CN112666194B - Virtual digital DR image generation method and DR virtual simulation instrument - Google Patents
Virtual digital DR image generation method and DR virtual simulation instrument Download PDFInfo
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Abstract
The invention discloses a method for generating a virtual digital DR image, which comprises the steps of constructing a DR digital object; constructing an X-ray energy spectrum curve emitted by the bulb tube; constructing a filtering material attenuation model; calculating the filtered X-ray energy spectrum; and calculating to obtain a virtual digital DR image by taking the DR digital object as a virtual scanning sample. The method can break through the original atlas range, namely, a DR digital human body or a DR digital object is used as a scanning sample to obtain DR images under different quality and quantity X-ray parameters and different positions and different fields, DR with different contrast ratios and signal-to-noise ratios is obtained in real time, and the method has wide application value.
Description
Technical Field
The invention relates to the technical field of DR simulation, in particular to a method for generating a virtual digital DR image and a DR virtual simulation instrument.
Background
The Digital Twin (Digital Twin) body is a virtual entity which is constructed in a virtual space and represents the real-time running state of a physical entity, has all-round functions of integrating geometric modeling, simulation and data analysis, and plays a role in comprehensive analysis decision. In the digital twinning technology, the simulation of the shape of a physical entity, a known (or experienced) physical law and an unknown physical law is realized through the construction of a geometric model, a mechanism model and a data model respectively. The digitalized twins are evaluated by Gartner in 2017 and 2018 for two consecutive years as one of ten major technologies affecting the future, and are gradually and widely applied to links of verification, design, test, maintenance, training and the like of large, complex, expensive and dangerous industrial products and systems.
Digital Radiography (DR), i.e., an image on an X-ray transmission path formed by a digital flat panel detector by using X-rays after transmitting a human body, mainly reflects the density of tissues and has superposition of front and rear image tissues. Computed Tomography (CT) uses X-rays that have been transmitted through a human body by rotation, and a tissue density distribution map on a ray transmission cross section is obtained by calculation. Compared with DR, the superposition of front and back image tissues is eliminated.
DR is the most widely used and popular equipment in medical imaging equipment, and therefore the principle and technology of DR is also the core teaching content of imaging technology specialties. Although the DR imaging principle is easier to understand compared with CT and MRI, the relationship between the positioning and the image, the selection of the optimal imaging parameter, and the relationship between the dosage and the imaging parameter are still difficult and key problems in teaching; because the DR real machine has a closed structure, radiation, a large occupied area, high requirements on field conditions and the like, batch and standardized teaching experiments cannot be carried out, the situation of 'watching by a group of people and demonstrating by one person' is caused, the teaching field is easy to be disordered, students cannot directly and intuitively carry out operation practice at once, the teaching effect is poor, and the students often only can further grope in medical practice; however, the number of patients in a hospital per day is huge, medical images become an important basis for diagnosis of doctors, and statistics shows that the diagnosis of more than 80% of diseases needs image participation, so that the hospital has no time and cannot search for sufficient time and conditions for students, and the patients can eat more dosage due to wrong operation and positioning, which is also not responsible for the patients, so that the necessary imaging principle and positioning operation skill need to be mastered before practice, and simultaneously, the idea and method for dosage control is established.
At present, there are two main forms of DR simulation teaching:
1. simulation teaching mode of the analog machine: the simulator with the core device, namely the bulb tube, removed by the real machine is used for carrying out positioning training, and the simulator has the advantages of solving the radiation problem, having low requirements on places, having the defects of limited quantity of built-in images, being incapable of generating images corresponding to different imaging parameters and different positioning positions in real time, and being consistent in occupied places with the real machine, and still unconditionally carrying out batch standardized teaching in most schools.
2. Scene and process simulation teaching mode: the method adopts a 3D interactive game form, simulates a shooting process of a patient after the patient enters a DR operation room, trains the humanistic care and standardized operation process of students, has the advantages of simulating the operation process and having interactivity, and has the defects that the process and the positioning training are solidified, the positioning training with high degree of freedom cannot be carried out, different imaging parameters cannot be corresponding to the process in real time, and corresponding images cannot be obtained by different positioning;
disclosure of Invention
Aiming at the technical problems of single image contrast, limited quantity and fixed section inclination angle of the traditional paper-plate DR atlas, the invention aims to: the method for generating the virtual digital DR image and the DR virtual simulation instrument are provided, the high-freedom DR virtual simulation instrument is constructed, high-freedom positioning training can be carried out, and the DR image under different imaging parameters and different positioning can be obtained in real time.
The technical scheme of the invention is as follows:
a method for generating a virtual digital DR image, comprising the steps of:
s01: constructing a DR digital object;
s02: constructing an X-ray energy spectrum curve emitted by the bulb tube;
s03: constructing a filtering material attenuation model;
s04: calculating the filtered X-ray energy spectrum;
s05: and calculating to obtain a virtual digital DR image by taking the DR digital object as a virtual scanning sample.
In a preferred technical solution, the method for constructing the DR digital object in step S01 includes the following steps:
s11: carrying out high-resolution isotropic tomography on a real object through dual-energy CT to obtain two groups of CT images with different energies, establishing a CT value matrix with a first energy and a CT value matrix with a second energy, and obtaining an electron density three-dimensional distribution matrix of each voxel of the object according to the CT value matrix with the first energy and the CT value matrix with the second energy;
s12: calculating an effective atomic number matrix according to the obtained electron density three-dimensional distribution matrix of the voxel;
s13: and calculating the electron density three-dimensional distribution matrix and the effective atomic number matrix of each voxel, and combining the electron density three-dimensional distribution matrix and the effective atomic number matrix with the three-dimensional space structure of the object to obtain a multi-dimensional matrix to obtain the DR digital object.
In a preferred technical solution, the method for constructing the energy spectrum curve of the X-ray emitted from the bulb in the step S02 includes:
s21: after the accelerated electrons impact the rhenium-tungsten alloy target or the molybdenum target, the generated X-ray continuous energy spectrum is as follows:
wherein mAs is the product of the set tube current (mA) and the exposure time(s), e is the electron electric quantity, r is the focal distance, F w (E) For intrinsic filtering effectiveness, E is the accelerated electron energy, N (E) is the number of X photons for a certain energy interval,
for photon yield per roentgen, dE is the photon energy interval;
s22: the characteristic energy spectrum of the generated X-ray is as follows:
wherein E is k The kth separated X-ray energy.
In a preferred embodiment, the filter model in step S03 includes an intrinsic filter model or an additional filter model, and each filter includes a type of filter material, a thickness of the filter material, and a shape of the filter material.
In a preferred embodiment, the method for calculating the filtered X-ray energy spectrum in step S04 includes:
s41: splitting the X-ray energy spectrum into n energy intervals, each energy interval being a source of single energy, i.e. a source of radiation of a single energy
E i ＝E i-1 + Δ, wherein, I i Representing the intensity of the ith interval X-ray energy, E i Representing the ith interval X-ray energy, E i-1 The energy of the (i-1) th interval X-ray is shown, and delta is a fixed value;
s42: and performing attenuation calculation on each single-energy ray source after passing through each filtering material, wherein the calculation formula is as follows:
wherein mu e To the attenuation coefficient, I i0 Is I i D is the thickness of the filter material, mu e ＝μ p +μ c ，μ p Is the photoelectric attenuation coefficient mu p ＝K*rou e *lamda 3 *Z 3.05 /(hc) 3 ，μ c Is the Compton attenuation coefficient mu c ＝K*rou e *lamada*Z/hc，rou e Is the electron density of the active material, lamda is the x-ray wavelength, Z is the effective atomic number, h is the Planck constant, c is the speed of light, and K is the coefficient;
s43: energy spectrum superposition is carried out on all the rays output after the single energy attenuation, and the filtered X-ray energy spectrum is obtained
In a preferred technical solution, the step S05 of calculating to obtain the virtual digital DR image includes:
s51: calculating the position of the space matrix of the corresponding part of the DR digital object in the light-beam device field;
s52: calculating a DR image range;
s53: according to the X-ray direction, according to the similarity proportion and the detector resolution ratio, performing interpolation, then projecting the interpolation layer by layer on the detector plane, accumulating the previous layer after each layer of data projection, and so on, and after all layers of projection are finished, according to the relational expression between the intensity I and the absorption coefficient u after the X-ray is incident on the object
Obtaining an expression of the discrete case as
Wherein, l is the ray penetration distance, N is the number of the separation units on the X-ray penetration path, I 0 And I is the X-ray intensity, μ, of the incident and emergent objects, respectively i The absorption coefficient of tissues with different unit lengths, and deltax is the unit length;
s54: and converting the X-ray intensity I of the emergent object into a brightness signal to obtain a virtual digital DR image.
The invention also discloses a DR virtual simulation instrument, which comprises:
the DR digital object constructing module is used for constructing a DR digital object;
the X-ray parameter construction module is used for constructing an X-ray energy spectrum curve emitted by the bulb tube;
the filtering model building module is used for building a filtering material attenuation model;
the filtered X-ray parameter calculation module is used for calculating a filtered X-ray energy spectrum;
and the scene construction module is used for constructing the equipment component and the object model for DR inspection, and setting the corresponding motion range and motion control function of the equipment component and the object model.
And the DR image calculation module is used for calculating to obtain a virtual digital DR image by taking the DR digital object as a virtual scanning sample.
In a preferred technical solution, the method for constructing the X-ray energy spectrum curve emitted by the bulb tube in the X-ray parameter construction module includes:
s21: after the accelerated electrons impact the rhenium-tungsten alloy target or the molybdenum target, the generated X-ray continuous energy spectrum is as follows:
wherein mAs is the product of the set tube current (mA) and the exposure time(s), e is the electron electric quantity, r is the focal distance, F w (E) For intrinsic filtering effectiveness, E is the accelerated electron energy, N (E) is the number of X photons for a certain energy interval,
for photon yield per roentgen, dE is the photon energy interval;
s22: the characteristic energy spectrum of the generated X-ray is as follows:
wherein, E k The kth separated X-ray energy.
In a preferred technical solution, the method for calculating the filtered X-ray energy spectrum in the filtered X-ray parameter calculation module includes:
s41: splitting the X-ray energy spectrum into n energy intervals, each energy interval being a source of single energy, i.e. a source of radiation of a single energy
E i ＝E i-1 + Δ, wherein, I i Representing the intensity of the ith interval X-ray energy, E i Representing the ith interval X-ray energy, E i-1 The energy of the X-ray at the interval i-1 is a fixed value;
s42: and performing attenuation calculation on each single-energy ray source after passing through each filtering material, wherein the calculation formula is as follows:
wherein mu e To be attenuation coefficient, I i0 Is I i D is the thickness of the filtered material, mu e ＝μ p +μ c ，μ p Is the photoelectric attenuation coefficient mu p ＝K*rou e *lamada 3 *Z 3.05 /(hc) 3 ，μ c Is the Compton attenuation coefficient mu c ＝K*rou e *lamada*Z/hc，rou e Is the electron density of the active material, lamda is the x-ray wavelength, Z is the effective atomic number, h is the Planck constant, c is the speed of light, and K is the coefficient;
s43: energy spectrum superposition is carried out on all the rays output after the single energy attenuation, and the filtered X-ray is obtainedEnergy spectrum
In a preferred technical scheme, the scene construction module further comprises a construction image range calculation model and an object positioning calculation model, wherein the image range calculation model is used for calculating the intersection of the X-ray irradiation range, the digital object range and the detection area range of the detector to serve as an effective exposure and detection area; the object positioning calculation model respectively performs corresponding translation and rotation operations on the three-dimensional object data at the original position according to a series of joint rotation actions of object positioning operations in a scene.
Compared with the prior art, the invention has the advantages that:
1. the DR virtual simulation instrument with high degree of freedom can break through the original atlas range, namely, the DR simulation instrument with high degree of freedom in different X-ray quality parameters, different filtering states, any inclination angles and any position can be obtained by taking a virtual CT digital human body or object as a scanning sample. Clinical DR imaging, once set up parameter scanning imaging, its image contrast basically has been fixed, if need obtain DR image under other condition or position, only scan once again. The invention can provide any DR image under different X-ray parameters, different radiation fields and different body positions according to the requirement on the basis of one-time double-energy CT imaging, and has important value.
2. The DR virtual simulation instrument with high degree of freedom can realize unlimited number of images, map information can break through the existing limitation of contrast and signal to noise ratio, and images with different contrasts and signal to noise ratios at any position can be realized. The method can also simulate the effect of generating artifact images with different effects, greatly broaden the concept of the original virtual digital map and enrich the research connotation of virtual digital people. The atlas not only can better meet the practical training function of image anatomy, but also can be used for developing clinical application and research, and can be used for teaching of human tomography anatomy and DR imaging diagnostics; meanwhile, the method can be used for comparison reference of clinical diagnosis to replace the DR map of the existing paper edition;
3. a typical disease DR digital human body is used as a virtual scanning sample, a DR simulation instrument is developed, the DR simulation instrument can be used for DR multi-scanning condition arbitrary body position imaging, and can be integrated on clinical DR equipment, so that multiple body position images can be obtained through one-time scanning, different angle image representations of the same position can be further obtained, and the application effect of the DR equipment is improved.
Drawings
The invention is further described with reference to the following figures and examples:
FIG. 1 is a flow chart of a method of generating a virtual digital DR image according to the present invention;
FIG. 2 is a schematic block diagram of a DR virtual simulation instrument of the present invention;
FIG. 3 is a flow chart of DR digital object construction according to the invention;
FIG. 4 shows the corresponding spectral lines for different tube voltages (60, 100, 140kV);
FIG. 5 is a diagram of a DR scene positioning operation interface;
FIG. 6 is a corresponding image of the 60kV tube voltage;
FIG. 7 is a corresponding image of 100kV tube voltage;
FIG. 8 is a corresponding image of 140kV tube voltage;
FIG. 9 is a body position and its corresponding image;
FIG. 10 is another body position and its corresponding image.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings in conjunction with the following detailed description. It should be understood that the description is intended to be exemplary only, and is not intended to limit the scope of the present invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.
The noun explains:
electron density distribution: electron density values per unit volume within a certain tissue.
Effective atomic number: the atomic number of an element is the number of protons within the atom of the element. However, since the living tissue is a mixture, the equivalent atomic number is obtained depending on the molecular composition of the tissue.
X-ray energy spectrum curve: the energy distribution of the X-ray emitted by the bulb. The maximum energy is generally determined by kV, reflecting the penetration energy of the radiation, and is measured by the quality of the radiation. The filtering material can absorb low-energy rays, so that the quality of the rays is hardened, the overall penetrating capacity is enhanced, and the absorbed dose of human tissues is reduced.
Shooting field: the X-ray exposure range is adjusted by the lead gates in the transverse direction and the longitudinal direction to ensure that the X-ray just covers the detected part, thereby avoiding other tissues from being unnecessarily irradiated by the X-ray.
The invention can be applied to human bodies, other animals, plants or other objects. The following description will be made in detail by taking a human body as an example.
The invention can be used for teaching of human tomography anatomy and CT image diagnosis; meanwhile, the method can be used for comparison reference of clinical diagnosis to replace the CT atlas of the existing paper edition; and can also be used for positioning evaluation of tumor radiotherapy or surgical treatment plan. It can also be used for small animals in various clinical studies.
In one embodiment, as shown in fig. 1, a method for generating a virtual digital DR image includes the following steps:
s01: constructing a DR digital object;
s02: constructing an X-ray energy spectrum curve emitted by the bulb tube;
s03: constructing a filtering material attenuation model;
s04: calculating the filtered X-ray energy spectrum;
s05: and calculating to obtain a virtual digital DR image by taking the DR digital object as a virtual scanning sample.
In another embodiment, the invention is an apparatus for simulating DR imaging principle and technology with high degree of freedom, which mainly comprises three linkage modules: an X-ray physical module, a DR imaging module and a DR technology module. The main advantages are: the imaging parameters can be set by simulating a real machine in the DR imaging module, the energy spectrum curve under the corresponding exposure condition can be displayed in real time in the X-ray physical module, the heat capacity and the exposure heat capacity of the current bulb tube, the radiation dose and other parameters are displayed in real time in the DR technical module, the 3D display technology is adopted in the DR technical module, the DR operating room environment is simulated, the human body position is set at high degree of freedom, corresponding position parameters can be returned to the DR imaging module, after an exposure button is clicked, non-simple image calling is performed, the DR imaging module can call a built-in digital human matrix containing human body physical information, imaging is simulated according to the position parameters, the process is consistent with the real machine real human imaging process, and in principle, corresponding images under different exposure parameters of different positions can be obtained. In the mode, students can give guidance to teachers or independently develop various operation experiments through computer terminals, and then combine related image cases to completely meet the batch and standardized teaching requirements; the mode can help students to understand the relationship between different imaging parameters and different operation positions, and can help students to establish a concept of dosage control due to the fact that the dosage under the current parameters can be displayed in real time, which is particularly important when people pay more and more attention to self health.
As shown in fig. 2, a DR virtual simulation instrument includes:
the DR digital object constructing module is used for constructing a DR digital object;
the X-ray parameter construction module is used for constructing an X-ray energy spectrum curve emitted by the bulb tube;
the filtering model building module is used for building a filtering material attenuation model;
the filtered X-ray parameter calculation module is used for calculating a filtered X-ray energy spectrum;
and the scene construction module is used for constructing equipment components and object models for DR (digital radiography) inspection, and setting corresponding motion ranges and motion control functions of the equipment components and the object models.
And the DR image calculation module is used for calculating to obtain a virtual digital DR image by taking the DR digital object as a virtual scanning sample.
The respective modules or steps of the above embodiments are described in detail below.
In a preferred embodiment, as shown in fig. 3, the method of constructing a DR digital object comprises the steps of:
s11: carrying out high-resolution isotropic tomography on a real object through dual-energy CT to obtain two groups of CT images with different energies, establishing a CT value matrix with a first energy and a CT value matrix with a second energy, and obtaining an electron density three-dimensional distribution matrix of each voxel of the object according to the CT value matrix with the first energy and the CT value matrix with the second energy;
s12: calculating an effective atomic number matrix according to the obtained electron density three-dimensional distribution matrix of the voxel;
s13: and calculating the electron density three-dimensional distribution matrix and the effective atomic number matrix of each voxel, and combining the electron density three-dimensional distribution matrix and the effective atomic number matrix with the three-dimensional space structure of the object to obtain a multi-dimensional matrix to obtain the DR digital object.
(1) Electron density matrix construction method
Applying clinical or industrial double-energy CT to human body or object to be scanned (other animal, plant or other object), making high-resolution isotropic tomographic scanning to obtain two groups of CT images with different energies, creating three-dimensional digital CT value matrix corresponding to different energies, and setting Hu H (i, j, k) and Hu L (i, j, k) are CT values at high energy (e.g., 140 kV) and low energy (e.g., 80 kV) at voxel (i, j, k), respectively. By applying the relational expression, the electron density rho corresponding to the human body or the object can be obtained e The three-dimensional distribution matrix of (a):
ΔHu(i、j、k)≡(1+α)Hu H (i、j、k)-αHu L (i、j、k)
α, a and b are weight parameters whose values are determined from experimental measurements of standard phantoms, as the usual example using a low voltage of 80kV and a high voltage of 140kV, α =0.778, a =0.997 and b =0.998.
(2) Effective atomic number matrix construction method
According to the relation μ = ρ e (σ τ +σ c )，σ τ ＝mE -n Z c ，σ c ＝ne -gE Z d ，σ τ Represents the scattering cross section of the photoelectric effect, σ c In the case of a Compton scattering cross section, at low voltages (below 150 kV), X-rays are scattered and absorbed inside a substance mainly by the influence of these two effects.
An equation relating to Z can be established:
μ(i、j、k)＝ρ e (i、j、k)(mE -n Z c +fe -gE Z d )
where m =22.3, n =3.302, c =4.62, d =0.939, f =0.672, g =0.00197 are parameters fitted according to experimental data, E is the weighted average energy of the X-ray energy spectrum calculated from the energy spectrum distribution, the size of the set of parameters is independent of the voltage combination at the time of dual-source CT acquisition, and has universality, and Z is the effective atomic number to be solved. Wherein, the energy spectrum distribution is obtained by programming according to related theoretical formulas.
From the relation Hu =1000 (μ - μ w)/μ w, the absorption coefficient μ (i, j, k) of a voxel (i, j, k) at the corresponding kV (e.g. 140 kV) can be calculated, wherein μ w corresponds to the absorption coefficient of water at kV, μ w w Can be obtained by
Is calculated, where ρ ew ＝3.343×10 23 e/cm 3 ，Z w ＝7.353。
Mu (i, j, k), mu w And solving the previous step to obtain rho e Substitution of (i, j, k) into μ (i, j, k) = ρ e (i、j、k)(aE -b Z c +fe -gE Z d )
The effective atomic number Z (i, j, k) at the corresponding voxel (i, j, k) can be solved.
In a preferred embodiment, the X-ray energy spectrum curve includes its quality (keV) and quantity (mAs) parameters, where keV determines the maximum energy of the X-ray photon and also reflects the maximum penetration (quality) of the X-ray, and mAS determines the intensity (quantity) of the X-ray. The X-ray energy spectrum of the X-ray generated by the bulb after inherent filtration (air and beryllium window) is included, and corresponding spectral lines of different tube voltages (60, 100 and 140kV) are shown in figure 4.
The method for constructing the X-ray energy spectrum curve emitted by the bulb tube comprises the following steps:
s21: after the accelerated electrons impact the rhenium-tungsten alloy target or the molybdenum target, the generated X-ray continuous energy spectrum is as follows:
wherein mAs is the product of the set tube current (mA) and the exposure time(s), e is the electron electric quantity, r is the focal distance, F w (E) For intrinsic filtering effectiveness, E is the accelerated electron energy, N (E) is the number of X photons for a certain energy interval,
for photon yield per roentgen, dE is the photon energy interval;
wherein the content of the first and second substances,
wherein the content of the first and second substances,
the mass energy conversion coefficient of the air; w is 33.97J/C, A is 0.000258C.
μ is a function of E, and for ease of calculation, after least squares fitting:
μ(E)＝a 1 +a 2 (E/100) -1.6 +a 3 (E/100) -2.7 +a 4 (E/100) -3.5 +a 5 (E/100) -4.5
wherein, a 1 -a 5 Are fitting coefficients.
S22: the characteristic energy spectrum of the generated X-ray is as follows:
wherein E is k The kth separated X-ray energy.
For the rhenium-tungsten alloy, the Ek energy and production ratio are respectively:
in a preferred embodiment, the filtering models include intrinsic or additive filtering models, each filter including a type of filtering material (including an effective atomic number Z and an electron density rou), a thickness of the material (uniform or non-uniform), and a shape of the material. Where the inherent filtration may be air, beryllium windows, etc., and the additional filtration may be aluminum, wedge filters, etc.
In a preferred embodiment, the method for calculating the filtered X-ray energy spectrum comprises:
s41: splitting the X-ray energy spectrum into n energy intervals, each energy interval being a source of single energy, i.e. a source of radiation of a single energy
Wherein, I i Representing the intensity of the ith interval X-ray energy, E i Representing the ith interval X-ray energy, E i-1 The energy of the (i-1) th interval X-ray is shown, and delta is a fixed value;
s42: and performing attenuation calculation on each single-energy ray source after passing through each filtering material, wherein the calculation formula is as follows:
wherein mu e To the attenuation coefficient, I i0 Is shown as I i D is the thickness of the filter material, mu e ＝μ p +μ c ，μ p Is the photoelectric attenuation coefficient mu p ＝K*rou e *lamda 3 *Z 3.05 /(hc) 3 ，μ c Is the Compton attenuation coefficient mu c ＝K*rou e *lamada*Z/hc，rou e For the electron density of the active material, lamda is the x-ray wavelength, Z is the effective atomic number, and h is the Planck constantC is the speed of light, K is the coefficient;
s43: energy spectrum superposition is carried out on all the rays output after the single energy attenuation, and the filtered X-ray energy spectrum is obtained
In a preferred embodiment, as shown in fig. 5, in the scene construction module, according to the spatial layout of the actual DR scan room, 3D modeling software is used to construct the X-ray tube, the beam splitter, the suspension frame, the scanning flat bed, the vertical flat panel detector, and other device components, and corresponding motion ranges and motion control functions are given to each component, including the horizontal and vertical opening and closing ranges of the beam splitter, the expansion and contraction of the suspension frame, the rotation of the tube in 3 directions, and the like; and 3D modeling software is adopted to construct a human body model, and the rotating and translating motion range and the motion control function of the joints of each part of the human body are endowed according to the actual motion function of each joint of the human body. The motion control function can be adjusted by a mouse control or a panel control button.
And constructing a space geometric model of the DR equipment and the human body positioning, wherein the space geometric model comprises a human body position, an inspection part and a three-dimensional space rotation angle.
The space geometric model of human body positioning comprises the product of three matrixes of inspection position data, a bulb tube X-ray radiation field and the space of a detector according to the body position of the human body; the human body part in the scene area rotates in a reasonable range through joints of all parts, and the detected matrixes in different body positions are obtained after the data matrix corresponding to the DR digital human body part rotates.
In a preferred embodiment, the scene construction module further comprises an image range calculation model and an object positioning calculation model.
And the image range calculation model is used for calculating the intersection of the X-ray irradiation range, the digital object range and the detector detection area range to serve as an effective exposure and detection area.
And the object positioning calculation model is used for respectively carrying out corresponding translation and rotation operations on the three-dimensional object data of the original position according to a series of joint rotation actions of object positioning operations in the scene.
In a preferred embodiment, in the virtual digital DR image obtained by calculation, the outgoing ray intensity distribution of each voxel irradiated in the filtered X-ray direction under different X-ray parameters and different filtering conditions of the DR digital human body matrix in different body positions is calculated, i.e. the DR image. The method specifically comprises the following steps:
s51: calculating the position of the space matrix of the corresponding part of the DR digital object in the light-beam device field; performing dot product calculation on the DR digital object and the field matrix;
s52: calculating a DR image range;
s53: according to the X-ray direction, according to the similarity proportion and the detector resolution ratio, performing interpolation, then projecting the interpolation layer by layer on the detector plane, accumulating the previous layer after each layer of data projection, and so on, and after all layers of projection are finished, according to the relational expression between the intensity I and the absorption coefficient u after the X-ray is incident on the object
Obtaining an expression of the discrete case as
Wherein, l is the ray penetration distance, N is the number of the separation units on the X-ray penetration path, I 0 And I is the X-ray intensity, μ, of the incident and emergent objects, respectively i The absorption coefficient of tissues with different unit lengths, and deltax is the unit length;
s54: and converting the X-ray intensity I of the emergent object into a brightness signal to obtain a virtual digital DR image. That is, the intensity I of the finally emitted X-rays is irradiated onto the detector unit at the corresponding position, and converted into a detector signal S, which is proportional to I. The signal S with different intensity formed by each detector unit is a DR image. The method for calculating the DR image range comprises the following steps:
a detector model is constructed, including the spatial resolution of the detector matrix (size of the detector cells) and the matrix size (number of detector cells = number transverse by number longitudinal, such as 1024 by 1024). And calculating the DR image area, namely performing point multiplication calculation between the light field of the light beam generator and the detector matrix to determine the calculation and display area of the DR image.
On the basis of one-time double-energy CT imaging, any DR image under different X-ray parameters, different radiation fields and different body positions can be given according to requirements.
For example, fig. 6 is a corresponding image of a 60kV tube voltage, fig. 7 is a corresponding image of a 100kV tube voltage, and fig. 8 is a corresponding image of a 140kV tube voltage.
FIG. 9 shows a body position and its corresponding image, and FIG. 10 shows another body position and its corresponding image.
It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explaining the principles of the invention and are not to be construed as limiting the invention. Therefore, any modification, equivalent replacement, improvement and the like made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. Further, it is intended that the appended claims cover all such variations and modifications as fall within the scope and boundaries of the appended claims or the equivalents of such scope and boundaries.
Claims (8)
1. A method for generating a virtual digital DR image, comprising the steps of:
s01: constructing a DR digital object;
s02: constructing an X-ray energy spectrum curve emitted by the bulb tube, comprising the following steps:
s21: after the accelerated electrons impact the rhenium-tungsten alloy target or the molybdenum target, the generated X-ray continuous energy spectrum is as follows:
wherein the content of the first and second substances,mAsin order to set the product of the tube current mA and the exposure time s, e is the electronic quantity, r is the focal distance,
for intrinsic filtering effect, E is an accelerated electronThe energy of the gas is converted into the energy,
the number of X-photons for a certain energy interval,
for the photon yield per roentgen,dEis a photon energy interval;
s22: the resulting X-ray characteristic spectrum is:
wherein the content of the first and second substances,
is the kth separated X-ray energy;
s03: constructing a filtering material attenuation model;
s04: calculating the filtered X-ray energy spectrum;
s05: and calculating to obtain a virtual digital DR image by taking the DR digital object as a virtual scanning sample.
2. The method of generating a virtual digital DR image according to claim 1 wherein said step S01 of constructing a DR digital object comprises the steps of:
s11: carrying out high-resolution isotropic tomography on a real object through dual-energy CT to obtain two groups of CT images with different energies, establishing a CT value matrix with a first energy and a CT value matrix with a second energy, and obtaining an electron density three-dimensional distribution matrix of each voxel of the object according to the CT value matrix with the first energy and the CT value matrix with the second energy;
s12: calculating an effective atomic number matrix according to the obtained electron density three-dimensional distribution matrix of the voxel;
s13: and calculating the electron density three-dimensional distribution matrix and the effective atomic number matrix of each voxel, and combining the electron density three-dimensional distribution matrix and the effective atomic number matrix with the three-dimensional space structure of the object to obtain a multi-dimensional matrix to obtain the DR digital object.
3. The method of generating a virtual digital DR image as recited in claim 1, wherein the filtering model in the step S03 comprises an intrinsic filtering model or an additional filtering model, and each filtering model comprises a filtering material type, a material thickness, and a material shape.
4. The method of generating a virtual digital DR image of claim 1 wherein said step S04 of calculating a filtered X-ray energy spectrum method comprises:
s41: splitting the X-ray energy spectrum into n energy intervals, each energy interval being a source of single energy, i.e. a source of radiation of a single energy
， 
Wherein, I i Representing the intensity of the ith interval X-ray energy, E i Representing the ith interval X-ray energy, E i-1 The energy of the (i-1) th interval X-ray is shown, and delta is a fixed value;
s42: and performing attenuation calculation on each single-energy ray source after passing through each filtering material, wherein the calculation formula is as follows:
wherein
To the attenuation coefficient, I i0 Is I i D is the thickness of the filtered material,
，
as photoelectric attenuation coefficient
，
Is the Compton attenuation coefficient
，rou e As the electron density of the active species,lamdais the x-ray wavelength, Z is the effective atomic number, h is the Planck constant, c is the speed of light, and K is the coefficient;
s43: performing energy spectrum superposition on all the rays output after single energy attenuation to obtain a filtered X-ray energy spectrum
。
5. The method of claim 1, wherein the step S05 of calculating the virtual digital DR image comprises:
s51: calculating the position of the spatial matrix of the corresponding part of the DR digital object in the field of the beam splitter;
s52: calculating a DR image range;
s53: according to the X-ray direction, according to the similarity proportion and the detector resolution ratio, performing interpolation, projecting the interpolation layer by layer onto the detector plane, accumulating the previous layer after each layer of data projection, and so on, and after all layers of projection are finished, according to the intensity of the X-ray incident object𝐈And absorption coefficient
Relation between them
Obtain an expression of the discrete case as
Wherein, in the step (A),lis the ray penetration distance, N is the number of separation units on the X-ray penetration path, I 0 And I is the X-ray intensity of the incident and exiting object respectively,µ i the absorption coefficient of tissues with different unit lengths, and deltax is the unit length;
s54: intensity of X-ray emitted from object𝐈And converting the digital image into a brightness signal to obtain a virtual digital DR image.
6. A DR virtual simulation instrument, comprising:
the DR digital object constructing module is used for constructing a DR digital object;
the X-ray parameter construction module is used for constructing an X-ray energy spectrum curve emitted by the bulb tube, and the method comprises the following steps:
s21: after the accelerated electrons impact the rhenium-tungsten alloy target or the molybdenum target, the generated X-ray continuous energy spectrum is as follows:
wherein mAs is the product of the set tube current mA and the exposure time s, e is the electronic quantity, r is the focal distance,
for intrinsic filtering effectiveness, E is the accelerated electron energy,
the number of X-photons for a certain energy interval,
for the photon yield per roentgen,dEis a photon energy interval;
s22: the resulting X-ray characteristic spectrum is:
wherein the content of the first and second substances,
is the kth separated X-ray energy;
the filtering model building module is used for building a filtering material attenuation model;
the filtered X-ray parameter calculation module is used for calculating a filtered X-ray energy spectrum;
the scene construction module is used for constructing equipment parts and object models for DR (digital radiography) inspection, and setting corresponding motion ranges and motion control functions of the equipment parts and the object models;
and the DR image calculation module is used for calculating to obtain a virtual digital DR image by taking the DR digital object as a virtual scanning sample.
7. The DR virtual simulation instrument of claim 6, wherein the method of calculating the filtered X-ray energy spectrum in the filtered X-ray parameter calculation module comprises:
s41: splitting the X-ray energy spectrum into n energy intervals, each energy interval being a source of single energy, i.e. a source of radiation of a single energy
， 
Wherein, I i Representing the intensity of the ith interval X-ray energy, E i Representing the ith interval X-ray energy, E i-1 The energy of the X-ray at the interval i-1 is a fixed value;
s42: and performing attenuation calculation on each single-energy ray source after passing through each filtering material, wherein the calculation formula is as follows:
in which
To the attenuation coefficient, I i0 Is I i D is the thickness of the filtered material,
，
as photoelectric attenuation coefficient
，
Is the Compton attenuation coefficient
，rou e As the electron density of the active species,lamdais the x-ray wavelength, Z is the effective atomic number, h is the Planck constant, c is the speed of light, K is the coefficient;
s43: performing energy spectrum superposition on all the rays output after single energy attenuation to obtain a filtered X-ray energy spectrum
。
8. The DR virtual simulation instrument of claim 6, wherein the scene construction module further comprises an image range calculation model and an object placement calculation model, wherein the image range calculation model calculates an intersection of an X-ray irradiation range, a digital object range and a detector detection area range as effective exposure and detection areas; the object positioning calculation model respectively carries out corresponding translation and rotation operations on the three-dimensional object data according to a series of joint rotation actions of object positioning operations in a scene on the three-dimensional object data at an original position.
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