JP5046209B2 - X-ray detector and X-ray CT apparatus - Google Patents

Description

  The present invention relates to an X-ray detector and an X-ray CT (Computed Tomography) apparatus, and more particularly to an X-ray detector having a plurality of detection channels and a reference channel for each column, and such X-ray detection. The present invention relates to an X-ray CT apparatus provided with a scanner.

  In an X-ray CT apparatus using cone beam X-rays, a two-dimensional detector is used as an X-ray detector in accordance with the coverage of cone beam X-rays. The two-dimensional detector is also called a multi-row detector or a multi-slice detector.

  In this type of X-ray detector, multi-row (multi-slice) detection channels are provided, and a reference channel for X-ray intensity correction is provided for each row of detection channels. These channels form a two-dimensional array. Two directions perpendicular to each other in the two-dimensional array are a channel arrangement direction (channel direction) and a channel column arrangement direction (column direction), respectively (for example, see Patent Document 1).

The two-dimensional detector is configured as a connected body of a plurality of modules. Each module corresponds to a subdivision of a two-dimensional array, and each has a unit array of a predetermined matrix size (for example, see Patent Document 1).
JP 2006-102299 A (paragraph number 0017-0022, FIG. 1-3) Japanese Patent Laying-Open No. 2005-192741 (paragraph numbers 0012-0014, FIGS. 1 and 2)

  For the module unit array, if the column pitch is halved and the number of columns is doubled, the spatial resolution in the column direction can be doubled without changing the coverage. By using such a module, the spatial resolution in the column direction of the two-dimensional detector can be refined twice.

  When high definition in the column direction is not required over the entire length in the channel direction, the high definition module may be used only in the central region of the two-dimensional array, for example, and the normal definition module may be used in other regions. Such a two-dimensional detector is called a hybrid detector.

  In an X-ray CT apparatus using a hybrid detector, it is difficult to perform high-quality imaging due to artifacts or the like caused by mismatching between the characteristics of the detection channel and the reference channel.

  Accordingly, an object of the present invention is to realize a hybrid X-ray detector capable of high-quality imaging, and an X-ray CT apparatus including such an X-ray detector.

  The invention for solving the problem is, in a first aspect, an X-ray detector having a plurality of detection channels and a reference channel for each column, wherein the detection channel has a product of the number of columns and the pitch of the columns. It consists of a plurality of groups of detection channels that are equal and have different combinations of the number of columns and the pitch of the columns, and the reference channel is a combination of the number of columns and the pitch of the columns. An X-ray detector comprising a plurality of groups of reference channels that respectively correspond to each other.

  In a second aspect, the invention for solving the problem is characterized in that the plurality of groups of detection channels are two groups of detection channels, and the plurality of groups of reference channels are two groups of reference channels. The X-ray detector according to the first aspect of the invention.

  According to a third aspect of the invention for solving the problem, in the third aspect, the pitch of the row in one of the two groups of detection channels is half of the pitch of the row in the other, and the row of the row in one of the two groups of reference channels. The X-ray detector according to the second aspect, wherein the pitch is half of the pitch of the row on the other side.

  According to a fourth aspect of the invention for solving the problem, in the fourth aspect, the half of the pitch of the reference channel row is performed by interleaving two series of reference channels. It is a line detector.

  The invention for solving the problem is, in a fifth aspect, the X-ray detection according to the fourth aspect, wherein the two series of reference channels are shifted from each other by a half pitch in the column arrangement direction. It is a vessel.

  According to a sixth aspect of the present invention, a tomographic image is obtained by scanning a subject with an X-ray detector having a plurality of detection channels and a reference channel for each column and an X-ray irradiator facing the detection channel. An X-ray CT apparatus for imaging, wherein the detection channel includes a plurality of groups of detection channels in which the product of the number of columns and the pitch of the columns is equal and the combination of the number of columns and the pitch of the columns is different. The X-ray CT apparatus is characterized in that a combination of a number and a column pitch comprises a plurality of groups of reference channels that respectively match a combination of the number of columns and the column pitch in the plurality of groups of detection channels.

In a seventh aspect, the invention for solving the problem is characterized in that the plurality of groups of detection channels are two groups of detection channels, and the plurality of groups of reference channels are two groups of reference channels. The X-ray CT apparatus according to the sixth aspect.

  According to an eighth aspect of the invention for solving the problem, in the eighth aspect, the pitch of the row in one of the two groups of detection channels is half of the pitch of the row in the other, and the row of the row in one of the two groups of reference channels. The X-ray CT apparatus according to the seventh aspect, wherein the pitch is half of the pitch of the row on the other side.

  The invention for solving the problem is that, in the ninth aspect, halving the pitch of the row of reference channels is performed by interleaving two series of reference channels. This is a line CT apparatus.

  The X-ray CT according to the ninth aspect is characterized in that, in the tenth aspect, the two series of reference channels are shifted from each other by a half pitch in the column arrangement direction. Device.

  In the first aspect, the X-ray detector is an X-ray detector having a plurality of rows of detection channels and a reference channel for each row, and the detection channels have the same product of the number of rows and the pitch of the rows. It consists of multiple groups of detection channels with different combinations of number and column pitch, and the reference channel matches the combination of the number of columns and the column pitch in the plurality of groups of detection channels. Therefore, it is possible to realize a hybrid X-ray detector capable of high-quality imaging.

  In a sixth aspect, the X-ray CT apparatus scans a subject with an X-ray detector having a plurality of rows of detection channels and a reference channel for each row and an X-ray irradiator facing the X-ray detector, and takes a tomographic image. In the line CT apparatus, the detection channel includes a plurality of groups of detection channels in which the product of the number of columns and the pitch of the columns is equal and the combination of the number of columns and the pitch of the columns is different, and the reference channel is the number of columns and the columns Since the combination of pitches consists of a plurality of groups of reference channels that respectively match the combination of the number of columns and the pitch of the columns in the plurality of groups of detection channels, a hybrid X-ray detector capable of high-quality imaging is provided. An X-ray CT apparatus can be realized.

  In the second or seventh aspect, the plurality of groups of detection channels are two groups of detection channels, and the plurality of groups of reference channels are two groups of reference channels. Can be obtained.

  In the third or eighth aspect, the row pitch in one of the two groups of detection channels is half of the row pitch in the other, and the row pitch in one of the two groups of reference channels is in the other row. Therefore, the difference in spatial resolution between the two stages can be doubled.

In the fourth or ninth aspect, halving the pitch of the reference channel row is performed by interleaving two series of reference channels, so that the pitch can be easily halved.
In the fifth or tenth aspect, since the two series of reference channels are shifted from each other by a half pitch in the column arrangement direction, the pitch can be halved appropriately.

The best mode for carrying out the invention will be described below with reference to the drawings. Note that the present invention is not limited to the best mode for carrying out the invention.
FIG. 1 shows a schematic configuration of an X-ray CT apparatus. This apparatus is an example of the best mode for carrying out the invention. An example of the best mode for carrying out the invention related to the X-ray CT apparatus is shown by the configuration of the apparatus.

  As shown in FIG. 1, the apparatus has a gantry 100, a table 200, and an operator console 300. The gantry 100 scans the subject 10 carried by the table 200 with the X-ray irradiation / detection device 110, collects projection data of a plurality of views, and inputs it to the operator console 300.

  The operator console 300 performs image reconstruction based on the projection data input from the gantry 100 and displays the reconstructed image on a display 302. Image reconstruction is performed by a dedicated computer in the operator 300.

  The operator console 300 also controls the operation of the gantry 100 and the table 200. Control is performed by a dedicated computer in the operator 300. Under the control of the operator console 300, the gantry 100 scans under a predetermined scanning condition, and the table 200 positions the subject 10 so that a predetermined part is scanned. Positioning is performed by adjusting the height of the top plate 202 and the horizontal movement distance of the cradle 204 on the top plate by a position adjusting mechanism built in the table 200.

  An axial scan can be performed by scanning with the cradle 204 stopped. A cine scan can be performed by continuously performing the axial scan over a predetermined time. By continuously scanning the cradle 204 while continuously moving, a helical scan can be performed.

  The height adjustment of the top plate 202 is performed by swinging the support column 206 around the attachment portion to the base 208. The top plate 202 is displaced in the vertical direction and the horizontal direction by the swing of the column 206. The cradle 204 moves in the horizontal direction on the top plate 202 to cancel the horizontal displacement of the top plate 202. Depending on the scan conditions, the scan is performed with the gantry 100 tilted. The gantry 100 is tilted by a built-in tilt mechanism.

  As shown in FIG. 2, the table 200 may be of a type in which the top plate 202 moves up and down vertically with respect to the base 208. The top plate 202 is moved up and down by a built-in lifting mechanism. In this table 200, the horizontal movement of the top plate 202 accompanying the raising and lowering does not occur.

  FIG. 3 schematically shows the configuration of the X-ray irradiation / detection device 110. As shown in FIG. 3, the X-ray irradiation / detection apparatus 110 detects an X-ray 134 emitted from a focal point 132 of an X-ray tube 130 by an X-ray detector 150. The X-ray detector 150 is an example of an X-ray irradiator in the present invention. The X-ray detector 150 is an example of the X-ray detector in the present invention.

  X-ray detector 150 is also an example of the best mode for carrying out the invention. The configuration of the X-ray detector 150 shows an example of the best mode for carrying out the invention relating to the X-ray detector.

  The X-ray 134 is shaped by an aperture mechanism (not shown) and becomes a cone beam X-ray. The X-ray detector 150 has a two-dimensional X-ray incident surface 152 corresponding to cone beam X-ray coverage. The X-ray incident surface 152 is curved so as to constitute a part of a cylinder. The central axis of the cylinder passes through the focal point 132.

  The X-ray irradiation / detection device 110 rotates around a central axis passing through an imaging center, that is, an isocenter O. The central axis is parallel to the central axis of the partial cylinder formed by the X-ray detector 150.

  The direction of the center axis of rotation is the z direction, the direction connecting the isocenter O and the focal point 132 is the y direction, and the direction perpendicular to the z direction and the y direction is the x direction. These x, y, and z axes are three axes in a rotating coordinate system with the z axis as the central axis.

  FIG. 4 schematically shows a plan view of the X-ray incident surface 152 of the X-ray detector 150. As shown in FIG. 4, the X-ray incident surface 152 has detection cells (cells) 154 two-dimensionally arranged in the x direction and the z direction. That is, the X-ray incident surface 152 is a two-dimensional array of detection cells 154. The detection cell 154 is configured by, for example, a combination of a scintillator and a photodiode.

  Each detection cell 154 constitutes a detection channel of the X-ray detector 150. The arrangement of detection channels in the x direction constitutes a row of detection channels. A plurality of detection channel columns are arranged in the z direction. That is, the X-ray detector 150 is a multi-row or multi-slice X-ray detector. Hereinafter, the x direction is also referred to as the channel direction, and the z direction is also referred to as the column direction.

  FIG. 5 schematically shows the configuration of the X-ray detector 150. As shown in FIG. 5, the X-ray detector 150 includes high-definition modules 510a and 510b and regular-definition modules 520a and 520b. Thereby, the X-ray detector 150 becomes a hybrid detector.

  The hybrid detector may be composed of three or more types of modules having different definition. Hereinafter, an example in which two types of modules are used will be described, but the same applies to a case in which three types of modules are used.

  A plurality of high-definition modules 510a are juxtaposed in the channel direction so as to form the central region of the two-dimensional array. The high definition module 510a is a module for a high definition detection channel.

  A plurality of regular definition modules 520a are arranged side by side in the channel direction so as to form regions on both sides of the central region. The regular definition module 520a is a module for a regular definition detection channel.

  The high-definition module 510b is arranged in parallel to the regular definition module 520a at the right end in the channel direction. This portion is outside the range of FOV (field of view), and is a portion where X-rays enter without passing through the subject 10. The high definition module 510b is a module for a high definition reference channel.

  The regular definition module 520b is arranged in parallel with the regular definition module 520a at the left end in the channel direction. This part is outside the range of the FOV and the X-ray is incident without passing through the subject 10. The normal definition module 520b is a module for a normal definition reference channel.

  Note that the right-end high-definition module 510b and the left-end regular definition module 520b may interchange positions. Hereinafter, an example in which the high-definition module 510b is located at the right end will be described.

  FIG. 6 shows an example of a unit array in the high definition module 510a. As shown in FIG. 6, the high-definition module 510a has, for example, 64 detection rows composed of 16 channels. That is, the unit array of the high-definition module 510a is an array having a matrix size of 16 × 64.

  FIG. 7 shows an example of a unit array in the regular definition module 520a. As shown in FIG. 7, the regular definition module 520a has, for example, 32 detection rows each including 16 channels. That is, the unit array of the regular definition module 520a is an array having a matrix size of 16 × 32.

  The high definition module 510a and the regular definition module 520a have the same unit array coverage. As a result, the high-definition module 510a and the regular definition module 520a become two groups of detection channels in which the product of the number of columns and the pitch of the columns is equal and the combination of the number of columns and the pitch of the columns is different.

  The high-definition module 510a has twice as many columns as the regular definition module 520a, and the column pitch is half that of the regular definition module 520a. As a result, the high-definition module 510a has a spatial resolution twice that of the normal-definition module 520a in the row direction. The multiple of the spatial resolution is not limited to 2 and may be an appropriate multiple. Hereinafter, the description will be made with a double example, but the same applies to other multiples.

  The high definition module 510b has the same configuration as the high definition module 510a. Thus, the high definition module 510b has the same spatial resolution as the high definition module 510a in the row direction. The high-definition module 510b may have a configuration with a smaller number of channels than the high-definition module 510a. Even in this case, the same spatial resolution in the row direction can be maintained.

  The regular definition module 520b has the same configuration as the regular definition module 520a. Thereby, the regular definition module 520b has the same spatial resolution as the regular definition module 520a in the row direction. Note that the regular definition module 520b may have a smaller number of channels than the regular definition module 520a. Even in this case, the same spatial resolution in the row direction can be maintained.

  The high definition module 510b and the regular definition module 520b have the same coverage in the column direction of the unit array. As a result, the high-definition module 510b and the regular definition module 520b become two groups of reference channels in which the product of the number of columns and the pitch of the columns is equal and the combination of the number of columns and the pitch of the columns is different.

  Thus, the X-ray detector 150 has two groups of high-definition and normal-definition spatial resolution in the row direction as detection channels, and correspondingly, high-definition spatial resolution in the row direction as reference channels. And two groups of normal definition channels.

  The X-ray detection signal of the high-definition reference channel is used for X-ray intensity correction of the X-ray detection signal of the high-definition detection channel. The X-ray detection signal of the normal definition reference channel is used for X-ray intensity correction of the X-ray detection signal of the normal definition detection channel.

  The high-definition reference channel has the same characteristics as the high-definition detection channel, and the regular-definition reference channel has the same characteristics as the regular-definition detection channel. For this reason, the artifact etc. which arise from the mismatch of the characteristic of a reference channel and a detection channel do not arise. Therefore, high-quality imaging can be performed by the X-ray detector 150.

  FIG. 8 shows another example of the unit array of the high-definition module 510b. As shown in FIG. 8, the number of channels is 16 in the channel direction (x direction) and 32 in the column direction (z direction). If the arrangement of channels in the z direction is referred to as a row, the channel rows are shifted by a half pitch between adjacent ones in the x direction. That is, the unit array includes two series of channels that are shifted from each other by a half pitch in the column direction.

  Such a unit array has a spatial resolution equivalent to that of the regular definition module 520a on a row-by-row basis, but since adjacent ones are shifted by a half pitch, by interleaving their X-ray detection signals, The spatial resolution can be refined twice. Therefore, a module having such a unit array can be used substantially as a high-definition module.

  The adjacent ones can be shifted by a half pitch by, for example, the shape and arrangement of channels as shown in FIG. That is, each channel has a light-receiving surface that is a parallelogram, and is adjacent to each other so as to be right-down in the x direction. The downward sloping per line corresponds to a half pitch. A module having such a unit array can also be used substantially as a high definition module.

It is a figure which shows the structure of the X-ray CT apparatus of an example of the best form for implementing invention. It is a figure which shows the structure of the X-ray CT apparatus of an example of the best form for implementing invention. It is a figure which shows the structure of a X-ray irradiation / detection apparatus. It is a figure which shows the structure of the X-ray entrance plane of an X-ray detector. It is a figure which shows typically the structure of an example of the X-ray detector of the best form for implementing invention. It is a figure which shows an example of the unit array in a high-definition module. It is a figure which shows an example of the unit array in a regular definition module. It is a figure which shows an example of the unit array in a high-definition module. It is a figure which shows an example of the unit array in a high-definition module.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10: Subject 100: Gantry 110: X-ray irradiation / detection apparatus 130: X-ray tube 132: Focus 134: X-ray 150: X-ray detector 152: X-ray incident surface 154: Detection cell 200: Table 202: Top plate 204: Cradle 206: Prop 208: Base 300: Operator console 510a, 510b: High definition module 520a, 520b: Normal definition module

Claims (10)

An x-ray detector having a plurality of rows of detection channels and a row of reference channels,
The detection channel includes a plurality of groups of detection channels in which the product of the number of columns and the pitch of the columns is equal and the combination of the number of columns and the pitch of the columns is different.
The X-ray detector is characterized in that the reference channel is composed of a plurality of groups of reference channels in which the combination of the number of columns and the pitch of the columns matches the combination of the number of columns and the pitch of the columns in the plurality of groups of detection channels. . The plurality of groups of detection channels are two groups of detection channels;
The X-ray detector according to claim 1, wherein the plurality of groups of reference channels are two groups of reference channels. The row pitch in one of the two groups of detection channels is half the row pitch in the other,
The X-ray detector according to claim 2, wherein the row pitch in one of the two groups of reference channels is half the row pitch in the other. The X-ray detector according to claim 3, wherein the pitch of the reference channel column is halved by interleaving two series of reference channels. 5. The X-ray detector according to claim 4, wherein the two series of reference channels are shifted from each other by a half pitch in a row direction. An X-ray CT apparatus that scans a subject with an X-ray detector having a plurality of rows of detection channels and a reference channel for each row and an X-ray irradiator facing the X-ray detector, and takes a tomogram,
The detection channel includes a plurality of groups of detection channels in which the product of the number of columns and the pitch of the columns is equal and the combination of the number of columns and the pitch of the columns is different.
X-ray CT apparatus characterized in that the reference channel is composed of a plurality of groups of reference channels in which the combination of the number of columns and the pitch of the columns matches the combination of the number of columns and the pitch of the columns in the plurality of groups of detection channels. . The plurality of groups of detection channels are two groups of detection channels;
The X-ray CT apparatus according to claim 6, wherein the plurality of groups of reference channels are two groups of reference channels. The row pitch in one of the two groups of detection channels is half the row pitch in the other,
The X-ray CT apparatus according to claim 7, wherein the row pitch in one of the two groups of reference channels is half of the row pitch in the other. 9. The X-ray CT apparatus according to claim 8, wherein the halving of the pitch of the reference channel row is performed by interleaving two series of reference channels. The X-ray CT apparatus according to claim 9, wherein the two series of reference channels are shifted from each other by a half pitch in a row direction.

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