Radiation inspection device

Abstract

To provide a radiation inspection device that can acquire a transparent image with high image quality regardless of the level of skill of a user by automatically adjusting the thickness or material of a filter.SOLUTION: A radiation inspection device comprises: a radiation source 2 that emits a radiation beam; a detector 3 that is provided opposite to the radiation source 2 and receives input of the radiation beam; a filter adjustment unit 4 that adjusts the attenuation factor of a filter F provided between the radiation source 2 and the detector 3 so as to attenuate the signal quantity I0 of radiation beam input to the detector 3; and a determination unit 942 that compares the signal quantity I0 of the radiation beam with a predetermined signal quantity Is. The filter adjustment unit 4 adjusts the attenuation factor of the filter F so that the signal quantity I0 of the radiation beam becomes equal to or less than the predetermined signal quantity Is.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a radiological inspection apparatus. [Background technology]

[0002] A radiation inspection device includes a radiation source that emits radiation, such as an X-ray beam, and a detector that is disposed opposite the radiation source and detects the X-ray beam. An inspection table on which an object to be inspected is placed is disposed between the radiation source and the detector, and a fluoroscopic image of the object to be inspected is obtained by irradiating the object with the X-ray beam. Furthermore, by rotating the inspection table once while the object to be inspected is irradiated with the X-ray beam, fluoroscopic images from all directions are obtained. A CT image (cross-sectional image) of the object to be inspected is obtained by reconstructing this fluoroscopic image.

[0003] It is known that filters are used to reduce noise, such as scattered radiation and metal artifacts, caused by the object being inspected when acquiring fluoroscopic images. A filter is a shielding plate made of metal or other material, and is placed in front of a radiation source to attenuate the X-ray beam input from the radiation source to a detector. This reduces the noise described above. However, changing the thickness or material of the filter to further attenuate the X-ray beam can reduce the amount of X-ray signal input to the detector even more than the noise, potentially lowering the signal-to-noise ratio of the fluoroscopic image. In conventional techniques, users adjust the thickness or material of the filter while taking this into consideration. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-132859 [Patent Document 2] Japanese Patent Application Publication No. 63-111107 Summary of the Invention [Problem to be solved by the invention]

[0005] However, adjusting the filter thickness or material while checking a fluoroscopic image requires many years of experience, and therefore a radiological examination device that allows even inexperienced users to easily adjust the filter thickness or material has been long awaited. Furthermore, adjustment of the filter thickness or material is required every time settings before imaging, such as the voltage or current applied to the radiation source or the positional relationship of each component, such as the distance from the radiation source to the detector (Focus to Detector Distance (FDD)), and therefore remains a time-consuming task even for experienced users.

[0006] In order to solve the above problem, the present embodiment aims to provide a radiological examination device that can easily obtain high-quality fluoroscopic images regardless of the user's level of skill by automatically adjusting the thickness or material of the filter. [Means for solving the problem]

[0007] The radiation inspection apparatus of the first embodiment has the following configuration. (1) A radiation source that emits a beam of radiation. (2) a detector that is disposed opposite the radiation source and into which the radiation beam is incident; (3) A filter adjustment unit that adjusts the attenuation rate of a filter provided between the radiation source and the detector in order to attenuate the signal amount of the radiation beam input to the detector. (4) A determination unit that compares the signal amount of the radiation beam with a predetermined signal amount. (5) The filter adjustment unit adjusts the attenuation rate of the filter so that the signal amount of the radiation beam is equal to or less than the predetermined signal amount.

[0008] The radiation inspection apparatus of the first embodiment may further include the following configuration. (1) The filter adjustment unit adjusts the attenuation rates of the filters by replacing the filters in ascending order of attenuation rates.

[0009] The radiation inspection apparatus of the second embodiment has the following configuration. (1) A radiation source that emits a beam of radiation. (2) a detector that is disposed opposite the radiation source and into which the radiation beam is incident; (3) A filter adjustment unit that adjusts the attenuation rate of a filter provided between the radiation source and the detector in order to attenuate the signal amount of the radiation beam input to the detector. (4) A calculation unit for calculating the thickness of the filter as a function of the signal amount of the radiation beam. (5) The filter adjustment unit adjusts the attenuation factor of the filter based on the thickness of the filter calculated by the calculation unit.

[0010] The radiation inspection apparatus of the second embodiment may further include the following configuration. (1) The calculation unit calculates the thickness of the filter based on a filter thickness curve that indicates the relationship between the thickness of the filter and the signal amount of the radiation beam.

[0011] (2) The filter thickness curve is expressed by the following equation:

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[0012] [Figure 1] FIG. 1 is a schematic diagram showing a radiological inspection apparatus according to an embodiment. [Figure 2] FIG. 2 is a functional block diagram showing a control unit according to the first embodiment. [Figure 3] 5 is a flowchart showing the operation of the radiological inspection apparatus according to the first embodiment. [Figure 4] FIG. 10 is a functional block diagram showing a control unit according to a second embodiment. [Figure 5]10 is a graph showing a filter thickness curve according to a second embodiment. [Figure 6] 10 is a flowchart showing the operation of the radiological inspection apparatus according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] [1. First embodiment] [1-1.Configuration] The configuration of a radiological inspection apparatus according to the first embodiment will be described below with reference to Fig. 1 and Fig. 2. The radiological inspection apparatus 100 irradiates an object W to be inspected with radiation and detects the radiation that has passed through the object W. Based on the detection result, the radiological inspection apparatus 100 generates a fluoroscopic image of the object W. Note that the radiological inspection apparatus 100 of this embodiment may be a CT apparatus, but in the following description it will be described as a radiological inspection apparatus that simply acquires fluoroscopic images.

[0014] 1, the radiological inspection apparatus 100 includes an inspection table 1 on which an object to be inspected W is placed, a radiation source 2 and a detector 3 that capture a fluoroscopic image of the object to be inspected W, and a filter adjustment unit 4 that is provided between the radiation source 2 and the detector 3 and adjusts a filter F that attenuates the radiation beam input from the radiation source 2 to the detector 3. The radiological inspection apparatus 100 further includes a control unit 9 that controls the operations of the inspection table 1, the radiation source 2, the detector 3, and the filter adjustment unit 4.

[0015] The inspection table 1 is a table having a mounting surface on which an object to be inspected W is placed. The inspection table 1 is equipped with a moving mechanism 11 that moves the mounting surface in a direction parallel to or perpendicular to the mounting surface, and a rotating mechanism 12 that rotates the mounting surface around an axis in the perpendicular direction. The moving mechanism 11 can be, for example, a ball screw mechanism driven by a servo motor. That is, the moving mechanism 11 moves the object to be inspected W in a direction parallel to or perpendicular to the mounting surface of the inspection table 1 by driving the servo motor. By moving the moving mechanism 11, the object to be inspected W can be aligned with the optical axis of the radiation beam.

[0016] The rotation mechanism 12 is provided below the movement mechanism 11 and is, for example, an actuator including a drive source such as a motor. The rotation mechanism 12 rotates the placement surface of the examination table 1 around an axis perpendicular to the placement surface. The rotation mechanism 12 may also be provided above the movement mechanism 11.

[0017] The radiation source 2 irradiates the inspection object W with a radiation beam. The radiation beam is a bundle of radiation rays that expands into a pyramidal shape with a focal point as the apex. The radiation source 2 is, for example, an X-ray tube, and the radiation is, for example, X-rays.

[0018] The detector 3 is disposed opposite the radiation source 2 across the examination table 1 and the object to be inspected W, and detects a two-dimensional distribution of radiation intensity attenuated according to the transmission path of the radiation, and outputs a fluoroscopic image to an image processing unit 93, which will be described later. The detector 3 is formed of, for example, a flat panel detector (FPD). The detector 3 also outputs a signal amount I0 of the radiation beam input thereto to a filter control unit 94, which will be described later.

[0019] The filter adjustment unit 4 holds a plurality of filters F, and inserts a filter F selected by a filter control unit 94 (described later) between the radiation source 2 and the detector 3. The filter adjustment unit 4 is provided, for example, on either the left or right side of the focal point of the radiation source 2 so that the inserted filter F is perpendicular to the optical axis of the radiation beam from the radiation source 2.

[0020] The filter F is a hard filter made of, for example, a metal. Suitable metals include copper, iron, aluminum, and alloys containing these. The filter F may be a plurality of filters made of the same material but having different thicknesses, or a plurality of filters made of different materials but having the same thickness. In the latter case, the thicknesses may be different as long as the attenuation rate of the radiation beam differs from filter to filter. In other words, it is sufficient that the attenuation rate of the radiation beam differs for each filter F. In the following explanation, the filter F will be described as a plurality of filters made of the same material but having different thicknesses.

[0021] 2, the control unit 9 includes a mechanism control unit 91 that controls the moving mechanism 11 and rotating mechanism 12 of the examination table 1, a radiation source control unit 92 that controls the radiation source 2, an image processing unit 93 that corrects the fluoroscopic image acquired from the detector 3, and a filter control unit 94 that causes the filter adjustment unit 4 to adjust the filter. The control unit 9 is composed of a computer and a driver circuit. The computer is composed of a storage device such as an HDD or SSD, a RAM, a CPU, etc. An input unit (not shown) is connected to the control unit 9, and a user controls each component of the radiological examination apparatus 100 via this input unit.

[0022] The mechanism control unit 91 controls the moving mechanism 11 and rotating mechanism 12 of the inspection table 1 to align the inspection object W placed on the inspection table 1 with the optical axis of the radiation beam and change the orientation of the inspection object W. The radiation source control unit 92 controls the radiation source 2 to irradiate the inspection object W with the radiation beam. That is, by controlling the mechanism control unit 91 and the radiation source control unit 92, the inspection object W is irradiated with the radiation beam, and a fluoroscopic image of the inspection object W can be acquired from the detector 3.

[0023] The image processing unit 93 includes an acquisition unit 931 that acquires various data such as offset data and gain data from the detector 3, and a correction unit 932 that corrects the fluoroscopic image based on the various data. The image processing unit 93 may display the fluoroscopic image corrected by the correction unit 932 on a display unit (not shown).

[0024] The filter control unit 94 includes a memory unit 941, a determination unit 942, and a selection unit 943. The memory unit 941 stores a predetermined signal amount Is in advance. The predetermined signal amount Is can be changed to a desired value via the input unit. The determination unit 942 refers to the memory unit 941 and compares the predetermined signal amount Is with the signal amount I0 of the radiation beam acquired from the detector 3. If I0>Is, the selection unit 943 causes the filter adjustment unit 4 to insert the filter F with the lowest attenuation rate among the filters F that have not been inserted between the radiation source 2 and the detector 3. Thereafter, the determination unit 942 compares Is with I0 attenuated by the filter F, and if I0≦Is, ends the adjustment of the filter F. On the other hand, if I0>Is again, the filter adjustment unit 4 controls the filter adjustment unit 4 to replace the filters F in order of decreasing attenuation rate until I0≦Is.

[0025] [1-2. Effect] The filter adjustment of this embodiment will be described with reference to Fig. 3. It is assumed that nothing is placed on the examination table 1 and that no filter F is inserted between the radiation source 2 and the detector 3.

[0026] First, under the control of the radiation source control unit 92, the radiation source 2 irradiates the detector 3 with a radiation beam. The detector 3 detects the signal amount I0 of the radiation beam input thereto and outputs it to the determination unit 942 of the filter control unit 94 (step S01). Next, the determination unit 942 refers to a predetermined signal amount Is stored in advance in the storage unit 941, and compares this predetermined signal amount Is with the signal amount I0 of the radiation beam acquired from the detector 3 (step S02).

[0027] If I0>Is (YES in step S02), the selector 943 causes the filter adjuster 4 to insert the filter F with the lowest attenuation rate among the filters F that have not been inserted between the radiation source 2 and the detector 3 so far (step S03). Thereafter, the process returns to step S01, and the detector 3 detects the signal amount I0 of the radiation beam attenuated through the filter F and outputs the signal amount I0 to the determiner 942. The determiner 942 again compares Is with I0, and if I0≦Is (NO in step S02), ends the adjustment of the filter F. On the other hand, if I0>Is again, the above-mentioned loop is repeated, and the selector 943 and the filter adjuster 4 sequentially replace the filters F in order of decreasing attenuation rate.

[0028] After the adjustment of the filter F is completed in this manner, the object W to be inspected is placed on the inspection table 1, and an image of the object W to be inspected is taken with the optimum filter F inserted.

[0029] [1-3.Effects] (1) In this embodiment, the determination unit 942 compares a predetermined signal amount Is with the signal amount I0 of the radiation beam acquired from the detector 3, and the filter adjustment unit 4 adjusts the filter F so that I0≦Is holds. This allows the user to acquire a fluoroscopic image with less noise while avoiding the need for complicated adjustments to the filter F. In particular, since there is no need to adjust the filter F even when the settings before imaging are frequently changed, the user can change the settings in various ways without being aware of the use of the filter F.

[0030] (2) In this embodiment, the filter adjuster 4 sequentially replaces the filters F in ascending order of attenuation rate. This not only reduces noise in the fluoroscopic image, but also prevents a decrease in the S / N ratio due to an excessive decrease in the signal amount I0. In other words, the user can acquire high-quality fluoroscopic images that achieve both noise reduction and a maintained S / N ratio.

[0031] [2. Second Embodiment] [2-1.Configuration] The configuration of the radiological inspection apparatus 100 of this embodiment will be described with reference to Figures 4 and 5. The second embodiment has the same basic configuration as the first embodiment. Only the differences from the first embodiment will be described below, and the same parts as in the first embodiment will be assigned the same reference numerals and detailed description will be omitted.

[0032] In this embodiment, the ideal thickness of the filter F is calculated based on the filter thickness curve. Therefore, the filter F in this embodiment is limited to a plurality of filters made of the same material but having different thicknesses.

[0033] 4, the filter control unit 94 of this embodiment includes a calculation unit 944 instead of the determination unit 942. Furthermore, the storage unit 941 stores a formula for calculating an ideal filter thickness in advance, in addition to a predetermined signal amount Is.

[0034] This mathematical formula is preferably an approximation of a filter thickness curve as shown in Fig. 5. The filter thickness curve indicates the relationship between the filter thickness X and the signal amount I0 of the radiation beam input to the detector 3. The filter thickness curve is difficult to express as a theoretical formula due to the influence of the energy spectrum of the radiation source 2, the energy sensitivity of the detector 3, the positional relationship of each component, etc., and therefore is obtained for each setting before imaging by using actual measurements or Monte Carlo simulation. The approximation formula indicating this filter thickness curve is a mathematical formula that is stored in advance in the storage unit 941.

[0035] This formula is shown, for example, by the following formula: Note that this formula can be changed to a desired one via the input unit described above.

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[0036] The calculation unit 944 refers to the storage unit 941 and calculates the ideal filter thickness Xs by substituting the predetermined signal amount Is and the radiation beam signal amount I0 acquired from the detector 3 into this formula. In other words, the calculation unit 944 calculates the ideal filter thickness Xs as a function of the radiation beam signal amount I0.

[0037] The selection unit 943 selects the filter F having the thickness closest to the ideal filter thickness Xs calculated by the calculation unit 944, and causes the filter adjustment unit 4 to insert the filter F.

[0038] [2-2. Effect] The filter adjustment of this embodiment will be described with reference to Fig. 6. It is assumed that nothing is placed on the examination table 1 and that no filter F is inserted between the radiation source 2 and the detector 3.

[0039] First, under the control of the radiation source controller 92, the radiation source 2 irradiates the detector 3 with a radiation beam. The detector 3 detects the signal amount I0 of the radiation beam input thereto and outputs it to the calculator 944 of the filter controller 94 (step S11). Next, the calculator 944 refers to the storage unit 941 and substitutes the predetermined signal amount Is and the signal amount I0 of the radiation beam acquired from the detector 3 into the above-mentioned formula to calculate the ideal filter thickness Xs (step S12). The selector 943 selects a filter F having a thickness closest to the ideal filter thickness Xs calculated by the calculator 944, and causes the filter adjuster 4 to insert the filter F (step S03).

[0040] After the adjustment of the filter F is completed in this manner, the object W to be inspected is placed on the inspection table 1, and an image of the object W to be inspected is taken with the optimum filter F inserted.

[0041] [2-3. Effects] (1) In this embodiment, the calculation unit 944 calculates the ideal filter thickness Xs as a function of the signal intensity I0 of the radiation beam, and the filter adjustment unit 4 adjusts the filter F based on this filter thickness Xs. This not only achieves the effects of the first embodiment, but also eliminates the need for trial and error to select the optimal filter F as in the first embodiment, thereby shortening the adjustment time.

[0042] (2) The calculation unit 944 of this embodiment calculates the ideal filter thickness Xs based on the filter thickness curve of the filter F. As a result, the more filters F are used, the more ideal the thickness of the filters F can be used. In the first embodiment, increasing the number of filters F has the disadvantage of increasing the time required to adjust the filters F, but this embodiment can eliminate this disadvantage.

[0043] 3. Other Embodiments Although multiple embodiments of the present invention have been described herein, these embodiments are presented as examples and are not intended to limit the scope of the invention. The above-described embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. These embodiments and their modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims.

[0044] (1) In the first embodiment, the filter F with the lowest attenuation rate is inserted first, but this is not limiting. For example, if the S / N ratio is not a major concern, the filter F with a medium attenuation rate may be inserted first. This reduces the number of loops in the adjustment flow for filter F, thereby shortening the adjustment time.

[0045] (2) In the first embodiment, the filters F are replaced one after another. However, an additional filter F may be inserted while a previously inserted filter F remains in place. In this case, it is preferable that the thickness and material of the multiple filters F are the same.

[0046] (3) In the second embodiment, the selector 943 selects the filter F having the thickness closest to the ideal filter thickness Xs calculated by the calculator 944. However, the selector 943 may select a filter F having a thickness equal to or greater than Xs and closest to Xs. This makes it possible to reliably reduce noise in the perspective images.

[0047] (4) In the above embodiment, the filter adjustment unit 4 adjusted the filter F based on the selection by the selection unit 943. However, this is not limited to this. For example, a notification unit (not shown) may notify the user of the filter F selected by the selection unit 943, encouraging the user to insert the filter F. [Explanation of symbols]

[0048] 100...Radiation inspection device 1...Examination table 11...Movement mechanism 12...Rotation mechanism 2…Radiation source 3...Detector 4...Filter adjustment section 9...Control unit 91...Mechanism control unit 92...Radiation source control unit 93...Image processing unit 931…Acquisition Department 932...Correction unit 94...Filter control section 941...Storage section 942...Judgment section 943...Selection section 944...Calculation section F...Filter W: Inspection object

Claims

1. a radiation source for emitting a radiation beam; a detector disposed opposite the radiation source and into which the radiation beam is input; a filter adjustment unit that adjusts an attenuation rate of a filter provided between the radiation source and the detector in order to attenuate a signal amount of the radiation beam input to the detector; a calculation unit for calculating a thickness of the filter as a function of a signal amount of the radiation beam; Equipped with The filter adjustment unit adjusts an attenuation rate of the filter based on the thickness of the filter calculated by the calculation unit. Radiation inspection equipment.

2. the calculation unit calculates the thickness of the filter based on a filter thickness curve indicating a relationship between the thickness of the filter and a signal amount of the radiation beam; The radiological inspection apparatus according to claim 1 .

3. The filter thickness curve is represented by the following formula: The radiological inspection apparatus according to claim 2 . [0010] Xs: filter thickness μ: Linear attenuation coefficient Is: Predetermined signal amount I0: Signal amount of the radiation beam

Images