JP4632845B2 - X-ray diagnostic equipment - Google Patents

Description

The present invention relates to X-ray diagnostic equipment. In particular, the present invention relates to an X-ray diagnostic apparatus that uses an X-ray flat panel detector to capture a plurality of images asynchronously and continuously.

  In recent years, as X-ray diagnostic apparatuses, the portability of screen / film systems and imaging plates, the high resolution characteristics of film / screen systems, I. (Image Intensifier)-A device using a flat panel detector using a TFT (thin film transistor) having a real-time property of a TV system as a switching gate has been developed.

  A flat panel detector using thin film technology (TFT) as a switching element for each pixel using thin film technology, a phosphor for converting X-rays into light on a flat detection surface, a photodiode for converting the light into charges, And a TFT for reading out (outputting) electric charges, and photodiodes (and capacitors, TFTs) are two-dimensionally arranged (in an array and in a plane). In this flat panel detector, a thin film is formed on one side of a glass substrate, patterned by etching, further formed by stacking thin films, and patterned again. Is formed.

  FIG. 7 is a circuit diagram showing a main configuration of the flat detector. The flat panel detector shown in FIG. 7 has an X-ray detection element 124 (TFT 123 may be included in the X-ray detection element) composed of a photodiode (including a capacitor) (not shown) as one element, and this is the column direction and the row direction. It is arranged in a two-dimensional array (in the line direction). As the X-ray detection element 124, there is selenium capable of directly converting X-rays into electric charges. However, the X-ray detection element 124 is not limited to selenium. A combination of an intensifying screen and a photodiode may be used.

  The gate terminal of the TFT 123 is commonly connected as a gate drive line for each line, and is connected to each line output terminal of the gate driver 125. The drain terminal of the TFT 123 is commonly connected as a data signal line for each column, and is connected to the multiplexer 127 via an integration circuit 126 including a read-out amplifier, a capacitor, and a reset switch for reset (not shown). Connected to each input terminal.

  Each line output terminal of the gate driver 125 outputs a pulse-like control signal in order in time series. By this pulse-like control signal, the TFTs 123 on the same line are simultaneously turned on and are different. The TFTs 123 in the line are turned on in time series so as not to overlap each other.

  Multiplexer 127 takes in the signals input to the input terminals during one pulse output from the line output terminals of gate driver 125 one by one in time series and outputs the signals from the output terminals. It has become.

  Accordingly, when one line of TFT 123 is simultaneously turned on by the pulse-like control signal output from each line output terminal of the gate driver 125, the charge accumulated in the storage capacitor (not shown) is output through the TFT 123, This electric charge is converted into a voltage via the integrating circuit 126 and output one by one (one pixel per line) in order by the multiplexer 127. When the reading of one line is completed in this way, reading of the next line is started.

  As described above, the flat panel detector reads the detection signals one by one (one pixel at a time) from each X-ray detection element 124 for each line and outputs it as image data (video signal) for one screen. Here, the period during which the imaging data for one screen is read from the flat panel detector is one frame. For this reason, in the flat detector, it takes time to read out the image signal.

  In the flat detector as described above, when the gate line is OFF, the signal can always be accumulated. For this reason, when the gate line is turned on once and a signal is read and turned off, a leak current or the like is accumulated in each X-ray detection element until the signal is turned on next time. However, if the leak current is different, the reference is different every time, and a normal image cannot be obtained. In order to prevent this, it is necessary to continue driving the X-ray detection element at a constant cycle or to turn on all the gate lines once and reset the leakage current etc. before irradiating the X-rays.

  However, when taking a picture at a specified position while moving the detector, such as DSA or rotating DSA, it takes time to reset if it is reset after coming to the desired position. It takes time to actually shoot. Furthermore, since the detector moves during that time, it is not possible to take a picture at the original designated position.

For this reason, there has been proposed an X-ray imaging apparatus capable of performing X-ray exposure for a desired time at an arbitrary timing with an X-ray detector being continuously driven, and capable of obtaining an accurate X-ray image. Thus (see Patent Document 1), it is possible to perform imaging in a state where the flat detector is continuously driven. This will be described with reference to FIG.
As shown in FIG. 8, the flat panel detector always keeps reading without providing a blanking period. For example, X-rays are irradiated at position 1. In this case, X-rays are irradiated from the middle of the frame and X-ray irradiation is completed in the middle of the next frame. However, when the X-ray irradiation is completed, the X-ray detection elements are still charged. Is accumulated. Therefore, the data of the next frame after the X-ray irradiation end frame is acquired, and an image is reconstructed from a total of three pieces of image data. Next, it is assumed that the X-ray is irradiated after moving to the position 2. At this time, an image can be reconstructed from two pieces of image data if it is within one frame period from X-ray irradiation to the end. This algorithm will be described with reference to FIG.

FIG. 9 is a diagram for explaining an algorithm for acquiring an image according to Patent Document 1. In FIG. In FIG. 9, as shown in (a), the period from the X-ray irradiation to the end is within one frame period, but the data in each frame is as shown in (b).
In FIG. 9, since the first image is irradiated with X-rays from the middle of the frame, the amount of charge at the start of X-ray irradiation is small and gradually increases according to the amount of X-ray irradiation. Has been. In the second image, the remaining data is read and a desired image is obtained by combining the first and second images. FIG. 10 shows how an image is reconstructed with three pieces of image data, but the description is omitted because it is basically the same as FIG.

However, it is preferable that images can be collected at as short a shooting interval as possible when performing a plurality of continuous shootings in an asynchronous operation such as DSA (Digital Subtraction Angiography) or rotating DSA. However, in the method described in Patent Document 1, since the image of the next frame after the last frame after the X-ray irradiation is also used for the image configuration, the next X-ray can be irradiated even in the earliest case. This is the start of the next frame. In other words, it is necessary to wait for a maximum of two frames after the end of X-ray irradiation until the next X-ray irradiation.
JP-A-9-140691

The present invention aims to provide an X-ray diagnostic equipment was shorter than the conventional irradiation intervals of the X-ray.

In the invention according to the aspect of the present invention, a plurality of X-ray detection elements (124) that are arranged in a matrix and store detected X-rays as charges, and are stored in the plurality of X-ray detection elements of the X-ray detector. The readout means (5) for sequentially reading out the generated charges for each line as a pixel signal and the effective information from the X-ray irradiation start frame to the next frame after the X-ray irradiation end are added to regenerate one image. Comprising means (17) for composing, wherein the reconstructing means separates the pixel signal of the next frame after the X-ray irradiation into information of two preceding and following X-ray images at a predetermined position. It is characterized by that .

The present invention can provide an X-ray diagnostic equipment was shorter than the conventional irradiation intervals of the X-ray.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of the X-ray diagnostic apparatus according to the present embodiment. The present invention is applied to a configuration having two flat detectors (in this specification, such a configuration is referred to as a “biplane”), but the basic configuration is also applicable to a single detector. Since it is the same, FIG. 1 shows only the configuration of one flat detector. Since the circuit configuration of the flat detector is the same as the configuration of FIG. 7 described above, illustration and description thereof are omitted.

  As shown in FIG. 1, in the X-ray diagnostic apparatus, an X-ray generation unit 12 and an X-ray detection unit 15 are supported by a holding unit 23 so as to face each other with a subject 13 interposed therebetween. A high voltage generator 10 is provided in front of the X-ray generator 12, and supplies a high voltage to the X-ray tube 11 of the X-ray generator 12. X-rays emitted from the X-ray tube 11 are shaped to have a predetermined beam width by the X-ray restrictor 22 and are emitted to the subject 13.

  X-rays that have passed through the subject 13 are detected by the flat detector 25 of the X-ray detector 15 and converted into electrical signals. The electrical signals are sequentially read under the control of the gate driver 5 and are subjected to current / voltage conversion by the charge / voltage converter 6. The electrical signal converted into the voltage signal is converted into a digital signal by the A / D converter 7 and then subjected to parallel / serial conversion by the parallel / serial converter 8 to obtain an image of the subject 13. The image signal of the subject 13 is output to an image storage circuit 16 including a large-capacity external storage device such as a memory such as a DRAM or EEPROM, an HDD, or an optical disk, for example. The charge / voltage converter 6 to the parallel / serial converter 8 constitute an image data generation unit 26.

  The image signal stored in the image storage circuit 16 is temporarily developed in the display image memory 36 of the display unit 21, then converted into an analog signal by the D / A converter 31, and converted into a video signal by the display circuit 32. And displayed on the monitor 33.

  In FIG. 1, a system control unit 17 controls the operation of each unit. Further, the system control unit 17 receives an operation of the operation unit 20 and performs control according to the operation. The operation unit 20 includes, for example, a keyboard and operation buttons. The mechanism control unit 18 performs control for moving and rotating the holding unit 23 three-dimensionally.

The operation of the X-ray diagnostic apparatus according to one embodiment of the invention configured as described above will be described.
When continuously acquiring images of the subject 13 while moving the flat detector of the X-ray diagnostic apparatus, it is not possible to capture all the frames following the frame at the end of the X-ray irradiation as in the prior art. Rather, the image data is separated in the middle of the frame following the frame at the end of X-ray irradiation. This will be specifically described below.

  FIG. 2 is a diagram for explaining a control method according to an embodiment of the present invention. As a precondition for this embodiment, it is assumed that the next X-ray irradiation is performed after a period of one frame period or more after the X-ray irradiation is completed.

  As shown in FIG. 2 (a), in the first X-ray irradiation, it is necessary to reconstruct an image using data of a frame with a circle. In the second X-ray irradiation, it is necessary to reconstruct an image by using data of a frame with Δ. For this reason, in the frame period in which ◯ and Δ overlap, the two previous and subsequent image data are acquired in an overlapping manner. However, as shown in (b), when looking at the data of each X-ray detection element in one frame, the first irradiation data (indicated by hatching) and the second irradiation data are accumulated. It can be seen that the X-ray detection elements (pixels) are not X-ray detection elements of the same line. Therefore, although the data is in the same frame, the data at the first irradiation and the data at the second irradiation can be separated. As shown in FIG. 3, when the period from the end of the first irradiation to the start of the second irradiation is shorter than one frame period, the same pixel as shown in FIG. In addition, since the first irradiation data and the second irradiation data are accumulated, the image cannot be separated by pixels as shown in FIG.

With reference to FIG. 4, specifically, from which data to which data is handled as one image data will be described. FIG. 4 is a timing chart for explaining the handling of image data.
In FIG. 4, it is assumed that X-ray irradiation starts at time t1, and irradiation ends at time t2. At time t1, the gate of the vertical selection line 4 in the first frame is turned on, and at time t2, the gate of the vertical selection line 5 in the third frame is turned off. Here, it is obvious that the charges due to the X-rays are accumulated in each pixel between the times t1 and t2.
Here, if the start of the image is made from the time when the gate of the vertical selection line 4 of the first frame is turned on, the image data from the start of the X-ray irradiation can be acquired. Then, since the X-ray irradiation is completed at time t2, each photoelectric detection element accumulates electric charges by the X-ray irradiation so far. Therefore, the gate-off of the vertical selection line 5 in the fourth frame is set as the end time of image acquisition by X-ray irradiation from time t1 to time t2. That is, the image acquisition by the X-ray irradiation from the time t1 to the time t2 is performed using the period from the start of the X-ray irradiation to the time one frame after the irradiation is ended as the image acquisition period. The next X-ray irradiation for image acquisition can be performed when the gate of the vertical selection line 5 in the fourth frame is turned off. That is, X-rays are irradiated after the gate of the vertical selection line 6 in the fourth frame is turned on, and the next image acquisition can be started from that point in the same manner as described above. In this specification, the function of separating the detection data in one frame period into the previous image data and the next image data in accordance with the end of X-ray irradiation is referred to as a “separation function” in this specification.

  By the separation function as described above, from the time when the X-ray irradiation is completed to the middle of the next one frame period can be used as the previous image data readout period, and the next image can be acquired immediately thereafter. . As shown in FIG. 5, conventionally, it is necessary to separate the X-ray irradiation period and the readout period, and a blanking period is provided. However, in the present invention, the X-ray irradiation image acquisition period is set in units of vertical selection lines. It is not necessary to provide a blanking period.

  When the separation function as described above is not provided, as shown in FIG. 6A, the period until the end of the next frame after the end of X-ray irradiation is used as the reading period of the previous image data. Until the readout period ends, the next X-ray irradiation cannot be performed. On the other hand, in the embodiment of the present invention, as shown in FIG. 6B, when the X-ray irradiation is completed, the next X-ray irradiation can be started by setting at least one frame period. . Therefore, according to the embodiment of the present invention, images can be collected at as short a shooting interval as possible when performing a plurality of continuous shootings. Further, the shorter the driving period of the flat detector, the shorter the X-ray irradiation interval. Therefore, the X-ray irradiation interval can be shortened by not providing a blanking period for driving the flat panel detector. Furthermore, this is more effective because the influence of shading due to the reading order can be reduced.

  Conventionally, the image of the next frame after the irradiation of X-rays is used for the synthesis of the previous X-ray image. When the next X-ray is irradiated during this frame, the next X-ray image appears in this image. However, with the configuration as described above, it is possible to separate an image by previous X-ray irradiation and an image by subsequent X-ray irradiation from one image. That is, immediately before the end of the first X-ray irradiation, based on the positional information of the gate line that is in the ON state, up to the same gate line of the next frame is set as the previous image information. That is, at this time, all the charges accumulated in the pixels by the X-ray irradiation are read out, so that the next X-ray irradiation for image acquisition may be performed. Therefore, when the next X-ray irradiation is performed immediately after this, the signal after the same gate line is the next signal even if it is an image of the same frame based on the position information of the gate line in the ON state. X-ray image information is obtained. Therefore, if the X-ray irradiation interval is longer than the driving period of the flat panel detector, the previous image and the next image can be spatially separated on one image.

  Further, the shorter the driving period of the flat detector, the shorter the X-ray irradiation interval. Therefore, it is better not to provide a blanking period for driving the flat panel detector. This is more effective because the influence of shading due to the reading order can be reduced.

  In addition, when imaging is performed at a plurality of positions with a DSA or the like position trigger using a flat detector, the flat detector is continuously driven and moved while irradiating X-rays at a predetermined position. Repeatedly irradiate X-rays at the same position, and add each image from the frame where X-ray irradiation started to the next frame after the last frame where X-ray irradiation ended. This is effective for making images of.

  The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention at the stage of implementation. Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements.

  In addition, for example, even if some structural requirements are deleted from all the structural requirements shown in each embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the effect of the invention Can be obtained as an invention.

1 is a block diagram showing a schematic configuration of an X-ray diagnostic apparatus according to an embodiment. The figure for demonstrating the control method which concerns on one Embodiment of this invention. The figure which shows the case where the period of 1 frame or more cannot be taken by the time of the 2nd irradiation start. The figure for demonstrating the method handled as one image data. The figure shown about the case where a blanking period is provided between X-ray irradiation, and the case where it does not provide. The figure for demonstrating the difference between this invention and the conventional method. The circuit diagram which shows the principal part structure of a plane detector. The figure which shows a mode that imaging | photography is possible in the state which driven the flat detector continuously. The figure for demonstrating the algorithm which reconstructs an image from two image data. The figure for demonstrating the algorithm which reconstructs an image from the image data of 3 sheets.

Explanation of symbols

4 ... vertical selection line 5 ... gate driver 6 ... charge / voltage converter 7 ... A / D converter 8 ... parallel / serial converter 10 ... high voltage generator 11 ... X-ray tube 12 ... X-ray generator 13 ... covered Sample 15 ... X-ray detection unit 16 ... Image storage circuit 17 ... System control unit 18 ... Mechanism control unit 20 ... Operation unit 21 ... Display unit 22 ... Line constrictor 23 ... Holding unit 25 ... Planar detector 26 ... Image data generation unit 31 ... D / A converter 32 ... Display circuit 33 ... Monitor 36 ... Image memory for display

Claims (5)

A plurality of X-ray detection elements arranged in a matrix and storing detected X-rays as electric charges;
Reading means for sequentially reading out the charges accumulated in the plurality of X-ray detection elements of the X-ray detector for each line as pixel signals;
A means for reconstructing one image by adding effective information from the X-ray irradiation start frame to the next frame after the X-ray irradiation end;
The reconstruction means separates the pixel signal of the frame next to the frame after the irradiation of X-rays into information of two preceding and following X-ray images at a predetermined position. .   2. The X-ray diagnostic apparatus according to claim 1, wherein the predetermined position is up to a line from which all pixel signals accumulated by previous X-ray irradiation are read out.   2. The X-ray diagnostic apparatus according to claim 1, wherein the predetermined position is a line from which an image signal is read out immediately before the end of X-ray irradiation, and is a pixel signal to the line read out in the next frame. Is separated as the previous X-ray image information, and the subsequent pixel signals are separated as the next X-ray image information.   The X-ray diagnostic apparatus according to any one of claims 1 to 3, wherein a period from the end of the previous X-ray irradiation to the start of the next X-ray irradiation is one frame or more. X-ray diagnostic equipment.   5. The X-ray diagnostic apparatus according to claim 1, wherein a signal is continuously read without providing a blanking period in driving the flat panel detector. .

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