JP4615288B2 - Radiography equipment - Google Patents

Description

  The present invention relates to a configuration of a communication unit mainly in a radiographic apparatus including a communication unit that can wirelessly transmit an image signal obtained by radiography such as X-rays to an external device.

  Today, in radiography for X-rays and the like for medical diagnosis, an X-ray transmitted through a subject using a solid-state detector (with a semiconductor as a main part) as an X-ray image detection means. Various types of radiographic apparatuses that detect X-rays and obtain an image signal representing an X-ray image of a subject have been proposed and put into practical use.

  Various types of solid state detectors used in this apparatus have been proposed. For example, from the aspect of the charge generation process that converts X-rays into electric charges, the signal charge obtained by detecting the fluorescence emitted from the phosphor by the photoconductive layer when irradiated with X-rays is temporarily stored in the power storage unit. Then, a photo-conversion solid-state detector that converts the accumulated charge into an image signal (electrical signal) and outputs it, or collects signal charges generated in the photoconductive layer by irradiating X-rays with a charge collecting electrode. There is a direct conversion type solid-state detector or the like that temporarily accumulates in a power storage unit and converts the accumulated charge into an electric signal and outputs it. The solid state detector in this system has a photoconductive layer and a charge collecting electrode as main parts.

  From the aspect of the charge reading process for reading out the accumulated charges to the outside, a light reading method of reading light by irradiating a detector with reading light (reading electromagnetic waves), or as described in Patent Document 1 In addition, there is a TFT reading type that scans and reads out a TFT (thin film transistor) connected to the power storage unit.

  The applicant of the present application has proposed an improved direct conversion type solid state detector in Patent Document 2 and the like. The improved direct conversion type solid state detector is a direct conversion type and optical readout type, and exhibits photoconductivity by receiving recording light (X-ray or fluorescence generated by X-ray irradiation). Photoconductive layer for recording, a charge transport layer that acts as an insulator for charges having the same polarity as the latent image charge, and acts as a conductor for transport charges having a polarity opposite to that of the latent image charge A photoconductive layer for reading that exhibits photoconductivity by receiving irradiation of an electromagnetic wave for reading is laminated in this order, and is formed at the interface (electric storage unit) between the photoconductive layer for recording and the charge transport layer. A signal charge (latent image charge) carrying image information is accumulated. Electrodes (first conductive layer and second conductive layer) are laminated on both sides of these three layers. Further, the solid state detector in this system has a recording photoconductive layer, a charge transport layer, and a reading photoconductive layer as main parts.

When a digital image signal is obtained from the solid state detector as described above, the following procedure is generally performed. First, the latent image charge accumulated inside the solid state detector is output for each pixel, and an analog signal corresponding to the latent image charge is detected for each pixel by a charge amplifier or the like, and detected for each pixel. The analog signals are combined in the pixel arrangement order. Then, the composite analog signal is AD converted to generate a digital image signal.
JP 2000-244824 A JP 2000-105297 A

  By the way, in recent years, some radiation imaging apparatuses incorporating a solid state detector have been proposed that include a communication means capable of wirelessly transmitting a digital image signal obtained by radiation imaging to an external device. If such a communication means is built in the apparatus, noise due to a radio signal is superimposed on a small analog signal before AD conversion, and as a result, the S / N of the image signal is significantly reduced.

  Of course, if the wireless communication is not performed when the image signal is generated, the above problem can be solved, but the transfer speed is limited in the wireless communication, and it takes a considerable time to transmit the image signal. For this reason, such an aspect requires an increase in the shooting interval, which is not preferable in the shooting workflow.

  The present invention has been made in view of the above circumstances, and in a radiation imaging apparatus including a communication unit capable of wirelessly transmitting a digital image signal obtained by radiography such as X-rays to an external device, the image signal An object of the present invention is to provide a radiation imaging apparatus that suppresses the influence of wireless communication noise on the radiography.

  A radiation imaging apparatus according to the present invention includes a solid-state detector that records image information upon receiving irradiation of radiation carrying image information, outputs an analog signal representing the recorded image information, and an analog signal output from the solid-state detector. A radiographic apparatus comprising: an image signal processing unit that AD-converts a digital image signal; and a communication unit that wirelessly transmits the digital image signal output from the image signal processing unit to an external device, The communication frequency of the communication means is higher than the sampling frequency of AD conversion of the image signal processing means.

  Here, the “solid state detector” is a detector that detects radiation carrying image information of a subject and outputs an image signal representing a radiation image related to the subject, and directly or once converts incident radiation into light. An image signal representing a radiographic image related to the subject can be obtained by converting the charge into charges later and outputting the charges to the outside.

  There are various types of solid-state detectors. For example, from the aspect of the charge generation process that converts radiation into electric charge, the photoconductive layer detects fluorescence emitted from the phosphor when irradiated with radiation. The signal charge obtained in this way is temporarily stored in the power storage unit, the stored charge is converted into an image signal (electrical signal) and output, or the photoconductive layer is irradiated with radiation. The signal charge generated in step 1 is collected by the charge collection electrode, temporarily stored in the power storage unit, and the stored charge is converted into an electrical signal and output, or the direct conversion type solid state detector that reads the stored charge to the outside From the aspect of the reading process, a TFT reading method that scans and reads a TFT (thin film transistor) connected to the power storage unit, or an optical reading method that reads the reading light (electromagnetic wave for reading) by irradiating the detector with the reading light. Such as those of news, there is such an improved direct conversion type which is proposed in the Patent Document 2 filed by the present applicant that combines the direct conversion type and the optical readout type.

  In addition, as a communication method of the above communication means, various existing communication methods such as Bluetooth, HiSWANa (High Speed Wireless Access Network type a), HiperLAN, wireless 1394, wireless USB, and wireless LAN can be applied.

  A radiation imaging apparatus according to the present invention includes a solid-state detector that records image information upon receiving irradiation of radiation carrying image information, outputs an analog signal representing the recorded image information, and an analog signal output from the solid-state detector. A radiographic apparatus comprising: an image signal processing unit that AD converts a digital image signal to generate a digital image signal; and a communication unit that wirelessly transmits the digital image signal output from the image signal processing unit to an external device. Even if noise due to wireless communication is superimposed on an analog signal by making the communication frequency of the image signal higher than the AD conversion sampling frequency of the image signal processing means, the image signal processing means is higher than the AD conversion sampling frequency. High frequency signals are discarded without being AD converted, and only the original analog signal is substantially AD converted. Since so obtained the same signal, it is possible to reduce the influence on the digital image signal.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing an example of an X-ray (radiation) imaging system using an X-ray (radiation) imaging apparatus according to the present invention, FIG. 2 is a schematic configuration diagram of the X-ray imaging system, and FIG. FIG. 4 is a schematic configuration diagram of the image signal processing unit of the X-ray imaging apparatus.

  The X-ray imaging system includes a cassette type X-ray imaging apparatus 1 including a solid state detector 20 and the like, and an X-ray irradiation including an X-ray source 41 for irradiating the X-ray imaging apparatus 1 with X-rays. The apparatus 40 and an imaging control means 60 that performs imaging control and the like for the X-ray imaging apparatus 1 are configured.

  The imaging control means 60 performs imaging control with respect to the X-ray imaging apparatus 1 based on an instruction input from the photographer, and acquires an image signal from the X-ray imaging apparatus 1. 1 is provided with communication means 61. The imaging control means 60 is connected to a network such as DICOM (Digital Imaging and Communication in Medicine).

  As shown in FIGS. 1 and 2, the X-ray imaging apparatus 1 includes a solid-state detector 20 that is an imaging device, a control unit 30 that controls the operation of each unit of the X-ray imaging apparatus 1, and the solid-state detector 20. An image signal processing unit 32 for processing the signal output from the printer, a printed circuit board 27 including two frame buffers 33 and 34, a communication unit 28 for communicating with the imaging control unit 60, and a power source for each unit. A power supply unit 31 to be supplied is arranged.

  The solid state detector 20 includes a first conductive layer 24 made of an a-Si TFT on a glass substrate 25, a photoconductive layer 23 that generates electric charges upon receiving X-ray irradiation, and exhibits a conductivity. The conductive layer 22 and the insulating layer 21 are laminated in this order.

  The first conductive layer 24 is formed with a TFT corresponding to each pixel. The output 24 a of each TFT is connected to the IC chip 26, and the IC chip 26 is connected to the image signal processing unit 32 on the printed circuit board 27. It is connected.

  As shown in FIG. 4, the image signal processing unit 32 includes a plurality of detection channels 50 provided for each TFT output 24 a of the first conductive layer 24, and a multiplexer 51 that combines the outputs of the detection channels 50. And an AD conversion unit 52 that AD converts the analog signal output from the multiplexer 51.

  Each detection channel 50 divides the analog signal output from the charge amplifier circuit 50a for detecting charges and the analog signal output from the charge amplifier circuit 50a into two systems, and a low-pass filter for limiting these analog signals to a predetermined bandwidth. An (LPF) circuit 50b and a correlated double sampling (CDS) circuit 50c that performs correlated double sampling using two analog signals output from the low-pass filter circuit 50b.

  When the solid state detector 20 irradiates the photoconductive layer 23 with X-rays while an electric field is formed between the first conductive layer 24 and the second conductive layer 22, A charge pair is generated, and a latent image charge corresponding to the amount of the charge pair is accumulated in the first conductive layer 24. When reading the accumulated latent image charge, the TFTs of the first conductive layer 24 are sequentially driven to output an analog signal corresponding to the latent image charge corresponding to each pixel, and this analog signal is processed by image signal processing. The detection channel 50 in the unit 32 detects each pixel, and the analog signal detected for each pixel is combined by the multiplexer 51 in the pixel arrangement order. Then, the composite analog signal is AD converted by the AD conversion unit 52 to generate a digital image signal. The generated digital image signal is output from the image signal processing unit 32 to the communication unit 28 via the two frame buffers 33 and 34, and is transmitted to the photographing control unit 60 by the communication unit 28.

  Here, the relationship between the wireless communication frequency of the communication means 28 and the sampling frequency of the AD converter 52 will be described with reference to the drawings. FIG. 6 is a graph showing the relationship between the wireless communication frequency of the communication means 28 and the sampling frequency of the AD converter 52. The vertical axis represents gain (dB) and the horizontal axis represents frequency (Log display).

  The cut-off frequency fc of the low-pass filter circuit 50b is set to a frequency that is reduced by 3 dB on the high frequency side with respect to the maximum gain of the analog signal to be subjected to AD conversion. Further, the sampling frequency of the AD conversion unit 52 is set to a frequency that is reduced by 20 dB on the high frequency side with respect to the maximum gain of the analog signal to be AD converted.

  In the present embodiment, the communication frequency of the communication means 28 incorporated in the X-ray imaging apparatus 1 together with the solid state detector 20 is set higher than the sampling frequency of the AD conversion unit 52, thereby wirelessly communicating with an analog signal. Even if the noise due to the above is superimposed, the AD converter 52 cuts out the signal having a frequency higher than the sampling frequency of AD conversion without AD conversion, and substantially AD-converts only the original analog signal. Therefore, the influence on the digital image signal can be reduced.

  Specifically, when the sampling frequency of the AD conversion unit 52 is 100 MHz, the communication method of the communication unit 28 may be a wireless LAN (2.4 GHz or 5 GHz) that is a standard having a communication frequency of 100 MHz or more.

  Note that the communication method between the X-ray imaging apparatus 1 (communication means 28) and the imaging control means 60 (communication means 61) is not limited to the wireless LAN, and the communication frequency is equal to or higher than the sampling frequency of the AD converter. Any method can be applied as long as it is.

  Next, the operation of the X-ray imaging system will be described. FIG. 5 is a timing chart mainly showing the operation timing at the time of imaging of the X-ray imaging apparatus. In the figure, the signal transmission or reception indicates the operation of the X-ray imaging apparatus. All operations of the X-ray imaging apparatus are controlled by the control unit 30.

  First, when an imaging effect is input to the imaging control means 60 by the photographer, an imaging request signal is transmitted from the imaging control means 60 to the X-ray imaging apparatus 1.

  When receiving the imaging request signal, the X-ray imaging apparatus 1 transmits an imaging Ready signal to the imaging control unit 60, and when the imaging control unit 60 receives the imaging Ready signal, the X-ray imaging unit 1 receives the X-ray from the imaging control unit 60. A photographing start signal is transmitted toward the photographing apparatus 1.

  When the X-ray imaging apparatus 1 receives the imaging start signal, it applies a voltage to the solid state detector 20.

  In this state, when an exposure switch of the X-ray irradiation apparatus 40 is pressed by the photographer, X-rays are irradiated from the X-ray source 41 toward the X-ray imaging apparatus 1.

  When the X-ray imaging apparatus 1 is irradiated with X-rays, latent image charges carrying X-ray image information are accumulated in the solid state detector 20. Since the amount of accumulated latent image charge is substantially proportional to the X-ray dose transmitted through the subject 5, the latent image charge carries an electrostatic latent image.

  The X-ray imaging apparatus 1 stops the application of voltage to the solid state detector 20 after a predetermined time has elapsed and terminates imaging, and then outputs an analog signal corresponding to the latent image charge from the solid state detector 20, and the image signal processing unit 32 generates a digital image signal based on the analog signal. Digital image signals generated by the image signal processing unit 32 are output to the first frame buffer 33 in the order of generation.

  At the time when all the digital image signals constituting one X-ray image are output to the first frame buffer 33, the digital image signal stored in the first frame buffer 33 is the second frame buffer 34. And the solid state detector 20 is in the imaging ready state.

  The subsequent processing (transmission of a digital image signal to the imaging control means 60) can be performed in parallel with the next imaging processing. When the photographing request signal has already been received from the photographing control means 60 at the time when the photographing ready state is entered, the photographing ready signal is transmitted to the photographing control means 60 to start the above photographing processing, When the imaging request signal is not received from the imaging control unit 60, the standby state is kept until the imaging request signal is received.

  When the digital image signal is transferred to the second frame buffer 34, an image transfer request signal is transmitted to the shooting control means 60. When the image transfer request signal is received by the shooting control means 60, An image transfer Ready signal is transmitted from the imaging control means 60 toward the X-ray imaging apparatus 1.

  When receiving the image transfer ready signal, the X-ray imaging apparatus 1 transmits an image signal to the imaging control means 60 and then ends a series of processes.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above. For example, the solid state detector may be of an optical readout type. Further, the present invention can be applied to various X-ray imaging systems such as a breast image imaging apparatus in which an X-ray irradiation unit and an imaging table on which a cassette type X-ray imaging apparatus is loaded are integrally provided.

1 is a schematic diagram showing an example of an X-ray imaging system using a radiation imaging apparatus according to the present invention. Schematic configuration diagram of the X-ray imaging system Schematic configuration diagram of X-ray detector and solid state detector of the X-ray imaging apparatus Schematic configuration diagram of an image signal processing unit of the X-ray imaging apparatus Timing chart mainly showing the operation timing at the time of imaging of the X-ray imaging apparatus Graph showing the relationship between the wireless communication frequency of the communication means and the sampling frequency of the AD converter

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 X-ray imaging apparatus 5 Subject 20 Solid state detector 28 Communication means 30 Control part 31 Power supply part 32 Image signal processing part 33 Frame buffer 1
34 Frame buffer 2
40 X-ray irradiation apparatus 41 X-ray source 60 Imaging control means 61 Communication means

Claims (5)

A solid-state detector that records the image information upon receiving irradiation of radiation carrying the image information, and outputs an analog signal representing the recorded image information;
Image signal processing means for AD-converting an analog signal output from the solid-state detector to generate a digital image signal;
Communication means for wirelessly transmitting the digital image signal output from the image signal processing means to an external device at a communication frequency higher than the sampling frequency of AD conversion of the image signal processing means;
The solid state detector, the image signal processing means, and the communication means so that a photographing operation including a recording operation of the solid state detector and a processing operation of the image signal processing means is performed in parallel with the communication operation of the communication means. A radiation imaging apparatus comprising: control means for controlling   The control means controls the solid-state detector, the image signal processing means, and the communication means so as to transmit a digital image signal generated during a certain photographing operation during the next photographing operation. The radiation imaging apparatus according to claim 1.   The radiographic apparatus according to claim 1, wherein the image signal processing unit and the communication unit are arranged on the same side with respect to a detection surface of the solid state detector. A first frame buffer and a second frame buffer between the image signal processing means and the communication means;
When all the digital image signals generated during one photographing operation are output from the image signal processing means to the first frame buffer, the first frame buffer transfers to the second frame buffer. On the other hand, the control means includes the solid state detector and the image so that the digital image signal is output and the solid state detector and the image signal processing means are in a standby state in which a next photographing operation can be performed. 4. The radiographic apparatus according to claim 1, wherein the radiographic apparatus controls signal processing means. When the control means has already received a photographing request signal from an external photographing control means at the time of entering the standby state, the solid state detector and the image signal processing means are configured to start a photographing operation. The radiation imaging apparatus according to claim 4, wherein the radiation imaging apparatus controls the radiation.

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