X-ray fluoroscope

Abstract

Provided is an X-ray fluoroscopy apparatus capable of appropriately performing X-ray photography after fluoroscopy. The X-ray fluoroscopy apparatus includes: an X-ray irradiation unit that irradiates an object with X-rays; a detector that detects X-rays that have passed through the object; a fluoroscopic image generation unit that generates a fluoroscopic image based on an output signal from the detector; a reference value acquisition unit that acquires a reference value that indicates brightness of an image captured in the fluoroscopic image; and an X-ray irradiation control unit that determines a photography condition for subsequent X-ray photography based on the reference value and a reference value that is a reference for the brightness.

Description

Technical Field

[0001] This invention relates to an X-ray imaging apparatus. Background Technology

[0002] Medical facilities are equipped with X-ray fluoroscopy equipment that irradiates a subject with X-rays and takes X-ray images. This X-ray fluoroscopy equipment is configured such that: first, continuous or pulsed X-rays are repeatedly irradiated toward the subject at a predetermined frame rate; after fluoroscopy, X-ray imaging (e.g., spot radiography) is performed.

[0003] To perform X-ray imaging, the thickness of the subject needs to be measured. Conventional X-ray fluoroscopy devices measure this thickness during the fluoroscopy phase before X-ray imaging. In conventional designs, the subject's thickness is measured using automatic control of the X-ray fluoroscopy exposure conditions. That is, existing X-ray fluoroscopy devices automatically adjust the X-ray exposure conditions to optimize the visibility of the image captured in the frames taken during fluoroscopy. For example, if the subject is thick, the X-ray exposure conditions are adjusted to increase the X-ray dose until optimal image visibility is achieved. Therefore, if the X-ray exposure conditions are stable during fluoroscopy, the adjustment of the X-ray fluoroscopy dose corresponding to the subject's thickness is complete. The subject's thickness is measured based on the final X-ray exposure conditions during fluoroscopy.

[0004] However, when the volume thickness is significantly thick or thin, image visibility may not be optimal even after changing the X-ray fluoroscopy irradiation conditions. This is because the X-ray irradiation conditions (e.g., tube voltage) during fluoroscopy have upper and lower limits. The volume thickness measurement methods described above require X-ray fluoroscopy irradiation conditions at the time point when image visibility is optimal, therefore, volume thickness cannot be measured in such cases. Regarding this issue, a technique for solving the above problem by adjusting the variable aperture attached to the image intensifier is described in the following prior art literature.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent No. 6432602 Specification Summary of the Invention

[0008] The problem the invention aims to solve

[0009] However, the existing technology has the following problem: the above solution cannot be used in X-ray fluoroscopy devices that do not have a variable aperture.

[0010] The present invention was made in view of this situation, and its object is to provide an X-ray fluoroscopic imaging apparatus capable of performing fluoroscopic X-ray imaging appropriately.

[0011] Solution for solving the problem

[0012] To achieve this objective, the present invention employs the following structure.

[0013] That is, the X-ray fluoroscopic imaging 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 an output signal from the detector; a reference value acquisition unit that acquires a reference value representing the brightness of the image captured in the fluoroscopic image; and an X-ray irradiation control unit that determines the imaging conditions for subsequent X-ray imaging based on the reference value and a reference value serving as a reference for the brightness.

[0014] The effects of the invention

[0015] 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 representing the brightness of the image captured in the fluoroscopy image and a target value serving as a reference for the brightness of the fluoroscopy image. By incorporating the aforementioned X-ray irradiation control unit, the X-ray fluoroscopy apparatus of the present invention enables appropriate subsequent X-ray imaging even when the subject is extremely thick or thin. Attached Figure Description

[0016] Figure 1 This is a functional block diagram illustrating the structure of the X-ray fluoroscopic imaging apparatus involved in the embodiments.

[0017] Figure 2 This is a flowchart illustrating the operation of the X-ray fluoroscopic imaging apparatus involved in the embodiments.

[0018] Figure 3 This is a schematic diagram illustrating the perspective image involved in the embodiment.

[0019] Figure 4 This is the table referenced by the body thickness calculation unit involved in the embodiment.

[0020] Figure 5 This is a table referenced by the X-ray irradiation control unit involved in the embodiment.

[0021] Figure 6 This is a schematic diagram illustrating the spot photography involved in the embodiment. Detailed Implementation

[0022] The X-ray fluoroscopy apparatus according to the embodiment will now be described with reference to the accompanying drawings. Furthermore, the following description will use a spot radiograph, performed after X-ray fluoroscopy, as an example of X-ray imaging. Figure 1 As shown, the X-ray fluoroscopy apparatus 1 according to the embodiment includes: a top plate 2 for mounting a subject in a horizontal position; an X-ray tube 3 disposed below the top plate 2 for irradiating the subject with X-rays; a detector 4 disposed above the top plate 2 for detecting X-rays that have passed through the subject; and a collimator 5 disposed between the top plate 2 and the X-ray tube 3 for limiting the irradiation range of the X-ray beam targeting the subject. The detector 4 is a flat panel detector. Flat panel detectors include indirect conversion type having a scintillator layer that converts X-rays into fluorescence and direct conversion type not having a scintillator layer that directly converts X-rays into electrical signals. In this example, either type of flat panel detector can be used.

[0023] 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 moving image generated when X-ray fluoroscopy is performed on a subject by repeatedly irradiating it with continuous X-rays or pulsed X-rays at a predetermined frame rate (e.g., 30 f / s). The fluoroscopic image generation unit 11 generates frames constituting the fluoroscopic image P in a time sequence based on the output signals sequentially output from the detector 4.

[0024] The reference value acquisition unit 12 acquires a reference value representing the brightness of the image captured in the perspective image P. The reference value is the average value of the pixel values ​​of the pixels constituting the perspective image P. The pixel values ​​can take values ​​in the range of 0 to 4,095, so the reference value is a value within this range.

[0025] The thickness calculation unit 13 estimates the thickness of the subject based on the X-ray fluoroscopy irradiation conditions and reference values. The thickness calculation unit 13 estimates the thickness of the subject using either of two modes. The first mode calculates the thickness of the subject based on the X-ray irradiation conditions during fluoroscopy, and the second mode calculates the thickness of the subject based on the reference values ​​during fluoroscopy. The second mode is used when the thickness is extremely thick or extremely thin; otherwise, the first mode is used.

[0026] 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 still image obtained by irradiating the subject with pulsed X-rays.

[0027] The X-ray irradiation control unit 21 is a control device for the X-ray tube 3, and controls the irradiation conditions for X-ray fluoroscopy within a configurable range. The X-ray irradiation control unit 21 transmits a control signal related to the tube voltage, tube current and irradiation time during X-ray fluoroscopy to the X-ray tube 3, and the X-ray tube 3 performs the X-ray irradiation operation based on the control signal. The tube voltage and tube current during X-ray fluoroscopy are specifically referred to as fluoroscopic tube voltage and fluoroscopic tube current.

[0028] The input unit 22 is a human-machine interface that receives operations from the surgeon related to the control of the X-ray fluoroscopic imaging apparatus 1, such as start of X-ray fluoroscopy, start of spot photography, and control of the collimator 5. The human-machine interface in this example is an operation panel or an operation console, for example.

[0029] The storage unit 23 stores information required for the operation of the X-ray fluoroscopic imaging apparatus 1, such as tables T1, T2, and T3 described later.

[0030] The main control unit 24 is a control device that uniformly controls each of the units 11, 12, 13, 14, and 21. The main control unit 24 is composed of a CPU (Central Processing Unit), and implements each of the units 11, 12, 13, 14, and 21 by executing various programs. Each unit may also be implemented by a processor independent of the main control unit 24. In addition, the main control unit 24 receives instructions for the X-ray fluoroscopic imaging apparatus 1 input by the surgeon via the input unit 22.

[0031] 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.

[0032] <Operation of X-ray Fluoroscopic Imaging Apparatus>

[0033] Next, the operation of X-ray fluoroscopic imaging will be described in accordance with Figure 2 the flow chart shown. As shown in step S1, the X-ray fluoroscopic imaging operation starts with X-ray fluoroscopy performed on a subject placed on the top plate 2. Regarding the fluoroscopic image P, although the subject can be observed in real time, the contrast of the captured image is low. The spot image SP obtained by the spot photography described later is suitable for appropriately diagnosing the lesion of the subject.

[0034] When X-ray fluoroscopy starts, the fluoroscopic image P is displayed on the monitor 31. The surgeon can move the top plate 2 relative to the X-ray tube 3 via the input unit 22 to adjust the opening of the collimator 5. When the adjustment related to the field of view is completed, the surgeon can operate via the input unit 22 as Figure 3As shown, a grid dividing the fluoroscopic image P into 4 rows and 4 columns of 16 segments is overlaid on the monitor 31. The surgeon can select any of the segments P1 to P16 of the fluoroscopic image P via the input unit 22. The selected segment is the area of ​​interest when obtaining a reference value representing the brightness of the X-ray fluoroscopy. When the surgeon selects any segment via the input unit 22, the process proceeds to step S2, where the acquisition of the reference value begins. In this example, the acquisition of the reference value continues until the X-ray fluoroscopy is completed. That is, the reference value is a dynamic parameter calculated for each frame constituting the fluoroscopic image.

[0035] For example, when the surgeon selects segment P15 via input unit 22, reference value acquisition unit 12 acquires a reference value based on the pixel values ​​of each pixel constituting segment P15. Specific examples of methods for acquiring the reference value include setting the average pixel value as the reference value, performing histogram analysis on segment P15, and setting the pixel value at the peak position as the reference value, etc. Furthermore, the surgeon can specify segments that avoid those containing air or metal components embedded in the subject among the 16 segments. Segments containing content outside the target area of ​​X-ray fluoroscopy are sometimes unsuitable for acquiring reference values ​​representing the brightness of X-ray fluoroscopy.

[0036] When the reference value is acquired, the process proceeds to step S3. In step S3, the reference value is compared with the target value stored in the storage unit 23. The target value corresponds to the reference value of the present invention. If the target value is equal to the reference value, the process proceeds to step S6 (described later); otherwise, the process proceeds to step S4. The target value is set to a brightness that ensures good visibility of the fluoroscopic image. Therefore, if the reference value is equal to the target value, the brightness of the fluoroscopic image is appropriate and 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.

[0037] In step S4, it is determined whether the X-ray fluoroscopy irradiation conditions are within the settable limits. If the determination is "yes," the process proceeds to step S6 (described later); if the determination is "no," the process proceeds to step S5. An upper and lower limit for the fluoroscopy tube voltage are specified for the X-ray tube 3. In step S4, it is determined whether the fluoroscopy tube voltage is the upper limit of 110kV; if the fluoroscopy tube voltage is 110kV, the determination is "yes." Additionally, in step S4, it is determined whether the fluoroscopy tube voltage is the lower limit of 40kV; if the fluoroscopy tube voltage is 40kV, the determination is "yes." Since the fluoroscopy tube voltage at the start of X-ray fluoroscopy is an intermediate value, this determination is "no," and the process proceeds to step S5.

[0038] In step S5, the X-ray fluoroscopy irradiation conditions are changed to bring the reference value closer to the target value. Therefore, if the reference value exceeds the target value, the X-ray irradiation control unit 21 controls the X-ray tube 3 to reduce the fluoroscopy tube voltage. Conversely, if the reference value is lower than 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.

[0039] If 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, when the reference value exceeds the target value, by repeating steps S3 to S5 several times, the fluoroscopic tube voltage gradually decreases until the reference value equals the target value. At this point, the feedback processing involved in steps S3 to S5 ends. Conversely, when the reference value is below the target value, by repeating steps S3 to S5 several times, the fluoroscopic tube voltage gradually increases until the reference value equals the target value. At this point, the feedback processing involved in steps S3 to S5 ends.

[0040] <Step S6: First Mode>

[0041] When the reference value and target value are equal when the fluoroscopy tube voltage is 100kV, the feedback process ends in a state where the fluoroscopy tube voltage has neither reached the upper nor lower limit. Therefore, in this case, step S3 determines "yes," and since the reference value is equal to the target value, the process exits the loop consisting of steps S3 to S5. The process then 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 based on the first mode described above. In the first mode, the body thickness calculation unit 13 reads from the storage unit 23... Figure 4 Table T1, shown at the top, provides the body thickness corresponding to the final fluoroscopy tube voltage. Table T1 illustrates the correlation between fluoroscopy tube voltage and body thickness under the condition that the fluoroscopy tube voltage is within the range from the lower to the upper limit when the reference and target values ​​are equal. Table T1 can be generated by actually fluoroscopying an acrylic sheet (phantom) used as the subject. That is, to create Table T1, multiple acrylic sheets with thicknesses ranging from 70mm to 270mm are prepared, each sheet is fluoroscopically examined, and the fluoroscopy tube voltage when the reference and target values ​​are equal is actually measured. In this example, since the fluoroscopy tube voltage is stable at 100kV, the estimated body thickness is 260mm. Incidentally, Figure 4 The value of the fluoroscopy tube current is a dependent variable that is determined along with the fluoroscopy tube voltage.

[0042] <Step S6: Second Mode>

[0043] The above description illustrates an example of estimating body thickness at the point in time when the reference value and the target value are equal during X-ray fluoroscopy. However, in cases of extremely thick body thickness, the reference value may not reach the target value during the feedback process described above. This is because an upper limit is specified for the fluoroscopy tube voltage. In this example, the body thickness can be appropriately estimated even in this case. Even if the fluoroscopy tube voltage reaches the upper limit of 110kV and the reference value is still lower than the target value, the feedback process ends with the fluoroscopy tube voltage reaching the upper limit. Therefore, in this case, it is determined to be "yes" in step S4, and the process exits the loop consisting of steps S3 to S5. Then, the process proceeds to step S6, where the body thickness of the subject is calculated based on the ratio (here, percentage) of the reference value to the target value. That is, the body thickness calculation unit 13 calculates the body thickness of the subject based on the second mode described above. In the second mode, the body thickness calculation unit 13 reads from the storage unit 23. Figure 4 The lower part of the table T2 is used to obtain the body thickness corresponding to the percentage and estimate the body thickness of the subject. Table T2 shows the correlation between percentage and body thickness under the condition that the fluoroscopy tube voltage is at the upper limit while keeping the reference value below the target value. For example, when the percentage is 50%, the body thickness calculation unit 13 estimates the body thickness to be 320 mm with reference to Table T2. That is, the body thickness calculation unit 13 estimates the body thickness by utilizing the phenomenon that the brightness of the fluoroscopy image decreases accordingly with the increase in body thickness when the X-ray fluoroscopy irradiation conditions are fixed.

[0044] Similarly, Table T2 also shows the relationship between percentage and body thickness under the condition that the fluoroscopy tube voltage becomes the lower limit while maintaining a reference value exceeding the target value. For example, when the percentage is 110%, the body thickness calculation unit 13 estimates the body thickness to be 40 mm with reference to Table T2. That is, the body thickness calculation unit 13 estimates the body thickness by utilizing the phenomenon that the brightness of the fluoroscopic image increases accordingly with the thinning of the body thickness when the X-ray irradiation conditions are fixed. Table T2 can be generated by actually fluoroscopying the acrylic plate, which is the subject of the examination.

[0045] Thus, with the fluoroscopy tube voltage set to maximum to prevent the reference value from falling below the target value, the aforementioned percentage is actually measured by fluoroscopy through a thick acrylic sheet, thereby generating Table T2. Conversely, with the fluoroscopy tube voltage set to minimum to prevent the reference value from exceeding the target value, the aforementioned percentage is actually measured by fluoroscopy through a thin acrylic sheet, thereby generating Table T2.

[0046] <Movements after estimating body thickness>

[0047] When the body thickness estimation based on the first or second mode is completed, the process proceeds to step S7, where the X-ray fluoroscopy is terminated upon instruction from the surgical operator via input unit 22. Afterwards, the process proceeds to step S8, where spot radiography is performed under the X-ray imaging conditions determined based on the body thickness calculated in step S6, upon instruction from the surgical operator via input unit 22. During spot radiography, the X-ray irradiation control unit 21 refers to the data stored in the storage unit 23. Figure 5 Table T3 is shown to obtain the X-ray imaging conditions corresponding to the estimated body thickness, under which spot radiography is performed. Figure 6 The dot film image SP, acquired through dot film radiography, is shown. The dot film image SP is a still image with higher contrast than a fluoroscopic image, suitable for various diagnostic procedures. The operation of the X-ray fluoroscopic radiography apparatus 1 in this example ends upon acquisition of the dot film image SP. Table T3 can be generated by actually performing X-ray radiography on the acrylic plate, which serves as the subject.

[0048] <Effects produced by the structure of the implementation method>

[0049] The structure and effects of the X-ray fluoroscopy device 1 in this example will be explained below.

[0050] (1) The X-ray fluoroscopy apparatus 1 in this example includes: an X-ray tube 3 that irradiates X-rays toward the 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 representing the brightness of the image captured in the fluoroscopic image; and an X-ray irradiation control unit 21 that determines the imaging conditions for subsequent X-ray radiography based on the reference value and a target value as a reference for brightness.

[0051] 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 used as a brightness benchmark. In this example, the X-ray fluoroscopy apparatus 1, by incorporating the aforementioned X-ray irradiation control unit 21, can calculate the thickness of the subject even when the subject's thickness is extremely thick or extremely thin.

[0052] (2) In the X-ray fluoroscopic imaging device described in (1), detector 4 is a flat panel detector.

[0053] As described above, if detector 4 is a flat panel detector, then compared to using an image intensifier as a detector, the device can be miniaturized. The reference value acquisition unit 12 in this example can also be applied to X-ray fluoroscopy apparatuses that do not have a variable aperture.

[0054] (3) In the X-ray fluoroscopic imaging apparatus described in (1) or (2), the X-ray irradiation control unit 12 controls the irradiation conditions of X-ray fluoroscopy within a settable range so that the reference value is close to the target value.

[0055] As described above, if the X-ray irradiation control unit 12 controls the irradiation conditions of X-ray fluoroscopy within a settable range so that the reference value is close to the target value, the brightness of the fluoroscopic image gradually approaches the reference, thereby improving the visibility of the fluoroscopic image.

[0056] (4) In the X-ray fluoroscopic imaging apparatus described in (3), even if the irradiation conditions reach the set limit value and the reference value does not become the target value, 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 the limit value.

[0057] If, as described above, the imaging conditions for subsequent X-ray radiography (i.e., spot radiography) are determined based on the target value and the reference value when the irradiation conditions are at their limits, even if the irradiation conditions reach the set limit value and the reference value does not become the target value, then subsequent X-ray radiography can be performed under appropriate imaging conditions even if the reference value does not become the target value.

[0058] (5) In the X-ray fluoroscopic imaging apparatus described in (3), a body thickness calculation unit 13 is also provided. The body thickness calculation unit 13 calculates the body thickness of the subject based on the irradiation conditions when the reference value becomes the target value. Even if the irradiation conditions reach the set limit value and the reference value does not become the target value, 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.

[0059] If the body thickness calculation unit 13 described above is provided, the body thickness, an important parameter for various X-ray imaging, can be calculated even when the reference value is not the target value. 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, even when the irradiation conditions reach the set limit value and the reference value is not the target value.

[0060] (6) In the X-ray fluoroscopic imaging 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.

[0061] As described above, if 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, then even in cases where the body thickness of the subject is extreme, X-ray imaging can be performed based on appropriate irradiation conditions. That is, according to the above structure, even when the irradiation conditions reach a set limit value or the reference value does not become the target value, the body thickness can still be calculated, and therefore various X-ray imaging methods can be performed based on the calculated body thickness.

[0062] (7) In any one of (1) to (6) of the X-ray fluoroscopic imaging apparatus, the reference value acquisition unit 12 acquires a reference value based on the brightness of each pixel in a specified area of ​​the fluoroscopic image.

[0063] As described above, if the reference value acquisition unit 12 acquires the reference value based on the brightness of each pixel within a specified area of ​​the fluoroscopic image, it can acquire the reference value without affecting the image area other than the subject captured in the fluoroscopic image, and can calculate the body thickness of the subject more accurately.

[0064] (8) In any one of (3) to (7) of the X-ray fluoroscopy apparatus, the X-ray irradiation control unit 21 performs the following control: changes 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 is close to the target value.

[0065] As described above, if the X-ray irradiation control unit 21 performs control to change the tube voltage of X-ray fluoroscopy so that the reference value is close to the target value, the reference value can be made closer to the target value as a reference for brightness more reliably.

[0066] (9) In the X-ray fluoroscopic imaging apparatus described in (5) or (6), even if the irradiation conditions reach a set limit value and the reference value does not become the target value, 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 the limit value.

[0067] 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 the limit value, even if the irradiation conditions reach the set limit value and the reference value does not become the target value, then the body thickness calculation unit 13 can easily calculate the body thickness of the subject using parameters that are easy to calculate.

[0068] <Other Embodiments>

[0069] Furthermore, the embodiments disclosed herein are illustrative in all respects and not restrictive. The scope of the invention includes the claims and all modifications within the meaning and scope of their equivalents. As an example, the invention can be modified and implemented as follows.

[0070] (1) The thickness calculation unit 13 and the X-ray irradiation control unit 21 can also use the equations corresponding to each table to replace T1, T2 and T3 to perform the operation.

[0071] (2) When generating tables T1, T2, and T3, acrylic is not required; other materials such as metal can also be used. Alternatively, the thickness of the subject can be determined by other methods, such as actual measurement using a ruler, and tables T1, T2, and T3 can be generated.

[0072] (3) The reference value acquisition unit 12 acquires reference values ​​based on the pixel values ​​of pixels contained in one segment of a fluoroscopic image divided into segments of a predetermined size (e.g., divided into 16 segments), but it can also acquire reference values ​​based on multiple segments. Alternatively, the reference value acquisition unit 12 can set a rectangular region of interest within the fluoroscopic image based on the center and size of the region specified by the surgical operator via the input unit 22, and acquire reference values ​​based on the region of interest. Of course, the reference value acquisition unit 12 can also acquire reference values ​​from the entire fluoroscopic image.

[0073] (4) The estimated body thickness can be used not only for spot radiography, but also for other radiographic methods such as subtraction angiography.

[0074] (5) Figure 4 The values ​​of the fluoroscopy tube voltage in Table T1 are shown below. Figure 4 The percentages in Table T2 shown below Figure 5 The volume thickness values ​​in Table T3 shown are actually a subset of the data stored in storage unit 23, but the amount of data in each table can be increased or decreased accordingly to the purpose of the device.

[0075] (6) In the above embodiments, the irradiation conditions for spot radiography are determined by estimating the thickness of the subject, but the present invention is not limited to this structure. A table relating fluoroscopy conditions to the irradiation conditions for spot radiography can also be created based on Table T1, which correlates fluoroscopy conditions with the thickness of the subject, and Table T3, which correlates the thickness of the subject with the irradiation conditions for spot radiography. Similarly, a table relating fluoroscopy conditions, percentages, and the thickness of the subject can also be created based on Tables T2 and T3. In this example, it is not necessary to estimate the thickness of the subject based on the radiographic conditions and percentages of the fluoroscopic image; the irradiation conditions for spot radiography can be calculated directly. The tables involved in this example can also be replaced with corresponding equations.

[0076] (7) In the above embodiments, X-ray dose adjustment was performed during the generation of the fluoroscopic image to make the reference value the target value, but the present invention is not limited to this structure. That is, it is also possible to omit the adjustment during the generation of the fluoroscopic image. Figure 2 The flowchart below explains the structure of steps S3 to S5. For example, the tube voltage is set to 70kV to perform the fluoroscopy in this example. With the percentage at 100%, the thickness of the subject is 180mm (refer to...). Figure 4 The thicker the specimen is compared to 180mm, the lower the percentage relative to 100; conversely, the thinner the specimen is compared to 180mm, the higher the percentage relative to 100. By actually performing X-ray examination on acrylic sheets (phantoms) of various thicknesses with a tube voltage of 70kV and calculating the percentages, a table representing the correlation between the specimen's thickness and the percentage can be derived.

[0077] (8) In the above embodiments, 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 structure. It can also be configured such that, instead of changing the tube voltage, the reference value is brought closer to the target value by changing any one of the following: tube current, X-ray pulse width, or beam hardening filter. In either case, it is possible to fabricate a model by actually viewing acrylic sheets (phantoms) of various thicknesses. Figure 4 Tables T1 and T2 are equivalent tables. In this example, the body thickness of the subject is estimated based on these tables.

[0078] Explanation of reference numerals in the attached figures

[0079] 1: X-ray fluoroscopic imaging device; 3: X-ray tube; 4: detector; 11: fluoroscopic image generation unit; 12: reference value acquisition unit; 13: body thickness calculation unit; 21: X-ray irradiation control unit.

Claims

1. An X-ray fluoroscopic imaging device, comprising: The X-ray irradiation section is directed towards the subject and irradiates it with X-rays. The detector detects X-rays that pass through the object being examined; A perspective image generation unit generates a perspective image based on the output signal from the detector; The reference value acquisition unit acquires a reference value representing the brightness of the image captured in the perspective image; as well as The X-ray irradiation control unit determines the imaging conditions for subsequent X-ray radiography based on the reference value and the reference value used as a reference for the brightness. The X-ray irradiation control unit controls the irradiation conditions of X-ray fluoroscopy within a settable range to make the reference value close to the baseline value. When the irradiation conditions are controlled within a settable range, such that the reference value is equal to the baseline value, the X-ray irradiation unit operates based on a first mode, in which the imaging conditions for subsequent X-ray imaging are calculated based on the irradiation conditions. Even if the irradiation conditions reach a set limit value and the reference value is not equal to the baseline value, the X-ray irradiation unit operates based on a second mode. In the second mode, the baseline value and the reference value when the irradiation conditions are at the limit value are obtained, and the imaging conditions for subsequent X-ray imaging are calculated based on the ratio of the baseline value to the reference value.

2. The X-ray fluoroscopic imaging apparatus according to claim 1, characterized in that, The detector is a flat panel detector.

3. The X-ray fluoroscopic imaging apparatus according to claim 1, characterized in that, The reference value acquisition unit acquires the reference value based on the brightness of each pixel within a specified area of ​​the perspective image.

4. The X-ray fluoroscopic imaging apparatus according to claim 1, characterized in that, The X-ray irradiation control unit performs the following control: changes 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 is close to the reference value.

5. An X-ray fluoroscopic imaging device, comprising: The X-ray irradiation section is directed towards the subject and irradiates it with X-rays. The detector detects X-rays that pass through the object being examined; A perspective image generation unit generates a perspective image based on the output signal from the detector; The reference value acquisition unit acquires a reference value representing the brightness of the image captured in the perspective image; The X-ray irradiation control unit determines the imaging conditions for subsequent X-ray imaging based on the reference value and the reference value used as a reference for the brightness. as well as The body thickness calculation unit calculates the body thickness of the subject based on the irradiation conditions when the reference value becomes the baseline value. The X-ray irradiation control unit controls the irradiation conditions of X-ray fluoroscopy within a settable range to make the reference value close to the baseline value. When the irradiation conditions are controlled within a settable range, such that the reference value is equal to the baseline value, the body thickness calculation unit operates based on a first mode, in which the body thickness is calculated based on the irradiation conditions. Even if the irradiation conditions reach a set limit value and the reference value is not equal to the baseline value, the body thickness calculation unit operates based on a second mode. In this second mode, it acquires the baseline value and the reference value when the irradiation conditions are at their limit value, and calculates the body thickness based on the ratio of the baseline value to the reference value. The X-ray irradiation control unit determines the X-ray imaging conditions based on the calculated body thickness.

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