JP4699780B2 - TR type computed tomography apparatus and radiation detection apparatus - Google Patents

Description

  The present invention relates to a TR computed tomography apparatus that collects three-dimensional data.

   In recent years, computer tomography scanners (hereinafter referred to as CT apparatuses) have been used in the field of industrial product development.

   Specifically, an aluminum casting, a ceramic product, or the like is displayed three-dimensionally using a CT apparatus and used for evaluation and analysis. In other words, a large number of cross-sectional images taken by the CT apparatus are converted into three-dimensional data and used for reverse engineering or digital engineering.

  By the way, this CT apparatus includes a Rotate / Rotate (RR) CT apparatus that obtains a cross-sectional image by scanning the subject one rotation relative to the radiation beam, and the subject relative to the radiation beam. There is a Translate / Rotate (TR) type CT apparatus that obtains a cross-sectional image by performing translation and step rotation.

  The RR type CT apparatus and the TR type CT apparatus are greatly different in the characteristics of scanning (hereinafter sometimes referred to as scanning) time and resolution.

  With respect to the scan time, the RR CT apparatus requires a short time because a cross-sectional image can be obtained by one scan. On the other hand, in the TR-type CT apparatus, since the parallel movement is performed several times so that the subject completely crosses the radiation, the scan time becomes long.

  Regarding the resolution, the RR CT apparatus takes a value determined by the channel pitch of the detector. On the other hand, in the TR CT apparatus, the data collection interval (pass interval) at the time of parallel scanning can be narrowed and does not depend on the channel pitch. As a result, in a configuration in which the RR-type CT apparatus and the TR-type CT apparatus obtain the same spatial resolution, the TR-type CT apparatus with a sufficient channel pitch is easier to take measures to reduce the incident scattered radiation, and the contrast and A cross-sectional image with good dimensional accuracy can be obtained.

  Due to such differences in characteristics, TR CT devices are often used in the industrial field (for example, see Non-Patent Document 1).

“Reverse Engineering Using CT Scanner”, M.M. Fujii, K .; Uyama, T .; Yamamoto, INTERMAC 2001 JOINT TECHNIC CONFERENCE, Nov. 9 (2001).

  By the way, the time required for the development of industrial products is greatly influenced by the quality and collection speed of three-dimensional data.

  However, in the conventional TR CT apparatus, it takes time to collect three-dimensional data. Therefore, there may be a delay in product development.

  An object of the present invention is to provide a TR CT apparatus capable of collecting high-quality three-dimensional data at high speed.

In order to solve the above problems, a TR computed tomography apparatus according to the present invention includes a radiation source for irradiating the subject with a fan-shaped radiation beam along an imaging surface for tomographic imaging of the subject, and the subject. A moving means for performing TR scanning combined with parallel movement along the imaging plane and rotation along the imaging plane relative to the specimen and the radiation beam, and movement perpendicular to the imaging plane; A post-collimator that changes the thickness of the radiation beam by narrowing the transmitted radiation beam in a direction perpendicular to the imaging surface, and a radiation beam focused by the post-collimator are arranged along the imaging surface. Detection means for detecting in the channel row of rows, and for each of the TR scans, based on the radiation beam individually detected in each of the two channel rows, A reconstruction means for creating a cross-sectional image ,
The detection means is disposed at a position facing the radiation beam, and separates the channel along the imaging surface for each channel and allows the radiation beam to pass. A channel collimator having a concave portion at a position along the imaging surface on the side surface, a planar column separator that is disposed at a position facing the injection side surface and that engages with the concave portion, and both surfaces of the column separator The two channel rows provided one by one,
The row separator is engaged with the recess so as to be integrated with the two channel rows so that the surface of the row separator coincides with the photographing surface, and is fixed to the channel collimator with a screw. .

  According to the present invention, it is possible to provide a TR type CT apparatus capable of collecting high-quality three-dimensional data at high speed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
FIG. 1 is a front view of a TR type CT apparatus according to the first embodiment of the present invention, and FIG. 2 is a plan view.

  The CT apparatus 10 is a TR CT apparatus that captures a cross-sectional image of the subject 5, and includes a radiation source 20, a mechanism unit 30, a radiation detection unit 40, and a data processing unit 50.

   Here, the radiation source 20 and the radiation detection unit 40 are arranged to face each other. Thereby, the radiation detection part 40 can detect the radiation beam which the subject 5 crossed.

  The radiation source 20 emits a fan-shaped X-ray beam 21B toward the radiation detection unit 40 along the imaging surface P on which the subject 5 is imaged. The X-ray tube 22 and the pre-collimators 23A and 23B are emitted from the radiation source 20. I have.

  The X-ray tube 22 emits a cone-shaped X-ray beam 21A in response to power supply and control from an X-ray control unit (not shown). The X-ray beam 21A is a cone-shaped beam having an apex angle of about 40 °.

  The pre-collimators 23A and 23B made of two plates are used to restrict the thickness of the X-ray beam 21A emitted from the X-ray tube 22. The X-ray beam 21A is focused on the fan-shaped X-ray beam 21B and irradiated on the subject 5. As a result, the subject 5 is not irradiated with useless X-rays.

   The mechanism unit 30 supports the radiation source 20, the radiation detection unit 40, the table 31 on which the subject 5 is placed, and the post-collimators 38 </ b> A and 38 </ b> B, respectively, and maintains the positional relationship of each part. The mechanism unit 30 includes a mechanism that rotates the table 31 with respect to the rotation axis C located at the center of the table 31 or translates the table 31 vertically and horizontally with the rotation axis.

  The table 31 is used to relatively move the placed subject 5 and the radiation source 20 by the mechanism unit 30. Specifically, the placed subject 5 is translated along the imaging plane P so as to cross the X-ray beam 21B (T direction in FIG. 2), or the subject 5 is orthogonal to the imaging plane P. Move up and down in the direction (Z direction in FIG. 1). In other words, the table 31 relatively translates the placed subject 5 and the X-ray beam 21 </ b> B in the direction along the imaging plane P and in the direction orthogonal to the imaging plane P. Further, the table 31 rotates the subject 5 around the rotation axis C at the center of the table.

   Thus, since the table 31 is translated or rotated in the vertical and horizontal directions, the imaging region of the subject 5 can be scanned with respect to the X-ray beam 22B.

   The X-ray beam 21B transmitted through the subject 5 is reduced in size in the direction orthogonal to the imaging plane P by post-collimators 38A and 38B made of two plates before entering the radiation detection unit 40. Thus, the X-ray beam 21C is obtained.

   The post collimators 38A and 38B have variable opening widths due to the mechanism of the mechanism section 30, and can change the slice thicknesses SWa and SWb simultaneously or individually. The slice thicknesses SWa and SWb can be set to 0.5, 1, 2, and 3 mm in steps, respectively.

  The radiation detection unit 40 detects a fan-shaped X-ray beam 21C emitted from the radiation source 20, as shown in FIGS.

   Here, FIG. 3 is an external perspective view of the radiation detection unit 40, FIG. 4A is a front view, FIG. 4B is an AA ′ sectional view, and FIG. 4C is a BB ′ section. FIG. 5A is an enlarged view of the recess 41A, FIG. 5B is a CC ′ sectional view, and FIG. 5C is a DD ′ sectional view.

   The radiation detection unit 40 is a collection of a large number of detector units 40A having the same structure arranged on a detector base 30A which is a part of the mechanism unit 30. However, in FIG. 3 to FIG. 5, only one detector unit 40 </ b> A is illustrated for ease of explanation. In addition, although the number of channels of the detector unit 40A is four, normally a larger number of channels is used. The detector unit 40A may be arranged in an arc shape around the focal point F of the radiation beam 21, or may be arranged in a straight line.

  As shown in FIG. 4A, the detector unit 40A includes an L-shaped unit base 49 installed on the detector base 30A, a channel collimator 41 attached to the unit base 49, and a channel collimator. 41, two channel rows 43 </ b> A and 43 </ b> B attached to the unit base 49 so as to be arranged behind the device base 49.

   The channel collimator 41 is disposed at a position facing the X-ray beam 21C, and has an exit side L on the side through which the X-ray beam 21C is emitted and has a recess 41A at a position along the imaging plane P. It is. A large number of channel collimators 41 are attached to the unit base 49 to form slits 41B.

  The slit 41B is a gap between the channel collimators 41 and is an X-ray path corresponding to each channel. The slits 41B are densely arranged on the unit base 49 so as to face the direction of the X-ray focal point F.

  The recess 41A is a portion that engages with the row separator 42 for alignment of the channel rows 43A and 43B. Thereby, the surface of the column separator 42 can be matched with the imaging surface P. The recess 41A is processed at the position (height h) of the imaging surface P of the channel collimator 41.

  The column separator 42 is a flat plate disposed at a position facing the injection side surface L so as to engage with the recess 41A. Here, a tungsten plate having a thickness of 0.2 mm is used. The surface of the column separator 42 is subjected to a reflection process for reflecting the light of the scintillator 44.

   The channel row 43A is obtained by adhering a light detection element row 45A to a scintillator block 44A, which is a row of scintillators 44, and one scintillator 44 and a corresponding light detection element form one X-ray detection channel. The channel row 43B has the same configuration. The channel rows 43A and 43B are provided along the imaging plane P via the row separator 42 (see FIGS. 4A and 4C).

  Thus, since there are two channel rows, two rows of data can be obtained along the imaging plane P over the fan angle θ0. The fan angle θ0 is a spread angle along the imaging plane P of the detected X-ray beam 21C.

  The scintillator blocks 44 </ b> A and 44 </ b> B are obtained by bonding a large number of scintillators 44 in rows on the upper and lower surfaces of one row separator 42. The scintillator blocks 44A and 44B are fixed to an L-shaped unit base 49 by a metal fitting 46A and a screw 46B via a lower light detection element array 45B.

   At this time, the positions of the scintillator blocks 44A and 44B are fixed so that the protruding portion of the column separator 42 is engaged with the recess 41A. As a result, the side surfaces of the scintillator blocks 44A and 44B and the side surface of the channel collimator 41 are arranged so that there is no step, so that the X-ray beam 21C that has passed through the slit 41B is accurately incident on the position where the scintillator 44 is arranged. Is done.

  A channel separator 47 is bonded between the scintillators 44. Further, between the scintillator 44 and the channel separator 47, there is a reflection layer (not shown) that reflects the light of the scintillator 44.

   The light detection element arrays 45A and 45B detect light when one element corresponds to one scintillator 44, and are provided on the upper surface of the scintillator block 44A and the lower surface of 44B. The X-ray beams 21C that have passed through the respective slits 41B of the channel collimator 41 cause the scintillator 44 to emit light, and the light emission of the scintillator blocks 44A and 44B is measured by the light detection element arrays 45A and 45B, respectively.

  The outputs of the photodetecting element arrays 45A and 45B undergo amplification, integration, multiplex, and digital conversion in a circuit portion (not shown) and are sent to the data processing unit 50.

  The data processing unit 50 and the display unit 51 are ordinary computers, and are configured by a CPU, a memory, a disk, a keyboard, various interfaces, and the like, and store software for controlling scanning, software for reconstructing a sectional image, and the like. .

   The data processing unit 50 processes the output of the radiation detection unit 40, gives a command to the mechanism unit 30 to control it, and forms a man-machine interface with the operator. By the output of the data processing unit 50, the display unit 51 displays the status of the apparatus, menu display, processing results, and the like.

   In addition, the data processing unit 50 processes and reconstructs transmission data of the subject 5 detected by the two channel rows 43A and 43B at a large number of positions in the TR scan that repeats parallel movement and stepwise rotation. Thus, it has a function of creating a cross-sectional image of the subject 5.

   Further, the data processing unit 50 has a function of controlling the vertical position of the table 31 so that a large number of continuous cross-sectional images can be obtained according to the slice thicknesses SWa and SWb changed by the post-collimators 38A and 38B. ing.

  Further, the data processing unit 50 has a function of issuing a command to an X-ray control unit (not shown) to start or stop the irradiation of the X-ray beam 21A from the X-ray beam 22.

(Operation of TR CT system)
The operation of the TR CT apparatus according to this embodiment will be described with reference to the flowchart of FIG.

  First, the operator places the subject 5 in the center of the table 31, adjusts the height of the table 31, and aligns the lower end of the imaging region of the subject 5 with the imaging plane P (S1). At this time, the data processing unit 50 sets the height of the table 31 according to the operator's vertical movement input (jog movement) (S1).

  Next, the operator inputs the slice thicknesses SWa and SWb and the height H of the imaging region to the data processing unit 50 (S2). Here, the openings of the post-collimators 38A and 38B are controlled by the data processing unit 50, the slice thicknesses SWa and SWb are set, and the imaging region height H is set (S2). For example, when the slice thickness is set to 1 mm, the openings of the post-collimators 38A and 38B are controlled by the data processing unit 50 so that the slice thickness SWa = SWb = 1 mm.

  Next, the data processing unit 50 waits for an operator scan start command (S3). When a scan start command is input, the data processing unit 50 starts irradiation with the X-ray beam 21A, controls the TR scan, and collects the output of the radiation detection unit 40.

  Here, the table 31 starts to translate, and during this translation, transmission data of the subject 5 is detected by the radiation detector 40 at a constant pitch and collected by the data processor 50 (S4). When the subject 5 crosses the X-ray beam 21C, the table 31 stops parallel movement.

   Subsequently, the table 31 rotates in one direction, for example, clockwise (CW) by the fan angle θ0 (S5). Then, parallel movement is started in the reverse direction, and transmission data is collected by the data processing unit 50. Similarly, when the subject 5 crosses the X-ray beam 21B, the table 31 stops parallel movement. The table 31 rotates clockwise by the fan angle θ0, and this operation is repeated K times. K is the smallest integer that satisfies θ0 · K ≧ 180 °.

  If the K translations are not completed, it is determined that the TR scan is not completed, and the table 31 continues to translate and rotate (S6-No).

  On the other hand, when the K translations have been completed, the data processing unit 50 has obtained data sets necessary for reconstructing the cross-sectional images from the two channel rows 43A and 43B. The cross-sectional image of the subject 5 is reconstructed by back projection (S6-Yes). As shown in FIG. 7, two cross-sectional images a1 and b1 having a slice thickness SW of 1 mm and a center interval of 1 mm are obtained as the cross-sectional images.

  Subsequently, when the cross-sectional image is obtained at a certain height in this way, the data processing unit 50 lowers the height of the table 31 by a height obtained by adding SWa and SWb (here, 2 mm) (S7).

  Thereafter, the same scan is performed. Thereby, as shown in FIG. 7, two cross-sectional images a2 and b2 are created.

  If the specified height is 2 Nmm, N sets of similar scans are performed. Here, if N scans are not performed, it is determined that necessary three-dimensional data cannot be obtained, the height of the table 31 is changed, and TR scan is continuously performed (S8-No). .

   On the other hand, when N sets of scans have been performed, it is determined that necessary three-dimensional data has been obtained, and the X-ray beam is stopped and the process is terminated (S8-Yes). Thereby, 2N cross-sectional images can be obtained with the centers separated by 1 mm.

   Then, the data processing unit 50 creates three-dimensional data based on these cross-sectional image data.

   Needless to say, if the designated height is H, the data processing unit 50 obtains the minimum integer N that satisfies N · (SWa + SWb) ≧ H, and controls to perform N scans. .

   As described above, according to the TR-type CT apparatus according to the present embodiment, the radiation detection unit 40 has the channel collimator 41 having the recess 41 </ b> A on the surface on the emission side of the radiation beam 21 along the imaging surface P of the radiation beam 21. A planar column separator 42 that is disposed at a position facing the emission side surface of the channel collimator 41, engages with the recess 41A, a scintillator block 44A provided on the upper surface of the column separator 42, and the column separator 42 A configuration including a scintillator block 44B provided on the lower surface, a light detection element array 45A provided on the upper surface of the scintillator block 44A, and a light detection element array 45B provided on the lower surface of the scintillator block 44B. Since two cross-sectional images are obtained by scanning, the cross-sectional images can be collected at high speed. Also, high-quality three-dimensional data can be created based on cross-sectional image data with very good dimensional accuracy according to the TR method.

   That is, it is possible to provide a TR CT apparatus that can collect high-quality three-dimensional data at high speed.

   Further, according to the invention according to this embodiment, the column separator 42 can be engaged with the recess 41 </ b> A of the channel collimator 41. Thereby, the end of the scintillator 44 can be accurately aligned with the imaging surface P. Further, the arrangement of each scintillator 44 and the arrangement of each channel collimator 41 can be made uniform, and the ratio of the X-ray beam 21C hitting the scintillator 44 can be increased. Therefore, the slice thicknesses SWa and SWb need not be increased more than necessary, and as a result, the slice thickness SW can be reduced.

Further, according to the invention according to the present embodiment, the scintillator blocks 44A and 44 are arranged in the direction perpendicular to the imaging plane P in the incident direction of the X-ray beam 21B and before the channel collimator 41.
With the configuration including post collimators 38A and 38B for changing the thickness of the X-ray beam 21B detected by B, the apertures of the post collimators 38A and 38B are controlled to control the slice thicknesses SWa,
SWb can be set arbitrarily. As a result, the slice thickness can be set in accordance with the accuracy in the Z direction required by the subject 5. For example, in the case of the subject 5 that gradually changes in the Z direction, the scan time can be shortened by increasing the slice thickness.

Further, the post-collimators 38A and 38B are located close to the radiation detection unit 40. Thereby, even if the position of the X-ray focal point F is unstable, the X-ray incident position on the scintillator 44 is hardly changed. That is, the positions of the post-collimators 38A and 38B are the same as the pre-collimator 2
Unlike the positions of 3A and 23B, the X-ray incident position does not change greatly due to the position fluctuation of the focal point F. Therefore, the output of the radiation detection unit 40 is not easily changed, and the slice thicknesses SWa and SWb do not need to be increased more than necessary. As a result, the slice thickness can be reduced.

  Furthermore, accurate three-dimensional data can be obtained by continuously obtaining a large number of cross-sectional images with good dimensional accuracy with thin slice thicknesses SWa and SWb. Needless to say, such three-dimensional data can be applied to digital engineering.

  Further, according to the invention of this embodiment, the photodetecting element arrays 45A and 45B are provided on the upper surface of the scintillator block 44A and the lower surface of 44B, respectively. Therefore, since the energy of the X-ray beam 21C that has not been captured by the scintillator is not directly received, a TR CT apparatus that can withstand long-term use can be provided.

(Modification of the first embodiment)
In the present embodiment, X-rays are used as radiation. However, the present invention is not limited to this, and it is needless to say that other transmissive radiations such as γ-rays may be used.

  In the present embodiment, the TR scan moves the subject 5, but the radiation source 20 and the radiation detection unit 40 may be moved as long as the movement is relatively the same. Further, for example, the parallel movement may be performed by the radiation source 20 and the radiation detection unit 40, and both may be moved by rotating the subject 5 by the table 31. Further, the table 31 may be raised and lowered by raising and lowering the radiation source 20 and the radiation detection unit 40.

  Further, the channel collimator 41 may be configured to be included in the radiation detection unit 40 as a whole, not included in each detector unit 40A. In this case, the channel collimator 41 for all the channels is attached on the detector base 30A, and the scintillator blocks 44A and 44B, the light detection element rows 45A and 45B, and the adhesive body of the metal fitting 46A are attached thereto.

  Further, when creating a cross-sectional image, three cross-sectional images may be created from one TR scan. That is, one cross-sectional image corresponding to an intermediate position can be created using one piece of data from the channel row 43A, one piece from the data of the channel row 43B, and two pieces of data. This third cross-sectional image is obtained by averaging the two data at the raw data stage and reconstructing it. Further, the third cross-sectional image can be obtained by averaging the two cross-sectional images.

  Furthermore, after creating three cross-sectional images a1, b1, and a1b1 in the first scan SC1, four cross-sectional images may be created after the second scan SC2. Specifically, as shown in FIG. 8, three images of cross-sectional images a2, b2, and a2b2 are created by the scan SC2, and the data obtained by the channel row 43B of the scan SC2 and the channel row 43A of the scan SC1 are obtained. A fourth cross-sectional image b2a1 is created from the data. Similarly, after the third scan SC3, four cross-sectional images are formed.

  Further, instead of creating two cross-sectional images in one scan, a single cross-sectional image may be created using both data of the channel row 43A and the channel row 43B.

  The slice thicknesses SWa and SWb are not necessarily set to the same value.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine a component suitably in different embodiment.

It is a front view of TR type CT apparatus concerning a 1st embodiment. It is a top view of TR type CT apparatus concerning the embodiment. It is an external appearance perspective view of the radiation detection part which concerns on the same embodiment. It is a front view of the radiation detection part which concerns on the same embodiment. It is an enlarged view of the recessed part which concerns on the same embodiment. It is a flowchart for demonstrating operation | movement of TR type CT apparatus which concerns on the same embodiment. It is a figure for demonstrating creation of the cross-sectional image which concerns on the same embodiment. It is a figure for demonstrating creation of the cross-sectional image which concerns on the same embodiment.

Explanation of symbols

    5 ... subject, 10 ... CT apparatus, 20 ... radiation source, 21A-C ... X-ray beam, 22 ... X-ray tube, 23A, 23B ... precollimator, 30. ..Mechanical part, 30A ... detector base, 31 ... table, 38A, 38B ... post collimator, 40 ... radiation detector, 40A ... detector unit, 41 ... channel collimator , 41A ... recess, 41B ... slit, 42 ... row separator, 43A, 43B ... channel row, 44 ... scintillator, 44A, 44B ... scintillator block, 45A, 45B ... Photodetector array, 46A ... metal fitting, 46B ... screw, 47 ... channel separator, 49 ... unit base, 50 ... data processing unit, 51 ... display unit, P ... Kagemen, L · · · exit-side surface, C · · · rotary shaft, .theta.0 · · · fan angle, SWa, SWb ··· slice thickness.

Claims (4)

A radiation source for irradiating the subject with a fan-shaped radiation beam along an imaging plane for tomographic imaging of the subject;
Moving means for performing TR scanning combined with parallel movement along the imaging surface and rotation along the imaging surface relative to the subject and the radiation beam, and movement perpendicular to the imaging surface;
A post-collimator that changes the thickness of the radiation beam by narrowing the radiation beam transmitted through the subject in a direction perpendicular to the imaging surface;
Detecting means for detecting the radiation beam focused by the post-collimator in two channel rows arranged along the imaging surface;
A TR- type computed tomography apparatus comprising: a reconstruction unit that creates two cross-sectional images of the subject based on radiation beams individually detected in each of the two channel rows for each TR scan ; There,
The detection means includes
The radiation beam is disposed at a position facing the radiation beam and separated for each channel along the imaging surface, and the radiation beam is allowed to pass therethrough. A channel collimator having a recess at a position along the imaging surface;
A planar column separator disposed at a position facing the injection side surface and engaged with the recess;
E Bei the channel row of the two rows arranged one column on each side of the column separator,
The row separator is engaged with the recess so as to be integrated with the two channel rows so that the surface of the row separator coincides with the photographing surface, and is fixed to the channel collimator with a screw. TR computer tomography system. In the TR type computed tomography apparatus according to claim 1 ,
The two channel rows are:
A first scintillator row provided on an upper surface of the row separator;
A first photodetecting element array provided on an upper surface of the first scintillator array;
A second scintillator row provided on the lower surface of the row separator;
A TR type computed tomography apparatus comprising: a second photodetecting element array provided on a lower surface of the second scintillator array. In the TR type computed tomography apparatus according to claim 1 or 2 ,
The moving means moves the subject and the radiation beam relatively perpendicularly to the imaging surface in accordance with the thickness of the radiation beam changed by the post-collimator. Shooting device. A detection device for detecting a fan-shaped radiation beam irradiated along a tomographic imaging surface used in a computer tomography apparatus,
The radiation beam is disposed at a position facing the radiation beam and separated for each channel along the imaging surface, and the radiation beam is allowed to pass therethrough. A channel collimator having a recess at a position along the imaging surface;
A planar column separator disposed at a position facing the injection side surface and engaged with the recess;
And two channel rows provided on each side of the row separator ,
The row separator is engaged with the recess so as to be integrated with the two channel rows so that the surface of the row separator coincides with the photographing surface, and is fixed to the channel collimator with a screw. Radiation detection device.

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