JP2011232057A - Ct device and imaging method for ct device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a CT device for obtaining a cross sectional image of an analyte having a layer structure in a short time.SOLUTION: The CT device includes a radiation source 1 for emitting a radiation with a radiation optical axis along a tomography face as a center toward the analyte 5 which is imaged by placement on a table 4 so as to allow a layer surface of a layer structure of the analyte 5 to be imaged to cross with the tomography face; a radiation detector 3 for detecting the radiation 2 transmitting the analyte 5 and performing an output as a transmission image; rotation means 7 for relatively rotating the table 4 and the radiation 2; scan control means 9c for performing scanning by controlling the rotation means 7 and the radiation detection means 3 so as to take in and store a plurality of transmission images as scan data by prioritizing a rotation angle to allow the layer surface of the analyte 5 to be close to a state in parallel with the optical axis of the radiation 2; and reconstitution means 9d for reconstituting at least one cross sectional image in parallel with the tomography face of the analyte 5, based on the scan data.

Description

  The present invention relates to a computed tomography apparatus (hereinafter referred to as a CT (Computed Tomography) apparatus) that captures a cross-sectional image of a subject.

  In recent years, the demand for secondary batteries such as lithium ion batteries and nickel metal hydride batteries has been increasing due to the development of mobile devices such as mobile phones and the practical use of electric vehicles. Along with this, the importance of battery inspection for supplying safe and reliable batteries that do not cause short-circuits or fire is increasing. As this battery inspection, a method is known in which a cross-sectional image of a subject having a layered structure is taken and inspected.

  First, FIG. 7 shows a conceptual diagram (cross-sectional view) of a battery 90 as a subject. This figure is a cross-sectional view showing an outline of the structure of a lithium ion battery, a nickel metal hydride battery, a nickel cadmium battery, or the like. In the case 91, a positive electrode plate 92 and a negative electrode plate 93 are housed in multiple layers via a separator (not shown), and the gap is filled with an electrolytic solution 94. For example, the layer pitch (positive electrode plate-positive electrode plate) is about 0.3 mm, the number of turns is several tens of times, and the overall cross-sectional dimension is about 30 mm × 120 mm.

  In order to inspect the battery having such a structure, in the inspection of the battery using the CT apparatus, a cross-sectional image as shown in FIG. 7 is taken and an electrode plate (a general term for the positive electrode plate 92 and the negative electrode plate 93) is taken. Layer wrinkles, layer spacing disturbances, and the like can be confirmed, and changes over time when batteries are used can be tracked and inspected.

  A conventional CT apparatus used for inspection of this battery will be described. A CT apparatus called a so-called RR (Rotate Rotate) system (third generation system) that performs only rotation in a conventional CT apparatus irradiates a subject with radiation (X-rays) generated from a radiation source. Is rotated relative to the radiation with a rotation axis that intersects the direction of the optical axis of the radiation, and the radiation transmitted from the subject is detected one-dimensionally or at every predetermined rotation angle interval during one detected rotation. Detection is performed by a radiation detector having a two-dimensional multiple detection channel, and a cross-sectional image or three-dimensional data of a subject is obtained (tomographic imaging) from the detector output.

  FIG. 8 shows a configuration of a CT apparatus described in Patent Document 1 as a conventional technique. FIG. 8A is a plan view, and FIG. 8B is a front view. In the figure, an X-ray tube 101 and an X-ray detector 103 for detecting a pyramid-shaped X-ray beam 102 generated therefrom with a two-dimensional resolution are arranged to face each other so that they enter the X-ray beam 102. A transmission image (transmission data) of the subject 105 placed on the table 104 is obtained.

  The table 104 is disposed on the XY mechanism 106, and the XY mechanism 106 is disposed on the rotation / lifting mechanism 107. When taking a cross-sectional image of the subject 105, transmission images are obtained in a number of directions (hereinafter referred to as scanning) while the table 104 is rotated once by the rotation / lifting mechanism 107 with respect to the rotation axis RA. A large number of transmission images obtained by this scan can be processed by the control processing unit 108 to obtain cross-sectional images (one or many) of the subject 105. Here, the XY mechanism 106 is used to move the table 104 in a plane orthogonal to the rotation axis RA with respect to the rotation axis RA and adjust the position so that the target portion 105a of the subject 105 is on the rotation axis RA. It is done. Further, the rotation axis RA and the detector 103 can be moved closer to or away from the X-ray tube 101 by the shift mechanism 109, and the imaging magnification (= FDD / FCD) can be changed according to the purpose.

  On the other hand, as a reconstruction processing method, the method described in Non-Patent Document 1 is usually used in the case of a pyramid-shaped X-ray beam. This method is a kind of filtered back projection method (FBP (Filtered Back Projection) method) and performs three-dimensional back projection. A cross-sectional image field (or scan area) 110 shown in FIG. 8 is defined as an area included in the X-ray beam 102 that is always detected by the detector 103 while the table 104 rotates once with respect to the rotation axis RA. The The cross-sectional image field 110 is a substantially cylindrical region around the rotation axis RA, and is a region where a cross-sectional image can be reconstructed without difficulty. Note that the cross-sectional image field 110 decreases in diameter and height in inverse proportion to the increase in photographing magnification.

  By the way, as described in Patent Document 1, there is known a method for tomography by enlarging a part of the subject 105 (hereinafter referred to as ROI (Region of Interest) scanning). In this tomography, as shown in FIG. 8A, the cross-sectional image field 110 is reduced, and the shift mechanism 109 and the XY mechanism 104 are positioned so that the target portion 105 a of the subject 105 is just within the cross-sectional image field 110. To do. Thereby, an enlarged cross-sectional image with high spatial resolution of the target portion 105a can be obtained. Furthermore, the conventional CT apparatus can take a cross-sectional image of the target portion of the layer structure of the battery 90 with high resolution, for example, by ROI scanning.

JP 2002-310943 A L.A.Feldkamp, L.C.Davis and J.W.Kress, Practical cone-beam algorithm, J.Opt.Soc.Am.A / Vol.1, No.6 / June1984

  However, when tomographic imaging of a subject having a layered structure such as a battery, it is necessary to reduce the rotation angle interval (sampling pitch in the rotation direction) for detecting a transmission image during rotation.

  The case of the battery in FIG. 7 will be described as an example. On the cross section, in the linear part of the electrode layer, each electrode plate and the separator are about 0.1 mm in thickness and about 100 mm in length and are very elongated. If such an elongated electrode plate has a large rotation angle interval, a linear false image is generated in the direction along the electrode plate and the resolution in the thickness direction (resolution with respect to the layer structure) is impaired. In this case, it is necessary to make the rotation angle interval for detecting the transmission image during one rotation finer to about 0.06 °, and the 360 ° view number (the number of transmission images taken during one rotation). ) Increases to 6000.

  As described above, the conventional CT apparatus has a problem that it is necessary to increase the number of views in order to ensure the resolution in the direction orthogonal to the layer of the subject having a layered structure, and the tomography time is long.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a CT apparatus that obtains a cross-sectional image of a subject having a layered structure in a short tomographic time.

  In order to achieve the above object, the invention according to claim 1 is a CT apparatus for taking a cross-sectional image of a subject having a layered structure on a table so that a layer surface of the layered structure to be photographed intersects a tomographic plane. A radiation source that emits radiation centered on a radiation optical axis along the tomographic plane toward the subject placed on the radiation detector, and radiation detection means that detects the radiation that has passed through the subject and outputs it as a transmission image And a rotating means for rotating the table and the radiation relative to a rotation axis orthogonal to the tomographic plane, and the layer surface while the rotating means and the radiation detecting means are rotated while controlling the rotating means and the radiation detecting means. Scan control means for performing a preferential scan for preferentially capturing and storing a plurality of transmission images as scan data at a rotation angle close to parallel to the radiation optical axis; And summarized in that it has a reconstruction means for reconstructing at least one cross-sectional image parallel to the tomographic plane of the subject, the.

  With this configuration, scanning is performed with priority given to the rotation angle at which the layer surface of the layered structure to be imaged of the subject is close to parallel to the radiation optical axis (detection of the transmission image with high frequency or limited angle). Since the cross-sectional image of the object is reconstructed from this scan data, the rotation range in which the radiation optical axis that does not contribute to the resolution of the layer structure on the cross-sectional image intersects the layer surface at a large angle as compared with the scan of one rotation. By not giving priority to transmission image detection, the time required for scanning can be shortened while maintaining the resolution in the direction orthogonal to the layer surface. In addition, the time required for reconstruction of the cross-sectional image can be shortened.

  In order to achieve the above object, according to a second aspect of the present invention, in the CT apparatus according to the first aspect, the scan control means is a first unit in which the layer surface is parallel to the radiation optical axis as the preferential scanning. A plurality of transmission images detected while rotating within a first rotation angle range including the first rotation position within ± 60 ° with the rotation position as the center are taken in as first scan data The gist is to perform the first scan stored in (1).

  With this configuration, the first scan is performed in the limited first rotation angle range including the rotation position where the layer surface of the layered structure to be imaged of the subject is parallel to the radiation optical axis, and the first rotation is performed. Since the cross-sectional image of the subject is reconstructed from the first scan data detected in the angle range, the radiation optical axis that does not contribute to the resolution of the layer structure on the cross-sectional image is larger on the layer surface than the one-scan scan. By omitting transmission image detection in the rotation range that intersects at an angle, the time required for scanning can be shortened while maintaining the resolution in the direction orthogonal to the layer surface. In addition, the time required for reconstruction of the cross-sectional image can be shortened.

  In order to achieve the above object, according to a third aspect of the present invention, in the CT apparatus according to the second aspect, the scan control means further includes a 180 ° difference from the first rotational position as the preferential scan. A plurality of transmission images detected while rotating within a second rotation angle range including the second rotation position within ± 60 ° centered on the rotation position 2 as second scan data. The gist is to perform a second scan that is captured and stored.

  With this configuration, as in the invention described in claim 2, as compared with a single rotation scan, transmission image detection in a rotation range in which the radiation optical axis that does not contribute to the resolution of the layer structure on the cross-sectional image intersects the layer surface at a large angle can be performed. By omitting, the time required for scanning can be shortened while maintaining the resolution in the direction orthogonal to the layer surface. In addition, the time required for reconstruction of the cross-sectional image can be shortened.

  In order to achieve the above object, according to a fourth aspect of the present invention, in the CT apparatus according to the second aspect, the scan control means detects a plurality of transmission images in the first scan at every first rotation angle interval. The scan control means, as the preferential scan, further rotates the first rotation angle while rotating the rotation within a third rotation angle range including at least a part outside the first rotation angle range. The gist is that a third scan is performed in which a plurality of transmission images detected at a third rotation angle interval larger than the interval are captured and stored as third scan data.

  In order to achieve the above object, according to a fifth aspect of the present invention, in the CT apparatus according to the third aspect, the scan control means detects a plurality of transmitted images at every first rotation angle interval in the first scan. In the second scan, a plurality of transmission images are detected at every second rotation angle interval, and the scan control means further includes the first rotation angle range and the second rotation as the preferential scan. A third rotation angle interval that is larger than both the first rotation angle interval and the second rotation angle interval while rotating in a third rotation angle range that includes at least a portion outside the rotation angle range. The gist of the present invention is to perform a third scan that captures and stores a plurality of transmission images detected every time as third scan data.

  With the configuration according to claims 4 and 5, the transmission image detection in the rotation range in which the radiation optical axis that does not contribute to the resolution of the layer structure on the cross-sectional image intersects the layer surface at a large angle as compared with the normal one-revolution scan. By carrying out at rough rotation angle intervals, the time required for scanning and the time required for reconstruction of the cross-sectional image can be reduced while maintaining the resolution in the direction orthogonal to the layer surface, and the structure other than the layered structure on the cross-sectional image is also improved to some extent. Can be represented.

In order to achieve the above object, an invention according to claim 6 is an imaging method of a CT apparatus for imaging a cross-sectional image of a subject having a layered structure, wherein the layer surface of the layered structure to be imaged intersects a tomographic plane. A radiation source that emits radiation about the radiation optical axis along the tomographic plane toward the subject placed on the table, and radiation that has passed through the subject are detected and output as a transmission image. Radiation detection means, rotation means for rotating the table and the radiation relative to a rotation axis orthogonal to the tomographic plane, and controlling the rotation means and the radiation detection means within a predetermined rotation angle range Scan control means for performing a scan for capturing and storing a plurality of transmission images detected while rotating as scan data, and a cross-sectional image of the subject from the stored scan data In the CT apparatus having the reconstructing means for reconfiguring, the process of specifying the first rotation position where the layer surface is parallel to the radiation optical axis, and the rotation angle close to the first rotation position while performing the rotation Preferentially scanning a plurality of transmission images as scan data and storing them, and reconstructing at least one cross-sectional image parallel to the tomographic plane of the subject from the scan data And having a process of performing.
With this method, the same effect as that of the first aspect of the invention can be obtained.

In order to achieve the above object, according to a seventh aspect of the present invention, in the CT apparatus imaging method according to the sixth aspect, the preferential scan is within ± 60 ° about the first rotation position. The first rotation angle range that includes the first rotation position is scanned, or the second rotation position that is 180 ° different from the first rotation position is within ± 60 °, and the The gist of the present invention is a scan obtained by adding a scan in the second rotation angle range including the second rotation position.
By this method, the same effects as those of the inventions of claims 2 and 3 can be obtained.

  According to the present invention, it is possible to provide a CT apparatus that obtains a cross-sectional image of a subject having a layered structure in a short tomographic time.

Schematic diagram showing the configuration of the CT apparatus according to the first embodiment of the present invention ((a) plan view, (b) front view) Fig. 1 is a flowchart of tomography according to the first embodiment of the present invention. The figure (plan view) which shows the mounting state to the table of the battery concerning a 1st embodiment of the present invention. Example of scan rotation angle range according to the first embodiment of the present invention An example of the rotation angle range of the scan according to the third modification of the first embodiment of the present invention Example of scan rotation angle range according to Modification 5 of the first embodiment of the present invention Conceptual diagram (cross-sectional view) of the battery 90 as the subject Schematic diagram showing the configuration of a conventional CT apparatus ((a) plan view, (b) front view)

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 6 as examples of the present invention.

(Configuration of the first embodiment of the present invention)
The configuration of the first embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a schematic diagram ((a) plan view, (b) front view) showing a configuration of a CT apparatus according to the first embodiment of the present invention. As shown in FIG. 1, a pyramid having an X-ray tube (radiation source) 1 and an optical axis (radiation optical axis) L that is a part of X-rays emitted from an X-ray focal point F of the X-ray tube 1 as a center. An X-ray detector (radiation detection means) 3 for detecting the X-ray beam (radiation) 2 with a two-dimensional resolution is arranged oppositely and placed on the table 4 so as to enter the X-ray beam 2. The X-ray beam 2 transmitted through the subject 5 is detected by the X-ray detector 3 and output as a transmission image (transmission data).

  The table 4 is disposed on an XY mechanism 6, and the XY mechanism 6 is disposed on a rotation / lifting mechanism (rotating means) 7. The table 4 rotates perpendicularly to the X-ray beam 2 by the rotation / lifting mechanism 7 (the X-ray beam 2 may intersect with the X-ray beam 2 and be substantially perpendicular to the direction of the optical axis L). At the same time, it is moved (lifted) in the z direction parallel to the rotation axis RA. The XY mechanism 6 moves the table 4 in the XY plane perpendicular to the rotation axis RA with respect to the rotation axis RA and the X-ray beam 2.

  The tomographic plane TP is defined as a plane that passes through the X-ray focal point F and is perpendicular to the rotation axis RA, and the optical axis L is on the tomographic plane TP. Further, the rotation mechanism RA (and the table 4) and the X-ray detector 3 can be moved closer to or away from the X-ray tube 1 by the shift mechanism (imaging magnification setting means) 8 and rotated with the X-ray focal point F of the X-ray tube 1. An imaging distance FCD (Focus to rotation Center Distance) between the axis RA and a detection distance FDD (Focus to Detector Distance) between the X-ray focal point F and the detection surface 3a of the X-ray detector 3 are set. be able to.

  Here, the XY mechanism 6 is used to adjust the position of the target portion of the subject 5 on the rotation axis RA, and the shift mechanism 8 changes the imaging magnification (= FDD / FCD) according to the purpose. Therefore, the z movement of the rotation / lifting mechanism 7 is used to adjust the target portion of the subject 5 to the height of the X-ray beam 2. The rotation of the rotation / lifting mechanism 7 is used to obtain a transmission image in a number of directions by rotating the subject 5 with respect to the X-ray beam 2 when taking a cross-sectional image.

  The cross-sectional image field (or scan area) 10 shown in FIG. 1 is defined as an area included in the X-ray beam 2 that is always measured during one rotation. The cross-sectional image field 10 is a substantially cylindrical region having the rotation axis RA as an axis, and is a region where a cross-sectional image can be reconstructed without difficulty. As other components, a control processing unit 9 that controls each mechanism (XY mechanism 6, rotation / elevating mechanism 7, shift mechanism 8) and processes transmission data from the X-ray detector 3, processing results For example, an X-ray control unit (not shown) for controlling the X-ray tube 1.

  The control processing unit 9 is a normal computer and includes a CPU, a memory, a disk (nonvolatile memory), a display unit 9a, an input unit (keyboard, mouse, etc.) 9b, a mechanism control board, an interface, and the like.

  The control processing unit 9 receives signals (encoder pulses and the like) of the operation positions of the mechanism units 6, 7, and 8 from the mechanism control board and controls the mechanism units 6, 7, and 8 to adjust the position of the subject. In addition to performing scanning (tomographic scanning) and the like, transmission data collection command pulses and the like are sent to the X-ray detector 3. Note that an encoder (not shown) is attached to each of the mechanism units 6, 7, and 8, and the XY movement positions X and Y of the table 4 by the XY mechanism 6, the z movement position z and the rotation angle of the rotation / lifting mechanism 7. φ and FCD and FDD by the shift mechanism 8 are read and sent to the control processing unit 9 respectively.

  Further, the control processing unit 9 collects transmission data from the X-ray detector 3 at the time of tomography, stores it, and performs reconstruction processing to obtain cross-sectional images of one or a plurality of subjects parallel to the tomography plane. Created and displayed on the display unit 9a. Further, the control processing unit 9 issues a command to an X-ray control unit (not shown), specifies tube voltage and tube current, and instructs X-ray emission and stop. The tube voltage and tube current can be changed according to the subject.

  As shown in FIG. 1, the control processing unit 9 reads and stores a plurality of transmission images detected while rotating the table 4 within a predetermined range as scan data as a functional block for the CPU to function by reading software. A scan control unit (scan control unit) 9c for performing scanning, a reconstruction unit (reconstruction unit) 9d for creating a cross-sectional image using scan data, and the like are provided.

(Operation of the first embodiment)
The operation of the first embodiment having the above-described configuration will be described with reference to FIGS. 7 and 2 to 4, taking as an example the case where the battery 90 is imaged as the subject 5.

  FIG. 7 shows a conceptual diagram (cross-sectional view) of a battery 90 that is a subject. This figure is a cross-sectional view showing an outline of the structure of a lithium ion battery, a nickel metal hydride battery, a nickel cadmium battery, or the like. In the case 91, a positive electrode plate 92 and a negative electrode plate 93 are housed in multiple layers via a separator (not shown), and the gap is filled with an electrolytic solution 94. For example, the layer pitch (positive electrode plate-positive electrode plate) is about 0.3 mm, the number of turns is several tens of times, and the overall cross-sectional dimension is about 30 mm × 120 mm.

FIG. 2 is a flowchart of tomography according to the first embodiment. As the tomography process of this example,
(1) Steps for placing a battery (2) Steps for setting photographing conditions (3) Steps for scanning (4) Steps for reconfiguration are provided. Hereinafter, each step will be described.

(1) Step of Placing Battery As shown in FIG. 2, in step S1, the operator places the battery 90 on the table 4 as follows. FIG. 3 is a diagram (plan view) showing a state where the battery is placed on the table. First, the rotation angle of the table 4 is reset to 0 ° (first rotation position), and then the layer surface 12 of the layered structure in the region (ROI: region of interest) 11 of the battery 90 to be imaged is the tomographic surface TP. And the layer surface 12 is placed so as to be parallel to the optical axis L.

(2) Step of setting shooting conditions Next, shooting conditions are set in step S2. The imaging conditions include geometric conditions, X-ray conditions, scan conditions, reconstruction conditions, and the like. As the geometric condition setting, a command is input from the input unit 9b, and the XY mechanism 6 is controlled so that the region 11 to be photographed is approximately on the rotation axis RA. The shift mechanism 8 is controlled so as to coincide with the cross-sectional image field 10 to set the photographing magnification. In addition, the height of the region 11 to be photographed is adjusted to the tomographic plane TP by controlling the rotary elevating mechanism 7 from the input unit 9b.

  As the X-ray condition setting, a tube voltage and a tube current suitable for the subject are set. As the scanning condition setting, the transmission image is detected preferentially (with high frequency or limited angle) at a rotation angle at which the layer surface 12 is nearly parallel to the optical axis L. Specifically, as the scan condition setting, the rotation angle range (the first rotation position) is within a range of ± 60 ° centered on 0 ° (first rotation position) and includes 0 ° (120 ° or less). 1 rotation angle range) is input and set as a scan range. For example, FIG. 4 shows an example of the rotation angle range of scanning. Here, a 45 ° range centered on 0 ° is set as the rotation angle range.

  As the scan condition setting, a rotation angle interval for detecting a transmission image (for example, 0.075 °), an integral frame number of the transmission image (for example, 5), and the like are further set. As reconstruction conditions, the number of cross-sectional images and the interval in the direction of the rotation axis (cross-sectional position with respect to the tomographic plane TP) are set.

(3) Scanning Step After step S2, scanning is performed in step S3. When the operator inputs a scan start, the scan control unit 9c controls the rotary elevating mechanism 7 and the X-ray detector 3 to set the table 4 while rotating the table 4 (continuously or in steps) within the set rotation angle range. A plurality of transmission images detected at each (first) rotation angle interval are captured and stored as (first) scan data.

(4) Step of performing reconstruction After step S3, in step S4, the reconstruction unit 9d parallelizes the sectional image in the sectional image field 10 of the battery 90 from the scan data to the tomographic plane TP (at the set sectional position). ) Reconstruct at least one cross-sectional image for display and storage. The reconstruction is performed by the normal filtered back projection method, but the difference is that normally, the filtered back projection for 360 ° is performed, but here, only the data in the scanned angular range is filtered back projected. Difference (ie, equivalent to backprojecting 0 over an angular range that was not scanned).
Thus, the flow of FIG. 2 ends.

(Effects of the first embodiment)
According to the first embodiment, scanning is performed in a rotation angle range of scanning (45 °) around the rotation position where the layer surface 12 of the layered structure in the region 11 to be photographed of the battery 90 is parallel to the optical axis L. Since the cross-sectional image of the battery 90 is reconstructed from the scan data detected in this rotational angle range, the optical axis L that does not contribute to the resolution of the layer structure on the cross-sectional image is compared with the scan of one rotation. By omitting transmission image detection in a rotation range that intersects the layer surface 12 at a large angle, the time required for scanning can be shortened while maintaining the resolution in the direction orthogonal to the layer surface. In addition, the time required for reconstruction of the cross-sectional image can be shortened. Specifically, scanning at 360 ° is normally performed at 45 °, so that the scan time and reconstruction time are about 1/8.

  Actually, comparing {Image 1: Cross-sectional image taken by tomography under the conditions of the first embodiment (45 ° scan)} with {Image 2: Cross-sectional image taken by a 360 ° scan under the same conditions} Although the image noise is slightly larger in the image 1, the resolution in the direction orthogonal to the layer surface 12 is the same. The noise of the image 1 is large because the data amount in the direction in which the optical axis L is along the layer surface is half that of the image 2. Therefore, the number of integrated frames under the shooting conditions of image 1 was doubled and image 1 'was shot and compared. As a result, image 1' and image 2 were indistinguishable.

  Furthermore, according to the first embodiment, as a secondary effect, there is an effect that ring-shaped artifacts are hardly generated. Actually, when comparing image 1 and image 2 described above, a faint ring-shaped artifact centered on the rotation axis RA could be recognized in image 2, but not in image 1 at all.

(Modification of the first embodiment)
In addition, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.

(Modification 1)
In the first embodiment, the scan rotation angle range of 45 ° is set around the rotation position at which the layer surface 12 of the layered structure is parallel to the optical axis L. However, the rotation angle range is not necessarily 45 °. . The layered structure of the battery 90 is locally inclined from the layer surface 12 by winding unevenness or wrinkles. Since it is only necessary to obtain a transmission image from the direction within the tilt range, the rotation angle range may be set so as to include the expected tilt angle range α.

Precisely, since the layer structure of the battery has a thickness within the field of view, the angle from the rotational position where X-rays are transmitted parallel to the upper end layer of the thickness to the rotational position where X-rays are transmitted parallel to the lower end layer of the thickness. It is necessary to increase the rotation angle range by β. Therefore, the rotation angle range may be set to increase by β and exceed α + β. This angle β corresponds to the angle of this thickness viewed from the X-ray focal point F, and the value of β is the maximum at the maximum thickness (= diameter of the sectional image field 10), and at this time β is the fan angle θ. It corresponds to ₀ (see FIG. 1). In a normal battery, α + β does not exceed 120 °, so the rotation angle range may be set to include 0 ° within ± 60 ° (total width of 120 ° or less), but as narrow as possible according to the subject. It is possible to increase the speed by setting. The width of the rotation angle range may be as small as 20 ° or 10 °, for example, when the flatness of the subject is good.

(Modification 2)
In the first embodiment, the rotation angle range of 45 ° scanning is set symmetrically around the rotational position where the layer surface 12 of the layered structure is parallel to the optical axis L (usually preferably symmetrical), but it is precisely symmetrical. It does not have to be, and it is only necessary that the outline is symmetrical.

(Modification 3)
In the first embodiment, the battery 90 is within ± 60 ° centered on a second rotation position (180 °) that is 180 ° different from the (first) rotation position (0 °) on which the battery 90 is placed. A second rotation angle range (120 ° or less) that is a continuous range including the second rotation position is set, and the table 4 is rotated within the second rotation angle range for each second rotation angle interval. A second scan that captures and stores a plurality of transmission images detected in step S2 as second scan data is performed, and the tomography of the battery 90 is performed from the first (first) scan data and the second scan data. It is also possible to reconstruct at least one cross-sectional image parallel to the imaging surface TP.

  FIG. 5 is an example of a scan rotation angle range according to the third modification, and the second rotation angle range is a 45 ° range centered on 180 °. The reconstruction in this case may be performed by reconstructing the first scan data as described in the first embodiment, similarly reconstructing the second scan data, and adding both cross-sectional images. Further, the second scan data may be back-projected by the filter correction after the cross-sectional image obtained by the back-projection of the first scan data by the filter correction.

  Note that the second rotation angle range is not within a range of 45 ° centered on 180 °, but within ± 60 ° centered on 180 °, as in the first rotation angle range, and the second rotation position ( The rotation angle range may include 180 °. The second rotation angle interval is usually the same as the first rotation angle interval, but may be different. According to the third modification, the same effect as in the first embodiment can be obtained.

  Specifically, scanning at 360 ° normally requires only 45 ° and 45 ° scanning, so that the scan time and reconstruction time are about 1/4. Actually, {Image 3: Cross-sectional image taken by tomography under the conditions of Modification 3 (45 ° and 45 ° scans)} and {Image 2: Cross-sectional image taken by 360 ° scans under the same conditions} are compared. The images 3 and 2 are so indistinguishable from each other. Further, in image 2, a faint ring-shaped artifact centering on the rotation axis RA could be recognized, but in image 3, it was not recognized at all.

(Modification 4)
In the first embodiment, a planar layer portion is selected as the region 11 of the battery 90 to be photographed, but the layer may be a curved surface. In this case, if the tangential direction of the layer portion to be observed is set as the layer surface 12, the layer portion roughly parallel to the layer surface 12 can be obtained as a good cross-sectional image.

(Modification 5)
In the first embodiment, when the battery 90 includes a structure other than the layered structure, there is a case where it is desired to photograph the structure so that the other structure is also expressed to some extent on the cross-sectional image obtained by photographing the layered structure. In this case, in addition to the first scan of the first embodiment (and the second scan of the third modification), a rough third scan with a larger rotation angle interval is added to the first scan (and the second scan). ) And the scan data of the third scan, the cross-sectional image of the battery 90 can be reconstructed.

  The third scan includes the first rotation angle interval (and the first rotation angle) while rotating in the third rotation angle range including at least a part outside the first rotation angle range (and the second rotation angle range). A plurality of transmission images detected at each third rotation angle interval larger than any one of the two rotation angle intervals are captured and stored as third scan data.

FIG. 6 shows an example of the scan rotation angle range according to the fifth modification.
The third scan may be a full scan with a rotation angle range of 360 °, or a half scan with 180 ° + fan angle θ _{0 to} 360 °, but the first rotation angle range (and the second rotation) may also be used. A scan that replenishes a portion outside the (angle range) may also be used. As the rotation angle range of this replenishment scan, all of the outer portion may be sufficient, or a part of the outer portion may be sufficient, or it may overlap with the first rotation angle range (and the second rotation angle range). Good.

The reconstruction unit 9d reconstructs at least one cross-sectional image parallel to the tomographic plane of the subject from the first scan data, the second scan data, and the third scan data.
Reconstruction is obtained by reconstructing cross-sectional images with the first to third scan data, and adding these cross-sectional images (including weighted addition). Further, the first to third scan data may be continuously subjected to filter-corrected backprojection (including weighted backprojection).

  According to the fifth modification, compared with a normal one-revolution scan, transmission image detection in a rotation range in which the optical axis L that does not contribute to the resolution of the layer structure on the cross-sectional image intersects the layer surface 12 at a large angle is performed with a rough rotation angle interval. By implementing this, it is possible to reduce the time required for scanning and the time required for reconstruction of the cross-sectional image while maintaining the resolution in the direction orthogonal to the layer surface 12, and the structure other than the layered structure is also shown to some extent on the cross-sectional image. You can

(Modification 6)
In the first embodiment, the rotation angle interval for detecting the transmission image is constant, but may be changed as a function of the rotation angle. For example, continuously or stepwise, the closer to 0 ° (first rotational position), the smaller.

  Further, when the rotation angle interval is changed as a function of the rotation angle, the scan rotation angle range does not need to be limited to 120 ° or less. That is, the rotation angle interval may be changed continuously or stepwise so that the rotation position becomes smaller as it approaches 0 ° and 180 ° and becomes larger as it approaches 90 ° and 270 °.

(Modification 7)
In the first embodiment, the table 4 (battery 90) is rotated with respect to the X-ray beam 2, but the rotation may be relative. For example, the X-ray tube 1 and the X-ray detector 3 may be rotated with respect to the rotation axis RA without rotating the table 4.

In the first embodiment, the table 4 is moved XY relative to the rotation axis RA and the X-ray beam 2, but the XY movement may be relative. For example, the rotation axis RA and the X-ray beam 2 (X-ray tube 1 and X-ray detector 3) may be moved XY without moving the table 4 in the XY direction.
In the first embodiment, the table 4 is moved by z with respect to the X-ray beam 2, but the z movement may be relative. For example, the X-ray beam 2 (X-ray tube 1 and X-ray detector 3) may be moved by z without moving the table 4 by z.

(Modification 8)
In the first embodiment, the battery 90 has been described as an example of the subject. However, the subject of the present invention is not limited to the battery, and subjects having other layered structures such as capacitors, coils, multilayer substrates, etc. It can be effectively applied to.
(Modification 9)
In the first embodiment, X-rays are used as radiation. However, the radiation is not limited to X-rays and may be transmissive radiation. For example, the radiation may be γ rays or microwaves.

DESCRIPTION OF SYMBOLS 1 ... X-ray tube 2 ... X-ray beam 3 ... X-ray detector 4 ... Table 5 ... Subject 6 ... XY mechanism 7 ... Rotation / lifting mechanism 8 ... Shift mechanism 9 ... Control processing part 9a ... Display part 9b ... Input part 9c: Scan control unit 9d: Reconstruction unit 10: Cross-sectional image field of view 11: Area 12 to be photographed ... Layer surface 90 ... Battery 91 ... Case 92 ... Positive electrode plate 93 ... Negative electrode plate 94 ... Electrolytic solution 101 ... X-ray tube 102 ... X-ray beam 103 ... X-ray detector 104 ... Table 105 ... Subject 105a ... Part of interest 106 ... XY mechanism 107 ... Rotation / lifting mechanism 108 ... Control processing part 109 ... Shift mechanism 110 ... Cross-sectional image field of view

Claims (7)

A CT apparatus for photographing a cross-sectional image of a subject having a layered structure,
A radiation source that emits radiation around a radiation optical axis along the tomography plane toward a subject placed on a table so that a layer surface of the layered structure to be imaged intersects the tomography plane; Radiation detecting means for detecting radiation transmitted through the specimen and outputting it as a transmission image; rotating means for rotating the table and the radiation relative to a rotation axis orthogonal to the tomographic plane;
The rotation means and the radiation detection means are controlled to rotate, and the rotation angle at which the layer surface is close to parallel to the radiation optical axis is preferentially taken in and stored as a plurality of transmission images as scan data. Scan control means for performing the scan;
Reconstructing means for reconstructing at least one cross-sectional image parallel to the tomographic plane of the subject from the scan data;
CT apparatus characterized by having. The CT apparatus according to claim 1,
The scan control means includes, as the preferential scan, a first surface that includes the first rotational position within ± 60 ° about the first rotational position where the layer surface is parallel to the radiation optical axis. Performing a first scan that captures and stores a plurality of transmission images detected while rotating in a rotation angle range of 1 as first scan data;
CT apparatus characterized by the above. The CT apparatus according to claim 2, wherein
The scan control means includes the second rotation position within ± 60 ° centered on a second rotation position that is 180 ° different from the first rotation position as the preferential scan. Performing a second scan that captures and stores a plurality of transmission images detected while rotating in the second rotation angle range as second scan data;
CT apparatus characterized by the above. The CT apparatus according to claim 2, wherein
The scan control means detects a plurality of transmission images at the first rotation angle interval in the first scan,
The scan control means, as the preferential scan, further rotates the rotation within a third rotation angle range including at least a part outside the first rotation angle range, based on the first rotation angle interval. Performing a third scan that captures and stores a plurality of transmission images detected at large third rotation angle intervals as third scan data;
CT apparatus characterized by the above. The CT apparatus according to claim 3.
The scan control means detects a plurality of transmission images at each first rotation angle interval in the first scan, detects a plurality of transmission images at the second rotation angle interval in the second scan,
The scan control means, as the preferential scan, further rotates the rotation within a third rotation angle range including at least a part outside the first rotation angle range and the second rotation angle range. A third scan that captures and stores, as third scan data, a plurality of transmission images detected for each third rotation angle interval that is greater than either the first rotation angle interval or the second rotation angle interval. Carry out the
CT apparatus characterized by the above. An imaging method for a CT apparatus for imaging a cross-sectional image of a subject having a layered structure,
A radiation source that emits radiation around a radiation optical axis along the tomography plane toward a subject placed on a table so that a layer surface of the layered structure to be imaged intersects the tomography plane; Radiation detecting means for detecting radiation transmitted through the specimen and outputting it as a transmission image; rotating means for rotating the table and the radiation relative to a rotation axis perpendicular to the tomography plane; and the rotating means; From the stored scan data, a scan control unit that controls the radiation detection unit to perform a scan that captures and stores a plurality of transmission images detected while rotating the image within a predetermined rotation angle range as scan data. In a CT apparatus having reconstruction means for reconstructing a cross-sectional image of the subject,
Identifying a first rotational position at which the layer surface is parallel to the radiation optical axis;
A process of performing a preferential scan that preferentially captures and stores a plurality of transmission images as scan data at a rotation angle close to the first rotation position while rotating.
Reconstructing at least one cross-sectional image parallel to the tomographic plane of the subject from the scan data;
An imaging method for a CT apparatus, comprising: The imaging method of the CT apparatus according to claim 6,
The preferential scan is a scan of a first rotation angle range that is within ± 60 ° around the first rotation position and includes the first rotation position, or further, the first rotation. A scan within a range of ± 60 ° centered on a second rotation position that is 180 ° different from the position, plus a scan of a second rotation angle range that includes the second rotation position.
A CT apparatus imaging method characterized by the above.

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