Intraoperative radiotherapy device based on dual-energy X-ray energy spectrum modulation and energy spectrum modulation method

Abstract

The invention belongs to the field of intraoperative radiotherapy devices, and particularly relates to an intraoperative radiotherapy device based on dual-energy X-ray energy spectrum modulation and an energy spectrum modulation method, the device comprises a cathode structure, an anode cylinder, a target material, a probe and a source applicator; the electron emission source, the cathode structure, the anode cylinder and the probe are sequentially arranged, the electron emission source is located in the cathode structure, the probe is arranged in the source applicator, and a target material is arranged at the end, away from the electron emission source, of the probe; the anode cylinder is provided with a focusing coil and a deflection coil, the focusing coil surrounds the anode cylinder and is used for fully focusing the electron beam, and the deflection coil is used for generating a deflection magnetic field to control the track of the electron beam to bombard different target materials. According to different treatment depths, the magnetic field modulation assembly is used for changing the electron motion trail, and the energy spectrum with the corresponding intensity is output, so that the tumor target region is treated. The device has the characteristics of high energy spectrum adjustment speed, high output energy spectrum intensity and accurate dose delivery.

Description

Technical Field

[0001] The present invention belongs to the field of intraoperative radiotherapy devices, and in particular relates to an intraoperative radiotherapy device based on dual-energy X-ray energy spectrum modulation and an energy spectrum modulation method. Background Art

[0002] Intraoperative radiotherapy (IORT), also known as intraoperative radiotherapy, is a radiotherapy method that delivers a single high-dose irradiation to visible tumors and tumor beds during surgery. Compared with traditional external beam radiotherapy (EBRT) and brachytherapy, intraoperative radiotherapy has many potential advantages, including: (1) while meeting the tumor target dose, intraoperative radiotherapy can reduce the dose to normal tissues and improve the treatment effect; (2) patients can be treated after the tumor is surgically removed, while the traditional fractionated external irradiation method has a long treatment cycle, often requiring several weeks. Therefore, intraoperative radiotherapy can effectively reduce the possibility of tumor cell proliferation while waiting for radiotherapy; (3) intraoperative radiotherapy has the characteristics of a single high-dose irradiation, has better biological effects, is more effective in killing tumor cells, and can reduce the risk of tumor recurrence. Among them, intraoperative radiotherapy based on low-energy X-rays has a compact device structure, is easy to move flexibly in the operating room, and the output X-rays are easy to shield, without the need for radiation-resistant reinforcement of the operating room, and has gradually become an important choice for intraoperative radiotherapy technology.

[0003] In the technical solution based on low-energy X-ray intraoperative radiotherapy, Zeiss proposed using a transmission low-energy X-ray tube as the radiation source, with a tube voltage of 50kV and a gold target. In order to adjust the output energy spectrum, the literature (Impact of spherical applicator diameter on relative biologic effectiveness of lowenergy IORT X-rays: A hybrid Monte Carlo study, 2020) describes the use of spherical applicators with different structures and thicknesses to adjust the output energy spectrum intensity. When treating breast cancer, the applicator is spherical and made of polyetherimide (PEI) with a density of 1.27~1.54g / cm 3 The radius of the ball is between 1.5 and 5 cm. The technicians replace the applicator of the corresponding size according to the depth of the treatment target area. However, while this solution obtains an adjustable energy spectrum, as the size of the applicator increases, the attenuation of the X-ray energy spectrum gradually increases, which in turn leads to a longer treatment time.

[0004] In summary, in view of the continuous demand for precision radiotherapy in tumor treatment, designing an X-ray source with rapidly adjustable output energy spectrum, high radiation intensity, compact device structure, and easy protection is of great significance to promoting the development of intraoperative radiotherapy technology. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides an intraoperative radiotherapy device and an energy spectrum modulation method based on dual-energy X-ray energy spectrum modulation, thereby realizing an intraoperative radiotherapy technology with adjustable energy spectrum and high ray intensity.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] An intraoperative radiotherapy device based on dual-energy X-ray spectrum modulation, the device comprising: an electron emission source, a cathode structure, an anode tube, a target material, a probe and a source applicator; the cathode structure, the anode tube and the probe are arranged in sequence, the electron emission source is located inside the cathode structure, the probe is arranged inside the source applicator, and the target material is arranged at one end of the probe away from the electron emission source; the electron emission source is used to generate initial electrons, the cathode structure and the anode tube are used to generate an accelerating electric field and preliminarily focus the emitted electrons, and the source applicator is used to fit the target material and protect the patient from infection by the device; the anode tube is provided with a focusing coil and a deflection coil, the focusing coil surrounds the anode tube and is used to fully focus the electron beam, and the deflection coil is used to generate a deflection magnetic field to control the trajectory of the electron beam to bombard different targets.

[0008] Furthermore, the target material includes a metal zirconium target material and a metal silver target material, and the metal zirconium target material and the metal silver target material are deposited on a beryllium window by magnetron sputtering, and the beryllium window is located at the probe head.

[0009] Furthermore, the device also includes a first shell and a second shell, and the second shell is located inside the first shell.

[0010] Furthermore, the first shell is made of metal, and the second shell is made of glass.

[0011] Furthermore, the electron emission source is fixed on a ceramic column, and the ceramic column is fixed to a side surface of the first housing.

[0012] Furthermore, an insulating device is provided on the side of the first shell to which the ceramic column is fixed. The material of the insulating device is alumina ceramic, and the ceramic column and the first shell are sealed by the insulating device.

[0013] Furthermore, a cathode structure is disposed at one end of the ceramic column, and the electron emission source is located inside the cathode structure.

[0014] Furthermore, the second shell is connected to the anode cylinder via a kovar structure, and the kovar structure is used to fix the positions of the anode cylinder and the second shell.

[0015] Furthermore, the applicator is spherical, made of polyetherimide PEI, and has a thickness of less than 1.5 cm.

[0016] The present invention also provides an energy spectrum modulation method, using the above-mentioned intraoperative radiotherapy device based on dual-energy X-ray energy spectrum modulation, the method comprises the following steps:

[0017] Under the condition of not loading the deflection magnetic field, adjusting the focusing magnetic field size, obtaining the focusing magnetic field intensity when the target focus is the smallest, and obtaining the focusing magnetic field intensity parameter;

[0018] Keep the intensity of the focusing magnetic field unchanged, adjust the size of the deflection magnetic field, change the trajectory of the electron beam in the deflection magnetic field area, and finally bombard the corresponding target material when the electron beam is transported inside the probe; obtain the energy spectrum output intensity information of the electron beam targeting focus all located in the metal zirconium target area and the metal silver target area, and establish the deposition dose distribution curves of the two output energy spectra at different depths in the water model;

[0019] According to the depth characteristics of the target area to be treated and the deposition dose distribution curve, the target material bombarded by the electron beam trajectory is adjusted to achieve intensity modulation of the output energy spectrum.

[0020] Furthermore, when the depth of the target area to be treated is shallow, the X-ray energy spectrum generated by bombarding the metal zirconium target with an electron beam is used;

[0021] When the depth of the target area to be treated is deep, the X-ray energy spectrum generated by electron beam bombarding the metal silver target is generated.

[0022] The intraoperative radiotherapy method based on the device is: according to the characteristics of the tumor target area to be irradiated, the output energy spectrum intensity is adjusted. Since the average energy of the output energy spectrum generated by the electron beam bombarding Zr is lower than the output energy spectrum of the Ag target, the penetration depth of the Zr target energy spectrum is small. Therefore, when irradiating the shallow target area, the deflection magnetic field is controlled to make the electron bombard the metal zirconium target material to produce an output energy spectrum, and when irradiating the deep target area, the characteristic energy spectrum of the metal silver target material is output. According to the different treatment depths, the present invention uses a magnetic field modulation component to change the trajectory of electron movement, output an energy spectrum of corresponding intensity, and thus treat the tumor target area. It has the characteristics of fast energy spectrum adjustment speed, high output energy spectrum intensity, and precise dose delivery.

[0023] Beneficial Effects

[0024] The intraoperative radiotherapy device of the present invention has adjustable output spectrum intensity and fast modulation speed. Aiming at the radiation dose requirements of target areas at different depths during intraoperative radiotherapy, the intraoperative radiotherapy device of the present invention adopts a dual-target X-ray tube, controls the electron beam to bombard different target areas by changing the deflection magnetic field to generate an output spectrum, and has the characteristics of adjustable spectrum and fast modulation speed.

[0025] The intraoperative radiotherapy device described in the present invention has low attenuation of the output energy spectrum intensity. The present invention uses a dual-target X-ray tube in conjunction with a 1cm thick applicator to achieve effective modulation of the output energy spectrum intensity. Compared with the traditional method of changing the output energy spectrum intensity by using spherical applicators of different thicknesses of 1.5 to 5cm (the thicker the applicator, the stronger the attenuation of the output X-rays), the energy spectrum modulation method of the present invention does not need to adjust the thickness of the spherical applicator, and has high output energy spectrum intensity, low attenuation, precise dose delivery, and fast modulation speed. When the tumor treatment target area changes and the output energy spectrum characteristics need to be adjusted accordingly, the needs of precision radiotherapy can be met. The present invention controls the trajectory of the electron beam by changing the deflection magnetic field intensity, so that electrons bombard different target materials to produce an output energy spectrum with adjustable intensity, and uses a fixed thickness of 1cm to absorb low-energy X-rays with energy less than 8 keV and ensure the safety of treatment. There is no need to change the size of the applicator, which reduces the error caused by loading and unloading the applicator structure. At the same time, a smaller thickness applicator is used to reduce the intensity attenuation of the output X-ray after passing through the applicator. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the overall structure of the X-ray source of the present invention.

[0027] Figure 2 This is a diagram of the target focus size when the electrons of the X-ray source of the present invention are not deflected.

[0028] Figure 3 It is a diagram of the transport trajectory of the electron beam of the X-ray source after deflection of the present invention.

[0029] Figure 4 This is a schematic diagram of target shooting after electron beam deflection.

[0030] Figure 5 It is the focus distribution diagram of the electron bombardment target of the present invention. Figure a is the focus distribution diagram of the electron bombardment Zr target of the present invention; Figure b is the focus distribution diagram of the electron bombardment Ag target of the present invention.

[0031] Figure 6 It is the energy spectrum diagram of electron bombardment of the present invention. Figure a is the energy spectrum diagram produced by electron bombardment of Zr target of the present invention; Figure b is the energy spectrum diagram produced by electron bombardment of Ag target of the present invention.

[0032] Figure 7 It is a normalized dose distribution diagram of the two output energy spectra deposited in a three-dimensional water tank according to the present invention.

[0033] Figure numerals: 1. first shell; 2. ceramic column; 3. electron emission source; 4. insulating device; 5. second shell; 6. cathode structure; 7. kovar structure; 8. anode cylinder; 9. focusing coil; 10. deflection coil; 11. probe; 12. spherical applicator; 13. chromium nitride; 14. metal zirconium target; 15. metal silver target; 16. metal nickel; 17. beryllium window. DETAILED DESCRIPTION

[0034] The present invention will now be described in further detail with reference to the accompanying drawings.

[0035] like Figure 1 As shown, an intraoperative radiotherapy device based on dual-energy X-ray spectrum modulation includes: an electron emission source 3, a cathode structure 6, an anode tube 8, a target material, a probe 11 and a source applicator 12. The cathode structure 6, the anode cylinder 8 and the probe 11 are arranged in sequence, the electron emission source 3 is located inside the cathode structure 6, the probe 11 is arranged inside the source applicator 12, and a target material is arranged at one end of the probe 11 away from the electron emission source 3; the electron emission source 3 is used to generate initial electrons, the cathode structure 6 and the anode cylinder 8 are used to generate an accelerating electric field and preliminarily focus the emitted electrons, the anode cylinder 8 is provided with a focusing coil 9 and a deflection coil 10, the focusing coil 9 surrounds the anode cylinder and is used to fully focus the electron beam, and the deflection coil 10 is used to generate a deflection magnetic field to control the trajectory of the electron beam to bombard different targets; the target materials include a metal zirconium target material 14 and a metal silver target material 15, the metal zirconium target material 14 and the metal silver target material 15 are deposited on a beryllium window 17 by magnetron sputtering, the probe 11 is connected to the anode cylinder 8, the beryllium window 17 and the target material are located at the head of the probe 11, and the source applicator 12 is used to fit the target area and protect the patient from device infection.

[0036] The device further comprises a first housing 1 and a second housing 5, wherein the second housing 5 is located inside the first housing 1, the first housing 1 is made of metal, preferably 304 stainless steel, and the second housing 5 is made of glass. The second housing 5 is used to fix the ceramic column 2 and the electron emission source 3.

[0037] The electron emission source 3 is made of a round tungsten wire and is fixed on a ceramic column 2, and the ceramic column 2 is fixed on the side of the first shell 1; the side of the first shell 1 where the ceramic column 2 is fixed is provided with an insulating device 4, and the insulating device material is alumina ceramic. The first shell 1 and the ceramic column 2 are sealed and connected through the insulating device 4, and the insulating device is used to isolate high-voltage components, protect the safe operation of the X-ray tube, and prevent electrostatic breakdown; the beryllium window 17 is made of metal beryllium, and one end of the ceramic column 2 is provided with a cathode structure 6, and the cathode structure 6 is made of 304 stainless steel. An accelerating electric field is generated between the cathode structure 6 and the anode tube to accelerate the electrons, and the cathode structure is groove-shaped and is used to preliminarily focus the emitted electron beam; the second shell 5 and the anode tube 8 are connected by a kovar structure 7 The kovar structure 7 is used to fix the position of the anode cylinder 8 and the second shell 5; the anode cylinder 8 is made of copper, the focusing coil 9 and the deflection coil 10 are both made of red copper enameled wire, the enameled wire diameter is 0.25 mm, the focusing coil is wound with 600 turns, the deflection coil is wound with 50 turns, the source applicator 12 is spherical, and the material is polyetherimide PEI, and the thickness of the source applicator 12 is less than 1.5 cm; the probe 11 is composed of chromium nitride 13 and metal nickel 16, and the chromium nitride and metal nickel are used to maintain the mechanical strength of the probe and maintain the vacuum inside the ray tube, the beryllium window 17 is located at the head of the probe 11, and the metal zirconium target 14 and the metal silver target 15 are deposited on the beryllium window 17 by magnetron sputtering, the thickness of the metal zirconium target is 6 μm, and the thickness of the metal silver target is 10 μm. The first shell is 15 cm long and 8 cm in diameter; the anode tube 8 is 5 cm long and has an inner hole diameter of 6 mm; the probe 11 is 7 cm long and has an inner hole diameter of 4 mm; the beryllium window 17 is 0.5 mm thick; the cathode structure 6 is loaded with negative high voltage, with a maximum value of negative 50 kV; and the anode tube 8 is grounded.

[0038] The energy spectrum modulation method using the above intraoperative radiotherapy device includes the following steps:

[0039] Step 1: Determine the parameters of the focusing magnetic field strength. Keep the intraoperative radiotherapy device based on dual-energy X-ray spectrum modulation running at a maximum tube voltage of 50 kV and a tube current of 0.04 mA. Load current in the focusing coil to generate a focusing magnetic field. The current gradually increases from 0 to 2 A in steps of 0.1 A. Adjust the focusing magnetic field size. At this time, no deflection magnetic field is loaded. Use a CCD camera (charge-coupled device camera) to obtain the target focus information using the pinhole method. Determine the focusing magnetic field strength when the target focus is the smallest. The results are as follows: Figure 2 As shown, under this structure, the minimum focus diameter is 1 mm, the center is located at (0.1 mm, 0 mm), the current loaded on the focusing coil is 1.5 A, and then the focusing magnetic field strength remains unchanged.

[0040] Step 2: Based on the parameters in step 1, load current to the deflection coil and adjust the deflection magnetic field to deflect the electron beam trajectory with a diameter of 1 mm so that it completely bombards the metal zirconium target or metal silver target. Figure 3 As shown in the figure, the electrons are accelerated by the electric field and focused by the focusing magnetic field. The trajectory of the electrons changes in the deflection magnetic field area. The electron beam is transported inside the probe and finally bombards the corresponding target material. The schematic diagram of the target focus is shown in the figure. Figure 4 As shown. When the electron beam target focus is all located in the metal zirconium target area, the intensity information of the output energy spectrum at this time is obtained. Then adjust the deflection magnetic field so that the electron beam target focus is all located in the metal silver target area, and the intensity information of the output energy spectrum at this time is obtained. Figure 5 a shows the focus information when electrons bombard the metal zirconium target. The focus is circular with a diameter of about 1 mm and a center coordinate of (1 mm, -0.5 mm). Figure 5 b shows the focus information when the electrons bombard the metal silver target. The focus is circular with a diameter of about 1 mm and a center coordinate of (-0.9 mm, 0 mm). It can be seen that the electron beam is mainly deflected in a certain axis, achieving the purpose of magnetic field modulation to bombard different target areas. Figure 6 As shown in a, in the output energy spectrum produced by electron bombardment of the Zr target, the characteristic spectrum lines of Zr and the continuous spectrum produced by bremsstrahlung can be seen, with an average energy of 21.6keV and an integrated intensity of 9.6E-04; Figure 6 As shown in Figure b, in the output energy spectrum generated by electron bombardment of the Ag target, the average energy of the output energy spectrum is 23.8keV, and the integrated intensity is 9.14E-04, showing the characteristic spectrum lines of Ag and the continuous spectrum generated by bremsstrahlung. From the above, it can be seen that the characteristic peaks of the initial energy spectrum generated by electron target bombardment still exist after passing through the 1cm source applicator, and the average energy of the energy spectrum generated by electron bombardment of Ag is higher than that of electron bombardment of Zr, while the intensity of the energy spectrum output by the Ag target is lower than that of the electron bombardment of the Zr target.

[0041] Based on the above, a three-dimensional water tank is used to establish the deposition dose curve of the output energy spectrum at different depths underwater, such as Figure 7 The output spectrum deposition percentage depth dose curve is shown, the horizontal axis represents the depth, and the vertical axis takes the initial intensity of electron bombardment of the Zr target as the normalized value 100%. Under the conditions of this embodiment, it can be seen from the dose distribution curve that due to the low average energy of the Zr spectrum, its dose curve drops more than the Ag spectrum. At a depth of 0.5 cm, the deposition doses of the two spectra are the same.

[0042] Step 3: Obtain the depth characteristics of the target area to be treated based on the patient's CT image, record the center of the target area as h (the range of h in intraoperative radiotherapy is usually 0 to 5 cm), and adjust the output time of the two energy spectra. Figure 7As a result, when treating a shallow target area (0-0.5 cm), the lower energy X-ray energy spectrum produced by electron beam bombarding the metal zirconium target is used for treatment; if h is a deep target area (0.5-5 cm), the higher energy X-ray energy spectrum produced by electron beam bombarding the metal silver target is used for treatment; so as to achieve the best treatment effect.

[0043] Compared with the current X-ray intraoperative radiotherapy method that uses a 1.5~5cm-sized applicator to change the output energy spectrum, the intraoperative radiotherapy device and method based on dual-energy X-ray energy spectrum modulation proposed in the present invention, through the design of a dual-target X-ray tube, uses a deflection magnetic field to control the electron trajectory to bombard different target materials to produce two different output energy spectra, combines the deposition dose distribution characteristics of the two energy spectra, and regulates the output of the two energy spectra according to the depth of the target area, with the characteristics of fast modulation speed and accurate dose delivery. At the same time, the use of a thin spherical applicator reduces the attenuation of the material itself to X-rays and reduces the loss of energy spectrum intensity.

[0044] It should be noted that the terms such as "deep layer" and "shallow layer" cited in the invention are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments in their relative relationships should be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0045] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. An intraoperative radiotherapy device based on dual-energy X-ray spectrum modulation, characterized in that: The device comprises: an electron emission source, a cathode structure, an anode tube, a target material, a probe and a source applicator; the cathode structure, the anode tube and the probe are arranged in sequence, the electron emission source is located inside the cathode structure, the probe is arranged inside the source applicator, and a target material is arranged at one end of the probe away from the electron emission source; the electron emission source is used to generate initial electrons, the cathode structure and the anode tube are used to generate an accelerating electric field and preliminarily focus the emitted electrons, and the source applicator is used to fit the target material and protect the patient from infection by the device; the anode tube is provided with a focusing coil and a deflection coil, the focusing coil surrounds the anode tube and is used to fully focus the electron beam, and the deflection coil is used to generate a deflection magnetic field to control the trajectory of the electron beam to bombard different targets.

2. The intraoperative radiotherapy device based on dual-energy X-ray spectrum modulation according to claim 1, characterized in that: The target material comprises a metal zirconium target material and a metal silver target material, and the metal zirconium target material and the metal silver target material are deposited on a beryllium window by magnetron sputtering, and the beryllium window is located at the probe head.

3. The intraoperative radiotherapy device based on dual-energy X-ray spectrum modulation according to claim 1, characterized in that: The device also includes a first housing and a second housing, wherein the second housing is located inside the first housing.

4. The intraoperative radiotherapy device based on dual-energy X-ray spectrum modulation according to claim 3, characterized in that: The first shell is made of metal, and the second shell is made of glass.

5. The intraoperative radiotherapy device based on dual-energy X-ray spectrum modulation according to claim 3, characterized in that: The electron emission source is fixed on a ceramic column, and the ceramic column is fixed on a side surface of the first housing.

6. The intraoperative radiotherapy device based on dual-energy X-ray spectrum modulation according to claim 5, characterized in that: An insulating device is arranged on the side of the first shell where the ceramic column is fixed. The insulating device is made of alumina ceramics. The first shell and the ceramic column are sealed by the insulating device.

7. The intraoperative radiotherapy device based on dual-energy X-ray spectrum modulation according to claim 3, characterized in that: The second shell is connected to the anode cylinder via a kovar structure, and the kovar structure is used to fix the positions of the anode cylinder and the second shell.

8. The intraoperative radiotherapy device based on dual-energy X-ray spectrum modulation according to claim 1, characterized in that: The applicator is spherical, made of polyetherimide PEI, and has a thickness of less than 1.5 cm.

9. A spectrum modulation method, characterized in that: Using the intraoperative radiotherapy device based on dual-energy X-ray spectrum modulation according to any one of claims 1 to 8, the method comprises the following steps: Under the condition of not loading the deflection magnetic field, adjusting the focusing magnetic field size, obtaining the focusing magnetic field intensity when the target focus is the smallest, and obtaining the focusing magnetic field intensity parameter; Keep the intensity of the focusing magnetic field unchanged, adjust the size of the deflection magnetic field, change the trajectory of the electron beam in the deflection magnetic field area, and finally bombard the corresponding target material when the electron beam is transported inside the probe; obtain the energy spectrum output intensity information of the electron beam targeting focus all located in the metal zirconium target area and the metal silver target area, and establish the deposition dose distribution curves of the two output energy spectra at different depths in the water model; According to the depth characteristics of the target area to be treated and combined with the deposition dose distribution curve, the target material bombarded by the electron beam is adjusted to achieve intensity modulation of the output energy spectrum.

10. The energy spectrum modulation method according to claim 9, characterized in that: When the depth of the target area to be treated is shallow, the X-ray energy spectrum generated by electron beam bombarding the metal zirconium target; When the depth of the target area to be treated is deep, the X-ray energy spectrum generated by electron beam bombarding the metal silver target is generated.

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