JP2013013442A - Image processing device, image processing method and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that it has been required to stop acquiring an image whenever a reference image for correction is updated while the image is continuously acquired in perspective projection.SOLUTION: An image processing device is connected to X-ray generation means for generating an X-ray and a detection means for detecting the X-ray and outputting data according to the X-ray and corrects the image data according to the X-ray as the X-ray, by using the image data obtained from the detection means while the generation means does not generate the X-ray as the reference data. When a change amount of a temperature is larger than a predetermined one, while a measurement result of the temperature around the detection means is obtained, the X-ray is continuously generated from the generation means, and the X-ray image is obtained from the detection means, the image processing device controls the generation means to temporarily stop the generation of the X-ray, and updates the reference image by using the image data obtained from the detection means while the generation means temporarily stops generating the X-ray.

Description

  The present invention relates to an image processing apparatus, an image processing method, and a program for correcting image data obtained from detected X-rays using a reference image.

  An X-ray diagnostic imaging apparatus performs X-ray irradiation by placing an X-ray generator on one side and an X-ray detector on the other side with a subject placed in the center, and image information from the signal output from the X-ray detector. And used for various diagnoses.

  An X-ray flat panel detector that outputs an image as a digital signal is a matrix of pixels composed of a phosphor that converts X-rays into visible light, a photoelectric conversion element that converts visible light into electric charge, and a switching element (TFT). It is configured by combining photoelectric conversion panels arranged in the above. In recent years, the spread of X-ray flat panel detectors has progressed, and the fields that can be applied in X-ray image diagnosis are increasing. For example, X-ray fluoroscopy devices and continuous radiographing devices that often used image intensifiers (I.I.) have become widespread.

  In such an apparatus that performs operations for a long time such as X-ray fluoroscopy and continuous imaging, problems related to heat generation of electrical components have become prominent. Since the amount of dark current in the photoelectric conversion element of the X-ray flat panel detector and the transfer amount, which is the ability of the switching element to transfer charges, vary from pixel to pixel, these are corrected using a reference image acquired in advance. The However, these dark currents and transfer amounts have temperature characteristics, and these characteristics also differ from pixel to pixel. If the temperature at which the reference image for correction is obtained rises while the image acquisition continues, the signal output value from each pixel differs from the X-ray input information. Variation will occur. As a result, a portion having a density different from the actual density is generated in the output image and it becomes difficult to find an abnormality of the subject, or the density changes with time, resulting in an image that is difficult to observe. Also, the longer the operation, the greater the heat generated by the electrical components, making it difficult to stably obtain images with high reproducibility.

  In response to this problem, Patent Document 1 proposes that the temperature is acquired prior to fluoroscopy, and that the image is configured by comparing the input / output characteristics stored in advance and the temperature at the time when the input / output characteristics are acquired. Yes. However, during fluoroscopy over a long period of time, the temperature continuously changes during image acquisition, and thus it is necessary to update the reference image for correction at an appropriate timing. In response to this problem, Patent Document 2 discloses a technique for notifying the operator that the reference image needs to be updated when the temperature rises or falls by a predetermined value or more compared to the reference temperature. Proposed.

JP-A-10-260487 JP 2007-185375 A

  However, in Patent Document 2, after notifying the operator that the reference image needs to be updated, the update operation is performed by interrupting the fluoroscopic operation and pressing the update button. That is, in order to update the reference image for correction while continuously acquiring images in the fluoroscopic operation, there is a problem that the image acquisition must be stopped each time. On the other hand, when image acquisition is continued without updating the reference image, there is a problem that it is difficult to maintain sufficient image quality.

  In order to achieve the above object, an image processing apparatus according to the present invention is connected to a generation unit that generates X-rays and a detection unit that detects the X-rays and outputs image data corresponding to the detected X-rays. An image processing apparatus that corrects image data corresponding to the X-ray and outputs it as an X-ray image using image data obtained from the detection means as a reference image in a state where the generating means does not generate X-rays. An amount of change in temperature during the acquisition of X-ray images from the detection means by continuously generating X-rays from the generation means and acquisition means for acquiring a temperature measurement result around the detection means; Control means for controlling the generating means so as to temporarily stop the generation of X-rays, and when the generating means temporarily stops the generation of X-rays, Image acquired from detection means Characterized in that and an updating means for updating the reference image by using the data.

  According to the present invention, it is possible to avoid image degradation due to the influence of a temperature change of the sensor panel during long-time continuous moving image acquisition.

The block diagram which shows the function structure of a X-ray image diagnostic apparatus. The flowchart which shows an example of the procedure of performing judgment and issuing of correction data update from a temperature measurement result. The flowchart which shows an example of the procedure from the start of fluoroscopic operation to completion | finish. 6 is a timing chart showing an example of image acquisition timing.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<< Embodiment 1 >>
FIG. 1 is a block diagram showing a functional configuration of the X-ray image diagnostic apparatus according to the present embodiment. An X-ray tube 100 for generating and irradiating X-rays and an X-ray detector 101 for receiving X-rays are arranged so as to face each other to constitute an imaging system. The X-ray tube 100 is supported by a support mechanism (not shown), and is configured to be able to adjust the position, such as the direction and height of X-ray irradiation. The X-ray detector 101 is also supported by a support mechanism (not shown) and corresponds to positioning with respect to the X-ray tube 100 and the subject M.

  The control unit 151 controls hardware such as the X-ray tube 100 and the X-ray detector 101 and various software. Various programs, various parameters, and the like used in the control unit 151 are stored in the data storage unit 155. The operation unit 160 is a part for inputting the start and end of photographing and fluoroscopy, and an ON / OFF switch such as an exposure switch or a foot pedal, or a keyboard, a mouse, a touch panel, or the like may be used together. . The image acquisition unit 152 acquires the electrical signal output from the X-ray detector 101 as image data. The correction processing unit 153 adds a process for correcting the input / output characteristics unique to each pixel of the image data in accordance with the configuration of the diagnostic apparatus and the operating conditions. This correction process is a process generally called dark current correction (offset correction). When it is necessary to obtain a reproducibility with higher accuracy, correction processing called gain correction is also performed at the same time. The image data subjected to the correction processing is subjected to image processing in a form suitable for observation and diagnosis in the image processing unit 154 and displayed as a result on the image display unit 170.

  The dark current correction is described in detail in Patent Document 1 and will not be described here, but a reference image acquisition method necessary for correction will be described below.

  The X-ray detector 101 is operated without X-ray irradiation from the X-ray tube 100. Then, only dark current generated inside the flat detector is detected without receiving X-ray information. The image acquired by the image acquisition unit 152 in this way is a reference image in dark current correction. The X-ray image diagnostic apparatus according to the present invention can acquire a reference image at any timing as long as X-ray irradiation is not performed. The reference image necessary for the correction is stored / saved in the data storage unit 155, and can be overwritten and updated as necessary.

  The control unit 151, the image acquisition unit 152, the correction processing unit 153, the image processing unit 154, and the data storage unit 155 are each a part of the computer 150, and the X-ray tube 100 and the X-ray detector 101 are connected to the computer 150. Has been. The image display unit 170 is a general computer display.

  The temperature measurement unit 102 measures the temperature around the X-ray detector 101 and transmits the measurement result to the control unit 151. The temperature measuring means 102 can measure the temperature more accurately as it is provided closer to the X-ray detector 101. The temperature measuring means 102 is installed around the X-ray detector 101 such as a support mechanism of the X-ray detector 101 or an outer frame that supports the panel in the panel-shaped X-ray detector 101.

  FIG. 2 is a flowchart illustrating an example of a procedure for determining and issuing a reference image update from the temperature measurement result. Unless otherwise specified, it is the control unit 151 that performs the operation of each step. The procedure of FIG. 2 is continuously executed while the fluoroscopic operation is being executed.

  In the flowchart of FIG. 2, it is first determined whether or not to continue fluoroscopy (S1). If the fluoroscopy is not continued (No in S1), that is, if the operation is stopped, the process is terminated. When fluoroscopy is continued (Yes in S1), the steps S2 to S6 are sequentially performed. First, a first temperature measurement is performed by the temperature measuring means 102 (S2). The temperature of the measurement result is Ta. After waiting for a predetermined time (t) (S3), the temperature measuring means 102 performs the second temperature measurement (S4). The temperature of the measurement result is Tb. Subsequently, the difference between Ta and Tb is compared with a predetermined temperature difference reference value ΔTo (S5). When the difference between Ta and Tb is equal to or smaller than ΔTo, the process returns to S1. If the difference between Ta and Tb exceeds the predetermined value ΔTo, it is determined that the reference image needs to be updated, and an update is issued (S6). Thereafter, the procedure returns to S1 and the procedure is repeated. The temperature values Ta and Tb are overwritten and updated each time.

  Here, ΔTo is obtained by confirming the relationship between the temperature change and the reproducibility of the image through experiments or the like, and is a numerical value whose optimum value changes depending on the time t. For this reason, in some cases, ΔTo and time t may be treated as changeable parameters. In this case, a plurality of tables corresponding to the device settings and environmental conditions may be stored in the data storage unit 155, and the optimal ΔTo and time t may be selected and applied under each condition, and ΔTo and time t are used. It is good also as a person sets freely. Even if the difference between Ta and Tb is the same, the optimal ΔTo value may differ depending on whether Ta> Tb or Ta <Tb, that is, whether the temperature has increased or decreased. . In this case, a more accurate determination can be made by setting the determination conditions in S5 using a plurality of equations.

  FIG. 3 is a flowchart illustrating an example of a procedure from the start to the end of the fluoroscopic operation in the X-ray image diagnostic apparatus according to the present embodiment. Unless otherwise specified, it is the control unit 151 that performs the operation of each step.

  A fluoroscopic operation is started by an operation input from the operation unit 160. First, a reference image is acquired (S11), and the reference image is updated (S12). The reference image is updated by overwriting an existing reference image. S11 and S12 are performed in an extremely short time that is not recognized as a time lag by the user. Thereafter, generation and irradiation of X-rays are started from the X-ray tube 100 (S13). Then, the X-ray detector 101 detects an X-ray image transmitted through the subject M (S14), and the image acquisition unit 152 acquires image data (S15). The acquired image data is subjected to correction processing using the reference image in the correction processing unit 153 (S16). Then, the image processing unit 154 performs image processing for display (S17), and displays an image on the image display unit 170 (S18). Thereafter, it is determined whether or not there is an instruction when the reference image needs to be updated (S19). If there is an announcement (Yes in S19), the process proceeds to S22, and if not (No in S19), the process proceeds to S20. In S20, it is determined whether or not there is an input to end fluoroscopy from the operator. If there is an input, the process proceeds to S21, and if there is no input, the process returns to S14 and X-ray detection is performed again. In S21, the generation and irradiation of X-rays are finished, and the fluoroscopic operation is finished. On the other hand, in S22, generation and irradiation of X-rays are temporarily stopped. Then, the reference image acquisition (S11) is performed again.

  Through the above process, the reference image is automatically updated in the X-ray image diagnostic apparatus according to the present embodiment. That is, even during long-time fluoroscopy, a predetermined temperature change is detected and the reference image is updated appropriately, so that image diagnosis can be continued in a state where image reproducibility is not deteriorated. Further, since the reference image is updated only when the amount of change in temperature exceeds a predetermined value, the update frequency can be minimized.

  In the above description, the fluoroscopic operation used for diagnosis or the like by displaying an image in real time has been described. In the X-ray image diagnostic apparatus according to the present embodiment, an imaging operation for storing image data may be performed. In addition, two operation modes, a fluoroscopic mode for performing a fluoroscopic operation and a photographing mode for performing photographing, may be prepared, and these may be used in accordance with an input from the operation unit 160.

  In the case of the shooting mode, the processed image data generated by the image processing unit 154 is stored in the data storage unit 155. Note that the image to be stored may be a moving image obtained by acquiring a plurality of temporally continuous images in the same process as the fluoroscopic operation and collecting them as a series, or may be a single still image.

  Note that in imaging for acquiring and storing still images, generation and irradiation of X-rays are stopped when one image acquisition is completed. For this reason, the procedure of S19 and S20 of the flowchart in FIG. 3 becomes unnecessary. Since one reference image is acquired for each shooting, there is no need to update during operation, and there is no need to issue an update instruction. On the other hand, in shooting for acquiring and storing moving images, in many cases, it is rare to execute continuous image acquisition for a long time. For this reason, there is little possibility that the image quality is deteriorated without updating the reference image during the photographing operation. Although the operations from S22 to S11, S12, and S13 in the flowchart in FIG. 3 are performed in an extremely short time, there is a possibility that a blank frame is generated in an image to be recorded. Further, in the photographing operation, there is an opportunity to make appropriate observations by making appropriate corrections before using the acquired image for diagnosis, and inconvenience does not easily occur without correction in real time.

  On the other hand, in the case of image acquisition by fluoroscopic operation used for diagnosis in real time, the reference image is updated at an appropriate timing in real time in combination with being operated continuously for a long time, thereby maintaining high reproducible image quality. The benefits are great. For this reason, in the X-ray image diagnostic apparatus according to the present embodiment, when the imaging mode and the fluoroscopic mode are used separately, the reference image may be updated only in the fluoroscopic mode. As a result, in the imaging mode, by not updating the reference image, it is possible to omit the calculation related to the image processing, and it is possible to execute accurate image processing in the fluoroscopic mode.

<< Embodiment 2 >>
The X-ray image diagnostic apparatus according to the present embodiment will be described by focusing on characteristic points different from those of the first embodiment. The X-ray diagnostic imaging apparatus according to the present embodiment is the same as the X-ray diagnostic imaging apparatus described in the first embodiment with respect to the system configuration of the apparatus and the basic fluoroscopic operation flow.

  FIG. 4 is an example of an image acquisition timing chart of the X-ray diagnostic imaging apparatus according to the present embodiment. FIG. 4 shows temporal changes in the X-ray irradiation operation and the image acquisition operation in a predetermined period during the fluoroscopic operation in the flowchart of FIG. In FIG. 4, the horizontal axis indicates time, 201 indicates switching between the ON and OFF states of X-ray irradiation, and 202 indicates switching between ON and OFF states of image acquisition.

  While the operation is continuing, the X-ray irradiation is normally ON and is in a state 201a in the figure. Image acquisition is performed at a constant cycle, and an ON state represented by 202a and an OFF state represented by 202b in the figure are repeated. The X-ray detected / acquired image in the ON state is finally displayed on the image display unit 170 through the process as described above, and the display is updated every time the OFF state comes in a certain cycle. It is recognized by the user as a continuous fluoroscopic image. Image acquisition continues to be ON and OFF until it is determined that fluoroscopy is completed in S20 of the flowchart in FIG.

  Here, when the reference image update is issued, that is, when it is determined in S19 of the flowchart in FIG. 3 that the update is issued, the X-ray irradiation is stopped in S22, and the transition is made from 201b to 201c. . In addition, X-ray irradiation is started in S13, thereby causing a state transition from 201d to 201e. On the other hand, image acquisition repeats ON and OFF as before. When the operation is performed with such timing control, the image acquired when the X-ray irradiation is ON is a normal fluoroscopic image, whereas the image acquired when the X-ray irradiation is OFF is the subject. Is an image that does not include information of X-rays transmitted through the. That is, the image reflects dark current data. Therefore, the image data obtained here can be used for subsequent image correction by overwriting and saving as the reference image. However, an image acquired at a timing including both the X-ray irradiation ON state and the X-ray irradiation OFF state during the image acquisition timing cannot be used as a fluoroscopic image or a reference image. That is, the image acquired in the portion 202g in FIG. 4 cannot be used as a fluoroscopic image or a reference image.

  On the other hand, 202i in FIG. 4 is a timing including only the X-ray irradiation OFF state, so that it can be used as a reference image, and this data is stored. In this example, a single image acquisition of 202i is used for acquiring the reference image. However, if this is repeated, acquisition of image data is repeated a plurality of times, and they are averaged and used as a reference image. A stable reference image can be acquired.

  When the acquisition of the reference image is completed as described above (S11 and S12 in FIG. 3), X-ray irradiation is started (S13 in FIG. 3), and a transition is made as indicated by a portion 201d in FIG. Thereafter, repeated image acquisition is performed in the same manner as described above, and the fluoroscopic operation is continued. However, an image acquired before the state of rise 201e when X-ray irradiation is turned on, that is, an image acquired at a timing of 202k, cannot be used as a fluoroscopic image or a reference image as in the case of 202g. That is, the image should be displayed as a perspective image after the image acquired at the timing of 202 m. The image obtained at the timing of 202 m is displayed as a result of using the newly updated reference image. By performing image correction using a new reference image, even when there is a temperature change in the X-ray detector 101, optimal image correction according to the situation can be performed. As a result, an image with excellent reproducibility can be displayed even during continuous fluoroscopic operations, and the accuracy of image diagnosis can be improved.

  By the way, in the example of FIG. 4, it has been described that the images of the three times 202g, 202i, and 202k cannot be used as the fluoroscopic images. However, it is not preferable that the fluoroscopic images displayed on the image display unit 170 are interrupted. If an image corresponding to the reference image or an image with no signal is displayed even for a very short time, the user feels uncomfortable. Therefore, in the diagnostic imaging apparatus according to the present embodiment, the last image effective as a fluoroscopic image, that is, the image acquired in 202e is repeatedly displayed (last image hold). This is performed until X-ray irradiation rises and a valid image is acquired as a fluoroscopic image at a timing of 202 m in FIG. Thereby, it is possible to configure an X-ray diagnostic imaging apparatus that does not give the user a sense of incongruity and can be used more comfortably.

  In the example of FIG. 4, the timing for switching X-ray irradiation ON and OFF may be controlled in order to suppress the number of images that cannot be used as fluoroscopic images or reference images. For example, when an update instruction is issued, X-ray irradiation is not temporarily stopped immediately, but after the update instruction, X-ray irradiation is temporarily performed at a timing when image acquisition is turned off, for example, at 202h. You may make it stop automatically. Thereby, the quantity of the image which cannot be used as a fluoroscopic image can be reduced.

<< Other Embodiments >>
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

Claims (6)

It is connected to a generating means for generating X-rays and a detecting means for detecting the X-rays and outputting image data corresponding to the detected X-rays, and is obtained from the detecting means in a state where the generating means does not generate X-rays. An image processing apparatus that corrects image data corresponding to the X-rays and outputs an X-ray image using the obtained image data as a reference image,
Obtaining means for obtaining a measurement result of the temperature around the detecting means;
While the X-ray is continuously generated from the generating means and the X-ray image is acquired from the detecting means, the generation of X-rays is temporarily stopped when the amount of change in temperature becomes larger than a predetermined value. Control means for controlling the generating means to:
Updating means for updating the reference image using image data acquired from the detection means while the generation means temporarily stops generation of X-rays;
An image processing apparatus comprising:   The image processing apparatus according to claim 1, wherein the control unit uses the different predetermined value depending on whether the acquired change in the temperature is an increase or a decrease.   The image processing apparatus has at least two operation modes of a photographing mode for recording and storing the corrected image and a perspective mode for displaying the image in real time, and the updating unit includes the perspective mode. The image processing apparatus according to claim 1, wherein the update of the reference image is executed only in step 1. It further comprises display means for displaying the corrected image data,
The display means displays an X-ray image output while the generating means generates X-rays while the generating means temporarily stops generating X-rays. Item 4. The image processing apparatus according to any one of Items 1 to 3. It is connected to a generating means for generating X-rays and a detecting means for detecting the X-rays and outputting image data corresponding to the detected X-rays, and is obtained from the detecting means in a state where the generating means does not generate X-rays. An image processing method in an image processing apparatus that uses the obtained image data as a reference image, corrects the image data according to the X-rays, and outputs the corrected X-ray image,
An acquisition unit acquiring a measurement result of a temperature around the detection unit;
When the control means continuously generates X-rays from the generating means and acquires an X-ray image from the detecting means, the generation of X-rays is generated when the amount of change in temperature becomes larger than a predetermined value. Controlling the generating means to temporarily stop;
Updating means for updating the reference image using image data acquired from the detection means while the generation means temporarily stops generation of X-rays;
An image processing method comprising:   The program for functioning a computer as each means with which the image processing apparatus of any one of Claim 1 to 4 is provided.

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