JP4504442B2 - X-ray diagnostic equipment - Google Patents

Description

The present invention relates to an X-ray diagnostic apparatus suitable for use in, for example, an X-ray diagnostic apparatus, and in particular, an X-ray flat detector is provided as an X-ray detection means, and the X-ray incident angle of the X-ray flat detector can be varied. As a result, various types of imaging such as tomography and rotational imaging can be performed with a single device without causing computation time and image quality degradation, and at any magnification while using an X-ray flat panel detector. The present invention relates to an X-ray diagnostic apparatus that enables imaging.

Conventionally, for example, an X-ray diagnostic apparatus for a circulatory device in which an X-ray source and an X-ray detector are provided at both ends of a C-arm having a substantially C-shape is known. In this X-ray diagnostic apparatus, it is possible to rotate the support shaft of the C arm around the support shaft that supports the C arm, and to rotate the C arm to slide along the shape of the C arm. Perspective photography in various directions and angles is possible.

An X-ray diagnostic apparatus in which an X-ray detector and an X-ray tube are attached to a bed that can be tilted is known as a device that is mainly used for diagnosis of the digestive system. This X-ray diagnostic apparatus is known for taking a tomographic image by performing X-ray imaging while moving the X-ray tube on an arc orbit or on a linear orbit parallel to the bed top.

The principle of tomography using this X-ray diagnostic apparatus will be explained. When the subject is fixed and the X-ray source and the X-ray film are moved parallel to the bed and in the opposite direction, any point on the specific cross section of the subject is always It will be projected onto a corresponding point on the X-ray film.
Draw a linear trajectory on the line film. As a result, on the X-ray film, an image obtained by adding the focused image of the specific section and the other blurred image is obtained. A tomographic image of a specific cross section in focus can be observed from this image. In order to observe a tomographic image of a cross section deviated from the specific cross section, the amount of movement of the X-ray film may be changed. For example, if you want to observe a cross section closer to the X-ray tube than the specific cross section, increase the amount of movement of the film. Conversely, if you want to observe a cross section closer to the X-ray film than the specific cross section, reduce the amount of movement of the film. good.

If the data acquisition system is an X-ray detector capable of high-speed and continuous data acquisition, the images at all positions can be stored as separate images (not summed like X-ray film). By shifting the image according to the position of the cross section to be configured and adding all the images, it is possible to reconstruct all the cross sections. This is the tomographic principle of the X-ray diagnostic apparatus.

However, in the conventional X-ray diagnostic apparatus, since the X-ray detector is restrained by the support portion of the C arm, the imaging mode is limited. For example, a circulatory X-ray diagnostic apparatus having a rotating arm as a support unit can only perform imaging at a predetermined angle or rotational imaging. For this reason,
Such a limitation has a problem of reducing the degree of freedom in clinical application of the designed imaging apparatus. That is, for example, in the case of a contrast examination of a coronary artery, an angle between the head side direction 55 degrees and the foot side direction 35 may be required. When trying to make such a deep angle, in the conventional X-ray diagnostic apparatus for a circulatory organ, a part of the detector comes into contact with the subject or the couch top, and the angle can be sufficiently deep. There wasn't.

Here, in the Japanese Patent Application Publication No. 9-109642, the above-described photographing is performed by converting a photographed digital image into a non-linear image by, for example, converting the photographed digital image into an image photographed by a tomographic apparatus. An imaging device has been proposed that solves the problem relating to the above degree of freedom.

However, this photographing apparatus performs non-linear transformation on the photographed digital image, so that the MT of the image is obtained.
In addition to the deterioration of F (spatial resolution), there is a problem that a very large number of arithmetic processing is required for nonlinear conversion and processing time is required.

That is, the digital image obtained by photographing is naturally sampled, but in order to perform the nonlinear conversion on this digital image, it must be sampled (resampling) again. In this resampling, sampling is performed again at a sampling pitch different from the sampling pitch when the digital image is formed, so that an aliasing error is likely to occur. Further, since no density value is recorded at the resampling point, an interpolation process is required to estimate the density value at the resampling point.
As a result, the MTF deteriorates.

In addition, for example, when obtaining a concentration value at one point in a rotary motion in which the X-ray tube and the X-ray detector rotate around one axis (rotation axis) by the rotation of the rotary arm, for example, nine addition operations ,
Four subtraction operations, 20 multiplication operations, and two division operations are required. In the non-linear transformation, it is necessary to perform each calculation for all pixels and all directions. For example, 1
When 70 captured images of 024 × 1024 [pixel2] are captured, it is necessary to perform the above-mentioned calculation “1024 × 1024 × 70” times in order to obtain the density values of all the images. For this reason, the nonlinear transformation requires a large amount of arithmetic processing and requires processing time. In addition,
This calculation number is an example when the X-ray tube and the X-ray detector perform a simple rotational motion. However, if the actual motion is a complex motion such as a conical motion, the amount of calculation In addition, the processing time is further increased.

The present invention has been made in view of the above-described problems, and causes a variety of imaging such as rotational imaging, digital tomographic image, three-dimensional reconstruction, and magnified imaging with one apparatus, causing deterioration in resolution and increase in calculation time. An object of the present invention is to provide an X-ray diagnostic apparatus that can be realized without any problem.

In order to solve the above-described problem, an X-ray diagnostic apparatus according to the present invention provides an X-ray generation means for exposing an X-ray to a subject, and an X-ray image transmitted through the subject as an electrical image. An X-ray flat panel detector that converts the signal, a C-shaped arm that supports the X-ray generator and the X-ray flat panel detector, and a support unit that rotatably supports the arm. The line plane detector is supported by the arm via an adjustment unit that adjusts the support angle of the X-ray plane detector, and the adjustment unit sets the support angle of the X-ray plane detector to the slide rotation of the arm. It can be adjusted around at least two axes of an axis parallel to the axis, an axis orthogonal to the slide rotation axis, or a diagonal line of the X-ray flat panel detector .

This enables various imaging such as rotational imaging, digital tomography, three-dimensional reconstruction, and the like with one apparatus, and enables imaging at a desired magnification by adjusting the X-ray incident angle. be able to.

In addition, discrete pixels in the imaging region can correspond to pixels formed by a solid X-ray detector. Therefore, a three-dimensional reconstructed image can be formed by affine transformation processing (enlargement, reduction, shift) and addition processing without performing nonlinear transformation processing on the captured digital image. Therefore, since the non-linear processing can be omitted in digital tomography and three-dimensional reconstruction, the calculation time can be shortened.

The X-ray diagnostic apparatus according to the present invention enables various imaging such as rotational imaging, tomographic imaging, three-dimensional reconstruction, and magnified imaging with one apparatus without causing deterioration in resolution and increase in calculation time. be able to. For this reason, the clinical value for the device can be improved.

Hereinafter, preferred embodiments of an X-ray diagnostic apparatus according to the present invention will be described in detail with reference to the drawings.

[First Embodiment]
The X-ray diagnostic apparatus according to the present invention can be applied to, for example, a single plane X-ray diagnostic apparatus as shown in FIGS. The X-ray diagnostic apparatus according to the first embodiment of the present invention includes a “fluoroscopy / imaging mode”, “subtraction imaging mode”, “tomographic imaging mode”, “reconstruction mode (no subtraction)”, “subtraction image” Total of 5 reconstruction modes ”
Although there are two imaging modes, if all the configuration requirements corresponding to each imaging mode are illustrated in one drawing, the drawing becomes complicated and difficult to understand. These are shown separately in FIG.

(Configuration corresponding to fluoroscopy and shooting modes)
First, the configuration corresponding to the fluoroscopic / imaging mode in this X-ray diagnostic apparatus is shown in FIGS.
As shown in FIG. 1, the bed 1 on which the subject is placed and the X provided on both ends of the C arm 4 respectively.
The X-ray flat panel detector 3, the X-ray flat panel detector 3, the contractible support 18 provided between the X-ray flat panel detector 3 and the C-arm 4, and the X-ray flat panel detector 3 are driven to rotate. And a detector rotating mechanism 6 for adjusting the incident angle of the line. The C-arm 4 is supported by a column 5 installed on the floor, and a holder 4a that supports the C-arm 4 so as to be slidable about the slide rotation axis is provided between the column 5 and the C-arm 4. Is provided. The holder 4a is attached to a support column 5 that is rotatably supported around a rotation axis orthogonal to the slide rotation axis. Further, the shrinkage support portion 18 is provided between the C arm 4 and the detector rotation mechanism 6.

Further, the X-ray diagnostic apparatus includes an A / D converter 7 that digitizes and outputs an analog imaging signal from the X-ray flat panel detector 3, and an imaging condition setting that mainly detects an X-ray irradiation angle and the like. Part 8;
An imaging condition memory 9 for storing data (imaging condition data) indicating imaging conditions detected by the imaging condition setting unit 8 and an imaging signal subjected to signal processing for fluoroscopic / imaging mode are converted into analog data, for example, a display unit 11 and the D / A converter 10 which supplies to etc.

Further, the X-ray diagnostic apparatus is for an image for temporarily storing an imaging signal digitized by the A / D converter 7 between signal lines connecting the A / D converter 7 and the D / A converter 10. Based on the imaging condition data stored in the memory 12 and the imaging condition memory 9 (according to the rotation angle of the X-ray flat panel detector 3), the geometry conversion process is performed on the imaging signal stored in the image memory 12. It includes a geometry conversion unit 13 that performs (trapezoid conversion processing) and an affine conversion unit 14 that performs affine conversion processing on the imaging signal that has been subjected to geometry conversion processing by the geometry conversion unit 13 and corrects distortion thereof.

Further, the X-ray diagnostic apparatus, for example, based on the imaging signal whose distortion has been corrected by the affine transformation unit 14 between the signal lines connecting the A / D converter 7 and the D / A converter 10, for example, Laplacian (two An edge emphasizing unit 15 for emphasizing an edge portion of the image by a second derivative operator) and a tone converting unit 16 for adjusting the brightness and sharpness of the image by adjusting, for example, contrast and brightness. .

(Configuration of X-ray flat panel detector 3)
As the X-ray flat panel detector 3, for example, vertical x horizontal pixels having a size of 4000 pixels x 4000 pixels are provided, and as shown in FIG. 5 , charges corresponding to the dose of incident X-rays are obtained. A solid X-ray sensitive element (X-ray detection element) comprising a plurality of pixels 21 to be formed and a plurality of thin film transistors 22 (TFTs) used as switches for reading out charges accumulated in the pixels 21 is arranged in the column direction and the row direction. They are arranged in a two-dimensional array in the direction.

Each pixel 21 is adapted to convert X-rays into visible light by a phosphor described later (phosphor 48 shown in FIG. 6). Photo that senses this visible light and forms charges according to the amount of incident light. It is composed of a diode and a capacitor (accumulation capacitor) for accumulating charges formed by the photodiode.

The connection point between the cathode terminal of the photodiode and one terminal of the storage capacitor is connected to a reverse bias power supply (-Vn) by a power supply line 25 (25-1, 25-2... 25-n). In addition, the connection point between the anode terminal of the photodiode and the other terminal of the storage capacitor is connected to the source terminal of the TFT 22.

The gate terminal of the TFT 22 is connected to each readout line 23 (23-1, 23-2... 23-n).
Are connected in common to each row and connected to each line output terminal of the line driving unit 24. The drain terminal of the TFT 22 is connected to a vertical transfer line 26 (26-1, 26-2...
26-n) is commonly connected to each column, and is connected to each switch 28-1, 28-2... 28-n of the multiplexer 28 via the lead-out amplifier 27.

More specifically, each X-ray detection element is composed of a pixel region 31 (PD: corresponding to the pixel 21) and a TFT region 32 (corresponding to the TFT 22) formed on the support 30 as shown in FIG. ing. On the support 30, a gate electrode 33 of the TFT 22 is formed, and an SiNx layer 34 is laminated thereon.

A polycrystalline silicon layer 35 (channel layer) is laminated on the SiNx layer 34 on the TFT region 32, and the n + a-Si layer 36 is sandwiched between both ends of the polycrystalline silicon layer 35 in FIG. A drain electrode 37 and a source electrode 38 are stacked. The TFT region 32 is covered with a first polyimide resin layer 44, and a metal electrode 45 that connects the transparent electrodes 43 in the pixel region 31 is laminated on the first polyimide resin layer 44. .

On the SiNx layer 34 on the pixel region 31, a transparent electrode 39 connected to the source electrode 38, an n + a-Si layer 40, an ia-Si layer 41, a p + a-Si layer 42, and the transparent electrode 4.
3 are laminated in order, thereby forming the photodiode having the Pin structure.

A second polyimide resin layer 46 is laminated on the metal electrode 45 in the TFT region 32 and the transparent electrode 43 in the pixel region 31, and a transparent protective film 47, a fluorescent layer is formed on the second polyimide resin layer 46. The body 48 and the light reflection layer 49 are sequentially laminated.

The X-ray flat panel detector 3 having such a configuration reflects visible light by the light reflecting layer 49,
Capture lines only. The phosphor 48 converts the captured X-rays into visible light. This visible light passes through the transparent protective film 47 and the second polyimide resin layer 46, and is further received by the pixel region 31 (photodiode) sensitive to visible light through the transparent electrode 43, and charges corresponding to the amount of light. It is said. This electric charge is accumulated in the accumulating capacitor, and is read out as an image signal pixel by pixel for each line via the readout line 23. The read image signal is proportional to the X-ray energy and is supplied to the A / D converter 7 shown in FIG. 1 via the multiplexer 28 and the output terminal 29.

(Operation in perspective and shooting mode)
Next, the operation of the fluoroscopic / imaging mode in the X-ray diagnostic apparatus of the embodiment will be described.

First, when performing imaging in the fluoroscopic / imaging mode, the operator operates the system console to capture an imaging angle (fluoroscopic angle), the number of X-ray exposures, an interval, a tube voltage, a detector viewpoint angle, and a contraction support unit 18. Input the shooting conditions such as the amount of contraction. The shooting condition data indicating the shooting conditions is temporarily stored in the shooting condition memory 9 via the shooting condition setting unit 8. When the imaging angle (perspective angle) is input from the operator, the imaging condition setting unit 8 supplies this to the detector rotation mechanism 6.

As shown in FIG. 7, the detector rotating mechanism 6 includes a motor 51, a power transmission unit 52, and a detector rotating unit 53. When the detector rotation angle is supplied from the imaging condition setting unit 8, the motor 51 is rotationally driven according to this, and the rotational force of the motor 51 is transmitted to the detector rotation mechanism 6 via the power transmission unit 52. . Thereby, the angle of the X-ray flat panel detector 3 with respect to the contraction support portion 18 and the C arm 4 can be changed according to the operation of the operator. The detector rotation mechanism 6 of the present embodiment is configured to rotate the X-ray flat panel detector 3 about an axis parallel to the slide rotation axis of the C arm 4 as shown in FIG. 13A. Yes. As shown in FIG. 13B, the X-ray flat panel detector 3 may be configured to rotate about an axis orthogonal to the slide rotation axis of the C arm 4 as a rotation axis. The X-ray flat panel detector 3 may be configured to rotate about two axes, an axis orthogonal to the rotation axis and an axis parallel to the slide rotation axis of the C arm 4. When the operator instructs to increase or decrease the contraction amount of the contraction support unit 18, the imaging condition setting unit 8 drives a motor (not shown) for the contraction support unit to change the contraction amount of the contraction support unit 18. .

Specifically, as shown in FIG. 8, the X-ray diagnostic apparatus using the C-arm 4 as a support as a support unit has an X-ray generation unit 2 and an X-ray plane as shown by a solid line in the drawing at the initial stage of imaging. The detector 3 is arranged in the vertical direction, and the X-ray flat detector 3 is opposed to the X-ray focal direction. In this state, when the C-arm 4 is rotated by an angle of θ degrees, the X-ray flat detector 3 always faces the X-ray focal direction as shown by a two-dot chain line in FIG. The shooting condition setting unit 8
The X-ray flat panel detector 3 is rotationally driven by the angle θ degree in accordance with the rotation angle of the C arm 4 based on the angle information detected by the above. Thereby, as indicated by the dotted line and the alternate long and short dash line in FIG. 8, the X-ray flat panel detector 3 can be controlled so as to always face the vertical direction regardless of the rotation angle of the C arm 4.

Next, X-ray exposure is performed after the X-ray flat panel detector 3 is rotationally driven. The X-ray exposure is performed so that a small dose of X-rays is continuously exposed during fluoroscopy, and a large dose of X-rays is intermittently exposed during imaging. The X-ray image formed by the X-ray exposure is captured by the X-ray flat panel detector 3 and supplied to the A / D converter 7 as an analog imaging signal. The A / D converter 7 digitizes this imaging signal and supplies it to the image memory 12. The image memory 12 temporarily stores this imaging signal.

Here, when the X-ray flat panel detector 3 is always directed in the X-ray focal direction as in the prior art,
Since the line is incident on the X-ray flat detector 3 substantially perpendicularly, the distance to the X-ray focal point is substantially the same at any position on the detection surface of the X-ray flat detector 3. As described above, when the X-ray flat panel detector 3 is rotationally driven so as to always face the vertical direction, X-rays are incident on the X-ray flat panel detector 3 at an angle. Depending on the position on the detection surface, there may be a large difference in the distance to the X-ray focal point, which may adversely affect the captured image.

For this reason, the geometry conversion unit 13 performs a trapezoid conversion process according to the shooting angle information stored in the shooting condition memory 9 on the image pickup signal stored in the image memory 12. That is, the geometry conversion unit 13 emits X-rays on the detection surface of the X-ray flat panel detector 3 from the imaging position information (imaging angle information and the contraction amount of the contraction support unit 18) stored in the imaging condition memory 9. The trapezoid area to be processed is obtained, and the image data of the trapezoid area is converted into rectangular image data.

Next, the affine transformation unit 14 performs, for example, image enlargement, reduction, inversion, translation processing, and the like on the imaging signal that has been subjected to the trapezoid transformation processing using the affine transformation processing (geometric transformation processing). Thus, each coordinate point is converted and distortion is corrected. The edge enhancement unit 15 enhances the edge portion of the captured image using a high frequency enhancement filter such as Laplacian (secondary differential operator), for example. Then, the gradation conversion unit 16 performs gradation correction (density correction) such as contrast and brightness on the coordinate-converted imaging signal, and supplies this to the D / A converter 10. The D / A converter 10 converts the imaging signal that has been digitally subjected to the above-described processing into an analog imaging signal, and supplies the analog imaging signal to the display unit 11, for example. Thereby, a fluoroscopic image or a captured image of a desired part of the subject can be displayed. Further, since the non-linear processing can be omitted at the time of digital tomography and three-dimensional reconstruction, the calculation time can be shortened. In addition, since the angle of the detector can be rotated by the detector rotating mechanism 6 when deep angling is performed, deeper angling can be performed than in the conventional X-ray diagnostic apparatus.

(Configuration corresponding to subtraction shooting mode)
Next, the configuration corresponding to the subtraction imaging mode in this X-ray diagnostic apparatus is shown in FIG.
In addition to the above-described bed 1 to gradation converting unit 16, a subtraction unit 55 that performs subtraction processing on a mask image stored in advance in the image memory 12 from a live image supplied from the A / D converter 7. It has composition which has.

(Operation in subtraction mode)
In this subtraction imaging mode, first, imaging is performed without injecting contrast medium into the subject, and image information obtained by this imaging is temporarily stored as a mask image in the image memory 12 in advance, and then the subject is contrasted. Injection is started and photography is started. A live image, which is image information obtained by imaging a contrast medium injected into the subject, is temporarily stored in the image memory 12.

The subtraction unit 55 reads out a live image from the image memory 12 and reads out a mask image corresponding to the live image from the image memory 12, and performs subtraction processing (D
A subtraction image is formed by performing SA (Digital Subtraction Angiography). That is, the subtraction unit 55 performs a subtraction process with the corresponding mask image while saving a live image obtained by photographing, and forms a subtraction image.

This subtraction image is subjected to trapezoid conversion processing, affine conversion processing, edge enhancement processing, and gradation conversion processing by the geometry conversion unit 13 to gradation conversion unit 16, respectively, and is converted into an analog form by the D / A converter 10 for display. Supplied to the unit 11. Accordingly, a subtraction image in which a desired part is clarified from the captured image can be displayed on the display unit 11. In addition, since the angle of the detector can be rotated by the detector rotating mechanism 6 when deep angling is performed, deeper angling can be performed than in the conventional X-ray diagnostic apparatus.

(Configuration corresponding to tomography mode)
Next, in the configuration corresponding to the tomography mode in this X-ray diagnostic apparatus, an imaging signal of a desired tomographic plane is added in addition to the bed 1 to image memory 12 and the affine transformation unit 14 as shown in FIG. It has the structure which has the addition part 56 processed.

The detector rotating mechanism 6 includes a motor 51, a power transmission unit 52, and a detector rotating unit 53 as shown in FIG. When the detector rotation angle is supplied from the imaging condition setting unit 8, the motor 51 is rotationally driven according to this, and the rotational force of the motor 51 is transmitted to the detector rotation mechanism 6 via the power transmission unit 52. . Thus, in accordance with the operator's operation, the angle of the X-ray flat panel detector 3 on the contraction support 18 and the C-arm 4 instead can Rukoto. The detector rotation mechanism 6 of the present embodiment is configured to rotate the X-ray flat panel detector 3 about an axis parallel to the slide rotation axis of the C arm 4 as shown in FIG. 13A. Yes. As shown in FIG. 13B, the X-ray flat panel detector 3 may be configured to rotate about an axis orthogonal to the slide rotation axis of the C arm 4 as a rotation axis. The X-ray flat panel detector 3 may be configured to rotate about two axes, an axis orthogonal to the rotation axis and an axis parallel to the slide rotation axis of the C arm 4. When the operator instructs to increase or decrease the contraction amount of the contraction support unit 18, the imaging condition setting unit 8 drives a motor (not shown) for the contraction support unit to change the contraction amount of the contraction support unit 18. .

Specifically, as shown in FIG. 8, the X-ray diagnostic apparatus using the C-arm 4 as a support as a support unit has an X-ray generation unit 2 and an X-ray plane as shown by a solid line in the drawing at the initial stage of imaging. The detector 3 is arranged in the vertical direction, and the X-ray flat detector 3 is opposed to the X-ray focal direction. In this state, when the C-arm 4 is rotated by an angle of θ degrees, the X-ray flat detector 3 always faces the X-ray focal direction as shown by a two-dot chain line in FIG. The shooting condition setting unit 8
The X-ray flat panel detector 3 is rotationally driven by the angle θ degree in accordance with the rotation angle of the C arm 4 based on the angle information detected by the above. As a result, as indicated by the dotted line and the alternate long and short dash line in FIG. 8, the X-ray flat panel detector 3 can be controlled so as to always face the vertical direction regardless of the rotation angle of the C arm 4.

(Operation in tomography mode)
In this tomography mode, for example, the C-arm 4 is controlled to rotate between −20 degrees and +20 degrees, and image information obtained by this imaging is temporarily stored in the image memory 12. Then, after image information during rotation control of the C-arm 4 between −20 degrees and +20 degrees is stored in the memory 14, an arbitrary tomographic plane is set by setting means (not shown). The affine transformation unit 14 performs affine transformation processing corresponding to the enlargement / reduction ratio and shift amount of each acquired image so that the set tomographic plane is focused on the image information read from the image memory 12, and Adder 5
6 is supplied. The adding unit 56 adds the images subjected to the affine transformation process to form a tomographic image of the set tomographic plane, and supplies this to the display unit 11 via the D / A converter 10. Thereby, a tomographic image at an arbitrary position can be displayed on the display unit 11. In addition, a tomographic image can be obtained at a relatively high speed with a circulatory X-ray diagnostic apparatus using a C-arm.

(Configuration corresponding to reconfiguration mode)
Next, the configuration corresponding to the reconstruction mode in this X-ray diagnostic apparatus is read from the image memory 12 in addition to the bed 1 to image memory 12 and the affine transformation unit 14 as shown in FIG. A filtering unit 57 that performs a predetermined filtering process on the imaging signal using, for example, a convolution filter, and a filtering coefficient variable unit 58 that variably controls the filter coefficient of the filtering unit 57 in accordance with shooting angle information stored in the shooting condition memory 9.
It has composition which has.

(Operation in reconfiguration mode)
First, when photographing a three-dimensional reconstruction image, image information for at least 180 degrees is required from the principle of three-dimensional reconstruction. On the other hand, since the X-ray diagnostic apparatus according to the present embodiment is a single plane as described above, the X-ray flat panel detector 3 is rotationally driven at the first 90 degrees as shown in FIG. . If an attempt is made to take the first 90 degrees or more, the angle with the X-ray focus direction of the X-ray flat detector 3 is too large, so that the data in the target range protrudes from the X-ray flat detector 3. For this reason, the X-ray diagnostic apparatus rotates the angle of the X-ray flat panel detector 3 by 90 degrees as shown in FIG. 9 at the time when the first 90 degrees imaging is completed, and the imaging at the first 90 degrees is performed. In the same manner as described above, the X-ray flat panel detector 3 is controlled so as to always face the direction perpendicular to the vertical direction regardless of the rotation angle of the C arm 4. Thereby, image information for 180 degrees required for three-dimensional reconstruction can be obtained.

Note that the rotational speed of the X-ray flat panel detector 3 is very slow relative to the image information collection speed. For this reason, the detection surface of the X-ray flat panel detector 3 is vertical, for example, from the state of FIG. 8 to the state of FIG. 9, the detection surface and the tomographic surface are not parallel. Only the image may be projected once on a plane parallel to the tomographic plane. During this time,
The image information may not be collected.

Here, in this reconstruction mode, there are provided two modes: a mode for executing a subtraction process for a captured image and a null image, and a mode for executing a subtraction process for a live image and a mask image.

(Mode for executing subtraction processing of captured image and null image)
In the case of this mode, first, a null indicating density unevenness of each X-ray prefecture detection element of the X-ray flat panel detector 3 obtained by performing imaging without placing anything on the bed 1 before imaging. An image is captured and stored in the image memory 12 in advance.

Next, as described above, the C-arm 4 is rotationally driven by 180 degrees, image information for each angle is taken as a photographed image, and these are stored in the image memory 12. The subtraction unit 55 performs a subtraction process between the null image and the captured image stored in the image memory 12 and supplies the subtraction image to the filtering unit 57.

Here, for example, the filtering unit 57 performs filtering on the subtraction image subjected to the subtraction processing using an appropriate convolution filter such as Shepp & Logan or Ramachandran in order to perform three-dimensional reconstruction by a so-called filtered back projection method. In the X-ray diagnostic apparatus, the detection surface of the X-ray flat panel detector 3 is controlled so as to be always parallel to the cross-section of the pixel arrangement in the imaging region during rotation, and image information is captured. To do. Even if the projection angle changes, when the filtering process is performed with a constant convolution filter, the width of the filter changes substantially depending on the angle (the more the angle of rotation of the X-ray flat panel detector 3 is inclined, the more the back projection is performed). The filtering width of the convolution filter at the time becomes small), which causes artifacts.

Therefore, the filtering coefficient variable unit 58 reads shooting angle information indicating the shooting angle of the subtraction image from the shooting condition memory 9, and variably controls the filter function (filter coefficient) of the filtering unit 57 according to the shooting angle. . Specifically, the filtering coefficient variable unit 58 sets q (t) as the filter function of the filtering unit 57 and θ as the shooting angle.
Based on the following mathematical formula, the filter function q1 corresponding to the photographing angle is set in the filtering unit 57.

q1 (t) = q (cos θ · t)
As a result, as shown in FIG. 10, the filter width of the convolution filter used in the filtering unit 57 can be variably controlled to the optimum filter width according to the rotation angle of the X-ray flat panel detector 3, and a three-dimensional reconstructed image can be obtained. It is possible to prevent inconvenience that artifacts occur.

Next, the subtraction image filtered by the filter coefficient variably controlled in this way is supplied to the image memory 12 and read by the affine transformation unit 14.
The affine transformation unit 14 performs an affine transformation process corresponding to the enlargement / reduction ratio of each image information and the shift amount so that the tomographic plane set by the operator is in focus.
Is applied to the subtraction image read out from, and this is supplied to the adder 56.

The adder 56 performs an addition process (back projection operation) on the subtraction image that has been subjected to the affine transformation process, thereby forming a reconstructed image of the set tomographic plane. Specifically, FIG.
1, the desired tomographic plane in the imaging region is H, the distance from this tomographic plane to the detection plane of the X-ray flat panel detector 3 is D, and the distance from this tomographic plane to the focal point of the X-ray generator 2 is L Then, the adding unit 56 adds the subtraction image multiplied by “L / (D + L)” to the desired tomographic plane H to form a reconstructed image of the desired tomographic plane H, which is converted into a D / A converter. 10 to the display unit 11. Thereby, it is possible to display the reconstructed image at an arbitrary position obtained by executing the subtraction process of the captured image and the null image while being an X-ray diagnostic apparatus on the display unit 11.

The reconstruction area (imaging area) is defined as a cylinder inscribed in the X-ray bundle in all directions of the X-ray generator 2. The inside of this cylinder is discretized three-dimensionally with the length at the center of the reconstruction area projected onto the width of one X-ray detection element of the X-ray flat panel detector 3, for example. It is necessary to obtain a reconstructed image of the data. However, this discrete interval is an example, and this may vary depending on the device or manufacturer. Therefore, basically, the discrete interval defined by the device may be used.

(Mode for executing subtraction processing between live image and mask image)
In this mode, the operator first takes an image without injecting a contrast medium into the subject, stores the image information obtained by the imaging as a mask image in the image memory 12 in advance, and then stores the image information on the subject. Imaging is started by injecting contrast medium. In addition, a live image that is image information obtained by imaging a contrast medium injected into the subject is temporarily stored in the image memory 12.

When the mask image and the live image, which are image information before and after the contrast medium injection, are stored in the image memory 12, the subtraction unit 55 performs both subtraction processes and supplies the subtraction image to the filtering unit 57. The filtering coefficient of the filtering unit 57 is varied according to the photographing angle by the filtering coefficient varying unit 58 as described above. The filtering unit 57 performs the filtering process of the subtraction image using the variable filtering coefficient, and supplies this to the affine transformation unit 14.

The affine transformation unit 14 performs affine transformation processing corresponding to the enlargement / reduction ratio of each image information and the shift amount so that the tomographic plane set by the operator is focused on the image memory 1.
2 is applied to the subtraction image read out from 2 and supplied to the adder 56. Adder 56
The adding unit 56 performs an addition process (back projection operation) on the subtraction image that has been subjected to the affine transformation process to form a reconstructed image of the set tomographic plane, which is converted into a D / A converter 10. To the display unit 11. As a result, a reconstructed image at an arbitrary position obtained by executing the subtraction process between the mask image and the live image can be displayed on the display unit 11 while being an X-ray diagnostic apparatus.

As is clear from the above description, the X-ray diagnostic apparatus of the first embodiment includes the C arm 4
The X-ray plane detector 3 is rotationally driven to adjust the X-ray incident angle so as to be parallel to the cross-section along the arrangement of the pixels in the reconstruction region regardless of the rotation angle of the image, and thus the “ Fluoroscopy
Various imaging in each mode of “imaging mode”, “subtraction imaging mode”, “tomographic imaging mode”, and “reconstruction mode” can be made possible.

Further, the addition processing (back projection calculation) in the addition unit 56 is performed by adding each surface parallel to the detection surface while reducing (enlarging) the image when the detector rotation mechanism 6 of the X-ray flat panel detector 3 is not provided. Is equal to Since the three-dimensional tomographic plane is defined discretely, the probability that each point H1, H2,... On the detection plane corresponds to the discrete point P1 on the three-dimensional tomographic plane as shown by the dotted line in FIG. For this reason, useless calculations such as interpolating the point P3 corresponding to the discrete point P1 with the points H1 and H2 are necessary. However, the X-ray diagnostic apparatus rotates the X-ray flat panel detector 3. The mechanism adjusts the detection surface of the X-ray plane detector 3 parallel to the three-dimensional tomographic plane as shown by the solid line in FIG. It can be formed by the adder 56. Accordingly, since the affine transformation process with a small amount of computation is performed instead of the nonlinear transformation process, the image processing time can be shortened. Furthermore, since a general-purpose affine conversion board can be used, the speed can be increased at a low cost.

[Modification of First Embodiment]
In the above description of the first embodiment, the X-ray diagnostic apparatus according to the present invention is applied to a single plane X-ray diagnostic apparatus. However, the X-ray diagnostic apparatus according to the present invention is a biplane. The present invention can also be applied to the X-ray diagnostic apparatus.

In this case, the image information is captured while the X-ray flat panel detector 3 is rotated based on the rotation angle of the C arm 4 as in the first embodiment. However, for 3D reconstruction, 9
Since image information with an angle of 0 degrees or more (in principle, 180 degrees or more) is required, in the case of this X-ray diagnostic apparatus for vibratory, the first plane is rotated by 90 degrees as shown in FIG. Control
As shown in FIG. 9, the second plane is rotated by 90 degrees so as to compensate for the rotation angle of the first plane, and the image information of 90 degrees or more is captured. Then, imaging is repeated, for example, at intervals of 1 degree while changing the projection angle of the rotation arm of each plane, and X-ray intensity distributions of 180 patterns corresponding to the obtained rotation angles, for example, 180 degrees are collected and three-dimensional reconstruction is performed.

Thereby, a tomographic image can be obtained with an X-ray diagnostic apparatus for a circulatory organ using a C-arm.
In addition, the time lag (from the state of FIG. 8 to the state of FIG. 9) from the time when the first 90-degree photographing is finished to the next photographing position, which has been a problem in the first embodiment described above. Time lag) is no longer necessary.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In this second embodiment, the X-ray diagnostic apparatus according to the present invention is applied to an X-ray diagnostic apparatus having a synchrotron as an X-ray generation means, and the X-ray from this synchrotron is used to determine the incident angle of the X-ray. By detecting with the adjusted X-ray plane detector 3, it is possible to obtain a photographed image with a desired magnification. In the description of the second embodiment, the same reference numerals are given to the portions showing the same operation as the X-ray diagnostic apparatus of the first embodiment, and the detailed description thereof is omitted. .

The synchrotron has attracted much attention in recent years as an apparatus for generating monochromatic parallel X-rays. Currently, an image intensifier (II) -television system (TV system) is known as the most practical real-time detection system for collecting X-ray moving images. When the X-ray flat panel detector 3 is used, I. As compared with the above, many advantages such as high MTF, no image distortion, and no density unevenness can be obtained. However, on the other hand, the X-ray flat panel detector 3 has a disadvantage that it cannot perform enlargement processing by the TV system.

For this reason, the X-ray diagnostic apparatus according to the second embodiment allows the X-ray flat panel detector 3 to obtain a photographed image with a desired magnification by the detector rotation mechanism 6 as shown in FIG. The incident angle of X-rays from the synchrotron is adjusted. As a result, in addition to the same effects as those of the first embodiment described above, it is possible to obtain an effect that enables a photographed image to be enlarged and photographed.

In the description of the second embodiment, the case of enlarging only one of the vertical and horizontal directions has been described for the sake of easy understanding. However, in actuality, the X-ray flat panel detector 3 is rotated around the diagonal line as an axis. The image in which the diagonal direction is enlarged can be collected.

However, although the images generally have the same vertical and horizontal sizes of pixels, the images obtained in this example are collected at fine pixel intervals in only one direction. In order to solve this problem, enlargement in another direction may be performed in terms of image processing by a method similar to digital zoom.

Finally, the description of each of the above-described embodiments is only an example of the present invention. Therefore, the present invention is not limited to these embodiments, and various modifications can be made without departing from the technical idea according to the present invention.

It is a block diagram for demonstrating the structure corresponding to fluoroscopy / imaging | photography mode in the single plane X-ray diagnostic apparatus which becomes 1st Embodiment to which the X-ray diagnostic apparatus which concerns on this invention is applied. It is a block diagram for demonstrating the structure corresponding to the subtraction imaging | photography mode in the X-ray diagnostic apparatus of the said 1st Embodiment. It is a block diagram for demonstrating the structure corresponding to the tomography mode in the X-ray diagnostic apparatus of the said 1st Embodiment. It is a block diagram for demonstrating the structure corresponding to the reconstruction mode of the subtraction image in the X-ray diagnostic apparatus of the said 1st Embodiment. It is a block diagram of the X-ray flat panel detector provided in the X-ray diagnostic apparatus of the said 1st Embodiment. It is sectional drawing of the pixel area | region and TFT area | region of the said X-ray flat panel detector. It is a block diagram of the rotational drive system of the said X-ray plane detector. It is a figure which shows each drive state of the X-ray plane detector by which rotation drive is controlled by the said rotation drive system. It is a figure which shows the other drive state of the X-ray flat panel detector controlled by the rotation drive system. FIG. 5 is a filter characteristic diagram for explaining a convolution filter in which a filter width is variably controlled according to a rotation angle of an X-ray flat panel detector that is rotationally driven by the rotational drive system. It is a figure which shows a mode that the sample point of the pixel of a three-dimensional reconstruction area | region and the sample point of an X-ray plane detector correspond by rotating the said X-ray plane detector. It is a figure for demonstrating the addition process of the pixel at the time of forming the reconstruction image of the X-ray diagnostic apparatus of the said 1st Embodiment. It is a figure which shows a mode that an X-ray flat detector can contact | adhere to a subject by rotationally driving an X-ray flat detector by the said rotational drive system. It is a figure for demonstrating the X-ray diagnostic apparatus of the 2nd Embodiment of this invention which aims at the expansion imaging | photography of the image with the parallel light from a synchrotron.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bed 2 X-ray generation part 3 X-ray plane detector 4 C arm 5 Strut 6 Detector rotation mechanism 7 A / D converter 8 Imaging condition setting part 9 Imaging condition memory 10 D / A converter 11 Display part 12 Image Memory 13 geometry conversion unit 14 affine transformation unit 15 edge enhancement unit 16 gradation conversion unit 55 subtraction unit 56 addition unit 57 filtering unit 58 filtering coefficient variable unit

Claims (4)

X-ray generation means for exposing the subject to X-rays;
An X-ray flat panel detector for converting an X-ray image transmitted through the subject into an electrical image signal;
A C-shaped arm that supports the X-ray generation means and the X-ray flat panel detector;
Supporting means for rotatably supporting the arm,
The X-ray flat panel detector is supported by the arm via an adjusting means for adjusting a support angle of the X-ray flat panel detector,
It said adjustment means, the support angle of the X-ray flat panel detector, the slide parallel to the rotation axis the axis of the arm, the axis perpendicular to the slide rotation axis or at least two axes of the diagonal of the X-ray flat panel detector, An X-ray diagnostic apparatus characterized by being adjustable. 2. The X of claim 1, wherein the adjustment means is capable of adjusting the support angle so that the detector surface of the flat detector moves in parallel according to the rotation of the arm by the support means. Line diagnostic equipment. Said adjusting means, X-rays according to claim 1 or claim 2, wherein the detection surface of the flat panel detector to adjust the pre-Symbol support angle so as to be parallel to the body axis of the subject Diagnostic device. Image processing means for performing image processing on the image signal is obtained, and a trapezoid area where X-rays are incident is obtained based on an incident angle of the X-rays to the flat detector, and the data of the trapezoid area is converted into rectangular image data. The X-ray diagnostic apparatus according to any one of claims 1 to 3, wherein:

Images