JP2011206098A - Radiation image capturing system - Google Patents

Abstract

In a radiographic imaging system for imaging a plurality of radiographic images for image reconstruction, the amount of data stored in a storage means is reduced and the time required for data storage is reduced.
An imaging unit including a radiation detector that irradiates a subject with radiation from a plurality of directions different from each other and captures a radiation image of the subject each time the irradiation is performed, and a plurality of sheets obtained by the imaging. In a radiographic imaging system for image reconstruction comprising a storage means 46 for storing image data carrying each radiographic image, an image relating to a partial region within the imaging range from image data G relating to one image. Means 43 for cutting out data GL; coordinate information acquisition means 43 for acquiring coordinate information indicating the position of the partial area in the imaging range; image data GL indicating the partial area; and coordinate information indicating the partial area. Are stored in the storage means 46 in association with each other.
[Selection] Figure 2

Description

  The present invention relates to a radiographic imaging system, and more particularly to a radiographic imaging system having a function of imaging a subject from a plurality of different directions in order to reconstruct a three-dimensional image or a tomographic image.

  Conventionally, for example, as disclosed in Patent Document 1, a subject is irradiated with radiation from a plurality of different directions, and a transmission radiation image of the subject is captured each time. Based on a plurality of pieces of radiation image information thus obtained, A radiation CT apparatus for reconstructing a three-dimensional image or a tomographic image of a subject is known. In this radiation CT apparatus, the two-dimensional radiation detector and the radiation source arranged opposite to the radiation detector are moved so as to rotate around the subject, and each time the rotational movement position is changed, for example, a cone beam-like shape is directed toward the subject. A radiation is irradiated, and the radiation that has passed through the subject at that time is detected by a two-dimensional radiation detector, and a plurality of radiation images are taken.

  For example, as shown in Patent Document 2, a radiation tomosynthesis apparatus that reconstructs a tomographic image or a three-dimensional image of a subject without moving the radiation detector is also known. In this radiation tomosynthesis apparatus, a radiation source facing a subject placed between a fixed two-dimensional radiation detector is moved along an arcuate trajectory, and each time the movement position changes, Radiation is emitted toward the object, and the radiation transmitted through the subject at that time is detected by the two-dimensional radiation detector, and a plurality of radiation images are taken.

  In the CT apparatus and tomosynthesis apparatus described above, after taking a large number of radiation images, a huge amount of image data indicating them is temporarily stored in a storage means, and then an image is based on the image data read from the storage means. Since reconstruction is performed, it takes a long time from photographing to completion of image reconstruction.

  Therefore, in Cited Document 1, only the image data related to a part of a plurality of photographed images is stored in the storage means so as to reduce the amount of data to be stored and the time required for data storage. Has been proposed. Also, cited document 3 proposes a technique for shortening the entire imaging time by changing imaging conditions for each imaging region when imaging a wide area including the heart using a radiation CT apparatus.

JP 2003-116842 A JP 2008-110098 A JP 2009-078126 A

  However, in the technique described in the cited document 1, no image data is stored at all for the radiation images other than the partial number of images in which the image data is stored. When a request for configuration occurs, there is a problem that the request cannot be met.

  Further, although the technique described in the cited document 3 can shorten the time required for photographing, it is impossible to reduce the amount of data to be stored and the time required for data storage.

  The present invention has been made in view of the above circumstances, and in a radiographic imaging system that captures a plurality of radiographic images for image reconstruction, it is possible to use all of the captured radiographic images for image reconstruction. In addition, an object is to sufficiently reduce the amount of data stored in the storage means and sufficiently reduce the time required for data storage.

A radiographic image capturing system according to the present invention includes:
An imaging unit that irradiates the subject with radiation from a plurality of directions different from each other, and captures a radiation image of the subject each time the irradiation is performed
In a radiographic imaging system for image reconstruction, comprising storage means for storing image data carrying each of a plurality of radiographic images obtained by this imaging,
Means for cutting out image data relating to a partial area within the imaging range from the image data relating to one image;
Coordinate information acquisition means for acquiring coordinate information indicating the position of the partial area in the imaging range;
Data storage control means for storing image data indicating the partial area and the coordinate information indicating the partial area in a storage means in association with each other is provided.

In the radiographic image capturing system of the present invention,
An area designating unit for designating the partial area so that a specific part in the subject is included with respect to a radiographic image obtained by irradiating the subject with radiation from one of the plurality of directions;
Display means for displaying a radiographic image captured by the imaging unit;
In the radiographic image displayed on the display means, input means for designating the partial region so as to include a desired region of interest;
Based on each radiation irradiation direction when these two radiographic images were imaged so that the partial region in the radiographic image different from the radiographic image in which the partial region was specified is included in the region of interest. It is desirable to further provide a region calculation means that is obtained by calculation.

  Further, the data storage control means is preferably configured to add the coordinate information to the extracted image data and store it in the storage means.

  Alternatively, the data storage control means may be configured to store the coordinate information in the storage means separately from the image data after associating with the information indicating the cut-out image data.

Furthermore, in the radiographic imaging system of the present invention,
On the basis of the image data relating to one image, there is provided means for extracting the outline of a specific part of the subject existing outside the partial area,
The data storage control unit is preferably configured to store the image data indicating the contour in the storage unit in association with the image data indicating the partial area and the coordinate information.

  In the radiographic image capturing system of the present invention, image data relating to a partial area within the imaging range is cut out from image data relating to one image, and image data indicating the partial area is stored in the storage means. Compared to the case where image data indicating all the imaging regions of a large number of radiographic images is stored in the storage means as in the conventional apparatus, the amount of data to be stored can be sufficiently reduced, and the time required for data storage can also be shortened. It becomes.

  Further, in the radiographic image capturing system of the present invention, the coordinate information indicating the partial area is stored in the storage unit in association with the image data indicating the partial area. By means of the coordinate information, it is possible to inform which part of the entire photographing area the image data indicating the partial area is carried. Thereby, the reconstruction means can perform image reconstruction from the image data indicating the partial area.

  The radiographic image capturing system according to the present invention does not thin out some of the captured radiographic images and store them in the storage means. Can be used for image reconstruction.

In the radiographic imaging system of the present invention,
An area designating unit for designating the partial area so that a specific part in the subject is included with respect to a radiographic image obtained by irradiating the subject with radiation from one of a plurality of directions;
Display means for displaying a radiographic image captured by the imaging unit;
In the radiographic image displayed on the display means, input means for designating the partial region so as to include a desired region of interest;
Based on each radiation irradiation direction when these two radiographic images were imaged so that the partial region in the radiographic image different from the radiographic image in which the partial region was specified is included in the region of interest. In the case where an area calculation means that is obtained by calculation is further provided, a radiation image is displayed on the display means, and an operation for designating a partial area by the input means is performed for one radiation image while observing the display image. For example, with respect to the remaining radiographic images, a partial region including the region of interest can be automatically obtained by arithmetic processing. If so, it will not take a long time to determine a partial region in each of a large number of radiographic images, and the time required from imaging to image reconstruction can be significantly reduced.

The schematic side view which shows CT apparatus provided with the radiographic imaging system by one Embodiment of this invention The block diagram which shows the structure in connection with the data processing of the said CT apparatus Schematic showing an example of a cutout region in a radiographic image Schematic showing an example of a specific part extracted in a radiographic image Schematic showing another example of the cutout region in the radiographic image Schematic which shows another example of the specific part extracted in a radiographic image Schematic front view showing a tomosynthesis apparatus to which the radiographic imaging system of the present invention can be applied.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration of a radiation CT apparatus 1 to which a radiographic imaging system 3 according to an embodiment of the present invention is applied. The radiographic imaging system 3 includes an imaging unit 2, an imaging unit driving unit 15 that rotates the imaging unit 2, an arm 20 that holds the imaging unit driving unit 15, an imaging table 22 that supports a subject P, and imaging radiation. A computer 30 that performs various processes on the image and an image display means 31 connected to the computer 30 are provided.

  The imaging unit 2 includes a radiation source 10 that emits conical (cone beam-like) radiation R, a radiation detector 11 that detects radiation R emitted from the radiation source 10 and transmitted through the subject P, a radiation source 10, and It comprises a C-arm 12 that holds the radiation detector 11. The C-arm 12 can be rotated 360 ° around the rotation axis C by the photographing unit driving means 15 fixed to the lower end of the arm 20. The arm 20 includes a movable portion 20a, and is held by a base portion 21 that is movably attached to the ceiling.

  The radiation source 10 and the radiation detector 11 are disposed to face each other with a predetermined distance therebetween with the rotation axis C interposed therebetween. The radiation detector 11 is composed of a radiation solid detector (so-called “Flat Panel Detector”: FPD) as an example, and a pixel which is a minimum unit for detecting the radiation R in a plane parallel to the radiation detection surface 11a. Are arranged in a two-dimensional matrix. This type of FPD is also described in detail in Patent Document 2 described above.

  The computer 30 includes a central processing unit (CPU) (not shown), storage means (storage device) such as an HDD or SSD, and input means 32 such as a mouse or a keyboard. The CPU performs a function of image reconstruction on a plurality of image signals obtained by continuous imaging to obtain a three-dimensional radiation CT image or tomographic image of the subject P, and the operation of the radiation source 10. It has functions for performing control, control of the detection operation of the radiation detector 11 and control of image signal reading operation, and rotational movement control of the imaging unit 2 by the imaging unit driving means 15.

  Hereinafter, the basic operation of the radiation CT apparatus 1 will be described. First, the subject P is laid on the imaging table 22, and the radiation source 10 and the radiation detector 11 are arranged at symmetrical positions with the rotational axis C being the approximate center of the subject P's body. Then, the photographing unit 2 is positioned. The photographing unit 2 is moved based on the operation of the computer 30 by the photographer.

  When photographing is started, the photographing unit 2 is rotated around the rotation axis C. Thus, the radiation source 10 is driven each time the imaging unit 2 is rotated and the angle formed by the radiation irradiation axis O of the radiation source 10 and the imaging table 22 (that is, the radiation irradiation direction with respect to the subject P) becomes a predetermined angle. The Thus, the radiation R emitted from the radiation source 10 and transmitted through the subject P enters the radiation detector 11. The radiation detector 11 outputs an image signal indicating the intensity of incident radiation in units of the pixels described above, that is, carrying a transmitted radiation image of the subject P.

  As described above, image signals indicating a plurality of radiographic images obtained by photographing the subject P from different directions are acquired. These image signals are input to the computer 30 and are stored / saved in the storage device after undergoing processing such as clipping processing described later.

  When the continuous imaging is completed, the CPU of the computer 30 performs an image reconstruction operation from the image signal stored in the storage device, generates a three-dimensional radiation CT image or a tomographic image, and displays these images as image display means. 31 is displayed.

  Next, the cutout process and related processes will be described. FIG. 2 schematically shows a configuration for performing these processes. In FIG. 2, the elements indicated as “XXX” in the computer 30 do not exist individually as hardware, but simply indicate the configuration for executing each process based on software. In addition, as an example, the imaging operation is performed every time the rotation angle of the imaging unit 2, that is, the rotation angle of the radiation source 10 and the radiation detector 11 is changed by 1 °, and the radiation source 10 and the radiation detector 11 are fully rotated. Assume that the angle is 360 °, and a total of 360 radiation images are captured in a series of imaging. However, the rotation angle between shooting operations, the total rotation angle, and the series of shots are not limited to the above values.

  At the time of capturing a series of radiographic images, the output of the radiation detector 11 is first input to the preprocessing unit 40, where it is processed into a predetermined standard digital image data G by undergoing processing such as amplification and A / D conversion. Next, the image data G is input to the writing / reading unit 41. Each time image data G for one radiation image is input, the writing / reading unit 41 temporarily stores it in the memory 42, adjusts the timing for processing to be described later, and stores the image data from the memory 42. G is read at any time and is input to the cutout unit 43 and the extraction unit 44.

  Here, in particular, when the image data G relates to the first radiographic image in the imaging order, the image data G is input from the writing / reading unit 41 to the image display means 31, and the radiographic image carried by the data is obtained. Reproduced and displayed on the image display means 31. FIG. 3 shows an example of the first radiographic image D1 in the imaging order. Here, a case where a chest image of the subject P is captured will be described as an example. The apparatus user observes this display image and designates a partial region L1 so that the region of interest (the lung field in this example) enters from the entire imaging region LT of the image. The designation of the partial area L1 is performed by operating the input means 32 such as a mouse or a keyboard. Information dL indicating the designated partial region L1 is input to the cutout unit 43.

In the present example, the partial area L1 is a quadrilateral as shown in FIG. 3, and similarly, a two-dimensional xy coordinate system with one corner of the entire imaging area LT being a quadrilateral as the origin (0, 0). , The coordinates (x ₁ , y ₁ ) and (x ₂ , y ₂ ) of the two diagonal points are specified.

  Based on the input information dL, the cutout unit 43 cuts out image data for only a partial region L1 indicated by the information dL from the image data G, and sends the cut out image data GL to the data storage control unit 45. input. At this time, information dL indicating the partial region L1 is also input to the data storage control unit 45 together with the image data GL. As described above, in the present embodiment, the cutting unit 43 also serves as a means for acquiring coordinate information.

At this time, if there is a specific part H that is considered necessary to be displayed later together with the region of interest, such as a specific organ, for example, the device user points to a point in the specific part H, for example. Specify part H. Information dS indicating the coordinates (x ₃ , y ₃ ) of the point pointed in this way is input to the extraction unit 44.

  On the other hand, the extraction unit 44 extracts the outline (outline) of the region including the coordinate point indicated by the information dS from the image data G based on the input information dS. This contour extraction can be performed by applying a conventionally known edge detection technique. FIG. 4 shows an example of the contour HR1 extracted in this way. Then, the extraction unit 44 inputs the image data GH indicating the contour HR1 to the data storage control unit 45.

  The data storage control unit 45 attaches the input information dL and information indicating the first shooting order to the image data GL as a tag, and stores the clipped image data GL ′ with the tag in the storage device 46. Further, the data storage control unit 45 attaches information indicating the first photographing order to the input image data GH as a tag, and causes the storage device 46 to store the tagged contour image data GH ′.

  As described above, the storage device 46 stores and saves the data related to the first radiographic image in the imaging order. However, the storage and storage of the data related to the second to 360th radiographic images in the imaging order are basically the same. Made. However, in those cases, the reproduction display of the radiation image by the image display means 31 and the operation of designating the partial region L1 and the specific part H by the input means 32 are not performed, and the designation is performed by the cutout unit 43 and the extraction unit 44, respectively. Made automatically.

  Hereinafter, the automatic designation will be described in detail. FIG. 3 shows a partial region L1 in the first radiographic image D1 in the imaging order. The region of interest (the lung field in this example) within that region changes to the subject P every time the imaging sequence changes. Each time the direction of radiation irradiation changes, the position in the entire imaging region LT changes. For example, FIG. 5 shows the position occupied by the lung field in the n-th (n ≠ 1) imaging order Dn in the imaging order, which is different from the state shown in FIG. As described above, the position change characteristic of the region of interest corresponding to the radiation irradiation direction varies depending on the imaging region such as the chest and head of the human body and the imaging menu, but each change characteristic is obtained experimentally and empirically. be able to. The cutout unit 43 follows the region determination program based on the position change characteristics of the region of interest, which is determined for each imaging region and imaging menu, and from the partial region L1 in the first radiographic image, the nth radiographic image in the radiographic order. The partial region Ln at is calculated and obtained.

The partial area Ln obtained by this calculation is also defined by the coordinates (x ₁ , y ₁ ) and (x ₂ , y ₂ ) of the two diagonal points described above. At this time, it is necessary to know the angular relationship between the first radiation irradiation direction and the nth radiation irradiation direction in the imaging order, and the angular relationship can be known from the value of n. For example, in this example, if n = 30, the radiation irradiation direction at that time changes by (30-1) × 1 = 29 ° compared to the first case in the imaging order.

  The cutout unit 43 automatically obtains a partial region Ln (n = 2 to 360) in each of the radiographic images in the imaging order 2 to 360 as described above, and then the image data G carrying each radiographic image. To cut out image data GL for a partial region Ln. Subsequent processing is performed in the same manner as in the first radiographic image in the imaging order.

On the other hand, the position of the point (x ₃ , y ₃ ) in the specific portion H shown in FIG. 3 also changes each time the radiation irradiation direction to the subject P changes. Similarly, it can be determined experimentally and empirically. In accordance with the point position determination program based on the above-described change characteristics, which is determined for each imaging region or imaging menu, the extraction unit 44 determines the radiographic image in the nth radiographic order from the points in the specific portion H in the radiographic image that is the first radiographic image The point in the specific part H is calculated and obtained. The points obtained by this calculation are also defined by coordinates (x ₃ , y ₃ ) as described above. At this time, it is necessary to know the angular relationship between the first radiation irradiation direction and the nth radiation irradiation direction in the imaging order, and the angular relationship is obtained in the same manner as described above.

  The extraction unit 44 automatically obtains the position of the point in the specific portion H in each of the radiographic images in the imaging order 2 to 360 as described above, and then from this image data G carrying each radiographic image, this point The outline (outline) of the region including the image is extracted, and image data GH indicating the outline is created. FIG. 6 shows an example of the contour HRn extracted in this way. Subsequent processing is performed in the same manner as in the first radiographic image in the imaging order.

  As described above, in the storage device 46, the extracted image data GL ′ in which information indicating the imaging order and the extracted partial region Ln (n = 1 to 360) is attached as a tag for each of the 360 radiation images, and The contour image data GH ′ accompanied with information indicating the photographing order as a tag is stored and stored.

  After the radiographic image has been captured, the reconstruction processing unit 47 uses the cut-out image data GL ′ stored and stored in the storage device 46 to generate a three-dimensional CT image of the subject P or a tomogram indicating an arbitrary tomographic plane. The image is reconstructed and the image is displayed on the image display means 31. At the time of this reconstruction, it is necessary to know the position of the partial region Ln (n = 1 to 360) in the entire imaging region and the radiation irradiation direction at the time of imaging for each of the 360 extracted radiographic images. However, they can be obtained from the tag.

  As described above, in the present embodiment, the image data GL indicating the entire imaging region for 360 radiation images is not stored in the storage device 46, and an image indicating only a partial region Ln in the entire imaging region. Since the data GL ′ is stored, the amount of data stored in the storage device 46 can be sufficiently reduced, and the time required for data storage can be sufficiently shortened. If so, it is possible to apply a relatively low capacity storage device 46, and it is possible to perform processing from shooting of a subject to display of a reconstructed image within a short time.

  Further, since 360 image data are stored and stored for the portion including the region of interest, there is no inconvenience in the image reconstruction of the region of interest because the data storage amount is reduced.

  In the present embodiment, the image data GH ′ indicating the contour of the specific part H such as an organ is also stored and stored in the storage device 46 in association with the information indicating the radiographic image capturing order. When a request for displaying the location of the specific portion H together with the region of interest is generated later, the request can be met. The image data GH ′ indicating such an outline has a very small amount of data as compared with image data carrying a radiographic image showing the entire specific portion H. Therefore, even if this image data GH ′ is stored in the storage device 46, it is possible to avoid a significant increase in the capacity required for the storage device 46 and the time required for data storage processing.

In the above embodiment, the partial region Ln cut out from the entire radiation image is a quadrilateral, and the region is specified by the coordinates (x ₁ , y ₁ ) and (x ₂ , y ₂ ) of the two diagonal points. However, this partial area may have other shapes. For example, this partial region may be circular, and in that case, the region can be specified by the coordinates and radius of the center of the circle as an example.

  In the above embodiment, the positions of the points in the partial region Ln and the specific portion H are automatically obtained by calculation processing for the radiation images in the imaging order 2 to 360. Similarly to the first radiographic image, it may be designated by manual operation while referring to the display image. However, in order to increase the processing speed, it is desirable to eliminate the manual operation as much as possible and adopt the automatic processing as described above.

  In the above embodiment, the cut-out image data GL ′ is attached with information indicating the photographing order and the cut-out partial area Ln as a tag. The information indicating the partial area Ln is the cut-out image data GL ′. May be separately stored in the storage device 46 as a unique file in association with information for specifying the data (the information indicating the shooting order is one of them). In that case, the file may be stored in a storage means different from the storage device 46. The same applies to the image data GH ′ indicating the contour of the specific portion H.

  In addition to the information described above, information attached to the cutout image data GL ′ as a tag includes imaging information (the initial position of the radiation tube, swing angle, number of images), patient information (imaging site, patient individual information), etc. May be added. This is the same when no tag is used, and the imaging information and patient information may be recorded together in the above-described file.

  Although the radiographic imaging system applied to the radiation CT apparatus has been described above, the radiographic imaging system of the present invention can also be applied to configure the above-described radiographic tomosynthesis apparatus. FIG. 7 shows an example of such a radiation tomosynthesis apparatus. In this apparatus, the radiation source 10 is moved along an arcuate trajectory M centered on a point Q set in the subject P on the imaging table 22, and every time the movement position changes, that is, the radiation irradiation axis. A radiographic image is captured every time the angle formed by O and the imaging table 22 changes. Based on the plurality of radiographic images obtained in this way, a three-dimensional image or tomographic image of the subject P can be reconstructed.

  Also in such a radiation tomosynthesis apparatus, if only a partial region is cut out from each of a plurality of radiographic images taken, and only the image data carrying it is stored and stored in the storage means, the FIG. The effect obtained in the radiation CT apparatus 1 can be similarly obtained.

DESCRIPTION OF SYMBOLS 1 Radiation CT apparatus 2 Imaging part 3 Radiographic imaging system 10 Radiation source 11 Radiation detector 12 C arm 15 Imaging part drive means 22 Imaging stand 30 Computer 31 Image display means 32 Input means 43 Extraction part 44 Extraction part 45 Data storage control Unit 46 Storage device 47 Reconstruction processing unit H Specific portion in radiographic image Ln Partial region in radiographic image LT Total imaging region of radiographic image O Radiation irradiation axis R Radiation

Claims (5)

An imaging unit that irradiates the subject with radiation from a plurality of directions different from each other, and captures a radiation image of the subject each time the irradiation is performed
In a radiographic imaging system for image reconstruction, comprising storage means for storing image data carrying each of a plurality of radiographic images obtained by this imaging,
Means for cutting out image data relating to a partial area within the imaging range from the image data relating to one image;
Coordinate information acquisition means for acquiring coordinate information indicating the position of the partial area in the imaging range;
A radiographic imaging system comprising: a data storage control unit that stores image data indicating the partial region and the coordinate information indicating the partial region in a storage unit in association with each other. An area designating unit for designating the partial area so that a specific part in the subject is included with respect to a radiographic image obtained by irradiating the subject with radiation from one of the plurality of directions;
Display means for displaying a radiographic image captured by the imaging unit;
In the radiographic image displayed on the display means, input means for designating the partial region so as to include a desired region of interest;
Based on each radiation irradiation direction when these two radiographic images were imaged so that the partial region in the radiographic image different from the radiographic image in which the partial region was specified is included in the region of interest. The radiographic imaging system according to claim 1, further comprising an area calculation means that is obtained by calculation.   The radiographic image capturing system according to claim 1, wherein the data storage control unit adds the coordinate information to the extracted image data and stores the coordinate information in a storage unit.   2. The data storage control unit is configured to store the coordinate information in a storage unit separately from the image data after associating the coordinate information with information indicating the cut-out image data. Or the radiographic imaging system of 2. Means for extracting an outline of a specific portion of a subject existing outside the partial region based on the image data relating to one image;
2. The data storage control unit is configured to store image data indicating the contour in a storage unit in association with image data indicating the partial region and the coordinate information. The radiographic imaging system of any one of 1-4.

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