Static CT imaging device with tube current modulation function and imaging method thereof

Abstract

A static CT imaging device with a tube current modulation function and an imaging method therefor are provided. [Solution] The static CT imaging device of the present invention includes a radiation source ring and a detector ring. The radiation source ring is provided with a plurality of uniformly distributed radiation sources, each of which emits radiation to scan the human body to be measured and projects positioning images of the human body at different angles onto the detector ring. The detector ring is provided with a plurality of uniformly distributed detectors for collecting radiation and obtaining positioning images. Based on the projection brightness of the positioning image, tube current modulation information of the radiation sources corresponding to the corresponding projection positions is obtained, where the tube current modulation information includes the tube current value to be used by each radiation source on the radiation source ring during the medical examination. The tube current of the corresponding radiation source on the radiation source ring is adjusted based on the tube current modulation information. By realizing automatic tube current modulation, the present invention can effectively reduce the exposure dose to the human body.

Description

【Technical Field】 【0001】 The present invention belongs to the technical field of medical devices, relates to a static CT imaging device with a tube current modulation function, and also relates to a corresponding static CT imaging method. 【Background Art】 【0002】 CT (Computed Tomography) is an abbreviation for computed tomography technology. Its imaging principle is to use an X-ray beam and a high-sensitivity X-ray detector to perform cross-sectional scans layer by layer around a specific part of the human body, receive the X-rays transmitted through this layer by the scintillation material in the X-ray detector, convert them into visible light, then convert them into electrical signals by a photoelectric converter, amplify them, and then convert them into digital signals by analog / digital conversion and input them into a computer for processing. In the computer, after calculating the information obtained by scanning each cross-section layer by layer, the X-ray attenuation coefficient or absorption coefficient of each voxel is obtained and arranged in a matrix, that is, a voxel digital matrix. The digital information in the voxel digital matrix is converted into small blocks with different shades from black to white, which are called pixels in a two-dimensional projection and are arranged tomographically to form a CT image. 【0003】 To increase scanning speed, improve imaging accuracy and speed, avoid the effects of centrifugal force due to mechanical rotation, and reduce signal tailing effects and overlapping crosstalk during high-speed rotation, a static real-time CT imaging system is disclosed in the Chinese Invention Patent, Publication No. CN105361900B. This static real-time CT imaging system comprises an annular photon counting detector, an annular scanning X-ray source, and a scanning timing controller. Under the control of the scanning timing controller, the annular scanning X-ray source emits X-rays in a narrow beam, which pass through the object being measured and are projected onto the corresponding annular photon counting detector. The annular photon counting detector transmits the corresponding exposure information to the data acquisition processing unit and the human-computer interaction unit via the scanning host and the main control unit, where the data acquisition processing unit and the human-computer interaction unit complete image reconstruction. In the scanning process of the static real-time CT imaging system described above, the annular scanning X-ray source does not need to rotate significantly. By sequentially switching the projection position of the X-rays using electronic control, the scanning speed can be increased by several tens of times, enabling the acquisition of dynamic three-dimensional stereoscopic images. Furthermore, by using a photon counting detector, absorption data and energy data can be obtained, resulting in the real-time reconstruction of data. 【0004】 However, in the process of performing medical examinations using CT scanners, it is necessary to control the radiation dose to reduce harm to the human body. In many spiral CT devices, there is only one radiation source, so in the most extreme cases (chest scans), two cycles of tube current adjustment are required for one scan, and if scanning four times per second, the adjustment frequency of the tube current becomes approximately 8 Hz. In the case of a thermal cathode radiation source, the magnitude of the tube current is greatly affected by the ambient temperature and filament temperature, making it technically very difficult to achieve tube current modulation. [Overview of the Initiative] [Problems that the invention aims to solve] 【0005】 The main technical problem that this invention aims to solve is to provide a static CT imaging device equipped with tube current modulation functionality. 【0006】 Another technical problem that the present invention aims to solve is to provide a corresponding static CT imaging method. 【0007】 To achieve the above objectives, the present invention employs the following technical solutions. 【0008】 According to a first embodiment of the present invention, the present invention includes a radiation source ring and a detector ring, The radiation source ring is equipped with a plurality of uniformly distributed radiation sources, each of which emits radiation to scan the human body to be measured and is used to project positioning images of the human body at different angles onto the detector ring, and the detector ring is equipped with a plurality of uniformly distributed detectors to collect the radiation and acquire the positioning images. Based on the projection brightness of the positioning image, tube current modulation information of the radiation source corresponding to the projection position is obtained, and the tube current modulation information includes the value of the tube current that each radiation source on the radiation source ring should use during the medical examination. The present invention provides a static CT imaging device equipped with a tube current modulation function that adjusts the tube current of the corresponding radiation source on the radiation source ring based on the tube current modulation information. 【0009】 Preferably, based on the projection brightness of the positioning image, the 0-degree tube current to be used by the radiation source at the 0-degree position in the radiation source ring during the medical examination is obtained. Based on the height of the bed, the thickness of the human body and the coverage area of ​​the human body in the XY direction of the positioning image are determined, and the 90-degree tube current to be used by the radiation source at the 90-degree position in the radiation source ring is obtained during the medical examination. According to the principle of symmetry, the 180-degree tube current is obtained based on the 0-degree tube current, and the 270-degree tube current is obtained based on the 90-degree tube current. By interpolating the 0-degree tube current, 90-degree tube current, 180-degree tube current, and 270-degree tube current using an interpolation method, the tube current that should be used by the radiation source at each position in the radiation source ring during a medical examination is obtained. 【0010】 Preferably, each of the radiation sources emits radiation alternately at a set frequency, and the projection areas corresponding to each of the radiation sources do not overlap. 【0011】 Furthermore, the static CT imaging device further comprises an image processing device, which is connected to the detector ring and used to receive the positioning image and perform image processing on the positioning image. 【0012】 Preferably, the interpolation method is a linear interpolation method or an elliptic interpolation method. 【0013】 According to a second embodiment of the present invention, a static CT imaging method is provided which is implemented based on the static CT imaging device described above. The steps include: each radiation source in the radiation source ring emits radiation to scan the human body to be measured, and projects positioning images of the human body at different angles onto the detector ring, thereby allowing a detector on the detector ring to acquire the positioning image; A step of acquiring tube current modulation information of the radiation source corresponding to the projection position based on the projection brightness of the positioning image, wherein the tube current modulation information includes the value of the tube current that each of the radiation sources on the radiation source ring should use during the medical examination. The procedure includes the step of adjusting the tube current of the corresponding radiation source on the radiation source ring based on the tube current modulation information. 【0014】 Preferably, based on the projection brightness of the positioning image, the 0-degree tube current to be used by the radiation source at the 0-degree position in the radiation source ring during the medical examination is obtained. Based on the height of the bed, the thickness of the human body and the coverage area of ​​the human body in the XY direction of the positioning image are determined, and the 90-degree tube current to be used by the radiation source at the 90-degree position in the radiation source ring is obtained during the medical examination. According to the principle of symmetry, the 180-degree tube current is obtained based on the 0-degree tube current, and the 270-degree tube current is obtained based on the 90-degree tube current. By interpolating between the 0-degree tube current, 90-degree tube current, 180-degree tube current, and 270-degree tube current using an interpolation method, the tube current that should be used by the radiation source at each position in the radiation source ring during a medical examination is obtained. 【0015】 Preferably, the value of the tube current is associated with the thickness of the human body. [Effects of the Invention] 【0016】 The stationary CT imaging device equipped with tube current modulation function provided in the present invention, compared to conventional technology, sets the tube current of the radiation source corresponding to the projection angle to a value associated with the thickness of the human body, in accordance with different conditions of radiation passing through the thickness of the human body at different projection angles. This thereby achieves automatic modulation of the tube current and effectively reduces the radiation dose to the human body. [Brief explanation of the drawing] 【0017】 [Figure 1] This is a schematic diagram showing the overall structure of a static CT imaging device equipped with tube current modulation function according to one embodiment of the present invention. [Figure 2] This is a schematic diagram showing the distribution of radiation sources in a static CT imaging device according to one embodiment of the present invention. [Figure 3] This is a schematic diagram showing the tube current corresponding to the projection angle in one embodiment of the present invention. [Figure 4] This figure shows a flowchart of a static CT imaging method equipped with a tube current modulation function according to one embodiment of the present invention. [Modes for carrying out the invention] 【0018】 The technical content of the present invention will be described in detail and specifically below in combination with the accompanying drawings and specific embodiments. 【0019】 In the process of performing a medical examination using a CT device, automatic modulation of the tube current, which automatically adjusts the value of the tube current used during scanning based on a positioning image, is one of the important techniques for controlling the radiation dose. In existing spiral CT devices, since there is only one radiation source, it has been technically difficult to achieve tube current modulation. 【0020】 As shown in FIG. 1, since a static CT imaging device is equipped with a plurality of radiation sources uniformly distributed throughout the ring, the concept of realizing the automatic modulation technology of the tube current is completely different from that of a spiral CT device. In a static CT imaging device, there is no need to adjust the tube current of a single radiation source in real time. According to the relationship between the tube current and the projection angle, it is only necessary to calculate the tube current of the radiation source at a specific projection angle and perform the corresponding setting. Before scanning, if a pre-calculated tube current modulation method for various angular positions is set for the radiation source at the corresponding angular position, the static CT imaging device can scan according to this set tube current modulation method. 【0021】 Therefore, by combining the unique characteristics of the radiation source ring and the detector ring of a static CT imaging device, a unique automatic tube current modulation function can be realized. That is, by setting the tube current of the radiation source corresponding to the projection angle to a value associated with the body thickness according to the different situations of the X-rays passing through the body thickness at different projection angles, "automatic modulation of the tube current" can be realized, and the radiation dose to the human body can be effectively reduced. 【0022】 It should be noted that in the art, the intensity of X-rays is usually represented by milliamperes (mA) of the tube current. By controlling the value of the tube current, the brightness of the projection image (such as a positioning image) can be controlled. Also, the 0-degree position mentioned in the embodiments of the present invention refers to the position directly above the radiation source ring and / or the detector ring, and the corresponding angular positions are calculated in the counterclockwise direction. 【0023】 In embodiments of the present invention, a static CT imaging device equipped with a tube current modulation function is first provided. The core idea of ​​this static CT imaging device is to utilize the unique characteristics of the radiation source ring and detector ring of the static CT imaging device to calculate and set the value of the tube current required for the radiation source at a specific projection angle according to the relationship between the tube current and the projection angle. Before scanning, the tube current modulation scheme calculated in advance for each angular position is set for the radiation source at the corresponding angular position, and then scanning is performed according to this set tube current value. 【0024】 Hereinafter, specific embodiments of a static CT imaging device equipped with this tube current modulation function will be described in detail by combining the embodiments shown in Figures 2 and 3. 【0025】 As shown in Figure 2, a static CT imaging device with tube current modulation functionality comprises a radiation source ring and a detector ring. The radiation source ring is equipped with a plurality of uniformly distributed radiation sources, each radiation source emitting radiation to scan the human body to be measured and used to project positional images of the human body at different angles onto the detector ring. The detector ring is equipped with a plurality of uniformly distributed detectors to collect the radiation and acquire the positional images. Based on the projection brightness of the positional images, tube current modulation information of the radiation sources corresponding to the corresponding projection positions is acquired, and the tube current modulation information includes the value of the tube current that each radiation source on the radiation source ring should use during the medical examination. Based on the tube current modulation information, the tube current of the corresponding radiation sources on the radiation source ring is adjusted. 【0026】 In one embodiment of the present invention, the radiation source is preferably an X-ray source, but may be of other types. A positioning image of the human body is acquired by scanning using a radiation source at the 0-degree position, and based on the projection brightness of the positioning image, the 0-degree tube current mA-0 that the radiation source at the 0-degree position in the radiation source ring should use during the medical examination is obtained. 【0027】 Based on the height of the bed, the thickness of the human body and the coverage area of ​​the human body in the XY direction of the positioning image are determined, and the 90-degree tube current mA-90 that should be used by the radiation source at the 90-degree position in the radiation source ring during the medical examination is obtained. According to the principle of symmetry, a 180-degree tube current mA-180 is obtained based on the 0-degree tube current, and the value of mA-180 is equal to the value of mA-0. A 270-degree tube current mA-270 is obtained based on the 90-degree tube current, and the value of mA-270 is equal to the value of mA-90. Specifically, considering the inherent symmetry of the human body, with mA-0, mA-90, mA-180, and mA-270 as the four endpoints, the tube currents with different projection angles exhibit both axial symmetry and centripetal symmetry. 【0028】 Therefore, the tube currents corresponding to the projection angles shown in Figure 3 are obtained by interpolating between the 0-degree tube current, 90-degree tube current, 180-degree tube current, and 270-degree tube current using an interpolation method, thereby acquiring the tube currents that the radiation sources at each angular position in the radiation source ring should use during a medical examination. 【0029】 In addition to the linear interpolation method described above, other interpolation methods can also be used. For example, the human body can be simulated as an ellipse, with 0 degrees and 90 degrees corresponding to the minor and major axes of the ellipse, respectively. By calculating the paths of radiation passing through this ellipse at different projection angles, the tube current mA-X (where X represents the angle) of the radiation source corresponding to each projection angle can be obtained. 【0030】 Once the tube current settings for the radiation sources at different projection angles are complete, the normal scanning process begins. Each radiation source located at a different projection angle in the radiation source ring performs the medical examination with a different tube current. 【0031】 In one embodiment of the present invention, a plurality of radiation sources (e.g., 4, 6, or 8) may be evenly arranged in a radiation source ring. Each radiation source alternately emits radiation at a set frequency, but the alternating frequencies of the emitted radiation must be such that the corresponding projection areas of each radiation source do not overlap in order to avoid interference. 【0032】 In one embodiment of the present invention, the static CT imaging device may further include an image processing device. This image processing device is connected to a detector ring and is used to receive the positioning image and to perform image processing on the positioning. 【0033】 Based on the static CT imaging device described above, as shown in Figure 4, an embodiment of the present invention further provides a static CT imaging method equipped with a tube current modulation function, specifically comprising steps S1 to S3. S1: Each radiation source in the radiation source ring emits radiation to scan the human body to be measured, and projects positioning images of the human body at different angles onto the detector ring, thereby enabling the detectors on the detector ring to acquire the positioning images. S2: A step of acquiring tube current modulation information of the radiation source corresponding to the projection position based on the projection brightness of the positioning image of the human body, wherein the tube current modulation information includes the value of the tube current that each of the radiation sources on the radiation source ring should use during the medical examination. S3: Based on the tube current modulation information, the tube current of the corresponding radiation source on the radiation source ring is adjusted. 【0034】 Specifically, by scanning with a radiation source at the 0-degree position, a positioning image of the human body is obtained, and based on the projection brightness of the positioning image, the 0-degree tube current mA-0 that the radiation source at the 0-degree position in the radiation source ring should use during the medical examination is obtained. Based on the height of the bed, the thickness of the human body and the coverage area of ​​the human body in the XY direction of the positioning image are determined, and the 90-degree tube current mA-90 that should be used by the radiation source at the 90-degree position in the radiation source ring during the medical examination is obtained. In accordance with the principle of symmetry of the human body, a 180-degree tube current mA-180 is obtained based on the 0-degree tube current, and the value of mA-180 is equal to the value of mA-0. Similarly, a 270-degree tube current mA-270 is obtained based on the 90-degree tube current, and the value of mA-270 is equal to the value of mA-90. That is, considering the inherent symmetry of the human body, with mA-0, mA-90, mA-180, and mA-270 as the four endpoints, the tube currents with different projection angles exhibit both axial symmetry and centripetal symmetry. 【0035】 Therefore, by interpolating between the 0-degree tube current, 90-degree tube current, 180-degree tube current, and 270-degree tube current using an interpolation method, the tube current to be used by the radiation source at each angular position in the radiation source ring during a medical examination is obtained. In different embodiments of the present invention, the interpolation method may be a linear interpolation method or an elliptic interpolation method. 【0036】 Since the tube current value is associated with the thickness of the human body, the tube current value associated with the thickness of the human body is set for the corresponding radiation source on the radiation source ring. After the tube current settings for the radiation sources at different projection angles are complete, the normal scanning process is started. Each radiation source at different projection angles on the radiation source ring performs the medical examination with a different tube current. 【0037】 The stationary CT imaging device and imaging method provided in the present invention, equipped with a tube current modulation function, set the tube current of the radiation source corresponding to the projection angle to a value related to the thickness of the human body, in accordance with situations where the thickness of the human body through which radiation passes differs at different projection angles, thereby achieving automatic modulation of the tube current and effectively reducing the radiation dose to the human body. 【0038】 The static CT imaging device equipped with tube current modulation function and the imaging method thereof provided in the present invention have been described in detail above. To those skilled in the art, any obvious modification made to the present invention without departing from the substantial content of the present invention will constitute infringement of the patent rights of the present invention and will result in corresponding legal liability.

Claims

[Claim 1] A static CT imaging device equipped with tube current modulation function, Equipped with a radiation source ring and a detector ring, The radiation source ring is equipped with a plurality of uniformly distributed radiation sources, each of which emits radiation to scan the human body to be measured and is used to project positional images of the human body at different angles onto the detector ring. The detector ring is equipped with a plurality of uniformly distributed detectors for collecting the radiation and obtaining the positioning image. The static CT imaging device is The system is configured to acquire a positional image of the human body by scanning using a radiation source at the 0-degree position on the radiation source ring, and to acquire the 0-degree tube current that the radiation source at the 0-degree position should use during the medical examination based on the projected brightness of the positional image. The system is configured to determine the thickness of the human body and the coverage area of ​​the human body in the X-Y direction of the positioning image based on the height of the bed, and to acquire the 90-degree tube current that should be used by the radiation source at the 90-degree position on the radiation source ring during the medical examination. In accordance with the principle of symmetry, the system is configured to acquire a 180-degree tube current based on the 0-degree tube current and a 270-degree tube current based on the 90-degree tube current. The system is configured to obtain the tube current that should be used by each position of the radiation source on the radiation source ring during a medical examination by interpolating between the 0-degree tube current, 90-degree tube current, 180-degree tube current, and 270-degree tube current using an interpolation method. Before scanning, the tube current to be used during the medical examination for each radiation source on the radiation source ring, which is acquired based on the positioning image, is configured to be set individually for each corresponding radiation source. Here, each of the radiation sources emits radiation alternately at a set frequency, and the projection areas corresponding to each of the radiation sources do not overlap. The static CT imaging device further comprises an image processing device, which is connected to the detector ring and used to receive the positioning image and perform image processing on the positioning image. A static CT imaging device equipped with tube current modulation functionality, characterized by the above features. [Claim 2] The static CT imaging device equipped with tube current modulation function according to claim 1, characterized in that the interpolation method uses a linear interpolation method or an elliptic interpolation method. [Claim 3] A static CT imaging method implemented based on the static CT imaging device described in claim 1 or 2, Each radiation source in the radiation source ring emits radiation to scan the human body to be measured, and projects positioning images of the human body at different angles onto the detector ring, thereby enabling the detectors on the detector ring to acquire the positioning images. A step of acquiring tube current modulation information of the radiation source corresponding to the projection position based on the projection brightness of the positioning image, wherein the tube current modulation information includes the value of the tube current that each of the radiation sources on the radiation source ring should use during the medical examination. A static CT imaging method characterized by comprising the step of adjusting the tube current of a corresponding radiation source on the radiation source ring based on the tube current modulation information. [Claim 4] Based on the projection brightness of the positioning image, the 0-degree tube current that the radiation source at the 0-degree position in the radiation source ring should use during the medical examination is obtained. Based on the height of the bed, the thickness of the human body and the coverage area of ​​the human body in the X-Y direction of the positioning image are determined, and the 90-degree tube current to be used by the radiation source at the 90-degree position in the radiation source ring is obtained during the medical examination. According to the principle of symmetry, the 180-degree tube current is obtained based on the 0-degree tube current, and the 270-degree tube current is obtained based on the 90-degree tube current. The static CT imaging method according to claim 3, characterized in that an interpolation method is used to interpolate between the 0-degree tube current, the 90-degree tube current, the 180-degree tube current, and the 270-degree tube current to obtain the tube current that the radiation source at each angle in the radiation source ring should use during a medical examination. [Claim 5] The static CT imaging method according to claim 3, characterized in that the interpolation method uses a linear interpolation method or an elliptic interpolation method. [Claim 6] The static CT imaging method according to claim 3, characterized in that the value of the tube current is associated with the thickness of the human body.

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