JP2007054359A - X-ray image diagnosing system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray image diagnosing system which prevents a post-generated defect element from being overlooked, and can maintain a high picture quality. <P>SOLUTION: This device is equipped with: an X-ray source 2; an X-ray flat surface detector 4; a defective element position recording section 9; a compensation processing section 10; an image processing section 11; a post-generated defective element detecting section 8; and a control section. In this case, the X-ray flat surface detector 4 is constituted by two-dimensionally arranging a plurality of X-ray detecting elements into a flat plate shape. The defective element position recording section 9 records the positional information of a defective element of the X-ray detecting elements which form the X-ray flat surface detector. The compensation processing section 10 performs various kinds of compensation processes including the compensation of the detection amount of the defective element by the detection amount of the X-ray detecting element at a vicinity position of the defective element and forms X-ray image forming data from the recorded positional information of the defective element. The image processing section 11 applies various kinds of image processes to the data which has been formed in the compensation processing section. The post-generated defective element detecting section 8 detects a post-generated defective element which grows later from the X-ray image which has been formed in the image processing section 11 or an already photographed clinical image. The control section updates and stores the position of the defective element which has been detected by the post-generated defective element detecting section in the defective element position recording section. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an X-ray image diagnostic apparatus that uses an X-ray flat panel detector composed of a plurality of X-ray detection elements as X-ray detection means, and in particular, detects defective elements that occur later on the X-ray flat panel detector. The present invention relates to an X-ray image diagnostic apparatus that detects and corrects pixel values of defective elements to form an X-ray image.

  In recent years, X-rays are converted into visible light proportional to the intensity of the X-rays by a phosphor, and the visible light is converted into an electrical signal using an X-ray flat panel detector composed of a plurality of pixels. An X-ray diagnostic imaging apparatus that obtains an X-ray digital image by converting the signal into a digital signal by an analog / digital (A / D) converter is used.

The image sensor of the X-ray flat panel detector preferably has no defective element, but is not practical because the manufacturing yield is low and the cost is high due to the number of pixels, the screen size, and the like.
Therefore, the defective element of the X-ray flat panel detector is detected in advance, the position of the detected defective element is stored, and the pixel of the defective element is determined by the pixel value of the element adjacent to the defective element at the stored position. The yield reduction is dealt with by obtaining the value by interpolation.

Furthermore, in addition to the defective element detected as described above, a new defective element is generated in the X-ray flat panel detector when clinically used.
This defective element is unread by the photodiode that converts the X-ray dose accumulated over a long period of time depending on the position of the element of the X-ray flat detector, that is, the X-ray into light and converts the converted light into electric charge. The defect element is newly generated from a period of use such as a difference in accumulated amount of charge over a long period of time or a secular change of the X-ray flat panel detector itself. This defect element is called a late defect element.

Conventionally, for the problem of such a late defect element, as described in Patent Document 1, a stationary object such as a phantom or acrylic, or nothing is placed in a medical facility for a certain period of time. This is dealt with by means of irradiating X-rays from a ray tube to detect the subsequent defective element and updating the defective element.
JP 2005-124613 A

However, the above prior art requires a special work for detecting a late defective element by bringing a dedicated phantom to a medical site, and this work is troublesome. Since this is not possible, the imaging throughput is reduced.
In addition, since the maintenance by the phantom is performed by determining the maintenance cycle, it is possible that a defective device may be overlooked because it cannot cope with a subsequent defective device generated during the maintenance cycle.

  The object of the present invention has been made in view of the above-mentioned problems, and saves the trouble of maintenance work for detecting a subsequent defective element to improve the photographing throughput and maintain high image quality by eliminating the oversight of the subsequent defective element. It is an object of the present invention to provide an X-ray diagnostic imaging apparatus that can do this.

  In order to solve the above problems, the present invention detects the subsequent defective element from clinical image data formed by an image processing unit of an X-ray image diagnostic apparatus, and is specifically achieved by the following means.

  (1) An X-ray flat panel detector for detecting X-rays irradiated by an X-ray source, wherein a plurality of X-ray detection elements for detecting the X-rays are two-dimensionally arranged in a flat plate shape, and Defect element position information storage means for storing position information of defective elements of the X-ray detection elements forming the X-ray flat panel detector, and subsequent detection of the positions of the subsequent defective elements generated at positions different from the defective elements A defective element detecting means; a control means for updating and storing the position of the subsequent defective element in the defective element position information storage means; a means for correcting the updated detection amount of the defective element; and the corrected In the X-ray diagnostic imaging apparatus comprising an image forming means for forming an X-ray image from a detected amount of a defective element and a detected amount detected by an X-ray detecting element other than the defective element, the subsequent defective element detecting means X-ray image obtained clinically or the image Comprises means for detecting a defective element from the X-ray image formed by the forming means, stores the position of the detected defective elements Update to the defective element position information storage means by said control means.

  (2) means for detecting a defective element from the X-ray image, position associating means for associating the position of each pixel of the X-ray image and the position of the X-ray detection element forming the X-ray plane detector; A reference value setting unit that sets a reference value of each pixel value of the X-ray image data, and a difference between the pixel value of each pixel of the X-ray image associated by the position association unit and the reference value is obtained. A difference calculating means, a threshold setting means for setting a threshold value of a difference calculated by the difference calculating means, and a pixel value of the difference calculated by the difference calculating means and a threshold value set by the threshold setting means to compare the X And a defective element position detecting means for detecting the position of the defective element of the line detecting element.

  (3) The reference value set by the reference value setting means and the threshold value set by the threshold setting means correspond to the positions associated by the position association means within a predetermined region of the X-ray image. Set based on pixel value.

By configuring in this way, subsequent defect elements generated in the X-ray flat panel detector are detected from clinically obtained X-ray images and X-ray images formed by the image processing unit of the present X-ray image diagnostic apparatus. As a result, there is no need to bring a dedicated phantom to the medical site for inspection as in the past, which greatly reduces the labor required for the maintenance work of the X-ray flat panel detector. This improves the throughput of clinical imaging without interruption of imaging.
In addition, using the clinical X-ray image formed by the image processing unit, it is possible to update the subsequent defective elements each time an image is taken, and an image can always be formed with corrected pixel values. High quality X-ray images can be maintained.

(4) The reference value set by the reference value setting unit is an average value or a median value of the pixel values of the X-ray image associated by the position association unit, and is set by the threshold setting unit. The threshold value is set by the average value or the median value and a preset magnification.
The set magnification can be determined from factors of image quality evaluation, such as whether or not the artifact of the obtained image can be recognized. Therefore, when the artifact or the like is recognized, the image quality is improved by changing the magnification. be able to.

(5) The predetermined area of the X-ray image is an area obtained by dividing the X-ray image area into a plurality of areas, and defective elements are detected by the defective element detection means for each of the divided image areas. The defective elements of the X-ray detection elements are detected by detecting and taking the logical product of the defective elements detected in the plurality of image areas.
(6) The plurality of divided image regions are provided with regions that overlap the divided adjacent regions.

  In this way, the X-ray image area is divided, an overlapping area is provided between the divided adjacent areas, and the logical product of the defective elements detected in the plurality of image areas is calculated, so that the adjacent region of interest is obtained. In addition, the dense defect elements that are spread over are not overlooked, and the defect element candidates due to the structure of the object are removed, thereby improving the reliability of the defect element detection.

(7) The predetermined area is an area smaller than the area where the previous defective element was detected.
Thereby, since the defective element in the area where the previous defective element was detected is known, the defective element detection time can be shortened by setting an area smaller than the defective element detection area to be performed next time. .

(8) The predetermined region of the X-ray image is a region in which an X-ray irradiation region from the X-ray source is limited.
Thereby, it is possible to prevent erroneous determination of defective element candidates due to a sharp change in pixel value at the boundary between the inside and outside of the X-ray irradiation field.

(9) The X-ray images are a plurality of X-ray images formed by the image forming unit by photographing different photographing objects.
(10) A means for notifying that the defective element position is updated when the defective element position is updated is provided.

As described above, according to the present invention, since the subsequent defective element is detected using the clinical image and the defective element is updated, the pixel value of the updated defective element is corrected and image processing is performed. The maintenance work for detecting a subsequent defective element by a conventional phantom is unnecessary, and the imaging throughput can be improved.
In addition, by updating the subsequent defect element using the captured clinical image every time the image is taken, the maintenance period of the detection of the subsequent defect element is greatly shortened. Captured images can be maintained.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing a schematic configuration of the X-ray image diagnostic apparatus of the present invention.
The X-ray diagnostic imaging apparatus of the present invention includes an X-ray tube 2 that irradiates a subject 1 with X-rays, and an X-ray diaphragm that restricts the X-rays emitted from the X-ray tube 2 to the irradiation field of the subject 1 3 and an X-ray flat detector 4 for detecting X-rays transmitted through the subject 1, and until the X-ray image is emitted from the X-ray tube 2 to display an X-ray image of the imaging region of the subject 1 A system controller 5 for controlling the entire apparatus, an X-ray plane detector controller 6 for controlling the X-ray plane detector 4, and an image for collecting X-ray image data detected by the X-ray plane detector 4 The collection unit 7, the subsequent defect element detection unit 8 that detects the defect element of the X-ray flat panel detector caused by the X-ray irradiation condition or secular change later, and the defect element that records the position information of the defect element Correction of pixel values of defective elements recorded in the defective element position recording unit 9 in the image data collected by the position recording unit 9 and the image collecting unit 7; A correction processing unit 10 that corrects dark current, gain, and the like of the X-ray flat panel detector 4, and an image processing unit that performs various processes such as various filter processes on the image data corrected by the correction processing unit 10. 11 and a display unit 12 for displaying an image processed by the image processing unit 11.
Here, the defective element of the X-ray flat detector 4 is also called a defective pixel because it appears in the resulting X-ray image.

  As shown in FIG. 2, the X-ray flat panel detector 4 includes an X-ray detection substance layer 4a that converts X-rays transmitted through the subject 1 into electric charges, and a TFT (Thin) that reads out the electric charges and converts them into electric signals. An X-ray detection element array 4b composed of transistors, an amplification circuit 4c for amplifying the electric signal converted by the TFT transistor, and an integration circuit 4d for integrating the electric signal amplified by the amplification circuit 4c, A line control circuit 4e for controlling the timing of reading out the charges converted by the X-ray detection material layer by a TFT transistor, and an A / D converter 4f for converting an analog signal output from the integration circuit 4d into a digital signal It consists of.

This X-ray flat panel detector 4 has an offset value called dark current detected by the X-ray flat panel detector 4 when no X-ray is incident, and this offset value is caused by a leakage current for each pixel. It varies depending on the ambient temperature and integration time.
Further, the gains (ratio of input signals to output signals of pixels) of all the pixels (pixels) constituting the X-ray flat panel detector 4 are not the same and vary.
Further, the X-ray flat detector 4 also has a defective element. As described in [Background Art], since the manufacturing yield is low and the cost is high due to the number of pixels, the screen size, etc., the defective elements of the X-ray flat panel detector are extracted in advance by inspection, and this extraction is performed. The position of the defective element is stored in advance, and the pixel value of the defective element is obtained by interpolation using the pixel value of the element adjacent to the defective element at the stored position.
Furthermore, late defective elements also occur depending on the X-ray conditions used and changes with time.
Thus, since the X-ray flat detector 4 has dark current, gain variation between X-ray elements, defective elements that occur during manufacture of the X-ray flat panel detector, and late defective elements that occur during practical use, Correction processing is required to cope with these.

  The X-ray flat panel detector control device 6 reads the X-ray detection signal detected by the X-ray flat panel detector 4, and inputs the read X-ray detection signal to the image acquisition unit 7. This is a device that performs readout control of the line plane detector 4.

Next, processes such as dark current correction, pixel gain correction, and defect element pixel value correction that are corrected by the correction processing unit 10 will be described.
In the X-ray diagnostic imaging apparatus, calibration imaging is performed prior to normal imaging. This calibration imaging is performed to collect information for image calibration (also called correction), and is used to perform gain correction of the X-ray flat panel detector 4 on an image during normal imaging. The correction correction unit 10 corrects the X-ray image data collected by the image collection unit 7 using the collected data by collecting the gain correction image and the position information of the defective element.

FIG. 3 is a block diagram showing the configuration of the correction processing unit 10.
The correction processing unit 10 includes a dark current correction unit 10a that corrects the dark current of the X-ray flat panel detector 4, a gain information holding unit 10b that records the gain information, and a uniform subject (no subject is included). Gain correction unit 10c for correcting the variation in the output between the X-ray detection elements of the X-ray flat panel detector 4 obtained by radiating predetermined X-rays to the same, and defects in the X-ray flat panel detector 4 And a defective pixel correction unit 10d that corrects the pixel value of the element.

The correction processing unit 10 having such a configuration is obtained by the dark current correction unit 10a immediately before acquiring the captured raw image data from the captured raw image data (image data obtained by capturing the specimen for diagnosis) obtained by normal imaging. The dark current correction process is performed by subtracting the dark current data obtained without irradiating the X-ray.
The dark current correction data is subjected to gain correction and defective pixel correction. The gain information used for these corrections and the position information of the defective elements are objects having uniform X-ray transmittance, for example, 21 mm. Take an aluminum plate and obtain it in advance.

The gain information is shot so that a plurality of images are obtained in order to obtain, for example, 10 average images and obtain an image with less noise.
Specifically, for example, a 21 mm aluminum plate having a uniform X-ray transmittance is imaged under X-ray imaging conditions in which the voltage applied between the anode and cathode of the X-ray tube 2 is 70 kV, and the X-ray flat detector at this time Photographing is performed so that the average output of 4 is the average output level of clinical tests, for example, around 500 gradations.
The gain of the X-ray flat panel detector 4 is obtained from the image data obtained in this way, and is stored in the gain information holding unit 10b.

The gain information stored in the gain information holding unit 10b is acquired by the following procedure.
(1) For gain correction data, 10 21 mm aluminum plates are photographed as described above, and 10 sheets are added and averaged and dark current correction is performed.
(2) The average value N of the obtained dark current corrected images is obtained.
(3) The pixel value Pij of the obtained dark current corrected image is divided by the average value N.
Nij ＝ Pij / N
Nij is a pixel gain correction value for each pixel. Stored in the gain information holding unit 10b.
(4) The captured raw image of the clinical test is subjected to dark current correction processing by the dark current correction unit, and then gain correction processing is performed by multiplying the pixel correction value for each pixel of the gain information holding unit 10b.

Next, creation of a defective pixel map necessary for performing defective pixel correction of the image data that has been gain-corrected by the defective pixel correction unit 10d will be described.
The defective pixel map is created using the above-described gain corrected image data, FIG. 4 (a) shows a defective element extraction flow for creating a defective pixel map, and FIG. For example, an X-ray detection surface composed of 3000 pixels × 3000 pixels is shown, and defective pixels are detected by the following procedure.

(1) First, the upper left of the region on the X-ray detection surface shown in FIG. 4B is set as a defective pixel detection start pixel of the target pixel Pij (step S41).
(2) The average pixel value A of all the pixels is calculated for the obtained image data after the gain correction process, and 0.05 is set as the designated multiple N in advance for the average pixel value A (step S42). The designated multiple is a value determined from the obtained image data, and is determined based on whether it can be recognized as an artifact when observing a clinical image, for example. The designated multiple can be changed by an external input device (not shown) provided in the system control device 5, for example, according to the degree of image quality such as the artifact.
(3) It is determined whether or not the difference between the pixel value of the target pixel Pij and the average pixel value A of all pixels is greater than N × A (step S43).
(4) If the result of this determination is | target pixel value−average pixel value A |> N × A of all pixels, the target pixel Pij is determined to be a defective pixel, and the defective element position recording unit is determined using this pixel as a defective pixel. 9 is recorded (step S44).
(5) On the other hand, if | target pixel value−average pixel value A | <N × A of all pixels, it is determined as a normal pixel whether or not the discrimination for all the X-ray detection surface regions has been completed (step S45). .
(6) If the determination for all the X-ray detection surface areas is not completed in step S45, the pixel is moved (step S46), and the process returns to step S43 to determine the moved pixel.
(7) The determination is made for all the X-ray detection surface areas, and the determination of the position of the defective pixel, that is, the defective element is completed.

In this way, defective elements are detected, but the target gain correction processed X-ray image (for example, an image of a 21 mm aluminum plate) has been sufficiently corrected for shading by the gain correction processing. Then, an element of a pixel whose output value is shifted by 5% from the total average value is regarded as a defective element.
In addition, the output of each pixel detected by the X-ray flat panel detector 4 depends on the X-ray dose, and the defective pixel output is a pixel that is not output at all, a pixel that always outputs a large digital signal, or an intermediate value There are pixels that output.
Therefore, the above-mentioned calibration is performed under various imaging conditions in the range of imaging conditions used clinically to detect defective pixels, and the OR of the defective pixels in the imaging conditions is taken to obtain defective pixels which are positional information of the defective pixels. A map is created and recorded in the defective element position recording unit 9.
In this case, if there is a defective element even under one X-ray condition, this element is assumed to be a defective element.

In addition to the defective element detected as described above, a new defective element is generated when used clinically.
This defective element is an X-ray dose accumulated over a long period of time depending on the position of the element of the X-ray flat panel detector 4, that is, the X-ray is converted into light, and the converted light is converted into electric charge and left unread on the photodiode. The defect element is newly generated from a period of use such as a difference in accumulated amount of the generated charge over a long period of time or a secular change of the X-ray flat panel detector itself. be called.

Also, unlike the aluminum plate with the uniform X-ray transmittance, the X-ray transmittance of the subject to be imaged in clinical practice is various, and all conditions that are the same as in clinical practice are just based on the difference from the average value of the pixel values of all pixels. It is not possible to specify a defective element.
Therefore, it is necessary to detect the subsequent defective element in clinical practice and update the position information of the defective element recorded in the defective element position recording unit 9.
That is, as described below, the present invention discriminates each pixel from the clinical image data formed by the image processing unit 11 to detect a defective element, and updates the position information of the defective element.

  Fig. 5 (a) shows a flowchart for detecting defective pixels from a clinical image, and Fig. 5 (b) shows an example of dividing an X-ray detection surface consisting of, for example, 3000 pixels x 3000 pixels into small areas, and detecting defective pixels in these small areas. Indicates the area.

The procedure for detecting defective pixels using clinical image data will be described below with reference to FIG.
(1) First, one image is selected from a plurality (L) of clinical images stored in a storage device (not shown), and the selected image data is used as a subsequent defect element detection unit. 8, the position of each pixel of the read X-ray image is associated with the position of the X-ray detection element forming the X-ray flat panel detector (step S51).
The means for associating the position of each pixel in the X-ray image with the position of the X-ray detection element forming the X-ray flat panel detector corresponds to the position association means in the claims.

(2) The X-ray detection surface of one selected image is divided into small areas, and a defective pixel detection start area is set (step S52). For example, in the case of an X-ray flat panel detector of 3000 pixels × 3000 pixels matrix shown in FIG.5 (b), 1/100 small area of the entire X-ray detection surface, that is, 30 pixels × 30 pixels small area, 1 When the pixel is 0.15 mm, the region of interest is set to 5 mm or less. This small area Q1.1 is set in the upper left of FIG. 5 (b), and this area is set as a discrimination start area.
In this case, if the small area is enlarged, the clinical image data is used as defective pixel detection target data, so that it is easily affected by the structure of the subject. Become more.
Therefore, since there are almost no diagnostic targets with a region of interest of 1 mm or less (corresponding to 7 pixels), the influence of image noise becomes large at 7 pixels x 7 pixels, so a small area of 15 pixels x 15 pixels or more is set. is there.

(3) For the set region of interest Q1.1 (30 pixels × 30 pixels), the defects recorded in the defect element position recording unit 9 detected using a 21 mm aluminum plate having a uniform X-ray transmittance The average value B of all the remaining pixels excluding the element (hereinafter, this defective element is referred to as “scratch” and this “scratch” map, that is, the defective pixel map may be referred to as “scratch coordinate”). Obtained (step S53).
This all-pixel average value B corresponds to the reference value in the claims.
For this average value B, for example, a specified multiple M of 0.5 (50%) is set in advance, but this may be changed as necessary.
(4) It is determined whether or not the difference between the pixel value of the target pixel qij and the average value B of the pixel values of the pixels in the small region Q1.1 is greater than M × B (step S54).
The calculation of the difference between the pixel value of the target pixel qij and the average value B of the pixel values of the pixels in the small area Q1.1 corresponds to a difference calculation unit in the claims, and the M × B is a claim. Corresponds to the threshold value.
(5) As a result of this determination, if | the pixel value of the target pixel qij−the average pixel value B of the small region Q1.1 |> M × B, the subsequent defective element detection unit 8 with the target pixel qij as a defective pixel candidate (Step S55).
(6) On the other hand, if | the pixel value of the target pixel qij−the average pixel value B of the small region Q1.1 | <M × B, the pixel is a normal pixel, and all of the set small regions of 30 pixels × 30 pixels It is determined whether or not the determination for the pixel is completed (step S56).

(7) If discrimination for all the pixels in the small area is not completed in step S56, the pixel is moved (step S57), and the process returns to step S54 to discriminate the moved pixel.
(8) When all the pixels in the set small area Q1.1 have been discriminated, it is determined whether or not the entire X-ray detection surface of 3000 pixels × 3000 pixels has been scanned (step S58).
(9) When not scanning the entire X-ray detection surface, as shown in FIG.5 (b), move to the right by half 15 pixels from the small area Q1.1 to the next small area Q1 .2 is set (step S59), the process returns to step S53, and the defective pixel is determined for the newly set pixel in the small region Q1.2 in the same manner as described above.
As described above, the small region Q1.1 and the small region Q1.2 are discriminated by overlapping by 15 pixels so as not to overlook dense defective pixels straddling adjacent regions of interest.

(10) In step S59, small areas are sequentially set to discriminate defective pixels.If the pixel cannot move around the X-ray detection surface, the region of interest protrudes as shown in FIG. Move by the amount that is not, return to the left column, and shift down by half the region of interest size (15 pixels).
(11) The target region of interest (small region) for the defective pixel determination set in this way is sequentially shifted to determine whether or not the plurality of (L) clinical image data of the different regions have been determined. However, if the determination is not completed, the process returns to step S51 to determine the next clinical image data.
(12) When the defective pixels are determined for all of the read L clinical images, the logical product of the defective element candidates is calculated for these L clinical images.
Thus, the logical product of the defective element candidates is taken in order to increase the reliability of the defective element detection except for the defective element candidates due to the structure of the subject.

(12) As a result of the logical product operation of the defective element candidate, the logical product outputs a subsequent defective element, the coordinates of which are registered as “scratches”, and the position of the defective element recorded in the defective element position recording unit 9 Update information.
(13) The defective element candidate in the case where the same coordinates are indicated even if the clinical inspection object is changed is determined as a new defective element, and the defective element position recording unit 9 is overwritten to update the defective element position information.

  Note that when overwriting (updating) a defective element candidate, a warning may be displayed on the display unit 12, and it may be left to the operator's decision whether to update the defective pixel map.

  Further, if the size of the region of interest is small, noise may increase and the discrimination accuracy may decrease, but noise can be reduced by increasing the number of clinical images used for discrimination (for example, 100 images).

  Furthermore, although the average value is used in the determination of the defective pixel, if there is a possibility that the average value may be dragged and shifted due to a relatively large X-ray shield in the region of interest in clinical practice, A median value may be used instead.

If the X-ray stop 3 is present, the pixel value changes sharply at the boundary between the inside and outside of the irradiation field restricted by the X-ray stop, so that it may be erroneously determined as a defective pixel candidate.
In this case, only the X-ray irradiation field region restricted by the X-ray diaphragm 3 is determined using the position information of the left and right diaphragm blades (not shown) of the X-ray diaphragm 3 based on the system information from the system control device 5. I do.

The X-ray irradiation field area is identified by obtaining a geometric condition from the distance between the focal point of the X-ray tube 2 and the X-ray flat detector 4 and the position information of the stop blades of the X-ray stop 3, and the X-ray flat detector This is possible by calculating the X-ray irradiation area on 4.
The position information of the diaphragm blades of the X-ray diaphragm 3 is provided in the image processing unit 9 under the control of a central processing unit CPU (not shown) set in the system controller 5 and provided in the system controller. Sent to the omitted field recognition circuit.
The position information of the X-ray diaphragm blades sent to this irradiation field recognition circuit, the distance D between the focal point of the X-ray tube 2 and the X-ray plane detector 4, and the X-ray emission angle a when X-rays are irradiated Therefore, the X-ray irradiation width W on the X-ray flat detector 3 can be obtained by calculation with W = 2 × D × tan (a / 2). A defective element may be detected in a region determined from the line irradiation width W.

  Furthermore, since the predetermined area for detecting the subsequent defective element is known as the defective element in the area where the previous defective element was detected, by setting an area smaller than the defective element detection area to be performed next time The detection time of defective elements can be shortened.

In the X-ray diagnostic imaging apparatus of the present invention configured as described above, the X-ray irradiated from the X-ray tube 2 passes through the subject 1 and enters the X-ray detection element array 4b in the X-ray flat detector 4. To do. The X-rays incident on the X-ray detection element array 4b have transmission image information, and the X-rays are converted into electric charges and read by the line control circuit 4e by a read control signal from the X-ray flat panel detector control device 6. It is read at the timing and amplified by the amplifier circuit 4c.
The amplified analog electric signal is integrated by the integrating circuit 4d, converted into a digital signal by the A / D converter 4f, and sequentially transferred to the image collecting unit 7.

The digital signal transferred to the image acquisition unit 7 is darkened by subtracting the dark current data acquired immediately before shooting from the captured raw image data collected in the image acquisition unit 7 by the dark current correction unit 10a of the correction processing unit 10. Perform current correction processing.
The dark current correction processed image data is gain corrected using the gain information stored in the gain information holding unit 10b by the gain correction unit 10c, and the image data subjected to the gain correction processing is the defective pixel correction unit 10d. Then, defective pixel correction processing is performed.
As described above, the defective pixel correction processing performed by the defective pixel correction unit 10d detects the subsequent defective elements using the clinical image data that has been captured in advance by the subsequent defective element detection unit 8, and detects the detected defects. The element is input to the defective element position recording unit 9, the position information of the defective element recorded in the defective element position recording unit 9 is updated, and the pixel value of the updated defective element is corrected.

  The captured image data that has been subjected to dark current correction, gain correction, and defective pixel correction in this way is subjected to image enlargement / reduction and various types of filter processing by the image processing unit 11, and X-rays are displayed on the screen of the display unit 10. Display the captured image.

As in the above-described embodiment, the X-ray image diagnostic apparatus of the present invention using an X-ray flat panel detector is clinical image data in which a subsequent defective element generated in the X-ray flat panel detector is processed by the image processing unit 9. Therefore, there is no need to bring a dedicated phantom to the medical site for inspection as in the prior art, and this greatly reduces the labor required for maintenance work of the X-ray flat panel detector.
In addition, since the maintenance by the conventional dedicated phantom is performed by determining the maintenance cycle, it is not possible to cope with the late defective element generated during the maintenance cycle.
On the other hand, in the present invention, using the clinical image data, it is possible to update the subsequent defective element each time an image is taken, so that an image can always be formed with corrected pixel values. An X-ray diagnostic imaging apparatus with high image quality and high reliability can be provided.

1 is a schematic diagram showing a schematic configuration of an X-ray image diagnostic apparatus according to the present invention. The figure which shows the structure of the X-ray plane detector used for the X-ray image diagnostic apparatus of this invention. The figure which shows the structure of the correction process part of the X-ray image diagnostic apparatus by this invention. The figure which shows the defective pixel map preparation flow figure and X-ray detection surface of the X-ray plane detector used for the X-ray image diagnostic apparatus of this invention. The figure which shows the flowchart which detects the subsequent defect element of the X-ray plane detector used for the X-ray image diagnostic apparatus of this invention, and a defect element detection area.

Explanation of symbols

  1 Subject, 2 X-ray tube, 3 X-ray diaphragm, 4 X-ray flat panel detector, 4a X-ray detection material layer, 4b X-ray detection element array, 4c amplification circuit, 4d integration circuit, 4e line control circuit, 4f Analog / digital converter (A / D converter), 5 system controller, 6 X-ray flat panel detector controller, 7 image acquisition unit, 8 subsequent defect element detection unit, 9 defective element position recording unit, 10 correction processing unit , 10a Dark current correction unit, 10b Gain information holding unit, 10c Gain correction unit, 10d Defective pixel correction unit, 11 Image processing unit, 12 Display unit

Claims (3)

  An X-ray flat panel detector for detecting X-rays irradiated by an X-ray source, wherein a plurality of X-ray detection elements for detecting the X-rays are two-dimensionally arranged in a flat plate shape, and the X-ray plane Defect element position information storage means for storing position information of defective elements of the X-ray detection elements forming the detector, and subsequent defect element detection for detecting positions of the subsequent defect elements generated at positions different from the defect elements Means, control means for updating and storing the position of the subsequent defective element in the defective element position information storage means, means for correcting the detected amount of the updated defective element, and correction of the corrected defective element An X-ray diagnostic imaging apparatus comprising: an image forming unit that forms an X-ray image from a detection amount and a detection amount detected by an X-ray detection element other than the defective element; From the X-ray image obtained in Recessed comprises means for detecting a device, X-rays image diagnosis apparatus characterized by storing the position of the detected defective elements to update the defective element position information storage means by said control means.   The X-ray image diagnosis apparatus according to claim 1, wherein the clinically obtained X-ray image is an X-ray image formed by the image forming unit.   The means for detecting a defective element from the X-ray image includes a position associating means for associating the position of each pixel of the X-ray image with the position of the X-ray detection element forming the X-ray flat panel detector, and the X-ray image Reference value setting means for setting a reference value for each pixel value of image data, and difference calculation means for obtaining a difference between the pixel value of each pixel of the X-ray image and the reference value associated by the position association means And a threshold value setting means for setting a threshold value of the difference calculated by the difference calculation means, a pixel value of the difference calculated by the difference calculation means and a threshold value set by the threshold value setting means to compare the X-ray detection element The X-ray image diagnostic apparatus according to claim 1, further comprising: a defective element position detecting unit that detects a position of the defective element.

Images