A medical accelerator and a dose monitoring method based on leakage dose measurement thereof

Abstract

The present invention relates to the technical field of medical accelerators, and discloses a medical accelerator, comprising an accelerating tube, a beam pipe, a beam scraper, a bellows and a beam needle. The beam pipe, the beam scraper, the bellows and the beam needle are detachably connected in sequence, and the four have a common central axis and are connected to form a straight line channel for electron beams to be transmitted in the straight line channel; the inner aperture of the beam scraper is smaller than the inner aperture of the beam pipe. A dose monitoring method is also disclosed, which establishes a relevant numerical relationship by simultaneously testing the X-rays generated by the first electron beam and the dose of the second electron beam before treatment, and monitors the dose of the second electron beam by testing the dose of the X-rays during treatment. The present invention generates X-rays by colliding the first electron beam with the beam scraper, and synchronously tests the X-rays to obtain the dose rate of the second electron beam at the outlet end of the beam needle, which does not affect the treatment process and can achieve online dose monitoring.

Description

Technical Field

[0001] This invention relates to the field of medical accelerator technology, specifically to a medical accelerator and a dose monitoring method based on leak dose monitoring. Background Art

[0002] According to the requirements of the national standard GB9706.5-2008, medical linear electron accelerators must include a dose monitoring system. The dose monitoring system used in traditional medical accelerators consists of an ionization chamber detector and its auxiliary circuitry. The ionization chamber is located within the radiation system, installed between the homogenizing filter or scattering foil and the secondary collimator of the photon beam. It consists of several pole pieces, two pairs for monitoring the homogenization in two mutually perpendicular directions within the radiation field, one for monitoring energy changes in the radiation, and two for detecting the absorbed dose. Most traditional medical accelerator dose monitoring systems use flat-plate ionization chambers, whose size should cover the entire treatment field; a few use finger-shaped ionization chambers. The function of the dose monitoring system is to monitor the dose rate, integrated dose, and symmetry and flatness of the X-ray and electron beams.

[0003] The medical accelerator of this invention directly uses electron beams to treat tumors. The entire process of the electron beam traveling from the accelerator tube to the tumor is transmitted in a thin tube (with an inner diameter of less than 5 mm). It cannot pass directly through the ionization chamber. Therefore, the ionization chamber is not suitable for this device. At present, there are no relevant dose monitoring methods at home and abroad to test the therapeutic dose of such a small electron beam online. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a medical accelerator for the electron beam of Ono, and a dose monitoring method for the medical accelerator capable of online monitoring of the electron beam of Ono during treatment.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a medical accelerator, comprising an electron gun control power supply, an electron gun, an accelerating tube, a magnetron, a modulator, a beam channel, a beam scraper, a bellows, and a beam needle. The electron gun control power supply controls the injection voltage of the electron gun. The electron gun outputs an electron beam, and the accelerating tube accelerates the electron beam output from the electron gun before outputting it through the beam needle. The modulator controls the magnetron. The magnetron is connected to the accelerating tube via a waveguide chain. The rear end of the beam channel is fixedly connected to the center of the front end of the accelerating tube. The beam channel, the beam scraper, the bellows, and the beam needle are sequentially and detachably connected, sharing a central axis and forming a straight channel for the electron beam to propagate through. The inner diameter of the beam scraper is smaller than the inner diameter of the beam channel.

[0007] Preferably, the scraper is a cylinder with a central hole.

[0008] Preferably, the material of the scraper is lead.

[0009] Preferably, the cylinder contains an inner ring.

[0010] Preferably, the inner ring is made of solid water or graphite.

[0011] Preferably, the bellows comprises a flexible channel tube, two flanges, and at least three sets of bolts.

[0012] Preferably, the shape of the elastic channel tube can be adjusted by adjusting the position of the nut in the bolt.

[0013] Preferably, the outlet end of the beam needle is a sealed end.

[0014] The present invention also provides a dose monitoring method for measuring any of the above-mentioned technical solutions in a medical accelerator, comprising the following steps:

[0015] S1: The first electron beam strikes the beam scraper to generate X-rays, and the first dose probe collects the X-ray signal;

[0016] S2: After the first dose probe completes signal collection, the data processing system processes the signal to obtain the dose rate H of the X-rays. a ;

[0017] S3: The data processing system's dose H of X-rays a The data is further processed to obtain the dose H of the second electron beam passing through the beam needle. b .

[0018] Preferably, the dose rate H of the second electron beam passing through the beam needle in step S3 is... b With the dose rate H of the X-rays a There exists a linear numerical relationship: H b =KH a .

[0019] Preferably, the steps for determining the value of K are as follows:

[0020] P1: The first electron beam strikes the beam scraper to generate X-rays, and the first dose probe collects the signal of the X-rays; the second electron beam passes through the beam needle, and the third dose probe collects the signal of the second electron beam passing through the beam needle;

[0021] P2: After the first dose probe finishes collecting the X-ray signal, the first data processing system processes the X-ray signal to obtain the dose rate H11 of the X-ray; after the third dose probe finishes collecting the signal of the second electron beam, the third data processing system processes the signal of the second electron beam to obtain the dose rate H21 of the second electron beam.

[0022] P3: Repeat steps P1-P2 to obtain a series of dose rates H1(H12,H13,H14,H15) of the X-rays. i , ┉) and the dose rate H2(H22,H23,H24,H2) of the second electron beam i ,┉);

[0023] P4: The dose rate H1(H11,H12,H13,H14,H1) of the X-ray electron beam. i , ┉) and the dose rate H2(H21,H22,H23,H24,H2) of the second electron beam i The average dose rate of the X-rays is obtained by taking the average value. and the average dose rate of the second electron beam The linear numerical relationship is obtained: That is, we get the value of K.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The present invention generates X-rays by striking a scraper with a first electron beam, and simultaneously tests the X-rays. The dose rate of the second electron beam is obtained by testing the dose rate of the X-rays. The method is novel.

[0026] 2. X-rays are generated by striking the beam scraper with the first electron beam. The X-rays are simultaneously tested and processed by the dose monitoring system to obtain the dose value of the second electron beam. This process does not affect the treatment process and can monitor the dose online, improving the convenience and accuracy of the treatment.

[0027] 3. Only one K value determination is needed before treatment, which enables continuous and multiple monitoring during the treatment process, making the operation convenient;

[0028] 4. A dual-dose monitoring system is adopted to ensure the effectiveness of the dose monitoring system in the event of a failure of one of the dose monitoring systems, thereby improving patient safety. Attached Figure Description

[0029] One or more embodiments are exemplarily illustrated by pictures in the corresponding drawings. These exemplifications do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements. Unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0030] Figure 1 This is a basic structural block diagram of the medical accelerator of this application;

[0031] Figure 2 This is a schematic diagram of the structure of the accelerator tube, beam needle and dose monitoring system in a medical accelerator in one embodiment;

[0032] Figure 3 This is a cross-sectional view of the scraper in one embodiment;

[0033] Figure 4 This is a cross-sectional view of the scraper in another embodiment;

[0034] Figure 5 This is a schematic diagram of the bellows structure in one embodiment;

[0035] Figure 6 This is a schematic diagram of the structure of the accelerator tube, beam needle, and dose monitoring system in a medical accelerator according to another embodiment;

[0036] Figure 7 For use Figure 2 A step diagram illustrating the dosage monitoring method using a dosage monitoring system;

[0037] Figure 8 This is a schematic diagram of the arrangement of the dose detection system when determining the K value in one embodiment;

[0038] Figure 9 A diagram illustrating the steps to determine the value of K;

[0039] Reference numerals: 1-Medical accelerator, 2-Electron gun control power supply, 3-Electron gun, 4-Acceleration tube, 5-Magnetron, 6-Modulator, 7-Beam tube, 8-Beam scraper, 801-Center hole, 9-Bellbell, 10-Beam needle, 11-Elastic channel tube, 12-Flange, 13-Bolt, 14-Dose probe, 15-Data processing system, 14a-First dose probe, 15a-First data processing system, 14b-Second dose probe, 15b-Second data processing system, 14c-Third dose probe, 15c-Third data processing system, 16-Dose detector. DETAILED DESCRIPTION

[0040] To further understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] It should be noted that the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," or "third" may explicitly or implicitly include one or more of that feature. The terms "front end" or "exit end" refer to the end closer to the beam tip when the device or equipment of this application is faced with the reader; "rear end" or "inlet end" refers to the end furthest from the beam tip when the device or equipment of this application is faced with the reader.

[0042] This invention provides a medical accelerator 1, please refer to... Figure 1-2 The system includes an electron gun control power supply 2, an electron gun 3, an accelerating tube 4, a magnetron 5, a modulator 6, a beam channel 7, a beam scraper 8, a bellows 9, and a beam needle. The electron gun control power supply 2 controls the injection voltage of the electron gun 3. The electron gun 3 outputs an electron beam, and the accelerating tube 4 accelerates the electron beam output from the electron gun 3 before outputting it through the beam needle. The modulator 6 controls the magnetron 5. The magnetron 5 is connected to the accelerating tube 4 via a waveguide chain. The rear end of the beam channel 7 is fixedly connected to the center of the front end of the accelerating tube 4. The beam channel 7, the beam scraper 8, the bellows 9, and the beam needle are sequentially and detachably connected, sharing a central axis and forming a straight channel for the electron beam to travel through. The inner diameter of the beam scraper 8 is smaller than the inner diameter of the beam channel 7.

[0043] The treatment process of the present invention is as follows: the beam needle 10 is introduced into the tumor lesion site in the human body through a cannula (not shown) pre-set on the human body, the electron gun 3 generates an electron beam, which is accelerated by the accelerator tube 4 and finally output through the beam needle 10. The electron beam hits the tumor lesion site and ablates the tumor.

[0044] The treatment process of the present invention can also be as follows: the tumor lesion site is exposed by means of surgery, the beam needle 10 is introduced into the tumor lesion site in the human body, the electron gun 3 generates an electron beam, which is accelerated by the accelerator tube 4 and finally output through the beam needle 10. The electron beam hits the tumor lesion site and ablates the tumor.

[0045] In this embodiment, the waveguide chain is a soft waveguide. Soft waveguides have good flexibility and can withstand a certain degree of bending, stretching and compression. With the accelerating tube 4 and the magnetron 5 set separately, the transmission of the electron beam is guaranteed.

[0046] In order to enable the electron beam to be transmitted smoothly from the beam needle 10, a focusing coil is set on the outer periphery of the connection structure between the accelerating tube 4 and the beam needle 10, which is beneficial to effectively guide the movement path of the electron beam and ensure that the electron beam is focused on the axis of the beam needle 10.

[0047] For further details, please refer to... Figure 3-4 The scraper 8 is a cylinder with a central hole 801.

[0048] Furthermore, the scraper 8 is made of lead.

[0049] For further details, please refer to... Figure 4 The cylinder contains an inner ring.

[0050] Furthermore, the inner ring is made of solid water or graphite.

[0051] X-ray generation principle: Brematuration of electrons. High-energy electrons bombard metals in a vacuum. When the electrons approach the atomic nucleus, they interact with the Coulomb field of the nucleus, causing the electrons to deflect and decelerate rapidly. The energy is converted into radiation, producing X-rays.

[0052] Since the dose of the electron beam must be monitored during the treatment process, this invention generates X-rays by partially impacting the scraper 8 with the electron beam, and the X-rays are tested simultaneously without affecting the treatment process, thus enabling online dose monitoring.

[0053] For further details, please refer to [link / reference]. Figure 5 The corrugated pipe 9 includes an elastic channel pipe 11, two flanges 12 and at least three sets of bolts 13.

[0054] Furthermore, the shape of the elastic channel tube 11 can be adjusted by changing the position of the nut in the bolt 13. For example, shortening the distance between the nut and the bolt head at a certain position can cause the elastic channel tube 11 to shift towards that position.

[0055] Furthermore, the outlet end of the beam needle 10 is a sealed end.

[0056] By adopting the above technical solution, the internal environment of the entire accelerator is kept in a vacuum environment, enabling low-loss electron transmission in a vacuum.

[0057] In this embodiment, the sealing end is a non-magnetic metal sheet, preferably a titanium or beryllium sheet. The thickness of the sealing end is less than 200 μm. Long-term experiments and research have shown that if the sealing end is too thick, electrons cannot pass through. When titanium or beryllium sheets are used as the sealing material, electron passage is better and electron attenuation is less, thus ensuring both effective electron throughput and a sealed internal space.

[0058] This invention uses a dose detector to test the dose; please refer to [reference needed]. Figure 2The dose detector 16 includes a dose probe 14 and a data processing system 15. The head end of the first dose probe 14a is opposite to the side of the scraper 8 and is located on the same central axis. The first data processing system 15b processes the signal monitored by the first dose probe 14a to obtain the dose of the second electron beam.

[0059] Specifically, the dose detector 16 in this embodiment includes a finger-shaped ionization chamber, preferably a UNIDOS E dosimeter manufactured by PTW GmbH, Germany. The UNIDOS E dosimeter can monitor the signal at the beam scraper 8 to directly obtain the X-ray dose; similarly, the UNIDOS E dosimeter can monitor the signal at the exit of the beam needle 10 to directly obtain the dose of the second electron beam.

[0060] The principle of measuring absorbed dose using a finger-shaped ionization chamber is as follows: First, the ionization charge generated by ionizing radiation is measured. Then, the average ionization energy of the air is used to calculate and convert it into the energy deposited by ionizing radiation, i.e., the absorbed dose.

[0061] The principle of absorbed dose measurement: When X-rays pass through a penetrating ionization chamber, the gas molecules inside the chamber are ionized, producing positive ions and electrons. Under the influence of an electric field, a weak current signal (10) is generated. -8 A) Its magnitude is directly proportional to the intensity of X-rays. By sending this signal to a preamplifier for processing, the intensity of the X-rays, i.e., the dose rate, can be measured. This method is reliable and provides accurate data detection.

[0062] This invention generates X-rays by striking the scraper 8 with a first electron beam, and simultaneously tests the X-rays without affecting the treatment process, enabling online dose monitoring.

[0063] For safety reasons, to avoid the dose detector 16 malfunctioning, in another technical solution, two sets of dose detectors 16 are set up. Both sets of dose detectors 16 can obtain the dose rate. If one set of dose detectors 16 malfunctions, the other set can continue to work. In addition, the dose rate data of the two sets can be compared to examine the stability of the data.

[0064] Please see Figure 6 The first set of dose detectors 16 includes a first dose probe 14a and a first data processing system 15a. The second set of dose detectors 16 includes a second dose probe 14b and a second data processing system 15b. The first dose probe 14a transmits data to the first data processing system 15a, and the second dose probe 14b transmits data to the second data processing system 15b.

[0065] This invention also provides a dose monitoring method for measuring any of the above-mentioned technical solutions in a medical accelerator; please refer to [link / reference]. Figure 7 This includes the following steps:

[0066] S1: The first electron beam strikes the beam scraper 8 to generate X-rays, and the first dose probe collects the X-ray signal;

[0067] S2: After the first dose probe completes signal collection, the first data processing system processes the signal to obtain the dose rate H of the X-rays. a ;

[0068] S3: The dose H of X-rays from the first data processing system a The data is further processed to obtain the dose H of the second electron beam passing through the beam needle. b .

[0069] Preferably, in step S3, the dose rate H of the second electron beam b With the dose rate H of the X-rays a There exists a linear numerical relationship: H b =KH a .

[0070] The dose monitoring method is used to indirectly obtain the dose of the second electron beam used for treatment by monitoring the dose of the first electron beam during treatment.

[0071] Figure 8 This is a schematic diagram of the arrangement of the dose detection system when determining the K value in one embodiment.

[0072] For further details, please refer to... Figure 9 The steps for determining the value of K are as follows:

[0073] P1: The first electron beam strikes the beam scraper 8 to generate X-rays, and the first dose probe 14a collects the X-ray signal; the second electron beam passes through the beam needle, and the third dose probe 14c collects the signal of the second electron beam.

[0074] P2: After the first dose probe 14a finishes collecting the X-ray signal, the first data processing system 15a processes the X-ray signal to obtain the dose rate H11 of the X-ray; after the third dose probe 14c finishes collecting the signal of the second electron beam, the third data processing system 15c processes the signal of the second electron beam to obtain the dose rate H21 of the second electron beam.

[0075] P3: Repeat steps P1-P2 to obtain a series of dose rates H1(H12,H13,H14,H15) of the X-rays. i , ┉) and the dose rate H2(H22,H23,H24,H2) of the second electron beam i ,┉);

[0076] P4: The dose rate H1(H11,H12,H13,H14,H1) of the X-rays. i , ┉) and the dose rate H2(H21,H22,H23,H24,H2) of the second electron beam i The average dose rate of the X-rays is obtained by taking the average value. and the average dose rate of the second electron beam The linear numerical relationship is obtained: That is, we get the value of K.

[0077] Determining the K value is equivalent to establishing a mathematical relationship between the X-ray dose rate and the dose rate of the second electron beam, and needs to be done before treatment.

[0078] To reduce errors in dose testing results, the distances between the first dose probe 14a and the outlet end on the side of the scraper 8, the distances between the second dose probe 14b and the outlet end on the side of the scraper 8, and the distances between the third dose probe 14c and the outlet end of the beam needle 10 are equal and kept constant.

[0079] This invention generates X-rays by striking the beam scraper 8 with a first electron beam, and simultaneously tests the X-rays to obtain the dose rate of the second electron beam at the exit end of the beam needle. This does not affect the treatment process and enables online monitoring of the dose of the second electron beam (used for treatment).

[0080] Example 1

[0081] Before treatment, the above steps P1-P4 were performed, and the test data are shown in Table 1.

[0082] Table 1. Test results of H1 and H2 before treatment (unit: Gy / s)

[0083]

[0084]

[0085] By processing the test results of H1 and H2, K = 79.426 was obtained.

[0086] Example 2

[0087] During treatment, dose monitoring is performed according to steps S1-S3, and the X-ray dose rate H... a Test value and dose rate H of the second electron beam b The calculated values ​​are shown in Table 2.

[0088] Table 2. Test results of H1 and H2 during treatment (unit: Gy / s)

[0089] Number of tests <![CDATA[H a Test value]]> <![CDATA[H b Calculated value Number of tests <![CDATA[H a Test value]]> <![CDATA[H b Calculated value 1 1.03 81.81 14 1.02 81.01 2 1.01 80.22 15 0.98 77.84 3 0.99 78.63 16 0.99 78.63 4 0.99 78.63 17 1.03 81.81 5 1.02 81.01 18 1.00 79.43 6 0.98 77.84 19 1.02 81.01 7 0.97 77.04 20 0.98 77.84 8 1.00 79.43 21 0.99 78.63 9 1.03 81.81 22 1.03 81.81 10 0.99 78.63 23 1.00 79.43 11 1.02 81.01 24 0.99 78.63 12 1.00 79.43 25 0.97 77.04 13 1.03 81.81

[0090] This embodiment calculates the dose rate of the second electron beam (used for treatment) by monitoring the dose rate of the first electron beam, and implements dose rate monitoring without affecting the treatment.

[0091] This invention generates X-rays by striking the beam scraper 8 with a first electron beam and simultaneously testing the X-rays. Only calibration is required before treatment to test the dose rate of the second electron beam at the exit end of the beam needle. The dose measurement steps of this invention are simple, do not affect the treatment process, and enable online dose monitoring.

[0092] For those skilled in the art, the embodiments should be considered exemplary and non-limiting. The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered to be within the scope of this specification. Therefore, it is intended to include all changes that fall within the meaning and scope of the equivalents of the claims within the present invention.

Claims

1. A dose monitoring method for measuring the dose of a medical accelerator, characterized in that: The medical accelerator comprises an electron gun control power supply, an electron gun, an accelerating tube, a magnetron, a modulator, a beam pipe, a beam scraper, a bellows and a beam needle; the electron gun control power supply is used to control the electron gun injection voltage; the electron gun is used to output an electron beam, and the accelerating tube is used to accelerate the electron beam output by the electron gun and output it through the beam needle; the modulator is used to control the magnetron; the magnetron is connected to the accelerating tube through a waveguide chain; the rear end of the beam pipe is fixedly connected to the front end center of the accelerating tube; the beam pipe, the beam scraper, the bellows and the beam needle are detachably connected in sequence, and the four have a common central axis and are connected to form a straight line channel for the electron beam to be transmitted in the straight line channel; the inner aperture of the beam scraper is smaller than the inner aperture of the beam pipe; the dose monitoring method comprises the following steps: S1: The first electron beam hits the beam scraper to generate X-rays, and the first dose probe collects X-ray signals; S2: After the first dose probe has collected the signal, the data processing system processes the signal to obtain the dose rate H of the X-ray a ; S3: The data processing system is responsible for the X-ray dose rate H a The data is further processed to obtain the dose rate H of the second electron beam passing through the beam needle. b ; Wherein, the dose rate H of the second electron beam in step S3 is b With the X-ray dose rate H a There is a linear numerical relationship: H b =KH a ; The steps for determining the K value are as follows: P1: The first electron beam hits the beam scraper to generate X-rays, and the first dose probe collects the X-ray signal; the second electron beam passes through the beam needle, and the third dose probe collects the signal of the second electron beam passing through the beam needle; P2: The first dose probe has completed collecting X-ray signals, and the first data processing system processes the X-ray signals to obtain the X-ray dose rate H11; the third dose probe has completed collecting the second electron beam signal, and the third data processing system processes the second electron beam signal to obtain the second electron beam dose rate H21; P3: Repeat steps P1-P2 to obtain a series of X-ray dose rates H1 (H12, H13, H14, H1 i ,┉) and the dose rate of the second electron beam H2 (H22, H23,H24,H2 i ,┉); P4 sets the dose rate H1 (H11, H12, H13, H14, H1 i , ┉) and the dose rate H2 of the second electron beam (H21, H22, H23, H24, H2 i , ┉) take the average value to obtain the average dose rate of the X-ray and the average dose rate of the second electron beam , we get a linear numerical relationship: =K , that is, the value of K is obtained.

2. The dose monitoring method according to claim 1, characterized in that: The beam scraper in the medical accelerator is a cylinder with a central hole.

3. The dose monitoring method according to claim 2, characterized in that: The beam scraper is made of lead.

4. The dose monitoring method according to claim 2, characterized in that: The interior of the cylinder in the medical accelerator includes an inner ring.

5. The dose monitoring method according to claim 4, characterized in that: The material of the inner ring is solid water or graphite.

6. The dose monitoring method according to claim 1, characterized in that: The bellows in the medical accelerator comprises an elastic channel tube, two flanges and at least three sets of bolts.

7. The dose monitoring method according to claim 6, characterized in that: The shape of the elastic channel tube can be adjusted by adjusting the position of the nut in the bolt.

8. The dose monitoring method according to claim 1, characterized in that: The exit end of the beam needle in the medical accelerator is a sealed end.

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