Side illuminator and method for determining angle and thickness of scattering foil in side illuminator

Abstract

The invention provides a side illuminator and a method for determining the angle and thickness of a scattering foil therein, and belongs to the technical field of radiotherapy equipment.The side illuminator comprises a shell which is of a hollow structure with an opening, a side treatment window and a bottom surface; a scattering foil disposed on a side of the side treatment window and configured to receive the first radiation, scatter the first radiation, and convert a portion of the first radiation into second radiation; and a modulator disposed inside the side treatment window and configured to modulate an intensity of a mixed radiation including the first radiation and the second radiation, and an attenuator disposed inside the side illuminator and configured to attenuate an intensity of mixed radiation including the first radiation and the second radiation. According to the invention, the vertically incident electron beam can be partially converted into the X-ray, the intensity of the electron and X-ray mixed beam is modulated, dose distribution consistent with the shape of a treatment window is formed in the treatment window on the side surface of the illuminator, and the illuminator is used for radiotherapy of tumors distributed in a vertical plane, such as an esophageal cancer postoperative tumor bed.

Description

Technical Field

[0001] The invention relates to the technical field of radiotherapy equipment, and in particular to a side illuminator and a method for determining the angle and thickness of a scattering foil therein. Background Art

[0002] Electron beam is one of the radiation sources used in tumor radiotherapy. It is mostly used for intra-operable radiation therapy (IORT) of abdominal tumors (such as liver and pancreas) and external beam radiotherapy of superficial tumors with planar distribution. The capsule applicator can convert the planar dose distribution produced by the conventional light-limiting tube into a conformal dose distribution of the spherical, prismatic and hemispherical tumor beds of breast cancer and brain tumors after surgery. However, the intraoperative radiotherapy of the vertically distributed tumor bed after esophageal cancer surgery has not yet been solved. Summary of the invention

[0003] The object of the present invention is to provide a side illuminator and a method for determining the angle and thickness of a scattering foil therein, so as to solve at least one technical problem existing in the above-mentioned background technology.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] In one aspect, the present invention provides a side illuminator, comprising:

[0006] a housing having a hollow structure with an opening, a side treatment window, and a bottom surface;

[0007] a scattering foil, disposed on the side of the lateral treatment window, configured to receive the first radiation, scatter the first radiation, and convert a portion of the first radiation into the second radiation; and

[0008] a modulator, disposed inside the side treatment window, configured to modulate the intensity of mixed radiation including the first radiation and the second radiation;

[0009] An attenuator is disposed inside the side illuminator and is configured to attenuate the intensity of mixed radiation including the first radiation and the second radiation.

[0010] Furthermore, the housing is made of metal material to shield radiation in the side areas outside the treatment window and to support the scattering foil and the attenuator.

[0011] Furthermore, the side treatment window is made of a rigid soft tissue equivalent material to support the modulator.

[0012] Furthermore, the scattering foil is located inside the side illuminator, close to the side treatment window, and has an optimized angle and thickness to ensure that a predetermined first radiation scattering angle is achieved while maintaining a predetermined mixed radiation intensity.

[0013] Furthermore, the modulator is located on the inner surface of the side treatment window and has an optimized shape and thickness so that the mixed radiation has a desired intensity distribution on the outer surface of the treatment window.

[0014] Furthermore, the attenuator is located at the bottom end of the side illuminator.

[0015] Furthermore, the attenuator is made of metal material to shield radiation at the bottom end of the applicator.

[0016] In a second aspect, the present invention provides a method for determining the angle of a scattering foil in a side illuminator as described above, comprising:

[0017] N scattering foils are arranged above the side treatment window to scatter and convert the first radiation, N is zero or a positive integer, and each scattering foil has a predetermined thickness and a different angle with the vertical direction of the beam;

[0018] On the surface of the side treatment window, counting the number of electrons and photons on the treatment window;

[0019] The angle with the largest number of electrons and photons is selected as the scattering foil angle.

[0020] In a third aspect, the present invention provides a method for determining the thickness of a scattering foil in a side illuminator as described above, comprising:

[0021] Model a series of scattering foils with different thicknesses and defined angles;

[0022] Calculate the minimum dose on a line at a certain depth from the surface of the side treatment window in a plane perpendicular to the side treatment window and passing through the center of the side treatment window;

[0023] The thickness corresponding to the maximum minimum dose is taken as the scattering foil thickness.

[0024] The beneficial effects of the present invention are as follows: it is capable of converting part of the vertically incident electron beam into X-rays, and modulating the intensity of the mixed beam of electrons and X-rays, so as to form a dose distribution consistent with the shape of the treatment window at the side treatment window of the irradiator, and is used for the radiotherapy of tumors distributed in a vertical plane, such as postoperative tumor bed of esophageal cancer.

[0025] Additional aspects and advantages of the present invention will be given in part in the following description, which will become obvious from the following description, or may be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0027] Figure 1 It is a schematic diagram of the front structural view of the side illuminator described in an embodiment of the present invention.

[0028] Figure 2 It is a schematic diagram of the side structure of the side illuminator described in an embodiment of the present invention.

[0029] Figure 3 This is a schematic diagram of the dose distribution in the area outside the treatment window surface of the side illuminator according to an embodiment of the present invention. Figure 3 (a) is the dose distribution perpendicular to the side treatment window and passing through the center plane of the side treatment window; Figure 3 (b) Dose distribution parallel to the lateral treatment window plane.

[0030] Figure 4 This is a schematic diagram of the percentage depth dose on the central axis at different heights from the top of the side treatment window according to an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below by the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0032] It should be understood by those skilled in the art that unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which this invention belongs.

[0033] It should also be understood that terms, such as those defined in commonly used dictionaries, should be understood to have a meaning consistent with that in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless as defined herein.

[0034] Those skilled in the art will appreciate that, unless otherwise stated, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements and / or groups thereof.

[0035] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory.

[0036] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0037] In the description of this specification, the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present technology and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present technology.

[0038] Unless otherwise clearly specified or limited, the terms "installed", "connected", "connected", and "set" should be understood in a broad sense, for example, they can be fixedly connected or set, or detachably connected or set, or integrally connected or set. For ordinary technicians in this field, the specific meanings of the above terms in this technology can be understood according to specific circumstances.

[0039] To facilitate understanding of the present invention, the present invention is further explained below with reference to specific embodiments in conjunction with the accompanying drawings, and the specific embodiments do not constitute a limitation on the embodiments of the present invention.

[0040] Those skilled in the art should understand that the drawings are merely schematic diagrams of embodiments, and the components in the drawings are not necessarily necessary for implementing the present invention.

[0041] In order to better apply electron beams to radiotherapy, in this embodiment, a side illuminator that can be used for electron beam radiotherapy is provided, which can convert part of the vertically incident electron beam into X-rays and modulate the intensity of the mixed beam of electrons and X-rays to form a dose distribution consistent with the shape of the treatment window at the side treatment window of the illuminator. It is used for radiotherapy of tumors distributed in a vertical plane, such as postoperative tumor bed of esophageal cancer, thereby expanding the application field of electron beam radiotherapy.

[0042] like Figure 1 to Figure 2 As shown, the side illuminator 111 includes a housing 101, which is a hollow structure with a top opening and a side treatment window 102. The material of the housing 101 is a metal material with a certain thickness to support the scattering foil 103, modulator 104 and attenuator 105 described later, and can support the tumor area attached to the treatment window, and also shield the side area outside the side treatment window of the illuminator. In an example, the housing can be made of stainless steel, and the side treatment window is made of organic glass to reduce the attenuation of the radiation and to fix the modulator 104 on its inner surface.

[0043] The shape of the housing 101 of the side illuminator is preferably a quadrangular prism, and the side treatment window 102 is located on one of the prism surfaces, which can fit the shape of the vertically distributed tumor bed after esophageal cancer surgery.

[0044] The side illuminator also includes a scattering foil 103, which is arranged near the side treatment window and forms a certain angle with the incident direction of the radiation, so as to scatter as many electrons as possible onto the side treatment window.

[0045] According to the method for determining the angle of the scattering foil 103 in the prismatic side applicator of this embodiment: establish a series of scattering foil models with a certain thickness and different angles with the perpendicular direction of the beam, calculate the number of electrons and photons on the treatment window, and take the angle with the largest number as the scattering foil angle.

[0046] In an exemplary embodiment, the series of scattering foils are 1 mm thick, have an angle of 0-70°, and are spaced 10° apart. Using Monte Carlo simulation, the angle of the scattering foil 103 can be any angle in the range of 0°-90°, for example, 60°.

[0047] According to the method for determining the thickness of the scattering foil 103 in the prismatic side illuminator of this embodiment: establish a series of square tungsten scattering foil models with different thicknesses and determined angles, calculate the minimum dose on a line at a certain depth from the surface of the side treatment window in a plane perpendicular to the side treatment window and passing through the center of the side treatment window, and take the thickness corresponding to the maximum value as the scattering foil thickness.

[0048] In an exemplary embodiment, the series of scattering foils have a thickness of 0.1-1 mm, a spacing of 0.1 mm, and an angle of 60°. Using Monte Carlo simulation calculation, the thickness of the scattering foil 103 can be in the range of 0.3 mm to 2 mm, for example, about 0.5 mm.

[0049] In one embodiment, the electron beam is a 12 MeV electron beam that passes through a 60 mm × 35 mm × 300 mm quadrangular prism-shaped light-limiting cylinder 111, and the scattering foil 103 is in the shape of a 50 mm × 25 mm rectangle. In order to maintain a high dose rate, the thickness of the scattering foil 103 only converts part of the electrons into X-rays. When the electron beam is injected into the scattering foil 103 and acts, the resulting ray beam is a mixed beam, which contains both X-rays and electrons.

[0050] Continue to refer to Figure 1 to Figure 2 The prismatic side illuminator further includes a modulator 104 behind the side treatment window 102, which is disposed inside the housing 101. Figure 1 to Figure 2 In the example of FIG. 1 , the housing 101 is a hollow prism structure, and the modulator 104 can be arranged inside the side treatment window 102. The modulator is used to modulate the intensity of mixed radiation including a first radiation such as an electron beam and a second radiation such as an X-ray. In order to provide the greatest possible irradiation intensity in the side treatment window, the upper part of the modulator 104 cannot attenuate the radiation beam directed to the lower part of the side treatment window, and the volume of the modulator 104 needs to be as small as possible. In this embodiment, the material of the modulator is easy to process and has a density of 2.7 g / cm 3 In order to achieve a planar intensity distribution on the surface of the side treatment window 102, the modulator 104 needs to have a desired thickness at each position.

[0051] The optimization method of the modulator thickness can be found in the Chinese invention patent application with application number 201810244336.0, which can be similarly used to determine the thickness of the modulator 104 in this application. Figure 1 to Figure 2 In the example of , the modulator 104 has a mountain-shaped cross-section and is arranged symmetrically about the central axis of the side treatment window. Here, "mountain-shaped" refers to a shape with a low top, a high middle, and a low bottom. That is, the thickness of the modulator is the largest in the middle. The angle can be adjusted through experiments as needed, and will not be repeated here. It should also be noted that, preferably, the mountain-shaped modulator 104 does not extend to the side wall of the prismatic shell 101.

[0052] Figure 3 The dose distribution outside the treatment window surface of the side applicator is shown. Figure 3 (a) shows the dose distribution perpendicular to the side treatment window and passing through the center plane of the side treatment window; Figure 3(b) shows the dose distribution in the plane parallel to the side treatment window. The isodose lines shown in the figure are normalized to the maximum dose point on the side treatment window surface. Figure 3 In (b), the dose distribution has a larger gradient above the side treatment window, which is caused by the oblique incidence of scattered electrons on the side treatment window. In one embodiment, the illuminator can produce a planar dose distribution on the side of the illuminator with a 12MeV electron beam, a dose rate of about 200cGy / min, and a dose at a depth of 0.5cm that is about 60% of the surface dose.

[0053] Figure 4 The percentage depth dose on the central axis at different heights from the top of the side treatment window is shown, and the dose is normalized to the maximum dose point on the surface of the side treatment window.

[0054] The prismatic side illuminator provided in this embodiment is capable of converting part of the electron beam into X-rays and modulating the intensity of the mixed radiation (including electron beams and X-rays), forming a dose distribution consistent with the shape of the treatment window in the area outside the surface of the side treatment window of the prismatic side illuminator, which is used for radiotherapy of tumors distributed in a vertical plane, thereby expanding the scope of use of electron beams.

[0055] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative work on the basis of the technical solution disclosed in the present invention should be included in the scope of protection of the present invention.

Claims

1. A side illuminator, characterized in that: include: a housing having a hollow structure with an opening, a side treatment window, and a bottom surface; a scattering foil, disposed on the side of the lateral treatment window, configured to receive the first radiation, scatter the first radiation, and convert a portion of the first radiation into the second radiation; as well as a modulator, disposed inside the side treatment window, configured to modulate the intensity of mixed radiation including the first radiation and the second radiation; An attenuator is disposed inside the side illuminator and is configured to attenuate the intensity of mixed radiation including the first radiation and the second radiation.

2. The side illuminator according to claim 1, characterized in that: The housing is made of metal material to shield radiation in the side areas outside the treatment window and to support the scattering foil and the attenuator.

3. The side illuminator according to claim 1, characterized in that: The side treatment windows are made of a rigid soft tissue equivalent material to support the modulator.

4. The side illuminator according to claim 1, characterized in that: The scattering foil is located inside the side illuminator, close to the side treatment window, and has an optimized angle and thickness to ensure that a predetermined first radiation scattering angle is achieved while maintaining a predetermined mixed radiation intensity.

5. The side illuminator according to claim 1, characterized in that: The modulator is located on the inner surface of the side treatment window and has an optimized shape and thickness so that the mixed radiation has a desired intensity distribution on the outer surface of the treatment window.

6. The side illuminator according to claim 1, characterized in that: The attenuator is located at the bottom end of the side illuminator.

7. The side illuminator according to claim 6, characterized in that: The attenuator is made of metal material to shield radiation at the bottom end of the illuminator.

8. A method for determining the angle of a scattering foil in a side illuminator according to any one of claims 1 to 7, characterized in that include: N scattering foils are arranged above the side treatment window to scatter and convert the first radiation, N is zero or a positive integer, and each scattering foil has a predetermined thickness and a different angle with the vertical direction of the beam; On the surface of the side treatment window, counting the number of electrons and photons on the treatment window; The angle with the largest number of electrons and photons is selected as the scattering foil angle.

9. A method for determining the thickness of a scattering foil in a side illuminator according to any one of claims 1 to 7, characterized in that include: Model a series of scattering foils with different thicknesses and defined angles; Calculate the minimum dose on a line at a certain depth from the surface of the side treatment window in a plane perpendicular to the side treatment window and passing through the center of the side treatment window; The thickness corresponding to the maximum minimum dose is taken as the scattering foil thickness.

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