JP4560175B2 - Radiation imaging equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radiographic apparatus, and, for example, relates to a radiographic apparatus that is configured to directly detect an X-ray flat panel sensor and image a subject.
[0002]
[Prior art]
When a certain type of phosphor is irradiated with radiation (X-rays, α-rays, β-rays, γ-rays, electron beams, ultraviolet rays, etc.), a part of this radiation energy is accumulated in the phosphor, and visible light is visible in this phosphor. It is known that when irradiated with excitation light such as phosphors, phosphors exhibit stimulating luminescence according to the stored energy, and phosphors exhibiting such properties are stimulable phosphors (stimulable phosphors). be called. Using this stimulable phosphor, radiation image information of a subject such as a human body is temporarily recorded on the sheet of the stimulable phosphor, and this stimulable phosphor sheet is scanned with excitation light such as a laser beam to emit light. Light is generated, and the resulting stimulated emission light is photoelectrically read to obtain an image signal. Based on this image signal, a radiographic image of the subject is visualized on a recording material such as a photographic photosensitive material or a display device such as a CRT. Radiation image information recording / reproducing systems for outputting as described above have been proposed (Japanese Patent Laid-Open Nos. 55-12429, 56-11395, etc.).
[0003]
In recent years, apparatuses for taking X-ray images in the same manner using semiconductor sensors have been developed. These systems have the practical advantage of being able to record images over a very wide radiation exposure range compared to conventional radiographic systems using silver salt photography. That is, X-rays with a very wide dynamic range are read by photoelectric conversion means and converted into electrical signals. Using these electrical signals, a radiation image is converted into a visible image on a recording material such as a photographic photosensitive material or a display device such as a CRT. By outputting, a radiation image that is not affected by fluctuations in the radiation exposure amount can be obtained.
[0004]
[Problems to be solved by the invention]
The X-ray image is composed of 2000 × 2500 pixels or more with respect to a 43 × 35 cm half-cut detail image as the resolution increases. In general, an X-ray imaging apparatus has image processing means, and a processed image (QA image) obtained by performing image processing on a raw image by the image processing means becomes a diagnostic image and is output to a printer or a diagnostic PACS. At this time, the raw image is often temporarily stored on the magnetic disk of the photographing apparatus main body, and when the temporary area becomes full, the raw image is erased while referring to the photographing date. However, these raw images are meant to be an imaging log of the apparatus, and it has been desired to store as much raw image information as possible for the purpose of developing image processing parameters.
[0005]
On the other hand, as a prior art, an image storage device (server) has already been proposed that stores an image while changing the image compression rate based on the accompanying information of the image. It has the purpose as a reference image or an evidence image at the time of litigation, and is not log information of the device as proposed in the present invention. For example, in the case of an X-ray image, the entire surface of the sensor may not be irradiated with X-rays but may be shot with the X-rays narrowed down. However, images output to a printer or network may be irradiated with X-rays by image processing. Only the region that has been cut is an image cut out.
[0006]
The present invention has been made in view of such circumstances, and an object thereof is to perform efficient radiographic image processing using log information of the imaging apparatus main body.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, a radiographic imaging device of the present invention includes a radiographic image detection unit, a raw image storage unit that stores a raw image from the radiographic image detection unit, Based on the accompanying information of the raw image, the raw image is reduced, the reduced raw image is saved in the raw image storage means as a reduced raw image, and the reduced raw image is based on the auxiliary information and the reduced raw image limit. Management for saving the compressed reduced raw image in the raw image storage means and deleting the compressed reduced raw image from the raw image storage means based on the supplementary information and the compressed reduced raw image limit With means It is characterized by that.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows the main components of a radiographic imaging apparatus according to the first embodiment of the present invention. Reference numeral 501 denotes an X-ray flat panel sensor for imaging an X-ray distribution transmitted through a patient. In this embodiment, an amorphous sensor is used, and an equivalent circuit is shown in FIG.
[0009]
A sensor driving circuit (not shown) performs switching for transmitting a readout signal to the sensor and reading out the electric charge accumulated in each pixel. Similarly, the read electric charge is amplified by an amplifier and AD converted, transferred to the image management unit 503, and stored in the raw image storage device 502. Here, the raw image is not a pure raw image but a raw image obtained by correcting each pixel offset and gain of the sensor 501. Since the offset depends on the integration time of the sensor, it is not necessary to store an image including the offset. As for gain correction, since there is a possibility that the gain distribution varies depending on the temperature, a gain image or LOG conversion that is performed when gain correction is performed is used as a raw image. However, the gain correction image is taken at a cycle of one day, one week, or one month, but this is separately stored as a past log. In the present invention, this gain correction image is also reduced or reduced and compressed as past log information.
[0010]
The image management unit 503 includes an imaging request receiving circuit 504 that receives an imaging request from the radiation information system 507, an image reduction unit 505, and an image compression unit 506.
[0011]
FIG. 2 shows an imaging request list input to the radiation information system 507 or transferred from a hospital information system (not shown) to the radiation information system 507. Here, a request list for June 23 and June 24 is displayed. When the shooting on June 24 is completed, the photographed image list in the image management means 503 is as shown on the right.
[0012]
Assume that the size of the raw image of the apparatus shown in this embodiment is 2000 × 2500 × 16 bits and 10 Mbytes, and the storage capacity of the raw image storage device 502 is 120 Mbytes. When the image management unit 503 completes the shooting for June 23, the image management unit 503 stores the raw images related to the 10 images for 23 days in the original size.
[0013]
At the time of shooting on the 24th, the free space of the raw image storage device 502 is 20 Mbytes, and at the time when Iwate Ikuko started shooting, the image for June 23 was not reduced. Turns out to be unable to save three raw images of Iwate.
[0014]
The image management unit 503 reduces the image of Akita taken on June 23 at this time. Although it is conceivable to reduce one of Akita's three images, in this embodiment, the storage status of images classified into the same study of the same patient is changed at the same time. Specifically, each side is compressed to 1/10 by the image reduction means 505, and reduced and converted into a 200 × 250 pixel raw image. The reduction ratio can be changed by setting means (not shown).
[0015]
The size of the reduced image is 100 Kbytes, and the capacity of the raw image occupied by the raw image storage device 502 at the time when the reduction of the three images of Akita-san and the shooting of the three images of Mr. Iwate on the 24th is completed. The original image portion is 100 Mbytes, and the compressed raw image portion is 300 Kbytes. Similarly, when the next Machida-san's shooting starts, five of Tochigi-san on the 23rd are reduced, and when Machida-san's three shooting is completed, the capacity of the raw image occupied in the raw image storage device 502 is The original image portion is 80 Mbytes, and the compressed raw image portion is 500 Kbytes.
[0016]
If this process is repeated, there will be no area where the raw image can be stored in the original. In practice, image management is performed so that the reduced area of the raw image does not exceed a settable capacity. Specifically, if the reduced raw image is managed so as not to exceed 20 Mbytes, the raw image storage device 502 having a capacity of 120 Mbytes has 200 reduced images and 10 original images in the original size. It becomes manageable.
[0017]
Further, it is possible to further increase the number of stored raw images by performing an image compression process for performing redundancy compression without changing the resolution of the image with respect to the reduced image. Specifically, for a festival where the capacity of the reduced raw image exceeds 20 Mbytes by the image compression means 506, image compression of 1/20 is applied to a reduced image of 200 × 250 pixels and 100 Kbytes. And compressed to 5K bytes.
[0018]
However, if this is repeated, all the reduced raw images become compressed images, so that the area of the compressed reduced raw image is managed so as not to exceed 10 Mbytes. That is, the raw image storage device 502 having a capacity of 120 Mbytes can manage 2000 compressed reduced raw images, 100 reduced raw images, and 10 raw images in the original size. Further, for the portion of the compressed reduced raw image exceeding 10 Mbytes, further image compression is possible, but in this embodiment, the image is completely erased.
[0019]
The processing flow of the above image management means is shown in FIG.
[0020]
First, if there is a new photographing request in step S301, it is determined in step S302 whether or not the original size can be stored. If yes, the reduction / compression process is not performed (step S308).
[0021]
On the other hand, if the original size cannot be stored, a raw image with a low degree of requirement is determined as a reduced raw image in step S303, as determined from the accompanying information of the image.
[0022]
Next, in step S304, it is determined whether or not the capacity of the reduced raw image exceeds SL. If not, the process proceeds to step S308, and if it exceeds, the reduced raw image with a low degree of request is compressed based on the information attached to the image. A reduced and compressed image is formed (step S305).
[0023]
In step S306, it is determined whether or not the capacity of the compressed reduced raw image exceeds CL. If not, the process proceeds to step S308, and if it exceeds, the compressed reduced raw image with a low degree of request is determined based on the accompanying information of the image. The image is erased (step S307).
[0024]
In the above example, the reduction of the raw image is determined in units of patient studies, but may be determined in units of images. In addition, only the shooting date is shown as supplementary information of the image, but as information from the radiation information magazine system (RIS), the date and time when the doctor diagnosed the target image or the date and time when the doctor referred to the image was received, Based on these pieces of information, it may be determined in a storage mode whether to store the original size, the reduced image, or the compressed image.
[0025]
When the image management unit 503 is realized by a computer, the above image reduction and image compression are performed in the background so as not to affect the photographing of the apparatus.
[0026]
The whole X-ray imaging system of the present embodiment will be described with reference to FIG. 101 represents an X-ray room, 102 represents an X-ray control room, and 103 represents a diagnosis room. The overall operation of the X-ray imaging system is governed by the system control unit 110. The functions of the system control unit 110 are mainly described below, but the image management unit 503 shown in FIG. 1 is a partial function of the system control unit 110.
[0027]
The operator interface 111 includes a touch panel on a display, a mouse, a keyboard, a joystick, a foot switch, and the like. From the operator interface 111, setting of imaging conditions (still image, moving image, X-ray tube voltage, tube current, X-ray irradiation time, etc.), imaging timing, image processing conditions, subject ID, captured image processing method, etc. Although it can be done, most information is transferred from the radiation information system 507 and does not need to be entered separately. An important operation of the operator is a confirmation operation of the captured image. That is, it is determined whether the angle is correct, the patient is not moving, and the image processing is appropriate.
[0028]
Then, the system control unit 110 instructs the imaging control unit 214 that controls the X-ray imaging sequence to specify imaging conditions based on an instruction from the imager 105 or the radiation information system 507, and captures data. Based on the instruction, the imaging control unit 214 drives the X-ray generator 120, the imaging bed 130, and the X-ray detector 140, which are the radiation source 211, captures image data, transfers the image data to the image processing unit 10, and then the operator Raw data that has been subjected to designated image processing and displayed on the display 160 and at the same time subjected to basic image processing for offset correction, LOG conversion, and gain correction is stored in the external storage device 161.
The external storage device 161 includes the raw image storage device 502 shown in FIG. 1. The external storage device 161 stores a processing program, a stored image list, a gain correction image, and the like in addition to the raw image. The
[0029]
Further, the system control unit 110 performs re-image processing and playback display, transfer and store image data to a device on the network, display display, printing on a film, and the like based on an instruction from the photographer 105.
[0030]
Next, a description will be sequentially added following the flow of signals.
[0031]
The X-ray generator 120 includes an X-ray tube 121 and an X-ray diaphragm 123. The X-ray tube 121 is driven by a high voltage generation power source 124 controlled by the imaging control unit 214 and emits an X-ray beam 125. The X-ray diaphragm 123 is driven by the imaging control unit 214, and shapes the X-ray beam 125 so that unnecessary X-ray irradiation is not performed in accordance with the change of the imaging region. The X-ray beam 125 is directed to a subject 126 lying on an X-ray transmissive imaging bed 130. The imaging bed 130 is driven based on an instruction from the imaging control unit 214. The X-ray beam 125 is applied to the X-ray detector 140 after passing through the subject 126 and the imaging bed 130.
[0032]
The X-ray detection unit 140 includes a grid 141, a scintillator 142, a photodetector array 8, an X-ray exposure monitor 144, and a drive circuit 145. The grid 141 reduces the influence of X-ray scattering caused by passing through the subject 126.
The grid 141 includes an X-ray low absorption member and a high absorption member, and has, for example, a stripe structure of Al and Pb. Then, the grid 141 is vibrated based on an instruction from the imaging control unit 214 at the time of X-ray irradiation so as not to cause moire due to the relationship of the lattice ratio between the photodetector array 8 and the grid 141. The essential components of the X-ray flat panel sensor 501 shown in FIG. 1 are a scintillator 142, a photodetector array 8, and a drive circuit 145.
[0033]
In the scintillator 142, the host material of the phosphor is excited by high-energy X-rays, and fluorescence in the visible region is obtained by recombination energy when recombining. The fluorescence may be due to the host itself such as CaWo4 or CdWO4, or due to the emission center substance inactivated in the host body such as Csl: Tl or ZnS: Ag.
[0034]
A photodetector array 8 is disposed adjacent to the scintillator 142. This photodetector array 8 converts photons into electrical signals. The X-ray exposure monitor 144 monitors the X-ray transmission amount. The X-ray exposure monitor 144 may detect X-rays directly using a crystalline silicon light receiving element or the like, or may detect light from the scintillator 142. In this example, visible light (proportional to the X-ray dose) transmitted through the photodetector array 8 is detected by an amorphous silicon light-receiving element formed on the back surface of the photodetector array 8 substrate, and the information is sent to the imaging control unit 214. Based on the information, the image pickup control unit 214 drives the high voltage generating power supply 124 to cut off or adjust the X-rays. The drive circuit 145 drives the photodetector array (flat panel sensor) 8 under the control of the imaging control unit 214, and reads a signal from each pixel. The photodetector array 8 and the peripheral drive circuit 145 will be described in detail later.
[0035]
The image signal from the X-ray detection unit 140 is transferred from the X-ray room 101 to the image processing unit 10 in the X-ray control room 102. At the time of this transfer, the noise accompanying the generation of X-rays is large in the X-ray room 101, so that the image data may not be transferred accurately due to noise, so it is necessary to increase the noise resistance of the transfer path. It is desirable to use a transmission system having an error correction function or to use, for example, a shielded twisted pair by a differential driver or a transfer path by an optical fiber. The image processing unit 10 switches display data based on an instruction from the imaging control unit 214 (described in detail later). In addition, image data correction, spatial filtering, recursive processing, and the like can be performed in real time, and gradation processing, scattered radiation correction, DR compression processing, and the like can be performed.
[0036]
The processed image is displayed on the display 160 via the display adapter 151. In addition, a basic image that has been subjected only to data correction simultaneously with real-time image processing is stored in the high-speed storage device 161. As the high-speed storage device 161, a data storage device satisfying a large capacity, high speed and high reliability is desirable, and for example, a hard disk array such as RAID is desirable. Further, the image data stored in the high-speed storage device 161 is stored in the external storage device based on an instruction from the operator. At that time, the image data is reconstructed so as to satisfy a predetermined standard (for example, IS & C) and then stored in an external storage device. The external storage device is, for example, a magneto-optical disk 162, a hard disk in the file server 170 on the LAN, or the like.
[0037]
The X-ray imaging system can be connected to a LAN via a LAN board 163 and has a structure having data compatibility with the HIS. In addition to connecting a plurality of X-ray imaging systems to the LAN, a monitor 174 for displaying moving images / still images as images, a file server 170 for filing image data, an image printer 172 for outputting images to film, An image processing terminal 173 for performing complicated image processing and diagnosis support is connected. The present X-ray imaging system outputs image data according to a predetermined protocol (for example, DICOM). In addition, a real-time remote diagnosis by a doctor at the time of X-ray imaging can be performed using a monitor connected to a LAN.
[0038]
FIG. 5 shows an equivalent circuit of an example of the light detection array 8. In the following example, a two-dimensional amorphous silicon sensor will be described, but the detection element is not particularly limited. For example, the solid-state imaging element (charge-coupled element or the like) or an element such as a photomultiplier tube may be used. However, the function and configuration of the A / D converter are the same.
[0039]
Now, returning to FIG. The configuration of one element is composed of a light detection unit 21 and a switching TFT 22 that controls charge accumulation and reading, and is generally formed of amorphous silicon (α-Si) disposed on a glass substrate. In this example, 21-C in the light detection unit 21 may simply be a photodiode having a parasitic capacitance, or may include an additional capacitor 21-C in parallel to improve the dynamic range of the photodiode 21-D and the detector. It may be considered as a light detector. The anode A of the diode 21-D is connected to the bias wiring Lb which is a common electrode, and the cathode K is connected to the controllable switching TFT 22 for reading out the electric charge accumulated in the capacitor 21-C. In this example, the switching TFT 22 is a thin film transistor connected between the cathode K of the diode 21 -D and the charge readout amplifier 26.
[0040]
The switching TFT 22 and the signal charge are generated by operating the reset switching element 25 and resetting the capacitor 21-C, and then emitting radiation 1, thereby generating a charge corresponding to the radiation dose in the photodiode 21-D, and the capacitor 21-C. Accumulated in C. Thereafter, the switching TFT 22 and the signal charge again operate the reset switching element 25 to transfer the charge to the capacitor element 713. Then, the amount accumulated by the photodiode 21-D is read as a potential signal by the preamplifier 26, and the incident radiation dose is detected by performing A / D conversion.
[0041]
FIG. 6 is an equivalent circuit diagram showing a photoelectric conversion device arranged two-dimensionally. A photoelectric change operation in the case where the photoelectric conversion element shown in FIG. 5 is specifically expanded in two dimensions will be described.
[0042]
The pixels of the light detection array 8 are composed of about 2000 × 2000 to 4000 × 4000 pixels, and the array area is about 200 mm × 200 mm to 500 mm × 500 mm. In FIG. 9, the light detection array 8 is composed of 4096 × 4096 pixels, and the array area is 430 mm × 430 mm. Therefore, the size of one pixel is about 105 × 105 μm. Each pixel is arranged two-dimensionally by wiring 4096 pixels in one block in the horizontal direction and arranging 4096 lines in order vertically.
[0043]
In the above example, the 4096 × 4096 pixel photodetector array 8 is configured by a single substrate, but the 4096 × 4096 pixel photodetector array 8 includes four 2048 × 2048 pixels. It can also be composed of a photodetector. In the case where one photodetector array 8 is formed by four 2048 × 2048 detectors, there is an advantage that the yield is improved by making the detector array 8 divided.
[0044]
As described above, one pixel includes the photoelectric conversion element 21 and the switching TFT 22. 21- (1, 1) to 21- (4096, 4096) correspond to the photoelectric conversion element 21 described above, and the cathode side of the photodetecting diode is represented as K and the anode side is represented as A. Reference numerals 22-(1, 1) to 22-(4096, 4096) correspond to the switching TFT 22.
[0045]
The K electrodes of the photoelectric conversion elements 21- (m, n) in each column of the two-dimensional photodetector array 8 are common column signal lines for the columns by the source and drain conductive paths of the corresponding switching TFTs 22- (m, n). (Lc1 to 4096). For example, the photoelectric conversion elements 21- (1,1) to (1,4096) in the column 1 are connected to the first column signal wiring Lc1. The A electrodes of the photoelectric conversion elements 21 in each row are commonly connected to a bias power source 31 that operates the above-described mode through a bias wiring Lb. The gate electrode of the TFT 22 in each row is connected to the row selection wiring (Lr1 to 4096). For example, the TFTs 22- (1, 1) to (4096, 1) in the row 1 are connected to the row selection wiring Lr1. The row selection wiring Lr is connected to the imaging control unit 33 through the line selector unit 32. For example, the line selector unit 32 includes an address decoder 34 and 4096 switch elements 35. With this configuration, any line Lrn can be read. If the line selector unit 32 is configured in the simplest manner, the line selector unit 32 can be configured simply by a shift register used in a liquid crystal display or the like.
[0046]
The column signal wiring Lc is connected to a signal reading unit 36 controlled by the imaging control unit 33. 25 is a switch for resetting the column signal wiring Lr to the reference potential of the reset reference power supply 24, 26 is a preamplifier for amplifying the signal potential, 38 is a sample and hold circuit, 39 is an analog multiplexer, and 40 is an A / D. Each converter is represented. The signal of each column signal line Lrn is amplified by the preamplifier 26 and held by the sample hold circuit 38. The output is sequentially output to the A / D converter 40 by the analog multiplexer 39, converted into a digital value, and transferred to the image processing unit 10 (not shown).
[0047]
In the photoelectric conversion device of this embodiment, 4096 × 4096 pixels are divided into 4096 lines Lcn, and outputs of 4096 pixels per column are simultaneously transferred, and preamplifiers 26-1 to 4096 are transmitted through the column signal wiring Lc. The analog multiplexer 39 sequentially outputs the signals to the A / D converter 40 through the sample hold units 38-1 to 4096.
[0048]
In FIG. 6, although it is represented as if the A / D converter 40 is configured by one, in reality, A / D conversion is simultaneously performed in 4 to 32 systems. This is because it is required to shorten the reading time of the image signal without unnecessarily increasing the analog signal band A / D conversion rate.
[0049]
The accumulation time and the A / D conversion time are closely related. When A / D conversion is performed at high speed, the band of the analog circuit becomes wide and it becomes difficult to achieve a desired S / N. Therefore, it is required to shorten the image signal reading time without unnecessarily increasing the A / D conversion speed. For this purpose, A / D conversion may be performed using a large number of A / D converters 40, but in this case, the cost increases. Therefore, it is necessary to select an appropriate value in consideration of the above points.
[0050]
Since the irradiation time of the radiation 1 is 10 to 500 msec, it is appropriate to make the full screen capture time or the charge accumulation time on the order of 100 msec or slightly shorter.
[0051]
For example, in order to sequentially drive all the pixels and capture an image at 100 msec, the analog signal band is set to about 50 MHz. For example, when A / D conversion is performed at a sampling rate of 10 mHz, at least four A / D converters 40 is required. In this imaging apparatus, A / D conversion is simultaneously performed in 16 systems. The outputs of the 16 systems of A / D converters 40 are input to 16 systems of memory (FIFO and the like) (not shown) corresponding thereto. By selecting and switching the memory, the image data corresponding to one continuous scanning line is transferred to the subsequent image processing unit 10 or the memory. Thereafter, images and graphs are displayed on a display device such as a display.
[0052]
With the configuration as described above, since the raw image to be temporarily stored can be managed by reducing and compressing based on the auxiliary information of the image, the number of raw images as the log information of the apparatus can be increased.
[0053]
【The invention's effect】
As described above, according to the present invention, it is possible to perform efficient radiation image processing using log information of the imaging apparatus main body.
[Brief description of the drawings]
FIG. 1 is a diagram showing the configuration of an embodiment
FIG. 2 is a diagram showing a shooting request list
FIG. 3 is a flowchart showing processing of image management means.
FIG. 4 is a diagram showing a detailed configuration of an X-ray image capturing apparatus.
FIG. 5 is a diagram showing a sensor equivalent circuit
FIG. 6 is a circuit diagram of a flat sensor panel.
[Explanation of symbols]
505 Image reduction means
506 Image compression means

Claims (5)

Radiation image detection means;
Raw image storage means for storing a raw image from the radiation image detection means;
Based on the incidental information of the raw image, the raw image is reduced, the reduced raw image is saved in the raw image storage means as a reduced raw image,
Based on the auxiliary information and reduced raw image limit, compress the reduced raw image, save the compressed reduced raw image in the raw image storage means,
A radiographic imaging apparatus comprising: an image management unit that erases the compressed reduced raw image from the raw image storage unit based on the supplementary information and the compressed reduced raw image limit .   The radiological image capturing apparatus according to claim 1, wherein the incidental information is at least one of an elapsed day from the image capturing date, an elapsed day from the image diagnosis date, and an elapsed day from the last access date.   The radiographic image capturing apparatus according to claim 1, wherein a gain image for gain correction of an image captured by the radiographic image detecting unit is also managed by the image managing unit.   The radiographic image capturing apparatus according to claim 1, wherein the image management unit changes a management mode in units of patients or studies.   The radiographic image capturing apparatus according to claim 1, wherein image management of the image management unit is performed by background processing.

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