JPH0620487Y2 - X-ray tomography system - Google Patents

Description

[Detailed description of the device]

A. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray tomography apparatus, and particularly to a plane image (CR image) or a tomographic image (CT image) of an appropriate size according to each part of a subject to be imaged. Regarding the technology for displaying. B. 2. Description of the Related Art Since the size of each part of a subject, such as the head, chest, and abdomen, varies, the conventional X-ray tomography apparatus displays a CT image displayed on a CRT according to the size of each part. In order to make the CR image a proper size and make the image easy to see, the effective visual field area can be set. The effective field of view is the diameter of the tomographic image, for example, 160,210,250,300, ... mm
As described above, the setting is switched in about five steps, and for example, the diameter is set to 160 mm when the head is imaged, and the diameter is set to 300 mm when the abdomen is imaged. However, even with the same head, the size varies from person to person, so even if the effective visual field area is set as described above, it is not always possible to obtain an image of the optimum size for all subjects. . Therefore, in order to display an image in an appropriate size on the CRT, the conventional device is provided with a function of enlarging and displaying the image transferred to the CRT in addition to the above setting of the effective field of view. In this enlarged display, for example, as shown in FIG. 9, the operator designates the area to be enlarged in the image transferred to the screen B of the CRT with the circular cursor K, and the cursor K
For example, the image processing is performed by the computer so that the area surrounded by is expanded to the K'area. Usually, as the enlarged display, (a) so-called simple enlarged display in which the pixels between the pixels of the image already displayed on the CRT are enlarged and displayed is interpolated, and (b) projection data stored as detected is designated as enlarged. There is a so-called reconstructed magnified display that reconstructs and displays the area. According to the former enlarged display, the image is easy to see, but since the resolution itself does not change, new image information cannot be obtained. In other words, the enlarged portion causes "blur" in the image. On the other hand, according to the latter enlarged display, since the image is reconstructed, an image with improved spatial resolution can be obtained. C. Problems to be Solved by the Invention However, with any of the above-mentioned enlarged displays,
Since the image of the subject is once displayed on the CRT, the enlarged area is designated, and then the image enlarged by the computer processing is displayed, it takes a considerable time to obtain the enlarged image, and the patient processing is performed. There is a problem that it is one of the causes of lowering the ability. The present invention has been made in view of such circumstances, and provides an X-ray tomography apparatus capable of promptly obtaining an image of an optimum size according to the size of each part being imaged. It is intended to be provided. D. Means for Solving the Problems This invention has the following configuration in order to achieve the above object. That is, the X-ray tomography apparatus according to the present invention includes a data acquisition unit that amplifies a signal from the X-ray detector and converts it into digital data (projection data), and projection data provided from the data acquisition unit. Stored in a buffer memory, and from the right end and the left end of the required projection data of the projection data toward the center of the X-ray irradiation region, sequentially compare the detected data with a predetermined reference value, and obtain the reference value. A first data processing unit that detects an area between both crossed data areas as an effective data area, and projection data in the effective data area based on the projection data and the effective data area provided from the first data processing unit. It is provided with a second data processing section which is appropriately associated with the image composition memory and an image display section which displays the contents of the image composition memory. E. According to the present invention, the effective data area is detected for the actually obtained projection data, and the projection data in the effective data area is displayed as an image based on being appropriately allocated to the image forming memory. The display of the display is effectively used regardless of the size of the region of the subject. F. Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic block diagram showing the configuration of an embodiment of the present invention. In the figure, reference numeral S is a subject, and 11 is a fan-shaped X toward the subject S.
An X-ray tube for irradiating a X-ray beam, and an X-ray detector 12 for measuring the intensity of transmitted X-rays, for example, have a structure in which about 500 X-ray detectors are arranged in an arc shape. The X-ray tube 11 and the X-ray detector 12 are configured to be rotatable around the subject S. The signal detected by each X-ray detector 12 is given to the data acquisition unit 13. The data acquisition unit 13 amplifies the signal to an appropriate level and converts it into digital data (projection data). This projection data is sent to the first data processing unit 14. The first data processing unit 14 includes a microcomputer 15 and a buffer memory 16, stores the projection data sequentially sent from the data collection unit 13 in the buffer memory 16, and is effective for the required projection data of each projection data. It has a function to detect the data area. This function will be described in detail later. The projection data processed by the first data processing unit 14 is given to the second data processing unit 17, where an image is formed. Second
The data processing unit 17 includes a microcomputer 18 that controls the image configuration and an image configuration memory 19. The image data formed in the image forming memory 19 is given to the image display unit 20. This image display unit 20 is a video memory
21, a memory controller 22, a CRT 23 and the like. Reference numeral 24 is a host computer for controlling data exchange between the above-mentioned respective parts of the apparatus. Next, the operation of the X-ray tomography apparatus described above will be described. This type of X-ray tomography apparatus uses a CR image and CT of the subject S.
It has a function of capturing an image, and normally, a CR image is captured before capturing a CT image, positioning for tomography is performed based on this CR image, and then the CT image is captured. . The enlarged image display according to the present invention is a CR image and a C image.
It is applied to any photographing of the T image. Hereinafter, the image display in the CR image shooting and the image display in the CT image shooting will be described respectively. First, image display in CR image shooting will be described. When a CR image is taken, the top plate 25 on which the subject S is lying on its back as shown in FIG. 2, for example, is pitch-fed by about 2 mm, and X-rays are emitted from the X-ray tube 11 at each position. The transmitted X-rays are detected by the X-ray detector 12. However, FIG. 2 shows a state in which the X-ray tube 11 and the X-ray detector 12 are pitch-fed for convenience of drawing. Now, (P _l ), ..., (P _j ), ...
It is assumed that X-rays are exposed at each position of (P _N ). 3 (P _l ), ..., (P _j ), ... (P _N ) show the profile of the transmitted X-ray at each position. The detection signal having such a profile is converted into digital projection data by the data collection unit 13 and stored in the buffer memory 16 of the first data processing unit 14. Then, for each projection data, the effective data area is detected as follows. Here, the valid data area means the following data area. As shown in FIG. 4, the projection data profile includes
A data region X _j (hereinafter referred to as a subject region) based on X-rays transmitted through the subject S and a region other than the subject region X _j based on X-rays transmitted through air or the top plate 25 (hereinafter,
Invalid area) exists. The subject region X _j is the subject S.
3 (P _l ), ..., (P
_j ), ... ( _PN ) have different values in each profile. The first data processing unit 14 detects the largest object area X _j from each profile and sets it as the effective data area X _MAX . Hereinafter, description will be given based on the flowchart shown in FIG. In step S1, the step feed position P _j and the effective data area X _MAX are initialized, and in step S2, the sampling position x _i of projection data is initialized as shown in FIG. The sampling interval of the projection data is, for example, 2 mm. Then, the deviation of the level _{D i} and D _{i + l} of the projection data in adjacent sampling positions _{x i} and _{x i + l | D i -D} i + l
| Is determined (step S3), and it is determined whether this deviation is larger than a predetermined reference value δ (step S3).
4). The reference value δ is the data level of the object area X _j ,
It is predetermined according to the difference from the data level of the other invalid area. When the X-rays do not pass through the subject S, the change width of the projection data is small, and therefore | D _i −D _{i + l} | <δ. If | D _i −D _{i + l} | <δ, the process proceeds to step S5, and the change width of data between the next sampling positions x _{i + l} and x _{i + 2} is determined. When the sampling position x _{i + l} on the right side of the two sampling positions x _i and x _{i + 1} comes to the object region X _j , | D _i −D _{i + l} |> δ is determined in step S4. It In this case, proceed to step S6, where x
The _i-1 is set to _{X L} (step S6). The The x x _i-1 instead of _i is set to X _L, the rising region of the profile as shown in FIG. 4 is consideration of a case slow, is to take the margin of the subject area X _i . When left position _{X L} of the object region _{X j} is determined, step S7
Then, the sampling position is set to the rightmost sampling position x _m in FIG. If the sampling position is set to the right end x _m , D _i −D
_il is calculated (step S8), and the change width of the projection data is confirmed by | D _i −D _il | <δ (step S8).
9), if the change width is small, the next sampling position x
_Then , the process proceeds to _il and x _i-2 (step S10), and similarly the change width of the data is confirmed. In the case of | D _i −D _il |> δ, x _{i + l} is set to X _R in order to secure a margin for the subject region X _i as in the case of _XL described above (step S11). In this way, the left and right positions X _L , X _{R of the} subject region X _i
When _determined, X L, the distance between _{X R | X} L -X _{R |} is calculated and this is the subject area _{X j} (step S12). Then, the process proceeds to step S13 to judge the magnitude relation between X _MAX and X _j . If X _j is larger, X _MAX is updated to X _j (step S14). Such processing is performed for each profile (P ₁ ) to (P _N ) and when the processing is completed for all profiles, the valid data area X _MAX at that time is output to the second data processing unit 17 (step S15). ~ Step S17). Second data processing unit 17 provided with valid data area X _MAX
As shown in FIG. 6, each projection data (P _l ) to (P _l )
_N ), the data in the effective data area X _MAX is sequentially allocated to the image forming memory 19. The image data of the image-forming memory 19 thus constructed is supplied to the image display unit 20, whereby the CRT 23
The CR image is displayed on the screen in the optimum size, in other words, in a large size in the entire visual field area of the screen. Next, image display in CT image capturing will be described. As is well known, when a CT image is taken, the X-ray tube 11 and the X-ray detector 12 are rotated 360 ° around the subject S, and a pulsed X-ray is irradiated several hundred times. , Projection data equal to the number of exposures is obtained. Usually the data collection department
The projection data sent from 13 to the first data processing unit 14 is stored in the buffer memory 16 and is sent to the second data processing unit 17 in real time each time, and back projection (back projection) is performed on the image composing memory 19. Projection). Therefore, in order to detect a valid data area X _MAX, all projection data from capture in the buffer memory 16, upon detecting the valid data area X _MAX, is inconvenient becomes long waiting time until the backprojection . By the way, in the subject (body) S, the subject region X _j
The maximum position is determined depending on the region to be imaged, for example, when the X-ray is emitted from the vertical direction on the chest and when the X-ray is emitted from the horizontal direction on the head. Therefore, in this embodiment, when measuring the chest, as shown in FIG. 7, the photographing is started from the position displaced by 5 ° in the counterclockwise direction with respect to the vertical direction, and the photographing is started from the photographing start position. The effective data area X _MAX is determined by the projection data obtained within the range of 10 °. On the other hand, when measuring the head, photographing is started in the horizontal direction, and the effective data area X _MAX is detected from the projection data obtained within a range of, for example, ± 5 ° with respect to the horizontal axis. The procedure for obtaining the effective data area X _MAX from each projection data obtained by the exposure of X-rays within the range described above is the same as the procedure described in FIG. 5, and therefore the description thereof is omitted here. When the valid data area X _MAX is detected, this data is sent to the second data processing unit 17, and the back projection is performed based on this. Hereinafter, description will be given with reference to FIG. In the figure, reference numeral 19 denotes a back projection image forming memory. Normally, the image forming memory 19 is composed of a 340 × 340 or 500 × 500 pixel matrix, but here, for convenience of explanation, a 6 × 6 pixel matrix is shown. Note that REF is a reference point that serves as a reference for selecting predetermined data from the projection data PD when performing back projection. Further, in the figure, X _o is the total length of the projection data PD determined according to the array length of the X-ray detector 12, and this value can be known in advance. X _MAX is an effective data area detected by the first data processing unit 14. Second data processing unit 17 provided with valid data area X _MAX
Determines how many mm the pixel pitch of the image forming memory 19 corresponds to based on this effective data area X _MAX . For example, the effective data area X _{MAX in the} 340 × 340 pixel matrix
If the back projection is for 340 mm projection data, the pixel pitch corresponds to 1 mm. The back projection uses the projection data PD corresponding to each pixel from the last pixel [35] to the first pixel in the image area.

It is executed by sequentially adding data toward [0]. At this time, the pointer value C for selecting the projection data PD corresponding to each pixel is obtained as follows. Setting of pointer reference value C ₀ The foot of a perpendicular line drawn from the center O of the image forming memory 19 to the profile of the projection data PD is made to coincide with the midpoint O ′ of the profile PD. Then, when the distance from the reference point REF to the perpendicular line drawn to the profile of the projection data PD and the head data of the profile is d, the pointer reference value C ₀
Is set as follows. C ₀ = d / ds Here, ds represents the sampling pitch of the projection data PD. Back projection from pixel [35] to [30] The pointer value C ₃₅ for designating the projection data PD to be written in the pixel [35] is set as follows. C ₃₅ = C ₀ + X X = P _cos θ / ds Here, P is a length corresponding to the pixel pitch according to the effective data area X _MAX , and θ is a profile angle. When the pointer value C ₃₅ is set, the projection data P at that point is set.
Write D to pixel [35]. The projection data PD designated by the following pointer value C ₃₄ is written in the pixel [34]. The projection data PD designated by the pointer values C _{33 to} C ₃₀ is written up to the pixel [30] below C ₃₄ = C ₃₅ + X. C ₃₃ = C ₃₄ + X C ₃₂ = C ₃₃ + X C ₃₁ = C ₃₂ + X C ₃₀ = C ₃₁ + X Back Projection to Pixel [29] Projection data PD to be written in pixel [29] is given by the following pointer value C ₂₉ . To be selected. D ₂₉ = D ₃₀ −Y Y = P _sin θ / ds Back projection from pixel [28] → [24] The projection data PD selected by the pointer values C _{28 to} C ₂₄ shown below are respectively written. _{C 28 = C 29 -X C 27} = C 28 -X C 26 = C 27 -X C 25 = C 26 -X C 24 = C 25 -X pointer value C ₂₃ showing backprojection then to pixel [23] The projection data PD selected by is written respectively. C ₂₃ = C ₂₄ -Y below Similarly pixel [23] →

The projection data PD corresponding to each is written in [0]. The back projection ends by executing the above processing for all the projection data PD obtained by the rotational scanning of 0 ° to 360 °. As a result, the projection data PD in the effective data area X _MAX is stored in the image composition memory 19.
Is back-projected to each pixel in the circular pixel area A shown in FIG. The image data obtained by the back projection to the image composition memory 19 is the image display unit described above.
It is sent to 20, and after being subjected to appropriate image processing, it is displayed on the CRT 23. As described above, since the projection data PD in the effective data area X _MAX is back-projected by effectively utilizing the pixel area of the image forming memory 19, the CT image has the optimum size on the screen of the CRT 23. Is displayed. As for the image processing when capturing a CT image, if the waiting time until the back projection is not a problem, the object region X _{j is set} for all projection data.
May be detected, and the valid data area X _MAX may be determined from the detected data. Further, the effective data area X _MAX may be detected based on the projection data obtained when the X-ray is emitted from the vertical direction and the horizontal direction. G. Effect of the Invention As is clear from the above description, the X-ray tomography apparatus according to the present invention detects the effective data area based on the projection data collected by irradiating the subject with X-rays,
Since the projection data in the effective data area is allocated to the pixel area of the image forming memory, the image of the optimum size is displayed on the display regardless of the size of the part of the subject. Further, according to this invention, it is not necessary to perform an operation of displaying an image of a subject on a display device and designating an enlarged display while observing the image, unlike the conventional device. Images can be obtained quickly. Further, according to this invention, it is not necessary to perform the operation of setting the effective visual field area before the image display as in the conventional apparatus, so that the operability of the X-ray tomography apparatus can be improved. Further, according to this invention, since the display image of the optimum size is obtained by allocating the projection data in the effective data area to the pixel area of the image composing memory, it is possible to realize the simple enlarged display of the conventional apparatus. It is possible to obtain a clear image without "blurring" of the display image based on simple interpolation.

[Brief description of drawings]

1 to 8 are explanatory views of an X-ray tomography apparatus according to an embodiment of the present invention, FIG. 1 is a schematic block diagram thereof, and FIG. 2 is an X-ray when a CR image is taken. Explanatory diagram of exposure, FIG. 3 is a profile of projection data at that time, FIG. 4 is an explanatory diagram of data sampling when detecting an effective data area, and FIG. 5 is a flowchart showing a procedure for detecting an effective data area. , FIG. 6 is an explanatory view of an image structure when obtaining a CR image, FIG. 7 is an explanatory view of an imaging start position when obtaining a CT image, and FIG. 8 is an explanatory view of a back projection when obtaining a CT image. is there. FIG. 9 is an explanatory diagram of a conventional device. S ... Subject, 11 ... X-ray tube 12 ... X-ray detector, 13 ... Data collection unit 14 ... First data processing unit 15 ... Microcomputer 16 ... Buffer memory 17 ... Second data Processing unit 18 ... Microcomputer 19 ... Image composition memory 20 ... Image display unit 23 ... CRT X _MAX ... Effective data area

Claims (1)

[Scope of utility model registration request] 1. A data acquisition section for amplifying a signal from an X-ray detector and converting it into digital data (projection data); projection data supplied from the data acquisition section; Of the required projection data among the data, the detected data and the predetermined reference value are sequentially compared from the right end and the left end toward the center of the X-ray irradiation area, and the area between both data neighborhoods exceeding the reference value. And a projection data in the valid data area based on the projection data and the valid data area provided from the first data processing section, as appropriate to the image reconstruction memory. An X-ray tomography apparatus comprising: a second data processing unit for turning on and an image display unit for displaying the contents of the image reconstruction memory.