CN105388170B - The measuring method and device of a kind of bone density - Google Patents

Abstract

The invention discloses the measuring method and device of a kind of bone density, correlation technique includes：It obtains the radioscopic image of sample and removes the Background X-ray image after sample, be denoted as sample image and background image respectively；The refraction information of sample is calculated with absorbing information according to the sample image got and background image；The bone density of sample is calculated with the parameter after absorption information and progress X ray Hardening correction according to the refraction information of the sample.Absorption image and refraction image can be obtained simultaneously by using method disclosed by the invention, dual intensity image not overlap problem is not present in measurement process so that bone density measurement speed and precision are improved.

Description

Method and device for measuring bone density

technical field

The invention relates to the technical field of density measurement, in particular to a method and device for measuring bone density.

Background technique

In the actual measurement of bone density, bone density is often described by the value of bone mass per unit area in a certain projection direction, and the unit is g/cm ² .

Bone density measurement methods have undergone decades of development. At present, there are X-ray film measurement method, single-photon absorptiometry method, two-photon absorptiometry method, dual-energy X-ray absorptiometry method, quantitative CT method, ultrasonic measurement method, etc. Wait.

However, the technical difficulty of the existing solution is how to simultaneously acquire the absorption images of the measured part under different X-ray energy states at the same moment. At present, there are mainly two mechanisms for generating dual-energy X-rays in medical equipment: one is the rare earth filter type, which uses rare earth filters containing rare earth elements samarium (Sm) or cerium (Ce) to filter X-rays, and the The continuous X-ray spectrum is divided into two nearly independent X-ray spectra, and the X-ray absorption images of the two energies are obtained simultaneously using a detector with an energy discriminator accordingly; the other is a pulse conversion type, which uses different pulses Control the X-ray tube voltage to generate X-rays with different energies and obtain absorption images. The above two methods have problems such as poor specificity of X-ray energy spectrum, complicated instrument hardware and data acquisition process, etc. The second method requires that the measured person cannot move during the measurement process, otherwise two kinds of energy will be generated. If the measured images do not overlap, the system cannot accurately calculate the bone density value of the measured part.

Contents of the invention

The object of the present invention is to provide a method and device for measuring bone density, which can accurately calculate the bone density.

The purpose of the present invention is achieved through the following technical solutions:

A method for measuring bone density, comprising:

Obtain the X-ray image of the tested sample and the background X-ray image after removing the tested sample, which are respectively recorded as the sample image and the background image;

Calculate the refraction information and absorption information of the measured sample according to the acquired sample image and background image;

The bone density of the tested sample is calculated according to the refraction information and absorption information of the tested sample, and parameters after X-ray hardening correction.

The X-ray image of the acquired sample under test and the background X-ray image after removing the sample under test are recorded as sample image and background image respectively, including:

Put the sample to be tested into the sample stage and adjust it to the predetermined range of the field of view, irradiate the sample to be tested with X-rays emitted by the X-ray tube, and move the X-ray detector installed on the X-ray detector along the direction perpendicular to the grating lines The analysis grating in front moves W steps evenly within one grating period, takes multiple images at each step to obtain the average, and corrects the image, and records the obtained image as the sample image, and records the sample image finally obtained at the kth step for

Wherein, the image correction includes:

Before acquiring the sample image and the background image, remove the optical elements between the X-ray tube and the X-ray detector out of the optical path, turn on the detector to collect D images, calculate the average and output an image, save it as a dark field correction image, and record I _offset ; after collecting D images, calculate the average output image, save it as a gain correction image, and record it as I _gain ;

Correct the image according to the following correction formula;

In the formula, (m,n) is the image pixel coordinates of the correction point, I(m,n) is the corrected image, I ₀ (m,n) is the original image, M is the number of row pixels of the detector, N is The number of columns of pixels for the detector.

The calculation of the refraction information and absorption information of the measured sample according to the obtained sample image and background image includes:

The formula for calculating the refraction information of the sample is:

In the formula, α is the refraction angle, and the coordinates (m, n) represent the position coordinates of the pixels on the X-ray detector; T represents the total number of steps of the phase step; _P2 represents the period of the analysis grating _G2 ; d is the phase grating The distance between _G1 and the analysis grating _G2 , the phase grating _G1 is arranged between the sample stage and the X-ray tube and is close to the sample stage;

The formula for calculating the absorption information of the sample is:

In the formula, A(m,n) represents the absorption image.

The method also includes:

For the tested sample, use X-rays to penetrate the same thickness of aluminum and plexiglass, and measure the actual absorption data and refraction data to perform X-ray hardening correction; the aluminum is used to simulate bone tissue, and the plexiglass is used to simulate soft tissue .

The calculation of the bone density of the tested sample according to the refraction information and absorption information of the tested sample and parameters after X-ray hardening correction includes:

Bone density was calculated using the following formula:

In the formula, M _B (m, n) represents the bone density at coordinates (m, n); α (m, n), A (m, n) are the refraction information and absorption information of the sample, respectively;

Both _{U S} and Q _S are the parameters after X-ray _hardening correction by using plexiglass to simulate soft tissue. Ratio, Q _S = (δ/ρ) _S represents the ratio of the refractive index correction value and density of organic glass;

Both U _B and Q _B are the parameters corrected by X-ray hardening by using aluminum to simulate bone tissue. The subscript B represents bone tissue, where U _B = (μ/ρ) _B represents the relationship between the corrected value of the linear absorption coefficient of aluminum and the density The ratio, Q _B =(δ/ρ) _B represents the ratio of the corrected value of the refractive index of aluminum to the density.

A device for measuring bone density, comprising:

The image acquisition unit is used to acquire the X-ray image of the sample to be tested, and the background X-ray image after the sample is removed, which are respectively recorded as the sample image and the background image;

An information calculation unit, configured to calculate the refraction information and absorption information of the measured sample according to the acquired sample image and background image;

The bone density calculation unit is used to calculate the bone density of the measured sample according to the refraction information and absorption information of the measured sample, and parameters after X-ray hardening correction.

The image acquisition unit is used to obtain the X-ray image of the sample under test, and the background X-ray image after the sample under test is removed, respectively recorded as the sample image and the background image, including:

Put the sample to be tested into the sample stage and adjust it to the predetermined range of the field of view, irradiate the sample to be tested with X-rays emitted by the X-ray tube, and move the X-ray detector installed on the X-ray detector along the direction perpendicular to the grating lines The analysis grating in front moves W steps evenly within one grating period, takes multiple images at each step to obtain the average, and corrects the image, and records the obtained image as the sample image, and records the sample image finally obtained at the kth step for

Wherein, the image correction includes:

Before acquiring the sample image and the background image, remove the optical elements between the X-ray tube and the X-ray detector out of the optical path, turn on the detector to collect D images, calculate the average and output an image, save it as a dark field correction image, and record I _offset ; after collecting D images, calculate the average output image, save it as a gain correction image, and record it as I _gain ;

Correct the image according to the following correction formula;

In the formula, (m,n) is the image pixel coordinates of the correction point, I(m,n) is the corrected image, I ₀ (m,n) is the original image, M is the number of row pixels of the detector, N is The number of columns of pixels for the detector.

The information calculation unit is used to calculate the refraction information and absorption information of the measured sample according to the obtained sample image and background image, including:

The formula for calculating the refraction information of the sample is:

In the formula, α is the refraction angle, and the coordinates (m, n) represent the position coordinates of the pixels on the X-ray detector; T represents the total number of steps of the phase step; _P2 represents the period of the analysis grating _G2 ; d is the phase grating The distance between _G1 and the analysis grating _G2 , the phase grating _G1 is arranged between the sample stage and the X-ray tube and is close to the sample stage;

The formula for calculating the absorption information of the sample is:

In the formula, A(m,n) represents the absorption image.

The unit also includes:

The correction unit is used to perform X-ray hardening correction by measuring the actual absorption data and refraction data by using X-rays to penetrate aluminum and plexiglass of the same thickness for the tested sample; the aluminum in it is used to simulate bone tissue, organic Glass is used to simulate soft tissue.

The bone density calculation unit is used to calculate the bone density of the measured sample according to the refraction information and absorption information of the measured sample, and the parameters after X-ray hardening correction, including:

Bone density was calculated using the following formula:

In the formula, M _B (m, n) represents the bone density at coordinates (m, n); α (m, n), A (m, n) are the refraction information and absorption information of the sample, respectively;

Both _{U S} and Q _S are the parameters after X-ray _hardening correction by using plexiglass to simulate soft tissue. Ratio, Q _S = (δ/ρ) _S represents the ratio of the refractive index correction value and density of organic glass;

Both U _B and Q _B are the parameters corrected by X-ray hardening by using aluminum to simulate bone tissue. The subscript B represents bone tissue, where U _B = (μ/ρ) _B represents the relationship between the corrected value of the linear absorption coefficient of aluminum and the density The ratio, Q _B =(δ/ρ) _B represents the ratio of the corrected value of the refractive index of aluminum to the density.

It can be seen from the technical solution provided by the present invention that only one X-ray energy value is used, that is, the influence of soft tissue is removed, thereby achieving the purpose of accurately calculating bone density. Moreover, since the energy adjustment device and the corresponding detector are no longer needed, the measurement device and the measurement process of bone density can be greatly simplified; in addition, since the absorption image and the refraction image can be obtained at the same time, there is no dual-energy image in the measurement process No overlap problem, bone density measurement speed and accuracy can be improved. At the same time, due to the introduction of refraction information, since the refraction coefficient of soft tissue to X-rays in the energy range is more than one thousand times stronger than the absorption coefficient, this provides a potential for applying this scheme to the accurate measurement of soft tissue and body composition and reducing radiation dose. possible.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For Those of ordinary skill in the art can also obtain other drawings based on these drawings on the premise of not paying creative efforts.

Fig. 1 is a flow chart of a method for measuring bone density provided by an embodiment of the present invention;

2 is a schematic diagram of a bone density measuring device provided by an embodiment of the present invention;

Figure 3a is a simulation diagram of the absorption image after the X-rays penetrate the sample on the selected cross-section provided by the embodiment of the present invention;

Fig. 3b is a simulated diagram of the refraction angle image after the X-ray penetrates the sample on the selected section provided by the embodiment of the present invention;

Fig. 3c is the integral image of the refraction angle distribution function α(x) provided by the embodiment of the present invention;

Figure 3d is a schematic diagram of the comparison between the soft tissue density simulation results and theoretical results provided by the embodiment of the present invention;

Figure 3e is a schematic diagram of the comparison between the bone tissue density simulation results and theoretical results provided by the embodiment of the present invention;

Fig. 4 is the schematic diagram of the measuring instrument provided by the embodiment of the present invention;

Fig. 5 is a schematic diagram of an experimental sample provided by an embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Fig. 1 is a flowchart of a method for measuring bone density provided by an embodiment of the present invention. As shown in Figure 1, it mainly includes the following steps:

1. Detector correction

Detector correction includes: dark field correction and gain correction. The specific correction process is;

Move the optical components between the X-ray tube and the X-ray detector out of the optical path, turn on the detector to collect D images, calculate an average output image, save it as a dark field correction image, and record it as I _offset ; collect D images again After obtaining an average output image, save it as a gain correction image, which is recorded as I _gain ;

In the subsequent image acquisition process, the image is corrected according to the following correction formula;

In the formula, (m,n) is the image pixel coordinates of the correction point, I(m,n) is the corrected image, I ₀ (m,n) is the original image, M is the number of row pixels of the detector, N is The number of columns of pixels for the detector.

2. Instrument optical path calibration

Move the optical components back to the optical path, turn on the X-ray tube and X-ray detector, fine-tune the beam splitting grating, and observe the moiré fringes on the detector. When the fringes are uniform and the periodic area is infinite, the optical path calibration is considered complete.

3. Acquire the sample image and background image

1) Acquisition and acquisition of sample images

Put the sample to be tested into the sample stage and adjust it to the predetermined range of the field of view, irradiate the sample to be tested with X-rays emitted by the X-ray tube, and move the X-ray detector installed on the X-ray detector along the direction perpendicular to the grating lines The analysis grating in front moves W steps evenly within one grating period, takes multiple images at each step to obtain the average, and corrects the image, and records the obtained image as the sample image, and records the sample image finally obtained at the kth step for

2) Acquire the background image

In the embodiment of the present invention, the above W may be set to 5.

4. Calculate the refraction information and absorption information of the measured sample.

This step is calculated based on the sample image and background image obtained in the previous step 2, refraction information and absorption information; the details are as follows:

1) The formula for calculating the refraction information of the sample is:

In the formula, α is the refraction angle, and the coordinates (m, n) represent the position coordinates of the pixels on the X-ray detector; T represents the total number of steps of the phase step; _P2 represents the period of the analysis grating _G2 ; d is the phase grating The distance between _G1 and the analysis grating _G2 , the phase grating _G1 is arranged between the sample stage and the X-ray tube and is close to the sample stage;

2) The formula for calculating the absorption information of the sample is:

In the formula, A(m,n) represents the absorption image.

5. X-ray hardening correction

X-ray hardening refers to the fact that after the continuous X-ray spectrum penetrates the object, the ray energy moves to the direction of high energy, that is, the X-ray "hardens". The cathode-emitting X-ray tube light source is used in the experimental instrument, and the X-ray spectrum generated includes the characteristic radiation spectrum and the bremsstrahlung spectrum. The bremsstrahlung spectrum is the X-ray spectrum continuously distributed in a certain energy range. Since the refraction ability and absorption ability of an object to X-rays are related to the energy of X-rays, and the refraction coefficient and absorption coefficient of the experimental sample are important parameters used in the calculation, it is necessary to know the equivalent energy of X-rays after penetrating the sample. Quantities to accurately determine the refractive index and absorption coefficient of the sample, which is corrected for X-ray hardening.

There are various correction methods for X-ray hardening. When the existing dual-energy X-ray absorptiometry instrument measures bone density, it often uses a calibrator model for calibration. The calibrator model is mostly composed of stepped aluminum alloy and stepped acrylic plastic to simulate different composition ratios of bone tissue and soft tissue, and then use different energies to pass through the calibrator to generate a calibration curve.

In the embodiment of the present invention, X-ray hardening correction is carried out by measuring the actual absorption data and refraction data by using X-rays to penetrate aluminum and plexiglass of the same thickness for the tested sample; the aluminum in it is used to simulate bone tissue , plexiglass is used to simulate soft tissue.

6. Calculation of bone density

In the embodiment of the present invention, the bone density of the tested sample is calculated according to the refraction information and absorption information of the tested sample, and parameters after X-ray hardening correction.

The absorption formula of X-rays after penetrating the human body is:

I＝I ₀ exp[-(μ/ρ) _S M _S -(μ/ρ) _B M _B ]

The refraction formula is:

Φ＝l(δ/ρ) _S M _S +l(δ/ρ) _B M _B

Among them, Φ represents the phase shift after the X-ray penetrates the object, the subscript S represents soft tissue, B represents bone tissue, l is the wave vector, δ is the refractive index of the material, ρ is the material density, and M is the surface density.

Simultaneous absorption and refraction formula, the value of bone density M _B can be calculated, if write

U _S ＝(μ/ρ) _S , U _B ＝(μ/ρ) _B , Q _S ＝(δ/ρ) _S , Q _B ＝(δ/ρ) _B

In the above formula, U _S and Q _S are the parameters after X-ray hardening correction by using organic glass to simulate soft tissue, the subscript S represents soft tissue, and U _S = (μ/ρ) _S represents the linear absorption coefficient correction of organic glass The ratio of the value to the density, Q _S = (δ/ρ) _S represents the ratio of the corrected value of the refractive index of the plexiglass to the density; U _B and Q _B are the parameters after X-ray hardening correction by using aluminum simulated bone tissue, the following Subscript B represents bone tissue, where U _B = (μ/ρ) _B represents the ratio of the corrected value of the linear absorption coefficient of aluminum to the density, Q _B = (δ/ρ) _B represents the ratio of the corrected value of the refractive index of aluminum to the density ;

then there is

Combined with the refraction and absorption information calculated in the previous step 4, the final calculation equation becomes

Based on this, the bone density and soft tissue density of the tested sample can be measured.

Compared with the existing bone density measurement method, the bone density measurement method provided by the embodiment of the present invention realizes the use of only one X-ray energy value, that is, removes the influence of soft tissue, thereby achieving the purpose of accurately calculating bone density. Moreover, since the energy adjustment device and the corresponding detector are no longer needed, the measurement device and the measurement process of bone density can be greatly simplified; in addition, since the absorption image and the refraction image can be obtained at the same time, there is no dual-energy image in the measurement process No overlap problem, bone density measurement speed and accuracy can be improved. At the same time, due to the introduction of refraction information, since the refraction coefficient of soft tissue to X-rays in the energy range is more than a thousand times stronger than the absorption coefficient, this provides a potential for applying this scheme to accurate measurement of soft tissues and reducing radiation dose.

Through the above description of the implementation manners, those skilled in the art can clearly understand that the above embodiments can be implemented by software, or by means of software plus a necessary general hardware platform. Based on this understanding, the technical solutions of the above-mentioned embodiments can be embodied in the form of software products, which can be stored in a non-volatile storage medium (which can be CD-ROM, U disk, mobile hard disk, etc.), including Several instructions are used to make a computer device (which may be a personal computer, a server, or a network device, etc.) execute the methods described in various embodiments of the present invention.

The embodiment of the present invention also provides a bone density measuring device, which can be used to implement the aforementioned method, as shown in Figure 2, the device mainly includes:

The image acquisition unit is used to acquire the X-ray image of the sample to be tested, and the background X-ray image after the sample is removed, which are respectively recorded as the sample image and the background image;

An information calculation unit, configured to calculate the refraction information and absorption information of the measured sample according to the acquired sample image and background image;

The bone density calculation unit is used to calculate the bone density of the measured sample according to the refraction information and absorption information of the measured sample, and parameters after X-ray hardening correction.

Further, the image acquisition unit is used to acquire the X-ray image of the sample under test, and the background X-ray image after the sample under test is removed, respectively recorded as sample image and background image, including:

Put the sample to be tested into the sample stage and adjust it to the predetermined range of the field of view, irradiate the sample to be tested with X-rays emitted by the X-ray tube, and move the X-ray detector installed on the X-ray detector along the direction perpendicular to the grating lines The analysis grating in front moves W steps evenly within one grating period, takes multiple images at each step to obtain the average, and corrects the image, and records the obtained image as the sample image, and records the sample image finally obtained at the kth step for

Wherein, the image correction includes:

Before acquiring the sample image and the background image, remove the optical elements between the X-ray tube and the X-ray detector out of the optical path, turn on the detector to collect D images, calculate the average and output an image, save it as a dark field correction image, and record I _offset ; after collecting D images, calculate the average output image, save it as a gain correction image, and record it as I _gain ;

Correct the image according to the following correction formula;

In the formula, (m,n) is the image pixel coordinates of the correction point, I(m,n) is the corrected image, I ₀ (m,n) is the original image, M is the number of row pixels of the detector, N is The number of columns of pixels for the detector.

Further, the information calculation unit is used to calculate the refraction information and absorption information of the measured sample according to the acquired sample image and background image, including:

The formula for calculating the refraction information of the sample is:

In the formula, α is the refraction angle, and the coordinates (m, n) represent the position coordinates of the pixels on the X-ray detector; T represents the total number of steps of the phase step; _P2 represents the period of the analysis grating _G2 ; d is the phase grating The distance between _G1 and the analysis grating _G2 , the phase grating _G1 is arranged between the sample stage and the X-ray tube and is close to the sample stage;

The formula for calculating the absorption information of the sample is:

In the formula, A(m,n) represents the absorption image.

Further, the device also includes:

The correction unit is used to perform X-ray hardening correction by measuring the actual absorption data and refraction data by using X-rays to penetrate aluminum and plexiglass of the same thickness for the tested sample; the aluminum in it is used to simulate bone tissue, organic Glass is used to simulate soft tissue.

Further, the bone density calculation unit is used to calculate the bone density of the tested sample according to the refraction information and absorption information of the tested sample, and parameters after X-ray hardening correction includes:

Bone density was calculated using the following formula:

In the formula, M _B (m, n) represents the bone density at coordinates (m, n); α (m, n), A (m, n) are the refraction information and absorption information of the sample, respectively;

Both _{U S} and Q _S are the parameters after X-ray _hardening correction by using plexiglass to simulate soft tissue. Ratio, Q _S = (δ/ρ) _S represents the ratio of the refractive index correction value and density of organic glass;

Both U _B and Q _B are the parameters corrected by X-ray hardening by using aluminum to simulate bone tissue. The subscript B represents bone tissue, where U _B = (μ/ρ) _B represents the relationship between the corrected value of the linear absorption coefficient of aluminum and the density The ratio, Q _B =(δ/ρ) _B represents the ratio of the corrected value of the refractive index of aluminum to the density.

It should be noted that the specific implementation manners of the functions implemented by the various functional modules included in the above apparatus have been described in detail in the previous embodiments, so details will not be repeated here.

Those skilled in the art can clearly understand that for the convenience and brevity of description, only the division of the above-mentioned functional modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional modules according to needs. The internal structure of the device is divided into different functional modules to complete all or part of the functions described above.

On the other hand, in order to facilitate the understanding of the present invention, further description will be made below in conjunction with specific examples. It should be noted that the specific numerical values provided in the following examples are only examples. In actual work, users can Make settings.

Example 1,

In this example, the complete process of calculating the area density of the experimental sample model is firstly simulated by means of computer numerical simulation. The conditions of the numerical simulation are set as follows: the diameter of the PMMA (organic glass) outer cavity (used to simulate soft tissue) is 2 cm, the diameter of the Al (aluminum) inner core (used to simulate bone tissue) is 1.5 cm, and the X-ray equivalent photon The energy is 30KeV. The data required for calculation can be found from the official website of the National Institute of Standards and Technology (NIST), as shown in Table 1.

Table 1. Parameters and corresponding values required for simulation calculation

The calculation process is as follows:

The first step is to obtain the absorption information after X-rays penetrate the sample, as shown in Figure 3(a), which is the absorption image after X-rays penetrate the sample on the selected cross-section, that is, the value of ln(I/I ₀ ) varies with Distribution function of the radial position of the section. Taking the center point of the section as an example, where the abscissa is 0, t _PMMA = 1cm, t _Al = 4cm, then ln(I/I ₀ )=-μ _PMMA t _PMMA -μ _AL t _AL , that is, the ordinate can be obtained is -11.1464.

The second step is to obtain the refraction information after the X-ray penetrates the object, as shown in Figure 3(b), which is the refraction angle image of the X-ray penetrating the sample on the selected section, that is, α(x) varies with the radial direction of the section Distribution function of location. Taking the center point of the section as an example, where the abscissa x=0, we have That is to say, the vertical coordinate is also 0. Figure 3(c) is the integral image of the refraction angle distribution function α(x), taking the center point of the section as an example, where the abscissa is 0 and the ordinate is The obtained result is 2.69337E-6.

The third step is the calculation of the surface density. Since the calculation results of the absorption information ln(I/I ₀ ) and the refraction information ∫α(x)dx are already available, the data listed in Table 1 are directly brought into the surface of the present invention. Density calculation formula:

The calculation results are shown by the solid lines in Fig. 3(d) and Fig. 3(e), marked as M _Simulation . In addition, since we have accurately understood the geometric parameters and density of the calculation model used, the actual surface density M = ρt distribution of the sample can be accurately calculated, and the settlement results are drawn in Fig. 3(d) and Fig. 3(e) as dotted lines, Tagged M _Theory . Since the numerical simulation does not need to consider the hardening effect of X-rays, it can be seen that the simulation results are almost identical to the theoretical results, which again demonstrates the correctness of the bone density measurement method provided by the present invention.

Example two,

This example mainly introduces the above-mentioned bone density measuring instrument. In this example, the schematic diagram of the measuring instrument is shown in Figure 4, mainly including: 1-X-ray optical machine, 2-source grating, 3-phase grating, 4-sample stage, 5-analysis grating, 6-detector and other components, which are distributed along the optical axis. The three gratings are all fixed on the 9-optical platform through the 8-optical precision displacement stage, and the 7-piezoelectric ceramic precision displacement motor is installed between the analysis grating and the optical precision displacement stage to complete the stepping motion of the analysis grating . The measurement device provided by the foregoing embodiments of the present invention is implemented by the PC shown in FIG. 4 , that is, the PC is used to implement the aforementioned functions.

Optical-mechanical parameter setting: focus 1.0mm, 60KV/7mA, exposure time 499ms. Three grating parameters: source grating period 120 μm, duty ratio 1:1; beam splitting grating period 60 μm, duty ratio 1:2; analysis grating period 120 μm, duty ratio 1:2. The detector pixel size is 200 μm, 1024×1024 pixels. The source grating is close to the optomechanical beryllium window (about 0.5cm), the distance from the beam splitting grating is 51 cm, the distance between the beam splitting grating and the analysis grating is 51 cm, the sample stage is 10 cm behind the beam splitting grating, and the analysis grating is close to the detector (actual distance from the scintillator About 10cm, with a protective glass plate on the front). The experimental sample is shown in Figure 5, consisting of 1-cylindrical cavity and 2-cylindrical core. The material of the cylindrical cavity 1 is plexiglass, the outer diameter of the section is 20 mm, and the inner diameter is 15 mm. The material of the cylindrical inner core 2 is aluminum, the cross-sectional diameter is 15 mm, and the length of the sample is 40 mm.

Step 1: Detector Correction

All optical components between the X-ray tube and the detector in the optical path are removed from the optical path, the X-ray tube is turned off, the detector is initialized, and image acquisition is performed. After collecting 50 images, calculate the average and output an image, save it as a dark field correction image, and record it as I _offset .

Turn on the X-ray tube, set the tube voltage to 60KV, collect 50 images and calculate the average to output an image, save it as a gain correction image, and record it as I _gain .

When the instrument is working normally, the following formula is executed on the obtained original image I ₀

I(m,n) is the final experimental image, and this process can complete the detector correction.

Step 2: Image Acquisition

After the sample image acquisition is completed, control the motor of the sample stage, move the sample out of the field of view, and move the analysis grating back to the original position. Follow the same operation process to obtain the background image, which is recorded as

Step 3: Information Extraction

Obtain the sample absorption image according to the following formula

Then obtain the refraction image according to the following formula

Step Four: X-Ray Hardening Correction

Take out the inner core of the sample and place it on the sample stage separately. The tube voltage of the X-ray tube is still set to 60KV. After collecting 50 images of the sample, calculate the average value and output a saved image, which is recorded as I _harden , and then move the sample out of the optical path , and other settings remain unchanged, 50 images are collected to calculate the average value, and then output a saved image, which is recorded as I ₀ . We select the center position of the cylinder for calculation. According to Lambert-Beer's law I=I ₀ e ^-μt , since the thickness t of the cylinder core at this place is 1.5cm, take I _harden =I ₀ e ^-μt to calculate the actual The linear absorption coefficient, that is, the corrected is 1.249cm ^-1 . And because of Where A is the sample absorption data calculated in step 3, combined with the existing correction value of the linear absorption coefficient of aluminum And we know that the thickness of the plexiglass at this place is t _PMMA = 0.5cm, that is, the correction value of the linear absorption coefficient of the plexiglass can be obtained is 0.281cm ^-1 .

After calculating the corrected values of the linear absorption coefficients of aluminum and plexiglass, you can find the corresponding equivalent energy through the NIST official website, which we record as and and look up the corresponding refractive index correction value and The corrected calculation results and search results are listed in Table 2.

Table 2 X-ray hardening corrected parameter values

Step 5: Calculate the surface density of the sample

For the selected calculation region (ROI), we have obtained the absorption information A(m,n) and refraction information α(m,n) at the place by step 3, and we can calculate the corrected U _S , U _B , Q _S and Q _B . then there is

U _S ＝(μ/ρ) _S ＝0.281/1.19＝0.2361(cm ² /g),

U _B ＝(μ/ρ) _B ＝1.249/2.72＝0.4592,

Q _S ＝(δ/ρ) _S ＝1.7197/1.19＝1.445126×10 ^-7 (cm ³ /g),

Q _B = (δ/ρ) _B = 2.7534/2.72 = 1.01227941×10 ^-7 (cm ³ /g)

Then bring the data into the surface density calculation formula

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person familiar with the technical field can easily conceive of changes or changes within the technical scope disclosed in the present invention. Replacement should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (8)

1. a kind of measuring method of bone density, which is characterized in that including：

It obtains the radioscopic image of sample and removes the Background X-ray image after sample, be denoted as sample drawing respectively Picture and background image；

The refraction information of sample is calculated with absorbing information according to the sample image got and background image；

Quilt is calculated according to the refraction information of the sample and the parameter after absorption information and progress X ray Hardening correction The bone density of sample：

In formula, M_BBone density at (m, n) denotation coordination (m, n)；α (m, n), A (m, n) are respectively the refraction information of sample with inhaling It collects mail and ceases；

U_SWith Q_SIt is the parameter carried out using organic glass simulation soft tissue after X ray Hardening correction, subscript S represents soft tissue, U therein_S=(μ/ρ)_SRepresent the linear absorption coefficient correction value of organic glass and the ratio of density, Q_S=(δ/ρ)_SIt indicates The refraction coefficient correction value of machine glass and the ratio of density；

U_BWith Q_BIt is to intend the parameter after bone tissue carries out X ray Hardening correction using aluminum dipping form, subscript B represents bone tissue, therein U_B=(μ/ρ)_BRepresent the linear absorption coefficient correction value of aluminium and the ratio of density, Q_B=(δ/ρ)_BRepresent that the refraction coefficient of aluminium is repaiied The ratio of positive value and density.

2. according to the method described in claim 1, it is characterized in that, the radioscopic image for obtaining sample and removal Background X-ray image after sample is denoted as sample image and includes with background image respectively：

Sample is put into sample stage and is adjusted to visual field preset range, utilizes the x-ray bombardment that X-ray tube projects to quilt Sample, and along the analysis grating being arranged in front of X-ray detector is moved perpendicular to grating line direction, in one light W steps are uniformly moved in grid cycle, often step takes multiple images to ask for average, and image is corrected, and the image of acquisition is denoted as Sample image, the sample image that note kth step finally obtains are

Sample is removed into sample stage, and analysis grating is moved back to original position, then according to the similary step of acquisition sample image Background image is acquired, and image is corrected, the image of acquisition is denoted as background image, the background that note kth step finally obtains Image is

Wherein, it is described to image carry out correction include：

Before sample image and background image is obtained, the optical element between X-ray tube and X-ray detector is removed into light X-ray tube is closed on road, is asked for one image of average output after opening D images of detector acquisition, is saved as details in a play not acted out on stage, but told through dialogues correction figure Picture is denoted as I_offset；X-ray tube is opened again, is asked for one image of average output after D images of acquisition, is saved as gain correction figure Picture is denoted as I_gain；

Image is corrected according to following correction formula；

In formula, (m, n) be correction point image pixel coordinates, I (m, n) be correct after image, I₀(m, n) be original image, M For the row pixel number of detector, N is the row pixel number of detector.

3. according to the method described in claim 2, it is characterized in that, sample image and background image meter that the basis is got The refraction information for calculating sample includes with absorbing information：

The refraction information calculation formula of sample is：

In formula, α is refraction angle, and coordinate (m, n) represents the position coordinates of pixel on X-ray detector；T represents phase stepping Total step number；P₂Represent analysis grating G₂Period；D is phase grating G₁With analysis grating G₂The distance between, the phase grating G₁It is arranged between sample stage and X-ray tube and close to the sample stage；

The absorption information calculation formula of sample is：

In formula, A (m, n) represents absorption image.

4. according to the method described in claim 1, it is characterized in that, this method further includes：

For sample, the aluminium and organic glass of same thickness are penetrated using X ray, by measure practical absorption data and Refraction data carries out X ray Hardening correction；Aluminium therein is used for simulating bone tissue, and organic glass is used for simulating soft tissue.

5. a kind of measuring device of bone density, which is characterized in that including：

Image acquisition unit, for obtaining the Background X-ray figure after the radioscopic image of sample and removal sample Picture is denoted as sample image and background image respectively；

Information calculating unit, for calculating the refraction information of sample with inhaling according to the sample image got and background image It collects mail and ceases；

Bone density computing unit, for the refraction information according to the sample with absorbing information and carrying out X ray hardening Revised parameter calculates the bone density of sample：

In formula, M_BBone density at (m, n) denotation coordination (m, n)；α (m, n), A (m, n) are respectively the refraction information of sample with inhaling It collects mail and ceases；

U_SWith Q_SIt is the parameter carried out using organic glass simulation soft tissue after X ray Hardening correction, subscript S represents soft tissue, U therein_S=(μ/ρ)_SRepresent the linear absorption coefficient correction value of organic glass and the ratio of density, Q_S=(δ/ρ)_SIt indicates The refraction coefficient correction value of machine glass and the ratio of density；

U_BWith Q_BIt is to intend the parameter after bone tissue carries out X ray Hardening correction using aluminum dipping form, subscript B represents bone tissue, therein U_B=(μ/ρ)_BRepresent the linear absorption coefficient correction value of aluminium and the ratio of density, Q_B=(δ/ρ)_BRepresent that the refraction coefficient of aluminium is repaiied The ratio of positive value and density.

6. device according to claim 5, which is characterized in that described image acquiring unit, for obtaining the X of sample Background X-ray image after ray image and removal sample, is denoted as sample image and includes with background image respectively：

Sample is put into sample stage and is adjusted to visual field preset range, utilizes the x-ray bombardment that X-ray tube projects to quilt Sample, and along the analysis grating being arranged in front of X-ray detector is moved perpendicular to grating line direction, in one light W steps are uniformly moved in grid cycle, often step takes multiple images to ask for average, and image is corrected, and the image of acquisition is denoted as Sample image, the sample image that note kth step finally obtains are

Sample is removed into sample stage, and analysis grating is moved back to original position, then according to the similary step of acquisition sample image Background image is acquired, and image is corrected, the image of acquisition is denoted as background image, the background that note kth step finally obtains Image is

Wherein, it is described to image carry out correction include：

Before sample image and background image is obtained, the optical element between X-ray tube and X-ray detector is removed into light X-ray tube is closed on road, is asked for one image of average output after opening D images of detector acquisition, is saved as details in a play not acted out on stage, but told through dialogues correction figure Picture is denoted as I_offset；X-ray tube is opened again, is asked for one image of average output after D images of acquisition, is saved as gain correction figure Picture is denoted as I_gain；

Image is corrected according to following correction formula；

In formula, (m, n) be correction point image pixel coordinates, I (m, n) be correct after image, I₀(m, n) be original image, M For the row pixel number of detector, N is the row pixel number of detector.

7. device according to claim 6, which is characterized in that information calculating unit, for according to the sample drawing got As the refraction information that sample is calculated with background image includes with absorbing information：

The refraction information calculation formula of sample is：

In formula, α is refraction angle, and coordinate (m, n) represents the position coordinates of pixel on X-ray detector；T represents phase stepping Total step number；P₂Represent analysis grating G₂Period；D is phase grating G₁With analysis grating G₂The distance between, the phase grating G₁It is arranged between sample stage and X-ray tube and close to the sample stage；

The absorption information calculation formula of sample is：

In formula, A (m, n) represents absorption image.

8. device according to claim 5, which is characterized in that the device further includes：

For being directed to sample, the aluminium and organic glass of same thickness are penetrated using X ray for amending unit, real by measuring The absorption data and refraction data on border carry out X ray Hardening correction；Aluminium therein is used for simulating bone tissue, and organic glass is used for Simulate soft tissue.