JP2008073424A - X-ray diagnostic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a rehalation and hunting phenomenon when removing an already inserted compensating filter by automatic control. <P>SOLUTION: An X-ray attenuation data table is prepared, which is based on measured data of the X-ray attenuation properties of each tube voltage. The thickness of the compensating filter 13 to prevent halation is calculated from current X-ray conditions and image level at an X-ray attenuation calculation part 27 in real time on the basis of the table's data, and the compensating filter 13 is controlled by a compensating filter controller 26 to draw back to a position causing no halation, which achieves more accurate automatic control such as to draw the compensating filter 13 back to the position causing no halation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an X-ray diagnostic apparatus, and more particularly to an X-ray diagnostic apparatus provided with a compensation filter for preventing halation from occurring on a display screen because a transmitted X-ray dose is partially excessive.

  In an X-ray diagnostic apparatus for imaging the heart and blood vessels of a subject using X-rays, if there is a large difference in X-ray transmittance between the imaging target region of the subject and its periphery, the X-ray transmittance is large. In some parts, halation may occur on the display screen. If this halation occurs, the screen becomes difficult to see and obstructs the diagnosis. Therefore, in order to prevent such inconvenience, compensation is conventionally made in the X-ray diaphragm that forms the X-ray field irradiated from the X-ray tube. A filter is provided, and a compensation filter is manually inserted at a position where halation is likely to occur while viewing a fluoroscopic image, thereby performing alignment, thereby preventing the occurrence of halation.

  FIG. 4 shows such a situation. That is, the X-ray diaphragm is used to irradiate the subject P placed on the bed (top) 4 with X-rays from the X-ray tube 11 and detect the transmitted X-rays with the X-ray detector 2. 12 is provided with a compensation filter 13 and is positioned so that the operator inserts the compensation filter 13 at an optimal position where halation does not occur while viewing an image while irradiating X-rays such as during fluoroscopy. I was going to match.

However, it is complicated to manually set the position of the compensation filter during the examination with X-ray irradiation, and it has been proposed to automatically control the insertion of the compensation filter based on image information. That is, a predetermined image level is set in advance as a halation level, a region having a level higher than the set level is detected as a halation region, and the compensation filter is moved in accordance with the detected halation region (for example, , See Patent Document 1). Thus, the compensation filter is automatically arranged at an appropriate position in a short time to prevent the occurrence of halation.
JP-A-8-275935

  By the way, in the automatic control of the compensation filter, it is necessary to automatically determine at which timing the compensation filter is inserted and at which timing the compensation filter is removed. Since the detection of the halation position can be realized by determining whether the image level of the fluoroscopic image is the maximum value, the timing for automatically inserting the compensation filter can be determined relatively easily. Further, to which part of the X-ray path the compensation filter is inserted may be controlled to an optimum position according to a predetermined algorithm based on the halation distribution of the fluoroscopic image.

  However, the timing for removing the already inserted compensation filter cannot be determined only by the image level. This is because whether or not halation occurs with the compensation filter removed is affected by the quality of X-rays even at the same image level. If this is not taken into consideration, there is a possibility that a hunting phenomenon occurs in which halation occurs again when the compensation filter is removed, and the compensation filter is automatically inserted again.

  Therefore, the present invention provides the X-ray attenuation characteristics for each tube voltage in the data measured on the device side for each quality filter so that the image level can be accurately estimated with the compensation filter removed. By preparing a table based on this and calculating in real time whether or not halation will occur even if the compensation filter is removed, automatic control that retracts the compensation filter to a position where no halation will occur can be realized with higher accuracy. The present invention has been made for the purpose of providing an X-ray diagnostic apparatus.

  In order to solve the above-described problem, an invention according to claim 1 is directed to an X-ray image based on an X-ray tube that irradiates a subject with X-rays and an X-ray irradiated from the X-ray tube and transmitted through the subject. X-ray detection means for obtaining a filter, filter means for partially reducing the X-ray dose incident on the X-ray detection means to prevent halation, and a desired position through which the X-ray passes through the filter means In an X-ray diagnostic apparatus comprising a filter moving means for arranging the X-ray attenuation data table, the change in the X-ray transmittance with respect to the thickness of the filter means in a desired X-ray condition is stored in advance as data, Based on the data stored in the X-ray attenuation data table, the calculation means for calculating the thickness of the filter means that does not generate halation based on the current X-ray conditions and the image level; Control means for controlling the drive of the filter moving means so as to move the filter means arranged at the position where the X-rays pass to a desired position where halation is not generated based on the calculation result of the calculation means; It is characterized by comprising.

  As indicated in the section for solving the above-described problems, according to the invention described in claim 1 described in the claims of the present invention, any image level can be obtained with the compensation filter removed. X-ray attenuation characteristics for each tube voltage are prepared as a table based on the data measured on the device side for each quality filter so that halation does not occur even if the compensation filter is removed. By calculating whether or not in real time, the compensation filter can be withdrawn to a position where no halation occurs, and automatic control of the compensation filter can be realized with higher accuracy.

  Hereinafter, an embodiment of an X-ray diagnostic apparatus according to the present invention will be described in detail with reference to FIGS. In these drawings, the same parts are denoted by the same reference numerals.

  FIG. 1 is a diagram showing the external appearance of an X-ray diagnostic apparatus. First, the external configuration of the X-ray diagnostic apparatus will be described with reference to FIG.

  The X-ray diagnosis apparatus 100 is configured to be suitable for diagnosis of the circulatory system such as the heart and blood vessels, for example. The X-ray generation unit 1 for irradiating X-rays and the X-ray generation unit 1 An X-ray detection unit 2 for two-dimensionally detecting X-rays, a first holding arm 3 formed in, for example, a C shape for holding the X-ray generation unit 1 and the X-ray detection unit 2 in opposite directions, and Separately, the X-ray generator 1a and the X-ray detector 2a are held in opposite directions, for example, a second holding arm 3a formed in a U shape, a bed 4 on which the subject is placed, and the X-ray detector 2 And a display unit 5 composed of a plurality of monitors for displaying X-ray images formed based on data detected by the X-ray detection unit 2a, and a stationary type installed on the floor supporting the first holding arm 3 Support the support 6 and the second holding arm 3a so that it can travel on the ceiling. It was and a overhead traveling type support unit 6a.

  Next, the internal configuration of the X-ray diagnostic apparatus will be described with reference to FIG. 2 showing a system diagram of the X-ray diagnostic apparatus. However, FIG. 1 shows an external appearance of an X-ray diagnostic apparatus 100 having two imaging units including an X-ray generation unit 1, an X-ray detection unit 2, and an X-ray generation unit 1a and an X-ray detection unit 2a. However, since the functions are the same in the description of the internal configuration, the imaging unit including one X-ray generation unit 1 and the X-ray detection unit 2 will be described in order to avoid complicated description. It shall be.

  The X-ray generation unit 1 is an X-ray tube 11 that irradiates a subject P placed on a bed (top plate) 4 with X-rays, and an X-ray that collimates the X-rays irradiated from the X-ray tube 11. In order to prevent halation of the display image, a diaphragm 12 and a compensation filter 13 that is inserted at a desired position in the X-ray path and partially reduces the X-ray dose are provided.

  The X-ray tube 11 is a vacuum tube that generates X-rays, and accelerates electrons emitted from a cathode (filament) by a high voltage to collide with a tungsten anode to generate X-rays. Therefore, the X-ray tube 11 is connected to a high voltage generator 21 that generates a high voltage to be applied between the anode and the cathode. This high voltage generator 21 has a large output capacity of 80 KW to 100 KW by, for example, an inverter system, and X-ray conditions such as a high voltage value and application time applied to the X-ray tube 11 by the X-ray controller 22 are set. It is to be controlled.

  On the other hand, the X-ray diaphragm 12 is located between the X-ray tube 11 and the subject P, and in the case of magnification imaging, a function of narrowing the X-ray beam emitted from the X-ray tube 11 to the size of the magnification imaging region. have. A compensation filter 13 is provided inside the X-ray diaphragm 12. The compensation filter 13 is well known to those skilled in the art. For example, the compensation filter 13 is provided in a disc-shaped rotary table having a through hole serving as an X-ray passage in the center, and a moving unit provided in the rotary table. It is possible to move toward the through hole that becomes the X-ray passage. Further, the rotary table itself is configured to be rotatable within the X-ray diaphragm 12 (see, for example, FIG. 3 of Patent Document 1). This compensation filter 13 is usually provided with two or three, and is inserted from a desired direction toward the X-ray path.

  The compensation filter 13 is made of a material that is semi-transparent to X-rays, and is inserted at a position where halation occurs to reduce the X-ray dose of the portion. Is formed in a tapered shape, and when inserted into the X-ray passage, the X-ray dose at the end thereof does not change extremely but changes smoothly. The control means for inserting the compensation filter 13 into a desired position in the X-ray path and withdrawing from the insertion position will be described later.

  Next, the X-ray detection unit 2 converts the X-rays that have passed through the subject P into charges, accumulates them, and reads out the accumulated charges as an X-ray image signal. A type in which X-rays converted into light by a fire (II) are photographed with a television camera is used.

  The X-ray detection unit 2 is connected to the image processing unit 23. The image processing unit 23 stores the image data serially sent from the X-ray detection unit 2, performs a subtraction process, or converts the image data into a TV format to generate a video signal. Then, the video signal generated by the image processing unit 23 is supplied to the display unit 5 constituted by a monitor such as a liquid crystal or a CRT, and is displayed as an X-ray diagnostic image.

  The image processing unit 23 is also connected to the image level / distribution calculation unit 24 and supplies the image information obtained by the image processing unit 23. The image level / distribution calculation unit 24 is connected to a filter position detector 25 that detects the current position of the compensation filter 13 and is supplied with position information of the detected compensation filter 13. A compensation filter controller 26 is provided to control insertion and withdrawal of the compensation filter 13 to / from a desired position in the X-ray path.

  In addition, what was shown with the code | symbol 27 in the figure is the X-ray attenuation calculation part which should also be called the characteristic component of this invention. A system control unit 7 having a memory and a CPU for organically controlling the components, and a keyboard for an operator to give various instructions and input set values to the system control unit 7; An operation unit 8 including various switches and a mouse is provided. The X-ray diagnostic apparatus 100 is also provided with a mechanism unit that moves the holding arm 3 and the bed (top plate) 4, a mechanism control unit that controls each mechanism of the mechanism unit, and the like. Under these controls, the rotation / movement operation is performed, but these are not directly required for the description of the present invention, and therefore illustration and description thereof are omitted here.

  Next, the function of the X-ray attenuation calculation unit 27 will be described with reference to FIG.

  FIG. 3 shows a characteristic diagram called an X-ray attenuation curve. This X-ray attenuation curve represents the ratio of the incident dose and the transmitted dose with respect to the thickness of the compensation filter. The horizontal axis is the thickness of the compensation filter, and the vertical axis is the ratio of the incident dose and the transmitted dose. It shows how the state changes depending on the tube voltage of the tube. In FIG. 3, three types of tube voltage A, tube voltage B, and tube voltage C are shown, but each tube voltage has a relationship of tube voltage A <tube voltage B <tube voltage C. As can be seen from FIG. 3, the X-ray transmittance of the compensation filter increases as the tube voltage increases. This is because the average X-ray energy irradiated from the X-ray tube 11 increases as the tube voltage increases.

  Therefore, in the present invention, an X-ray attenuation curve is obtained for each tube voltage of the compensation filter used in advance, and is stored as an X-ray attenuation data table in, for example, the memory of the system control unit 7 of the X-ray diagnostic apparatus 100. Keep it. When the image in which the compensation filter 13 has already been inserted is observed and the compensation filter 13 is to be retracted to the optimum position because the image has become dark, the current applied to the X-ray tube 11 The X-ray transmittance at that time is calculated from the tube voltage and the thickness of the compensation filter 13, and to what extent the compensation filter 13 is retracted is calculated in real time and no halation occurs. The compensation filter 13 is evacuated to the position, and the calculation is performed by the X-ray attenuation calculation unit 27.

  In the X-ray diagnostic apparatus 100 having such a configuration, operations when inserting and retracting the compensation filter 13 will be described.

  First, when the compensation filter 13 is inserted, the X-ray diagnostic apparatus 100 usually has an automatic brightness adjustment function so that the image level (the brightness level of the image) is constant during X-ray fluoroscopy. The line conditions are automatically controlled so that the brightness of the X-ray image displayed on the display unit 5 is kept constant. Further, based on the image information obtained from the image processing unit 23, the image level / distribution calculation unit 24 detects the image level and the distribution of halation.

  As a result, if it is determined that the compensation filter 13 needs to be inserted, the halation occurrence position detected by the image level / distribution calculation unit 24 from the current position of the compensation filter 13 detected by the filter position detector 25. The compensation filter 13 is automatically moved by the compensation filter controller 26. That is, since data such as the image level and the distribution of halation is sent from the image level / distribution calculation unit 24 to the system control unit 7, the system control unit 7 generates halation to the compensation filter controller 26 based on this information. The movement of the compensation filter 13 to the position is instructed. Therefore, the compensation filter 13 is inserted at the designated position.

  By the way, when the image becomes darker than necessary due to the insertion of the compensation filter 13, the compensation filter 13 is retracted to the optimum position. Since this control has not been successful in the past, in the present invention, the image level when the compensation filter 13 is removed from the current thickness of the compensation filter 13 and the current tube voltage condition applied to the X-ray tube 11. Further, the thickness of the compensation filter 13 where halation starts is calculated in real time by the X-ray attenuation calculation unit 27 while referring to the X-ray attenuation data corresponding to the X-ray conditions stored in advance in the system control unit 7 as a table. However, the compensation filter 13 is moved while confirming whether halation does not occur even if the compensation filter 13 is removed.

  That is, the image level in the image and its distribution are calculated by the image level / distribution calculation unit 24 in relation to the position of the currently inserted compensation filter 13, and the result is sent to the system control unit 7. Based on the result, the system control unit 7 estimates various conditions in which halation does not occur even if the compensation filter 13 is removed, and determines the compensation filter 13 from the X-ray attenuation data based on the current X-ray conditions for all the conditions. The X-ray attenuation calculation unit 27 performs calculation for confirming whether halation does not occur regardless of the thickness up to which direction. Then, based on the calculation result in the X-ray attenuation calculation unit 27, the system control unit 7 gives an instruction to the compensation filter controller 26 to exit the compensation filter 13 in a predetermined direction until a predetermined thickness is reached. As a result, the compensation filter 13 moves to a position where the image level is restored to a predetermined level and no halation occurs.

  In this manner, it is possible to reliably prevent the compensation filter 13 from being out of the halation region and causing halation again under any X-ray conditions. Further, the occurrence of a hunting phenomenon that automatically repeats insertion and withdrawal of the compensation filter is prevented, and the accuracy of automatic compensation filter control is greatly improved.

  As described in detail above, according to the present invention, the X-ray attenuation characteristic for each tube voltage is determined for each quality filter so that the image level can be accurately estimated with the compensation filter removed. Prepared as an X-ray attenuation data table based on data measured on the apparatus side, and by calculating in real time whether or not halation will occur even if the compensation filter is removed, the compensation filter is retracted to a position where no halation occurs Accordingly, an X-ray diagnostic apparatus that realizes automatic control of the compensation filter with higher accuracy is provided.

  Needless to say, the present invention is not limited to the above-described one embodiment, but can be implemented in various modes without departing from the scope of the invention.

1 is an external view of an embodiment of an X-ray diagnostic apparatus according to the present invention. It is the block diagram which showed schematic structure of one Example of the X-ray diagnostic apparatus which concerns on this invention. It is a characteristic view called the X-ray attenuation curve shown in order to demonstrate the effect | action of this invention. It is explanatory drawing shown in order to demonstrate the use condition of the compensation filter in a X-ray diagnostic apparatus.

Explanation of symbols

1 X-ray generator 2 X-ray detector 3 Holding arm 4 Bed (top)
DESCRIPTION OF SYMBOLS 5 Display part 6 Support device 7 System control part 8 Operation part 11 X-ray tube 12 X-ray restrictor 13 Compensation filter 21 High voltage generator 22 X-ray control part 23 Image processing unit 24 Image level / distribution calculation part 25 Filter position detection 26 Compensation filter controller 27 X-ray attenuation calculation unit 100 X-ray diagnostic apparatus

Claims (1)

An X-ray tube for irradiating the subject with X-rays, an X-ray detection means for obtaining an X-ray image based on the X-rays emitted from the X-ray tube and transmitted through the subject, and incident on the X-ray detection means An X-ray diagnostic apparatus comprising: filter means for partially reducing the X-ray dose to prevent halation; and filter moving means for disposing the filter means at a desired position through which the X-ray passes.
An X-ray attenuation data table in which changes in the X-ray transmittance with respect to the thickness of the filter means under desired X-ray conditions are stored as data;
Based on the data that the X-ray attenuation data table has, an arithmetic means for calculating the thickness of the filter means that does not generate the halation from the current X-ray condition and the image level;
Control means for controlling the driving of the filter moving means so that the filter means already arranged at the position where the X-rays pass is moved to a desired position where halation is not generated based on the calculation result of the calculation means. An X-ray diagnostic apparatus comprising:

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