Lung respiration simulation device for radiotherapy and three-dimensional dose distribution acquisition method for lung respiration simulation device

Abstract

The invention relates to a pulmonary respiration simulation device for radiotherapy and a three-dimensional dose distribution acquisition method for the device. The main control module of the simulation device collects flux distribution in real time through the electronic detector, constructs a three-dimensional model of the body surface of the biological in-vitro lung through the detection module, and inflates or inhales the biological in-vitro lung through the driving assembly. The three-dimensional dose distribution acquisition method comprises the following steps: acquiring perspective flux distribution in real time; calculating incident flux distribution P1; carrying out reverse deduction on the incident flux distribution P1 to obtain incident flux distribution P2; carrying out repeated iterative optimization on the incident flux distribution P1 and the incident flux distribution P2 to obtain incident flux distribution Pn; and reconstructing the three-dimensional dose distribution in the biological in-vitro lung body. The beneficial effects are that breathing of a lung cancer patient can be simulated, and three-dimensional dose distribution in a biological in-vitro lung body can be accurately acquired in real time for dose verification in radiotherapy, so that the lung cancer radiotherapy effect is improved.

Description

Technical Field

[0001] The present invention relates to the field of medical simulation technology, and in particular to a lung respiration simulation device for radiotherapy and a method for obtaining three-dimensional dose distribution for this device. Background Art

[0002] One of the core challenges in lung cancer radiotherapy is that the dose distribution in the radiotherapy plan is calculated based on a certain static respiratory phase when the patient is CT-simulated and positioned. However, in actual treatment, the lung tumor continuously displaces with respiratory movement and it is difficult to continuously stay in the expected dose area. This not only may weaken the treatment effect, but also may increase the risk of healthy tissues being accidentally exposed to high radiation. To solve this problem, accurately capturing the dynamic position information of the tumor has become the key, which has promoted the development of various monitoring technologies. However, the existing technologies lack sufficient theoretical and experimental verification and there are risks in directly applying them to clinical practice. Therefore, constructing a model highly similar to the human body to comprehensively simulate the complex situations in the real treatment environment is crucial for verifying the clinical applicability and accuracy of these technologies. However, traditional mechanical models can simulate the physical characteristics of respiratory movement but are difficult to reproduce the authenticity and complexity of biological tissues; biological models are closer to the physiological state but often difficult to accurately match the respiratory characteristics of specific patients. More importantly, both mechanical models and biological models are mostly limited to exploring tumor movement at the theoretical level and have not fully involved in in-vivo dose verification during the actual treatment process. The current mainstream dose verification devices all belong to rigid body verification, cannot truly reflect the movement characteristics of biological tissues, especially the patient's respiratory movement, and can only be verified before treatment, unable to measure and verify the actual impact of respiratory movement on dose distribution in real time and accurately. Summary of the Invention

[0003] The technical problem to be solved by the present invention is: to provide a lung respiration simulation device for radiotherapy that can achieve highly customized simulation of the individual respiratory characteristics of patients, and also provide a method for obtaining three-dimensional dose distribution for this device that can obtain the three-dimensional dose distribution in the ex-vivo lung in real time.

[0004] The technical solution adopted by the present invention to solve its technical problems is: a lung respiration simulation device for radiotherapy, including an ex-vivo lung, an electronic detector, a detection module, a main control module, and a driving assembly. The ex-vivo lung is used to simulate the human lung. The main control module is connected to the electronic detector, the detection module, and the driving assembly. The driving assembly is connected to the ex-vivo lung. The main control module collects the flux distribution in real time through the electronic detector after radiotherapy rays pass through the ex-vivo lung. The main control module captures the deformation of the lung body surface in real time through the detection module and constructs a three-dimensional model of the ex-vivo lung body surface. The main control module inflates or inhales the ex-vivo lung through the driving assembly to make the ex-vivo lung contract or expand to simulate the respiratory state of the human lung.

[0005] In some embodiments, optionally, the radiotherapy lung respiration simulation device further includes an elastic container for simulating the human chest and abdomen. The driving assembly is connected to the elastic container. The main control module synchronously inflates or inhales the ex vivo lung and the elastic container through the driving assembly, so that the ex vivo lung and the elastic container contract or expand synchronously to mimic the undulating state of the human chest and abdomen.

[0006] In some embodiments, optionally, the driving assembly includes a driving bracket, a driving module, a pressing module, and a balloon. The driving module, the pressing module, and the balloon are mounted on the driving bracket. The main control module is connected to the driving module, the driving module is connected to the pressing module, and there are two balloons. The two balloons are respectively connected to the ex vivo lung and the elastic container through tracheas. The main control module generates a pulse signal according to the amplitude and period of the human respiration curve and transmits the pulse signal to the driving module. The driving module controls the forward and backward movement of the pressing module according to the frequency and quantity of the pulse signal, and synchronously presses or stretches the two balloons, so that the balloons synchronously inflate or inhale the ex vivo lung and the elastic container.

[0007] In some embodiments, optionally, the detection module includes an optical ranging detector, a pressure sensor, and a data automatic collector. The pressure sensor is used to be tied to the human chest and abdomen to detect the period of the human respiration curve. The optical ranging detector is used to be arranged above the ex vivo lung to capture the surface deformation of the lung in real time and construct a three-dimensional model of the ex vivo lung surface. The optical ranging detector is also used to be arranged above the human chest and abdomen to detect the amplitude of the human respiration curve. The main control module is connected to the data automatic collector, and the data automatic collector is respectively connected to the optical ranging detector and the pressure sensor. The main control module receives the detection data of the optical ranging detector and the pressure sensor through the data automatic collector.

[0008] In some embodiments, optionally, the optical ranging detector is specifically a laser ranging detector. The laser ranging detector is used to capture the surface deformation of the lung in real time and construct a three-dimensional model of the ex vivo lung surface by emitting and receiving laser three-dimensional point clouds, or to detect the amplitude of the human respiration curve.

[0009] In some embodiments, optionally, a hydrogel simulating a tumor is injected into the ex vivo lung.

[0010] In some embodiments, optionally, the driving module includes a motor and a lead screw. The lead screw is connected to the output end of the motor. A slider is arranged on the lead screw. The slider moves forward or backward as the lead screw rotates. The pressing module is mounted on the slider and moves forward or backward with the slider. The pressing module is a U-shaped fork. The fork feet of the U-shaped fork are respectively aligned with two storage balloons. The motor adjusts the rotation speed and direction according to the frequency and quantity of the pulse signal. A front limit sensor and a rear limit sensor are respectively mounted on the front part and the rear part of the lead screw. Both the front limit sensor and the rear limit sensor are electrically connected to the main control module and are used for limiting the maximum stroke in the front and rear directions.

[0011] In some embodiments, optionally, the electronic detector is an electronic portal imaging device, and the electronic detector is arranged below the ex vivo lung.

[0012] A method for obtaining a three-dimensional dose distribution of the above-mentioned lung respiration simulation device for radiotherapy includes the following steps: A) Real-time collect the flux distribution after the radiotherapy ray passes through the ex vivo lung through the electronic detector below the ex vivo lung. This flux distribution is called the fluoroscopic flux distribution; B) Map the fluoroscopic flux distribution onto the three-dimensional model of the surface of the ex vivo lung captured in real time to obtain a three-dimensional transmitted flux distribution. Use ray tracing technology to restore the specific path of the radiotherapy ray from the radiation source to the surface of the ex vivo lung. Based on the three-dimensional transmitted flux distribution and the specific path, calculate the flux distribution before the radiotherapy ray enters the ex vivo lung according to the energy deposition per unit mass of the primary ray and the flux distribution kernel. This flux distribution is called the incident flux distribution P1; C) Based on the exponential attenuation law of the radiotherapy ray, directly inversely deduce the incident flux distribution P2 from the incident flux distribution P1; D) Perform multiple iterative optimizations on the incident flux distribution P1 and the incident flux distribution P2 to obtain the optimized incident flux distribution Pn; E) Perform real-time dynamic correction on the incident flux distribution Pn using the biological deformation registration algorithm, map the corrected measurement results to a unified reference coordinate system. Subsequently, use the Monte Carlo algorithm in the unified reference coordinate system to simulate the transmission process of photons in the radiotherapy ray in an inhomogeneous medium, apply specific biological tissue-dose conversion factors and correction coefficients in combination with the 4DCT images of the ex vivo lung, and convert the incident flux distribution Pn into the actual absorbed dose distribution to reconstruct the three-dimensional dose distribution in the ex vivo lung.

[0013] In some embodiments, optionally, in step A, perform deconvolution processing on the signal collected in real time by the electronic detector to obtain the flux distribution after the radiotherapy ray passes through the ex vivo lung.

[0014] In some embodiments, optionally, in step D, the specific process of multiple iterative optimizations is as follows: compare the incident flux distribution P1 and the incident flux distribution P2 to obtain a residual, reverse the residual to obtain a correction amount for the incident flux distribution P2, and update the incident flux distribution P2 in combination with a relaxation factor to ensure non-negativity constraints. Stop updating when the difference between the incident flux distribution P1 and the incident flux distribution P2 is less than a threshold. At this time, output the incident flux distribution Pn after iterative optimization.

[0015] The beneficial effects of the present invention are as follows: Currently, in-vivo dose verification methods mainly evaluate the actually emitted radiation dose, which belongs to post-event evaluation and cannot prevent problems before they occur. Moreover, this verification method is still limited by factors such as patient individual differences and physiological activity interference. Especially for the target areas in the chest and abdominal pelvic regions, it is easily affected by physiological changes such as respiratory movement, gastrointestinal peristalsis, and bladder filling, resulting in the actual dose deviating from the planned dose.

[0016] The lung respiration simulation device for radiotherapy of the present invention can accurately quantify and simulate the respiration patterns of lung cancer patients, such as irregular respirations like coughing, deep breathing, and moist breathing. The respiration patterns are very rich and are used for real-time in-vivo biological dose distribution verification during radiotherapy. Real-time in-vivo biological dose distribution verification not only overcomes the difficult-to-control physiological variables in actual patient treatment but also opens up a new path for achieving more accurate and personalized radiotherapy dose verification.

[0017] In the prior art, the dose verification model obtains the three-dimensional dose distribution within the model through multiple built-in dose sensors. However, it is impossible to install dose sensors inside the moving ex-vivo lung to obtain the three-dimensional dose distribution within the biological model.

[0018] The method for obtaining the three-dimensional dose distribution of the present invention can accurately and real-time obtain the three-dimensional dose distribution within the ex-vivo lung body, which is used to accurately quantify the difference between the actual dose and the planned dose, thereby providing strong technical support for improving the radiotherapy effect of lung cancer and reducing normal tissue damage. Brief Description of the Drawings

[0019] The present invention will be further described below in conjunction with the drawings and embodiments; Figure 1 is a schematic diagram of the main structure of the lung respiration simulation device for radiotherapy of the present invention; Figure 2 is a schematic diagram of detecting the amplitude of the respiration curve of the human body by the laser ranging detector of the detection module of the invention; Figure 3 is a schematic diagram of performing radiotherapy by the lung respiration simulation device for radiotherapy of the present invention; In the figure: 1. Laser ranging detector, 2. Pressure sensor, 3. Chest and abdomen, 4. Data automatic collector, 5. Main control module, 6. Driving bracket, 7. Motor, 8. Lead screw, 9. Slide block, 10. U-shaped fork, 11. Pagoda adapter, 12. Storage balloon, 13. Air tube, 14. Ex vivo lung, 15. Elastic container, 16. Front limit sensor, 17. Rear limit sensor, 18. Electronic portal imaging device. Detailed implementation mode

[0020] As Figures 1 - 3 A lung respiration simulation device for radiotherapy as shown includes an ex vivo lung 14, an elastic container 15, an electronic detector, a detection module, a main control module 5 and a driving assembly. The ex vivo lung 14 is used to simulate the human lung, and the elastic container 15 is used to simulate the chest and abdomen 3 of a human. The main control module 5 is connected to the electronic detector, the detection module and the driving assembly. The driving assembly is connected to the ex vivo lung 14 and the elastic container 15. The electronic detector is arranged below the ex vivo lung 14. The main control module 5 collects the flux distribution in real time through the electronic detector after the radiotherapy ray passes through the ex vivo lung 14. The main control module 5 captures the deformation of the lung body surface in real time through the detection module and constructs a three-dimensional model of the surface of the ex vivo lung 14. The main control module 5 synchronously inflates or inhales the ex vivo lung 14 and the elastic container 15 through the driving assembly, so that the ex vivo lung 14 and the elastic container 15 contract or expand synchronously to simulate the breathing state of the human lung and the undulating state of the chest and abdomen 3 of a human. The ex vivo lung 14 is preferably a pig lung close to the human lung.

[0021] Dose verification is divided into pre-treatment verification and in-treatment verification. Pre-treatment verification is non-real-time verification, and in-treatment verification is real-time verification. Pre-treatment verification is non-in-vivo verification, and in-treatment verification is in-vivo verification. Currently, the dose verification methods adopted clinically are all pre-treatment, non-real-time, and non-in-vivo dose verification methods, because in-treatment verification really requires a real patient for measurement. If problems are found, they cannot be corrected because the radiotherapy machine cannot be stopped during treatment.

[0022] This lung respiration simulation device for radiotherapy can not only be used to replace real patients for dose verification, but also be used for radiotherapy experimental research such as studying the influence of respiratory movement on the radiotherapy treatment effect.

[0023] Currently, the verification model for dose verification adopted clinically is a non-dynamic and rigid mold. The verification model of this solution is dynamic. The ex vivo lung 14 is preferably a pig lung close to the human lung, and the simulation is more realistic.

[0024] The drive assembly includes a drive bracket 6, a drive module, a pressing module, and a storage balloon 12. The drive module, the pressing module, and the storage balloon 12 are installed on the drive bracket 6. The main control module 5 is connected to the drive module, the drive module is connected to the pressing module. There are two storage balloons 12, and the two storage balloons 12 are respectively connected to the ex vivo lung 14 and the elastic container 15 through air pipes 13. The main control module 5 generates a pulse signal according to the amplitude and period of the human respiratory curve, and transmits the pulse signal to the drive module. The drive module controls the forward and backward movement of the pressing module according to the frequency and quantity of the pulse signal, and synchronously presses or stretches the two storage balloons 12, so that the storage balloons 12 synchronously inflate or inhale air into the ex vivo lung 14 and the elastic container 15.

[0025] The drive module includes a motor 7 and a lead screw 8. The lead screw 8 is connected to the output end of the motor 7. A slider 9 is arranged on the lead screw 8, and the slider 9 moves forward or backward as the lead screw 8 rotates. The pressing module is installed on the slider 9 and moves forward or backward with the slider 9. The pressing module is a U-shaped fork 10, and the fork feet of the U-shaped fork 10 are respectively aligned with the two storage balloons 12. The motor 7 adjusts the rotation speed and direction according to the frequency and quantity of the pulse signal. A front limit sensor 16 and a rear limit sensor 17 are respectively installed at the front and rear parts of the lead screw 8. The front limit sensor 16 and the rear limit sensor 17 are both electrically connected to the main control module 5 and are used for maximum stroke limit in the front and rear directions to avoid damaging this device due to misoperation.

[0026] The motor 7 is preferably a stepping motor. The air pipe 13 is preferably a silica gel hose. The storage balloon 12 is a storage balloon 12 made of polyvinyl chloride material, and the elastic container 15 is an inflatable elastic container 15 made of rubber. The storage balloon 12 is connected to the air pipe 13 using a pagoda adapter 11.

[0027] The detection module includes an optical ranging detector, a pressure sensor 2, and a data automatic collector 4. The pressure sensor 2 is used to be tied to the chest and abdomen 3 of the human body to detect the period of the human respiratory curve. The optical ranging detector is used to be arranged above the ex vivo lung 14 to capture the surface deformation of the lung in real time and construct a three-dimensional model of the surface of the ex vivo lung 14. The optical ranging detector is also used to be arranged above the chest and abdomen 3 of the human body to detect the amplitude of the human respiratory curve. The main control module 5 is connected to the data automatic collector 4, and the data automatic collector 4 is respectively connected to the optical ranging detector and the pressure sensor 2. The main control module 5 receives the detection data of the optical ranging detector and the pressure sensor 2 through the data automatic collector 4.

[0028] At Figure 1 and 3In the embodiment, the laser range finder 1 of the present invention is installed by a bracket mounted on the treatment bed, and the automatic data collector 4 is installed on the side of the bracket. The pressure sensor 2 is specifically a bandage pressure sensor, and the bandage pressure sensor provided by the CT positioning machine can be directly used.

[0029] The optical ranging detector is specifically a laser ranging detector 1, which is used to capture the lung surface deformation in real time by emitting and receiving laser three-dimensional point clouds, construct a three-dimensional model of the biological ex vivo lung 14 surface, or detect the amplitude of the human body's breathing curve.

[0030] The ex vivo lung 14 is infused with a hydrogel that simulates a tumor.

[0031] The specific process of simulating the patient's tumor and breathing curve using the above-mentioned radiotherapy lung breathing simulation device is as follows: The program of the main control module 5 is written based on Arduino-1.8.19. By adjusting the parameters in the for loop function, the number of forward and reverse rotations of the motor 7 is set to control the volume of the gas pressed out of the balloon 12 to match the amplitude of the patient's breathing curve. The parameters in the delayMicroseconds function are adjusted to set the delay time of the high level and the low level to change the rotation speed of the motor 7 to match the period of the breathing curve. The parameters in the delay function are adjusted to set the switching time between the forward and reverse rotation of the motor 7 to match the time of the patient's breathing pause. After the program is compiled, the main control chip in the main control module 5 is imported. The main control chip is a high-performance ATmega328P-PU circuit board. The internal picoPower 8-bit AVR microcontroller is used to calculate and generate pulse signals, and the generated pulse signals are transmitted to the driver module 6. The driver module 6 accurately controls the speed and direction of the motor 7 according to the frequency and number of the pulse signals to achieve the reproduction of the patient's breathing curve.

[0032] A 10% polyvinyl alcohol solution was injected into an isolated lung 14 through a bronchoscope, followed by a resveratrol ethanol solution, which was mixed to form a hydrogel, which was regarded as a tumor mimic.

[0033] The motor 7 of the lung breathing simulation device for radiotherapy is installed at the front end of the screw 8 with a diameter of 16mm and a pitch of 5mm. The motor 7 rotates one circle to drive the screw 8 to rotate one circle, and the slider 9 on the screw 8 moves linearly by 5mm, and the U-shaped fork 10 installed on the slider 9 also moves linearly by 5mm. Under the operation of the motor 7, the U-shaped fork 10 on the slider 9 presses and stretches the balloon 12, so that the balloon 12 synchronously inflates or inhales the biological isolated lung 14 and the elastic container 15, driving the synchronous expansion and contraction of the biological isolated lung 14 and the elastic container 15.

[0034] Specifically, the motor 7 rotates forward 10 turns, causing the U-shaped fork 10 to push forward 50 mm and squeeze the storage balloon 12. The gas in the storage balloon 12 is compressed and blown out 500 ml, and enters the ex vivo lung 14 through the ventilation pipe 13, causing the ex vivo lung 14 to expand, simulating the inhalation state of the human lung. At the same time, the other fork foot of the U-shaped fork 10 also pushes another storage balloon 12, causing the gas in the storage balloon 12 to enter the elastic container 15, causing it to expand, simulating the bulging of the chest and abdomen 3 of the human body; After the forward rotation of the motor 7 ends, it pauses for 500 ms, simulating the pause at the end of human inhalation. Then the motor 7 rotates backward 10 turns, causing the U-shaped fork 10 to retreat 50 mm. The gas originally pressed into the ex vivo lung 14 and the elastic container 15 flows back into the storage balloon 12. The ex vivo lung 14 contracts, simulating the exhalation state of the human lung. At the same time, the elastic container 15 also contracts, simulating the contraction of the chest and abdomen 3 of the human body; Repeat the above process to simulate the breathing state of the human lung.

[0035] In this solution, the ex vivo lung 14, that is, the pig lung, will be pre-filled with gas at the beginning, so that its outer contour is consistent with the amplitude of the human chest, starting from the exhalation state of the human lung as the initial state. The elastic container 15 is also pre-filled with gas, so that its outer contour is consistent with the amplitude of the human chest.

[0036] For each turn of the motor 7, the volume of the balloon also changes linearly, that is, the advancing or stretching distance is fixed. The elastic behavior of the pig lung can be approximated by a linear spring model. The air flow resistance is proportional to the pressure difference and the flow rate. The influence of environmental factors such as temperature and humidity on the properties of the gas is ignored. The following function expression can describe the relationship between the rotation of the motor 7 and the breathing amplitude of the pig lung: Among them, k elastic represents the elastic coefficient of the pig lung; β is a proportionality coefficient; V balloon represents the volume of the balloon; V min represents the volume of the pig lung after complete exhalation; V lung represents the maximum volume of the pig lung; N represents the number of turns of the motor 7; L represents the advancing or stretching distance of the storage balloon 12 for each turn of the motor 7.

[0037] The electronic detector is the electronic portal imaging device 18, and the electronic portal imaging device 18 is the EPID. In Figure 3 , the electronic portal imaging device 18 is specifically located on the back of the treatment couch.

[0038] This radiotherapy lung breathing simulation device is powered by a main power supply.

[0039] As shown Figure 3 in the figure, a method for obtaining a three-dimensional dose distribution of the above-mentioned lung respiration simulation device for radiotherapy includes the following steps: A) The flux distribution after the radiotherapy ray passes through the ex vivo lung 14 is collected in real time by an electronic detector below the ex vivo lung 14, and this flux distribution is called the perspective flux distribution.

[0040] In step A, the signal collected in real time by the electronic detector is deconvolved to obtain the flux distribution after the radiotherapy ray passes through the ex vivo lung 14.

[0041] The radiation source of the radiotherapy device emits radiotherapy rays as high-energy X-rays, which will interact with the porcine lung when penetrating it. When X-rays leave the radiation source and enter the air or medium, they begin to spread and form a field scatter, which can describe the intensity and distribution of X-rays in space. The electronic detector, i.e., EPID, located below the porcine lung can receive the photons scattered from the inside of the porcine lung. These photons form a Gaussian distribution pattern on the surface of the EPID. Since the signal received by the EPID contains the superposition effect of scattered photons and the original radiation beam, deconvolution calculation is required to separate them and remove the influence of scattered photons. After deconvolution calculation, the signal received by the EPID can be converted into the flux distribution after passing through the porcine lung.

[0042] B) Map the perspective flux distribution onto the three-dimensional model of the surface of the ex vivo lung 14 captured in real time to obtain the three-dimensional transmitted flux distribution. The ray tracing technique is used to restore the specific path of the radiotherapy ray from the radiation source to the surface of the ex vivo lung 14. Based on the three-dimensional transmitted flux distribution and the specific path, the flux distribution before the radiotherapy ray enters the ex vivo lung 14 is calculated according to the energy deposition of the primary ray per unit mass and the flux distribution kernel. This flux distribution is called the incident flux distribution P1.

[0043] C) Assume that all of the incident flux distribution P1 calculated above comes from the direct contribution of the radiation source, and directly inversely deduce the incident flux distribution P2 based on the exponential attenuation law of the radiotherapy ray through the incident flux distribution P1.

[0044] D) Iteratively optimize the incident flux distribution P1 and the incident flux distribution P2 multiple times to obtain the optimized incident flux distribution Pn.

[0045] In step D, the specific process of multiple iterative optimizations is as follows: Compare the incident flux distribution P1 and the incident flux distribution P2 to obtain the residual. Inversely deduce the correction amount of the incident flux distribution P2 from the residual, and update the incident flux distribution P2 in combination with the relaxation factor to ensure non-negativity constraints. Stop updating when the difference between the incident flux distribution P1 and the incident flux distribution P2 is less than the threshold. At this time, output the iteratively optimized incident flux distribution Pn.

[0046] E) Considering the organ movement caused by breathing, the incident flux distribution Pn is corrected in real time by using a biological deformation registration algorithm, and the corrected measurement results are mapped to a unified reference coordinate system. Subsequently, within the unified reference coordinate system, the Monte Carlo algorithm is used to simulate the transmission process of photons in the radiotherapy beam in a heterogeneous medium. By applying specific biological tissue-dose conversion factors and correction coefficients and combining with the 4DCT images of the ex vivo lung 14, the incident flux distribution Pn is converted into the actual absorbed dose distribution, and the three-dimensional dose distribution in the ex vivo lung 14 is reconstructed.

[0047] A method for real-time in-vivo dose verification of a biological object using the above-mentioned lung breathing simulation device for radiotherapy, comprises the following steps: I. During the radiotherapy plan design stage, 4DCT images of the patient, i.e., four-dimensional computed tomography images, are acquired, and the amplitude and period of the patient's breathing curve are detected by the laser distance detector 1, the strap-on pressure sensor, and the data automatic collector 4 of the detection module of the above-mentioned lung breathing simulation device for radiotherapy.

[0048] Specifically: The patient is scanned using a Philips large-bore Brilliance Big Bore CT locator to obtain 4DCT images of the lungs.

[0049] During the scanning process, the strap-on pressure sensor tied to the patient's chest and abdomen 3 captures the undulation signal of the patient's chest and abdomen 3, realizing the detection of the period of the human breathing curve.

[0050] However, the pressure sensor 2 can only obtain the period of the breathing curve and cannot obtain the amplitude of the breathing curve. Therefore, during the scanning process, the laser distance detector 1 of the detection module continuously sends laser pulses to the patient's chest and abdomen 3, and thus a lot of distances are measured. Within one period, the maximum distance minus the minimum distance is the amplitude of human breathing.

[0051] II. Using the above-mentioned lung breathing simulation device for radiotherapy to simulate the tumor and breathing curve of the patient and perform radiotherapy according to the radiotherapy plan for real-time in-vivo dose verification of the biological object.

[0052] During radiotherapy, the three-dimensional dose distribution in the ex vivo lung 14 is obtained by the above-mentioned three-dimensional dose distribution acquisition method. The difference between this three-dimensional dose distribution and the dose distribution in the Monaco treatment planning system (version 5.40.02; Elekta Instrument AB, Stockholm, Sweden) is quantified by calculating the gamma passing rate. Based on these difference analyses, the radiotherapy plan is adjusted quickly and accurately to ensure that the treatment plan is more suitable for the actual situation of the patient.

[0053] During the CT positioning machine in the radiotherapy plan design stage and the radiotherapy equipment in the radiotherapy stage are working, the self - carried strap - type pressure sensor needs to be strapped to the chest and abdomen 3 of the patient, and only when the breathing fluctuations of the chest and abdomen 3 are detected can they start working. The elastic container 15 of the lung respiration simulation device for radiotherapy in this solution is used to simulate the breathing movement of the chest and abdomen 3 of a person, enabling the CT positioning machine and the radiotherapy equipment in the radiotherapy stage to start working.

Claims

1. A lung breathing simulation device for radiotherapy, characterized in that: The system comprises a biological isolated lung, an electronic detector, a detection module, a main control module and a drive assembly. The biological isolated lung is used to simulate a human lung. The main control module is connected to the electronic detector, the detection module and the drive assembly. The drive assembly is connected to the biological isolated lung. The main control module collects the flux distribution of radiotherapy rays after passing through the biological isolated lung in real time through the electronic detector. The main control module captures the deformation of the lung surface in real time through the detection module to construct a three-dimensional model of the biological isolated lung surface. The main control module inflates or inhales the biological isolated lung through the drive assembly to shrink or expand the biological isolated lung to simulate the breathing state of the human lung.

2. The lung breathing simulation device for radiotherapy according to claim 1, characterized in that: It also includes an elastic container, which is used to simulate the chest and abdomen of a person. The driving assembly is connected to the elastic container. The main control module inflates or inhales air into the biological ex vivo lung and the elastic container synchronously through the driving assembly, so that the biological ex vivo lung and the elastic container contract or expand synchronously to simulate the ups and downs of the chest and abdomen of a person.

3. The lung breathing simulation device for radiotherapy according to claim 2, characterized in that: The driving assembly includes a driving bracket, a driving module, a pressing module and a balloon storage balloon, which are mounted on the driving bracket, the main control module is connected to the driving module, which is connected to the pressing module, there are two balloon storage balloons, which are respectively connected to the biological ex vivo lung and the elastic container through the trachea, the main control module generates a pulse signal according to the amplitude and period of the human body's breathing curve, and transmits the pulse signal to the driving module, the driving module controls the forward and backward movement of the pressing module according to the frequency and quantity of the pulse signal, synchronously presses or stretches the two balloon storage balloons, so that the balloon storage balloons synchronously inflate or inhale the biological ex vivo lung and the elastic container.

4. The lung breathing simulation device for radiotherapy according to claim 2, characterized in that: The detection module includes an optical ranging detector, a pressure sensor and an automatic data collector. The pressure sensor is used to be tied to the chest and abdomen of a human body to detect the period of the human body's breathing curve. The optical ranging detector is used to be set above the biological ex vivo lung to capture the deformation of the lung surface in real time and build a three-dimensional model of the biological ex vivo lung surface. The optical ranging detector is also used to be set above the chest and abdomen of a human body to detect the amplitude of the human body's breathing curve. The main control module is connected to the automatic data collector, and the automatic data collector is respectively connected to the optical ranging detector and the pressure sensor. The main control module receives the detection data of the optical ranging detector and the pressure sensor through the automatic data collector.

5. The lung breathing simulation device for radiotherapy according to claim 4, characterized in that: The optical ranging detector is specifically a laser ranging detector, which is used to capture the lung surface deformation in real time by emitting and receiving laser three-dimensional point clouds, construct a three-dimensional model of the biological lung surface in vitro, or detect the amplitude of the human body's breathing curve.

6. The lung breathing simulation device for radiotherapy according to claim 1, characterized in that: The ex vivo lungs were infused with a hydrogel that mimicked a tumor.

7. The lung breathing simulation device for radiotherapy according to claim 3, characterized in that: The driving module includes a motor and a screw rod, which is connected to the output end of the motor. A slider is arranged on the screw rod, and the slider moves forward or backward with the rotation of the screw rod. The pressing module is installed on the slider and moves forward or backward with the slider. The pressing module is a U-shaped fork, and the fork legs of the U-shaped fork are respectively aligned with the two air storage balloons. The motor adjusts the speed and direction according to the frequency and number of the pulse signal. The front limit sensor and the rear limit sensor are respectively installed at the front and rear of the screw rod. The front limit sensor and the rear limit sensor are both electrically connected to the main control module for limiting the maximum travel in the front and rear directions.

8. The lung breathing simulation device for radiotherapy according to claim 1, characterized in that: The electronic detector is an electronic portal imaging device, and the electronic detector is arranged below the biological ex vivo lung.

9. A method for acquiring three-dimensional dose distribution for the lung breathing simulation device for radiotherapy according to claim 1, characterized in that: The steps include: A) The electronic detector under the isolated lung collects the flux distribution of the radiotherapy rays after they pass through the isolated lung in real time. This flux distribution is called the fluoroscopic flux distribution. B) Mapping the perspective flux distribution onto the real-time captured three-dimensional model of the biological ex vivo lung surface to obtain the three-dimensional transmission flux distribution, using ray tracing technology to restore the specific path of the radiotherapy ray from the radiation source to the biological ex vivo lung surface, and based on the three-dimensional transmission flux distribution and the specific path, according to the unit mass original ray energy deposition and flux distribution kernel calculation to obtain the flux distribution of the radiotherapy ray before entering the biological ex vivo lung, which is called the incident flux distribution P1; C) Based on the exponential attenuation law of radiotherapy rays, the incident flux distribution P2 is directly inversely deduced from the incident flux distribution P1; D) performing multiple iterations of optimization on the incident flux distribution P1 and the incident flux distribution P2 to obtain an optimized incident flux distribution Pn; E) The incident flux distribution Pn is dynamically corrected in real time using a biological deformable registration algorithm, and the corrected measurement results are mapped to a unified reference coordinate system. Subsequently, a Monte Carlo algorithm is used within the unified reference coordinate system to simulate the transmission process of photons in radiotherapy rays in an inhomogeneous medium. The incident flux distribution Pn is converted into an actual absorbed dose distribution using specific biological tissue-dose conversion factors and correction coefficients combined with the 4DCT image of the biological ex vivo lung, and the three-dimensional dose distribution in the biological ex vivo lung is reconstructed.

10. The method for acquiring three-dimensional dose distribution according to claim 9, characterized in that: In step A, the signal collected by the electronic detector in real time is deconvoluted to obtain the flux distribution of the radiotherapy rays after passing through the biological ex vivo lung.

11. The method for acquiring three-dimensional dose distribution according to claim 9, characterized in that: In step D, the specific process of multiple iterative optimization is: compare the incident flux distribution P1 and the incident flux distribution P2 to obtain the residual, reverse the residual into the correction amount of the incident flux distribution P2, and update the incident flux distribution P2 in combination with the relaxation factor to ensure the non-negative constraint. When the difference between the incident flux distribution P1 and the incident flux distribution P2 is less than the threshold, stop updating, and output the iteratively optimized incident flux distribution Pn.

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