X-ray fluoroscopy system

Abstract

To provide an X-ray fluoroscopic apparatus capable of properly taking radiography after fluoroscopy.SOLUTION: The X-ray fluoroscopic apparatus comprises: an X-ray irradiation part which irradiates a subject with X-rays; a detector which detects X-rays having passed through the analyte; a fluoroscopic image generation part which generates a fluoroscopic image based on an output signal from the detector; a reference value acquisition part which acquires a reference value indicative of the luminance of an image reflected in the fluoroscopic image; and an X-ray irradiation control part which determines radiography conditions of subsequent radiography based on the reference value and a reference value being the reference of the luminance.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an X-ray fluoroscopic imaging apparatus.

Background Art

[0002] In a medical field, an X-ray fluoroscopic imaging apparatus that irradiates a subject with X-rays to capture an X-ray image is deployed. Such an X-ray fluoroscopic imaging apparatus first repeatedly irradiates a subject with continuous X-rays or pulsed X-rays to perform fluoroscopy at a predetermined frame rate, and performs X-ray imaging (for example, spot imaging) after the fluoroscopy is completed.

[0003] To perform X-ray imaging, it is necessary to measure the thickness of the subject. Conventional X-ray fluoroscopic imaging apparatuses measure this thickness at the fluoroscopy stage before X-ray imaging. In the conventional configuration, the thickness of the subject is measured using automatic control of the irradiation conditions of X-ray fluoroscopy. That is, a conventional X-ray fluoroscopic imaging apparatus automatically changes the irradiation conditions of X-rays so that the visibility of the image captured in the frame captured at the fluoroscopy stage is optimized. For example, when the thickness of the subject is thick, the irradiation conditions of X-rays are changed to increase the dose of X-rays until the visibility of the image is optimized. Therefore, when the irradiation conditions of X-rays are stabilized at the fluoroscopy stage, it means that the adjustment of the dose of X-ray fluoroscopy according to the thickness has been completed. The thickness of the subject is measured based on the final irradiation conditions of X-rays at the fluoroscopy stage.

[0004] However, when the thickness is extremely thick or thin, the visibility of the image may not be optimized even if the irradiation conditions of X-ray fluoroscopy are changed. This is because there are upper and lower limits to the irradiation conditions (for example, tube voltage) of X-rays at the fluoroscopy stage. Since the above-described method for measuring the thickness requires the irradiation conditions of X-ray fluoroscopy when the visibility of the image is optimized, the thickness cannot be measured in such cases. In this regard, the following prior art documents describe a technique for solving the above problems by adjusting an iris diaphragm attached to an image intensifier.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Patent No. 6432602 specification [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, conventional technology has the following problems: Specifically, the above-mentioned solution cannot be used in X-ray fluoroscopy equipment that does not have an iris aperture.

[0007] This invention has been made in view of these circumstances, and aims to provide an X-ray fluoroscopy apparatus that can appropriately perform X-ray imaging after fluoroscopy. [Means for solving the problem]

[0008] To achieve this objective, the present invention has the following configuration. In other words, the X-ray fluoroscopy apparatus of the present invention comprises an X-ray irradiation unit that irradiates X-rays toward a subject, a detector that detects X-rays that have passed through the subject, a fluoroscopic image generation unit that generates a fluoroscopic image based on the output signal from the detector, a reference value acquisition unit that acquires a reference value indicating the brightness of the image captured in the fluoroscopic image, and an X-ray irradiation control unit that determines the shooting conditions for subsequent X-ray imaging based on the reference value and a reference value which is a standard for the brightness. [Effects of the Invention]

[0009] The X-ray fluoroscopy apparatus of the present invention includes an X-ray irradiation control unit that determines the imaging conditions for subsequent X-ray imaging based on a reference value indicating the brightness of the image captured in the fluoroscopic image and a target value which is a standard for the brightness of the fluoroscopic image. By including the above-mentioned X-ray irradiation control unit, the X-ray fluoroscopy apparatus of the present invention can appropriately perform subsequent X-ray imaging even when the body thickness of the subject is extremely thick or thin. [Brief explanation of the drawing]

[0010] [Figure 1] This is a functional block diagram illustrating the configuration of an X-ray fluoroscopy apparatus according to an embodiment. [Figure 2] This is a flowchart illustrating the operation of the X-ray fluoroscopy apparatus according to the embodiment. [Figure 3] This is a schematic diagram illustrating a perspective view related to the embodiment. [Figure 4] This is the table referenced by the body thickness calculation unit in the embodiment. [Figure 5] This is a table referenced by the X-ray irradiation control unit according to the embodiment. [Figure 6] This is a schematic diagram illustrating spot photography according to the embodiment. [Modes for carrying out the invention]

[0011] The following description of the X-ray fluoroscopy apparatus according to the embodiment will be explained with reference to the drawings. In the following description, the case in which spot imaging, an example of X-ray imaging, is performed following X-ray fluoroscopy will be used as an example. The X-ray fluoroscopy apparatus 1 according to the embodiment has, as shown in Figure 1, a top plate 2 on which a subject in a horizontal position is placed, an X-ray tube 3 positioned below the top plate 2 for irradiating the subject with X-rays, a detector 4 positioned above the top plate 2 for detecting X-rays that have passed through the subject, and a collimator 5 provided between the top plate 2 and the X-ray tube 3 to limit the irradiation range of the X-ray beam to the subject. The detector 4 is a flat panel detector. Flat panel detectors include indirect conversion types that have a scintillator layer that converts X-rays into fluorescence, and direct conversion types that do not have a scintillator layer and directly convert X-rays into electrical signals. In this example, either type of flat panel detector can be used.

[0012] The fluoroscopic image generation unit 11 generates a fluoroscopic image P based on the output signal from the detector 4. The fluoroscopic image P is a video generated when X-ray fluoroscopy is performed at a predetermined frame rate (e.g., 30 f / s) by repeatedly irradiating a subject with continuous X-rays or pulsed X-rays. The fluoroscopic image generation unit 11 generates frames that constitute the fluoroscopic image P in chronological order based on the output signals successively output from the detector 4.

[0013] The reference value acquisition unit 12 acquires a reference value indicating the luminance of the image reflected in the fluoroscopic image P. The reference value is the average value of the pixel values of the pixels constituting the fluoroscopic image P. Since the pixel value can take a value in the range from 0 to 4,095, the reference value is a value within this range.

[0014] The body thickness calculation unit 13 estimates the body thickness of the subject from the irradiation conditions of the X-ray fluoroscopy and the reference value. The body thickness calculation unit 13 estimates the body thickness of the subject in either of two modes. The first mode is a mode of calculating the body thickness of the subject from the X-ray irradiation conditions during fluoroscopy, and the second mode is a mode of calculating the body thickness of the subject from the reference value during fluoroscopy. The second mode is used when the body thickness is extremely thick or extremely thin, and the first mode is used in other cases.

[0015] The spot image generation unit 14 generates a spot image SP based on the output signal from the detector 4. The spot image SP is a single still image obtained by irradiating the subject with pulsed X-rays.

[0016] The X-ray irradiation control unit 21 is a control device for the X-ray tube 3 and controls within a range where the irradiation conditions of the X-ray fluoroscopy can be set. The X-ray irradiation control unit 21 transmits control signals regarding the tube voltage, tube current, and irradiation time in the X-ray fluoroscopy to the X-ray tube 3, and the X-ray tube 3 performs an X-ray irradiation operation based on this control signal. The tube voltage and tube current during X-ray fluoroscopy are particularly referred to as the fluoroscopy tube voltage and the fluoroscopy tube current.

[0017] The input unit 22 is a human interface that receives an operator's operations related to the control of the X-ray fluoroscopy imaging apparatus 1, such as the start of X-ray fluoroscopy, the start of spot imaging, and the control of the collimator 5. The human interface in this example is, for example, an operation panel or an operating table.

[0018] The storage unit 23 stores information necessary for the operation of the X-ray fluoroscopy imaging apparatus 1, such as the tables T1, T2, T3, etc., described later.

[0019] The main control unit 24 is a control device that comprehensively controls each unit 11, 12, 13, 14, 21. The main control unit 24 is composed of a CPU (Central Processing Unit) and realizes each unit 11, 12, 13, 14, 21 by executing various programs. Each unit may be realized by an independent processor from the main control unit 24. Also, the main control unit 24 receives an instruction from an operator for the X-ray fluoroscopic imaging apparatus 1 through the input unit 22.

[0020] The monitor 31 displays the fluoroscopic image P generated by the fluoroscopic image generation unit 11 and the spot image SP generated by the spot image generation unit 14.

[0021] <Operation of the X-ray fluoroscopic imaging apparatus> Hereinafter, the operation of X-ray fluoroscopy will be described according to the flowchart shown in FIG. 2. The operation of X-ray fluoroscopy starts with X-ray fluoroscopy of the subject placed on the top plate 2 as shown in step S1. The fluoroscopic image P can observe the subject in real time, but the contrast of the image to be captured is low. To appropriately diagnose a lesion of the subject, the spot image SP obtained by spot imaging described later is suitable.

[0022] When X-ray fluoroscopy is started, the fluoroscopic image P is displayed on the monitor 31. The operator can move the top plate 2 relative to the X-ray tube 3 through the input unit 22 and adjust the opening degree of the collimator 5. When the adjustment regarding the field of view is completed, the operator can, through the input unit 22, superimpose and display a grid that divides the fluoroscopic image P on the monitor 31 into 16 parts in 4 rows and 4 columns as shown in FIG. 3 on the fluoroscopic image P. The operator can select any one of the fragments P1 to P16 of the fluoroscopic image P through the input unit 22. The selected fragment becomes the attention area when obtaining a reference value indicating the luminance of X-ray fluoroscopy. When the operator selects any one of the fragments through the input unit 22, the process proceeds to step S2 and the acquisition of the reference value is started. In this example, the acquisition of this reference value continues until the X-ray fluoroscopy ends. That is, the reference value is a dynamic parameter calculated for each frame constituting the fluoroscopic image.

[0023] For example, when the operator selects fragment P15 through the input unit 22, the reference value acquisition unit 12 acquires a reference value based on the pixel values ​​of each pixel constituting fragment P15. Specific examples of methods for acquiring the reference value include using the average value of the pixel values ​​as the reference value, or performing a histogram analysis on fragment P15 and using the pixel value where the peak is located as the reference value. The operator can also specify fragments from among the 16 fragments, avoiding fragments that, for example, reflect air or metal components embedded in the subject. Fragments that reflect things other than the purpose of X-ray fluoroscopy may not be suitable for acquiring a reference value indicating the brightness of the X-ray fluoroscopy.

[0024] When the acquisition of the reference value begins, the process proceeds to step S3. In step S3, the reference value is compared with the target value stored in the memory unit 23. The target value corresponds to the reference value of the present invention. If the target value and the reference value are equal, the process proceeds to step S6 described below; otherwise, the process proceeds to step S4. The target value is set to a brightness level that provides good visibility of the fluoroscopic image. Therefore, if the reference value is equal to the target value, the fluoroscopic image at that time will have appropriate brightness and be easy to observe. Generally, the reference value at the start of X-ray fluoroscopy is not equal to the target value, and the process proceeds to step S4.

[0025] In step S4, it is determined whether the irradiation conditions for X-ray fluoroscopy are at the settable limit. If this determination is true, the process proceeds to step S6 described below; otherwise, the process proceeds to step S5. The X-ray tube 3 has defined upper and lower limits for the fluoroscopy tube voltage. In step S4, it is determined whether the fluoroscopy tube voltage is at the upper limit of 110kV. If the fluoroscopy tube voltage is 110kV, the determination is true. Also in step S4, it is determined whether the fluoroscopy tube voltage is at the lower limit of 40kV. If the fluoroscopy tube voltage is 40kV, the determination is true. Since the fluoroscopy tube voltage at the start of X-ray fluoroscopy is an intermediate value, this determination is false, and the process proceeds to step S5.

[0026] In step S5, the irradiation conditions for X-ray fluoroscopy are changed so that the reference value approaches the target value. Therefore, if the reference value is above the target value, the X-ray irradiation control unit 21 controls the X-ray tube 3 to lower the fluoroscopy tube voltage. If the reference value is below the target value, the X-ray irradiation control unit 21 controls the X-ray tube 3 to increase the fluoroscopy tube voltage. After step S5, the process returns to step S3.

[0027] As steps S3 to S5 are repeated, the reference value gradually approaches the target value, and consequently, the visibility of the fluoroscopic image P improves. That is, if the reference value is above the target value, the fluoroscopic tube voltage gradually decreases as steps S3 to S5 are repeated several times, and eventually the reference value becomes equal to the target value. At this point, the feedback process related to steps S3 to S5 is completed. On the other hand, if the reference value is below the target value, the fluoroscopic tube voltage gradually increases as steps S3 to S5 are repeated several times, and eventually the reference value becomes equal to the target value. At this point, the feedback process related to steps S3 to S5 is completed.

[0028] <Step S6: First Mode> When the fluoroscopy tube voltage is 100kV and the reference value equals the target value, the feedback process described above ends with the fluoroscopy tube voltage not reaching either the upper or lower limit. Therefore, in this case, the process exits the loop consisting of steps S3 to S5 because step S3 becomes true. Then, the process proceeds to step S6, where the body thickness of the subject is calculated based on the final fluoroscopy tube voltage. That is, the body thickness calculation unit 13 calculates the body thickness of the subject using the first mode described above. In the first mode, the body thickness calculation unit 13 reads the table T1 shown in the upper part of Figure 4 from the storage unit 23 to obtain the body thickness corresponding to the final fluoroscopy tube voltage. Table T1 shows the relationship between the fluoroscopy tube voltage and body thickness under the condition that the fluoroscopy tube voltage when the reference value equals the target value is within the range from the lower limit to the upper limit. Table T1 can be generated by actually fluoroscopying an acrylic plate (phantom) that represents the subject. In other words, to create table T1, multiple acrylic plates with thicknesses ranging from 70 mm to 270 mm are prepared, and each acrylic plate is subjected to X-ray fluoroscopy. The fluoroscopy tube voltage is measured when the reference value equals the target value. In this example, since the fluoroscopy tube voltage stabilized at 100 kV, the thickness is estimated to be 260 mm. Incidentally, the value of the fluoroscopy tube current in Figure 4 is a dependent variable that is determined in conjunction with the determination of the fluoroscopy tube voltage.

[0029] <Step S6: Second Mode> The above explanation shows an example where body thickness is estimated when the reference value equals the target value in X-ray fluoroscopy. However, if the body thickness is extremely thick, for example, the reference value will never reach the target value in the above feedback process. This is because there is an upper limit on the fluoroscopy tube voltage. In this example, body thickness can be estimated appropriately even in this case. If the reference value is still below the target value even when the fluoroscopy tube voltage reaches the upper limit of 110kV, the above feedback process ends when the fluoroscopy tube voltage reaches the upper limit. Therefore, in this case, the process exits the loop consisting of steps S3 to S5 when step S4 becomes true. Then, the process proceeds to step S6, where the body thickness of the subject is calculated based on the ratio (in this case, a percentage) of the reference value to the target value. That is, the body thickness calculation unit 13 calculates the body thickness of the subject using the second mode described above. In the second mode, the body thickness calculation unit 13 reads table T2, shown in the lower part of Figure 4, from the storage unit 23 to obtain the body thickness corresponding to the percentage and estimate the body thickness of the subject. Table T2 shows the relationship between percentage and body thickness under conditions where the reference value is below the target value and the fluoroscopy tube voltage is at its upper limit. For example, if the percentage is 50%, the body thickness calculation unit 13 estimates the body thickness to be 320 mm by referring to table T2. In other words, the body thickness calculation unit 13 estimates the body thickness by utilizing the phenomenon that the brightness of the fluoroscopic image decreases as the body thickness increases when the irradiation conditions for X-ray fluoroscopy are constant.

[0030] Similarly, Table T2 also shows the relationship between percentage and body thickness under conditions where the reference value is above the target value while the fluoroscopy tube voltage is at its lower limit. For example, if the percentage is 110%, the body thickness calculation unit 13 estimates the body thickness to be 40 mm by referring to Table T2. In other words, the body thickness calculation unit 13 estimates the body thickness by utilizing the phenomenon that, when the X-ray irradiation conditions are constant, the brightness of the fluoroscopic image increases as the body thickness decreases. Table T2 can be generated by actually fluoroscopying an acrylic plate representing the subject.

[0031] Thus, Table T2 is generated by measuring the aforementioned percentage by performing a transparent inspection of a thick acrylic plate with the transparent tube voltage set to maximum, in case the reference value falls below the target value. Also, Table T2 is generated by measuring the aforementioned percentage by performing a transparent inspection of a thin acrylic plate with the transparent tube voltage set to minimum, in case the reference value exceeds the target value.

[0032] <Actions after body thickness estimation> Once the body thickness estimation is completed based on the first or second mode, the process proceeds to step S7, where X-ray fluoroscopy is completed based on instructions from the operator via the input unit 22. Subsequently, the process proceeds to step S8, where spot imaging is performed based on the X-ray irradiation conditions determined based on the body thickness obtained in step S6, based on instructions from the operator via the input unit 22. During spot imaging, the X-ray irradiation control unit 21 refers to the table T3 shown in Figure 5, which is stored in the memory unit 23, to obtain the X-ray irradiation conditions corresponding to the estimated body thickness, and spot imaging is performed under these conditions. Figure 6 shows the spot image SP obtained by spot imaging. The spot image SP is a still image with higher contrast than the fluoroscopic image and is suitable for various diagnoses. The operation of the X-ray fluoroscopy apparatus 1 in this example is completed upon acquisition of the spot image SP. Table T3 can be generated by actually X-ray imaging an acrylic plate representing the subject.

[0033] <Effects of the configuration of the embodiment> The configuration of the X-ray fluoroscopy apparatus 1 in this example and its effects will be explained below. (1) The X-ray fluoroscopy apparatus 1 in this example comprises an X-ray tube 3 that irradiates X-rays toward a subject, a detector 4 that detects X-rays that have passed through the subject, a fluoroscopic image generation unit 11 that generates a fluoroscopic image based on the output signal from the detector 4, a reference value acquisition unit 12 that acquires a reference value indicating the brightness of the image captured in the fluoroscopic image, and an X-ray irradiation control unit 21 that determines the shooting conditions for subsequent X-ray imaging based on the reference value and a target value which is a brightness standard.

[0034] According to the X-ray fluoroscopy apparatus 1 described above, the X-ray irradiation control unit 21 determines the imaging conditions for subsequent X-ray imaging based on a reference value and a target value which is a brightness standard. The X-ray fluoroscopy apparatus 1 in this example, by including the X-ray irradiation control unit 21 described above, can calculate the body thickness even when the body thickness of the subject is extremely thick or extremely thin.

[0035] (2) In the X-ray fluoroscopy apparatus described in (1), the detector 4 is a flat panel detector.

[0036] As described above, if the detector 4 is a flat panel detector, the device can be made smaller than if an image intensifier were used as the detector. The reference value acquisition unit 12 in this example can also be applied to X-ray fluoroscopy devices that do not have an iris aperture.

[0037] (3) In the X-ray fluoroscopy apparatus described in (1) or (2), the X-ray irradiation control unit 12 controls the irradiation conditions for X-ray fluoroscopy within a settable range so that the reference value approaches the target value.

[0038] As described above, if the X-ray irradiation control unit 12 controls the irradiation conditions for X-ray fluoroscopy within a settable range so that the reference value approaches the target value, the brightness of the fluoroscopic image will gradually approach the reference, thereby improving the visibility of the fluoroscopic image.

[0039] (4) In the X-ray fluoroscopy apparatus described in (3), the X-ray irradiation control unit 12 determines the imaging conditions for subsequent X-ray imaging based on the target value and the reference value when the irradiation conditions are at their limit, if the reference value does not become the target value even when the irradiation conditions reach the settable limit value.

[0040] As described above, if the reference value does not become the target value even when the irradiation conditions reach the settable limit, the shooting conditions for subsequent spot X-ray imaging can be determined based on the target value and the reference value when the irradiation conditions are at their limit. This allows subsequent X-ray imaging to be performed under appropriate shooting conditions even if the reference value does not become the target value.

[0041] (5) The X-ray fluoroscopy apparatus described in (3) is equipped with a body thickness calculation unit 13 that calculates the body thickness of a subject from the irradiation conditions when the reference value becomes the target value, and the body thickness calculation unit 13 calculates the body thickness based on the target value and the reference value when the irradiation conditions are at the limit value when the reference value does not become the target value even when the irradiation conditions reach the limit value which can be set.

[0042] As described above, if the reference value does not become the target value even when the irradiation conditions reach the settable limit, a body thickness calculation unit 13 is provided that calculates the body thickness based on the target value and the reference value when the irradiation conditions are at the limit. This makes it possible to calculate the body thickness, which is an important parameter when performing various X-ray imaging, even when the reference value does not become the target value.

[0043] (6) In the X-ray fluoroscopy apparatus described in (5), the X-ray irradiation control unit 21 determines the irradiation conditions for subsequent X-ray imaging based on the body thickness of the subject calculated by the body thickness calculation unit 13.

[0044] As described above, the X-ray irradiation control unit 21 determines the irradiation conditions for X-ray imaging based on the body thickness of the subject calculated by the body thickness calculation unit 13, making it possible to perform X-ray imaging based on appropriate irradiation conditions even when the subject's body thickness is extreme. In other words, with the above configuration, even if the irradiation conditions reach the limit value that can be set and the reference value does not become the target value, it is still possible to calculate the body thickness, and therefore various types of X-ray imaging can be performed based on the calculated body thickness.

[0045] (7) In the X-ray fluoroscopy apparatus described in any of (1) to (6), the reference value acquisition unit 12 acquires a reference value based on the brightness of each pixel in a predetermined area of ​​the fluoroscopic image.

[0046] As described above, if the reference value acquisition unit 12 acquires a reference value based on the brightness of each pixel in a predetermined area of ​​the translucent image, it is possible to acquire a reference value while avoiding images other than the subject that are captured in the translucent image, and thus it becomes possible to calculate the body thickness of the subject more accurately.

[0047] (8) In the X-ray fluoroscopy apparatus described in any of (3) to (7), the X-ray irradiation control unit 21 performs control to change at least one of the X-ray fluoroscopy tube voltage, tube current, pulse width, and beam hardening filter so that the reference value approaches the target value.

[0048] As described above, if the X-ray irradiation control unit 21 performs control to change the tube voltage of the X-ray fluoroscopy so that the reference value approaches the target value, the reference value can be brought closer to the target value, which is the brightness standard, more reliably.

[0049] (9) In the X-ray fluoroscopy apparatus described in (5) or (6), the body thickness calculation unit 13 calculates the body thickness based on the ratio of the target value to the reference value when the irradiation conditions are at their limit, if the reference value does not become the target value even when the irradiation conditions reach the limit value which can be set.

[0050] As described above, if the body thickness calculation unit 13 calculates the body thickness based on the ratio of the target value to the reference value when the irradiation conditions are at their limit, even when the reference value does not reach the target value when the irradiation conditions reach the limit value, the body thickness calculation unit 13 can easily calculate the body thickness of the subject using parameters that are easy to calculate.

[0051] <Other examples> The embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention includes the claims and all modifications within the meaning and scope of equivalence to the claims. For example, the present invention can be modified and implemented as follows.

[0052] (1) The body thickness calculation unit 13 and the X-ray irradiation control unit 21 may operate using equations corresponding to each table instead of tables T1, T2, and T3.

[0053] (2) When producing tables T1, T2, and T3, it is not necessary to use acrylic; other materials such as metal may be used. Alternatively, the thickness of the subject may be measured by other methods, such as by measuring with a tape measure, and tables T1, T2, and T3 may be produced based on that measurement.

[0054] (3) The reference value acquisition unit 12 was configured to acquire a reference value from the pixel value of a pixel included in one of the fragments formed by dividing the fluoroscopic image into predetermined sizes (for example, 16 divisions), but it may also acquire a reference value based on multiple fragments. Alternatively, the reference value acquisition unit 12 may set up a rectangular area of ​​interest within the fluoroscopic image based on the operator's specification of the center and size of the area through the input unit 22, and acquire a reference value based on the area of ​​interest. Of course, the reference value acquisition unit 12 may also acquire a reference value from the entire fluoroscopic image.

[0055] (4) The estimated body thickness can be used for other imaging techniques such as subtraction angiography in addition to spot imaging.

[0056] (5) The values ​​of the fluoroscopy tube voltage in table T1 shown in Figure 4, the percentages in table T2 shown in Figure 4, and the body thickness values ​​in table T3 shown in Figure 5 are excerpts from the data actually stored in the memory unit 23, but the number of data points in each table can be increased or decreased according to the purpose of the device.

[0057] (6) In the above-described embodiment, the irradiation conditions for X-ray imaging in spot imaging were determined by estimating the body thickness of the subject, but the present invention is not limited to this configuration. A table relating fluoroscopic conditions and X-ray imaging irradiation conditions in spot imaging may be created based on Table T1 relating fluoroscopic conditions and the body thickness of the subject, and Table T3 relating the body thickness of the subject and the X-ray imaging irradiation conditions in spot imaging. Similarly, a table relating fluoroscopic conditions, percentages, and X-ray imaging irradiation conditions in spot imaging may be created based on Tables T2 and T3 relating fluoroscopic conditions, percentages, and the body thickness of the subject. In this example, the X-ray imaging irradiation conditions in spot imaging can be calculated directly without estimating the body thickness of the subject based on the imaging conditions and percentages of the fluoroscopic image. The tables in this example can also be replaced with corresponding equations.

[0058] (7) In the above-described embodiment, the X-ray dose was adjusted so that the reference value became the target value during the generation of the fluoroscopic image, but the present invention is not limited to this configuration. That is, a configuration can be made in which steps S3 to S5 of the flowchart described in Figure 2 are omitted. In this example, fluoroscopy is performed with the tube voltage set to 70kV. When the percentage at this time is 100, it can be seen that the body thickness of the subject is 180mm (see Figure 4). As the body thickness of the subject increases from 180mm, the percentage decreases from 100, and as the body thickness of the subject decreases from 180mm, the percentage increases from 100. A table showing the relationship between the thickness of the subject and the percentage can be obtained by actually fluoroscopying acrylic plates (phantoms) of various thicknesses with the tube voltage set to 70kV and calculating the percentage.

[0059] (8) In the embodiments described above, control was performed to bring the reference value closer to the target value by changing the tube voltage, but the present invention is not limited to this configuration. Instead of the tube voltage, the reference value may be brought closer to the target value by changing the tube current, the pulse width of the X-ray pulse, or the beam hardening filter. In any case, tables corresponding to tables T1 and T2 in Figure 4 can be created by actually viewing acrylic plates (phantoms) of various thicknesses. In this example, the body thickness of the subject is estimated based on these tables. [Explanation of symbols]

[0060] 1. X-ray fluoroscopy device 3 X-ray tube 4 detectors 11 Fluoroscopic image generation section 12. Reference Value Acquisition Section 13 Body Thickness Calculation Section 21 X-ray irradiation control unit

Claims

1. An X-ray irradiation unit that irradiates the subject with X-rays, A detector that detects X-rays that have passed through the subject, A translucent image generation unit generates a translucent image based on the output signal from the detector, A reference value acquisition unit that acquires a reference value indicating the brightness of the image reflected in the perspective image, The system includes an X-ray irradiation control unit that determines the imaging conditions for subsequent X-ray imaging based on the aforementioned reference value and the aforementioned reference value which is the brightness standard, The X-ray irradiation control unit controls the irradiation conditions for X-ray fluoroscopy within a settable range so that the reference value approaches the reference value. The aforementioned X-ray irradiation control unit is When the irradiation conditions are controlled within a settable range and the reference value becomes equal to the reference value, a first mode calculates the imaging conditions for subsequent X-ray imaging based on the irradiation conditions, A second mode is provided in which, if the reference value does not become equal to the standard value even when the irradiation conditions reach a settable limit, the standard value and the reference value when the irradiation conditions are at their limit are obtained, and the imaging conditions for subsequent X-ray imaging are calculated based on the ratio of the standard value and the reference value. An X-ray fluoroscopy system that operates based on [a specific principle / system].

2. An X-ray irradiation unit that irradiates the subject with X-rays, A detector that detects X-rays that have passed through the subject, A translucent image generation unit generates a translucent image based on the output signal from the detector, A reference value acquisition unit that acquires a reference value indicating the brightness of the image reflected in the perspective image, An X-ray irradiation control unit that determines the imaging conditions for subsequent X-ray imaging based on the aforementioned reference value and the aforementioned reference value which is the brightness standard, The system includes a body thickness calculation unit that calculates the body thickness of a subject from the irradiation conditions when the reference value becomes the reference value. The X-ray irradiation control unit controls the irradiation conditions for X-ray fluoroscopy within a settable range so that the reference value approaches the reference value. The aforementioned body thickness calculation unit is When the irradiation conditions are controlled within a settable range and the reference value becomes equal to the reference value, a first mode is used to calculate the body thickness based on the irradiation conditions, A second mode is provided in which, if the reference value does not become equal to the standard value even when the irradiation conditions reach a settable limit, the standard value and the reference value when the irradiation conditions are at the limit are obtained, and the body thickness is calculated based on the ratio of the standard value and the reference value. It operates based on, The aforementioned X-ray irradiation control unit is an X-ray fluoroscopy apparatus that determines the imaging conditions for the X-ray imaging based on the calculated body thickness.

3. In the X-ray fluoroscopy apparatus according to claim 1 or claim 2, The detector is an X-ray fluoroscopy device, which is a flat panel detector.

4. In the X-ray fluoroscopy apparatus according to any one of claims 1 to 3, The reference value acquisition unit is an X-ray fluoroscopy apparatus that acquires the reference value based on the brightness of each pixel in a predetermined region of the fluoroscopic image.

5. In the X-ray fluoroscopy apparatus according to any one of claims 1 to 4, An X-ray fluoroscopy apparatus in which the X-ray irradiation control unit performs control to change at least one of the tube voltage, tube current, pulse width, and beam hardening filter of the X-ray fluoroscopy so that the reference value approaches the reference value.

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