CN110123349B - Bone mineral density measuring method and device - Google Patents
Bone mineral density measuring method and device Download PDFInfo
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- CN110123349B CN110123349B CN201910376259.9A CN201910376259A CN110123349B CN 110123349 B CN110123349 B CN 110123349B CN 201910376259 A CN201910376259 A CN 201910376259A CN 110123349 B CN110123349 B CN 110123349B
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Abstract
The invention discloses a bone mineral density measuring method and a device, wherein the method comprises the following steps: collecting a low-energy scattering sampling image and a low-energy target image of a part to be scanned of a patient under the same low-energy exposure condition, and collecting a high-energy scattering sampling image and a high-energy target image under the same high-energy exposure condition; respectively determining scattering components according to the low-energy scattering sampling image and the high-energy scattering sampling image to obtain a low-energy scattering component and a high-energy scattering component; removing the low-energy scattering component from the low-energy target image to obtain a low-energy correction image after scattering, and removing the high-energy scattering component from the high-energy target image to obtain a high-energy correction image after scattering; and determining the bone density of the scanning part according to the low-energy correction image and the high-energy correction image. The measuring method can remove the influence of scattering on the quality of the target image in the scanning process, thereby improving the accuracy of the bone density measuring result.
Description
Technical Field
The invention relates to the technical field of medical image processing, in particular to a bone mineral density measuring method and device.
Background
In recent years, osteoporosis has received increasing attention, and bone mineral density measurement can accurately and quantitatively give the diagnosis result of the bone of a tester.
Currently, the medical imaging principles for determining bone mineral density mainly include: dual energy X-ray absorption assay, photon absorption method, neutron activation analysis method, ultrasonic quantitative measurement and nuclear magnetic resonance measurement method; among them, the dual-energy X-ray absorption measurement method has the advantages of high imaging speed and good result stability, and is generally used as a measurement method recommended in medical diagnosis.
The existing bone density measuring instrument based on the dual-energy X-ray absorption measuring method mostly adopts a fan-shaped beam X-ray scanning mode, and a slit collimator is usually added between a bulb tube and a flat panel detector, so that rays irradiate an interested region in a fan shape, and the mode has large primary scanning area and short scanning time. However, this approach has the following problems: the utilization rate of the rays is reduced because the rays need to pass through the slit collimator first; when the rays pass through the human body, scattering is brought about due to the influence of bones and soft tissues, thereby affecting the accuracy of the final bone density value.
In view of this, how to improve the existing bone mineral density measurement mode to improve the accuracy of bone mineral density measurement is a technical problem that needs to be solved by those skilled in the art.
Disclosure of Invention
The invention aims to provide a bone mineral density measuring method and device, which can reduce the influence of scattering on the quality of a scanned image, thereby improving the accuracy of bone mineral density measurement.
In order to solve the technical problems, the invention provides a bone mineral density measuring method, which comprises the following steps:
collecting a low-energy scattering sampling image and a low-energy target image of a part to be scanned of a patient under the same low-energy exposure condition, and collecting a high-energy scattering sampling image and a high-energy target image under the same high-energy exposure condition;
respectively determining scattering components according to the low-energy scattering sampling image and the high-energy scattering sampling image to obtain a low-energy scattering component and a high-energy scattering component;
removing the low-energy scattering component from the low-energy target image to obtain a low-energy correction image after scattering, and removing the high-energy scattering component from the high-energy target image to obtain a high-energy correction image after scattering;
and determining the bone density of the scanning part according to the low-energy correction image and the high-energy correction image.
A bone density measurement method as described above, the method further comprising:
collecting a low-energy aerial image under the same low-energy exposure condition and a high-energy aerial image under the same high-energy exposure condition;
obtaining the average gray value I of the low-energy aerial image OL And the average gray value I of the high-energy aerial image OH ；
The determining the bone density of the scanning site from the low energy corrected image and the high energy corrected image includes:
obtaining an average gray value GrayH of a corresponding area of a scanning part in the high-energy correction image and an average gray value GrayL of a corresponding area of the scanning part in the low-energy correction image; obtaining the area S of a corresponding area of a scanning part in a scanning image;
the bone density of the scanned part is obtained by the following calculation formula:
R＝ρ*S/t；
t＝a+bH+cL+dHL+eH 2 +fL 2 ；
H＝-ln(GrayH/I OH )；
L＝-ln(GrayL/I OL )；
wherein R is bone density, ρ is bone salt density, and t is bone thickness;
h is the attenuation value of the corresponding area of the scanning part in the high-energy correction image, and L is the attenuation value of the corresponding area of the scanning part in the low-energy correction image;
a. b, c, d, e, f are correction coefficients.
The bone mineral density measuring method described above, the method for determining each correction coefficient a, b, c, d, e, f includes:
preparing a plurality of simulated tissues simulating a part to be scanned, wherein the simulated tissues comprise simulated soft tissues and simulated bone tissues; thickness t of simulated bone tissue of each of the simulated tissues n Different;
obtaining low-energy simulation images after the scattering of the simulation tissues under the same low-energy exposure condition, and obtaining high-energy simulation images after the scattering of the simulation tissues under the same high-energy exposure condition;
calculating a low-energy attenuation value L of a corresponding region of the simulated tissue in the low-energy simulated image of each simulated tissue n And a high-energy attenuation value H of a corresponding region of the simulated tissue in the high-energy simulated image of each of the simulated tissues n ；
Wherein L is n ＝-ln(GrayL n /I OL )，H n ＝-ln(GrayH n /I OH ) The method comprises the steps of carrying out a first treatment on the surface of the Wherein GrayL n GrayH is the average gray value of the corresponding region of the simulated tissue in the low-energy simulated image n An average gray value of a corresponding region of the simulated tissue in the high-energy simulated image;
each of the simulated bone tissuesThickness t of (2) n Corresponding low energy attenuation value L n High energy attenuation value H n Substitution into formula t n ＝a+bH n +cL n +dH n L n +eH n 2 +fL n 2 And calculates each correction coefficient a, b, c, d, e, f.
The bone mineral density measuring method described above also varies the thickness of the simulated soft tissue simulating a plurality of the simulated tissues of the same part to be scanned.
The bone density measuring method as described above, the simulated soft tissue is made of polymethyl methacrylate, and the simulated skeletal tissue is made of aluminum.
As described above with respect to the bone mineral density measurement method,
the method for acquiring the low-energy scattering sampling image and the low-energy target image of the part to be scanned of the patient under the same low-energy exposure condition, and the high-energy scattering sampling image and the high-energy target image under the same high-energy exposure condition comprises the following steps: placing an attenuation die body for scatter sampling in an optical path forming the low-energy scatter sampling image and the high-energy scatter sampling image; the attenuation die body comprises a plurality of attenuation bodies arranged in a matrix form;
the method for determining the scattering component comprises the following steps: and acquiring a corresponding scattering value of an attenuation body position in the attenuation die body in a scattering sampling image, determining a scattering value of a non-attenuation body position in the attenuation die body according to the acquired scattering value to determine a preliminary scattering image, performing smoothing on the preliminary scattering image to obtain a scattering image, and obtaining the scattering component according to the scattering image.
The method for measuring bone mineral density as described above, the attenuating body is specifically a lead plate.
In the bone mineral density measuring method, in the attenuating die body, the attenuating bodies are arranged at equal intervals.
The invention also provides a bone density measuring device which comprises a ray generator, an image collector, a scattering prediction module and a bone density determination module;
the radiation generator is capable of generating low energy spectrum radiation forming a low energy exposure condition and high energy spectrum radiation forming a high energy exposure condition, and is capable of switching between a first optical path for forming a low energy target image and a high energy target image and a second optical path for forming a low energy scattering sampling image and a high energy scattering sampling image;
the first light path is provided with a filter, and the second light path is provided with an attenuation die body for scattering sampling;
the image collector is used for collecting projection images generated by the position, to be scanned, of the patient scanned by the ray generator so as to obtain the low-energy scattering sampling image and the low-energy target image under the same low-energy exposure condition, and obtain the high-energy scattering sampling image and the high-energy target image under the same high-energy exposure condition;
the scattering prediction module is used for respectively determining scattering components according to the low-energy scattering sampling image and the high-energy scattering sampling image obtained by the image collector to obtain a low-energy scattering component and a high-energy scattering component;
the bone mineral density determining module is used for obtaining a low-energy correction image after scattering and a high-energy correction image after scattering according to the low-energy target image and the high-energy target image obtained by the image collector and the low-energy scattering component and the high-energy scattering component output by the scattering prediction module, and determining the bone mineral density of the scanning part according to the low-energy correction image and the high-energy correction image.
The bone mineral density measuring device as described above, the radiation generator comprising a bulb, a high voltage generator and a beam limiter, wherein the beam limiter is switchable between the first optical path and the second optical path; the attenuation die body covers the opening of the beam limiter in a state that the beam limiter is switched to the second light path;
the image collector is specifically a flat panel detector.
The bone density measuring device as described above, the attenuation body including a plurality of attenuation bodies arranged in a matrix form;
the scattering prediction module comprises an acquisition unit and a processing unit;
the acquisition unit can acquire a first scattering value corresponding to the position of the attenuation body in the attenuation die body in the scattering sampling image;
the processing unit can calculate a second scattering value corresponding to the non-attenuating body position in the attenuating die body in the scattering sampling image according to the first scattering value so as to determine a preliminary scattering image;
the processing unit is further capable of smoothing the preliminary scatter image to obtain a scatter image and determining the scatter component from the scatter image.
The bone mineral density measuring device further comprises a storage module, wherein the bone mineral density determining module comprises an identification unit, an image processing unit and a calculation unit;
the storage module is pre-stored with low-energy exposure parameters, high-energy exposure parameters and correction coefficients corresponding to the scanning part;
the ray generator can call the corresponding low-energy exposure parameters and high-energy exposure parameters in the storage module according to the part to be scanned so as to generate corresponding low-energy rays and high-energy rays;
the identification unit can identify the area corresponding to the scanning part in the scanned image and determine the area of the corresponding area;
the image processing unit is used for processing the target image according to the scattering component so as to obtain a corrected image after scattering;
the computing unit comprises a first computing unit, a second computing unit and a third computing unit; the first calculation unit is used for calculating attenuation values of the corresponding areas of the scanning parts in the corrected image according to the corrected image;
the second calculation unit is used for calculating the bone thickness of the scanning part according to the attenuation value and the correction coefficient corresponding to the scanning part, which is prestored in the invoked storage module;
the third calculation unit is used for calculating the bone density of the scanning part according to the bone thickness and the area determined by the identification unit.
According to the bone mineral density measuring method and device, the target image of the scanning part is obtained, meanwhile, the scattering sampling image under the same exposure condition is obtained, the scattering component is determined based on the scattering sampling image, the target image is subjected to scattering removal treatment according to the scattering component to obtain the corrected image, and the bone mineral thickness of the scanning part is determined according to the corrected image; the measuring method and the measuring device can remove the influence of scattering on the quality of the target image in the scanning process, thereby improving the accuracy of the bone mineral density measuring result.
Drawings
FIG. 1 is a flow chart of an embodiment of a bone mineral density measurement method according to the present invention;
FIG. 2 is a flow chart of a method for determining a scattering component in an embodiment;
FIG. 3 is a flowchart illustrating a method for determining correction coefficients in a bone thickness calculation formula according to an embodiment;
FIG. 4 is a schematic diagram of an attenuating die body in an exemplary embodiment;
fig. 5 a-5 c show a schematic view of the processing of the scatter sample image by the scatter prediction module when the scan site is an arm.
Detailed Description
In order to better understand the aspects of the present invention, the present invention will be described in further detail with reference to the accompanying drawings and detailed description.
For ease of understanding and brevity of description, the following description is provided in conjunction with methods and apparatus for measuring bone mineral density, and the discussion of the advantageous effects will not be repeated.
Referring to fig. 1, fig. 1 is a flowchart illustrating an embodiment of a bone mineral density measurement method according to the present invention.
In this embodiment, the bone mineral density measuring method includes:
step S100, collecting a low-energy scattering sampling image and a low-energy target image of a part to be scanned of a patient under the same low-energy exposure condition, and collecting a high-energy scattering sampling image and a high-energy target image under the same high-energy exposure condition;
the bone mineral density measuring device comprises a ray generator and an image collector, wherein the ray generator is used for generating rays with high energy and low energy spectrums so as to form a low-energy exposure condition and a high-energy exposure condition required when scanning a scanning position.
The radiation generator is further capable of switching between a first optical path in which the filter is placed and a second optical path in which an attenuation matrix is placed, wherein the attenuation matrix is used for scatter sampling.
When the ray generator scans the part to be scanned through the first optical path, the image acquired by the image acquisition unit is a target image of the part to be scanned, and when the ray generator scans the part to be scanned through the second optical path, the image acquisition unit acquires a scattering sampling image due to the arrangement of the attenuation die body.
Here, the filtering is used to remove low-energy rays and reduce the influence of radiation hardening on the quality of the target image.
It should be further noted that the low energy and the high energy referred to herein are relative concepts, and the parameters corresponding to the low energy exposure condition and the high energy exposure condition are different for different scan sites, and may be specifically determined according to practical application requirements.
Step 200, respectively determining scattering components according to the low-energy scattering sampling image and the high-energy scattering sampling image to obtain the low-energy scattering component and the high-energy scattering component;
removing low-energy scattering components from the low-energy target image to obtain a low-energy correction image after scattering, and removing high-energy scattering components from the high-energy target image to obtain a high-energy correction image after scattering;
and determining the bone density of the scanning part according to the low-energy correction image and the high-energy correction image.
The bone mineral density measuring device also comprises a scattering prediction module and a bone mineral density determination module.
The scattering prediction module can acquire the low-energy scattering sampling image and the high-energy scattering sampling image acquired by the image acquisition device, and determine the low-energy scattering component of the low-energy scattering sampling image and the high-energy scattering component of the high-energy scattering sampling image.
It should be noted that in practical applications, the low-energy scattering component and the high-energy scattering component are also represented in the form of images.
The bone mineral density determining module can determine the bone mineral density of the scanning part according to the low-energy scattering component and the high-energy scattering component output by the scattering prediction module, and the low-energy target image and the high-energy target image acquired by the image acquisition device.
Specifically, the bone mineral density determining module can remove the low-energy scattering component from the low-energy target image to obtain a low-energy correction image, remove the high-energy scattering component from the high-energy target image to obtain a high-energy correction image, and determine the bone mineral density according to the low-energy correction image and the high-energy correction image of the scanning part.
In a specific scheme, the ray generator comprises a bulb tube, a high-voltage generator and a beam limiter, wherein the beam limiter can be switched between a first optical path and a second optical path, and particularly, the beam limiter can be used for switching a filtering die body used for scattering sampling and placed in the optical path, so that the switching between the first optical path and the second optical path is realized; and when the beam limiter is switched to the second light path, the attenuation die body covers the opening of the beam limiter.
The image collector specifically selects the flat panel detector, so that the ray utilization rate is high, the speed is high, the cost is lower, and the application scene can be enlarged.
As described above, the bone mineral density measuring method and apparatus provided in this embodiment acquire a scattering sampling image under the same exposure condition while acquiring a target image of a scanning region, determine a scattering component based on the scattering sampling image, and perform a scattering process on the target image according to the scattering component to obtain a corrected image, and determine a bone mineral thickness of the scanning region according to the corrected image; the measuring method and the measuring device can remove the influence of scattering on the quality of the target image in the scanning process, thereby improving the accuracy of the bone mineral density measuring result.
In this embodiment, in step S100 of the bone mineral density measuring method, a low-energy aerial image under the same low-energy exposure condition and a high-energy aerial image under the same high-energy exposure condition are also acquired.
That is, the low-energy exposure conditions for acquiring the low-energy aerial image, the low-energy scattering sampling image and the low-energy target image are the same, and the high-energy exposure conditions for acquiring the high-energy aerial image, the high-energy scattering sampling image and the high-energy target image are the same.
In step S200, the average gray level I is determined according to the low-energy aerial image OL Determining the average gray value I according to the high-energy aerial image OH 。
The bone density of the scanning site is determined by the following calculation formula (1).
R＝ρ*S/t (1)
Wherein R is bone density, ρ is bone salt density, the value is a known fixed value, t is bone thickness, and S is the area of the corresponding region of the scanned part in the scanned image. Here, the scan image includes a scatter sampling image obtained by scanning the scan region, a target image, a processed corrected image, or the like.
It should be noted that, when the scanning part is scanned, the projection image obtained finally is usually a square picture containing the scanning part, that is, the projection image is not an image corresponding to the scanning part, but only the area information corresponding to the scanning part is actually needed to be known, and the area S of the area corresponding to the scanning part in the formula (1) can be obtained according to the acquired target image; it will be appreciated that, for the same scan region, the areas of the scan region in the obtained scatter sample image, the target image and the corrected image are substantially identical, but because the scatter sample image has an attenuation module, the acquisition of the area is affected, so in the actual operation process, the area of the scan region corresponding to the target image or the corrected image after processing is preferably determined, so as to improve the measurement accuracy.
The bone thickness t in the formula (1) is determined by calculation of the following formula (2):
t＝a+bH+cL+dHL+eH 2 +fL 2 (2)
where H is the attenuation value of the region corresponding to the scanning location in the high-energy corrected image, L is the attenuation value of the region corresponding to the scanning location in the low-energy corrected image, and a, b, c, d, e, f are correction coefficients.
Each correction coefficient can be determined in advance, and only the correction coefficient is required to be called during calculation.
Wherein H and L can be determined by calculation of the following formulas (3), (4), respectively:
H＝-ln(GrayH/I OH ) (3)
L＝-ln(GrayL/I OL ) (4)
in this embodiment, the bone mineral density measuring device further includes a memory module, and the memory module pre-stores the low-energy exposure parameter, the high-energy exposure parameter, and the correction coefficient in formula (2) corresponding to the scanning position.
As described above, the low-energy exposure parameter and the high-energy exposure parameter are different for different scanning sites, and similarly, the specific value of the correction coefficient a, b, c, d, e, f in the formula (2) is also different for different scanning sites. That is, each scanning position corresponds to a group of low-energy exposure parameters, high-energy exposure parameters and correction coefficients.
In practical application, a plurality of scanning positions and parameters corresponding to the scanning positions one by one can be stored in the storage module in advance, and corresponding calculation parameters can be called according to the scanning positions during scanning.
Further, the average gray value I of the blank image under the low-energy exposure parameters corresponding to the scanning position can be set in advance OL And average gray value I of aerial image under high-energy exposure parameter corresponding to scanning position OH Stored in a memory module for recall as needed during scanning.
It will be appreciated that the low energy exposure parameters and the high energy exposure parameters are determined for the determined scan region, and accordingly the average gray level I of the aerial image at the low energy exposure parameters and the high energy exposure parameters OL And I OH The method is also determined, and the bone mineral density is stored in the storage module after being calculated in advance, so that the flow of actual scanning and calculating the bone mineral density can be shortened, and the time required for measuring the bone mineral density can be shortened.
In this embodiment, the bone mineral density determining module of the bone mineral density measuring device specifically includes an identifying unit, an image processing unit, and a calculating unit.
The identification unit can identify the area corresponding to the scanning part in the scanned image and determine the area of the corresponding area.
The image processing unit is used for processing the target image according to the scattering component determined by the scattering prediction module so as to obtain a corrected image after scattering; specifically, the image processing unit can remove the low-energy scattering component from the low-energy target image to obtain a low-energy correction image, and remove the high-energy scattering component from the high-energy target image to obtain a high-energy correction image.
The computing unit specifically comprises a first computing unit, a second computing unit and a third computing unit.
The first calculating unit is used for calculating an attenuation value L of a corresponding area of a scanning part in the low-energy correction image according to the low-energy correction image determined by the image processing unit, and calculating an attenuation value H of the corresponding area of the scanning part in the high-energy correction image according to the high-energy correction image determined by the image processing unit. The first calculation unit may call the I corresponding to the scan location stored in advance in the memory module during calculation of the attenuation value OH And I OL . Specifically, the first calculation unit may store the above formulas (3), (4) to be called to calculate the relevant attenuation values.
The second calculation unit is used for calculating the bone thickness of the scanning part according to the attenuation value H, L calculated by the first calculation unit and calling the correction coefficient corresponding to the scanning part in the storage module; specifically, the above formula (2) may be stored in the second calculation unit to be called to calculate the bone thickness.
The third calculation unit is used for calculating the bone mineral density of the scanning part according to the bone mineral thickness calculated by the second calculation unit and the area determined by the identification unit, and specifically, the third calculation unit can store the formula (1) so as to call for calculating the bone mineral thickness.
In this embodiment, in step S100 of the bone mineral density measuring method, an attenuation phantom for scatter sampling is placed in an optical path forming a scatter sampling image; wherein the attenuation die body comprises a plurality of attenuation bodies arranged in a matrix form;
referring to fig. 2, fig. 2 is a flow chart illustrating a method for determining a scattering component in an embodiment.
In step S200, the method for determining the scattering component includes:
a1, acquiring a corresponding scattering value of an attenuation body position in an attenuation die body in a scattering sampling image;
a2, determining a scattering value of a non-attenuating body position in the attenuation die body according to the arrangement parameters of the attenuating body in the attenuation die body and the acquired scattering value so as to determine a preliminary scattering image;
and A3, performing smoothing treatment on the preliminary scattering image to obtain a scattering image, and determining a scattering component according to the scattering image.
In the bone density measuring device, the attenuation die bodies placed in the second light path are a plurality of attenuation bodies which are arranged in a matrix form; the scattering prediction module specifically comprises an acquisition unit and a processing unit, wherein the acquisition unit can acquire a first scattering value corresponding to the position of an attenuation body in the attenuation die body in the scattering sampling image, the processing unit can calculate a second scattering value corresponding to the position of a non-attenuation body in the attenuation die body in the scattering sampling image according to the first scattering value so as to determine a preliminary scattering image, and the processing unit can also carry out smoothing processing on the preliminary scattering image so as to obtain the scattering image and determine a scattering component according to the scattering image.
Specifically, after the ray emitted by the bulb tube passes through the attenuation body, the ray which can be received by the flat panel detector is almost 0, so that it can be considered that all gray values obtained by scattering the position of the attenuation body in the sampled image are caused by scattering, and the gray values can be used for representing the scattering values, that is, the gray values of the position of the attenuation body in the scattered sampled image are the first scattering values.
Because the relative positions of the attenuation bodies in the attenuation die body are determined, the second scattering value of the position of the non-attenuation body can be determined according to the relative position relation among the attenuation bodies and the first scattering value.
Specifically, it can be determined by linear interpolation, and it is understood that the preliminary scattering image after the linear interpolation processing is not smooth, but in practice the scattering itself should be smooth, so that after the preliminary scattering image is obtained by the linear interpolation processing, the preliminary scattering image is further subjected to smoothing processing to obtain a scattering image in which the scattering component can be determined. The smoothing method may specifically be a filtering method, and of course, other processing methods may be selected in practice.
It should be noted here that in this embodiment the scattering component is represented in the form of an image, i.e. the scattering image obtained in the manner described above corresponds to the scattering component.
Through experimental study, the attenuation body in the attenuation die body is specifically selected from lead plates so as to ensure the accuracy of scattering prediction.
When the device is specifically arranged, all the attenuation bodies are arranged at equal intervals in the attenuation die body, so that the subsequent calculation of the scattering value of the position of the non-attenuation body is facilitated.
Referring to fig. 4, fig. 4 is a schematic diagram of an attenuation body according to an embodiment, in which attenuation bodies 10 are arranged at equal intervals.
The thickness, diameter and interval distance between lead plates of the attenuation body can be set according to practical application requirements.
Referring to fig. 5 a-5 c, fig. 5 a-5 c show a schematic view of the processing of the scatter sample image by the scatter prediction module when the scan region is an arm.
Fig. 5a shows a scatter sampling image obtained by scanning an arm, fig. 5b shows a preliminary scatter image obtained by interpolating the image shown in fig. 5a, from which it can be seen that the image obtained by interpolation is not smooth, the edge of the corresponding region of the arm is relatively sharp, and fig. 5c shows a scatter image obtained by smoothing the image shown in fig. 5 b.
Referring to fig. 3, fig. 3 is a flowchart illustrating a method for determining a correction factor in a bone thickness calculation formula according to an embodiment.
In this embodiment, the method for determining each correction coefficient a, b, c, d, e, f in the above formula (2) includes:
step B1, preparing a plurality of simulated tissues simulating a part to be scanned, wherein the simulated tissues comprise simulated soft tissues and simulated bone tissues; simulated skeletal tissue of each simulated tissueThickness t n Different;
it will be appreciated that for a scan site, it is desirable to prepare a plurality of simulated tissues of different thicknesses that simulate the scan site;
step B2, obtaining low-energy simulation images after the scattering of the simulation tissues under the same low-energy exposure condition; obtaining high-energy simulation images of the scattered simulated tissues under the same high-energy exposure condition;
it will be appreciated that the exposure conditions for scanning the simulated tissue in this step are the same as those of the part to be scanned, so that an accurate correction factor corresponding to the part to be scanned can be obtained.
The method for obtaining the low-energy simulated image after the scattering of each simulated tissue is similar to the method for obtaining the corrected image of the part to be scanned, and the description is not repeated here.
Step B3, calculating a low-energy attenuation value L of a corresponding region of the simulated tissue in the low-energy simulated image of each simulated tissue n And a high-energy attenuation value H of a corresponding region of the simulated tissue in the high-energy simulated image of each simulated tissue n ；
Wherein L is n ＝-ln(GrayL n /I OL )，H n ＝-ln(GrayH n /I OH )；
Wherein GrayL n GrayH is the average gray value of the corresponding region of the simulated tissue in the low-energy simulated image n For the average gray value of the corresponding region of the simulated tissue in the high-energy simulated image, I OL Is the average gray value of the low-energy aerial image under the same low-energy exposure condition, I OH The average gray value of the high-energy aerial image under the same high-energy exposure condition.
It should be noted that, as described above, in the actual bone mineral density measurement process, the calculation of bone mineral density also involves I OH And I OL And these two values may be determined in advance to be called upon for measurement calculations, while for different scan sites, each correction factor also needs to be stored in advance for later call upon measurement calculations, so that for the same scan site,can be firstly determined I OH And I OL 。
Step B4, thickness t of simulated bone tissue of each simulated tissue n Corresponding low energy attenuation value L n High energy attenuation value H n Substitution into formula t n ＝a+bH n +cL n +dH n L n +eH n 2 +fL n 2 And calculates each correction coefficient a, b, c, d, e, f.
Obviously, the formula in this step is the formula (2) mentioned above
It will be appreciated that the thickness t of simulated bone tissue of each simulated tissue n It is known that, after step B2 and step B3, a low energy attenuation value and a high energy attenuation value of each simulated tissue can be obtained, and an overdetermined equation can be obtained after substituting the low energy attenuation value and the high energy attenuation value into the formula (2):
t 1 ＝a+bH 1 +cL 1 +dH 1 L 1 +eH 1 2 +fL 1 2
t 2 ＝a+bH 2 +cL 2 +dH 2 L 2 +eH 2 2 +fL 2 2
t 3 ＝a+bH 3 +cL 3 +dH 3 L 3 +eH 3 2 +fL 3 2
……
t n ＝a+bH n +cL n +dH n L n +eH n 2 +fL n 2
the 6 correction coefficients a, b, c, d, e, f may be calculated using a least squares fit method or other calculation method.
In practice, the number of simulated tissues corresponding to a part to be scanned and the thickness of each simulated tissue may be set according to the calculation requirements, so long as the above 6 correction coefficients corresponding to the part to be scanned can be determined.
In a specific scheme, the simulated soft tissue of the simulated tissue can be made of polymethyl methacrylate (PMMA), the simulated bone tissue can be made of aluminum, and the simulated tissue can be conveniently scanned. In practical applications, the simulated tissue may be made of other materials.
The thickness of soft tissue and bone is different for human body parts, and in practical application, the thickness of the simulated tissue can be determined by referring to the corresponding part to be scanned of the simulated tissue when the simulated tissue is prepared.
It should be noted that, since the thickness of the soft tissue also affects the attenuation value, in the above step B1 of determining the correction coefficient, the thickness of the simulated soft tissue of each simulated tissue is set differently, in addition to the thickness of the simulated bone tissue of each simulated tissue, for a plurality of simulated tissues simulating the same part to be scanned.
The method and the device for measuring the bone mineral density provided by the invention are described in detail. The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to facilitate an understanding of the method of the present invention and its core ideas. It should be noted that it will be apparent to those skilled in the art that various modifications and adaptations of the invention can be made without departing from the principles of the invention and these modifications and adaptations are intended to be within the scope of the invention as defined in the following claims.
Claims (12)
1. A method of bone density measurement, the method comprising:
collecting a low-energy scattering sampling image and a low-energy target image of a part to be scanned of a patient under the same low-energy exposure condition, and collecting a high-energy scattering sampling image and a high-energy target image under the same high-energy exposure condition; the low-energy target image and the high-energy target image are collected under a first optical path with filtering placed, the low-energy scattering sampling image and the high-energy scattering sampling image are collected under a second optical path with an attenuation die body placed, and the attenuation die body covers an opening of the beam limiter when the beam limiter is switched to the second optical path, and the attenuation die body comprises a plurality of attenuation bodies arranged in a matrix form;
respectively determining scattering components according to the low-energy scattering sampling image and the high-energy scattering sampling image to obtain a low-energy scattering component and a high-energy scattering component;
removing the low-energy scattering component from the low-energy target image to obtain a low-energy correction image after scattering, and removing the high-energy scattering component from the high-energy target image to obtain a high-energy correction image after scattering;
and determining the bone density of the scanning part according to the low-energy correction image and the high-energy correction image.
2. The bone mineral density measurement method of claim 1, wherein the method further comprises:
collecting a low-energy aerial image under the same low-energy exposure condition and a high-energy aerial image under the same high-energy exposure condition;
obtaining the average gray value I of the low-energy aerial image OL And the average gray value I of the high-energy aerial image OH ；
The determining the bone density of the scanning site from the low energy corrected image and the high energy corrected image includes:
obtaining an average gray value GrayH of a corresponding area of a scanning part in the high-energy correction image and an average gray value GrayL of a corresponding area of the scanning part in the low-energy correction image; obtaining the area S of a corresponding area of a scanning part in a scanning image;
the bone density of the scanned part is obtained by the following calculation formula:
R＝ρ*S/t；
t＝a+bH+cL+dHL+eH 2 +fL 2 ；
H＝-ln(GrayH/I OH )；
L＝-ln(GrayL/I OL )；
wherein R is bone density, ρ is bone salt density, and t is bone thickness;
h is the attenuation value of the corresponding area of the scanning part in the high-energy correction image, and L is the attenuation value of the corresponding area of the scanning part in the low-energy correction image;
a. b, c, d, e, f are correction coefficients.
3. The bone mineral density measurement method according to claim 2, wherein the determination method of each correction factor a, b, c, d, e, f includes:
preparing a plurality of simulated tissues simulating a part to be scanned, wherein the simulated tissues comprise simulated soft tissues and simulated bone tissues; thickness t of simulated bone tissue of each of the simulated tissues n Different;
obtaining low-energy simulation images after the scattering of the simulation tissues under the same low-energy exposure condition, and obtaining high-energy simulation images after the scattering of the simulation tissues under the same high-energy exposure condition;
calculating a low-energy attenuation value L of a corresponding region of the simulated tissue in the low-energy simulated image of each simulated tissue n And a high-energy attenuation value H of a corresponding region of the simulated tissue in the high-energy simulated image of each of the simulated tissues n ；
Wherein L is n ＝-ln(GrayL n /I OL )，H n ＝-ln(GrayH n /I OH ) The method comprises the steps of carrying out a first treatment on the surface of the Wherein GrayL n GrayH is the average gray value of the corresponding region of the simulated tissue in the low-energy simulated image n An average gray value of a corresponding region of the simulated tissue in the high-energy simulated image;
thickness t of each of the simulated bone tissues n Corresponding low energy attenuation value L n High energy attenuation value H n Substitution into formula t n ＝a+bH n +cL n +dH n L n +eH n 2 +fL n 2 And calculates each correction coefficient a, b, c, d, e, f.
4. The bone mineral density measuring method according to claim 3, wherein the simulated soft tissue thickness of a plurality of the simulated tissues simulating the same part to be scanned is also different.
5. The bone mineral density measurement method according to claim 3, wherein the simulated soft tissue is made of polymethyl methacrylate and the simulated skeletal tissue is made of aluminum.
6. The method for measuring bone mineral density according to any one of claims 1 to 5, wherein,
the method for determining the scattering component comprises the following steps: and acquiring a corresponding scattering value of an attenuation body position in the attenuation die body in a scattering sampling image, determining a scattering value of a non-attenuation body position in the attenuation die body according to the acquired scattering value to determine a preliminary scattering image, performing smoothing on the preliminary scattering image to obtain a scattering image, and obtaining the scattering component according to the scattering image.
7. The bone mineral density measurement method of claim 6, wherein the attenuating body is embodied as a lead plate.
8. The method of measuring bone density according to claim 6, wherein the attenuating bodies are arranged at equal intervals in the attenuating body.
9. The bone density measuring device is characterized by comprising a ray generator, an image collector, a scattering prediction module and a bone density determination module;
the radiation generator is capable of generating low energy spectrum radiation forming a low energy exposure condition and high energy spectrum radiation forming a high energy exposure condition, and is capable of switching between a first optical path for forming a low energy target image and a high energy target image and a second optical path for forming a low energy scattering sampling image and a high energy scattering sampling image;
the first light path is provided with a filter, and the second light path is provided with an attenuation die body for scattering sampling; the attenuation die body covers the opening of the beam limiter when the beam limiter of the ray generator is switched to the second optical path; the attenuation die body comprises a plurality of attenuation bodies arranged in a matrix form;
the image collector is used for collecting projection images generated by the position, to be scanned, of the patient scanned by the ray generator so as to obtain the low-energy scattering sampling image and the low-energy target image under the same low-energy exposure condition, and obtain the high-energy scattering sampling image and the high-energy target image under the same high-energy exposure condition;
the scattering prediction module is used for respectively determining scattering components according to the low-energy scattering sampling image and the high-energy scattering sampling image obtained by the image collector to obtain a low-energy scattering component and a high-energy scattering component;
the bone mineral density determining module is used for obtaining a low-energy correction image after scattering and a high-energy correction image after scattering according to the low-energy target image and the high-energy target image obtained by the image collector and the low-energy scattering component and the high-energy scattering component output by the scattering prediction module, and determining the bone mineral density of the scanning part according to the low-energy correction image and the high-energy correction image.
10. The bone mineral density measurement device of claim 9 wherein the radiation generator comprises a bulb, a high voltage generator, and a beam limiter, wherein the beam limiter is switchable between the first optical path and the second optical path;
the image collector is specifically a flat panel detector.
11. The bone density measurement device of claim 9, wherein the scatter prediction module comprises an acquisition unit and a processing unit;
the acquisition unit can acquire a first scattering value corresponding to the position of the attenuation body in the attenuation die body in the scattering sampling image;
the processing unit can calculate a second scattering value corresponding to the non-attenuating body position in the attenuating die body in the scattering sampling image according to the first scattering value so as to determine a preliminary scattering image;
the processing unit is further capable of smoothing the preliminary scatter image to obtain a scatter image and determining the scatter component from the scatter image.
12. The bone mineral density measurement device of any one of claims 9-11, further comprising a memory module, the bone mineral density determination module comprising an identification unit, an image processing unit, and a calculation unit;
the storage module is pre-stored with low-energy exposure parameters, high-energy exposure parameters and correction coefficients corresponding to the scanning part;
the ray generator can call the corresponding low-energy exposure parameters and high-energy exposure parameters in the storage module according to the part to be scanned so as to generate corresponding low-energy rays and high-energy rays;
the identification unit can identify the area corresponding to the scanning part in the scanned image and determine the area of the corresponding area;
the image processing unit is used for processing the target image according to the scattering component so as to obtain a corrected image after scattering;
the computing unit comprises a first computing unit, a second computing unit and a third computing unit; the first calculation unit is used for calculating attenuation values of the corresponding areas of the scanning parts in the corrected image according to the corrected image;
the second calculation unit is used for calculating the bone thickness of the scanning part according to the attenuation value and the correction coefficient corresponding to the scanning part, which is prestored in the invoked storage module;
the third calculation unit is used for calculating the bone density of the scanning part according to the bone thickness and the area determined by the identification unit.
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