Computed tomography device

Abstract

The present invention provides a computed tomography apparatus which can select an optimal imaging condition regardless of the experience of a user, thereby improving workability. A computed tomography device (100) is provided with: a storage unit (73) for storing a plurality of imaging times required for imaging and imaging conditions preset in accordance with the imaging times when imaging an image of a subject (A) by irradiating the subject (A) with radiation; a display unit (5) that displays a plurality of imaging times; an input unit (6) that receives, from a user, a selection of the imaging time displayed on the display unit (5); and an imaging condition determination unit (74) that determines, as an imaging condition at the time of imaging, an imaging condition corresponding to the imaging time received by the input unit (6).

Description

Technical Field

[0001] An embodiment of the present invention relates to a computer tomography apparatus. Background Art

[0002] Industrial computed tomography (CT) devices that inspect small electronic parts such as lithium-ion batteries with high resolution are widely used. In the CT device, a radiation source that irradiates radiation, such as an X-ray beam, and a detector that detects the X-ray beam of the radiation source with two-dimensional resolution are arranged opposite to each other. A rotatable inspection table is provided between the radiation source and the detector. While the X-ray beam is irradiated to the object to be inspected placed on the inspection table, the inspection table rotates once, thereby irradiating the X-ray beam to the object to be inspected in all directions.

[0003] In order to use a CT device for imaging, various imaging conditions need to be set. The various imaging conditions include tube current, tube voltage, material or thickness of metal filter, exposure time, number of views, pixel combination (binning), number of accumulated images, dose, etc. There are many setting items. In order to obtain the best image, these various imaging conditions need to be set appropriately.

[0004] [Prior art literature]

[0005] [Patent Document]

[0006] [Patent Document 1] Japanese Patent No. 6519663 Summary of the invention

[0007] [Problems to be solved by the invention]

[0008] However, as described above, since there are many setting items, it is difficult for inexperienced users to set appropriate conditions, and it is a laborious task even for experienced users. Therefore, a technology has been developed in which icons of parameters of shooting conditions are arranged in a matrix on a display screen according to two-dimensional indicators related to image quality, and the user selects from the displayed icons to determine the shooting conditions (Patent Document 1).

[0009] In the case of Patent Document 1, the difficulty of setting the imaging conditions is indeed alleviated to a certain extent. However, without knowledge related to CT imaging such as concentration resolution or resolution, selection cannot be made. The situation that inexperienced users find it difficult to select appropriate icons will not change. Also, even experienced users have to select icons after considering concentration resolution or resolution, so the laborious work will not change.

[0010] An embodiment of the present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide a CT apparatus that can select the optimal imaging condition regardless of the user's experience, thereby improving operability.

[0011] [Technical means to solve the problem]

[0012] A computer tomography apparatus in an embodiment of the present invention includes: a storage unit, which stores a plurality of shooting times required for shooting and shooting conditions pre-set corresponding to each shooting time when irradiating a test object with radiation to shoot an image of the test object; a display unit, which displays the plurality of shooting times; an input unit, which receives a selection of the shooting time displayed on the display unit from a user; and a shooting condition determination unit, which determines the shooting condition corresponding to the shooting time received by the input unit as the shooting condition for shooting, wherein the shooting condition is set so that at any of the shooting times, the value of the radiation dose detected by the detector is the same or within a certain range. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a side view schematically showing the CT apparatus according to the first embodiment.

[0014] Figure 2 It is a schematic diagram showing a state where the display unit displays the shooting time.

[0015] Figure 3 It is a block diagram showing the structure of the control unit.

[0016] Figure 4 This is a table showing an example of shooting conditions corresponding to shooting time.

[0017] Figure 5 This is a table showing an example of shooting conditions corresponding to shooting times in Modification 1.

[0018] Figure 6 This is a table showing an example of shooting conditions corresponding to shooting times in Modification 2.

[0019] Figure 7 This is a schematic diagram showing a method of calculating the dose when a metal filter unit is used.

[0020] Figure 8 This is a table showing an example of shooting conditions corresponding to shooting times in Modification 3.

[0021] Fig. 9 (a) and Fig. 9 (b) is a diagram showing a display state of shooting conditions on a display unit, Fig. 9 (a) indicates the standard mode, Fig. 9(b) indicates professional mode.

[0022] Fig.10 This is a table showing an example of the imaging conditions corresponding to the imaging time according to the second embodiment.

[0023] Fig.11 It is a block diagram showing the configuration of a control unit in the third embodiment.

[0024] Fig.12 It is a diagram showing an example of the shooting conditions in each preset table.

[0025] Fig.13 This is a diagram showing an example of shooting conditions for each preset table according to Modification 6.

[0026] Fig.14 This is a diagram for illustrating an example of switching of the imaging mode in the fourth embodiment.

[0027] [Explanation of Symbols]

[0028] 100: CT device

[0029] 1: Inspection table

[0030] 11: XY mechanism

[0031] 12: Rotating table

[0032] 13: Lifting mechanism

[0033] 2: Radiation source

[0034] 3: Detector

[0035] 4: Metal filter unit

[0036] 5: Display unit

[0037] 6: Input section

[0038] 7: Control Department

[0039] 71: Inspection table control department

[0040] 72: Radiation source control department

[0041] 73: Storage

[0042] 74: Shooting condition determination unit

[0043] 75: Movement amount calculation unit

[0044] 76: Geometric ratio calculation unit

[0045] 77: Table selection section

[0046] A: Object to be inspected DETAILED DESCRIPTION

[0047] (First Embodiment)

[0048] Hereinafter, the CT apparatus according to the first embodiment will be described in detail with reference to the drawings. Figure 1 It is a side view schematically showing the CT apparatus according to the first embodiment.

[0049] The CT device 100 is a device for performing nondestructive inspection on an object A. The CT device 100 irradiates the periphery of the object A with a radiation beam that passes through the object A, and detects the radiation dose that is weakened by passing through the object A. Then, a cross-sectional image, i.e., a CT image, of the object A is generated based on the detection result. In addition, the CT device 100 generates a three-dimensional (3D) image based on the generated multiple CT images.

[0050] like Figure 1 As shown, the CT device 100 includes: an inspection table 1, a radiation source 2, a detector 3, a metal filter unit 4, a display unit 5, an input unit 6, and a control unit 7. The inspection table 1 is a table having a placement surface for placing the inspection object A. The inspection table 1 can move in a direction parallel to the placement surface or in a direction orthogonal to the placement surface. In addition, the inspection table 1 can rotate about a direction perpendicular to the placement surface. The inspection table 1 has an XY mechanism, a rotating table 12, and a lifting mechanism 13.

[0051] The XY mechanism 11 places the inspection object A. For example, a ball screw mechanism driven by a servo motor may be used for the XY mechanism 11. The XY mechanism 11 is movable in a direction parallel to the optical axis of the radiation beam and in a direction parallel to the placement surface and in a direction orthogonal to the optical axis of the radiation beam.

[0052] The rotating table 12 is provided below the XY mechanism. The rotating table 12 includes an actuator including a driving source such as a motor, and is provided to be rotatable about a direction perpendicular to the mounting surface. During the radiation beam irradiation, the rotating table 12 rotates, thereby irradiating the inspection object A in all directions with the radiation beam.

[0053] The lifting mechanism 13 is provided below the rotating table 12. The lifting mechanism 13 may use a ball screw mechanism driven by a servo motor. The lifting mechanism 13 can move in a direction perpendicular to the loading surface. That is, by moving the lifting mechanism 13 in a direction perpendicular to the loading surface, the height of the inspection object A can be adjusted.

[0054] The radiation source 2 irradiates, for example, a radiation beam that passes through the inspection object A. The radiation beam is a beam of radiation that has a fan angle and a cone angle and spreads in a conical shape with the focus of the radiation source as the vertex. In the present embodiment, the radiation source 2 is, for example, a reflective or transmissive microfocus X-ray tube or a nanofocus X-ray tube, and the radiation beam is an X-ray beam. In addition, the radiation beam is not limited to an X-ray beam, and any beam that passes through the inspection object A, such as a gamma ray, can be used.

[0055] The detector 3 is arranged opposite to the radiation source 2 across the inspection table 1 and the object A to be inspected. The detector 3 is arranged so that the center of the imaging area coincides with the optical axis of the radiation source 2. The detector 3 detects the two-dimensional distribution of the radiation intensity that is weakened corresponding to the transmission path of the radiation beam, and outputs a perspective image. The detector 3 includes, for example, a flat panel display (Flat Panel Display, FPD). The detector 3 has a moving mechanism for adjusting the distance from the object A to be inspected. The detector 3 can be moved in a direction orthogonal to the imaging area (a direction parallel to the optical axis of the radiation source 2) by the moving mechanism. In addition, in order to align the optical axis of the radiation source with the center of the imaging area, the detector 3 can also be moved in a direction parallel to the imaging area by the moving mechanism.

[0056] The metal filter unit 4 is arranged between the object to be inspected A and the radiation source 2 and at a position close to the radiation source 2. The metal filter unit 4 is a thin plate-shaped member with a thickness of about several mm. The metal filter unit 4 is a metal plate containing copper, aluminum, iron, etc. or an alloy thereof. A plurality of metal filter units 4 are provided, and the raw materials or thicknesses of each metal filter unit 4 are different.

[0057] The metal filter unit 4 is arranged to be movable by a moving mechanism (not shown). The moving mechanism may use a ball screw mechanism driven by a servo motor, for example. The moving mechanism moves the metal filter unit 4 corresponding to the raw material and thickness and the shooting time selected by the user on the optical axis of the radiation source 2. The radiation beam is irradiated to the metal filter unit 4 arranged on the optical axis, and the radiation beam passing through the metal filter unit 4 is irradiated to the inspection object A. By passing through the metal filter unit 4, the generation of metal artifacts is suppressed.

[0058] The display unit 5 is, for example, a monitor such as a liquid crystal display or an organic electroluminescence (EL) display. The display unit 5 displays various images, such as fluoroscopic images, CT images, and 3D images of the inspection object A, an imaging area, and imaging conditions. In addition, the display unit 5 may also display the imaging conditions determined by the control unit 7 to be optimal.

[0059] The display unit 5 displays a plurality of shooting times for which various shooting conditions described later are set in advance. The shooting time is the time required for actual shooting. Figure 2 2 is a schematic diagram showing a state where the display unit 5 displays the shooting time. Figure 2 As shown, the display unit 5 displays icons of shooting time. The display unit 5 displays four shooting times, for example, 1min, 4min, 7min, and 25min. The display unit 5 displays icons of shooting time in order from short to long shooting time. In addition, Figure 2 The shooting time is an example. For example, you can set the shooting time to 10 minutes, 15 minutes, etc., and the number of shooting times can also be set to more than four. In addition, Figure 2 The “Beautiful” display shown indicates that a more beautiful and clear image can be obtained as the shooting time is longer.

[0060] The input unit 6 may be a keyboard, a mouse, a touch panel, etc. The input unit 6 receives the shooting time displayed on the display unit 5 from the user. In addition, the input unit 6 may receive various operations such as menu selection for formal shooting or trial shooting, setting of shooting conditions, manual operation of the moving mechanism, start of shooting, selection of a part of the inspection object A to be observed, etc.

[0061] The control unit 7 includes a computer and a drive circuit. The computer includes a memory such as a hard disk drive (HDD) or a solid state drive (SSD), a random access memory (RAM), a central processing unit (CPU), etc. The control unit 7 is connected to the input unit 6, and the user controls the control unit 7 to control each structure of the CT device 100 via the input unit 6.

[0062] Figure 3 7 is a block diagram showing the structure of the control unit 7. Figure 3 As shown, the control unit 7 includes a table control unit 71 , a radiation source control unit 72 , a storage unit 73 , and an imaging condition determination unit 74 .

[0063] The inspection table control unit 71 controls the XY mechanism 11, the rotating table 12, and the lifting mechanism 13. Through the control of the inspection table control unit 71, the inspection object A placed on the inspection table 1 can be aligned with the optical axis of the radiation beam or the inspection object A can be rotated once during the irradiation of the radiation beam. In addition, through the control of the inspection table control unit 71, the distance (Focus Center Distance (FCD)) between the radiation source 2 and the inspection object A is adjusted.

[0064] The radiation source control unit 72 controls the radiation source 2 to irradiate the inspection object A with radiation beams. That is, the inspection object A is irradiated with radiation beams in all directions under the control of the inspection table control unit 71 and the radiation source control unit 72 , and the detector 3 acquires a fluoroscopic image.

[0065] The storage unit 73 stores a plurality of preset shooting times and also stores the best shooting conditions corresponding to each shooting time. Figure 4 is a table showing an example of shooting conditions corresponding to shooting time. Figure 4 As shown in FIG. 1 , the imaging conditions such as the tube voltage, tube current, material and thickness of the metal filter unit 4, pixel combination, exposure time, number of views, cumulative number of images, and dose are set corresponding to each imaging time. Figure 4 Taking the example of , when the shooting time is 1 minute, in the storage unit 73, the tube voltage is stored as 200 kV, the tube current is stored as 100 mA, the metal filter unit 4 is stored as the raw material is copper and the thickness is 1 mm, the pixel combination is stored as 1, the exposure time is stored as 100 ms, the number of views is stored as 600, the cumulative number of frames is stored as 1, and the dose is stored as 10000.

[0066] Here, the dose refers to the amount of radiation signal detected by the detector 3. The dose at each imaging time is preset to be the same or within a certain range. Figure 4 In the example of FIG. 1 , the dose at each imaging time of 1 minute, 4 minutes, 7 minutes, and 25 minutes is 10,000 and is the same.

[0067] The dose was calculated by the following formula (1).

[0068] Dose = tube current × pixel combination 2 × exposure time × cumulative number of images···(1)

[0069] Alternatively, the actual measured value may be obtained by measuring without placing the inspection object A on the inspection table 1 .

[0070] In addition, in the present embodiment, the dose is set to be the same, but the dose at each imaging time may be set to be within a certain range. The so-called certain range is determined by the specifications of the CT device 100 or the arrangement relationship of the object to be inspected. For example, a limit value in the specifications of the CT device 100 is set, and a range of plus or minus 10% of the limit value is set as a certain range.

[0071] The shooting condition determination unit 74 determines the shooting condition. That is, the shooting condition corresponding to the shooting time selected by the user is determined as the shooting condition for actual shooting. After the shooting condition determination unit 74 determines the shooting condition, shooting starts.

[0072] As described above, the storage unit 73 of the CT device 100 of this embodiment stores a plurality of imaging times that are preliminarily associated with the optimal imaging conditions. Then, the user can simply select the imaging time displayed on the display unit 5. Thus, there is no need to set detailed imaging conditions. Therefore, even an inexperienced user can perform optimal imaging. In addition, for an experienced user, time-consuming operations can be omitted, thereby improving operability.

[0073] In addition, in this embodiment, the dose is the same at each shooting time. By setting the dose to be the same, the signal-to-noise (SN) ratio of the image becomes constant. By setting the SN ratio under each shooting condition to be constant, the increase in shooting time only contributes to the resolution of the image. By simply selecting that longer shooting time = higher resolution, the best shooting conditions for obtaining beautiful images can be set.

[0074] (Variant 1)

[0075] Next, the CT apparatus 100 of the modification example 1 is described. In addition, the same symbols are given to the same structures and functions as those in the first embodiment, and detailed descriptions are omitted. In the first embodiment, the pixel combination at each imaging time is the same, and in the modification example 1, the pixel combination is changed according to the different imaging times.

[0076] Figure 5 This is a table showing an example of shooting conditions corresponding to shooting times in Modification 1. Figure 5 The following examples show shooting times of 1 minute, 2 minutes, 12 minutes, and 16 minutes. Figure 5 As shown, the pixel combination is 2 when the shooting time is 1 minute and 2 minutes, and the pixel combination is 1 when the shooting time is 12 minutes and 16 minutes.

[0077] When the pixel combination is changed, the dose is different if it is based on the above formula (1). Therefore, in this variation 1, the dose is set to be the same by further adjusting the exposure time. The so-called exposure time is the time required to capture one frame, sometimes also called the integration time. Figure 5 As shown, the exposure time is 100 ms when the shooting time is 1 min and 2 min, and the exposure time is 200 ms when the shooting time is 12 min and 16 min.

[0078] As described above, in the CT device 100 of variant example 1, the pixel combination is changed in at least a part of each shooting time, and the exposure time is used for adjustment so that the dose at each shooting time becomes constant. As shown in the formula (1), in the calculation of the dose, the pixel combination is squared. Therefore, when the dose is set to the same, if the value of the pixel combination is increased, the value of the exposure time or the cumulative number of images becomes smaller. Moreover, the shooting time is determined by "exposure time × number of views × cumulative number of images". Therefore, if the value of the pixel combination is increased, the shooting time can be shortened. Since the pixel combination is related to the resolution of the detector, by changing the pixel combination, the best shooting conditions for obtaining beautiful images can be set at each shooting time.

[0079] In addition, in Modification 1, the exposure time is used for adjustment so that the dose at each shooting time is the same even if the pixel combination is changed. Thus, the shooting time or dose can be adjusted without changing the properties of X-rays such as transmittance or spectrum. Therefore, the contrast at each shooting time becomes constant.

[0080] (Variant 2)

[0081] Next, the CT apparatus 100 of the modification 2 is described. In addition, the same reference numerals are given to the same structures and functions as those of the first embodiment, and detailed descriptions thereof are omitted. In the modification 1, the exposure time is used for adjustment so that the dose at each imaging time is the same even if the pixel combination is changed, but in the modification 2, the metal filter unit 4 is used for adjustment.

[0082] Figure 6 is a table showing an example of shooting conditions corresponding to shooting time in Modification Example 2. Figure 6 1, 2, and 3 minutes are shown in the example. In the second variation, the raw material of the metal filter unit 4 is copper and the same, but the thickness is different according to the different shooting times. Figure 6 As shown, when the shooting time is 1 minute, the thickness is 2 mm, when the shooting time is 2 minutes, the thickness is 1 mm, and when the shooting time is 3 minutes, the thickness is 0.2 mm. In addition, when the shooting time is 1 minute, the pixel combination is 3, when the shooting time is 2 minutes, the pixel combination is 2, and when the shooting time is 3 minutes, the pixel combination is 1.

[0083] The material or thickness of the metal filter 4 is adjusted so that the dose at each imaging time is the same or within a certain range even when the pixel combination is different. The dose can be calculated using the measured value or, for example, by the following formula (2) and formula (3).

[0084] Figure 7This is a schematic diagram showing a method of calculating the dose when the metal filter unit 4 is used. The dose when the metal filter unit 4 is used is calculated by the following formula (2).

[0085]

[0086] I(E, x): The intensity of the attenuated X-ray of energy E (the intensity after passing through the metal filter unit 4)

[0087] I 0 (E): Initial intensity of energy E (intensity irradiated from radiation source 2)

[0088] μ(E): Radiation attenuation coefficient of energy E in the material of the metal filter unit 4

[0089] x: distance that X-rays pass through the substance (thickness of the metal filter unit 4)

[0090] e:Napier's constant

[0091] Alternatively, the dose can also be calculated using the following formula (3).

[0092]

[0093] A: Detector area

[0094] t: exposure time

[0095] μ filer : Radiation attenuation coefficient of the metal filter unit 4

[0096] The dose may be calculated using equations other than the above equations (2) and (3). For example, the dose may be calculated by adding a combination term in consideration of scattered rays, by considering a conical beam, or by using Monte Carlo simulation.

[0097] When the user selects an imaging time via the input unit 6 , the type of the metal filter unit 4 is determined. The metal filter unit 4 is moved by the moving mechanism so that the metal filter unit 4 corresponding to the selected imaging time is arranged on the optical axis of the radiation source 2 .

[0098] As described above, in the CT apparatus 100 of the second modification, the imaging conditions are stored in correspondence with each imaging time in such a manner that the types of the metal filter units 4 at each imaging time are different and the doses are the same or within a certain range. Thus, the metal filter unit 4 that is optimal for the radiation irradiated from the radiation source 2 can be set, thereby effectively reducing metal artifacts.

[0099] In addition, the determined metal filter unit 4 may not be automatically arranged by the moving mechanism. For example, the display unit 5 may display the material and thickness of the metal filter unit 4, and when each metal filter unit 4 is marked with a number, the number and the like may be displayed, and the user may arrange the metal filter unit 4. In this case, since it is not necessary to arrange a plurality of metal filter units 4 or a moving mechanism in the CT apparatus 100, the CT apparatus 100 can be simplified and miniaturized.

[0100] (Variant 3)

[0101] Next, the CT apparatus 100 of the modification 3 is described. In addition, the same reference numerals are given to the same structures and functions as those of the first embodiment, and detailed descriptions thereof are omitted. In the modification 1, the exposure time is adjusted according to the different shooting times, but in the modification 3, the accumulated number of images is changed.

[0102] Figure 8 is a table showing an example of shooting conditions corresponding to shooting time in Modification 3. Figure 8 The examples in FIG. 1 show shooting times of 1 minute, 4 minutes, 27 minutes, and 36 minutes. Figure 8 As shown, the cumulative number of pictures when the shooting time is 1 minute and 4 minutes is 1, and the cumulative number of pictures when the shooting time is 27 minutes and 36 minutes is 3. In addition, the pixel combination is 3 when the shooting time is 1 minute and 4 minutes, and the pixel combination is 1 when the shooting time is 27 minutes and 36 minutes.

[0103] As described above, in the CT apparatus 100 of the third modification, the pixel combination is changed in at least a part of each imaging time, and the dose is adjusted by the accumulated number of images so that the dose is the same or within a certain range. Thus, the imaging time or dose can be adjusted without changing the properties of X-rays such as transmittance or spectrum. In addition, when the exposure time is used for adjustment, there will be restrictions due to the specifications of the CT apparatus 100, but when the accumulated number of images is used for adjustment, there is no such restriction, so the degree of freedom in setting the imaging conditions at each imaging time is improved.

[0104] (Variant 4)

[0105] Next, the CT apparatus 100 of the modification example 4 is described. In addition, the same symbols are attached to the same structures and functions as those in the first embodiment, and detailed descriptions are omitted. In the first embodiment, imaging is started under imaging conditions corresponding to the imaging time selected by the user, but in the modification example 4, there is a function of correcting the imaging time corresponding to the imaging time.

[0106] For example, a user from Figure 4 Select 7min from the 4 shooting times shown. Fig. 9 As shown in (a) of FIG. 1 , the display unit 5 displays the shooting conditions corresponding to the selected shooting time of 7 minutes. The user can change the shooting mode on the display screen.

[0107] When the user changes the shooting mode from Standard to Professional, such as Fig. 9 As shown in (b), the shooting mode is changed to the professional mode, and each shooting condition can be modified. When the user modifies each shooting condition to a more appropriate condition and presses the determination button, the shooting condition is changed to the modified condition, and shooting starts based on the modified shooting condition.

[0108] In this way, the CT apparatus 100 of the fourth modification can correct the preset imaging conditions. Thus, it is possible to make a fine correction according to the imaging purpose, etc., so that imaging can be performed under more optimal imaging conditions. Therefore, more optimal images can be obtained.

[0109] (Second Embodiment)

[0110] Next, the CT apparatus 100 of the second embodiment is described. In addition, the same symbols are marked for the same structure and the same function as the first embodiment, and detailed description is omitted. In the first embodiment, the imaging conditions are set in such a way that the dose is the same or within a certain range at each imaging time. In the second embodiment, on this basis, the imaging conditions are set in such a way that the resolution when the imaging time is long is equal to or increased from the resolution when the imaging time is short. In addition, the so-called resolution is the resolution of the detector.

[0111] Fig.10 is a table showing an example of shooting conditions corresponding to shooting times in the second embodiment. Fig.10 In the example of FIG. 1 , six imaging times are shown, namely, 1 min, 2 min, 4.5 min, 9 min, 27 min, and 36 min. The dose at each imaging time is 90,000 and is the same.

[0112] Furthermore, the shooting conditions are set in such a way that the resolution of the case where the shooting time is long is equal to or increased from the resolution of the case where the shooting time is short. In other words, the resolution of the case where the shooting time is short is not higher than the resolution of the case where the shooting time is long. That is, if the shooting time is 1 minute and the shooting time is 2 minutes, the resolution is the same. On the other hand, if the shooting time is 1 minute and the shooting time is 4.5 minutes, or the shooting time is 2 minutes and the shooting time is 4.5 minutes, the resolution is higher when the shooting time is 4.5 minutes.

[0113] Also, because resolution is tied to pixel binning, adjusting the resolution also adjusts the pixel binning values. Fig.10 In the example, adjustment is performed as follows: the number of pixel combinations is 3 when the resolution is 500×500, whereas the number of pixel combinations is 2 when the resolution is 1500×1500.

[0114] Thus, in the CT apparatus 100 of this embodiment, the dose is the same at each imaging time, and the resolution in the case of a long imaging time is equal to or higher than that in the case of a short imaging time. Therefore, a beautiful image can be obtained in the case of a long imaging time.

[0115] (Variant 5)

[0116] The CT apparatus 100 of the fifth modification is described. In addition, the same symbols are given to the same structures and functions as those in the second embodiment, and detailed descriptions are omitted. In the second embodiment, the imaging conditions are set in such a way that the resolution increases step by step as the set imaging time becomes longer. In the fifth modification, the imaging conditions are set in such a way that the number of views is equal to or increased instead of the resolution. The so-called number of views refers to the number of data collection directions per week.

[0117] For example, Figure 5 As shown, the number of views when the shooting time is 1 minute is set to 600, the number of views when the shooting time is 2 minutes is set to 1200, the number of views when the shooting time is 12 minutes is set to 1800, and the number of views when the shooting time is 16 minutes is set to 2400. As the shooting time becomes longer, the number of views increases.

[0118] Thus, when the number of views under the set shooting time is compared, the number of views in the case of long shooting time is equal to or more than the number of views in the case of short shooting time, and the number of views increases stepwise as the shooting time becomes longer. With respect to the same dose, the more the number of views increases, the more the clarity of the image increases. Therefore, the clarity of the image can be improved as the shooting time becomes longer.

[0119] (Third Embodiment)

[0120] A CT apparatus 100 according to a third embodiment will be described. The same reference numerals are used for the same configurations and functions as those in the first embodiment, and detailed descriptions thereof will be omitted. In the third embodiment, an imaging time and imaging conditions are set according to a geometric magnification.

[0121] Fig.11 1 is a block diagram showing the structure of the control unit 7 in the third embodiment. In the third embodiment, the control unit 7 further includes a movement amount calculation unit 75, a geometric magnification calculation unit 76, and a table selection unit 77. The movement amount calculation unit 75 calculates the movement amount of the object A or the detector 3 caused by the user via the input unit 6.

[0122] The geometrical magnification calculation unit 76 calculates the distance (FCD) from the focus of the radiation source 2 to the inspection object A and the distance (focus to detector distance, FDD) from the focus of the radiation source 2 to the detector 3, taking into account the movement amount calculated by the movement amount calculation unit 75. Then, the geometrical magnification calculation unit 76 calculates the geometrical magnification (FCD / FDD) based on the calculated FCD and FDD.

[0123] The table selection unit 77 selects a preset table corresponding to the geometric magnification. Fig.12 7 is a diagram showing the contents of each preset table. The storage unit 73 stores a plurality of preset tables as optimal shooting conditions corresponding to the geometric magnification. The preset table is a group of a plurality of shooting times and shooting conditions set corresponding to each shooting time. The preset table is changed according to the geometric magnification.

[0124] For example, Fig.12 As shown, preset table (1) and preset table (2) are set. Moreover, the value of a as a threshold is stored in the storage unit 73. The table selection unit 77 selects the preset table (1) when the geometric magnification calculated by the geometric magnification calculation unit is less than a. On the other hand, the table selection unit 77 selects the preset table (2) when the geometric magnification calculated by the geometric magnification calculation unit is greater than a. In the present embodiment, the preset table (2) is selected.

[0125] The display unit 5 displays the shooting time set in the preset table (2), and the user selects the desired shooting time from the displayed shooting time. As the shooting condition, since the preset table (2) is selected, the metal filter unit 4 is 0 mm, that is, the shooting is performed without the metal filter unit 4. In addition, the tube voltage is not 200 kV. If the user selects 2 minutes, 101 kV is used as the shooting condition.

[0126] In this way, the storage unit 73 stores a plurality of preset tables corresponding to geometric magnifications, and the user selects a shooting time corresponding to the geometric magnification. Therefore, shooting corresponding to the geometric magnification can be performed, and even an inexperienced user can obtain a clearer image.

[0127] In addition, the preset tables do not need to be two, and more than two may be provided to further classify the range of geometric magnification. In this case, the number of the first threshold, the second threshold, and the threshold indicating the boundary of each preset table can be increased. Thus, a clearer image can be obtained.

[0128] (Variant 6)

[0129] Next, the CT apparatus 100 of the modification example 6 is described. In addition, the same symbols are given to the same structures and functions as those in the third embodiment, and detailed descriptions are omitted. In the CT apparatus 100 of the modification example 6, as in the third embodiment, a plurality of preset tables are stored, and the table selection unit 77 selects the corresponding preset table according to the geometric magnification, and the above aspects are the same.

[0130] However, in the modification 6, the dose is set to be the same or within a certain range under any imaging condition. The dose is set to be the same or within a certain range by adjusting any one or all of the tube current, exposure time, cumulative number of images, and metal filter unit 4. That is, even if the preset tables are different, the dose under each imaging condition is the same or within a certain range.

[0131] Fig.13 is a diagram showing the shooting conditions of each preset table of Modification Example 6. Fig.13 As shown in FIG. 1 , in each preset table, the tube current and exposure time conditions are different, but the dose is 40,000 and the same. Fig.13 In the example of FIG. 1 , the tube current and the exposure time are adjusted in the same manner as the dose, but the metal filter unit 4 or the accumulated number of images may be adjusted.

[0132] Thus, in Modification 6, under any of the shooting conditions in the preset table, the dose is set to be the same or within a certain range by adjusting any one or all of the tube current, exposure time, cumulative number of images, and metal filter unit 4. Thus, regardless of the geometric magnification, the best metal filter unit 4 can be set for a constant SN ratio or a reduction in metal artifacts, so that the image quality improves as the shooting time increases.

[0133] (Fourth Embodiment)

[0134] A CT apparatus 100 according to a fourth embodiment is described. In addition, the same reference numerals are given to the same structures and functions as those in the third embodiment, and detailed descriptions thereof are omitted. The CT apparatus 100 according to the fourth embodiment is configured such that a user selects an imaging mode according to the type of the object A to be inspected or the purpose of imaging, etc., based on the structure of the third embodiment.

[0135] The storage unit 73 stores a plurality of shooting modes. For example, in addition to the standard mode, the storage unit 73 also stores shooting modes according to the type of the inspected object A and the purpose of shooting. The types of the inspected object A include materials such as plastic, weight, thickness, etc. The storage unit 73 stores the shooting time and the shooting time in correspondence with each item. The purpose of shooting includes internal observation, appearance observation, size measurement, or image clarity for each purpose, etc. The storage unit 73 stores the shooting time and the shooting time in correspondence with each item. In each shooting mode, shooting conditions suitable for each shooting mode are set corresponding to the shooting time.

[0136] Fig.14 FIG. 4 is a diagram showing an example of switching of the shooting mode according to the fourth embodiment. Fig.14 As shown, the storage unit 73 stores a heavyweight mode in addition to the standard mode. The storage unit 73 stores a plurality of preset tables corresponding to geometric magnifications in the heavyweight mode. The doses at each shooting time in the preset table are set to be the same or within a certain range. In addition, the doses at each shooting time in different preset tables are also set to be the same or within a certain range.

[0137] The user can change the shooting mode via the input unit 6. When the user selects the shooting mode, a preset table corresponding to the shooting mode and the geometric magnification is determined. Then, the display unit 5 displays the shooting time stored in the determined preset table. The user selects the shooting time via the input unit 6. The shooting condition determination unit 74 determines the shooting condition corresponding to the shooting time selected by the user as the shooting condition.

[0138] In this way, in the CT apparatus 100 of the fourth embodiment, the user selects an imaging mode according to the type of the object A or the purpose of imaging. The storage unit 73 stores a plurality of preset tables corresponding to the imaging modes or imaging conditions corresponding to each imaging time. Thus, imaging can be performed under more appropriate conditions, and the user can obtain the best image.

[0139] (Other embodiments)

[0140] In this specification, although the embodiments of the present invention are described, the embodiments are provided as examples and are not intended to limit the scope of the invention. The embodiments described above can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the scope of the invention. The embodiments or their modifications are included in the scope or gist of the invention and are also included in the invention described in the claims and their equivalents.

Claims

1. A computer tomography device, comprising: A storage unit for storing a plurality of shooting times required for shooting and shooting conditions preset corresponding to each shooting time when shooting an image of the inspection object by irradiating the inspection object with radiation; A display unit, displaying a plurality of said shooting times; an input unit for receiving a selection of the shooting time displayed on the display unit from a user; and The imaging condition determination unit determines the imaging condition corresponding to the imaging time received by the input unit as the imaging condition at the time of imaging.

2. The computer tomography apparatus according to claim 1, wherein: The imaging condition is set so that the value of the radiation dose detected by the detector is the same or within a certain range at any of the imaging times.

3. The computer tomography apparatus according to claim 2, wherein: By changing the exposure time setting, the dose is adjusted so that the dose value remains the same or falls within a certain range.

4. The computer tomography apparatus according to claim 2, further comprising: A plurality of metal filter units are provided between the radiation source and the object to be inspected and are used to adjust the transmission dose of the radiation. By changing the material or thickness of the metal filter portion, the dose value is adjusted to be the same or within a certain range.

5. The computer tomography apparatus according to claim 2, wherein: By changing the setting of the cumulative number of sheets, the dose value is adjusted to be the same or within a certain range.

6. The computer tomography apparatus according to claim 1 or 2, wherein: The imaging condition is set so that the resolution when the imaging time is set to be long is the same as or higher than the resolution when the imaging time is set to be short.

7. The computer tomography apparatus according to claim 1 or 2, wherein: The photographing condition is set so that the number of views when the photographing time is set to be long becomes the same as or increases compared with the number of views when the photographing time is set to be short.

8. The computer tomography apparatus according to claim 1 or 2, further comprising: A geometrical multiple calculation unit calculates the geometrical multiple; as well as A table selection unit, which selects a preset table corresponding to the geometric magnification; The storage unit stores a plurality of preset tables corresponding to each geometric magnification. In each preset table, a plurality of shooting times and shooting conditions preset corresponding to each shooting time are respectively set. The geometrical magnification calculation unit calculates the geometrical magnification based on the distance from the focus of the radiation source to the inspection object and the distance from the focus of the radiation source to the detector. The table selection unit selects the preset table corresponding to the geometrical magnification calculated by the geometrical magnification calculation unit, The display unit displays the plurality of shooting times set in the preset table selected by the table selection unit.

9. The computer tomography apparatus according to claim 8, wherein: By changing any one or all of the tube current, exposure time, number of accumulated images, and settings of the metal filter unit, the radiation dose is adjusted so that the value is constant or within a certain range.

10. The computer tomography apparatus according to claim 1 or 2, wherein: The storage unit stores shooting modes according to the type of the inspected object and the purpose of shooting. In each shooting mode, the shooting conditions corresponding to a plurality of the shooting times are set. The input unit receives an input of the shooting mode from the user, The display unit displays the plurality of shooting times corresponding to the shooting mode selected by the user.

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