JP5438895B2 - X-ray detector system and X-ray CT apparatus - Google Patents

Description

  The present invention relates to an X-ray detector system in which an X-ray detector and a data acquisition device for amplifying an analog signal obtained from the X-ray detector and converting it into a digital signal are integrated into a chip and the X-ray detector system. The present invention relates to an X-ray CT apparatus provided with a detector system.

  The X-ray CT apparatus includes an X-ray tube and an X-ray detector arranged so as to face each other with a subject interposed therebetween, and irradiates X-rays from the X-ray tube while rotating these around the subject, X-rays transmitted through the subject are detected by an X-ray detector and converted into an electrical signal. For example, about 1000 channels of X-ray detectors are arranged in a direction (channel direction) orthogonal to the body axis direction of the subject. The electrical signal converted by the X-ray detector reflects the intensity of the X-ray that has passed through the subject, and the data obtained by collecting around the subject once or half-round is reconstructed. Thus, a tomographic image in the rotation plane is formed and displayed.

  This X-ray CT apparatus shortens the imaging time by high-speed rotation of the X-ray tube and the X-ray detector, and moves the X-ray detector in the channel direction (direction orthogonal to the body axis direction of the subject) and the slice direction (subject). High definition is progressing by subdividing and arranging in two dimensions along the body axis direction of the specimen. As a two-dimensional X-ray detector, for example, one having about 1000 channels and 4 slices has been generally used, but recently, a multi-slice X-ray CT apparatus capable of simultaneous imaging of 16 slices or more has been put into practical use. It has become like this.

In such a multi-slice X-ray detector, the number of wires for detecting signals from, for example, a photodiode array for detecting X-rays is remarkably increased, and this signal line is accommodated in the chip of the photodiode array. There was a problem that it became difficult. Therefore, a through electrode is formed in a silicon wafer on which a photodiode element is formed, and the wiring on the silicon wafer and the wiring inside the substrate on which the photodiode array is placed are electrically connected through the through electrode. There has been proposed a multi-slice X-ray detector that reduces the number of wires for extracting signals from the photodiode array and enables simultaneous imaging of 16 slices or more (see, for example, Patent Document 1).
JP 2004-57507 A

  By the way, in the recent X-ray CT apparatus, the demand for simultaneous multi-slice imaging has further increased along with the increase in resolution, and the multi-slice X-ray detector, which has conventionally been about 16 to 40 slices, has been further increased in number of rows. For example, development of an X-ray CT apparatus equipped with a two-dimensional X-ray detector capable of simultaneous imaging of 256 slices has been planned. However, as the number of slices that can be simultaneously photographed increases, the size of the X-ray detector increases, making it difficult to manufacture, and there is a problem in that the yield decreases.

  Further, since it is difficult to manufacture an X-ray detector for 1000 channels on a single substrate, conventionally, n-channel, m-slice photodiodes or semiconductor detection elements 101 are formed as shown in FIG. The number of substrates 102 corresponding to a predetermined number of channels (for example, 1000 channels) is prepared, and as the X-ray detector 100 to be mounted on the X-ray CT apparatus, the necessary number of each substrate 102 is placed on the body axis of the subject. They are arranged in a circular arc shape in the orthogonal direction.

  Further, the X-ray detector 100 is connected to a subsequent data acquisition device (DAS) 200 via a flat cable 300. The DAS 200 is formed by a substrate 203 on which an integrating amplifier chip 201 and an analog / digital converter chip 202 are arranged. For example, the DAS 200 is configured by a number of substrates 203 corresponding to the substrate 102 of the X-ray detector 100, and each corresponding substrate. 102 and the substrate 203 are connected by a flat cable 300 via a connector (not shown).

  The X-ray detector 100 and the DAS 200 rotate at high speed around the subject, and there is a possibility that the flat cable 300 is pulled during the rotation and the connector is disconnected. Further, since the signal passing through the flat cable 300 is an analog signal, vibration during rotation is picked up as noise, which may adversely affect the reconstructed image.

  In addition, the semiconductor detection element 101 that forms the X-ray detector 100, the integration amplifier chip 201 and the analog / digital converter chip 202 that form the DAS 200, and the like are each manufactured by specialized manufacturers. Therefore, when these are used as the X-ray detector 100 or the DAS 200 of the X-ray CT apparatus, the semiconductor detector chip 101, the integrating amplifier chip 201, and the analog / digital converter chip 202 supplied from each specialized manufacturer are mounted. A process of connecting and assembling the placed substrates to each other is required, and it takes time to perform the work. Therefore, there is a demand for simplifying the manufacturing process and reducing the size of the completed product by mounting the semiconductor detection element chip 101, the integration amplifier chip 201, the analog / digital converter chip 202, and the like on one substrate. It was.

  The present invention has been made to solve such problems.

In order to solve the above-mentioned problem, the invention according to claim 1 is arranged in a two-dimensional array of a plurality of detection elements that convert X-rays directly or once into light and then indirectly convert them into electrical signals. An X-ray detection chip, an amplification chip for amplifying an electric signal from the detection element of the X-ray detection chip, an A / D conversion chip for converting the output of the amplification chip into a digital signal, the amplification chip, and the For at least one of the A / D conversion chips, a plurality of chips each including a smaller number of elements than the plurality of detection elements are provided so that the number of the plurality of detection elements is the same as the number of elements. and, the plurality of chips are formed respectively so as to be smaller than the area of the total area of the detection surface of the surface parallel to the detection surface for detecting the X-ray of the X-ray detection chip, the The line detection chip, the amplification chip, and the A / D conversion chip are stacked in this order so as to form a three-layer structure, and a connection means that electrically connects between them is connected to the A / D. An X-ray detector system comprising: a substrate mounted in electrical connection with a D conversion chip.

  According to a second aspect of the present invention, in the X-ray detector system according to the first aspect, the connecting means for sequentially electrically connecting the chips is a through electrode or wire bonding. To do.

  According to a third aspect of the present invention, in the X-ray detector system according to the first or second aspect, the amplification chip and the A / D conversion chip placed on the substrate are The number of chips is larger than that of the X-ray detection chip.

  According to a fourth aspect of the present invention, there is provided the X-ray detector system according to any one of the first to third aspects, wherein the X-ray detector system is a unit, and the channel direction and It is characterized in that a large X-ray detector system is obtained by combining a plurality of them in the slice direction.

According to the fifth aspect of the present invention, the X-ray irradiation means for irradiating the X-ray around the subject, and the X-ray irradiated by the X-ray irradiation means and transmitted through the subject directly or once. An X-ray detection chip in which detection elements that are converted into light and indirectly converted into electric signals are arranged two-dimensionally; an amplification chip that amplifies the electric signals from the detection elements of the X-ray detection chip; An A / D conversion chip for converting the output of the amplification chip into a digital signal, and at least one of the amplification chip and the A / D conversion chip each include a smaller number of elements than the plurality of detection elements. A plurality of chips are provided so that the number of the detection elements is the same as the number of the detection elements, and the plurality of chips are parallel to a detection surface for detecting the X-rays of the X-ray detection chip. Become The total area are respectively formed to be smaller than the area of the detection surface of the X-ray detection chip, overlaid so that three-layer structure in the order of the amplifier chip and the A / D conversion chip, between them An X-ray detector system comprising a connection means for electrically connecting the substrates and a substrate on which the substrate connected by the connection means is placed, and a plurality of combinations of the X-ray detector systems in the channel direction and / or the slice direction An X-ray CT apparatus comprising: an image reconstructing unit that forms a tomographic image of the subject based on data collected through the image.

  As shown in the section of the means for solving the above problems, according to the invention of each claim described in the claims of the present invention, the following effects can be obtained.

  According to the first aspect of the present invention, the amplifier and the A / D converter constituting the data acquisition device (DAS) are formed into chips, and the X-ray detector chip is overlapped on the chips, so that the conventional configuration is different. An X-ray detector system in which the X-ray detector and the data acquisition device (DAS) are integrated into one chip can be provided. As a result, the X-ray detector system can be made high definition, the manufacturing yield can be improved, and the manufacturing process can be simplified.

  According to the second aspect of the present invention, it is not necessary to connect the X-ray detector portion and the data acquisition device (DAS) portion with a cable, and the influence of noise can be greatly reduced.

  According to the invention described in claim 3, the entire X-ray detector system is reduced in size by reducing the data acquisition device (DAS) portion while increasing the X-ray detection portion and increasing the X-ray detection sensitivity. be able to.

  According to the invention described in claim 4, an X-ray detector system having a desired number of channels and slices can be easily configured by freely combining packaged X-ray detector systems.

  According to the invention described in claim 5, by appropriately combining the X-ray detector system, a tomographic image having a desired number of slices can be easily obtained with high definition and high image quality can be obtained by eliminating the influence of noise. An X-ray CT apparatus capable of obtaining a tomographic image can be provided, which can greatly contribute to the improvement of medical quality.

  Embodiments of an X-ray detector system and an X-ray CT apparatus including the X-ray detector system according to the present invention will be described below in detail with reference to FIGS.

  FIG. 1 is an external view showing a schematic configuration of an embodiment of an X-ray CT apparatus according to the present invention, and FIG. 2 is a schematic block diagram of the same.

  The X-ray CT apparatus includes a gantry 1, a bed 2 arranged on the front surface of the gantry 1, and a console 3 that operates the gantry 1 and the bed 2. An opening 4 serving as a photographing unit is provided at a substantially central portion of the gantry 1. A top plate 5 on which the subject is placed is provided on the upper surface of the bed 2. By the operation of the console 3, the height of the bed 2 is appropriately adjusted, and the top plate 5 is also slid to the gantry 1 side. Therefore, at the time of imaging, the subject is sent to the opening 4 of the gantry 1 while being placed on the top 5.

  On the console 3, an input device 6 and a monitor 7 including a keyboard, a pointing device such as a mouse, a trackball, and a joystick are disposed. The controller 3 stores a controller 20 described later.

  As shown in FIG. 2, the X-ray tube 11 and the X-ray detector system 12 face each other in the gantry 1 with the subject P placed on the top 5 and positioned in the opening 4. Are arranged as follows. The X-ray tube 11 and the X-ray detector system 12 are supported by a rotating unit 13 and can rotate continuously around the subject P. The rotation unit 13 is driven based on a drive control signal supplied from the control unit 20 by the rotation drive unit 14.

  A high voltage generator 16 is installed in the gantry 1. The high voltage generator 16 is connected to the X-ray tube 11 via a slip ring (not shown), and a tube current and tube supplied to the X-ray tube 11 based on an X-ray control signal supplied from the control unit 20. The voltage is determined and supplied at a predetermined timing to generate X-rays.

  The X-ray tube 11 emits cone-shaped X-rays, which are shaped into an X-ray beam of a required size using a slit (not shown) and irradiated onto the subject P. Although the details will be described later, the X-ray detector system 12 is integrated by stacking a main detector 12a and a data acquisition system (hereinafter referred to as DAS) 12b on a substrate such as a ceramic. Formed.

  The main detector 12a detects X-rays that have passed through the subject P, and the DAS 12b performs main detection based on a data collection control signal supplied from the control unit 20 at a timing related to the generation of X-rays. The measurement data reflecting the X-ray transmittance for each X-ray path obtained from the instrument 12a is collected. Therefore, the DAS 12b includes an integrator that temporally integrates the output from each X-ray detection element of the main detector 12a, an A / D converter that converts the output of the integrator into a digital signal, and the like. The output of the DAS 12b is supplied to the control unit 20, and an image reconstruction process (not shown) provided in the control unit 20 performs an image reconstruction process to form a tomographic image.

  The couch 2 is provided with a couch controller 15, and based on a couch control signal supplied from the controller 20, for example, the couchtop 5 is moved to a desired slice position by a predetermined amount or a predetermined scan is performed. Or move continuously over a range.

  Next, details of the X-ray detector system according to the present invention will be described with reference to FIGS. In these drawings, the same portions are denoted by the same reference numerals.

  As described above, the X-ray detector system 12 according to the present invention is formed by integrating the main detector 12a and the DAS 12b into chips, and stacking them on a substrate such as ceramic. The outline of the basic configuration is shown in FIG. 3A is a perspective view for explaining the structure of the X-ray detector system 12, and FIG. 3B is a side view.

  That is, the main detector 12a of the X-ray detector system 12 is an X-ray detection element of a type that converts X-rays into light once with a scintillator and further converts the light into electric signals with a photodiode, A semiconductor X-ray detection element of a type that converts to a signal is used. An array of n (for example, n = 24) of these X-ray detection elements in the channel direction and m (for example, m = 64) in the segment direction is formed on one chip. Therefore, X-rays that have passed through the subject P are detected by the n-channel, m-segment main detector 12a.

  Although not shown, a collimator for collimating X-rays incident on the main detector 12a is arranged on the X-ray input side of the main detector 12a. The chip of the main detector 12a is overlapped with the DAS 12b that is also chipped.

  The DAS 12b of the X-ray detector system 12 includes an integrator 12b1 that temporally integrates the output from each X-ray detection element of the main detector 12a, and an A / D converter 12b2 that converts the output of the integrator 12b1 into a digital signal. Are formed by superimposing those formed on one chip, and similarly to the main detector 12a, n (for example, n = 24) array in the channel direction and m (for example, m = 64) array in the segment direction This is formed in one chip. The DAS 12b including the integrator 12b1 and the A / D converter 12b2 is placed on a substrate 12c made of ceramic or the like. Further, the main detector 12a and the DAS 12b placed on the substrate 12c are combined into a single package including a collimator to constitute the X-ray detector system 12.

  Here, the thick arrows shown in FIG. 3 indicate the direction of signal flow in the X-ray detector system 12. That is, the output of the main detector 12a, which is converted into an electric signal by detecting X-rays, is amplified by the integrator 12b1, and the amplified signal is converted into a digital signal by the A / D converter 12b2, so that the signal flows. The direction is in the order of main detector 12a → integrator 12b1 → A / D converter 12b2. Therefore, along the signal flow, the corresponding elements of the main detector 12a, the integrator 12b1 and the A / D converter 12b2 are electrically connected to each other, and the last A / D converter 12b2 is formed on the substrate 12c. Connected to the terminal portion of the circuit pattern. For connection between these chips and the substrate 12c, signals are sequentially transmitted directly under each chip by through electrodes (hole and via) formed for each element on the silicon wafer of each chip. it can.

  The outline of the connection method between the chips using the through electrode will be described with reference to FIG. FIG. 4 is an enlarged side sectional view showing only a part of the integrator 12b1 and the A / D converter 12b2 as an example. That is, an integrator element 12b12 is formed at a predetermined position on the upper surface of the silicon wafer 12b11 constituting the integrator 12b1, and a through electrode 12b13 corresponding to each integrator element 12b12 is formed at a predetermined position on the silicon wafer 12b11. Has been. Further, a bump 12b14 is provided on the back side of the silicon wafer 12b11 for each through electrode 12b13.

  On the other hand, the A / D converter 12b2 to be positioned under the integrator 12b1 similarly has an A / D converter element 12b22 formed at a predetermined position on the upper surface of the silicon wafer 12b21 constituting the A / D converter 12b2. In addition, a through electrode 12b23 corresponding to each A / D converter element 12b22 is formed in a predetermined position in the silicon wafer 12b21, and a bump 12b24 is provided on the back side of the silicon wafer 12b21 for each through electrode 12b23.

  Then, by placing the integrator 12b1 on the A / D converter 12b2, the bumps 12b14 on the back surface side of the silicon wafer 12b11 constituting the integrator 12b1 are formed on the silicon wafer 12b21 constituting the A / D converter 12b2. It is in contact with and electrically connected to the input terminal of the A / D converter element 12b22 on the upper surface. Similarly, by placing the A / D converter 12b2 on the substrate 12c, the bumps 12b24 on the back side of the silicon wafer 12b21 constituting the A / D converter 12b2 are formed on the terminal portions 12c1 of the circuit pattern formed on the substrate 12c. Touch and be electrically connected.

  Similarly, the chip constituting the main detector 12a is overlapped and connected to the chip of the integrator 12b1, and the main detector 12a and the DAS 12b are integrated.

  In this way, for example, a rectangular X-ray detector system 12 in which a chip-formed 24-channel, 64-segment main detector 12a and DAS 12b are stacked on the substrate 12c is formed as one package. Therefore, with such an X-ray detector system 12 as one unit, it is as if tiles in the channel direction and the segment direction so that the predetermined number of channels N (for example, N = 1000) and the number of slices M (for example, M = 256). The X-ray detector system in which the X-ray detector and the DAS are integrated at a high density can be realized.

  That is, the X-ray detector system 12 having n channels and m segments as one package is arranged in a plurality of circular arcs around the focal point of the X-ray tube 11 so as to form a desired N channel, and further By mounting this X-ray detector system on the X-ray CT apparatus so that a plurality of rows are arranged along the body axis direction of the subject to obtain a desired M slice, a large number of fine tomographic images can be obtained simultaneously. An X-ray CT apparatus is provided.

  In addition, this invention is not limited to said Example, It can implement with a various form.

  For example, as shown in FIG. 5, the corresponding elements of the main detector 12a, the integrator 12b1, and the A / D converter 12b2 are connected by a through electrode, and the last A / D converter 12b2 and the substrate 12c are connected to each other by a wire. You may make it connect using the method of bonding. 5 (a) is a perspective view similar to FIG. 3 (a), and FIG. 5 (b) is a side view similar to FIG. 3 (b). Reference numeral 12d in the figure denotes a wire bonding portion for circuit connection between the A / D converter 12b2 and the substrate 12c.

  The thick arrows in the figure indicate the signal flow in the X-ray detector system 12, and the signals flow downward through the through electrodes in the order of the main detector 12a → integrator 12b1 → A / D converter 12b2. It shows that the / D converter 12b2 flows to the substrate 12c in the horizontal direction (for example, the segment direction) by the wire bonding portion 12d.

  Further, as shown in FIG. 6, the corresponding elements of the main detector 12a, the integrator 12b1, and the A / D converter 12b2, and all of the A / D converter 12b2 and the substrate 12c are connected using the wire bonding portion 12d. You may make it connect. Here, FIG. 6 (a) is also a perspective view similar to FIG. 3 (a), and FIG. 6 (b) is a side view similar to FIG. 3 (b).

  Although the main detector 12a is desired to be as large as possible in order to increase the X-ray detection efficiency, the integrator 12b1 and the A / D converter 12b2 chips can be made considerably smaller than the main detector 12a chip. Therefore, the production yield can be increased accordingly. That is, when the chip of the main detector 12a is formed of, for example, 24 channels and 64 segments, the integrator 12b1 and the A / D converter 12b2 constituting the DAS 12b are respectively replaced with, for example, 12 channels and 32 segments. Thus, the number of elements may be halved, and two of them may be sandwiched between the substrate 12c and the main detector 12a to form a 24 channel, 64 segment DAS 12b.

  Several modifications of the X-ray detector system 12 based on this idea are shown in FIG. That is, FIG. 7A shows a single DAS 12b obtained by dividing the chip of the integrator 12b1 and the A / D converter 12b2 into a plurality of chips in a one-to-one correspondence with the main detector 12a of one chip. These are placed on the substrate 12c. Further, FIG. 7B shows a case where a plurality of A / D converters 12b2 chips are provided with one chip of the integrator 12b1 set to 2, and FIG. 7C shows a integrator 12b1. A plurality of chips of A / D converter 12b2 are provided so as to correspond to 2 for 1 chip. As means for connecting the chips, the means in each of the embodiments shown in FIGS. 3 to 6 can be adopted as appropriate.

It is the external view which showed schematic structure of one Example of the X-ray CT apparatus which concerns on this invention. 1 is a schematic block diagram of an embodiment of an X-ray CT apparatus according to the present invention. It is explanatory drawing which showed the outline of the fundamental structure of the X-ray detector system which concerns on this invention. It is explanatory drawing shown in order to demonstrate the outline of the connection method between chips | tips by a penetration electrode. It is explanatory drawing which showed the outline of the other embodiment of the X-ray detector system which concerns on this invention. It is explanatory drawing which showed the outline of the further another embodiment of the X-ray detector system which concerns on this invention. It is explanatory drawing which showed the modification of the X-ray detector system which concerns on this invention. It is explanatory drawing of the conventional X-ray detector and data acquisition apparatus which are mounted in X-ray CT apparatus.

Explanation of symbols

12 X-ray detector system 12a Main detector 12b Data acquisition device (DAS)
12b1 integrator 12b2 A / D converter 12c substrate

Claims (5)

An X-ray detection chip in which a plurality of detection elements that convert X-rays directly or once into light and then indirectly convert them into electrical signals are arranged in a two-dimensional manner;
An amplification chip for amplifying an electric signal from the detection element of the X-ray detection chip;
An A / D conversion chip for converting the output of the amplification chip into a digital signal;
For at least one of the amplification chip and the A / D conversion chip, a plurality of chips each including a smaller number of elements than the plurality of detection elements are equal in number to the plurality of detection elements. And the plurality of chips are arranged such that the total area of the surfaces parallel to the detection surface for detecting the X-rays of the X-ray detection chip is smaller than the area of the detection surface. is formed, and connecting means for the X-ray detection chip, overlaid so that three-layer structure in the order of the amplifier chip and the a / D conversion chip, electrically connected therebetween,
A substrate that is connected by the connection means and is placed in electrical connection with the A / D conversion chip; and
An X-ray detector system comprising:   The X-ray detector system according to claim 1, wherein the connection means for sequentially electrically connecting the chips is a through electrode or wire bonding.   The number of the amplification chips and A / D conversion chips mounted on the substrate is larger than that of the X-ray detection chip, according to any one of claims 1 and 2. X-ray detector system according to   4. The large X-ray detector system according to claim 1, wherein the X-ray detector system is a single unit, and a plurality of the X-ray detector systems are combined in a channel direction and / or a slice direction to form a large X-ray detector system. The X-ray detector system according to Item 1. X-ray irradiation means for irradiating an X-ray around the subject;
An X-ray detection chip in which X-rays irradiated by the X-ray irradiation means and transmitted through the subject are directly or once converted into light and then indirectly converted into electric signals are two-dimensionally arranged. When,
An amplification chip for amplifying an electric signal from the detection element of the X-ray detection chip;
An A / D conversion chip for converting the output of the amplification chip into a digital signal;
For at least one of the amplification chip and the A / D conversion chip, a plurality of chips each including a smaller number of elements than the plurality of detection elements are equal in number to the plurality of detection elements. And the plurality of chips are arranged such that the total area of the surfaces parallel to the detection surface for detecting the X-rays of the X-ray detection chip is smaller than the area of the detection surface. It is formed, and connecting means for the X-ray detection chip, overlaid so that three-layer structure in the order of the amplifier chip and the a / D conversion chip, connected between them electrically,
An X-ray detector system comprising a substrate on which a substrate connected by the connecting means is placed;
Image reconstructing means for forming a tomographic image of the subject based on data collected through a combination of a plurality of X-ray detector systems in the channel direction and / or slice direction;
An X-ray CT apparatus comprising:

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