Cold cathode X-ray tubes for brachytherapy

Abstract

The present invention provides a cold cathode X-ray tube for brachytherapy, relating to the technical field of nanomaterial X-ray tube design and use. The X-ray tube includes a tube shell, an anode material and a cathode material disposed within the tube shell, and uses carbon nanotubes as the cathode material. The anode material is connected to a micro-heat dissipation structure, and the cathode material is connected to an external power supply. A grid is also provided near the cathode. By adjusting the current and voltage, dwell time, and dwell position, the X-ray beam intensity, beam direction, and X-ray source position can be adjusted, thereby achieving brachytherapy. The present invention overcomes the shortcomings of the prior art and designs a radioactive source for use in the human body. The angle and energy of the X-rays emitted by the tube can be selected and adjusted, and can significantly improve and control the radiotherapy of various malignant tumors.

Description

Technical Field

[0001] The present invention relates to the technical field of design and use of nanomaterial X-ray tubes, and in particular to a cold cathode X-ray tube for brachytherapy. Background Art

[0002] Radiotherapy is widely used in the treatment of malignant tumors, using the property of ionizing radiation to induce apoptosis in tumor cells to kill tumors. Brachytherapy is widely used in common tumors such as cervical cancer, breast cancer, prostate cancer, head and neck tumors, esophageal cancer, and other gynecological cancers. High-dose rate (HDR) brachytherapy places a tiny radioactive source (Ir-192 gamma source with a half-life of 73.827 days and an activity of 10 Ci or other sources) into the patient's body for irradiation, thereby providing a dose distribution that is as consistent as possible for the tumor target while avoiding radiation toxicity that causes serious side effects on endangered organs. It is a very important radiotherapy method. For example, in the treatment of cervical cancer, it is significantly more effective than external beam radiotherapy in terms of tumor local control and survival rate.

[0003] Currently, mainstream brachytherapy equipment, operating systems, and radiation sources in China are expensive, leading to complex procedures for clinicians. Ir-192 sources are also expensive, and due to their 73.827-day half-life, they need to be replaced every three months, resulting in high costs and high consumption. Furthermore, the radiation sources used in brachytherapy have a fixed gamma energy and a fixed, unchangeable radiation penetration range, which is not optimal for the patient's target area. For example, 22% of the photons (also known as "gamma rays") emitted by an Ir-192 source have energies as high as 468 keV, inevitably irradiating many healthy areas of the patient's body far from the target area. Current brachytherapy dose algorithms are limited to adjusting the source's position and dwell time, and cannot utilize the more advanced intensity-modulated radiotherapy (IMRT) methods commonly used in external beam radiation therapy to control the energy, direction, and shape of the radiation. Furthermore, even when not in use, radionuclides must be shielded to protect personnel, making operation cumbersome and difficult to carry. Furthermore, Ir-192 production relies on nuclear reactor facilities, presenting significant cost and nuclear safety challenges.

[0004] Radiation physics shows that gamma rays from radioisotopes are essentially the same as "X-ray" photons. The first clinically used X-ray tubes used a high-temperature tungsten cathode, which heated ions and emitted electrons. These electrons were then attracted by an electric field to an anode (usually made of tungsten). X-ray photons are produced during collisions between the electrons and the anode, and the energy they ultimately acquire is determined by the potential difference between the cathode and the anode. This potential controls the maximum energy of the X-ray photons, and thus their penetration depth into human tissue (a key factor in ensuring radiation dose distribution around the tumor volume). Furthermore, the anode / cathode arrangement and angle can direct radiation in the ideal direction, effectively targeting asymmetric tumor cell clusters. Finally, X-ray devices only emit radiation when powered, making them more convenient and safer to operate than isotope sources. Users also do not need to obtain a government radioactive material license, avoiding the thorny issue of radioisotope production. However, traditional X-ray tubes are large, have poor temporal resolution (due to slow thermal ion emission), have a short lifetime, and require cooling of the high-temperature tungsten cathode for miniaturization. At the same time, in order to achieve the dose requirements of "intensity modulated" brachytherapy, X-ray devices need to have flexible electronic control characteristics.

[0005] Early work has demonstrated the feasibility of producing X-ray radiation from carbon nanotubes. 7 When an electric field of 10 V / m is applied to a solid surface, electrons within the solid are ejected into the vacuum. This phenomenon, known in X-ray generation as "field emission" or "cold cathode emission," is a result of quantum mechanical tunneling. However, until the discovery of nanotubes by Iijima in 1991, such high electric fields posed a significant engineering challenge. In 1995, Rinzler et al. first reported field emission from a single multi-walled nanotube (MWNT). Nanotubes have extremely small ratios of the tip radius of curvature to their length, resulting in a significant enhancement of the electric field at the tip. As observed by Ajayan and Zhou in 2000, the effective field at these locations is often several orders of magnitude greater than the applied field, and due to the large enhancement factor β, the threshold field for field emission, Vth, can be very low. Nanotube-based field emitters have proven superior to conventional radiation sources and have rapidly found applications in a variety of applications, including flat-panel displays. The application of field emission in X-ray production requires exceptionally high and stable current densities. Current densities exceeding 1 μA (>10 6 A / cm 2The researchers conducted similar measurements on single CNTs with closed ends and clean surfaces, ultimately demonstrating that single carbon nanotube electron emitters do exhibit Fowler-Nordheim behavior, with a work function of 5.1±0.1 eV. For a macroscopic cathode, the peak emission current of a 9 cm cathode with a pulse width of 1 μs and an anode voltage of 200 kV was 3000 A. In recent years, many scholars have independently verified some of the characteristics exhibited in electron field emission, including high field emission rates, narrow electron energy spread, rapid control of X-ray generation, low reactivity to residual gases, and low power and cooling requirements.

[0006] As for X-ray sources, existing commercial nanomaterial-based X-ray sources are large in size, suitable for external irradiation, and have low popularity. Existing commercial miniature X-ray sources are implemented differently, do not use nanomaterials, and have non-adjustable voltage. Existing patented technologies for nanomaterial-based miniature X-ray sources do not address both temperature control in the human body and practical applications in afterloading radiotherapy.

[0007] The application number for nanomaterial X-ray tubes is 201210434550.5, which discloses an X-ray tube and its preparation method, which details the preparation method and improvement technology of submillimeter-scale tubes, but does not mention their application in radiotherapy. X The Korean patent details the design of the catheter and discloses its potential applications in tumor treatment. However, its structural configuration still makes it difficult to select the angle and energy of the radiation, which poses significant challenges to its practical application. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention provides a cold cathode X-ray tube for brachytherapy. Designed for use as a radioactive source within the human body, the present invention allows for selection and adjustment of the angle and energy of the X-rays emitted by the tube. This technology can significantly improve and control the radiotherapy of various malignant tumors, effectively reducing the cost of traditional treatment equipment and enhancing the safety of radiotherapy.

[0009] To achieve the above objectives, the technical solution of the present invention is implemented through the following technical solutions:

[0010] A cold cathode X-ray tube for brachytherapy comprises a tube shell, an anode material and a cathode material arranged inside the tube shell, and nano-carbon tubes are used as the cathode material. In response to thermal management requirements (i.e., the device is maintained at a temperature 10°C higher than the ambient temperature), a cooling device based on micro-electromechanical systems (MEMS) technology is designed for the X-ray tube, i.e., the anode material is connected to a micro heat dissipation structure, the cathode material is connected to an external power supply, and a grid is set near the cathode (the device is grounded to avoid high voltage between the grid and the nano-emitter). The X-ray beam intensity, beam direction and X-ray source position are adjusted by adjusting the current and voltage, the dwell time and the dwell position, thereby achieving brachytherapy.

[0011] Preferably, the tube shell material is a low-z ceramic material, and the radius of the tube shell is 5-8 mm, and the tube shell material is evacuated through high vacuum tube technology when used.

[0012] Preferably, the anode material is tungsten, and the thickness of the tungsten anode is 4-5 μm.

[0013] Preferably, the grid is fixedly placed near the cathode to provide voltage as an electronic switch for electron field emission, and the grid reserves 80% of the space for electrons to pass through.

[0014] Preferably, other nanomaterials such as graphene, nano-fiber, nano-rod, nano-needle and nano-pin are used instead of carbon nanotubes as cathode materials.

[0015] The present invention provides a cold cathode X-ray tube for brachytherapy, which has the following advantages over the prior art:

[0016] A novel micro X-ray tube based on a carbon nanotube field emission cold cathode structure is provided for the treatment of common tumors such as cervical cancer, breast cancer, prostate cancer, head and neck tumors, esophageal cancer, and other gynecological cancers, as well as other applications requiring in vivo radiation exposure, such as the use of a microradiation source in cardiac interventional therapy, thereby replacing traditional Ir-192 radionuclide therapy procedures. The micro X-ray tube based on a carbon nanotube field emission "cold cathode" structure, along with its accompanying radiation dose algorithm and inverse optimization treatment plan, offers the following advantages over traditional Ir-192 radionuclide therapy systems:

[0017] (1) There is no need to frequently replace the Ir-192 radioactive source, thus avoiding dependence on imported sources and reducing treatment costs.

[0018] (2) No radiation shielding is required, making operation safer and more convenient.

[0019] (3) It is easy to carry and use in remote areas, and has lower cost.

[0020] (4) The irradiation depth and direction can be adjusted according to the shape and location of the tumor, which can further improve the lethality of the tumor target area and reduce side effects.

[0021] (5) Compared with existing X-ray tube technology: the current and voltage can be adjusted to achieve intensity modulation, control the temperature within the acceptable range of the human body, and focus on the use of afterloading radiotherapy (internal irradiation therapy). BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the structure of the X-ray tube in Example 1 of the present invention;

[0023] Figure 2 Schematic diagram of the structure of the X-ray tube in Example 2 of the present invention;

[0024] Figure 3 Schematic diagram of the structure of the X-ray tube in Example 3 of the present invention. DETAILED DESCRIPTION

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0026] Preparation of carbon nanotubes:

[0027] (1) Using ethylene as a carbon source gas, a silicon wafer as a growth substrate, and iron nanoparticles as a catalyst, a carbon nanotube array material is grown on the substrate surface through a chemical vapor deposition process, and its structure is regulated;

[0028] (2) The prepared carbon nanotube array is heat-treated in an air environment at 450°C to separate the carbon nanotube array from the silicon growth substrate. The carbon nanotube array is then transferred to the surface of a metal conductive substrate of a field emission device. The metal substrate and the carbon nanotube array are bonded using conductive silver paste. After high-temperature baking, effective ohmic contact is achieved between the carbon nanotube array and the metal substrate.

[0029] Example 1:

[0030] The cathode material is arranged inside the inner wall of the bulb (see Figure 1 ):

[0031] A spherical device with a radius of about 5-8 mm was set up using a 100 μm thick, stable and strong low-z ceramic material (Al2O3 ceramic) and a high vacuum tube technology was used in 10 6 The tube is emptied under the support, and a nano-carbon tube source array is set on the inner wall of the tube shell as a cathode structure (the CNT source array consists of multiple individually addressable X-ray focuses, which are realized by a gated CNT field emission cathode array, and all the focuses are positioned along a special tungsten target), and the cathode structure is connected to an external power supply structure, allowing an adjustable voltage of 10-50kV to be supplied to the tube, and the size of the nano-cathode base is 200 microns;

[0032] The tungsten anode is arranged in the center of the tube shell in a spherical shape with a thickness of 4-5 μm. The spherical tungsten anode is connected to the heat dissipation channel, and a coolant is arranged inside the heat dissipation channel and is connected to an external power supply.

[0033] A grid was set 50 μm outside the nanocathode (the grid reserved 80% of the space for electrons to pass through), and a 100 V voltage was provided as an electronic switch for electron field emission. The device was grounded to avoid high voltage between the grid and the nanoemitter.

[0034] Example 2:

[0035] Spherical central cathode setup (see Figure 2 ):

[0036] A spherical device with a radius of about 5-8 mm was set up using a 100 μm thick, stable and strong low-z ceramic material (Al2O3 ceramic) and a high vacuum tube technology was used in 10 6 The tube is emptied under the support, and a nano-carbon tube material is set as a cathode in the center of the tube shell, and the cathode structure is connected to an external power supply structure, allowing an adjustable voltage of 10-50kV to be supplied to the tube, and the size of the nano-cathode base is 200 microns;

[0037] The tungsten anode is deposited on the inner wall of the spherical shell with a thickness of 4-5 μm, and the tungsten anode is connected to the heat dissipation channel, and a coolant is set inside the heat dissipation channel and is connected to an external power supply;

[0038] A grid was set 50 μm outside the nanocathode (the grid reserved 80% of the space for electrons to pass through), and a 100 V voltage was provided as an electronic switch for electron field emission. The device was grounded to avoid high voltage between the grid and the nanoemitter.

[0039] Example 3:

[0040] Parallel cylindrical cathode-anode design (see Figure 3 ):

[0041] A cylindrical device with a radius of about 5-8 mm was set up using a 100 μm thick, stable and strong low-z ceramic material (Al2O3 ceramic) and a high vacuum tube technology was used in 10 6 The tube is emptied under the support, and a large cylindrical nano-emitter base (nano-carbon tube) is set as the cathode inside the tube shell, and the cathode structure is connected to the external power supply structure, allowing an adjustable voltage of 10-50kV to be supplied to the tube;

[0042] The tungsten anode is deposited on the inner wall of the inner ring surface of the cylindrical shell with a thickness of 4-5 μm, and the tungsten anode is connected to the heat dissipation channel, and a coolant is set inside the heat dissipation channel and is connected to an external power supply;

[0043] A grid was set 50 μm outside the nanocathode (the grid reserved 80% of the space for electrons to pass through), and a 100 V voltage was provided as an electronic switch for electron field emission. The device was grounded to avoid high voltage between the grid and the nanoemitter.

[0044] In each of the aforementioned embodiments, current is used to modulate X-ray intensity to achieve the asymmetric dose distribution that may be required in the tumor target area. The Al2O3 ceramic housing not only provides mechanical support but also allows X-rays to pass through, preventing harm to patients or healthcare professionals. A nanocathode material is used to provide sufficient nanofield emitters to deliver an X-ray dose rate of approximately 20 Gy / min at a tissue depth of 3 cm.

[0045] At the same time, the electron bombardment of the anode assembly generates excess heat that needs to be dissipated, which can be dissipated and cooled through the heat dissipation channel to keep the temperature within an acceptable range during use.

[0046] The power supply operates in the 10-50 kV voltage range, providing photons with a maximum energy of less than 50 keV, eliminating the shielding issues required for Ir-192 sources used in high-dose-rate (HDR) brachytherapy. The source current and photon beam intensity are modulated to approximate the penetration depth and dose rate characteristics of clinically applicable radionuclides, such as the HDR radioactive seed Ir-192. As a result, dose consistency can be increased. At an operating voltage of 50 kV, the source is designed to produce air kerma intensities ranging from 1400 Gy·cm 2 ·h -l (The tube current is 300 μA, about three times that of a 10 Ci HDRIr-192 source) to 4.7 Gy·cm 2 ·h -l (The tube current is 1μA at this time).

[0047] In summary, the device fabricated by the present invention can provide insights into clinical radiotherapy and facilitate subsequent improvements and development of radiotherapy technology. Furthermore, once the X-ray tube reaches the affected area, the emitted X-rays penetrate human tissue and are detected by the outside world. This allows for imaging, and the information revealed by the imaging can be used to confirm the position of the X-ray tube and conduct medical analysis and research on images captured by X-rays emitted from within the human body, providing a promising direction for medical treatment research.

[0048] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0049] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A cold cathode X-ray tube for brachytherapy, characterized in that: The X-ray tube includes a tube shell, an anode material and a cathode material disposed inside the tube shell, and a nano-carbon tube array is used as the cathode material. The anode material is connected to a micro heat dissipation structure, and the cathode material is connected to an external power supply. A grid is provided 50 μm outside the nano-cathode, and the X-ray beam intensity, beam direction, and X-ray source position are adjusted by adjusting the current and voltage, dwell time, and dwell position, thereby achieving close-range radiotherapy. The cathode material of the X-ray tube is arranged at the center or on the inner wall of the tube; the arrangement of the cathode material at the center of the tube can be made into a spherical central cathode or a parallel cylindrical cathode-anode design; The spherical central cathode is provided with a spherical vacuum shell, and the cathode material is provided in the center of the spherical vacuum shell and connected to an external power supply, and the anode material is deposited on the inner wall of the spherical vacuum shell and connected to a micro heat dissipation structure; The parallel cylindrical cathode-anode design is to set up a cylindrical vacuum tube shell, and the cathode material is set as a large nano-cylindrical nano-emitter base inside the cylindrical vacuum tube shell and connected to an external power supply, and a layer of anode material is deposited on the inner annular surface of the cylindrical vacuum tube shell to connect to the micro heat dissipation structure; The cathode material is arranged inside the inner wall of the tube as follows: a spherical vacuum tube shell is provided, the cathode material is a nano-carbon tube source array composed of multiple individually addressed X-ray foci on the inner wall of the tube shell, and the cathode material is connected to an external power supply, and the anode material is a hollow spherical material arranged in the center of the tube shell and connected to a micro heat dissipation structure.

2. The cold cathode X-ray tube for brachytherapy according to claim 1, wherein: The shell material is a low-z ceramic material, and the radius of the shell is 5-8 mm. The shell material is evacuated through high vacuum tube technology when in use.

3. The cold cathode X-ray tube for brachytherapy according to claim 1, wherein: The anode material is tungsten, and the thickness of the tungsten anode is 4-5 μm.

4. The cold cathode X-ray tube for brachytherapy according to claim 1, wherein: The grid is fixedly placed near the cathode to provide voltage as an electronic switch for electron field emission, and the grid reserves 80% of the space for electrons to pass through.

5. The cold cathode X-ray tube for brachytherapy according to claim 1, wherein: Graphene, nano-fiber, nano-rod, nano-needle and nano-pin are used instead of carbon nanotubes as cathode materials.

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