X-ray image taking device

Abstract

An X-ray imaging apparatus is provided that uses the characteristic values ​​of a field emission X-ray generator and an X-ray detector to provide a relatively high-quality image with the same image quality at a relatively low dose or less by X-ray imaging driven by a high-speed pulse of X-rays. The X-ray image imaging apparatus according to the present invention includes: an imaging unit comprising an X-ray generator and an X-ray detector, wherein the X-ray generator irradiates an object with X-rays, and the X-ray detector receives X-rays transmitted through the object and generates projection data frame by frame; an input unit for inputting imaging information including at least one of tube voltage, tube current, and irradiation time; a storage unit for storing generator irradiation information including at least one of the rise time and fall time of the X-ray generator, detector detection information including at least one of the frame rate and readout time of the detector, dose-pulse-quality relationship information relating to the relationship between X-ray dose, X-ray pulse number, and X-ray image quality; and a control unit for calculating the number of X-ray pulses for X-ray imaging of the object based on the imaging information, using the generator irradiation information, the detector detection information, and the dose-pulse-quality relationship information.

Description

Technical Field

[0001] This invention relates to an X-ray image capturing device, and more specifically, to an X-ray image capturing device for starting / stopping a pulse-driven X-ray generator. Background Technology

[0002] In industrial fields, including the medical field, X-ray imaging devices refer to devices that use X-ray detectors to detect X-rays emitted from and transmitted through an X-ray emitter onto a subject, and construct an X-ray image based on the detected electrical signals. X-rays attenuate at different rates depending on the material along their path as they pass through, and upon reaching the X-ray detector, are converted into electrical signals through photoelectric effects. As described above, X-ray imaging devices utilize electrical signals reflecting the cumulative attenuation along the X-ray's path to provide information related to the interior of the subject as an X-ray image.

[0003] Recently, research and development have been underway on X-ray sources utilizing field emission methods from nanostructures such as carbon nanotubes (CNTs). X-ray generators using carbon nanotubes differ from existing thermionic emission X-ray generators using tungsten filaments in their electron emission mechanism. Because field emission X-ray generators can emit electrons by applying a voltage, they offer faster electron emission and control compared to thermionic emission. Therefore, they can more easily emit X-rays in the form of start / stop pulses for various applications such as X-ray video recording, and provide the possibility of relatively low-dose X-ray imaging.

[0004] Currently, X-ray imaging in medical settings is determined based on imaging conditions such as tube voltage, tube current, imaging distance (FFD), dose, and imaging time. However, since these imaging conditions are based on existing X-ray imaging devices using thermionic X-ray tubes (i.e., thermionic emission X-ray generators), the following problem exists: under these imaging conditions, the advantages of field emission X-ray generators, which achieve low dose and high image quality through pulse driving, cannot be fully utilized. Summary of the Invention

[0005] Technical issues The present invention was proposed to solve the above-mentioned problems, and its object is to provide an X-ray image capturing apparatus in which an X-ray image capturing apparatus equipped with an X-ray generator that is advantageous for pulse-driven field emission mode can provide an image of relatively high quality with the same image quality at a dose that is relatively low or less than that of a thermionic X-ray generator by utilizing the characteristic values ​​of the X-ray generator and the X-ray detector.

[0006] Technical solution To address the aforementioned technical problems, the X-ray image imaging apparatus according to the present invention comprises: an imaging unit including an X-ray generator and an X-ray detector, wherein the X-ray generator irradiates an object with X-rays, and the X-ray detector receives the X-rays transmitted through the object and generates projection data frame by frame; an input unit for inputting imaging information including at least one of tube voltage, tube current, and irradiation time; a storage unit for storing generator irradiation information including at least one of the rise time and fall time of the X-ray generator, detector detection information including at least one of the frame rate and readout time of the detector, dose-pulse-quality relationship information relating to the relationship between X-ray dose, X-ray pulse number, and X-ray image quality; and a control unit for calculating the number of X-ray pulses for X-ray imaging of the object based on the imaging information, using the generator irradiation information, the detector detection information, and the dose-pulse-quality relationship information.

[0007] The control unit can calculate the X-ray pulse rate of the X-ray source based on the number of X-ray pulses, adjust the frame rate of the X-ray detector based on the X-ray pulse rate, and control the X-ray generator and the X-ray detector to X-ray the subject during the irradiation time with the X-ray pulse rate and the adjusted frame rate.

[0008] The X-ray dose based on the number of pulses can be below the X-ray dose based on the imaging information.

[0009] The shooting information may also include: mode information, used to select low-dose mode and high-quality mode.

[0010] The number of pulses of the X-ray generator in the low-dose mode can be configured to be less than the number of pulses of the X-ray generator in the high-definition mode.

[0011] The generator irradiation information may also include the interval time between X-ray pulses.

[0012] The interval time can be greater than or equal to the readout time of the detector.

[0013] The image quality of the X-ray image may include the SNR value.

[0014] Beneficial effects According to the configuration of the present invention, the following effect is achieved: in an X-ray imaging apparatus equipped with an X-ray generator that is advantageous for pulse-driven field emission, by utilizing the characteristic values ​​of the applied X-ray generator and X-ray detector, and by using high-speed pulse-driven X-ray imaging, an image of the same quality is provided as a relatively high-quality image at a relatively low dose or less. Attached Figure Description

[0015] Figure 1 It is a graph showing the theoretical relationship between the number of X-ray pulses and image quality under the same X-ray dose conditions.

[0016] Figure 2 The results show that, under the same X-ray dose conditions in a practical device, image quality improves with increasing X-ray pulse number.

[0017] Figure 3 The diagram shows a waveform of an X-ray imaging apparatus according to an embodiment of the present invention, based on a pulse-driven X-ray dose.

[0018] Figure 4 This is a block diagram illustrating the configuration of an X-ray image capturing apparatus according to an embodiment of the present invention.

[0019] Figure 5 This is a flowchart illustrating an X-ray imaging method using an X-ray image imaging apparatus according to an embodiment of the present invention. Detailed Implementation

[0020] Various embodiments of the present invention will be described below with reference to the accompanying drawings. The technical concept of the present invention can be further clearly understood through these embodiments. The present invention should not be limited to the embodiments described below.

[0021] Figure 1 It is a graph showing the theoretical relationship between the number of X-ray pulses and image quality under the same X-ray dose conditions.

[0022] The horizontal axis of the graph represents the number of X-ray pulses required to uniformly divide and irradiate an image with a total photon count of 100. The vertical axis represents the signal-to-noise ratio (SNR), an indicator of image quality. X-rays follow a Poisson distribution. Therefore, the SNR value, as an indicator of X-ray image quality, is theoretically proportional to the root of the photon count.

[0023] That is, when X-ray dose = number of photons = N, if 100 photons are continuously irradiated, the signal-to-noise ratio (SNR) is root(100) = 10. If the 100 photons are divided into two pulses and irradiated with 50 photons each time, then root(50) = 7.07 and 2 x 7.07 = 14.1. Therefore, compared to using 100 photons at once, when the same amount of photons is used in two pulses, the SNR value shows a theoretical increase of about 40%. According to this principle, it can be known that, under the condition that the total number of X-ray photons is constant, as the number of pulses used to irradiate them increases, the image quality of the X-ray image improves in the same trend as the curve.

[0024] Figure 2 The results show that, under the same X-ray dose conditions in a practical device, image quality improves with increasing X-ray pulse number.

[0025] In actual X-ray imaging devices, under the same X-ray dose conditions, the increase in image quality index SNR with increasing X-ray pulse number may not be entirely consistent with the theoretical increasing trend mentioned above due to various factors. However, when comparing the SNR value of an image exposed once at 30 FPS (Frames Per Second) using the applicant's actual X-ray imaging device (EOX) with the SNR value of an image exposed twice at 60 FPS to meet the same dose conditions, it can be confirmed that the SNR is improved by approximately 19%.

[0026] Figure 3 The diagram shows a waveform of an X-ray imaging apparatus according to an embodiment of the present invention, based on a pulse-driven X-ray dose.

[0027] In the X-ray imaging apparatus according to this embodiment, when a field emission X-ray generator is driven using a square wave signal, the irradiated X-ray dose is as shown in the graph below: the driving signal reaches the target value after a predetermined rising time from the ON point, and the driving signal decreases after a predetermined falling time from the OFF point. The rising and falling times can vary depending on the characteristics of the X-ray generator. For field emission X-ray generators, the rising and falling times are relatively short compared to thermionic emission X-ray generators, but they also vary slightly among field emission X-ray generators depending on individual characteristics.

[0028] The existence of rise and fall times in actual X-ray imaging devices is one reason why the increase in SNR with increasing pulse number under the same X-ray dose conditions differs from the theoretically predicted amount. Another reason is that, as shown in the figure, only doses higher than the minimum dose benchmark, which is a value related to the efficiency of the imaging device, contribute to the generation of X-ray images. Due to these factors, the increase in SNR with pulse number under the same X-ray dose conditions does not match the theoretically predicted value. However, the fact that the SNR increases with increasing pulse number is consistent with the situation confirmed by the aforementioned actual products.

[0029] In this figure, the interval time represents the rest period in the pulse drive of the X-ray generator. As shown, the interval time can be inserted between each X-ray pulse or periodically between nodes formed by multiple pulses and the next node. The interval time can be the same as the readout time of the X-ray detector or inserted to be longer. Furthermore, the insertion of the interval time can match the pulse drive frequency of the X-ray generator with the frame rate (i.e., the number of frames acquired per second) of the X-ray detector.

[0030] Figure 4 This is a block diagram illustrating the configuration of an X-ray image capturing apparatus according to an embodiment of the present invention.

[0031] The X-ray image capturing apparatus according to the present invention includes: an imaging unit 40, including an X-ray generator (hereinafter referred to as the generator) and an X-ray detector (hereinafter referred to as the detector); a control unit 20, which controls X-ray image capturing by controlling the generator and the detector; an input unit 30, which receives imaging conditions and imaging mode selection inputs from the photographer; and a storage unit 30, which stores various information 31, 32, 33, and 34 required to generate control signals for the control unit 20. As an example, the generator may be a field emission type X-ray generator equipped with a carbon nanotube (CNT) emitter.

[0032] As one type of information, the storage unit 30 stores imaging information 31 for various imaging types of image medical examinations. The imaging information 31 may include imaging conditions such as tube voltage, tube current, irradiation time, X-ray dose (mAs: tube current × time), and imaging distance, according to the type of image medical examination that can be performed using the X-ray imaging apparatus according to this embodiment.

[0033] The storage unit 30 stores generator irradiation information 32 as one type of the various types of information. The generator irradiation information 32 may include at least one of the rise time, fall time, and interval time of the generator mounted on the corresponding X-ray imaging device. As an example, the generator irradiation information 32, as characteristic values ​​of the generator confirmed during the initial setup of the X-ray imaging device, may include the aforementioned rise time and fall time. When there are two or more generators mounted on the X-ray imaging device, the storage unit 30 stores generator irradiation information 33 for each generator.

[0034] The storage unit 30 stores detector detection information 33, which is one type of the various types of information. The detector detection information 33 may include at least one of the frame rate and read-out time of the detector mounted on the X-ray imaging device. Frame rate represents the speed at which the detector can acquire image data (i.e., the number of image frames per second), and read-out time represents the time required to transmit one frame of image data to the control unit 20. When there are two or more detectors mounted on the X-ray imaging device, the storage unit 30 may store the detector detection information 33 for each individual detector.

[0035] Furthermore, the storage unit 30 may store dose-pulse-image quality relationship information 34, which is one type of the various types of information. When irradiation is performed on multiple pulses with predetermined tube voltage and tube current values, divided into multiple X-ray dose values ​​included in the imaging information 31, information related to the relationship between the image quality index (e.g., SNR) value of the image acquired from the detector may be included in the dose-pulse-image quality relationship information 34. The predetermined tube voltage and tube current may be multiple values. The dose-pulse-image quality relationship information 34 may also be provided and used as a lookup table. The dose-pulse-image quality relationship information 34 may be created in such a way that when X-ray pulses are irradiated at a predetermined pulse rate (pulses per second), the X-ray dose and image quality according to the number of pulses are shown. The predetermined pulse rate may be multiple levels and may be equal to or higher than the frame rate of the detector included in the detector detection information 33. In other words, each frame of the detector may correspond to one or more pulses.

[0036] Figure 5 This is a flowchart illustrating an X-ray imaging method using an X-ray image imaging apparatus according to an embodiment of the present invention.

[0037] Here, let's refer together to the above. Figure 4 and Figure 5The control unit 20 is observed to use the information stored in the storage unit 30 to configure the X-ray imaging device according to this embodiment.

[0038] When X-ray image capture begins, the capture conditions (s1) are first input through the input unit 10 based on the X-ray image to be captured. For example, in the case of capturing an X-ray image equivalent to one of the standardized imaging medical examinations, the operator can select which part of the body to capture instead of inputting the capture conditions. At this time, the control unit 20 can load the capture conditions corresponding to the corresponding capture from the capture information 31 stored in the storage unit 30, and the operator can also adjust some of the loaded capture conditions through additional input.

[0039] Furthermore, in the shooting condition input step (s1), the photographer can selectively input one of several shooting modes, such as a low-dose mode and a high-quality mode, through the input unit 10. The control unit 20 can calculate the shooting unit control information 35 for controlling the shooting unit 40 when X-ray image is captured, using the shooting conditions pre-input based on the photographer's mode selection and the generator irradiation information 32, the detector detection information 33, and the dose-pulse-quality relationship information 34 pre-stored in the storage unit 30. Here, the calculation includes not only direct calculation but also finding a suitable value in a lookup table.

[0040] When the photographer selects a high-quality mode based on the shooting mode selection (s2), under the condition of irradiating the same X-ray dose as the shooting conditions input by the photographer, the imaging unit control information used to drive the generator and detector can be calculated to divide the corresponding dose into multiple pulses and irradiate, thereby acquiring projection data (s41). Even in this case, the number of irradiated X-ray pulses can be limited by setting an upper limit for the SNR value of the high-quality mode X-ray image, so that the SNR value of the expected image within the corresponding dose range does not exceed the upper limit. The high-quality mode can also be further subdivided into ordinary high-quality mode and ultra-high-quality mode, etc. In addition, it can also be configured as follows: during the process of forming an X-ray image while shooting, the projection data of multiple X-ray pulses is accumulated, the degree of improvement of the SNR of the X-ray image is checked, and if the value reaches the target value of the high-quality mode, the X-ray pulse irradiation is stopped.

[0041] When the photographer selects a low-dose mode based on the shooting mode selection (s2), imaging unit control information (s51) can be calculated. This imaging unit control information enables the provision of an X-ray image with the same image quality (SNR) as the shooting conditions input by the photographer, but at a lower dose than the X-ray dose required for the corresponding shooting conditions. The control unit 20 can use the pre-input shooting conditions and the generator irradiation information 32, the detector detection information 33, and the dose-pulse-image quality relationship information 34 pre-stored in the storage unit 30 to calculate imaging unit control information 35 for controlling the imaging unit 40 when the X-ray image is captured.

[0042] Compared to the imaging conditions loaded from the imaging information 31, which are based on existing X-ray generators that irradiate continuous X-rays, the X-ray image imaging apparatus according to the present invention can improve the image's SNR by irradiating pulsed X-rays as described above. Therefore, compared to the "tube current × time" (mAs) based on the imaging conditions, even if the X-ray dose irradiated to the subject is reduced by decreasing the sum of the tube current or the X-ray pulse irradiation time (mAs), the image quality level required for ordinary X-ray image imaging can be met. Therefore, the imaging unit control information 35 according to the low-dose mode has at least one smaller value than the tube current and time included in the imaging information 31. When considering that the generator irradiation information 32 and the detector detection information 33 control the generator and the detector at the maximum frame rate and a suitable pulse rate, the imaging unit control information 35 in the low-dose mode can be calculated by calculating the minimum number of pulses required to satisfy the image quality (SNR) conditions for the corresponding medical examination image.

[0043] As described above, if the imaging unit control information (s41, s51) is calculated, the control unit 20 will at least temporarily store the imaging unit control information 35 in the storage unit 30, and control the imaging unit 40 by using the imaging unit control information 35, thereby performing X-ray imaging according to each imaging mode (s42, s52).

[0044] Industrial availability This invention relates to an X-ray imaging device, which can be used in medical X-ray imaging devices and in industrial non-destructive testing X-ray imaging devices.

Claims

1. An X-ray image capturing device, comprising: The imaging unit includes an X-ray generator and an X-ray detector. The X-ray generator irradiates the subject with X-rays, and the X-ray detector receives the X-rays that have penetrated the subject and generates projection data frame by frame. The input unit receives imaging information including at least one of tube voltage, tube current, and irradiation time. The storage unit stores generator irradiation information including at least one of the rise time and fall time of the X-ray generator, detector detection information including at least one of the frame rate and readout time of the detector, and dose-pulse-quality relationship information regarding the relationship between X-ray dose, X-ray pulse number, and X-ray image quality. as well as The control unit calculates the number of X-ray pulses used for X-ray imaging of the subject based on the imaging information, the generator irradiation information, the detector detection information, and the dose-pulse-image quality relationship information.

2. The X-ray image capturing apparatus as described in claim 1, wherein, The control unit calculates the X-ray pulse rate of the X-ray source based on the number of X-ray pulses, adjusts the frame rate of the X-ray detector based on the X-ray pulse rate, and controls the X-ray generator and the X-ray detector to X-ray the subject during the irradiation time with the X-ray pulse rate and the adjusted frame rate.

3. The X-ray image capturing apparatus as described in claim 1, wherein, The X-ray dose based on the number of pulses is less than or equal to the X-ray dose based on the imaging information.

4. The X-ray image capturing apparatus as described in claim 1, wherein, The shooting information also includes: mode information, used to select low-dose mode and high-quality mode.

5. The X-ray image capturing apparatus as described in claim 4, wherein, The number of pulses of the X-ray generator in the low-dose mode is less than the number of pulses of the X-ray generator in the high-definition mode.

6. The X-ray image capturing apparatus as described in claim 1, wherein, The generator irradiation information also includes the interval time between X-ray pulses.

7. The X-ray image capturing apparatus as described in claim 6, wherein, The interval time is greater than or equal to the readout time of the detector.

8. The X-ray image capturing apparatus as described in claim 1, wherein, The image quality of the X-ray image includes the SNR value.

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