used and the correction equation is composed of offset correction terms, further (3) the reference phantom uses two or more types of different measurement results, and the correction equation is based on the gain / offset correction term. Is included.

Further, regarding the above (2) and (3), 2
A bone measurement method in which more than one kind of reference phantoms are taken in close contact with a single radiographic film or the like together with the reference material, and two or more kinds of reference phantoms are separately and There is a bone measurement method in which images are taken at the same position.

In the method of the present invention, the difference between the facilities is determined by using a correction formula including a gain / offset correction term obtained by using two or more types of reference phantoms having different measurement results. The change over time includes a bone measurement method using a correction formula including a correction term of an offset obtained using one type of reference phantom.

Further, the present invention provides a means for obtaining a photoelectric signal based on an image of a subject bone radiographed together with a reference material having a varying thickness, and a characteristic of the photoelectric signal based on the thickness of the reference material. In a bone measuring apparatus provided with a processing means for performing characteristic measurement by an inverse function or an approximate function thereof and measuring the bone to be examined, the processing means emits a reference phantom instead of the bone to be examined together with the reference material. A correction formula for reducing inter-facility differences or compensating for temporal changes in facilities, which is obtained in advance based on the measurement results obtained by imaging and measuring by a predetermined bone measurement method, shall be used. And a bone measuring device characterized by the following.

The facility in the present invention refers to a facility where X-ray photography is performed, and usually means a hospital or the like.

[0014]

Therefore, according to the present invention, by taking the above-described means, it is possible to more accurately observe the temporal change of the bone measurement result of the same subject in the facility.
In addition, it is possible to more accurately compare bone measurement results between subjects within a facility or between facilities.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will now be described with reference to FIGS.
This will be described with reference to FIG.

When the bone measurement method of the present invention uses an image on an X-ray film, the X-ray film for bone measurement is generally taken by the method shown in FIG.

At this time, X generated by the X-ray imaging device
The wavelength of the line differs depending on the set tube voltage (FIG. 2).
Therefore, the mass attenuation coefficient μ representing the ease of transmission of X-rays when transmitting the test object also changes (FIG. 3). Actually, when an image is taken with an X-ray imaging apparatus, the tube voltage fluctuates within a certain range (see the example of the tube voltage waveform in FIG. 4), and as a result, the type of the apparatus and the use environment of the day change. The way the tube voltage fluctuates depends on the situation. FIG. 5 shows the difference in the measurement result due to the difference in the tube voltage. From this, it can be understood that the difference between the X-ray imaging apparatuses is one of the causes of the difference between facilities or the day-to-day difference in the same facility.

Further, when developing the photographed X-ray photographic film, an automatic developing machine is generally used (FIG. 6). However, in an automatic developing machine, development unevenness occurs in the longitudinal direction of an internal X-ray photographic film feeding roller regardless of the performance of the apparatus (FIG. 7). Considering the attenuation of X-rays due to the distance from the X-ray source in addition to this, it can be seen that there is very large unevenness on the X-ray photographic film. This error is also the difference between facilities,
Or, it can be seen that it is one of the causes of the day difference in the same facility.

Due to the above factors, even if the same subject, such as the second metacarpal, is measured after imaging, the measurement results of the bone measurement obtained differ between the facilities as shown in FIG. is there. For each of the data, when calculating the areas ΔGS and ΔGS / D of the hatched portions in the absorbance pattern at the midpoint of the second metacarpal bone on the radiographic film in FIG. 9, the measurement results are as shown in FIG. A very good correlation is seen with the size of Therefore, it was considered that the difference between facilities can be reduced by correcting ΔGS.

Hereinafter, a method of ΔGS correction, which is an example of correction using a correction formula in the bone measurement method of the present invention, will be described in detail.

The reference phantom according to the present invention has a structure as shown in FIG. 11, and includes a pseudo soft tissue 8 and a pseudo bone 9. The pseudo soft tissue 8 and the pseudo bone 9 are made of pure aluminum (A1080), but may be other substances such as hydroxyapatite. FIG. 12 shows the measurement results at several facilities of three types of reference phantoms in which only the inner diameter of the simulated bone 9 is changed. From this figure, a and a represent the coefficients indicating the degree of increase in the measurement results of three types of reference phantoms having different inner diameters.
Assuming that the offset coefficient at each facility is b, it can be approximated as Y = aX + b. Here, Y is the design value of ΔGS of the measurement result, and X is the design value of ΔGS of each reference phantom. At all facilities,
Since the coefficient a indicating the degree of increase in the measurement result is almost the same (see Table 1), the difference between facilities can be corrected with a certain degree of accuracy by adjusting only the offset coefficient b.

Table 1 shows the ΔGS of each reference phantom on the horizontal axis.
The vertical axis indicates the gain and the offset when the ΔGS / D measurement value of each reference phantom is taken on the vertical axis.

[0023]

[Table 1]

Hereinafter, an example of a method of correcting between facilities by adjusting only the offset coefficient b will be described in detail.

The photographing of the X-ray film required for the bone measuring method is performed as shown in FIG. In FIG. 1, 1 is X
A radiographic device 4 is a dedicated cassette sandwiching an X-ray photographic film and an intensifying screen, and 3 is a reference phantom. The photographed X-ray photographic film is developed by an automatic developing machine or a similar device or manually. FIG. 11 shows an example of the reference phantom shape. The same reference phantom is measured after photographing in another facility by the same method. FIG. 8 shows the distribution of the ΔGS measurement result of the reference phantom among a plurality of facilities.

From the measurement results obtained at each facility, an offset coefficient unique to each facility is determined by the following equation.

[0027]

(Equation 1)

Here, Σ (k = 1 to n) in the above equation is the sum of the reference phantoms in all facilities. Also, D
_meas is the measured value of the external dimensions of the reference phantom at each facility. ΣGS / D _meas is a measured value of the bone measurement result of the reference phantom in each facility. D _dsgn is a design value of the external dimensions of the reference phantom, and ΔGS / D
_meas is a design value of the bone measurement result of the reference phantom.
As a result, the bone measurement result corrected between facilities is calculated by the following equation. Here, ΔGS / D _mdfd is the corrected bone measurement result.

[0029]

(Equation 2)

As a result, even if the same reference phantom is measured by the bone measuring device after the photographing, the distribution between the facilities as shown in FIG. 8 is changed to a distribution with almost no difference between the facilities as shown in FIG. Can be corrected.

As described above, it has been found that the difference between the facilities can be reduced as shown in Table 2 even when the correction only for the offset is performed. Gain coefficient a representing the degree of increase
It is necessary to make adjustments between facilities by adjusting the amount.

Table 2 shows the effect when offset correction is performed in the apparatus of the present invention.

[0033]

[Table 2]

Hereinafter, an example of a method of correcting between facilities by adjusting the gain coefficient a and the offset coefficient b will be described in detail.

The photographing of the X-ray film required for the bone measuring method of the present invention is performed as shown in FIG. In FIG. 1, reference numeral 1 denotes an X-ray imaging apparatus, 4 denotes a dedicated cassette sandwiching an X-ray photographic film and an intensifying screen, and 3 denotes a reference phantom. The photographed X-ray photographic film is developed by an automatic developing machine or a similar device or manually. Although two or more types of reference phantoms may be used, three types are used here. FIG. 11 shows the shape of the reference phantom. Table 3 shows examples of the shape and dimensions of each reference phantom. Three types of reference phantoms are measured at other facilities after photographing in the same manner. FIG. 12 shows the distribution of the measurement results of each reference phantom between facilities.

Table 3 shows the inner and outer diameters of the three types of reference phantoms in the device of the present invention.

[0037]

[Table 3]

At each facility,

[0039]

(Equation 3)

The following equation is obtained by writing a graph (FIG. 14) and performing a temporary regression.

[0041]

(Equation 4)

Here, △ _revolved is △ estimated by linear regression, a is a gain coefficient, and b is an offset coefficient. Using this equation, the bone measurement result ΣGS / D _meas can be corrected to a value with a small difference between facilities. The correction equation is represented by the following equation.

[0043]

(Equation 5)

Here, ΔGS / D _mdfd is the corrected bone measurement result. As a result, even if three types of reference phantoms are measured by the bone measuring device after imaging, the distribution between facilities as shown in FIG. 12 is corrected to a distribution with almost no difference between facilities as shown in FIG. be able to. In addition, the effects as shown in Table 4 are observed even in terms of differences between facilities.

Table 4 shows the effect when the gain / offset correction is performed in the apparatus of the present invention.

[0046]

[Table 4]

Examples of the test subjects applicable to the bone measuring method of the present invention include a human bone growth state, a degree of aging, or a range of bone lesions such as osteoporosis and osteomalacia or symptoms thereof. The bone to be examined is required when performing various bone measurements such as confirmation of the degree of progress of the treatment and the effect of the treatment. X
The bone to be examined in the case of using a radiographic film is not particularly limited as long as an X-ray photographic film having a certain degree of clear shading can be obtained. desirable. Specific examples include a long bone made of cortical bone such as a hand bone, a humerus, a radius, an ulna, a femur, a tibia, and a fibula. Further, other specific examples of the test bone applicable to the apparatus of the present invention include cancellous bone such as the calcaneus, the spine, and the end of the long bone. Further, any other test object may be used as long as it needs to be converted into the thickness of a standard substance and evaluated through an X-ray photographic film.

The bone measuring apparatus according to the present invention is characterized in that it has a configuration for implementing such a bone measuring method.
FIG. 16 schematically shows a preferred embodiment of the bone measuring device of the present invention. In this figure, a means for generating light (light source) for irradiating the X-ray photographic film with the automatic reading function unit 10 and a detecting means for detecting the intensity of light transmitted from the light source through the X-ray photographic film And a film automatic running means for automatically running the X-ray photographic film.

Such a light source may be a light source that generates a spot light, but usually requires scanning means. In order to provide a device having a small and simple structure, a band light for generating a band light is required. Light sources are practically preferred.
As the detecting means, any means can be used as long as it can detect transmitted light and can be automatically read. However, when a band light source is used, a band sensor, that is, a line sensor is preferably used, and in particular, a band-shaped contact image sensor is practically used. Above. Rollers are usually used as a means for running the film. Among them, a pair of rollers that rotate in opposite directions with the film interposed therebetween is preferably used, but other types of rollers may be used. The automatic running means of the film may be any means capable of running the X-ray photographic film at a predetermined speed at a speed suitable for the speed detected by the detecting means. It may be present or intermittent.

It is preferable that the bone measuring device of the present invention includes image storage means. As such image storage means,
A data group in which a digital signal relating to the intensity of transmitted light in an image on the X-ray film of the test bone obtained by the automatic reading means as described above corresponds to the position of the film, or an image converted to the thickness of a standard material Any storage device can be used as long as it can store a data group related to the data, and the storage memory size is selected according to the purpose of bone measurement. A specific example is 2 in the bone measurement of the second metacarpal bone.
Computer means such as an image memory of about M bytes can be used.

Further, the apparatus of the present invention is provided with arithmetic means for performing various processes for performing bone measurement using the image read from the film.

Further, as shown in FIG. 16, the apparatus of the present invention has a CRT (Cathode Ray Tub) for displaying an image of the subject bone read by the image reading means or stored by the storage means as an image.
e) an image display means, a point input means for inputting reference points necessary for bone measurement in the displayed image of the test bone, and a test bone stored using the input reference points. An apparatus having an operation unit for performing an operation for bone measurement on an image is included.

As the image display means, any means can be used as long as it can display, as an image, a data group having a positional relationship with a digital signal stored in the image storage means or obtained by the automatic reading means. More specifically, a CRT or the like can be given as a preferable example from the cost of resolution.

For example, as a point input means for inputting a reference point when an intermediate point of the second metacarpal is determined by a CRT image, a position can be specified and input as a reference point on the image display means. Any type can be used as long as it is possible.Specific examples include cursor position display, instruction control means, light pen type input means, a method of externally inputting with a touch panel, and a stored image of the bone to be inspected. , An automatic input method, and the like.

In the apparatus of the present invention, for example, before adjusting the light amount of the light source, the position of the reference point input by the point input means in the image display means is stored by a storage means such as a RAM as shown in FIG. Then, the same portion of the film is read again using the adjusted light amount after the light amount is adjusted based on the determination result as described above, and the point input is performed based on the reference point already stored in the RAM in the image displayed on the display means. That includes means for performing such operations. These series of operations are performed by the image reading function unit 10 operated by the control of the MPU in FIG. With this configuration, the irradiation light amount is reset and if it is different from the previous setting value, the film is automatically fed to the aluminum stairs and the target part, and if the point input of the reading target part is necessary, the previous point input value is Since the information is stored and automatically processed at that position, the burden on the operator for re-input can be reduced.

As the bone measurement output means in the bone measurement apparatus of the present invention, any means can be used as long as it can output the measurement results obtained by the calculation. Examples include an ink printer, a thermal printer, a laser printer, a video printer, and other CRT screens.

In the reading function unit 10 shown in FIG. 16, for example, a line sensor (CCD: Charged Coupled) having a pitch of 65 μm × 4096 elements
Device) are arranged at right angles to the film movement direction, and X
Strip light source (LED:
The film is irradiated by Light Emitting Diode, and the transmitted light is condensed by a rod lens arranged so as to focus on a line sensor on the film reflection surface, and the intensity of the transmitted light corresponding to the density of the X-ray film is obtained. And a microfilm running means using a pulse motor capable of micromoving at a pitch of 65 μm in a direction perpendicular to the line sensor and the belt-shaped light source at the same time as obtaining a signal such as this. Each element of the line sensor outputs an analog voltage proportional to the amount of light incident on the line sensor (= the amount of light transmitted according to the density of the film).

The control means for detecting the transmitted light by squeezing a specific portion of the X-ray photographic film or controlling the intermittent running of the film at a predetermined speed is shown in FIG. It is illustrated as a controller.

The CCD driver shown in FIG. 16 has a function of controlling data stored in the CCD to be extracted at a predetermined timing.

In the bone measurement data processing function unit in FIG. 16, a data group read by the reading function unit 10 is stored by an image storage unit mainly including an image input / output unit and an image memory in the data processing unit 11. The data group relating to the stored image is C
Displayed by RTC and CRT.

An image of the metacarpal bone is displayed on a 7-inch CRT (640 dots × 400 lines) having an image display means and a point input means, and a cursor is moved to specify a measurement site to designate a head and an epiphysis. I do. Such point input means is shown as a KBI / F and a keyboard in FIG.

The calculation for bone measurement is performed by using R in FIG.
OM (program storage unit for operation) and RAM
(A part for performing the operation and storing the result).

The bone measurement results obtained are shown in FIG.
It is output by an output unit mainly composed of an RI / F and a printer. RS-232C and MODEM
F, for connecting with other devices.

The MPU in FIG. 16 controls, in addition to the above-described functions, fetching data into an image memory, starting / stopping a program, and controlling a keyboard / CRT.
It is a 6-bit microprocessor, and the PIO functions as an interface for inputting / outputting digital control input / output to / from the computer system.

With respect to the use of the correction formula which is a feature of the apparatus of the present invention, for example, a bone measurement is performed by changing a phantom in a facility in advance to obtain the correction formula as described above, and the coefficients of the correction formula are calculated as shown in FIG. And store it in the ROM. At the time of actual measurement of the bone to be inspected, the bone measurement processing is performed by using a correction formula using those coefficients in the ROM.

In the above-described embodiment, an X-ray photographic film is used. However, the present invention can be easily applied to an apparatus for directly irradiating an X-ray image sensor with X-rays to form an image. FIG. 17 schematically shows the flow from X-ray imaging to bone measurement in the case of such an apparatus.

In an apparatus for directly irradiating an X-ray onto an X-ray image sensor to form an image, an imaging plate 12 is used instead of a cassette sandwiching an X-ray film in a conventional X-ray imaging method. Then, the laser light irradiation means 13 and the light detection sensor 14 irradiate the X-ray information stored and recorded on the imaging plate 12 with laser light, whereby information proportional to the X-ray intensity can be read as an optical signal. A / D conversion is performed on the read photoelectric information to obtain an X-ray image 15 of the subject bone. The X
Bone measurement equivalent to the bone measurement method of the present invention can be performed together with the line image.

[0068]

As described above, according to the present invention, after deriving a correction formula for a difference between facilities using a reference phantom, the same test object is measured when the same test object is measured in order to convert the measurement result again using the correction formula. The difference and the difference between the measurement results in the facility after a certain period of time can be reduced. As a result, it is possible to accurately compare the measurement results between facilities and the temporal change of a certain subject in the facilities.

[Brief description of the drawings]

FIG. 1 illustrates an example of radiographing of a radiographic film for bone measurement.

FIG. 2 shows the relationship between tube voltage and X-ray wavelength in an X-ray imaging apparatus.

FIG. 3 illustrates an example of a change in a mass attenuation coefficient according to a tube voltage change.

FIG. 4 illustrates an example of a fluctuation of a tube voltage when a radiograph is taken by an X-ray apparatus (single phase).

FIG. 5 illustrates an example of a correlation between a set tube voltage and a bone measurement result at the time of radiographic film photography.

FIG. 6 shows an example of an automatic developing machine.

FIG. 7 illustrates an example of development unevenness by an automatic developing machine (in a film feeding direction).

FIG. 8 illustrates an example of a distribution of bone measurement results between facilities.

FIG. 9 illustrates an example of bone measurement in the apparatus of the present invention.

FIG. 10 illustrates an example of a correlation between ΔGS / D and ΔGS in a bone measurement result.

FIG. 11 shows an example of a reference phantom shape in the apparatus of the present invention.

FIG. 12 illustrates an example of a distribution between facilities of three types of reference phantom bone measurement results in the apparatus of the present invention.

FIG. 13 is a diagram illustrating an example of a distribution between facilities of a bone measurement result after offset correction in the apparatus of the present invention.

FIG. 14 shows the Σ of each reference phantom in the device of the present invention.
Relationship between GS design value and △

FIG. 15 illustrates an example of a distribution between facilities of bone measurement results after gain / offset correction in the apparatus of the present invention.

FIG. 16 schematically illustrates the apparatus of the present invention as a block diagram.

FIG. 17 is a diagram schematically showing a flow from X-ray imaging to bone measurement in a bone measurement device using an X-ray image sensor.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 X-ray imaging device 2 Standard material of varying thickness 3 Reference phantom 4 Dedicated cassette sandwiching X-ray photographic film and intensifying screen 5 GSmax1 in bone pattern 6 GSmax2 in bone pattern 7 GSmin8 in bone pattern Soft tissue 9 pseudo bone 10 automatic reading function unit 11 data processing unit 12 imaging plate 13 laser light irradiation means 14 light detection sensor 15 X-ray image of bone to be examined

Claims (4)

(57) [Claims] 1. An optical signal based on an image of a test bone obtained by radiography with a reference material having a varying thickness is converted into a photoelectric signal based on the thickness of the reference material using computer means. In a bone measurement method of measuring the test bone by converting the characteristic to an inverse function or an approximate function thereof,
In place of the bone to be examined, two or more reference phantoms having different measurement results are separately radiographed together with the reference material at the same position, and radiographs are taken together with the reference material. A bone measurement method characterized in that a correction formula including an offset correction term for reducing a difference and / or correcting a temporal change in a facility is obtained in advance, and the correction formula is used when measuring a bone to be inspected. 2. Radiation with a reference material of varying thickness.
Image-based photogrammetry of the subject bone obtained by radiography
The reference material thickness using computer means.
The characteristics of the photoelectric signal can be specified by the inverse function or its approximate function.
In the bone measurement method of measuring the test bone by sex conversion,
Release the reference phantom with the reference material instead of the test bone
When taking radiographs and measuring by the prescribed bone measurement method
Based on the measurement result, reduce the difference between facilities and / or within the facility
A correction formula for correcting the change with time is obtained in advance,
This correction formula is used when measuring the bone to be examined, and the
Uses two or more reference phantoms with different measurement results.
Compensation consisting of gain-offset correction terms obtained using
The formal use, the change over time in the facility is one kind of reference phantom
Correction formula consisting of offset correction terms obtained using
A bone measurement method, characterized by using: 3. A means for obtaining a photoelectric signal based on an image of a subject bone radiographed with a reference material having a varying thickness, and an inverse function or a characteristic of the photoelectric signal based on the thickness of the reference material. In a bone measurement device having processing means for performing characteristic conversion with the approximation function and measuring the test bone,
The processing means replaces the bone to be inspected with two types having different measurement results.
Reduction of previously obtained center differences based on the measurement results when the kind or more reference phantom and radiographic with the standards in separately and the same position was determined by a predetermined bone measuring method and / or site A bone measurement apparatus characterized in that a correction formula including an offset correction term for correcting a change with time is used. 4. Radiation with a reference material of varying thickness.
Obtain a photoelectric signal based on a radiographic image of the test bone
Means and reverse the characteristics of the photoelectric signal based on the thickness of the reference material.
Measurement of the subject bone by converting characteristics with a function or its approximate function
A bone measuring device provided with a processing means for performing
The processing means includes a reference phantom in place of the bone to be examined.
Radiography with reference material
Determined in advance based on the measurement results when measuring
Reduce differences between facilities and / or compensate for changes over time in facilities.
The difference between facilities is measured.
Using two or more reference phantoms with different results
Correction equation consisting of the gain / offset correction terms
The time-dependent change in the facility uses one kind of reference phantom.
Correction formula consisting of offset correction terms obtained by
A bone measuring device characterized by being a means.