JP2000232977A - X-ray ct device - Google Patents

X-ray ct device

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Publication number
JP2000232977A
JP2000232977A JP11035998A JP3599899A JP2000232977A JP 2000232977 A JP2000232977 A JP 2000232977A JP 11035998 A JP11035998 A JP 11035998A JP 3599899 A JP3599899 A JP 3599899A JP 2000232977 A JP2000232977 A JP 2000232977A
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JP
Japan
Prior art keywords
ray
slice width
processing
projection data
ray detector
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP11035998A
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Japanese (ja)
Inventor
Yoshihiro Inoue
芳浩 井上
Original Assignee
Shimadzu Corp
株式会社島津製作所
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Shimadzu Corp, 株式会社島津製作所 filed Critical Shimadzu Corp
Priority to JP11035998A priority Critical patent/JP2000232977A/en
Publication of JP2000232977A publication Critical patent/JP2000232977A/en
Pending legal-status Critical Current

Links

Abstract

(57) [Summary] [PROBLEMS] To obtain a tomographic image of a slice width before division by dividing the slice width direction and collecting projection data without increasing the cost. SOLUTION: A multi-line type X-ray detector 25 and a multi-line compatible DAS 26 divide and collect projection data of a subject M from multiple directions in a circumferential direction in a slice width direction. The reconstruction of the tomographic image of the slice width before division is performed by the first processor 1 until the respective absorption coefficients obtained from the collected projection data are added in the slice width direction, and the processing result is transmitted. The data is transmitted to the second processing unit 5 via the paths 28 and 40, and the second processing unit 5 performs the subsequent processing. First
The processor 1 includes an X-ray irradiation mechanism 24, an X-ray detector 25, and D
It is configured to rotate integrally with the AS 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray CT apparatus for capturing a tomographic image, and in particular, to collect and collect projection data of a subject from multiple orbiting directions in a slice width direction. The present invention relates to an X-ray CT apparatus that reconstructs a tomographic image having a slice width before division based on projection data.

[0002]

2. Description of the Related Art As shown in FIG. 5, a conventional X-ray CT apparatus of this type includes a bed (not shown), a gantry 20, a console 30, and the like.

The bed is provided with a bed base (not shown) that can be raised and lowered and a top plate 12, and the top plate 12 on which the subject M is mounted is placed horizontally with respect to the bed base (perpendicular to the plane of FIG. 5). The subject M can be inserted into and removed from the opening 21 of the gantry 20 by sliding in a desired direction.

In the gantry 20, there are provided an X-ray irradiation mechanism 24 comprising an X-ray tube 22 and an X-ray collimator 23, an X-ray detector 25, a data acquisition unit (DAS) 26, a rotating stand 27 and the like. . These devices 22 to 26 are mounted on a rotary gantry 27 with the X-ray irradiating mechanism 24 and the X-ray detector 25 facing each other, and by rotating the rotary gantry 27, the X-ray irradiating mechanism 24 and the X-ray detecting The X-ray irradiation mechanism 24, the X-ray detector 25, and the DAS
26 is integrally rotated around the opening 21 (the subject M inserted into the opening 21).

[0005] The X-ray collimator 23 converts the X-rays emitted from the X-ray tube 22 into fan beams FB having a predetermined slice width.
To prevent unnecessary exposure of the subject M, and to suppress the deterioration of image quality due to scattered radiation. X-ray detector 25
Is configured such that a plurality of X-ray detection elements are arranged in the rotation direction (the direction in which the fan beam FB spreads) so that transmitted X-rays from a plurality of directions can be simultaneously detected by one collection of projection data. , DAS 26 integrates transmitted X-rays for each X-ray detection element and collects projection data from a direction corresponding to each X-ray detection element. Then, the rotary gantry 27 is rotated while the subject M is inserted into the opening 21, and projection data is collected every time the rotary gantry 27 is rotated by a predetermined angle. ) To collect projection data from multiple directions around the subject M. Further, the projection data collected by the DAS 26 is transmitted from the rotating DAS 26 to the rotating frame 27, a rotation / fixing data transmission unit 28 for performing data transmission between the rotating part and the fixed part by a brush or the like, and a fixed transmission. Cable 4
After that, the image data is supplied in real time to an image reconstruction processing unit 31 that performs processing for reconstructing a tomographic image.

The image reconstruction processing unit 31 stores a supplied projection data of the subject M from multiple directions in the circling direction, and a processor that performs various processes from reconstructing a tomographic image from the projection data. 33 and the like.

[0007] Until a tomographic image is reconstructed from projection data, the following processing is performed. That is, first, hardware such as the X-ray tube 22 and the X-ray detector 25 performs offset subtraction to remove an error (offset) superimposed on the collected projection data, and then performs logarithmic multiplication by round operation. The absorption coefficient of the subject M from the direction is calculated, and an image reconstruction operation such as convolution conversion or back projection is performed using the calculation result to reconstruct a tomographic image.

[0008] As shown in FIG. 5, the image reconstruction processing section 31 is conventionally provided in the console 30. That is, the conventional apparatus is configured so that all processes from reconstructing a tomographic image from projection data are performed in the console 30.

By the way, an X-ray detector 25 mounted on this type of X-ray CT apparatus has generally been described in FIG.
As shown in (a), the X-ray detecting element 25a has a one-dimensional array structure in which the X-ray detecting elements 25a are arranged in one line along the rotation direction of the X-ray detector 25, and detects transmitted X-rays in the slice width SL direction collectively. The so-called single-line type. 6 indicates channels of the X-ray detection elements 25a arranged in the rotation direction of the X-ray detector 25.

However, this single-line type X
In the case of the line detector 25, an accurate tomographic image cannot be obtained, for example, when the absorption coefficient of a substance in the slice width SL is partially different, such as when bones partially exist in the slice width SL. There was a problem.

For example, as shown in FIG. 7A, when there is a portion having an absorption coefficient of μa and μb (μa ≠ μb) within a slice width SL, a single-line type X-ray detector 25 is mounted. In some devices, the collected projection data is (Ia +
Ib), the absorption coefficient of this portion (μa + μb)
Is calculated by logarithmic calculation based on the projection data (Ia + Ib).

The absorption coefficient (μa + μb) of this portion is
[Log (Io / Ia) / L] + [log (Io / Ib) / L]
, But due to the non-linearity of the logarithmic operation, log (Io /
(Ia + Ib)) @ log (Io / Ia) + log (Io / I
b), and the absorption coefficient μs obtained from the projection data (Ia + Ib) does not coincide with (μa + μb).
An accurate tomographic image of this slice width SL cannot be obtained.

Here, as shown in FIG. 7B, the projection data Ia, Ib of the portion having the absorption coefficient μa and the portion having the absorption coefficient μb are shown.
Can be collected individually, the absorption coefficient (μa + μ
b) can be determined accurately.

Therefore, in recent years, as shown in FIG.
As a two-dimensional array structure in which the X-ray detection elements 25a are arranged in a plurality of rows along the rotation direction of the X-ray detector 25, the transmission X-rays in the slice width SL direction can be divided and detected in the slice width SL direction. So-called multi-line type X-ray detector 25, and a so-called multi-line type D capable of collecting projection data for each line.
There has been proposed an X-ray CT apparatus equipped with the AS 26 and configured to be able to divide and collect projection data of the subject M from multiple directions in the slice width SL direction.

After calculating each absorption coefficient from each projection data, the image reconstruction unit 31 of this apparatus performs an operation of adding each absorption coefficient in the slice width direction for each channel Ch, and the calculation result is obtained. Is performed to reconstruct a tomographic image having a slice width SL before division.

[0016]

However, an X-ray CT equipped with the multi-line type X-ray detector 25 described above.
In the case of the apparatus, DAS2
The number of projection data output from the X-ray CT is determined by the X-ray CT apparatus equipped with the single-line type X-ray detector 25 described above.
This is the number obtained by multiplying the number of projection data output from the AS 26 by the number of divisions of the slice width SL. For example, the number of channels Ch in the rotation direction of the single-line type and the multi-line type X-ray detector 25 is m (for example, 600), and the number of divisions of the slice width SL of the multi-line type X-ray detector 25 is n.
(For example, 4), the X-ray with the single-line X-ray detector 25 mounted in one projection data collection
The number of projection data output from the DAS 26 in the X-ray CT apparatus is m (600), but the number of projection data output from the DAS 26 in the X-ray CT apparatus equipped with the multi-line type X-ray detector 25 is m. × n (2400), and the number of projection data output from the DAS 26 is greatly increased as compared with the X-ray CT apparatus equipped with the single-line type X-ray detector 24. As the number of divisions in the SL direction increases, the number increases accordingly.

Since the conventional apparatus has a configuration in which the output data from the DAS 26 is sent out to the transmission paths 28 and 40 as it is, the X-ray C with the multi-line type X-ray detector 25 is mounted.
The T device needs to increase the data transmission capacity of the transmission paths 28 and 40 for transmitting the projection data output from the DAS 26, compared to the X-ray CT device equipped with the single-line type X-ray detector 25. In order to improve the data transmission capability of the rotation / fixed data transmission unit 28, there are technical difficulties, and due to the high cost, an X-ray CT apparatus equipped with a multi-line type X-ray detector 25 has However, there is a problem that the manufacturing cost is extremely higher than that of an X-ray CT apparatus equipped with a single-line type X-ray detector 25.

In the configuration of the conventional apparatus, all the collected projection data is temporarily stored in the memory 32. Therefore, the X-ray CT apparatus equipped with the multi-line type X-ray detector 25 has
With the large increase in the number of projection data output from the AS 26, it is necessary to increase the storage capacity of the memory 32, resulting in a further increase in cost.

The present invention has been made in view of such circumstances, and, without increasing the cost, collects projection data by dividing in the slice width direction and generates a tomographic image of the slice width before division. It is an object to provide an X-ray CT apparatus that can be obtained.

[0020]

The present invention has the following configuration to achieve the above object. That is, according to the present invention, the X-ray irradiating unit, the X-ray detector, and the data acquisition unit (DAS) are integrated while maintaining the facing state of the X-ray irradiating unit and the multi-line type X-ray detector. X-ray CT for reconstructing a tomographic image of a slice width before division based on the collected projection data based on the acquired projection data, which is obtained by dividing projection data from multiple directions around the subject in the slice width direction.
In the apparatus, first processing means for performing reconstruction processing of a tomographic image up to adding each absorption coefficient obtained from each acquired projection data in the slice width direction, and second processing for performing subsequent processing And the first processing means is configured to rotate integrally with the X-ray irradiating means, the X-ray detector, and the DAS.
The processing result of the processing means is transmitted to the second processing means via a transmission path.

[Operation] The operation of the present invention is as follows. In capturing a tomographic image, projection data from multiple directions around the subject is divided and collected in a slice width direction by an operation similar to that of a conventional X-ray CT apparatus equipped with a multi-line X-ray detector.

In the reconstruction processing of the tomographic image having the slice width before division, an offset is subtracted from each projection data,
An absorption coefficient is calculated from the calculation result, and each absorption coefficient is added in the slice width direction, and then an image reconstruction operation is performed.

In the present invention, of the reconstruction processing of the tomographic image, the processing up to adding each absorption coefficient obtained from each collected projection data in the slice width direction is performed by the first processing means. The result is transmitted to the second processing means via the transmission path, and the subsequent processing (image reconstruction calculation) is performed by the second processing means.

That is, since the output data from the first processing means (data sent to the transmission path) is data obtained by combining data divided in the slice width direction, the number of data is a single line type. And the number of data output from the DAS in the X-ray CT apparatus equipped with the X-ray detector.

Further, since the first processing means is configured to rotate integrally with the X-ray irradiating means, the X-ray detector and the DAS, the number of data transmitted from the rotating portion to the transmission path is as follows. This is the same as in the case of an X-ray CT apparatus equipped with a single-line type X-ray detector.

Therefore, the transmission capacity of the transmission path including the rotation / fixed data transmission unit and the storage capacity of the memory for temporarily storing data are different from those of an X-ray CT apparatus equipped with a single-line X-ray detector. Can be the same.

[0027]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a front view showing a configuration of a bed and a gantry part of an X-ray CT apparatus according to one embodiment of the present invention, FIG. 2 is a block diagram showing a configuration of a gantry and a console part of the embodiment apparatus, and FIG. FIG. 3 is a block diagram illustrating a configuration of a processor.

The X-ray CT apparatus according to this embodiment includes a bed 10, a gantry 20, a console 30, and the like.

The bed 10 has a bed base 11 that can be raised and lowered.
And a top 12, and a top 12 on which the subject M is mounted.
Is slidingly moved relative to the bed base 11 so that the subject M can be inserted into and removed from the opening 21 of the gantry 20.

In the gantry 20, an X-ray irradiating mechanism 24 corresponding to X-ray irradiating means comprising an X-ray tube 22 and an X-ray collimator 23, and a multi-line X-ray detecting device as shown in FIG. A device 25, a multi-line compatible data acquisition unit (DAS) 26, a rotating gantry 27, a first processing unit 1 corresponding to a first processing unit, and the like are provided. These devices 1,
Reference numerals 22 to 26 are attached to a rotary gantry 27 with the X-ray irradiating mechanism 24 and the X-ray detector 25 facing each other, and by rotating the rotary gantry 27, the X-ray irradiating mechanism 24 and the X-ray detector 25 are rotated. The X-ray irradiation mechanism 24, the X-ray detector 25, the DAS 26, and the first processor 1 are integrally rotated around the opening 21 (the subject M inserted into the opening 21) while maintaining the facing state of It is configured to be.

As described above, according to this apparatus configuration, the projection data of the subject M from multiple directions around the slice M can be sliced by the multi-line X-ray detector 25 and the multi-line compatible DAS 26. The data can be collected by dividing in the SL direction.

In the conventional apparatus, the projection data output from the DAS 26 is used as it is as the rotation / fixed data transmission unit 28.
In addition, in this embodiment, the projection data output from the DAS 26 is supplied to the first processor 1 to be transmitted to the fixed transmission cable 40.
To perform the processing described later, and the processing result (the first processing unit 1)
And the fixed transmission cable 4 for transmitting the data output from the
0 is transmitted.

The first processor 1 performs a calculation in the tomographic image reconstruction processing until the respective absorption coefficients obtained from the collected projection data are added in the slice width SL direction.

In the reconstruction processing of the tomographic image, offset subtraction is performed on each of the acquired projection data, an absorption coefficient is calculated from the result, and each absorption coefficient is added in the slice width direction. Therefore, it is necessary to calculate the absorption coefficient by offset subtraction or logarithmic calculation before adding each absorption coefficient in the slice width SL direction. Therefore,
As shown in FIG. 3, the first processor 1 is obtained by dividing in the slice width SL direction by an offset subtraction unit 2 that performs offset subtraction, an absorption coefficient calculation unit 3 that calculates an absorption coefficient by logarithmic calculation. An absorption coefficient adder 4 is provided for adding an absorption coefficient in the slice width SL direction for each channel Ch.

For example, as shown in FIG. 4, suppose that projection data obtained by dividing a certain channel Ch = i in the slice width SL direction is Iij (j = 1, 2,..., N). , Iij ′ = I
ij-OF (OF is an offset) is calculated, and the absorption coefficient calculation unit 3 calculates the absorption coefficient μij from Iij ′ by a well-known logarithmic calculation. Then, in the absorption coefficient adding unit 4, the absorption coefficient μ obtained by dividing in the slice width SL direction is obtained.
Calculate μi by adding i1 to μin.

The processing performed by the first processor 1 is only a relatively simple operation such as subtraction, logarithmic operation, and addition.
The first processor 1 can be composed of, for example, a subtraction circuit, a logarithmic operation circuit, an addition circuit, a memory, and the like.
And a memory. Note that the offset subtraction unit 2 holds an offset OF to be subtracted.

In the reconstruction processing of the tomographic image, the first processor 1
Image reconstruction calculations such as convolution conversion and back projection after the processing performed in step 2 are performed by the second processing unit 5 provided in the console 30 and corresponding to a second processing unit.

The second processing unit 5 includes a memory 32 for storing data transmitted from the transmission cable 40 (data output from the first processor 1), a processor 6 for performing image reconstruction calculation, and the like. ing.

With the above configuration, the multi-line type X-ray detector 25 and the multi-line compatible DA
With S26, the projection data of the subject M from multiple directions can be divided and collected in the slice width direction.
A tomographic image having a slice width before division can be obtained based on the projection data collected by the processor 1 and the second processing unit 5.

According to the configuration of the above embodiment, the first
The processor 1 performs an operation until at least each absorption coefficient obtained from each projection data is added in the slice width SL direction. Therefore, the output data from the first processor 1 (the absorption coefficient after addition) is the slice data. This is data obtained by combining data divided in the width SL direction, and the number of data is always the X-ray CT having the single-line type X-ray detector 25 irrespective of the number of divisions in the slice width SL direction. DAS2 with device
6 is the same as the number of data (projection data) output.

For example, if the number of channels Ch in the rotation direction of the X-ray detector 25 is m (for example, 600), the single-line X-ray detector 25 is mounted every time projection data is collected. The number of projection data output from the DAS 26 in the X-ray CT apparatus is m (600). On the other hand, in this embodiment, the number of data of the absorption coefficient μi output from the first processor 1 is m (600), and the single-line X
This is the same as the number of data output from the DAS 26 in the X-ray CT apparatus equipped with the line detector 25.

Further, the first processing unit 1 is
To rotate integrally with the X-ray irradiation mechanism 24, the X-ray detector 25 and the DAS 26, so that the number of data transmitted from the rotating part to the transmission paths 28 and 40 is a single line. It is the same as the case of the X-ray CT apparatus equipped with the X-ray detector 25 of the type.

Therefore, the transmission capacity of the transmission paths 28 and 40 including the rotation / fixed data transmission unit 28 can be made the same as that of the X-ray CT apparatus equipped with the single-line type X-ray detector 25. Further, the number of data once stored in the memory 32 is the same as that of the X-ray having the single-line X-ray detector 25 mounted thereon.
Since the storage capacity of the memory 32 is the same as that of the X-ray CT apparatus,
It can be the same as a line CT apparatus. Accordingly, in order to realize an X-ray CT apparatus capable of collecting projection data divided in the slice width SL direction and obtaining a tomographic image of the slice width before division, the transmission capacity of the transmission paths 28 and 40 is increased or the memory capacity is increased. There is no need to increase the storage capacity of the T.32, and there is no increase in cost.

[0044]

As is apparent from the above description, according to the present invention, the projection data of the subject from multiple directions of rotation is divided and collected in the slice width direction, and the divided data is divided based on the collected projection data. In the X-ray CT apparatus that reconstructs a tomographic image having a slice width of, a process of reconstructing a tomographic image is performed until the respective absorption coefficients obtained from the collected projection data are added in the slice width direction. The first processing means and the second processing means for performing the subsequent processing are performed separately, and the first processing means is configured to rotate integrally with the X-ray irradiation means, the X-ray detector, and the DAS. Since the processing result of the processing unit is transmitted to the second processing unit via the transmission path, the transmission capability of the transmission path including the rotation / fixed data transmission unit,
The storage capacity of the memory for temporarily storing data can be made the same as that of an X-ray CT apparatus equipped with a single-line type X-ray detector. In order to realize an X-ray CT apparatus capable of obtaining a tomographic image having a slice width of, there is no need to increase the transmission capacity of a transmission path or increase the storage capacity of a memory. Therefore, an X-ray CT apparatus capable of acquiring projection data divided in the slice width direction and obtaining a tomographic image of the slice width before division can be realized at low cost.

[Brief description of the drawings]

FIG. 1 is a front view showing a configuration of a bed and a gantry portion of an X-ray CT apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a gantry and a console portion of the embodiment device.

FIG. 3 is a block diagram illustrating a configuration of a first processor.

FIG. 4 is a diagram for explaining a processing process in a first processor 1;

FIG. 5 is a block diagram showing a configuration of a gantry and a console portion of the conventional device.

FIG. 6 is a plan view showing a configuration of a single-line X-ray detector and a multi-line X-ray detector.

FIG. 7 is a diagram for explaining a problem of an X-ray CT apparatus equipped with a single-line X-ray detector.

[Explanation of symbols]

 1: first processing unit 5: second processing unit 24: X-ray irradiation mechanism 25: X-ray detector 26: DAS 27: rotating base 28: rotation / fixed data transmission unit 30: console 40: transmission cable M: cable Sample SL: Slice width

Claims (1)

    [Claims]
  1. An X-ray irradiating means, an X-ray detector, and a data acquisition unit (DAS) are integrally formed while maintaining a state in which an X-ray irradiating means and a multi-line type X-ray detector are opposed to each other. In an X-ray CT apparatus which rotates and collects projection data of a subject from multiple directions of rotation in a slice width direction and collects the slice data in a slice width direction, and reconstructs a tomographic image of a slice width before division based on the collected projection data, The image reconstruction processing is divided into a first processing means for performing processing until addition of each absorption coefficient obtained from each collected projection data in the slice width direction and a second processing means for performing subsequent processing. The first processing means is configured to rotate integrally with the X-ray irradiating means, the X-ray detector, and the DAS, and the processing result of the first processing means is transmitted via a transmission path. It is specially transmitted to the second processing means. X-ray CT device to be used as a reference.
JP11035998A 1999-02-15 1999-02-15 X-ray ct device Pending JP2000232977A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP11035998A JP2000232977A (en) 1999-02-15 1999-02-15 X-ray ct device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP11035998A JP2000232977A (en) 1999-02-15 1999-02-15 X-ray ct device

Publications (1)

Publication Number Publication Date
JP2000232977A true JP2000232977A (en) 2000-08-29

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
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Country Status (1)

Country Link
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6434214B1 (en) * 1999-01-11 2002-08-13 Hitachi Medical Corporation X-ray CT apparatus and X-ray imaging method
CN100381101C (en) * 2004-04-06 2008-04-16 东软飞利浦医疗设备系统有限责任公司 Method for determining effective section width of CT unit

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6434214B1 (en) * 1999-01-11 2002-08-13 Hitachi Medical Corporation X-ray CT apparatus and X-ray imaging method
CN100381101C (en) * 2004-04-06 2008-04-16 东软飞利浦医疗设备系统有限责任公司 Method for determining effective section width of CT unit

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