JP4738954B2 - Radiation imaging apparatus, method thereof, and program - Google Patents

Description

  The present invention relates to a radiation imaging apparatus that performs radiation imaging using radiation or the like, a method thereof, and a program. Here, in this specification, in addition to α-rays, β-rays, γ-rays, and the like, which are beams formed by particles (including photons) emitted by radiation decay, beams having the same or higher energy, for example, X-rays , Particle beams, cosmic rays, etc. are also included in the radiation.

  FIG. 4 is a diagram showing a schematic configuration of a radiation imaging system including a conventional radiation imaging apparatus. FIG. 5 is a schematic circuit diagram of an imaging means used in a conventional radiation imaging apparatus. FIG. 6 is a diagram showing an example of driving timing of the conventional radiation imaging apparatus.

  As shown in FIG. 4, a conventional radiation imaging system 400 includes a radiation generator 401, an imaging unit 402, a radiation I / F 403, and a control unit 404 (for example, Patent Document 1, Patent Document 2, Patent Document). 3). The imaging unit 402 is connected to the control unit 404 via a cable 405c, and a control signal such as a drive pulse is supplied from the control unit 404 to the imaging unit 402. The radiation generator 401 and the control unit 404 are connected via a radiation I / F 403. At this time, the radiation generator 401 and the radiation I / F 403 are connected by a cable 405b. Further, the radiation I / F 403 and the control means 404 are connected by a cable 405a.

  An imaging unit 402 used in a conventional radiation imaging apparatus disclosed in Patent Document 4 will be described with reference to FIG. The image pickup unit 402 is an area sensor 501 that performs two-dimensional arraying of pixels composed of photoelectric conversion elements such as PIN photodiodes and switching elements such as thin film transistors (TFTs) that are formed using amorphous silicon. have. A bias voltage Vs is applied from the power source to the common electrode side of the PIN photodiode of each pixel. The TFT gate electrode of each pixel is connected to common gate lines Vg1 to Vg1 to 3. The common gate line is connected to a gate driving device 502 including a shift register (not shown). On the other hand, the source electrode of each TFT is connected to the common data lines Sig 1 to 3, and is output as an image signal by a reading device 503 including an input amplifier 504, a sample hold 505, an analog multiplexer 506, an output amplifier 507, an LPF circuit 508, and the like. The

  Next, the operation of the conventional radiation imaging system 400 will be described using the timing chart of FIG. In FIG. 6, RES, Vg1, Vg2, Vg3, and SMPL signals are control signals supplied from the control unit 404 of FIG. 4 to the imaging unit 402, and are also shown in FIG. Here, RES is a reset of the common data line and the input amplifier 504, Vg1 to Vg3 are signals applied to the gates of the TFTs of each common gate line, and SMPL is a signal for transferring charges to the capacitor of the sample hold 505. The analog output is an output signal including subject information output from the reading device 503.

The conventional radiation imaging system 400 gives control signals to the radiation generation apparatus 401 and the imaging means 402 using a common control means 404 in order to operate the radiation generation apparatus 401 and the imaging means 402 in synchronization. . Thus, the radiation control signal A given from the control means 404 to the radiation I / F 403 and the radiation control signal C given from the control means 404 to the imaging means 402 can be synchronized.
Japanese Patent Laid-Open No. 08-130682 Japanese Patent Laid-Open No. 08-257026 JP 2001-296363 A JP 05-503770 gazette

  However, since an element such as a relay is used for the radiation I / F 403, a timing delay may occur. Therefore, the radiation control signal A may be given to the radiation generator 401 as the radiation control signal B delayed for a predetermined period (for example, period D in FIG. 6). In this case, the radiation generator 401 generates pulsed radiation to the imaging unit 402 according to the radiation control signal B delayed for a predetermined period from the radiation control signal A.

  In the case of a radiation imaging system using pulsed radiation irradiation, radiation irradiation may be prohibited during a reading period between A and B and A 'and B' shown in FIG. Therefore, the control unit 404 has to set a timing margin in consideration of the delay of the radiation pulse and supply control signals such as RES, Vg1, Vg2, Vg3, and SMPL to the imaging unit 402.

  In addition, since the relay element used for the radiation I / F has a large delay and is unstable, precise timing control is difficult, and the timing is easily limited. Due to this restriction, high-speed reading is unavoidable, and as a result, there are cases where it is disadvantageous for the noise band.

  In addition, there is a method of shooting by irradiating a subject with continuous radiation without synchronizing the radiation generator and the imaging means, but there is a problem that the motion of the subject is blurred and the image quality is lowered.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a radiation imaging apparatus capable of functioning the synchronization operation of the radiation generation apparatus and the imaging unit more reliably.

The present invention has been made to solve the above-described problems. In the radiographic apparatus according to the first aspect of the present invention, an imaging unit that captures a radiographic image based on a radiation pulse emitted from the radiation generator, a detection unit that detects the radiation pulse, and a in the radiation imaging apparatus and a control means for controlling said image pickup means based on the detection result, the imaging means includes a filter means for limiting a particular frequency band of the output signal of the image pickup means, said control means Has calculation means for calculating the pulse width and period of the radiation pulse based on the detection result of the detection means, and based on the pulse width and period of the radiation pulse calculated by the calculation means, the imaging A control signal for controlling the frame rate of the means and limiting the specific frequency band is output to the filter means .

  Here, the control of the imaging unit by the control unit includes, for example, outputting a control signal for reading out a pixel signal corresponding to the amount of received radiation from each pixel arranged in a grid pattern in the imaging unit. The radiation pulse is emitted from a radiation generator.

  The radiation imaging system according to the second aspect of the present invention includes a radiation generation apparatus and the radiation imaging apparatus described above.

In the radiographic method according to the third aspect of the present invention, an irradiation step of irradiating an imaging means for capturing a radiographic image with a radiation pulse, a detection step of detecting the radiation pulse, and a detection result in the detection step A control step of controlling the imaging means based on, wherein in the control step, a pulse width and a period of the radiation pulse are calculated based on a detection result in the detection step, and the calculated radiation pulse Based on the pulse width and the period, the frame rate of the imaging means and the specific frequency band of the filter means for limiting a specific frequency band of the output signal of the imaging means are controlled.

  The program according to the fourth aspect of the present invention is characterized by causing a computer to execute the radiation imaging method.

  A computer-readable storage medium according to the fifth aspect of the present invention is characterized in that the program is stored.

  According to the present invention, the synchronization operation of the timing of the radiation pulse emitted by the radiation generator and the imaging operation timing in the imaging means can be performed more reliably without providing a complicated connection or interface with the radiation generator that emits the radiation pulse. It is possible to make it.

  The preferred embodiments of the present invention will be described below with reference to the drawings. In the present embodiment, X-rays will be described as an example of radiation. However, the present invention is not limited to this, and may include α rays, β rays, γ rays, and the like.

  FIG. 1 is a diagram showing a schematic configuration of a radiation imaging apparatus according to a preferred embodiment of the present invention.

  In FIG. 1, reference numeral 100 denotes a radiation imaging apparatus, which includes an imaging unit 102, a radiation pulse detection unit 103, and a control unit 104. The radiation generation apparatus 101 irradiates the imaging unit 102 of the radiation imaging apparatus 100 with pulsed radiation (hereinafter referred to as a radiation pulse). Thus, a radiation imaging system including the radiation imaging apparatus 100 and the radiation generation apparatus 101 is configured. The imaging unit 102 senses the intensity of the radiation emitted from the radiation generation apparatus 101 and captures a radiation image at a timing according to a control signal from the control unit 104. The radiation pulse detector 103 detects a change in the radiation pulse emitted from the radiation generator 101 and outputs a detection signal to the controller 104.

  Compared with the conventional radiographic system of FIG. 4, the radiographic system in the present embodiment has the following features different from the conventional radiographic system.

  First, in the radiation imaging system according to the present embodiment, the radiation generation apparatus 101 and the control unit 104 of the radiation imaging apparatus 100 are not connected by a cable, and it is not necessary to perform communication between these apparatuses. In addition, the radiation imaging system in the present embodiment is provided with a radiation pulse detection unit 103. The detection signal of the change of the radiation pulse output from the radiation pulse detection unit 103 is input to the control unit 104. The control unit 104 can control the imaging unit 102 based on the detection result of the radiation pulse detection unit 103. The radiation pulse detecting means 103 can be constituted by a phototimer including a PIN type photodiode formed using crystalline silicon, and can detect the rising and falling of the radiation pulse irradiated by the radiation generating apparatus 101 with high accuracy. Is possible. In the present embodiment, the connection between the radiation pulse detection unit 103 and the control unit 104 and the connection between the control unit 104 and the imaging unit 102 are performed using the cable 105. However, in a preferred embodiment of the present invention, these connections are not limited to cables, and wireless communication such as wireless LAN or infrared communication may be used.

  Next, a detailed configuration example of the imaging unit 102 illustrated in FIG. 1 will be described and described.

  FIG. 3 is a diagram illustrating a detailed configuration example of the imaging unit 102 illustrated in FIG. 1. In FIG. 3, the area sensor 201 is a matrix drive in which pixels composed of a conversion element such as a PIN photodiode PD formed using amorphous silicon and a switching element such as a thin film transistor (TFT) T1 are two-dimensionally arranged. I do. A bias voltage Vs is applied from the power source to the common electrode side of the PIN photodiode PD of each pixel included in the area sensor 201. The gate electrodes of the TFTs T <b> 1 of the respective pixels are connected to the common gate lines Vg <b> 1 to 3, and the common gate lines Vg <b> 1 to 3 are connected to the gate driving device 202. The gate driving device 202 is composed of a shift register, for example.

  On the other hand, the source electrode of each TFT · T 1 is connected to the common data lines Sig 1 to 3, and a pixel signal is output to the readout device 203. The readout device 203 includes an input amplifier 204, a sample hold 205, an analog multiplexer 206, an output amplifier 207, an LPF circuit 208, and a resistance value control unit 209. Based on the pixel signals input from the common data lines Sig1 to Sig3, An image signal is generated and output in analog form.

  The features of the imaging unit 102 shown in FIG. 3 that are different from the conventional imaging unit shown in FIG. 5 will be described. First, it has a low-pass filter (hereinafter abbreviated as LPF) circuit 208 connected to the output amplifier 207 of the reading device 203, and the resistance value of the variable resistance circuit of the LPF circuit 208 is that the LPF circuit 208 has a variable resistance. The point which can be changed by control by the resistance value control part 209 differs. Thereby, the cutoff frequency of the LPF circuit 208 connected to the output amplifier 207 of the reading device 203 can be controlled according to the control of the resistance value control unit 209. Specifically, the resistance value control unit 209 operates in accordance with a control signal from the control unit 104 in FIG. In other words, the control unit 104 can control frequency band restriction processing for the output signal of the imaging unit 102. For example, the control unit 104 can change the frequency band of the LPF circuit 208 according to the driving speed of the area sensor 201. Thereby, the noise reduction of the output signal of the imaging means 102 is realizable. In the present embodiment, the area sensor is described as being configured with a PIN photodiode formed using amorphous silicon as a conversion element and a TFT as a switching element. However, the preferred embodiment of the present invention is not limited to this, and a MIS type sensor formed using amorphous silicon instead of the PIN type photodiode may be used as the photoelectric conversion element. When forming a radiation imaging apparatus, it is desirable to arrange a scintillator that is a wavelength converter that converts radiation such as cesium iodide into light in a wavelength band that can be detected by the photoelectric conversion element on the area sensor. In this case, the conversion element includes a photoelectric conversion element and a scintillator. Further, the conversion element may be formed using a material that directly converts radiation into electric charge, such as lead iodide, mercury iodide, amorphous selenium, or gallium arsenide. Furthermore, the material of the area sensor using the photoelectric conversion element is not limited to amorphous silicon, and polycrystalline silicon or single crystal silicon may be used. When an area sensor is configured using single crystal silicon, a conversion element such as a CCD or a CMOS sensor can be used.

  Next, the operation of the imaging unit 102 described with reference to FIG. 3 will be described.

  FIG. 2 is a diagram illustrating an example of driving timing of the imaging unit 102 described in FIG. As shown in FIG. 2, the radiation generating apparatus 101 of this embodiment periodically generates radiation pulses. The radiation imaging apparatus 100 in the present embodiment can continuously read out the radiation pulses. The radiation pulse detecting means 103 detects the rising edge T1 of the first radiation pulse (actual radiation irradiation), the falling edge T2 of the first radiation pulse, the rising edge T1 'of the next radiation pulse, etc. shown in FIG. The control means 104 that has received this detection signal has a function (calculation means) for calculating the pulse width and pulse period of the radiation pulse from the radiation generating apparatus 101. Next, the control means 104 controls the driving of the imaging means 102 as shown in FIG. 2 based on the calculated pulse width and pulse period of the radiation pulse. Specifically, the control unit 104 drives the imaging unit 102 by supplying control signals such as RES, Vg1, Vg2, Vg3, and SMPL to the imaging unit 102. For example, the control unit 104 controls the frame rate of the imaging unit 102 in accordance with the obtained pulse width and pulse period of the radiation pulse.

  First, the control means 104 puts the imaging means 102 in the accumulation state during the period in which the radiation pulses in the periods T1 'to T2' are rising. Next, the control unit 104 controls the driving speed so that the pixel signal read-out process is completed between the radiation pulse falling timing T2 'and the rising timing T1 "of the next radiation pulse. That is, the reset operation by RES, the charge transfer operation by Vg1 to 3 and the sample hold by SMPL are completed between T2 'and T1 ". In addition, the frequency band of the LPF circuit 208 connected to the output amplifier 207 of the reading device 203 is changed according to the driving speed. Thereby, the frequency band of the output amplifier 207 determined by the LPF circuit 208 can be changed according to the driving speed, and noise reduction of the output signal can be realized.

  Here, FIG. 7 shows a specific configuration example of the control means 104 of the present embodiment. The radiation pulse rise time memory 106 and the radiation pulse fall time memory 107 are time T1, T1 ′, T1 ″, T1 ′ ″... And T2, T2 ′, T2 ″, T2 ′ shown in FIG. ... Are sequentially stored and updated, and input to the calculation means 108. Based on the information from these memories, the calculation means 108 calculates a pulse period and a pulse width, and causes the drive timing generation means 109 to generate a signal for driving the area sensor. Here, in FIG. 7, the drive timing generation unit 109 generates RES, Vg 1 to 3, SMPL, and LPF band control signals, but is not limited to these signals. For example, when the gate driving device 202 is configured by a shift register, a start pulse, a shift clock, an enable signal, and the like may be generated instead of Vg1 to Vg1. Furthermore, in the present embodiment, the control unit 104 and the imaging unit 102 are provided separately, but a part or all of the functions of the control unit may be built in the imaging unit. In recent medical practice, a portable imaging means called a cassette is sometimes used. Therefore, it is more desirable to incorporate a part or all of the functions of the control means 104 of the present invention in the imaging means 104. Here, FIG. 8 is a diagram showing a radiation imaging system using the radiation imaging apparatus according to the preferred embodiment of the present invention. Reference numeral 6040 denotes a portable imaging means. Reference numeral 6050 denotes a movable mobile radiation generator. Reference numeral 6060 denotes radiation generated from the mobile radiation generator 6050, reference numeral 6061 denotes a patient or subject, and reference numeral 6062 denotes a patient or subject's chest. Further, 6070 is an image processor that performs image processing on an electrical signal from the imaging means 6040, 6080 is a display that displays the image information subjected to image processing, and 6090 is a transmission means such as a telephone line for transmitting the image information. Reference numeral 6100 denotes developing means such as a film processor for outputting image information to the film 6110. The radiation pulse detection means is preferably built in 6040 portable imaging means. Some or all of the functions of the control unit 104 may be provided inside the image processor 6070 or may be built in the portable imaging unit 6040. From the viewpoint of portability, it is more desirable that the function of the control unit 104 is built in the portable imaging unit 6040.

  The radiation imaging apparatus 100 performs the above processing on the radiation pulses in the periods T1 "to T2" and the radiation pulses in the periods T1 "" to T2 "" as appropriate. As a result, the radiation imaging apparatus 100 according to the present embodiment causes the imaging unit 102 to synchronize with the radiation pulse emitted by the radiation generation apparatus 101 without connecting the control unit 104 and the radiation generation apparatus 101 with a cable or the like. The radiation image can be read by driving. That is, the cable and the radiation I / F for connecting the radiation generating apparatus 101 and the control unit 104 that are conventionally required are not required, and the radiation imaging system can be configured more simply. Although there are cases where the conventional radiation I / F cannot cope, the radiation imaging apparatus 100 of the present embodiment can also cope with radiation generation apparatuses having different specifications due to differences in manufacturers.

  Since the configuration of the radiation imaging apparatus 100 in the present embodiment does not require complicated cable connection with the radiation generation apparatus 101, the configuration is suitable for application to a portable radiation imaging apparatus. In this embodiment, the radiation pulse detection unit 103 is provided in the vicinity of the imaging unit 102. However, the radiation pulse detection unit 103 may be provided in the vicinity of the radiation generator 101 or in the vicinity of the subject. The radiation pulse detection means 103 may be provided inside the imaging means 102, or the radiation pulse may be detected using at least a part of the output of the imaging means 102 itself.

  Further, in the radiation imaging apparatus 100 according to the present embodiment, the delay as in the conventional period D shown in FIG. 6 does not occur with respect to the timing of the periodic radiation pulse output from the radiation generation apparatus 101. Is reduced, and the conventional high-speed reading is not required in the imaging unit 102. Accordingly, a sufficient time can be secured for accumulation and readout of pixel signals, so that it is possible to provide a radiation imaging apparatus capable of capturing a radiation image with a better S / N ratio (with reduced noise) than before. . Further, since the radiation imaging system according to the present embodiment does not use the radiation I / F, there is no timing error due to the large delay of the radiation I / F (relay element) as in the prior art. Furthermore, according to the configuration of the control unit 104 of the present embodiment, the driving of the imaging unit can be controlled in real time by calculating the pulse period and the pulse width in real time. The pulse period and pulse width of the radiation generator used for diagnosis may change depending on the characteristics of the generator or assumptions of diagnosis. According to a preferred embodiment of the present invention, since the driving of the imaging means can be changed in real time, it is possible to cope with changes in the pulse period and pulse width of the radiation generating apparatus as described above, which is convenient.

  In the above-described embodiment, the arithmetic function of the control unit 104 is realized by hardware. However, the present invention is not limited to this, and a CPU (Central Processing Unit) is executed by reading a program for realizing each processing function from the memory. The function may be realized by doing so. That is, the hardware configuration of the control unit 104 may include at least a CPU and a memory.

  Further, the preferred embodiment of the present invention is not limited to the above-described configuration, and at least a part of the functions of each process of the control unit 104 may be realized by dedicated hardware. The above-described memory is typically a computer-readable recording medium, and includes, for example, a nonvolatile memory such as a flash memory and a ROM. However, the memory is a recording medium that can only be read, such as a magneto-optical disk device, HDD (hard disk drive), CD-ROM, volatile memory other than RAM, or a computer-readable / writable recording medium using a combination thereof. It may be configured.

  In addition, a program for realizing each function of the control means 104 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system and executed to execute each process. Also good. The computer system may include not only software such as an OS but also hardware such as peripheral devices. Specifically, the program read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. Thereafter, based on the instructions of the program, the CPU provided in the function expansion board or function expansion unit performs part or all of the actual processing. The present invention includes the case where the functions of the above-described embodiments are realized by the processing.

  The computer-readable recording medium typically includes a portable medium such as a flexible disk, a magneto-optical disk, a ROM, and a CD-ROM, and a storage device such as a hard disk built in the computer system. However, in a computer-readable recording medium, like a volatile memory (RAM) inside a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line, Those holding the program for a certain period of time may be included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the transmission medium for transmitting the program includes a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.

  The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

  A program product such as a computer-readable recording medium in which the above program is recorded can also be applied as an embodiment of the present invention. The above program, recording medium, transmission medium, and program product are included in the scope of the present invention.

  As mentioned above, although embodiment of this invention has been explained in full detail with reference to drawings, a concrete structure is not restricted to this embodiment, The deformation | transformation of the range which does not deviate from the summary of this invention is also included.

  The present invention is suitably used for a radiation detection apparatus that detects radiation such as X-rays and γ-rays, and is applied to a medical image diagnostic apparatus, a nondestructive inspection apparatus, an analysis apparatus using radiation, and the like.

It is a figure which shows schematic structure of the radiography apparatus which concerns on suitable one Embodiment of this invention. 6 is a diagram illustrating an example of driving timing of the imaging unit 102. FIG. It is a figure which shows the detailed structural example of the imaging means 102 shown in FIG. It is a figure which shows schematic structure of the radiography system containing the conventional radiography apparatus. It is a typical circuit diagram of the imaging means used for the conventional radiography apparatus. It is a figure which shows the example of a drive timing of the conventional radiography apparatus. It is a figure which shows the specific structural example of the control means 104 which concerns on suitable embodiment of this invention. It is a figure which shows the radiography system using the radiography apparatus which concerns on suitable embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Radiography apparatus 101 Radiation generation apparatus 102 Imaging means 103 Radiation pulse detection means 104 Control means 105a, 105b Cable 106 Radiation pulse rise time memory 107 Radiation pulse fall time memory 108 Calculation means 109 Drive timing generation means

Claims (9)

An imaging unit that captures a radiographic image based on a radiation pulse emitted from the radiation generating device; a detection unit that detects the radiation pulse; and a control unit that controls the imaging unit based on a detection result of the detection unit; In a radiation imaging apparatus having
The imaging means has filter means for limiting a specific frequency band of an output signal of the imaging means,
The control means has a calculation means for calculating a pulse width and a period of the radiation pulse based on a detection result of the detection means, and based on the pulse width and the period of the radiation pulse calculated by the calculation means. A radiation imaging apparatus that controls a frame rate of the imaging unit and outputs a control signal for limiting the specific frequency band to the filter unit . The radiation imaging apparatus according to claim 1, wherein the detection unit is provided in the vicinity of the imaging unit. The radiation imaging apparatus according to claim 1, wherein the detection unit is provided in the vicinity of the radiation generation apparatus. The radiation imaging apparatus according to claim 1, wherein the detection unit is provided as a part of the imaging unit. Radiation imaging system comprising: the radiation imaging apparatus, comprising: a radiation generator for generating the radiation pulses, to any one of claims 1 4. The radiation imaging system according to claim 5 , wherein the imaging unit is a portable imaging unit, and the radiation generator is a mobile radiation generator. An irradiation step of irradiating a radiation pulse to an imaging means for capturing a radiation image;
A detection step of detecting the radiation pulse;
The detection step in the detection result on the basis calculates the pulse width and period of the radiation pulses, on the basis of the pulse width and the period of the radiation pulses the operation and frame rate of the imaging means, the imaging means A control step for controlling the specific frequency band of the filter means for limiting a specific frequency band of the output signal ;
Radiation imaging method including A process for irradiating a radiation pulse to an imaging means for capturing a radiation image;
A process for detecting the radiation pulse by a detection means;
Wherein the pulse width and period of the radiation pulses is calculated by calculating means, based on the pulse width and the period of the calculated radiation pulses on the basis of the detection result obtained from said detecting means, a frame of said image pickup means A process for causing the control means to control the rate and the specific frequency band of the filter means for limiting a specific frequency band of the output signal of the imaging means ;
A program that causes a computer to execute. A computer-readable storage medium storing the program according to claim 8 .

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