WO2007096937A1 - 放射線撮像装置および放射線検出信号処理方法 - Google Patents
放射線撮像装置および放射線検出信号処理方法 Download PDFInfo
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- 230000005855 radiation Effects 0.000 title claims abstract description 278
- 238000000034 method Methods 0.000 title claims description 89
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
- A61B6/42—Arrangements for detecting radiation specially adapted for radiation diagnosis
- A61B6/4208—Arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector
- A61B6/4233—Arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector using matrix detectors
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
- A61B6/02—Arrangements for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
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- A—HUMAN NECESSITIES
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- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
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- A61B6/50—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment specially adapted for specific body parts; specially adapted for specific clinical applications
- A61B6/504—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment specially adapted for specific body parts; specially adapted for specific clinical applications for diagnosis of blood vessels, e.g. by angiography
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- A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
- A61B6/58—Testing, adjusting or calibrating thereof
- A61B6/582—Calibration
- A61B6/585—Calibration of detector units
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- G—PHYSICS
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- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/16—Measuring radiation intensity
- G01T1/24—Measuring radiation intensity with semiconductor detectors
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
- G03B42/00—Obtaining records using waves other than optical waves; Visualisation of such records by using optical means
- G03B42/02—Obtaining records using waves other than optical waves; Visualisation of such records by using optical means using X-rays
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- H04N5/30—Transforming light or analogous information into electric information
- H04N5/32—Transforming X-rays
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y10S378/00—X-ray or gamma ray systems or devices
- Y10S378/901—Computer tomography program or processor
Definitions
- the present invention relates to a medical or industrial device configured to obtain a radiation image based on a radiation detection signal output at a predetermined sampling time interval from a radiation detection means in accordance with radiation irradiation to a subject.
- the present invention relates to a technique for removing a time delay caused by a radiation detection means from a radiation detection signal taken out from the radiation detection means.
- An X-ray detector for detecting an X-ray transmission image of a subject that has recently been generated by X-ray irradiation by an X-ray tube in a medical X-ray diagnostic apparatus which is one of the representative devices of a radiation imaging apparatus
- a flat panel X-ray detector (hereinafter referred to as “FPD” t, as appropriate) in which an extremely large number of X-ray detection elements using a semiconductor or the like are arranged vertically and horizontally on an X-ray detection surface is used.
- sampling is performed based on an X-ray detection signal for one X-ray image taken out from the FPD at a sampling time interval when the subject is irradiated with radiation by the X-ray tube.
- a configuration is adopted in which an X-ray image corresponding to an X-ray transmission image of the subject at each time interval is obtained.
- the use of FPD is advantageous in terms of device structure and image processing because it is lighter and does not cause complex detection distortion, compared to image intensifiers that use conventional power.
- the time delay included in each radiation detection signal extracted at the sampling time interval is assumed to be an impulse response composed of an exponential function with several time delays. Delay after removing time delay from radiation detection signal y
- the calculation process for the removal radiation detection signal X is performed according to the following equation.
- N Number of exponential functions with different time constants constituting impulse response n: Subscript indicating one of exponential functions constituting impulse response a: Strength of exponential function n
- N Number of exponential functions with different time constants constituting impulse response n: Subscript indicating one of exponential functions constituting impulse response a: Strength of exponential function n
- F, ⁇ , ⁇ which are impulse response coefficients of FPD, are obtained in advance, and fixed to the radiation detection signal ⁇
- Patent Document 2 X with the time delay removed is calculated.
- Patent Document 3 In addition to the method of Patent Document 2 described above, there is a technique for reducing a long time constant component for a time delay using a backlight (see, for example, Patent Document 3).
- a 17-inch FPD has 3072 ⁇ 3072 pixels in length and breadth
- the above-described method of Patent Document 2 requires a large amount of calculation for recursive calculation processing. Therefore, in the case of fluoroscopic shooting of moving images, measures are taken to reduce the amount of calculation by performing a viewing operation that adds pixels. For example, in a viewing operation that combines 2 X 2 pixels both vertically and horizontally, the number of pixels can be reduced to 1Z4 and the amount of calculation can be reduced to 1Z4. In addition, in the viewing operation that combines the vertical force pixels and the horizontal 2 ⁇ 4 pixels into one pixel, the number of pixels can be reduced to 1Z8 and the amount of calculation can be reduced to 1Z8.
- a high resolution image is acquired when the number of pixels to be viewed is small, and a low resolution image is acquired when the number of pixels to be viewed is large. . Therefore, when focusing on reducing the amount of calculation rather than obtaining a high-resolution image, a low-resolution image is obtained by increasing the number of pixels to be viewed. To reduce the amount of calculation. Conversely, if it is more important to obtain a high-resolution image than to reduce the amount of calculation, increasing the amount of calculation reduces the number of pixels subject to viewing and acquires a high-resolution image. .
- the image range to be subjected to recursive calculation processing is changed to increase or decrease the amount of calculation.
- the amount of calculation is larger than when the 12-inch square is increased by the amount of image area subject to recursive computation. Become more.
- the amount of calculation is less than with a 12-inch square, as the image range subject to recursive computation is narrowed. .
- a plurality of modes that also have the combined power of the illumination field and the viewing are prepared in advance, and the frame rate of the moving image is maintained by switching the modes as required by the operator. Therefore, when observing a high-resolution image, the illumination field is narrowed in order to suppress an increase in the amount of calculation due to the small number of pixels to be viewed. For example, when observing a high-resolution image, use the 2 X I viewing instead, and use a mode that limits the illumination field to 9 inches square. Conversely, when observing an image with a wide illumination field, the number of pixels that are subject to viewing is reduced in order to suppress an increase in the amount of calculation due to the expansion of the illumination field. For example, when observing an image with a wide illumination field, enlarge to a 17-inch square illumination field, and instead use a mode limited to a low resolution of 4 X 2 views.
- Patent Document 1 US Pat. No. 5,249,123 (Mathematical expressions and drawings in the specification)
- Patent Document 2 Japanese Patent Application Laid-Open No. 2004-242741 (Formulas and Drawings in the Specification)
- Patent Document 3 Japanese Patent Application Laid-Open No. 9-9153 (page 3-8, FIG. 1)
- FIG. 12 is a diagram schematically showing images before and after field expansion
- FIG. 12 is a diagram in which irradiation conditions before and after irradiation field expansion are associated with images in time series.
- the image before the irradiation field expansion is set to P, and the irradiation field expansion is performed.
- the timing of the irradiation field expansion instruction is T, and when ON in Fig. 12,
- the irradiation signal indicates the radiation irradiation status
- the OFF irradiation signal indicates the radiation non-irradiation status.
- an image P before illumination field expansion a 12-inch square illumination field image is taken as an example.
- the lag component is accumulated because it is left unirradiated without being subjected to recursive computation.
- the outer frame part P is not a problem.
- the outer frame is expanded to a 15-inch square illumination field.
- the lag component superimposed on the minute p appears as high brightness.
- the radiation detection signal is high due to the lag component and has a signal value (high pixel value) due to the overlapped state, high luminance remains in the outer frame portion P, causing a problem in the radiation image. Arise. As described above, if a predetermined operation related to radiation imaging represented by expansion of the irradiation field is interrupted at the time of radiation irradiation, the radiation image is hindered.
- the size of the long time constant component (also called “long-term lag”) for the time delay becomes more pronounced as FPD, so the acceptance criteria for lag characteristics at the time of shipping inspection Measures are taken to ensure that FPDs with high brightness are not shipped.
- stricter acceptance criteria can hinder FPD yield improvement.
- the present invention has been made in view of the above circumstances, and reduces the problem of radiation images caused by interruption of a predetermined operation related to radiation imaging at the time of irradiation of radiation, while reducing radiation detection means caps.
- Another object of the present invention is to provide a radiation imaging apparatus and a radiation detection signal processing method capable of removing the time delay of the radiation detection signal caused by the radiation detection means extracted from the radiation detection signal.
- the present invention has the following configuration.
- the radiation imaging apparatus of the present invention is a radiation imaging apparatus that obtains a radiation image based on a radiation detection signal, and detects radiation that has passed through the subject and radiation irradiating means that irradiates the subject with radiation. And a signal sampling means for extracting a radiation detection signal from the radiation detection means at a predetermined sampling time interval, and the radiation detection means force is also output at the sampling time interval as the subject is irradiated with radiation.
- the apparatus is configured to obtain a radiographic image based on a radiation detection signal, and the apparatus further includes a single or decay time constant for a time delay included in each radiation detection signal extracted at a sampling time interval.
- a time delay removing means for removing from the line detection signal and an irradiation control means for controlling the timing of starting and stopping the irradiation of the radiation irradiating means.
- the irradiation controlling means starts the irradiation of the radiation irradiating means.
- the time delay removing means removes the time delay by recursive calculation processing to obtain a corrected radiation detection signal, and
- an irradiation control means in accordance with an instruction of a predetermined operation relating to radiation imaging.
- the time delay removing means temporarily stops the recursive arithmetic processing, and the signal sampling means is caused by a temporary stop of the radiation irradiating means.
- a radiation detection signal at the time of irradiation is acquired, and (C) with the start of the predetermined operation, the irradiation control means restarts the irradiation of the radiation irradiation means, and the time delay removal means is the non-irradiation It is characterized in that the initiating of the radiation detection signal power based on an initial value obtained by recursive computation again.
- a single time delay included in the radiation detection signal output at a predetermined sampling time interval in accordance with the radiation applied to the subject by the radiation irradiating means is detected.
- the time delay removing means removes the impulse response that is constituted by a plurality of exponential functions having different decay time constants.
- Each radiation detection signal force When removing the time delay, recursive calculation is performed. The process of removing each radiation detection signal by this recursive calculation process is executed according to the following process.
- the signal sampling means acquires a radiation detection signal at the time of non-irradiation due to a temporary stop of the radiation irradiation means.
- the irradiation control means restarts the irradiation of the radiation irradiation means, and the time delay removal means is the initial detection obtained from the radiation detection signal at the time of non-irradiation. Start recursive operation again based on the value. Before the prescribed operation, recursive arithmetic processing is used.
- the time delay removal means removes the time delay, acquires a radiographic image from the obtained corrected radiation detection signal, and performs a recursive calculation process based on the initial value described above after a predetermined operation.
- the time delay removing means removes the time delay and obtains a radiation image from the obtained post-correction radiation detection signal.
- the irradiation is temporarily stopped as described above (B), and recursion is performed.
- the specified operation starts, the irradiation is restarted as shown in (C) above, and the recursive calculation is performed based on the initial value obtained for the radiation detection signal power when no irradiation is performed. Start the process again. Therefore, irradiation and recursive calculation processing can be performed after a predetermined operation by (C) as before the predetermined operation, and irradiation and recursive calculation processing before the predetermined operation can be performed by temporarily stopping in (B). Does not affect the data after the specified operation.
- the signal sampling means acquires the radiation detection signal at the time of non-irradiation due to a temporary stop, and performs recursive calculation processing based on the initial value obtained for the radiation detection signal power at the time of non-irradiation. Therefore, even if the above-mentioned predetermined operation is interrupted at the time of radiation irradiation, the radiation image is prevented from being disturbed by the predetermined operation regarding radiation imaging being interrupted at the time of radiation irradiation. In addition, the time delay of the radiation detection signal power can be more accurately removed.
- the radiation detection signal processing method of the present invention extracts radiation detection signals detected by irradiating a subject at predetermined sampling time intervals, and is based on the radiation detection signals output at the sampling time intervals.
- This is a radiation detection signal processing method that performs signal processing to obtain radiation images, and consists of a single or a plurality of exponential functions with different decay time constants for the time delay included in each radiation detection signal extracted at sampling time intervals.
- the process of removing from each radiation detection signal by the recursive calculation process is performed according to the following process as a result of the impulse response to be generated. (A) With the radiation process started, the recursive calculation process takes time.
- the corrected radiation detection signal is obtained by removing the delay, and (B) Irradiation is temporarily stopped according to the instruction for the predetermined operation related to radiation imaging. At the same time, the recursive calculation process is temporarily stopped, and a radiation detection signal at the time of non-irradiation is acquired by the temporary stop, and (C) the irradiation is started again at the start of the predetermined operation. The recursive calculation process is restarted based on the initial value obtained for the radiation detection signal power at the time of non-irradiation.
- the radiation detection signal processing method of the present invention when a predetermined operation related to radiation imaging is interrupted at the time of radiation irradiation, irradiation is temporarily stopped as described above (B), and recursion is performed.
- the specified operation starts, the irradiation is restarted as shown in (C) above, and recursively based on the initial value from which the radiation detection signal power at the time of non-irradiation can also be obtained.
- the computation process is started again. Therefore, irradiation and recursive calculation processing can be performed after a predetermined operation by (C) as before the predetermined operation, and irradiation and recursive calculation processing before the predetermined operation can be performed by temporarily stopping in (B).
- Examples of the radiation imaging apparatus and the radiation detection signal processing method described above include the following.
- N Number of exponential functions with different time constants constituting impulse response n: Subscript indicating one of exponential functions constituting impulse response a: Strength of exponential function n
- the corrected radiation detection signal X after removing the time delay by the simple gradual equation of equations A to C before the predetermined operation described above.
- the initial value of k nk is determined as shown in Equation D above.
- there is a residual lag (lag signal value) due to the time delay that occurred during the time tO to tl.
- the initial value for recursive calculation processing is set according to the lag signal value remaining at the time of non-irradiation), and impulses obtained by equations A to C under the conditions of the initial value determined by equation D Based on the response, the time delay is removed and the corrected radiation detection signal X is obtained.
- an example of the predetermined operation described above is expansion of the irradiation field of radiation.
- a field of illumination the above-mentioned (B) is the radiation detection signal at the time of the above-mentioned stop (irradiation and recursive calculation process) and the above-mentioned (non-irradiation) non-irradiation in accordance with the instruction to enlarge the irradiation field
- the above-mentioned (non-irradiation and recursive calculation processing) is started again with the start of the irradiation field expansion.
- Radiation detection signal power during irradiation The corrected radiation detection signal is obtained by removing the time delay by recursive calculation based on the initial value obtained.
- the radiation detection signal at the time of non-irradiation due to a temporary stop is acquired, and recursive calculation processing is performed based on the initial value that can also obtain the radiation detection signal power at the time of non-irradiation (C) Therefore, even if the above-mentioned irradiation field expansion is interrupted at the time of radiation irradiation, radiation detection is performed while reducing the trouble of the radiation image due to the irradiation field expansion being interrupted at the time of radiation irradiation. The time delay can be more accurately removed from the signal.
- the illumination field is wider so that it is wider than the image subject to the recursive calculation process and narrower than the image subject to the recursive computation process after the illumination field is enlarged.
- the size of the visual field is manipulated, the following effects are produced.
- the image that is wider than the image subject to the recursive calculation process and that becomes narrower than the image subject to the recursive calculation process after the irradiation field expansion is This is an image obtained by removing the image corresponding to the irradiation field operation means from the image after the irradiation field expansion (that is, the image subjected to the recursive calculation process after the irradiation field expansion) and before the irradiation field expansion. (That is, the image subject to recursive computation before the illumination field expansion) and the image before the illumination field expansion (the outer frame part between the images corresponding to the illumination field operation means) It also becomes an image.
- the outer frame portion that is not subject to recursive calculation processing is related to before and after the illumination field expansion.
- the high brightness appeared after being left in the irradiated state because of the temporary stop of (B) described above, the effects of irradiation before the irradiation field expansion and recursive calculation processing were Does not affect the data of the outer frame part.
- the radiation detection signal at the time of non-irradiation due to a temporary stop is acquired, and the recursive calculation processing based on the initial value obtained from the radiation detection signal at the time of non-irradiation has been described above ( Therefore, the time delay due to the recursive calculation process can be more accurately removed by the above-described initial value even in the outer frame portion after the irradiation field expansion. Because of this, even if the illumination field expansion is interrupted at the time of radiation irradiation, it is possible to reduce the trouble of the radiation image due to high brightness.
- the high brightness described above does not appear, so a certain amount of waiting time may be required before the high brightness attenuates. This also reduces the burden on the subject and helps prevent the doctor's diagnosis.
- the ratio can be considered constant before and after the irradiation field expansion. Therefore, for the pixels that are common before and after the irradiation field expansion, the ratio of the time constant component amount at the time of irradiation before the irradiation field expansion and immediately before the non-irradiation is used as the radiation detection signal at the time of non-irradiation.
- the pixel value based on this is divided for each attenuation time constant, and each divided value is set as the initial value (obtained from the radiation detection signal power when non-irradiation due to temporary stop), and newly expanded by expanding the irradiation field.
- the pixel value based on the radiation detection signal when not irradiated is divided for each attenuation time constant using the same time constant component ratio as that for the common pixel described above.
- the corrected radiation detection signal is obtained by removing the time delay by recursive calculation processing based on each initial value. More specifically, it is performed as follows.
- N Number of exponential functions with different time constants constituting impulse response n: Subscript indicating one of exponential functions constituting impulse response a: Strength of exponential function n
- the time delay is removed based on the impulse responses obtained by the equations A to C under the conditions with the initial values determined by the equations D and H, and the corrected radiation detection signal is obtained. Ask.
- the corrected radiation detection signal X after the time delay is removed by the formulas A to C and the simple recurrence formula.
- FIG. 1 is a block diagram showing an overall configuration of an X-ray fluoroscopic apparatus according to an embodiment.
- FIG. 2 is a plan view showing a configuration of an FPD used in the example device.
- FIG. 3 is a schematic diagram showing a sampling state of an X-ray detection signal at the time of execution of X-ray imaging by the embodiment apparatus.
- FIG. 4 is a flowchart showing a procedure of an X-ray detection signal processing method in the embodiment.
- FIG. 5 is a flowchart showing a recursive arithmetic processing process for removing a time delay before irradiation field expansion in the X-ray detection signal processing method in the embodiment.
- FIG. 6 is a flowchart showing a recursive arithmetic processing process for time delay removal after irradiation field expansion in the X-ray detection signal processing method in the embodiment.
- FIG. 7 is a flow chart showing the procedure of irradiation and recursive calculation processing before and after illumination field expansion in an example.
- FIG. 8 is a diagram in which the irradiation state before and after the irradiation field expansion in the example is associated with the image in time series.
- FIG. 9 is a diagram showing a time delay situation corresponding to the radiation incident situation.
- FIG. 10 is a diagram showing a time delay situation in which a shooting lag (time delay) overlaps fluoroscopy.
- FIG. 11 is a diagram schematically showing images before and after an illumination field expansion.
- FIG.12 A diagram showing the time-series correspondence between irradiation conditions and images before and after conventional irradiation field expansion. is there.
- FIG. 1 is a block diagram illustrating the overall configuration of the X-ray fluoroscopic apparatus according to the embodiment.
- the X-ray fluoroscopic apparatus includes an X-ray tube 1 that irradiates X-rays toward the subject M, and an FPD (flat panel type) that detects X-rays transmitted through the subject M.
- a detection signal processing unit 4 that creates an X-ray image based on the image signal
- an image monitor 5 that displays the X-ray image acquired by the detection signal processing unit 4.
- the embodiment apparatus is configured, and the acquired X-ray image is displayed on the screen of the image monitor 5.
- the X-ray tube 1 corresponds to the radiation irradiating means in the present invention
- the FPD 2 corresponds to the radiation detecting means in the present invention
- the AZD transformation 3 corresponds to the signal sampling means in the present invention.
- the X-ray detection signal corresponds to the radiation detection signal in the present invention
- the X-ray image corresponds to the radiation image in the present invention.
- the X-ray tube 1 and the FPD 2 are arranged to face each other with the subject M interposed therebetween. Specifically, the X-ray tube 1 irradiates the subject M with cone-beam-shaped X-rays while being controlled by the X-ray irradiation control unit 6 at the time of X-ray imaging, and at the same time, occurs along with X-ray irradiation.
- the X-ray tube 1 and the FPD2 are arranged to face each other so that the transmitted X-ray image force FPD2 of the subject M is projected onto the X-ray detection surface.
- the X-ray tube moving mechanism 7 and the X-ray detector moving mechanism 8 are configured so that the X-ray tube 1 and the FPD 2 can reciprocate along the subject M, respectively.
- the X-ray tube moving mechanism 7 and the X-ray detector moving mechanism 8 are controlled by the irradiation detection system movement control unit 9 to control the X-ray irradiation central force FPD2.
- the irradiation detection system movement control unit 9 to control the X-ray irradiation central force FPD2.
- the FPD 2 has a large number of X-ray detection elements 2a on the X-ray detection surface on which a transmission X-ray image of the subject M force is projected. They are arranged vertically and horizontally along Y. For example, X-ray detection elements 2a are arranged vertically and horizontally in a matrix of 1536 x 1536 on an X-ray detection surface having a width of about 30 cm x 30 cm.
- Each X-ray detection element 2a of the FPD2 has a corresponding relationship with each pixel of the X-ray image created by the detection signal processing unit 4, and is projected on the X-ray detection surface based on the X-ray detection signal extracted from the FPD2 An X-ray image corresponding to the transmitted X-ray image is created by the detection signal processing unit 4.
- the AZD converter 3 continuously extracts X-ray detection signals for each X-ray image at a sampling time interval ⁇ t, and the subsequent memory unit 10 generates an X-ray detection signal for X-ray image creation. And X-ray detection signal sampling operation (extraction) is started before X-ray irradiation. That is, as shown in FIG. 3, at the sampling time interval At, all X-ray detection signals for the transmitted X-ray image at that time are collected and stored in the memory unit 10 one after another. Prior to X-ray irradiation, the start of extraction of X-ray detection signals by the AZD converter 3 may be performed manually by the operator or automatically in conjunction with the X-ray irradiation instruction operation. It may be configured.
- the X-ray fluoroscopic apparatus calculates a corrected X-ray detection signal by removing a time delay from each X-ray detection signal by recursive calculation processing.
- Delay removal unit 11 irradiation control unit 12 that controls the start and stop timing of irradiation of X-ray tube 1
- collimator 13 that controls the size of the irradiation field of X-rays emitted from X-ray tube 1
- an illumination field control unit 14 for controlling the collimator 13.
- the time delay removal unit 11 corresponds to the time delay removal unit in the present invention
- the irradiation control unit 12 corresponds to the irradiation control unit in the present invention
- the collimator 13 corresponds to the irradiation field operation unit in the present invention. To do.
- the time delay is included in each X-ray detection signal extracted from the FPD 2 at sampling time intervals.
- the time delay is removed from each X-ray detection signal by performing the recursive calculation process described above by considering the time delay as an impulse response composed of one or more exponential functions having different decay time constants. As shown in Fig. 8, the process of removing each X-ray detection signal by this recursive calculation process is performed according to the following process.
- the time delay removal unit 11 removes the time delay by recursive calculation processing and obtains a corrected X-ray detection signal. Then, in accordance with an instruction of (B) predetermined operation related to radiation imaging (in this embodiment, irradiation field expansion), the irradiation control unit 12 temporarily stops the irradiation and the time delay removal unit 11 recursively. Computation is temporarily stopped (T and Sample in Figure 8)
- the AZD converter 3 acquires an X-ray detection signal at the time of non-irradiation due to a temporary stop of the X-ray tube 1. Further, (C) with the start of the above-described predetermined operation (here, irradiation field expansion), the irradiation control unit 12 restarts irradiation, and the time delay removal unit 11 performs the above-described non-irradiation (FIG. 8). (See T to T in the figure) Start recursive calculation processing again based on the above (see T, transition to OFF force ON in Fig. 8).
- the X-ray detection signal at each time includes a signal corresponding to the past X-ray irradiation as a time delay (see the hatched portion in Fig. 9). It is. This time delay is removed by the time delay removal unit 11 to obtain a corrected X-ray detection signal without time delay. Based on the corrected X-ray detection signal, the detection signal processing unit 4 creates an X-ray image corresponding to the transmitted X-ray image projected on the X-ray detection surface.
- the time delay removal unit 11 before a predetermined operation (in this case, the illumination field expansion), the time delay removal unit 11 removes the time delay by recursive calculation processing, and an X-ray image is obtained from the obtained corrected X-ray detection signal. After a predetermined operation (in this case, the illumination field is expanded), the time delay removal unit 11 removes the time delay by the recursive calculation process based on the initial value described above. An X-ray image is acquired from the corrected X-ray detection signal.
- a predetermined operation in this case, the illumination field expansion
- the time delay removal unit 11 performs a recursive calculation process for removing a time delay from each X-ray detection signal before the predetermined operation described above (here, irradiation field expansion). Use A to C.
- N Number of exponential functions with different time constants constituting impulse response n: Subscript indicating one of exponential functions constituting impulse response a: Strength of exponential function n : Exponential function n decay time constant
- the corrected X-ray detection signal X from which the time delay has been removed is quickly obtained by a simple gradual equation of equations A to C.
- the initial value is determined as in the following formula D.
- the initial value for the recursive operation processing is set by the residual lag signal value when the beam is not irradiated), and the impedance obtained by the equations A to C under the condition of the initial value determined by the equation D is set.
- the corrected X-ray detection signal X is obtained by removing the time delay based on the Lus response.
- the time delay removal unit 11 performs a recursive calculation process for removing the time delay from each X-ray detection signal V after the predetermined operation described above (in this case, the irradiation field expansion).
- Formulas A to C use the same formula as the recursive calculation process before the illumination field expansion described above.
- the sampling time point k here is set as follows without using the sampling time point before the irradiation field expansion. In other words, the irradiation and recursive calculation processing associated with the start of the irradiation field expansion from the time of non-irradiation due to a temporary stop (see T to T in Figure 8)
- the visual field control unit 14 executes the control process according to instructions input from the operation unit 15 (e.g., instructions for expanding the irradiation visual field), data, or various commands sent from the main control unit 16 according to the progress of X-ray imaging. .
- FIG. 4 is a flowchart showing the procedure of the X-ray detection signal processing method in the embodiment. Note that this shooting includes past shooting as shown in Fig. 10 and the current fluoroscopy! /.
- the extracted X-ray detection signal is stored in the memory unit 10.
- Step S2 Subject M is irradiated with X-rays continuously or intermittently according to operator settings. In parallel with this, extraction of the X-ray detection signal ⁇ for one X-ray image by AZD modification 3 and storage in the memory unit 10 are continued at the sampling time interval At.
- Step S3 When the X-ray irradiation is completed, the process proceeds to the next step S4.
- Step S4 X-ray detection signal Y for one X-ray image collected from memory unit 10 by one sampling
- Step S5 The corrected X-ray detection signal X, that is, the pixel value, in which the time-delay removal unit 11 performs recursive calculation processing according to equations A to C to remove the time-delay from each X-ray detection signal Y Ask for kk.
- the detection signal processing unit 4 creates an X-ray image based on the corrected X-ray detection signal X for one sampling (one X-ray image).
- Step S7 The created X-ray image is displayed on the image monitor 5.
- Step S8 If an unprocessed X-ray detection signal Y remains in the memory unit 10, step S4 k
- X-ray images are created one after another at a speed of about 30 sheets per second, and the created X-ray images can be displayed continuously. Therefore, moving image display of X-ray images becomes possible.
- FIG. 7 is a flowchart showing a recursive calculation process for removing a time delay after the irradiation field expansion in the method
- FIG. 7 is a flowchart showing a procedure of irradiation and recursive calculation processing before and after the irradiation field expansion in the embodiment. Is real It is the figure which matched the irradiation condition before and behind the illumination visual field expansion in an example, and an image in time series.
- step T1 This will be described later in step T1.
- Step U2 State where irradiation is started (see T and OFF force in Fig. 8 as well as transition to ON)
- the corrected X-ray detection signal is obtained by removing the time delay by recursive calculation processing. More specific processing will be described later in steps T1 to T6 in FIG.
- Step U3 If there is an instruction to enlarge the irradiation field from the operation unit 15 (see FIG. 1), Step U3
- Step U4 In response to an instruction to expand the irradiation field, irradiation is temporarily stopped and recursive computation processing is temporarily stopped (see T, sampling point in FIG. 8).
- step ⁇ will be described later.
- the X-ray detection signal after correction is obtained by removing the time delay by recursive calculation processing based on the initial value obtained from (1). More specific processing will be described later in steps ⁇ and ⁇ 2 to ⁇ 6 in Fig. 5.
- Step Tl Collect the residual lag (lag signal value) due to the time delay generated in the past shooting. Specifically, in the first frame, AZD Transform 3 extracts the X-ray detection signal ⁇ ⁇ for one X-ray image due to residual lag from FPD2. This X-ray detection signal ⁇ is recursive
- equation D is expressed by the following equation ⁇ .
- N is the formula G
- Step T4 After increasing k by 1 (k2 k + 1) in equations A and C, then substituting X for the previous time into equation C to obtain S, S, and S The corrected X-ray detection signal X is calculated by substituting the obtained S, S, S and X-ray detection signal Y k-1 lk 2k 3k lk 2k 3k k into equation A.
- Step T5 If there is an unprocessed X-ray detection signal Y, the process returns to Step ⁇ 4, and an unprocessed X k
- Step T6 The post-correction removal X-ray detection signal X of one sampling (one X-ray image) is calculated, and recursive calculation processing for one shot is performed before the irradiation field is expanded.
- Last k The post-correction removal X-ray detection signal X of one sampling (one X-ray image) is calculated, and recursive calculation processing for one shot is performed before the irradiation field is expanded.
- Step ⁇ Collects residual lag (lag signal value) in the same manner as in Step T1 before irradiating field expansion at the time of non-irradiation due to a temporary stop accompanied by an instruction to expand the irradiating field.
- Step T2 Step 2-2 before irradiation expansion is the same as step ⁇ 2, and a description thereof will be omitted.
- the residual ratio ⁇ ⁇ is calculated using the above formula ⁇ instead of using the formula ⁇ ⁇ ⁇ as before the illumination field expansion.
- the prime value is divided for each decay time constant. Then, the divided values are used as the initial values (obtained from the X-ray detection signal force at the time of non-irradiation due to temporary stop) described above using Equation D.
- the pixel value based on 0 is divided for each decay time constant.
- the divided values are used as the initial values described above (obtained as the X-ray detection signal power during non-irradiation due to temporary stop).
- Pixel values based on 0 can be divided for each decay time constant.
- each of the X-ray detection signals ⁇ in non-irradiation is expressed as shown in Expression D above, regardless of the common pixels and the pixels newly added in the irradiation field expansion. The rest of
- the X-ray detection signal Y is added with the pixels to be added being added.
- the average value of all the pixels in the image P before the illumination field expansion is used to improve accuracy.
- Step T3 Since this is the same as Step T3 before the irradiation expansion, its description is omitted.
- Step ⁇ 4 Since step ⁇ 4 before irradiation expansion is the same as step ⁇ 4, description thereof is omitted.
- Step ⁇ 5 Since step ⁇ 5 before irradiation expansion is the same as step ⁇ 5, description thereof is omitted.
- Step ⁇ 6 Since step ⁇ 6 before irradiation expansion is the same as step ⁇ 6, description thereof is omitted. After steps ⁇ and ⁇ 2 to ⁇ 6, the recursive calculation process for one shot is completed after the illumination field is enlarged.
- the AZD converter 3 obtains the X-ray detection signal at the time of non-irradiation due to a temporary stop and recursively based on the initial value from which the X-ray detection signal power at the time of non-irradiation can also be obtained. Since the calculation process is performed as shown in (C), even if the above-mentioned predetermined operation (irradiation field expansion) is interrupted during X-ray irradiation, the predetermined operation related to X-ray imaging (irradiation field expansion) is not performed. It is possible to more accurately remove the time delay from the X-ray detection signal while reducing the trouble of the X-ray image caused by interruption during X-ray irradiation.
- an image that is wider than an image subject to recursive calculation processing (for example, 12 inches) before the irradiation field expansion (for example, 12 inches) and that is subject to recursive calculation processing after the irradiation field expansion (example) For example, when operating the size of the illumination field (for example, 13 inches) to be narrower than 15 inches, the following effects can be obtained.
- the recursive calculation process before the irradiation field expansion, the recursive calculation process is wider than the image subject to the recursive calculation process and after the irradiation field expansion.
- the image that is narrower than the target image is the image P after the irradiation field is expanded.
- the image corresponding to the collimator 13 is removed from the image P, and before the irradiation field expansion.
- Image P (ie, the image subject to recursive computation before the illumination field is expanded)
- the outer frame portion P which is not subject to recursive calculation processing, is related to before and after illumination field expansion.
- the force that was the radiation detection means force SFPD
- This invention uses a radiation detection means that causes a time delay of X-ray detection signals other than FPD! It can also be used for devices with special configurations!
- the present invention can be applied to devices other than the X-ray fluoroscopic apparatus such as an X-ray CT apparatus.
- the above-described embodiment apparatus is a medical apparatus
- the present invention is not limited to medical use but can be applied to industrial apparatuses such as non-destructive inspection equipment.
- the above-described embodiment apparatus is an apparatus that uses X-rays as radiation.
- the present invention is not limited to X-rays, and is also applicable to apparatuses that use radiation other than X-rays (for example, ⁇ -rays). Can be applied.
- a corrected X-ray detection signal is obtained by removing the time delay based on the impulse response obtained by the equations A to C.
- the time delay may be removed based on the innulus response obtained by the equations a to c.
- the predetermined operation related to radiation imaging is enlargement of the irradiation field of view.
- the predetermined operation related to radiation imaging is enlargement of the irradiation field of view.
- the present invention is suitable for a radiographic apparatus equipped with a flat panel X-ray detector (FPD).
- FPD flat panel X-ray detector
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Priority Applications (6)
Application Number | Priority Date | Filing Date | Title |
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EP06714098A EP1987771A4 (en) | 2006-02-20 | 2006-02-20 | DEVICE FOR TAKING RADIOLOGICAL IMAGES AND METHOD FOR PROCESSING RADIATION DETECTION SIGNALS |
JP2008501496A JP4893733B2 (ja) | 2006-02-20 | 2006-02-20 | 放射線撮像装置および放射線検出信号処理方法 |
CN2006800390947A CN101291625B (zh) | 2006-02-20 | 2006-02-20 | 放射线摄像装置以及放射线检测信号处理方法 |
PCT/JP2006/302958 WO2007096937A1 (ja) | 2006-02-20 | 2006-02-20 | 放射線撮像装置および放射線検出信号処理方法 |
US12/280,150 US7760856B2 (en) | 2006-02-20 | 2006-02-20 | Radiographic apparatus and radiation detection signal processing method |
KR1020087004742A KR100970540B1 (ko) | 2006-02-20 | 2006-02-20 | 방사선 촬상장치 및 방사선 검출신호처리방법 |
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PCT/JP2006/302958 WO2007096937A1 (ja) | 2006-02-20 | 2006-02-20 | 放射線撮像装置および放射線検出信号処理方法 |
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US (1) | US7760856B2 (ja) |
EP (1) | EP1987771A4 (ja) |
JP (1) | JP4893733B2 (ja) |
KR (1) | KR100970540B1 (ja) |
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Cited By (2)
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JP2011030778A (ja) * | 2009-07-31 | 2011-02-17 | Canon Inc | 医用画像撮影装置およびその撮影方法 |
JP2014083085A (ja) * | 2012-10-19 | 2014-05-12 | Toshiba Corp | 医用診断装置、x線照射装置およびx線照射方法 |
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JP5405093B2 (ja) * | 2008-12-05 | 2014-02-05 | 富士フイルム株式会社 | 画像処理装置及び画像処理方法 |
WO2011148546A1 (ja) * | 2010-05-26 | 2011-12-01 | 株式会社島津製作所 | X線撮影装置 |
JP5597055B2 (ja) | 2010-07-30 | 2014-10-01 | キヤノン株式会社 | 制御装置及び制御方法 |
JP6056380B2 (ja) * | 2012-10-31 | 2017-01-11 | コニカミノルタ株式会社 | 放射線画像撮影システム |
JP5753551B2 (ja) * | 2013-04-25 | 2015-07-22 | 日立アロカメディカル株式会社 | 放射線測定装置 |
JP6815273B2 (ja) * | 2017-05-18 | 2021-01-20 | 富士フイルム株式会社 | 放射線画像撮影装置、画像処理装置、画像処理方法、及び画像処理プログラム |
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JP4893733B2 (ja) | 2012-03-07 |
EP1987771A1 (en) | 2008-11-05 |
KR20080043794A (ko) | 2008-05-19 |
US7760856B2 (en) | 2010-07-20 |
JPWO2007096937A1 (ja) | 2009-07-09 |
CN101291625B (zh) | 2011-05-04 |
EP1987771A4 (en) | 2011-02-16 |
CN101291625A (zh) | 2008-10-22 |
KR100970540B1 (ko) | 2010-07-16 |
US20090034679A1 (en) | 2009-02-05 |
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