RU178295U1 - Rotating Anode Multipath X-ray Tube - Google Patents

Abstract

The utility model relates to X-ray technology, in particular to an X-ray tube, and can be used in medical X-ray diagnostics: radiography, tomography, mammography, tomosynthesis, and non-destructive testing. The x-ray tube contains an anode assembly comprising a cylindrical anode with external conical grooves uniformly made over the entire surface of the anode and being targets of the anode, the anode being mounted in a vacuum cylinder for rotation around the axis of rotation, which determines the longitudinal direction, and a plurality of cathode assemblies, including cathodes for emitting electron beams to form a focal spot on the corresponding target of the anode, while the axis of the electron beams is directed perpendicular to appropriate grooves. Using a device of this design will ensure accurate positioning in the space of the focal spot with its complete immobility during exposure, which will reduce the time of the diagnostic procedure while simultaneously significantly improving the quality of the obtained x-ray image.

Description

FIELD OF TECHNOLOGY

The utility model relates to X-ray technology, in particular to the field of development of X-ray tubes, and can be used in medical X-ray diagnostics: radiography, tomography, mammography, tomosynthesis, and non-destructive testing.

BACKGROUND

To diagnose volumetric formations of the mammary gland, digital mammary gland tomosynthesis (DBT) is used, which makes it possible to obtain three-dimensional images of the mammary gland in the form of separate sections, on which there are no images of objects from overlying or underlying layers, complicating the diagnosis in conventional x-ray mammography, and in the vast majority cases avoid biopsy examination. During the examination, the x-ray tube of the tomosynthesis apparatus rotates around the mammary gland in an arc of 30-50 degrees and in increments of 2-3 degrees, approximately 15-25 digital x-rays are taken. That is, the survey is performed at different positions of the axis of the x-ray beam relative to the object of study. After receiving the pictures, they are transferred to the image reconstruction block, where the software reconstructs the three-dimensional image in the form of a set of two-dimensional sections of breast tissue. The quality of 3D image reconstruction depends on the accuracy of positioning of the focal spot when receiving primary images and its size.

In currently on the market mammograms with tomosynthesis function, the spatial position of the x-ray beam is changed exclusively mechanically, while the survey is done in two ways:

1) at the time of the exposure, the tripod is braked, which requires time for braking, damping the oscillations of the tripod and subsequent acceleration, significantly complicates the mechanics of the mammograph and increases the duration of the examination;

2) shooting is carried out while the tripod is moving, which leads to the inevitable “blur” of the image and the need to reduce the exposure time to the detriment of image quality.

These problems are successfully solved by equipping the mammograph with an X-ray tube, which includes several (15-30) cathode-grid modules located with a certain step along one line. During the examination, the x-ray sources are switched on in turn, and each of them works for the exposure time sufficient to obtain a high-quality x-ray image. Thus, the change in the spatial position of the x-ray beam is achieved not by mechanical movement of the emitter, but by electrical switching of the cathodes of one fixed tube. In this case, the complete immobility of the focal spot during exposure and its precise positioning in space is ensured, which favorably affects the quality of reconstruction of the 3D image of tomosynthesis.

Known models of mammographs with tomosynthesis function, in which linear multipath emitters with fixed anodes are used (WO 2009012453 A1, US 7970099 B2, US 8139716 B2, WO 2011033439 A1). The main disadvantage of such devices is the low power performance of emitters with a fixed anode, which leads to the need to shoot at exposure durations of about 1 second. And this, in turn, leads to a significant increase in the duration of the examination procedure (up to 30 seconds) and a decrease in the quality of image reconstruction due to biological processes in living tissue.

Known models of mammographs with tomosynthesis function, in which anodes are used in the form of a rotating disk with a target on its conical lateral surface (US 2011002442 A1, US 5511105 A, US 4596028 B, RU 2578675 C1). However, in these x-ray tubes, the narrow area of the focal spot on the target, as well as the shape of the focal spot of the electron beam in the form of a circle on the target, leads to a high density of thermal energy in the focal spot released on the surface of the target / anode, and the geometric arrangement of the x-ray sources in an arc a circle in a plane that does not intersect the object of scanning, makes it impossible to conduct a comprehensive tomographic analysis of the scanned object.

The closest analogue of the claimed utility model is a stationary x-ray emitter with a rotating anode in the form of a smooth cylinder (WO 2017173341 A1). The design proposed in this invention does not provide the same size of the effective focal spots and, therefore, the same dose rate in the plane of the X-ray image detector for all the rays of the emitter, which leads to a decrease in the quality of image reconstruction.

Therefore, there is a need to create new stationary x-ray digital systems of thoracic tomosynthesis, computed tomography, non-destructive testing and related methods.

DISCLOSURE OF A USEFUL MODEL

The technical problem solved by the claimed utility model is the need to create a simplified design and reduce the cost of x-ray machines, the need to significantly reduce the time for carrying out diagnostic procedures while significantly improving the quality of examinations.

The technical result achieved by using the claimed utility model is to increase the accuracy of positioning in the space of the focal spot with its complete immobility during exposure.

The technical result is achieved due to the fact that the proposed x-ray tube contains an anode assembly including a cylindrical anode with external conical grooves made uniformly over the entire surface of the anode and being targets of the anode, while the anode is mounted in a vacuum cylinder for rotation around the axis of rotation, which determines longitudinal direction, many cathode nodes, including cathodes for emitting electron beams to form a focal spot on the corresponding target of the anode, while si electron beams are directed perpendicular to the generatrix of the corresponding groove.

In addition, the X-ray tube is characterized by the fact that the length of the anode is determined by the ratio L> 2⋅F⋅tg (α / 2), where F is the focal length of the X-ray apparatus, and α is the total tomography angle.

In addition, the angle between the generatrix of the corresponding groove and the axis of rotation of the anode is determined by the ratio β = arctan (l / F), where F is the focal length of the x-ray apparatus, l is the distance from the central focal spot to the middle of the corresponding groove.

In addition, indirect cathodes with electron-optical systems made with the ability to control on / off cathodes and the formation of an electron beam of a given shape were used as cathodes.

In addition, the focal spot may have an oblong shape with a major axis and a minor axis.

In addition, the small axis of each focal spot coincides with the generatrix of the groove, and the large axis of each focal spot is perpendicular to the generatrix of the corresponding conical groove.

In the proposed device, the exact direction of the axis of the x-ray beam to the center of the x-ray image detector and the equality of the dose rate of x-ray radiation in the plane of the receiver from all the emitter rays is ensured by the use of a cylindrical rotating anode in the sharing device, whose targets are located on conical grooves, and several stationary x-ray sources emissions that are triggered in a certain sequence for the distribution of heat ruzki generated in the anode. The proposed design of a radiator with a rotating anode is able to provide a distance between the extreme focal spots from 45 to 60 cm, complete immobility of the focal spot during exposure and its precise positioning in space, which contributes to the obtaining of an x-ray image of improved quality.

With a nominal focal spot size of 0.3 mm, the emitter is able to provide anode current of at least 100 mA for each beam, which will allow to obtain high-quality primary images at exposures of not more than 0.1 seconds, spending time no more than 2 seconds on the entire process of obtaining primary images, which reduces the likelihood of blurring the X-ray image as a result of the movement of the patient and improves the quality of the reconstruction of the 3D image.

Simplified system design and reduced size increase reliability and reduce purchase and maintenance costs.

TERMS (DEFINITIONS).

In the description of the present invention, the terms “includes,” “including,” and “includes” are interpreted as meaning “includes, but is not limited to.” These terms are not intended to be construed as “consists of only”.

The term “connected” means functionally connected, any number or combination of intermediate elements between the connected components (including the absence of intermediate elements) can be used.

As mentioned herein, the term “multipath x-ray source” may refer to devices that can simultaneously or sequentially generate multiple beams of x-rays.

In the materials of this application, “refractory metal” is usually understood to mean molybdenum (used in mammography) and tungsten (used in radiography). In high-price x-ray tubes, tungsten is alloyed with rhenium.

Unless defined separately, technical and scientific terms in this application have standard meanings generally accepted in the scientific and technical literature.

BRIEF DESCRIPTION OF THE DRAWINGS

Details, features, as well as advantages of this utility model follow from the following detailed description of the claimed technical solution using the drawings, which depict:

FIG. 1 is a schematic diagram of a rotating anode multipath x-ray tube in accordance with an embodiment described below.

FIG. 2 - Schematic diagram of the formation of an electron beam of a given shape, creating a focal spot on the anode target. Top view and side view of a cathode with an electronic optical system and anode target. View of the focal spot.

FIG. 3 - Layout of the plurality of cathodes relative to the cylindrical anode and the location of focal spots from all cathodes in accordance with this technical solution. Front view. Cross section of an x-ray tube.

In the drawings, like numbers are used to denote like parts.

NOTATION

1. Anode

2. The rotor

3. Val

4. Bearing

5. Stator

6. The line of cathode nodes

7. Vacuum cylinder

8. The cathode

9. Electron-optical system

10. The electron beam

11. The target of the anode

12. Focus spot

13. The forming anode.

14. The axis of rotation of the anode

15. The axis of the electron beam

IMPLEMENTATION OF A USEFUL MODEL

In FIG. 1 is a schematic diagram of a stationary x-ray image system with multiple x-ray sources, including a multi-beam x-ray tube in accordance with this technical solution and a stationary plane-parallel detector, which can remain stationary.

As shown in FIG. 1, a multi-beam x-ray tube may include a vacuum cylinder 7, within which an anode assembly comprising a rotating anode 1, and a line of stationary cathode assemblies 6 are provided.

The anode 1 is essentially cylindrical hollow and is located on the shaft 3, which, in turn, is mounted on the inner end walls of the vacuum cylinder 7 using special (designed to work in vacuum) ball bearings 4.

The anode can rotate around an axis of rotation 14, which corresponds to the axis of rotation of the shaft 3 and determines the longitudinal direction of the x-ray tube. The torque is transmitted to the shaft 3 by the engine with the stator 5 due to the induction of an alternating magnetic field acting on the rotor 2 of the engine. When current is applied to the stator of the electric motor (electromagnets), the rotor of the electric motor begins to rotate due to the induction of a magnetic field and its interaction with the magnets of the motor rotor. One skilled in the art would understand that the transmission is not limited to this embodiment and can be implemented using any known mechanism.

The rotating anode 1 is made in the form of a cylinder made of copper or graphite, the length of which L is determined by the ratio:

L> 2⋅F⋅tg (α / 2),

where F is the focal length of the x-ray apparatus, α is the total angle of tomography.

The surface of the anode is made with evenly spaced conical grooves, which are the targets of the anode, on the surface of which a refractory metal is applied - tungsten or molybdenum. The distance between two adjacent grooves is the same for all grooves. The surface angle of the corresponding groove (generatrix angle) relative to the axis of rotation of the anode is calculated by the formula:

β = arctan (l / F),

where F is the focal length of the x-ray apparatus, l is the distance from the middle of the cylinder (central focal spot) to the middle of the corresponding groove.

In the presence of conical grooves on the surface of the cylindrical anode 1, the axis of each x-ray beam is perpendicular to the generatrix of the corresponding groove, which ensures the same size of the effective focal spots and, therefore, the same dose rate in the plane of the x-ray image detector for all emitter rays.

In mammography, the size of the focal spot is 0.3 mm. The depth of the groove may be approximately equal to the nominal value of the size of the focal spot. Consequently, the depth of the groove will be, in the worst case, not more than 0.5 mm, which allows the use of a hollow cylinder as an anode.

Indirectly heated cathodes with electron-optical systems are used in the cathode assembly line, which allow controlling the on / off of cathodes (rays) and forming an electron beam of a given shape, creating an elongated focal spot on the anode target: L1 - major axis of the focal spot, L2 - minor axis focal spot. The cathodes can be turned on and off sequentially (alternately) at a given speed, depicting the object at different angles. Alternatively, cathodes may be included based on a predetermined sequence (for example, not necessarily, sequentially in a row). Accordingly, it is possible to obtain various reconstructed images of moving objects.

The major axis of each focal spot (L1) is perpendicular to the generatrix of the corresponding cylindrical conical groove. The minor axis (L2) of the focal spot coincides with the generatrix of the conical surface of the target.

The cathodes 8 are located essentially along a straight line at an angle to direct the x-rays to the object so that the axes of their electron beams 15 are directed perpendicular to the surface of the corresponding groove (target) of the cylindrical anode 1. Therefore, the farther from the middle of the anode, the smaller the distance between adjacent cathodes.

The location line of the cathodes 8 may be parallel to the image plane of the x-ray detector.

The cathodes 8 and the x-ray detector can be stationary relative to each other when the object is irradiated with x-ray sources and projection images are detected by the x-ray detector. Focal spots from all cathodes are located on one line - the generatrix of the cylindrical anode. Focal spots can be essentially the same size.

After supplying power to the x-ray apparatus in which the tube is installed, a low level of incandescent voltage is applied to the cathodes — the heating voltage, which is maintained while waiting for the procedure. Locking voltages are applied to the control electrodes of the cathode assemblies — negative with respect to the cathode.

When carrying out the procedure and pressing the “Exposure” button of the X-ray apparatus, the full glow voltage is applied to the cathodes and an alternating voltage is applied to the stator to spin the anode. At the end of the process of heating the cathodes to operating temperature and accelerating the anode to a speed of 2700 rpm, a trigger voltage is applied to the control electrode of the first cathode — positive with respect to the cathode. Its value is chosen so that an electron beam of a given configuration is formed that provides the necessary size of the focal spot. At the same time, high voltage is applied to the anode. When electrons enter the anode material, an x-ray is formed. By tracking the angle of rotation of the anode and the turn-on time of the corresponding cathode, an electron beam is created in geometry, as shown in FIG. 2. In order to maintain the location of the focal spot during the sequence of images, the time between applying voltage to the respective cathodes will be the time during which the anode axis rotates 360 ° (the time can be a multiple of the 360 ° rotation time of the anode).

At the end of the first exposure, a blocking voltage is applied to the control electrode of the first cathode — negative with respect to the cathode. High voltage is not removed from the anode. The flat panel detector enters the reading mode of the first image. At the end of the reading process, the detector sets a ready signal, and a trigger voltage is applied to the control electrode of the second cathode — positive relative to the cathode — the x-ray radiation from the second cathode is turned on. At the end of the second exposure, a blocking voltage — negative with respect to the cathode — is applied to the control electrode of the second cathode. High voltage from the anode is still not removed. The flat panel detector enters the read mode of the second image. Similarly, on-off cycles are performed sequentially for all cathodes.

After the last cathode is turned off, a high voltage is removed from the tube anode, an alternating voltage is removed from the stator, and the filament voltage at the cathodes decreases to the heating level. The handset goes into standby mode.

All received primary images are transferred to a workstation, where a layered image of the object of study is obtained by a special reconstruction algorithm.

Although the present utility model has been described in detail with examples of options that appear to be preferred, it must be remembered that these embodiments of the utility model are provided only to illustrate the utility model. This description should not be construed as limiting the scope of the utility model, since the design of the proposed multi-beam X-ray tube by specialists in the field of X-ray technology and others may be amended to adapt the multi-beam X-ray tube to specific materials or situations, and not beyond attached utility model formula. The person skilled in the art understands that within the scope of the utility model, which is determined by the paragraphs of the proposed formula, various options and modifications are possible, including equivalent solutions. All such variations, which are obvious to experts in the given field of technology, are considered to be included in the scope of the present utility model, which is defined in the attached formula. To clarify the present description, it should be noted that the phrase "characterized by" means "including, but not limited to."

Claims (8)

1. An x-ray tube containing an anode assembly comprising a cylindrical anode with external conical grooves uniformly made over the entire surface of the anode and being targets of the anode, the anode being mounted in a vacuum cylinder for rotation about an axis of rotation that defines a longitudinal direction, a plurality of cathode assemblies including cathodes for emitting electron beams to form a focal spot on the corresponding target of the anode, with the axis of the electron beams being directed perpendicular to the corresponding groove. 2. The x-ray tube according to claim 1, characterized in that the anode length is determined by the ratio L> 2⋅F⋅tg (α / 2), where F is the focal length of the x-ray apparatus, α is the total tomography angle. 3. The x-ray tube according to claim 1, characterized in that the angle between the generatrix of the corresponding groove and the axis of rotation of the anode is determined by the ratio β = arctan (1 / F), where F is the focal length of the x-ray apparatus, 1 is the distance from the central focal spot to the middle appropriate grooves. 4. The x-ray tube according to claim 1, characterized in that the cathodes used are indirect cathodes with electron-optical systems made with the ability to control the on / off cathodes and the formation of an electron beam of a given shape. 5. The x-ray tube according to claim 1, characterized in that the focal spot has an oblong shape with a major axis and a minor axis. 6. The x-ray tube according to claim 5, characterized in that the small axis of each focal spot coincides with the generatrix of the groove, and the large axis of each focal spot is perpendicular to the generatrix of the corresponding conical groove.

Images