Ionization chamber with adjustable polar plate distance and adjusting method

Abstract

The invention provides an ionization chamber with an adjustable polar plate distance and an adjusting method, and the ionization chamber comprises a housing which is provided with a through hole for a beam to pass through; the collector is fixed in the shell; the high-voltage electrode and the collector are arranged at an interval; the spacer ring is connected with the collector, and the spacer ring is located between the collector and the high-voltage electrode; the adjusting assembly comprises a lead screw, the lead screw is connected with the high-voltage electrode, the lead screw is rotatably arranged relative to the adjusting assembly, and the high-voltage electrode is driven to move by rotating the lead screw, so that the distance between the collector and the high-voltage electrode is adjusted. According to the ionization chamber with the adjustable polar plate distance and the adjusting method, the technical problem that the monitoring result of the radiotherapy dose rate is inaccurate due to the influence of ion recombination in the ionization chamber in the related technology is solved.

Description

Technical Field

[0001] The invention relates to the technical field of radiotherapy monitoring, and in particular to an ionization chamber with adjustable plate spacing and an adjustment method. Background Art

[0002] In the fiercely competitive field of medical devices, radiotherapy equipment that takes into account both conventional radiotherapy and Flash radiotherapy is the future development trend. Traditional conventional dose rate radiotherapy uses a thin-window flat-panel ionization chamber to monitor the parameters of the electron beam or X-ray. In the ultra-high dose rate monitoring environment, the density of positive and negative ions generated by secondary electron radiation ionization is large, and the traditional flat-panel ionization chamber is prone to ion recombination effects, resulting in the inability to accurately monitor the ultra-high dose rate in the Flash mode, thereby affecting the dose accuracy and treatment safety of Flash radiotherapy. Moreover, in the Flash radiotherapy mode, the traditional ionization chamber has a large number of gas medium ionizations and a large current collected by the plate, which can easily burn out the electronic modules outside the ionization chamber. Therefore, the thin-window flat-panel ionization chamber used in traditional radiotherapy cannot take into account the ultra-high dose rate Flash radiotherapy.

[0003] In order to solve the problem of ion recombination, the amount of gas medium between the plates of the ionization chamber must be greatly reduced. Among them, small spacing is one of the main means to reduce the amount of gas medium between the plates of the ionization chamber. The low spacing solution is to reduce the distance between the electrodes to achieve the purpose of reducing the total amount of gas between the electrodes, thereby solving the problem of ion recombination. In other words, if this solution is adopted, by adjusting the plate spacing, ion recombination can be avoided or reduced, and the accuracy of monitoring the beam dose rate can be improved, but the specific small spacing that is suitable for Flash radiotherapy still needs to be studied, and the electrode spacing of the existing ionization chamber is generally fixed.

[0004] Therefore, the prior art needs to be further developed. Summary of the invention

[0005] The purpose of the present invention is to overcome the above technical deficiencies and provide an ionization chamber with adjustable plate spacing and an adjustment method to solve the technical problem in the related art that the ionization chamber is affected by ion recombination, resulting in inaccurate monitoring results of radiotherapy dose rate.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions: an ionization chamber with adjustable plate spacing is provided, comprising: a shell, a through hole is provided on the shell for the beam to pass through; a collector, the collector is fixed in the shell; a high-voltage electrode, the high-voltage electrode and the collector are spaced apart; a spacer ring, the spacer ring is connected to the collector, and the spacer ring is located between the collector and the high-voltage electrode; an adjustment component, the adjustment component includes a screw rod, the screw rod is connected to the high-voltage electrode, the screw rod is rotatably arranged relative to the adjustment component, and the high-voltage electrode is driven to move by rotating the screw rod, thereby adjusting the distance between the collector and the high-voltage electrode.

[0007] Furthermore, the shell includes a base and an end cover, a accommodating cavity is arranged between the base and the end cover, a structure for fixing the collecting electrode is provided on the base, and a structure opposite thereto is provided on the end cover; the collecting electrode, the spacer ring, the high-voltage electrode and a screw rod for adjusting the spacing between the electrode plates are all arranged in the accommodating cavity, and the spacer ring is used to maintain a stable spacing between the collecting electrode and the high-voltage electrode.

[0008] Furthermore, the adjustment component also includes a motor, which is arranged on the end cover and located outside the accommodating cavity. The screw rod is connected to the motor, and the motor is used to drive the screw rod.

[0009] Furthermore, the adjustment assembly also includes an adjustment mechanism connected to the high-voltage pole, a connecting portion is provided on the adjustment mechanism, a screw rod is connected to the connecting portion, and the position of the high-voltage pole is adjusted by rotating the screw rod, thereby adjusting the distance between the pole plates. Furthermore, two guide rod holes are provided on the connecting part, and the adjusting assembly also includes two guide rods. Each guide rod and each guide rod hole are provided correspondingly. The guide rod is provided through the guide rod hole. The guide rod is connected to the connecting part. When the screw rod is rotated to drive the connecting part to move, the connecting part moves along the guide rod.

[0010] Furthermore, the shell is a cylindrical structure, and there are two adjustment components, which are symmetrically arranged on the end cover.

[0011] Furthermore, the spacer ring is provided with a first opening and a second opening, the first opening is provided through the ring wall of the spacer ring, the second opening is embedded in the ring wall of the spacer ring, and the first opening and the second opening are provided at intervals.

[0012] A method for adjusting is applied to the above-mentioned ionization chamber with adjustable plate spacing, the method comprising: according to the target beam parameters in the treatment plan and the ionization chamber calibration database, the beam detection module calculates and selects the spacing between the collector 2 and the high-voltage electrode 3 corresponding to the target beam parameters, and the spacing is used as the initial spacing N0; the controller moves the high-voltage electrode through the adjustment component to adjust the spacing between the collector and the high-voltage electrode to the initial spacing N0, the ionization chamber receives the target beam irradiation and uses the beam detection module to compare and adjust at the same time: if the beam parameters measured by the ionization chamber are consistent with the beam parameters measured by the beam detection module, the initial spacing N0 is used as the final spacing N for subsequent formal treatment beam measurement; if the beam parameters measured by the ionization chamber are inconsistent with the beam parameters measured by the beam detection module, the high-voltage electrode is moved according to a certain ratio until the beam parameters measured by the ionization chamber are consistent with the beam parameters measured by the detection film, and the spacing between the collector and the high-voltage electrode is the final spacing N.

[0013] Furthermore, the final spacing N is determined by: N=N0±K*(X-1)N0, where X is the number of times the high voltage pole is moved, and K is the adjustment proportional coefficient. Further, the beam detection module is a QA tool, a film or a diamond.

[0014] Beneficial effects: 1. The ionization chamber of the present invention has an adjustable distance between the high-voltage electrode and the collecting electrode, so that the ionization chamber can be applied to the measurement of electron beams or X-ray beams at conventional dose rates, and can also take into account the measurement of electron beams or X-ray beams at ultra-high dose rates, thereby expanding the application range of the ionization chamber. When measuring electron beams or X-ray beams at conventional dose rates, the distance between the high-voltage electrode and the collecting electrode is increased, the sensitivity of the ionization chamber is improved, the microcurrent is increased, and the measurement of low-dose rate beams is achieved. When measuring electron beams or X-ray beams at ultra-high dose rates, the distance between the high-voltage electrode and the collecting electrode is reduced to reduce the total amount of gas between the electrodes, reduce the sensitivity of the ionization chamber, weaken or eliminate the ion recombination effect, and reduce the microcurrent at the same time, which will not damage the subsequent electronic modules, thereby ensuring the measurement of ultra-high dose rate beams. The scope of use of the ionization chamber has been expanded, providing a prerequisite for the development of radiotherapy equipment that takes into account both conventional radiotherapy and Flash radiotherapy.

[0015] 2. In the ionization chamber with adjustable plate spacing of the present invention, guide rods are arranged on both sides of the screw rod to improve the stability of the high-voltage pole during movement, thereby providing a guarantee for the normal use of the ionization chamber.

[0016] 3. The adjustment method of the present invention can be used to quickly adjust the spacing value corresponding to each application scenario, thereby improving the treatment efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic structural diagram of a dual ionization chamber used in an embodiment of the present invention; Figure 2 is an exploded view of an ionization chamber with adjustable plate spacing used in an embodiment of the present invention; Figure 3 is a schematic structural diagram of a base used in an embodiment of the present invention; Figure 4 is a schematic diagram of the structure of the collector used in an embodiment of the present invention; Figure 5 is a schematic structural diagram of a spacer ring used in an embodiment of the present invention; Figure 6 is a schematic diagram of the structure of the high voltage electrode used in an embodiment of the present invention; Figure 7 is a schematic diagram of the structure of the adjustment mechanism used in the embodiment of the present invention; Figure 8 It is a cross-sectional view of an ionization chamber with adjustable plate spacing used in an embodiment of the present invention.

[0018] The above drawings include the following reference numerals: 1. Shell; 11. Through hole; 12. First flange; 13. Second flange; 14. Base; 141. Opening; 15. End cover; 16. Accommodating chamber; 2. Collecting electrode; 21. Collecting insulating ring; 22. Collecting bearing part; 23. Central collecting part; 24. Peripheral collecting part; 25. Pin; 3. High-voltage electrode; 31. High-voltage part; 32. High-voltage bearing part; 33. High-voltage insulating ring; 4. Spacer ring; 41. First opening; 42. Second opening; 5. Adjusting assembly; 51. Screw rod; 52. Motor; 53. Adjusting mechanism; 531. Connecting part; 532. Guide rod hole; 54. Guide rod; 60. First ionization chamber; 70. Second ionization chamber. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0020] According to an embodiment of the present invention, an ionization chamber with adjustable plate spacing is provided. Figures 1 to 8 , including: a shell 1, the shell 1 is provided with a through hole 11 for the beam to pass through; a collector 2, the collector 2 is fixed on the first flange 12; a high-voltage electrode 3, the high-voltage electrode 3 is spaced apart from the collector 2; a spacer ring 4, the spacer ring 4 is connected to the collector 2, and the spacer ring 4 is located between the collector 2 and the high-voltage electrode 3; an adjustment component 5, the adjustment component 5 includes a screw rod 51, the screw rod 51 is connected to the high-voltage electrode 3, the screw rod 51 is rotatably arranged relative to the adjustment component 5, and the screw rod 51 is rotated to make the high-voltage electrode 3 approach or move away from the collector 2, thereby adjusting the distance between the collector 2 and the high-voltage electrode 3. Figure 2 As shown, the screw rod 51 moves up and down to drive the high-voltage electrode 3 to move up and down, thereby adjusting the distance between the collecting electrode 2 and the high-voltage electrode 3.

[0021] Before using the ionization chamber in practical applications, it is necessary to calibrate the ionization chamber to find the corresponding relationship between the dose rate and the plate spacing, which will serve as one of the bases for determining the spacing in subsequent use. Several beams of a series of dose rates accurately measured by film or diamond are respectively passed through the ionization chamber, such as the dose rate in the range of 50cGy / s to 100cGy / s, and the plate spacing is adjusted to evaluate the electron recombination effect at different spacings, and the spacing N1 with small or no electron recombination effect is used as the spacing for beam measurement in the range of 50cGy / s to 100cGy / s. Similarly, for ultra-high dose rates, such as the range of 1Gy / s to 10Gy / s, the plate spacing is adjusted to evaluate the electron recombination effect at different spacings, and the spacing N2 with small or no electron recombination effect is used as the spacing for beam measurement in the range of 1Gy / s to 10Gy / s. Similarly, the spacing N3 corresponding to the range of 10Gy / s to 30Gy / s, the spacing N4 corresponding to the range of 30Gy / s to 60Gy / s, etc. The spacing values ​​corresponding to each dose rate range from conventional dose rate to ultra-high dose rate that may be used in Flash radiotherapy are completed. After the ionization chamber is calibrated, the corresponding relationship between the dose rate and the initial spacing is stored in the controller.

[0022] When treatment is required, detect whether the distance between the plates is the minimum distance. If not, the controller first controls the action of the adjustment component 5 to reset the distance between the plates to the minimum value to ensure the safety of the subsequent electrical module of the ionization chamber. Then, according to the target dose rate and dose given in the treatment plan, the corresponding initial distance N0 is selected, and the controller moves the high-voltage pole 3 through the adjustment component 5 to adjust the distance between the plates to the initial distance N0. Set the machine jump number of the beam generating device according to the target dose rate and dose given in the treatment plan. In order to ensure the accuracy of the measurement and the safety of the treatment, QA tools, or films, or diamonds are still used for comparison and verification before formal treatment. The comparison and verification method is: if the parameters measured by the ionization chamber are consistent with the parameters measured by the QA tool, or film, or diamond, etc., the subsequent formal treatment spacing is performed according to the initial spacing N0.

[0023] If the beam parameters measured by the ionization chamber are inconsistent with the beam parameters measured by the beam detection module, the spacing adjustment will continue until the beam parameters measured by the ionization chamber are consistent with the beam parameters measured by the beam detection module, and the final spacing after adjustment will be used as the spacing value for the subsequent formal treatment. The adjusted final spacing and corresponding parameters such as dose rate will continue to be stored in the controller and will be used as the priority for the next beam measurement with the same parameters. After the treatment is completed, the plate spacing should be reset to the minimum value to protect the subsequent electronic modules. The adjustable ionization chamber and adjustment method can be applied to both conventional conventional dose rate radiotherapy and ultra-high dose rate Flash radiotherapy mode.

[0024] By adjusting the setting of the component 5, the distance between the collecting electrode 2 and the high-voltage electrode 3 is adjustable, so that the distance can be optimized until the ion recombination is reduced or eliminated, the accuracy of the monitored radiotherapy dose rate is guaranteed, and the patient is provided with an accurate dose and dose rate. The ionization chamber with adjustable plate spacing of this embodiment solves the technical problem of inaccurate monitoring results of radiotherapy dose rate caused by the influence of ion recombination in the ionization chamber at ultra-high dose rate in the related art.

[0025] It should be noted that according to industry standards and regulatory requirements, in order to ensure the safety of use, a dual ionization chamber is required for radiotherapy monitoring operations (such as Figure 1 As shown). In this embodiment, each ionization chamber can adjust the distance between the electrode plates. The arrangement order of the collector 2, the spacer ring 4, the high-voltage electrode 3 and the adjustment component 5 of the first ionization chamber 60 and the second ionization chamber 70 are the same, and the first ionization chamber 60 and the second ionization chamber 70 are arranged in series back to back to form a symmetrical structure. The two can be fixedly connected together or arranged separately. The spacer ring 4 is made of insulating material. In addition to insulating between the collector 2 and the high-voltage electrode 3, it also limits the minimum spacing of the gap adjustment and also plays a limiting role. That is, when the adjustment component 5 drives the high-voltage electrode 3 to contact the spacer ring 4, the minimum spacing between the high-voltage electrode 3 and the collector 2 is reached to prevent the spacing from being too small so that the gas medium undergoes air breakdown under the action of the electric field. The thickness of the spacer ring 4 is equal to the thickness of the collecting part + the minimum gap between the collecting part and the high-voltage part + the thickness of the high-voltage part.

[0026] See also Figure 2 and Figure 3 In the ionization chamber with adjustable plate spacing of the present embodiment, the shell 1 includes a base 14 and an end cover 15, and an accommodating cavity 16 is arranged between the base 14 and the end cover 15. The base 14 is provided with a structure for fixing the collector 2, and the end cover 15 is provided with a structure opposite thereto; the collector 2, the spacer ring 4, the high-voltage electrode 3 and the screw rod 51 for adjusting the plate spacing are all arranged in the accommodating cavity 16, and the spacer ring 4 is used to maintain a stable interval between the collector 2 and the high-voltage electrode 3.

[0027] See also Figure 2 and Figure 3In the ionization chamber with adjustable plate spacing in this embodiment, the housing 1 also includes a first flange 12 and a second flange 13, the first flange 12 is arranged on the base 14, and the second flange 13 is arranged on the end cover 15; a receiving chamber 16 is arranged between the base 14 and the end cover 15, and the collector 2, the spacer ring 4, the high-voltage electrode 3 and the screw rod 51 are all arranged in the receiving chamber 16. A through hole 11 for the beam to pass through is arranged in the middle of the end cover 15 and the base 14. A second flange 13 extending inward is arranged on the end cover 15, and the second flange 13 is used to fix the adjustment component 5. The receiving chamber 16 between the base 14 and the end cover 15 is mainly used to accommodate and install other components. A first flange 12 extending inward is also arranged at the bottom of the base 14, and the collector 2 is fixed on the first flange 12. Openings 141 for the plate leads to pass through are symmetrically opened on both sides of the base 14.

[0028] See also Figure 1 and Figure 4 In this embodiment, the collector 2 includes a collecting insulating ring 21, a collecting bearing part 22, a central collecting part 23 and a peripheral collecting part 24. Among them, the peripheral collecting part 24 of the first ionization chamber 60 adopts a "five-partition" form to divide the periphery of the collecting part into five equal parts, and the peripheral collecting part 24 of the second ionization chamber 70 adopts a "one-partition" form, that is, no division. The main purpose of this partition is to meet the requirements of regulations on dose symmetry and uniformity, and the dose symmetry and uniformity are verified by comparing multiple peripheral collecting parts 24 and central collecting parts 23.

[0029] Specifically, the collecting bearing part 22 can be Mylar film or ceramic or mica. There are two pins 25 on one side of the collecting part and three on the other side. When Mylar film is used, its electron beam has the best penetration, and the blocking and scattering of the electron beam can be almost ignored, and the influence on the beam is minimal; at the same time, it can reduce the secondary electrons generated by the absorption of neutrons by the electron beam or X-ray and the film, and avoid the measurement inaccuracy caused by the secondary electrons. When ceramics and mica are used, the structural strength of the collecting electrode 2 and the high-voltage electrode 3 is better. Each collecting part and the high-voltage part 31 are plated on Mylar film, ceramic sheet, or mica sheet by evaporation. In this embodiment, the collecting part adopts Mylar film, and the Mylar film is evenly pasted and laid on the collecting insulating ring 21. After pasting and laying flat, it needs to be cleaned, and then evaporated after cleaning, and then cleaned again after evaporation, so as to avoid leakage current caused by the introduction of pollutants in actual use, which affects the accuracy of the measurement results.

[0030] See also Figure 2In the ionization chamber with adjustable plate spacing in this embodiment, the adjustment component 5 further includes a motor 52, which is arranged on the end cover 15, and the motor 52 is located outside the accommodating chamber 16. The screw 51 is connected to the motor 52, and the motor 52 is used to drive the screw 51. The adjustment of the plate is achieved by the motor 52 in conjunction with the screw drive, and a mounting hole for mounting the motor 52 is provided on the second flange 13. Of course, other transmission forms such as threaded transmission, cam mechanism, hydraulic pressure or pneumatic pressure can also be used.

[0031] See also Figure 2 , Figure 6 and Figure 7 In the ionization chamber with adjustable plate spacing in this embodiment, the adjustment component 5 includes an adjustment mechanism 53 connected to the high-voltage electrode 3, a connection portion 531 is provided on the adjustment mechanism 53, and the screw 51 is connected to the connection portion 531. The position of the high-voltage electrode 3 is adjusted by rotating the screw 51, thereby adjusting the distance between the collector 2 and the high-voltage electrode 3. The high-voltage electrode 3 includes a high-voltage portion 31, a high-voltage bearing portion 32, and a high-voltage insulating ring 33. The high-voltage portion 31 of the high-voltage electrode 3 and the collector 2 are both made of low-Z metal materials, such as aluminum and titanium, and are arranged on their respective bearing portions by evaporation, etc., with a coating thickness of 20μm to 100μm. Because low-Z metals have little blocking and scattering of electron beams, and have little energy loss. One end of the adjustment mechanism 53 is connected to the high-voltage electrode 3, and the other end is connected to the motor 52 through the connection portion 531 by screw transmission. The adjustment mechanism 53 moves up and down under the action of the motor 52 and the screw transmission, thereby driving the high-voltage electrode 3 to move up and down, thereby adjusting the distance between the collector 2 and the high-voltage electrode 3.

[0032] See also Figure 7 In the ionization chamber with adjustable plate spacing of this embodiment, two guide rod holes 532 are further provided on the connecting portion 531, and the adjustment assembly 5 further includes two guide rods 54, each guide rod 54 is provided corresponding to each guide rod hole 532, and the guide rod 54 is provided through the guide rod hole 532, one end of the guide rod 54 is connected to the connecting portion 531, and the other end of the guide rod 54 is connected to the second flange 13, and when the screw rod 51 is rotated to drive the connecting portion 531 to move, the connecting portion 531 moves along the guide rod 54. A transmission hole matching the screw rod 51 is provided in the middle of the connecting portion 531. In order to ensure the smooth movement of the adjustment mechanism 53, the connecting portion 531 is provided with guide rod holes 532 on both sides of the transmission hole, and the guide rod 54 moves up and down in the guide rod hole 532.

[0033] See also Figure 1 , Figure 2 and Figure 8In the ionization chamber with adjustable plate spacing in this embodiment, the housing 1 is a cylindrical structure, the first flange 12 and the second flange 13 are both annular structures, there are two adjustment components 5, and the two adjustment components 5 are symmetrically arranged on the end cover 15. The collector 2 is connected with the spacer ring 4 and fixed to the annular flange of the base 14, wherein the collector 2 plate of the five-partition is coaxially arranged with the through hole 11.

[0034] See also Figure 2 and Figure 5 In the ionization chamber with adjustable plate spacing in this embodiment, the first opening 41 and the second opening 42 are provided on the spacer ring 4. The first opening 41 is provided through the ring wall of the spacer ring 4, and the second opening 42 is embedded in the ring wall of the spacer ring 4. The first opening 41 and the second opening 42 are provided at intervals. In this embodiment, the spacer ring 4 is provided with the first opening 41 on the double-pin side of the collector 2. Since the pins of the high-voltage pole 3 are also provided on this side, it is necessary to provide the first opening 41 through the ring wall of the spacer ring 4. The second opening 42 is provided on the three-pin side, and no other components are connected to the corresponding upper side, because only a groove needs to be provided on the ring wall.

[0035] In the adjustment method of the present embodiment, according to the target beam parameters in the treatment plan and the ionization chamber calibration database, the beam detection module calculates and selects the spacing between the collector 2 and the high-voltage electrode 3 corresponding to the target beam parameters, and this spacing is used as the initial spacing N0; the controller moves the high-voltage electrode 3 through the adjustment component 5 to adjust the spacing between the high-voltage electrode 3 and the collector 2 to the initial spacing N0, and the ionization chamber receives the target beam irradiation and uses the beam detection module to compare and adjust at the same time: if the beam parameters measured by the ionization chamber are consistent with the beam parameters measured by the beam detection module, the initial spacing N0 is used as the final spacing N for subsequent formal treatment beam measurement; if the beam parameters measured by the ionization chamber are inconsistent with the beam parameters measured by the beam detection module, the high-voltage electrode 3 is moved according to a certain ratio until the beam parameters measured by the ionization chamber are consistent with the beam parameters measured by the detection film, and the spacing between the collector 2 and the high-voltage electrode 3 is the final spacing N.

[0036] In the adjustment method of the present embodiment, the method for determining the final spacing N is: N=N0±K*(X-1)N0, where X is the number of times the high-voltage electrode 3 is moved, and K is the adjustment proportional coefficient. K can be set according to factors such as the rotation performance of the motor and the screw 51. In the present embodiment, K=0.05, that is, it is adjusted according to the adjustment amount of 5% of the current spacing. The adjustment component 5 moves the high-voltage electrode 3 and adjusts the spacing between the high-voltage electrode 3 and the collector 2 to the initial spacing N0. When at the initial spacing N0, the beam parameters measured by the ionization chamber are consistent with the beam parameters measured by the beam detection module, and the spacing between the collector 2 and the high-voltage electrode 3 does not need to be adjusted. At this time, X=1, N=N0.

[0037] Specifically, the gap between the collector and the high-voltage electrode is adjustable, and the measurable range is wide. It can be used not only in the application scenarios of traditional conventional dose rates, but also in the flash therapy mode under ultra-high dose rates. By reducing the gap between the collector and the high-voltage electrode to an appropriate value, the total amount of inter-electrode gas is reduced, the ion recombination effect is reduced, and the beam parameters are accurately measured, so that the ionization chamber can be used in the flash therapy mode.

[0038] In the case of the initial spacing N0, if there is an ion recombination effect that affects the measurement accuracy, the total amount of inter-electrode gas should be reduced, and the spacing between the collector 2 and the high-voltage electrode 3 needs to be continuously reduced. In this case, the final spacing N is less than or equal to the initial spacing N0; in the case of the initial spacing N0, if the micro-current collected by the collector plate is too small to measure the relevant parameters, the total amount of inter-electrode gas should be increased, and the spacing between the collector 2 and the high-voltage electrode 3 needs to be continuously increased. In this case, the final spacing N is greater than or equal to the initial spacing N0. After the ionization chamber completes the monitoring work, the controller sends an instruction to the motor 52 to control the inter-electrode spacing to the minimum spacing, that is, to move the high-voltage electrode 3 to the nearest distance from the collector 2, complete the ionization chamber state initialization, and prepare for the next work. In the adjustment method of this embodiment, the beam detection module is a QA tool, film, diamond, etc., and both film and diamond have the advantages of wide spectrum transmittance, high thermal shock resistance, and low scattering.

[0039] It should be noted that the initial spacing N0 is a spacing value calculated by film calibration or by machine learning of past data. Before the ionization chamber is used, the spacing values ​​corresponding to multiple beams are measured by film, and the initial spacing is set according to the correspondence between the dose rate and the spacing value. It can also be calculated based on the dose rate and spacing value used in the ionization chamber in the past. The final spacing N and the corresponding beam parameters of the last adjustment are stored in the controller as the selection of the next initial spacing. The target beam parameters are provided by the radiotherapy planning system or manually entered by the user.

[0040] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0041] Optionally, the specific examples in this embodiment may refer to the examples described in the above embodiments, and this embodiment will not be described in detail here.

[0042] The serial numbers of the above-mentioned embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0043] In the above embodiments of the present application, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, please refer to the relevant description of other embodiments.

[0044] The above is only a preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. An ionization chamber with adjustable plate spacing, characterized in that: include: A housing (1), wherein the housing (1) is provided with a through hole (11) for the beam to pass through; A collecting electrode (2), the collecting electrode (2) being fixed inside the shell (1); A high voltage electrode (3), the high voltage electrode (3) and the collecting electrode (2) being arranged at an interval; A spacer ring (4), the spacer ring (4) being connected to the collecting electrode (2), the spacer ring (4) being located between the collecting electrode (2) and the high-voltage electrode (3); An adjustment component (5), the adjustment component (5) comprising a screw rod (51), the screw rod (51) being connected to the high-voltage electrode (3), and the screw rod (51) being rotated to drive the high-voltage electrode (3) to move, thereby adjusting the distance between the collecting electrode (2) and the high-voltage electrode (3).

2. The ionization chamber with adjustable plate spacing according to claim 1, characterized in that: The housing (1) comprises a base (14) and an end cover (15); a receiving cavity (16) is provided between the base (14) and the end cover (15); a structure for fixing the collecting electrode (2) is provided on the base (14), and a structure corresponding thereto is provided on the end cover (15); The collecting electrode (2), the spacer ring (4), the high-voltage electrode (3), and the screw rod (51) for adjusting the distance between the electrode plates are all arranged in the accommodating cavity (16); the spacer ring (4) is used to maintain a stable distance between the collecting electrode (2) and the high-voltage electrode (3).

3. The ionization chamber with adjustable plate spacing according to claim 2, characterized in that: The adjustment assembly (5) further comprises a motor (52), wherein the motor (52) is arranged on the end cover (15), the motor (52) is located outside the accommodating cavity (16), the screw rod (51) is connected to the motor (52), and the motor (52) is used to drive the screw rod (51).

4. The ionization chamber with adjustable plate spacing according to claim 3, characterized in that: The adjustment assembly (5) comprises an adjustment mechanism (53) connected to the high-voltage pole (3); the adjustment mechanism (53) is provided with a connection portion (531); the screw rod (51) is connected to the connection portion (531); the position of the high-voltage pole (3) is adjusted by rotating the screw rod (51), thereby adjusting the distance between the pole plates.

5. The ionization chamber with adjustable plate spacing according to claim 4, characterized in that: The connecting portion (531) is further provided with two guide rod holes (532). The adjusting assembly (5) further comprises two guide rods (54). Each guide rod (54) and each guide rod hole (532) are provided correspondingly. The guide rod (54) is provided through the guide rod hole (532). The guide rod (54) is connected to the connecting portion (531). When the screw rod (51) is rotated to drive the connecting portion (531) to move, the connecting portion (531) moves along the guide rod (54).

6. The ionization chamber with adjustable plate spacing according to claim 5, characterized in that: The housing (1) is a cylindrical structure, and there are two adjustment assemblies (5), which are symmetrically arranged on the end cover (15).

7. The ionization chamber with adjustable plate spacing according to claim 1, characterized in that: The spacer ring (4) is provided with a first opening (41) and a second opening (42); the first opening (41) is provided through the ring wall of the spacer ring (4); the second opening (42) is embedded in the ring wall of the spacer ring (4); the first opening (41) and the second opening (42) are provided at intervals.

8. A method for adjusting the plate spacing of an ionization chamber according to any one of claims 1 to 7, characterized in that: The adjustment method comprises: According to the target beam parameters in the treatment plan and the ionization chamber calibration database, the beam detection module calculates and selects the spacing between the collector 2 and the high-voltage electrode 3 corresponding to the target beam parameters, and this spacing is used as the initial spacing N0; The controller moves the high-voltage electrode (3) through the adjustment component (5) to adjust the distance between the high-voltage electrode (3) and the collecting electrode (2) to the initial distance N0. The ionization chamber receives the target beam irradiation and uses the beam detection module to compare and adjust at the same time: if the beam parameters measured by the ionization chamber are consistent with the beam parameters measured by the beam detection module, the initial distance N0 is used as the final distance N for subsequent formal treatment beam measurement; if the beam parameters measured by the ionization chamber are inconsistent with the beam parameters measured by the beam detection module, the high-voltage electrode (3) is moved according to a certain ratio until the beam parameters measured by the ionization chamber are consistent with the beam parameters measured by the detection film, at which time the distance between the collecting electrode (2) and the high-voltage electrode (3) is the final distance N.

9. The adjustment method according to claim 8, characterized in that: The method for determining the final spacing N is: N=N0±K*(X-1)N0, wherein X is the number of times the high voltage pole (3) is moved, and K is the adjustment proportional coefficient.

10. The adjustment method according to claim 9, characterized in that: The beam detection module is a QA tool, a film or a diamond.

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