WO2008012917A1

WO2008012917A1 - Radiation photographing device and radiation detecting signal processing method

Info

Publication number: WO2008012917A1
Application number: PCT/JP2006/315028
Authority: WO
Inventors: Akihiro Nishimura; Shoichi Okamura
Original assignee: Shimadzu Corporation
Priority date: 2006-07-28
Filing date: 2006-07-28
Publication date: 2008-01-31

Abstract

A radiation photographing device is configured to seek and estimate lag information at the present based on lag information in the past out of lag information in accordance with a plurality of X-ray detecting signals acquired at a non-irradiating time prior to irradiating an X-ray in photographing. Thus, a lag image can be reasoned by analogy in consideration of the past lag information and, by making use of this analogical lag image to merely eliminate a lag while time delay components, i.e., lag data are properly reasoned by analogy, the time delay components contained in the X-ray detecting signal can be easily eliminated from the X-ray detecting signal.

Description

Specification

Radiation imaging apparatus and radiation detection signal processing method

Technical field

TECHNICAL FIELD [0001] The present invention relates to a radiation imaging apparatus and a radiation detection signal processing method for obtaining a radiation image based on a radiation detection signal detected by irradiating a subject, and in particular, a time delay included in a radiation detection signal. The present invention relates to a technique for removing the radiation detection signal force from the minute.

Background art

As an example of a radiation imaging apparatus, an imaging apparatus that detects an X-ray and obtains an X-ray image has conventionally used an image intensifier (I. I) as an X-ray detection means. In Japan, flat panel X-ray detectors (hereinafter abbreviated as “FPD”) are used.

[0003] The FPD is configured by laminating a sensitive film on a substrate, detects the radiation incident on the sensitive film, converts the detected radiation into an electric charge, and arranges it in a two-dimensional array. The charge is stored in the capacitor. The accumulated charge is read by turning on the switching element and sent to the image processing unit as a radiation detection signal. Then, an image having pixels based on the radiation detection signal is obtained in the image processing unit.

[0004] When a powerful FPD is used, the conventional force is also used, which is lighter and does not cause complicated detection distortion compared to an image intensifier or the like. Therefore, FPD is advantageous in terms of device structure and image processing.

[0005] However, when FPD is used, a time delay is included in the X-ray detection signal. Due to the time delay, the afterimage of X-ray irradiation in the previous imaging is reflected in the X-ray image as an artifact. In particular, in fluoroscopy in which X-ray irradiation is continuously performed at a short time interval (for example, 1Z30 seconds), the influence of the time lag corresponding to the time delay is large and hinders diagnosis.

[0006] Therefore, the knock time is used to reduce the long time constant component for the time delay (see, for example, Patent Document 1), or the time delay is the sum of exponential functions having a plurality of time constants. As a result, recursive arithmetic processing is performed using these exponential functions to perform lag correction (for example, For example, refer to Patent Document 2) to reduce artifacts due to time delay.

[0007] When a backlight is used as in Patent Document 1 described above, the structure becomes complicated due to the structure for the backlight. In particular, if a backlight is used in an FPD that has achieved a lightweight structure, the structure will become heavy and complicated again. In the case of Patent Document 2 described above, it is necessary to perform lag correction by performing recursive calculation processing for the number of times of sampling for acquiring the X-ray detection signal, and the lag correction is complicated.

[0008] Therefore, when performing lag correction so that the time delay included in the X-ray detection signal can be easily removed from the X-ray detection signal, the time lag correction is performed at the time of non-irradiation before X-ray irradiation in imaging. It is possible to obtain a number of X-ray detection signals, acquire lag images based on these X-ray detection signals, and use them to remove lag from the X-ray images to be imaged.

Patent Document 1: Japanese Patent Laid-Open No. 9-9153 (Page 3-8, Fig. 1)

Patent Document 2: Japanese Patent Application Laid-Open No. 2004-242741 (Pages 4-11, Fig. 1, 3-6)

Disclosure of the invention

Problems to be solved by the invention

However, the method of removing lag from the X-ray image to be imaged using the acquired lag image has the following problems. In other words, it is assumed that the lag image acquired by non-irradiation until immediately before imaging has the same value as the lag component superimposed on the X-ray image to be imaged. Then, the X-ray image power is subtracted from the lag image as it is.

[0010] Actually, as shown in Fig. 16 (a), a force time (several minutes or more) has passed since the X-ray irradiation in the previous imaging, which is the source of lag. In this case, the amount of lag (that is, the X-ray detection signal when not irradiated) I

Since N itself is also constant, there is no problem in subtracting the lag image (correction data) obtained by weighted average (weighted average) from the X-ray image. However, as shown in Fig. 16 (b), if so much time (within 1 minute) has not elapsed since the X-ray irradiation in the previous imaging, the lag decays momentarily. It is appropriate to subtract the X-ray image power from the lag image at the time of non-irradiation until just before. In some cases, a component that is not lag is subtracted, resulting in overcorrection. This is a short time constant component of the time delay! /, Na! / This is probably because the medium time constant component is dominant without decaying.

[0011] Therefore, as a measure to solve the troublesome problem, the attenuation state of the lag is acquired in advance and stored in a formula or table, based on the X-ray conditions and elapsed time of the previous imaging! A method of analogizing the lag component superimposed on the X-ray image acquired by this imaging is also conceivable. However, in the case of a powerful method, the attenuation of the lag depends on the X-ray conditions, and a huge amount of attenuation must be maintained in order to cope with many X-ray conditions. Therefore, there is a need for a correction method that can properly analogize the lag even when it is gradually attenuated, and that does not depend on the X-ray conditions.

[0012] The present invention has been made in view of such circumstances, and the time delay included in the radiation detection signal can be easily removed, and the time delay is included. It is an object of the present invention to provide a radiation imaging apparatus and a radiation detection signal processing method capable of appropriately analogizing lag data.

Means for solving the problem

In order to achieve such an object, the present invention has the following configuration.

That is, 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. A radiation detection means for performing acquisition, a plurality of radiation detection signals detected from the radiation detection means at the time of non-irradiation before irradiation of radiation in imaging, and those acquired by the non-irradiation signal acquisition means Among the lag information based on the radiation detection signal, the lag image analogy means for obtaining the current lag information based on the past lag information and analogizing the lag image, and the radiation detection signal detected from the radiation detection means for imaging radiation Based on the irradiation signal acquisition means acquired at the time of irradiation and the radiation detection signal acquired by the irradiation signal acquisition means, the radiation to be imaged Radiation image acquisition means for acquiring an image, and time included in the radiation detection signal by removing lag from the radiation image acquired by the radiation image acquisition means using the lag image estimated by the lag image estimation means It is characterized by comprising lag correction means for performing lag correction related to the time delay by removing the delay from the radiation detection signal. [0014] According to the radiation imaging apparatus of the present invention, the non-irradiation signal acquisition means acquires a plurality of radiation detection signals detected from the radiation detection means at the time of non-irradiation before irradiation of radiation in imaging. Of the lag information based on the radiation detection signals acquired by the non-irradiation signal acquisition means, the lag image analogy means estimates the lag image by obtaining the current lag information based on the past lag information. . On the other hand, the irradiation signal acquisition means acquires the radiation detection signal detected from the radiation detection means at the time of radiation irradiation in imaging. Based on the radiation detection signal acquired by the irradiation signal acquisition means, the radiation image acquisition means acquires a radiation image to be imaged. Then, by removing the lag from the radiographic image acquired by the radiological image acquisition means using the lag image analogized by the lag image analogizing means described above, the time delay included in the radiological detection signal is obtained from the radiation detection signal. The lag correction means performs lag correction related to the time delay due to the removal. In this way, it is not necessary to perform recursive calculation processing and perform lag correction for the number of times of sampling for acquiring a radiation detection signal as in Patent Document 2 described above. Furthermore, because the lag image analogy means obtains the current lag information and analogizes the lag image based on the past lag information, so much time has not passed since the previous radiation exposure. However, it is possible to infer a lag image considering past lag information. As a result, it is possible to properly estimate the lag data that is the time delay. Therefore, by simply removing the lag using the analogized lag image, the time delay included in the radiation detection signal can be easily removed from the radiation detection signal while appropriately estimating the time delay as lag data. be able to. Further, the structure of the apparatus that does not require the use of the backlight as in Patent Document 1 described above does not become complicated.

An example of the radiation imaging apparatus of the present invention includes a lag image acquisition unit that acquires a lag image based on a plurality of radiation detection signals acquired by the non-irradiation signal acquisition unit described above. The image acquisition means and the lag image analogization means described above are used together, and the lag image analogy is performed by the lag image analogization means by acquiring the lag image by the lag image acquisition means. In this example, the acquisition of the lag image by the lag image acquisition unit and the analogy of the lag image by the lag image estimation unit are synonymous.

[0016] Another example of the radiation imaging apparatus of the present invention is the non-irradiation signal acquisition means described above. Based on a plurality of acquired radiation detection signals, a lag image acquisition means for acquiring a lag image is provided, and the lag image acquired by the lag image acquisition means is based on the past lag information. By correcting, the above-described lag image analogizing means estimates the lag image after correction. In another example, after the acquisition of the lag image by the lag image acquisition means, the former lag image is corrected by the lag image estimation means in order to estimate the lag image. Therefore, in the case of this other example, the analogy of the lag image includes the function of correcting the former lag image obtained earlier.

The radiation detection signal processing method according to the present invention is a radiation detection signal processing method for performing signal processing for obtaining a radiation image based on a radiation detection signal detected by irradiating a subject, wherein the signal The processing includes a non-irradiation signal acquisition step of acquiring a plurality of radiation detection signals at the time of non-irradiation before irradiation of radiation in imaging, and lag information based on those radiation detection signals acquired in the non-irradiation signal acquisition step. Based on the lag information of the lag image, the lag image analogy process for estimating the lag image and estimating the lag image, the irradiation signal acquisition process for acquiring the radiation detection signal at the time of radiation irradiation in the imaging, and the irradiation signal acquisition process Based on the detected radiation detection signal, the radiological image acquisition process for acquiring the radiographic image to be imaged and the radiographic image acquired in the radiological image acquisition process Further, by performing lag removal using the lag image estimated in the lag image analogizing step, lag correction for lag correction by removing the time delay included in the radiation detection signal from the radiation detection signal is performed. And a correction process.

According to the radiation detection signal processing method of the present invention, in the non-irradiation signal acquisition step, a plurality of radiation detection signals are acquired at the time of non-irradiation before radiation irradiation in imaging. Of the lag information based on the radiation detection signals acquired in the non-irradiation signal acquisition process, based on the past lag information, in the lag image analogization process, the lag image is estimated by obtaining the current lag information. On the other hand, in irradiation signal acquisition, a radiation detection signal is acquired at the time of radiation irradiation in imaging. Based on the radiation detection signal acquired in the irradiation signal acquisition step, the radiation image acquisition step acquires a radiation image to be imaged. Then, from the radiographic image acquired in the radiographic image acquisition step, the above-described lag image analogization is performed. The lag correction is performed in the lag correction process by removing the lag using the analogized lag image and removing the time lag included in the radiation detection signal by removing the radiation detection signal force. As described above, it is not necessary to perform lag correction by performing recursive arithmetic processing for the number of times of sampling for obtaining the radiation detection signal as in Patent Document 2 described above. Furthermore, since the lag image analogy process obtains the current lag information and analogizes the lag image based on the past lag information, if much time has passed since the radiation exposure in the previous imaging, However, it is possible to infer a lag image considering past lag information. As a result, the lag data that is the time delay can be appropriately estimated. Therefore, simply by removing the lag using the analogized lag image, the time delay included in the radiation detection signal can be estimated from the radiation detection signal while appropriately estimating the time delay as lag data. It can be easily removed.

In an example of the radiation detection signal processing method of the present invention, the above-described past information is a coefficient represented by a signal ratio regarding the radiation detection signal acquired at the past non-irradiation, and the above-described lag image analogy is described. In the process, the current lag information is obtained based on the coefficient, and the lag image is estimated. The past information is not limited to such a signal ratio, and may be a radiation detection signal itself acquired at the past non-irradiation or a signal obtained by multiplying the signal by a constant.

[0020] Another example of the radiation detection signal processing method of the present invention is a lag image for acquiring a lag image based on the radiation detection signals acquired in the non-irradiation signal acquisition step described above! The image acquisition process includes signal processing, and the lag image acquisition process and the lag image estimation process described above are the same process, and the lag image acquisition process is performed by acquiring the lag image in the lag image acquisition process. The analogy of the lag image is performed. In another example, the acquisition of the lag image in the lag image acquisition process and the analogy of the lag image in the lag image analogization process are synonymous.

[0021] Still another example of the radiation detection signal processing method of the present invention is a lag image acquisition that acquires a lag image based on the radiation detection signals acquired in the non-irradiation signal acquisition step described above. The signal processing is provided, and the lag image acquisition described above is performed by correcting the lag image acquired in the lag image acquisition step based on the past lag information described above. It is to analogize the corrected lag image in the process. In this further example, after the lag image is acquired in the lag image acquisition step, the former lag image obtained in advance is corrected in the lag image acquisition step in order to analogize the lag image. Therefore, in this other example, the analogy of the lag image includes a function of correcting the former lag image obtained earlier.

[0022] In a further specific example in the other example described above, the above-described past information is a coefficient represented by a signal ratio regarding the past radiation detection signal acquired in the non-irradiation signal acquisition step described above. Therefore, in the above-described lag image analogizing step, the current lag information is obtained based on the coefficient to estimate the lag image. This specific example is also an example in which the above-described example is combined with another example.

[0023] In this specific example, it is preferable to obtain the coefficient described above for each pixel and obtain the current lag information for each pixel based on each coefficient. Since the attenuation characteristics of lag data are different for each pixel, a high-quality radiographic image without lag can be obtained by this calculation.

[0024] A further specific example in the above-described further example is that the above-described past information is a correction represented by a signal ratio regarding the past radiation detection signal acquired in the above-described non-irradiation signal acquisition step. In the lag image analogy process described above, the correction coefficient is applied to the lag image acquired in the lag image acquisition process to correct the corrected lag image as the current lag information. By analogy. This specific example is also an example in which the above-described example and another example are combined.

In this specific example, it is preferable that the above-described correction coefficient is obtained for each pixel, and correction is performed by applying each correction coefficient to the lag image for each pixel. Since the attenuation characteristics of the lag data are different for each pixel, a high-quality radiographic image without lag can be obtained by obtaining in this way.

The invention's effect

[0026] According to the radiation imaging apparatus and the radiation detection signal processing method according to the present invention, the past lag information among the lag information based on the plurality of radiation detection signals acquired at the time of non-irradiation before radiation irradiation in imaging. Based on the current lag information Therefore, it is possible to infer a lag image that takes into account past lag information.By simply removing the lag using this estimated lag image, the lag data that is the time delay is properly inferred, The time delay included in the radiation detection signal can be easily removed from the radiation detection signal.

Brief Description of Drawings

FIG. 1 is a block diagram of an X-ray fluoroscopic apparatus according to Embodiment 1.

[Fig. 2] This is an equivalent circuit of a flat panel X-ray detector used in an X-ray fluoroscopic apparatus as seen from the side.

[Fig. 3] Equivalent circuit of flat panel X-ray detector in plan view.

FIG. 4 is a schematic diagram showing a flow of data regarding the image processing unit and the memory unit according to the first embodiment.

FIG. 5 is a timing chart regarding irradiation of each X-ray and acquisition of an X-ray detection signal.

FIG. 6 is a flowchart showing a series of signal processing by the non-irradiation signal acquisition unit, lag image acquisition unit, lag image analogy unit, irradiation signal acquisition unit, X-ray image acquisition unit, and lag correction unit according to Example 1. .

FIG. 7 is a flowchart specifically showing the acquisition Z analogy processing of the lag image of FIG.

FIG. 8 is a timing chart regarding the amount of lag (X-ray detection signal at the time of non-irradiation) written together with the irradiation of each X-ray and acquisition of the X-ray detection signal.

FIG. 9 is a block diagram of an X-ray fluoroscopic apparatus according to Embodiments 2 and 3.

FIG. 10 is a schematic diagram illustrating a data flow regarding an image processing unit and a memory unit according to a second embodiment.

FIG. 11 is a flowchart showing a series of signal processing by a non-irradiation signal acquisition unit, a lag image acquisition unit, a lag image analogy unit, an irradiation signal acquisition unit, an X-ray image acquisition unit, and a lag correction unit according to Example 2. is there.

FIG. 12 is a flowchart showing a series of signal processing by a non-irradiation signal acquisition unit, a lag image acquisition unit, a lag image analogy unit, an irradiation signal acquisition unit, an X-ray image acquisition unit, and a lag correction unit according to Example 2. is there.

FIG. 13 is a schematic diagram showing the flow of data related to the image processing unit and the memory unit according to Example 3. It is a schematic diagram.

FIG. 14 is a flow chart showing a series of signal processing by a non-irradiation signal acquisition unit, a lag image acquisition unit, a lag image analogy unit, an irradiation signal acquisition unit, an X-ray image acquisition unit, and a lag correction unit according to Example 3. is there.

FIG. 15 is a graph showing the result of application of Example 3 to actual data measured using a 17-inch direct conversion flat panel X-ray detector.

[FIG. 16] (a) and (b) are timing charts relating to the amount of lag (X-ray detection signal at the time of non-irradiation) written together with conventional X-ray irradiation and X-ray detection signal acquisition.

Explanation of symbols

[0028] 2… X-ray tube

3… Flat panel X-ray detector (FPD)

9a… Non-irradiation signal acquisition unit

9b… Lag image acquisition unit

9c… Lag image analogy part

9d… Irradiation signal acquisition unit

9e… X-ray image acquisition unit

9f… Lag correction part

M… Subject

Example 1

[0029] Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an X-ray fluoroscopic apparatus according to Embodiment 1, and FIG. 2 is an equivalent circuit of a flat panel X-ray detector used in the X-ray fluoroscopic apparatus as viewed from the side. Figure 3 shows the equivalent circuit of a flat panel X-ray detector in plan view. In Example 1, including Examples 2 and 3 described later, a flat panel X-ray detector (hereinafter referred to as “FPD” as appropriate) is taken as an example of radiation detection means, and X-ray fluoroscopy is used as a radiation imaging device. A description will be given by taking a photographing apparatus as an example.

As shown in FIG. 1, the X-ray fluoroscopic apparatus according to the first embodiment includes a top plate 1 on which the subject M is placed, and an X-ray tube that irradiates the subject M with X-rays. 2 and FPD3 for detecting X-rays transmitted through the subject M. The X-ray tube 2 is compatible with the radiation irradiation means in the present invention. FPD3 corresponds to the radiation detection means in this invention.

[0031] The X-ray fluoroscopic apparatus also includes a top plate control unit 4 that controls the elevation and horizontal movement of the top plate 1, an FPD control unit 5 that controls scanning of the FPD 3, and a tube voltage of the X-ray tube 2. Output from the X-ray tube control unit 7 having the high voltage generator 6 that generates the tube current, the AZD modification 8 that extracts the X-ray detection signal that is a charge signal from the FPD3, and the AZD modification 8 The image processing unit 9 that performs various processing based on the X-ray detection signal, the controller 10 that controls each of these components, the memory unit 11 that stores processed images, and the operator set the input settings. It has an input unit 12 to perform and a monitor 13 to display processed images.

[0032] The top board control unit 4 horizontally moves the top board 1 to store the subject eyelid at the imaging position, or moves the top face up to the imaging position, sets the subject eyelid to a desired position by moving up and down, rotating and horizontally, Take an image while moving it horizontally, or move it horizontally after the image is taken and control it to retreat from the image position. The FPD control unit 5 performs control related to scanning by horizontally moving the FPD 3 or rotating it around the body axis of the subject's body. The high voltage generator 6 generates a tube voltage and a tube current for irradiating X-rays and applies them to the X-ray tube 2. The X-ray tube controller 7 moves the X-ray tube 2 horizontally, Rotating and moving around the axis of the body axis of the heel, controls the scanning, and controls the field of view of the collimator (not shown) on the X-ray tube 2 side. When scanning the X-ray tube 2 or the FPD 3, the X-ray tube 2 and the FPD 3 move while facing each other so that the FPD 3 can detect the X-rays emitted from the X-ray tube 2.

[0033] The controller 10 includes a central processing unit (CPU) and the like, and the memory unit 11 includes a storage medium represented by ROM (Read-only Memory), RAM (Random-Access Memory), and the like. It is configured. The input unit 12 includes a pointing device represented by a mouse, a keyboard, a joystick, a trackball, and a touch panel. In the X-ray fluoroscope, the FPD3 detects X-rays that have passed through the subject M, and based on the detected X-rays, the image processing unit 9 performs image processing to capture the subject M. I do.

[0034] Note that the image processing unit 9 performs non-irradiation of a plurality of X-ray detection signals before X-ray irradiation in imaging. A non-irradiation signal acquisition unit 9a that is acquired at the time of irradiation, a lag image acquisition unit 9b that acquires a lag image based on the X-ray detection signals acquired by the non-irradiation signal acquisition unit 9a, and detection of these radiations Among the lag information based on the signal, the lag image analogizing unit 9c that obtains the current lag information based on the past lag information and analogizes the lag image, and the irradiation signal acquired when the X-ray detection signal is emitted during the X-ray irradiation An acquisition unit 9d, an X-ray image acquisition unit 9e that acquires an X-ray image to be imaged based on the X-ray detection signal acquired by the irradiation signal acquisition unit 9d, and the X-ray image A lag correction unit 9f that removes lag from the X-ray image acquired by the acquisition unit 9e using the lag image estimated by the lag image analogization unit 9c described above is provided. X-ray image force By removing the lag using the lag image, the lag correction unit 9f performs lag correction related to the time delay by removing the time delay included in the X-ray detection signal from the X-ray detection signal. The non-irradiation signal acquisition unit 9a corresponds to the non-irradiation signal acquisition unit in the present invention, the lag image acquisition unit 9b corresponds to the lag image acquisition unit in the present invention, and the lag image analogy unit 9c Corresponding to the image analogy means, the irradiation signal acquisition unit 9d corresponds to the irradiation signal acquisition means in this invention, the X-ray image acquisition unit 9e corresponds to the radiation image acquisition means in this invention, and the lag correction unit 9f Corresponds to the lag correction means in the present invention.

In the first embodiment, unlike the second and third embodiments described later, the acquisition of the lag image by the lag image acquisition unit 9b and the analogy of the lag image by the lag image estimation unit 9c are synonymous. The lag image is analogized by acquiring the lag image. That is, in the first embodiment, the lag image acquiring unit 9b and the lag image analogizing unit 9c are used in common.

[0036] Note that the memory unit 11 includes a non-irradiation signal memory unit 1la for writing and storing each non-irradiation X-ray detection signal acquired by the non-irradiation signal acquisition unit 9a, and a lag image acquisition unit 9bZ. Acquired by the lag image analogizing unit 9c The lag image memory unit 1 lb for writing and storing the lag image estimated by Z and the irradiation X-ray detection signal acquired by the irradiation signal acquiring unit 9d for writing and storing A signal memory unit 1 lc and an X-ray image memory unit 1 Id for writing and storing the X-ray image acquired by the X-ray image acquisition unit 9e.

[0037] In the first embodiment, the lag image acquisition unit 9bZ lag image analogy unit 9c acquires the lag image based on each non-irradiation X-ray detection signal read from the non-irradiation signal memory unit 11a. analogy The lag image memory unit l ib is then written and stored (see FIG. 4). In Example 2 to be described later, the lag image acquisition unit 9b acquires a lag image based on each non-irradiation X-ray detection signal read from the non-irradiation signal memory unit 11a. Lag image memory unit 1 lb is written and stored, and each non-irradiated X-ray detection signal read from the non-irradiation signal memory unit 11a and lag image memory unit ib read from the lag image memory unit 11a. Based on the image, the lag image acquisition unit 9b corrects and analogizes the lag image, and writes and stores the corrected lag image in the lag image memory unit ib (see FIG. 10). In Example 3 described later, the acquisition of the lag image is performed by a recursive weighted average (recursive processing) described later (see FIG. 13).

As shown in FIG. 2, the FPD 3 also includes a glass substrate 31, a thin film transistor TFT formed on the glass substrate 31, and a force. As shown in FIG. 2 and FIG. 3, the thin film transistor TFT has a large number of switching elements 32 (for example, 1024 × 1024) formed in a vertical and horizontal two-dimensional matrix arrangement. The switching elements 32 are formed separately from each other. In other words, FPD3 is also a two-dimensional array radiation detector.

As shown in FIG. 2, an X-ray sensitive semiconductor 34 is laminated on the carrier collection electrode 33, and the carrier collection electrode 33 of the switching element 32 is formed as shown in FIGS. Connected to source S! A plurality of gate bus lines 36 are connected from the gate driver 35, and each gate bus line 36 is connected to the gate G of the switching element 32. On the other hand, as shown in FIG. 3, a multiplexer 37 that collects charge signals and outputs them to one is connected to a plurality of data bus lines 39 via amplifiers 38, as shown in FIGS. Thus, each data bus line 39 is connected to the drain D of the switching element 32.

[0040] With the bias voltage applied to the common electrode (not shown), the gate of the switching element 32 is turned ON by applying the voltage of the gate bus line 36 (or to OV), and the carrier collection electrode 33 is Then, the charge signal (carrier) converted through the X-ray sensitive semiconductor 34 incident on the detection surface side is read out to the data bus line 39 through the source S and drain D of the switching element 32. Until the switching element is turned on, the charge signal is The number is temporarily stored and stored in a capacitor (not shown). The charge signals read out to the data bus lines 39 are amplified by the amplifiers 38 and output together by the multiplexer 37 as one charge signal. The output charge signal is digitized by AZD converter 8 and output as an X-ray detection signal.

[0041] Next, by the non-irradiation signal acquisition unit 9a, the lag image acquisition unit 9b, the lag image estimation unit 9c, the irradiation signal acquisition unit 9d, the X-ray image acquisition unit 9e, and the lag correction unit 9f according to the first embodiment. A series of signal processing will be described with reference to the timing charts of FIGS. 5 and 8 and the flowcharts of FIGS. In this process, the process from the end of X-ray irradiation in the previous imaging to the X-ray irradiation in the current imaging will be described as an example.

[0042] (Step S1) Has the waiting time elapsed?

From the end of X-ray irradiation in the previous imaging, a predetermined waiting time T as shown in Fig. 5

W

It is determined whether or not the time has passed. Immediately after the end of irradiation, a short time constant component or a medium time constant component is included in the time delay. These time constant components in the short Z decay in a short time, and after the decay, the long time constant component becomes dominant and remains at almost the same strength. Therefore, a waiting time T is set so that an X-ray detection signal is acquired at the time of non-irradiation after a predetermined time elapses in the previous imaging, and after the waiting time T has passed, the next step is taken.

W W

Proceed to step S2. Whether or not the waiting time T has elapsed is determined by a timer (illustrated

W

(Omitted). In other words, the timer is reset to “0” simultaneously with the end of X-ray irradiation in the previous imaging, and the timer starts counting, which corresponds to the waiting time T.

W

It can be determined that the waiting time T has passed.

W

[0043] Also, the force waiting time T due to the individual lag characteristics of FPD3 is preferably about 15 seconds.

W

Just 30 seconds is enough. The longer the waiting time T is, for example, 30 seconds or more.

W

Although it is desirable, if the time is too long, the time between photographing is extended. Therefore, in practice, the waiting time T is about 3 seconds.

W

[0044] (Step S2) Acquisition of X-ray detection signal at non-irradiation

The non-irradiation signal acquisition unit 9a samples each X-ray detection signal during non-irradiation after the waiting time T has elapsed.

W

Pulling time Acquired sequentially every ΔΤ1 interval. Sampling count until the start of X-ray irradiation in this imaging is (N + 1) (where K = 0, 1, 2, ...,,-1, Ν) The first subscript to be acquired immediately after the waiting time T has elapsed is Κ = 0. And (K + 1) number

W

If the X-ray detection signal acquired by the eye is I, κ w is acquired first immediately after the waiting time τ elapses.

X-ray detection signal is I, X acquired immediately before the start of X-ray irradiation in this imaging

0

The line detection signal is I. Note that steps S2 to S5 are continued every sampling time ΔΤ1.

N

Suppose you do.

[0045] (Step S3) Has this imaging been reached?

At the time of acquisition of the X-ray detection signal in step S2, that is, the sampling time force It is determined whether or not the start of X-ray irradiation in the current imaging has been reached (here, the force at which K = N + 1). If so, jump to step S6. If not, go to the next step S4.

[0046] (Step S4) Raise K by 1

Prepare the next sampling by incrementing the value of the subscript K by one.

[0047] Reject X-ray detection signal before (Step S5)

X-ray detection signal I acquired by non-irradiation signal acquisition unit 9a in step S2 is not irradiated

K

Write and store in the signal memory unit 11a. At this time, before X-ray detection signal I

K

The X-ray detection signal I acquired at the point (ie, the previous X-ray detection signal) is no longer necessary.

K-2

Reject with. Therefore, only the latest X-ray detection signal and the X-ray detection signal acquired at the previous time point are stored in the non-irradiation signal memory unit 11a. In step S4, if X is increased from K = 0 to K = 1 and the process proceeds to step S5, or if step S4 is increased from Κ = 1 to Κ = 2 and the process proceeds to step S5, the X-ray detection signal I Earlier than

0

Since there is no X-ray detection signal, there is no need to reject it. Then, return to step S2 for the next sampling, and repeat steps S2 to S5 every sampling time ΔΤ1 interval. In the first embodiment, the force that rejects the previous X-ray detection signal and leaves only the latest X-ray detection signal and the X-ray detection signal acquired at the previous time, of course, does not necessarily need to be rejected. Steps S2 to S5 described above correspond to the non-irradiation signal acquisition step in this invention.

[0048] (Step S6) Acquisition of lag image Z analogy

In step S3, the sampling time reached the start of X-ray irradiation in the current imaging The (N + 1) th X-ray detection signal I acquired in step S2 and the previous time N

N

The Nth X-ray detection signal I that was the previous point in time

N- 1 As the lag information of N-1, the X-ray detection signal I and the past lag information (X-ray detection signal I)

Obtain the lag image that is the current lag information based on N N- 1 z Analogy. That is, the lag image acquisition unit 9bZ lag image analogy unit 9c does not receive the X-ray detection signal I acquired immediately before the start of X-ray irradiation in this imaging and the X-ray detection signal I acquired at the previous time point. Irradiation signal

N N- 1

The data is read from the memory unit 11a, the coefficient is obtained in step S601 (see FIG. 7), and the lag image is estimated using the coefficient in step S602 (see FIG. 7).

[0049] (Step S601) Obtain coefficients

X-ray detection signal I acquired just before the start of X-ray irradiation I

Using N as the numerator, the X-ray detection signal I obtained at the previous time point is used as the denominator, and the coefficient C is obtained as shown in the following equation (1).

N- 1 N

[0050] C = 1 ÷ Ι · '· (1)

N N N- 1

Therefore, the coefficient C

N is a coefficient expressed by the signal ratio related to the X-ray detection signal acquired during the past non-irradiation. Specifically, the past X-ray detection signal (X-ray detection signal acquired in steps S2 to S5). I) is a coefficient expressed as a signal ratio. The coefficient C is

Corresponds to the coefficient represented by the signal ratio related to the radiation detection signal acquired during past non-irradiation in the N- 1 N invention, and the signal related to the past radiation detection signal acquired in the non-irradiation signal acquisition process in this invention. This also corresponds to the coefficient expressed as a ratio, and also corresponds to past lag information in the present invention.

[0051] (Step S602) Analogize lag images using coefficients

Using the coefficient C obtained in step S601, the lag image L is obtained as shown in equation (2) below.

N X

I will.

[0052] L = C X I--(2)

X N N

As shown in equation (2) above, the coefficient C is applied to the X-ray detection signal I acquired immediately before the start of X-ray irradiation.

N

Lag image L by multiplying N

Get X Z analogy. Then, the lag image acquisition unit 9bZ lag image analogization unit 9c writes and analogizes the lag image L to the lag image memory unit 1 lb.

X

Remember me. Step S6 including steps S601 and 602 corresponds to the lag image acquisition step and the lag image analogy step in the present invention. In the first embodiment, as described in the description of the image processing unit 9, the lag image acquisition process and the lag image analogization process are the same process, and the lag image in the lag image acquisition process. As a result, the lag image is analogized in the lag image analogy process. Therefore, the acquisition of the lag image in the lag image acquisition process and the analogy of the lag image in the lag image analogization process are synonymous.

[0054] (Step S7) Acquisition of X-ray detection signal during irradiation

When the X-ray irradiation in the current imaging is finished, the irradiation signal acquisition unit 9d acquires the X-ray detection signal at the time of irradiation obtained by the irradiation. The X-ray detection signal at the time of irradiation acquired by the irradiation signal acquisition unit 9d is written and stored in the irradiation signal memory unit 1lc. This step S7 corresponds to the irradiation signal acquisition step in the present invention.

[0055] (Step S8) Acquisition of X-ray image by current imaging

Based on the X-ray detection signal at the time of irradiation acquired in step S7, the X-ray image acquisition unit 9e acquires the X-ray image to be captured this time. Let this X-ray image be X. The X-ray image X acquired by the X-ray image acquisition unit 9e is written and stored in the X-ray image memory unit id. This step S8 corresponds to the radiation image acquisition step in this invention. Further, the X-ray image X corresponds to a radiographic image to be imaged in the present invention.

[0056] (Step S9) Lag correction

The lag correction unit 9f uses the lag image L acquired in step S6 as the lag image memory unit l ib.

X

The X-ray image X acquired in step S8 is read from the X-ray image memory unit l id and the lag image L is subtracted from the X-ray image X. The X-ray image after lag correction is

X

Then Y = X-L.

X

[0057] In practice, the timing of X-ray irradiation in the current imaging is not necessarily determined in advance. Therefore, the timing to reach K = N + 1 is not always in advance. Therefore, in practice, steps S2 to S5 described above are repeatedly performed at every sampling time interval, and when the sampling time reaches the start of X-ray irradiation in the current imaging in step S3, the force K = N + 1 is set. It is time to reach. Of course, if the timing of X-ray irradiation in this imaging is determined in advance, the timing of reaching K = N + 1 is also known in advance, so the value of N is determined in advance and K = N + 1 The sampling time may be set so as to reach the start of X-ray irradiation in the current imaging in accordance with the timing of reaching. This step S9 corresponds to the lag correction step in this invention.

[0058] According to the first embodiment configured as described above, the non-irradiation signal acquisition unit 9a includes a plurality of X-ray detection signals (this embodiment) detected from the flat panel X-ray detector (FPD) 3. In Example 1, I,

0

1, 1, ..., I, I) are acquired at the time of non-irradiation before X-ray irradiation in imaging. Non-light

1 2 N- 1 N

Among the lag information based on the X-ray detection signals acquired by the radiation signal acquisition unit 9a, the past lag information (in the first embodiment, the X-ray detection signal I and the coefficient C acquired at the previous time point)

Based on N- 1 N, the lag image analogy unit 9c obtains the current lag information (lag image L) and performs analogy

X

On the other hand, the irradiation signal acquisition unit 9d acquires the X-ray detection signal detected from the FPD 3 at the time of X-ray irradiation in imaging. Based on the X-ray detection signal acquired by the irradiation signal acquisition unit 9d, the X-ray image acquisition unit 9e acquires an X-ray image to be imaged.

[0060] Then, lag removal is performed from the X-ray image acquired by the X-ray image acquisition unit 9e using the lag image estimated by the lag image estimation unit 9c described above, thereby being included in the X-ray detection signal. The lag correction unit 9f performs lag correction related to the time lag by removing the time lag from the X-ray detection signal force.

In this way, it is not necessary to perform lag correction by performing recursive arithmetic processing for the number of times of sampling for acquiring an X-ray detection signal as in Patent Document 2 described above. Furthermore, based on the past lag information (X-ray detection signal I and coefficient C), the lag image estimation unit 9c

N- 1 N

Report (lag image L) and analogize it.

X

The time has passed (within 1 minute)! / Wow! / In some cases, X-ray detection signal I (lag

N

However, even if the amount of lag decreases (see Fig. 8), it is possible to infer a lag image considering past lag information. As a result, the lag data, which is the time delay, can be estimated appropriately. Therefore, by simply removing the lag using this analogized lag image, the time delay included in the X-ray detection signal can be easily removed while also properly estimating the time delay as the lag data. can do. Further, the structure of the apparatus that does not require the use of a backlight as in Patent Document 1 described above does not become complicated. [0062] It should be noted that in Example 1, including Examples 2 and 3 described later, a coefficient C (described later) is set for each pixel.

N

In the second and third embodiments, the correction coefficient) is preferably obtained, and the current lag information (lag image L) is preferably obtained for each pixel based on each coefficient. Lag data attenuation characteristics for each pixel

X

Therefore, a high-quality X-ray image with no lag can be obtained by calculating in this way.

[0063] In the present embodiment 1, including later-described embodiments 2 and 3, a plurality of X's at the time of non-irradiation after the elapse of a predetermined time (the waiting time T in the present embodiment 1) has elapsed since the X-ray irradiation in the previous imaging. Line detection

W

By acquiring the signals, multiple X-ray detection signals at the time of non-irradiation before X-ray irradiation in this imaging are acquired. When the X-ray irradiation in the previous imaging is completed and the state shifts to the non-irradiation state, the short time constant component or medium time constant component of the time delay is attenuated in a short time, and after attenuation, the long time constant component is It becomes dominant and continues to remain at about the same strength. Therefore, conventionally, when an X-ray detection signal is acquired immediately after the end of X-ray irradiation in the previous imaging, a signal is acquired with a short Z medium time constant component, and the short / The time delay of the medium time constant component cannot be correctly removed. This is the same as explained in Fig. 8 and conventional Fig. 16. Therefore, as in the present invention, the present lag information is obtained based on the past lag information and the lag image is inferred, thereby taking into account the past lag information including the time delay of the short Z medium time constant component. The lag image can be inferred, and the X-ray irradiation power in the previous imaging is also the predetermined time (in this example 1, the waiting time T

W

) The time delay component of the short Z medium time constant component can be correctly removed even after the passage of time.

[0064] Of course, as in the first embodiment, the X-ray irradiation power in the previous imaging may be acquired as a plurality of X-ray detection signals at the time of non-irradiation after a predetermined time has passed, or the X-rays in the previous imaging may be acquired. Multiple X-ray detection signals may be acquired during non-irradiation without much time elapse from irradiation. As in Example 1, the X-ray irradiation power in the previous imaging is acquired at the time of non-irradiation before X-ray irradiation in the current imaging by acquiring multiple X-ray detection signals at the time of non-irradiation after the lapse of a predetermined time. Multiple X-ray detection signals at the time of acquisition, and the signal is acquired with only a long time constant component remaining after a predetermined time has elapsed. It is possible to accurately remove the time delay of the long time constant component with no time delay.

Example 2 Next, Embodiment 2 of the present invention will be described with reference to the drawings. FIG. 9 is a block diagram of the fluoroscopic imaging apparatus according to the second and third embodiments, and FIG. 10 is a schematic diagram illustrating a data flow regarding the image processing unit and the memory unit according to the second embodiment. The portions common to the above-described first embodiment are denoted by the same reference numerals, and the description thereof is omitted. As shown in FIG. 9, the X-ray fluoroscopic apparatus according to Example 2, including Example 3 to be described later, separately uses the lag image acquisition unit 9b and the lag image analogy unit 9c separately from each other. Except for being independent, the configuration is the same as that of the fluoroscopic imaging apparatus according to the first embodiment. In addition, the data flow related to the image processing unit 9 and the memory unit 11 in FIG. 10, the non-irradiation signal acquisition unit 9a, the lag image acquisition unit 9b, the lag image analogy unit 9c, the irradiation signal acquisition unit 9d, and the X-ray image acquisition The series of signal processing by the unit 9e and the lag correction unit 9f is also different from the first embodiment.

In the second embodiment, as shown in FIG. 10, the lag image acquisition unit 9b performs lag image based on each non-irradiation X-ray detection signal read from the non-irradiation signal memory unit 11a. Is acquired and stored in the lag image memory unit l ib, read from the non-irradiation signal memory unit 11a and read from each non-irradiated X-ray detection signal and lag image memory unit l ib. Based on the lag image, the lag image analogizing unit 9c corrects and analogizes the lag image, and writes and stores the corrected lag image in the lag image memory unit 1 lb. If the previous lag image is the past lag information, the lag image obtained by the lag image acquisition unit 9b is corrected based on the above-mentioned past lag information (previous lag image), so that the lag image analogy unit 9c Infers the corrected lag image. In the case of the second embodiment, the analogy of the lag image includes a function of correcting the lag image obtained before correction, and the lag image is acquired after the lag image acquisition unit 9b acquires the lag image. In order to make an analogy, the lag image obtained before correction is corrected by the lag image analogy unit 9c.

[0067] Next, the non-irradiation signal acquisition unit 9a, the lag image acquisition unit 9b, the lag image estimation unit 9c, the irradiation signal acquisition unit 9d, the X-ray image acquisition unit 9e, and the lag correction unit 9f according to the second embodiment. A series of signal processing will be described with reference to the flowcharts in FIGS. Note that the steps common to the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.

[0068] (Step S1) Has the waiting time elapsed?

As in the case of Example 1 described above, it is waited after the end of X-ray irradiation in the previous imaging. Judge whether the interval T has elapsed. After waiting time Τ has passed, the next step S12

W W

Proceed to

[0069] (Step S12) Acquisition of X-ray detection signal at non-irradiation

As in Example 1 above, each X-ray detection signal during non-irradiation after elapse of waiting time

W

Are acquired sequentially every sampling time ΔΤ1 interval (for example, 1Z30 seconds). However, in Example 2, as will be apparent from the following description, until the eighth X-ray detection signal 1 ₇ (that is, Κ = 7) is acquired, it is first acquired immediately after the elapse of the waiting time Τ. X-ray detection signal I

Non-irradiated signal memory section without being rejected until the seventh X-ray detection signal I obtained from W 0

6

1 la memorized. It is assumed that steps S12 to S14 are continuously performed at every sampling time interval.

[0070] (Step S13) K = 7?

Whether the subscript K has reached 7, that is, whether the sampling time has reached 8th (here K

= Power that reaches 7) Judge whether or not. If so, jump to step S2. If not, go to the next step S14.

[0071] (Step S14) Raise the value of K by 1

As in Example 1 above, the value of the subscript K is incremented by 1 to prepare for the next sampling. Until the eighth X-ray detection signal I (that is, K = 7) is acquired, each X-ray detection signal I acquired by the non-irradiation signal acquisition unit 9a in step S12 is obtained.

K

The non-irradiation signal memory unit 11a is sequentially written and stored. At this time, from X-ray detection signal I

K

X-ray detection signal I acquired at the previous time

K-1 is not rejected, but is stored in the non-irradiation signal memory unit 11a until it contains eight X-ray detection signals. Then, the process returns to step S12 for the next sampling, and steps S12 to S14 are repeated every sampling time interval.

[0072] (Step S21) Acquisition of a lag image

When the sampling time reaches the eighth in step S13, the lag image acquisition unit 9b acquires a lag image based on each non-irradiation X-ray detection signal read from the non-irradiation signal memory unit 11a. Specifically, as described above, eight X-ray detection signals are always stored in the non-irradiation signal memory unit 11a, and the latest X-ray detection is newly performed in step S2. When the output signal is stored in the non-irradiation signal memory unit 11a, only the oldest X-ray detection signal is rejected in step S51 described later. On the other hand, the (K−6) th X-ray detection signal I stored in the non-irradiation signal memory unit 11a and the (K + 1) th X-ray detection signal I are stored.

The lag image L is obtained based on 8 signals at K-7 K. Specifically, the level of these signals

K

The average is obtained as a lag image L (L = ∑1 / 8, where ∑ is 1 =: «: -7 to: <<: the sum of :). So

K K i

Then, the lag image acquired by the lag image acquisition unit 9b is written and stored in the lag image memory unit 1 lb. This step S21 corresponds to the lag image acquisition step in this invention.

[0073] (Step S611) Obtain Correction Factor

Of the (K + 1) th X-ray detection signal I and the previous lag image L, the previous lag image

K K- 1

With L as past lag information, the X-ray detection signal I and past lag information (X-ray detection)

K- 1 K

Lag image L is corrected based on the

K- 1 K

Analogize image L. That is, the lag image analogizing unit 9c performs the (K + 1) th X-ray detection signal I

X

Is read from the non-irradiation signal memory unit 11a and the previous lag image L

K K- 1

This is estimated by reading out from the image memory unit l ib, obtaining a correction coefficient in step S611, and correcting the lag image using the correction coefficient in step S612 described later. Using the (K + 1) th X-ray detection signal I as the numerator and the previous lag image L as the denominator,

K K- 1

The correction coefficient c is obtained as follows.

K

[0074] C = 1 ÷ L

K K K- 1

Therefore, the correction factor C is related to the X-ray detection signal acquired during past non-irradiation.

K

This is a coefficient expressed by the signal ratio, specifically, a correction coefficient related to the past X-ray detection signal acquired in steps S2 to S5 and expressed by the signal ratio of the previous lag image L.

K- 1

is there. The correction coefficient c is the radiation detection acquired at the past non-irradiation in this invention.

K

This corresponds to the coefficient represented by the signal ratio related to the signal, corresponds to the coefficient represented by the signal ratio related to the past radiation detection signal acquired in the non-irradiation signal acquisition step in the present invention, and the past lag information in the present invention. It corresponds to.

[0075] (Step S3) Has this imaging been reached?

As in Example 1 above, the X-ray detection signal acquisition time, that is, the sampling time force, has reached the start of X-ray irradiation in this imaging (in this case K = N + 1) Judgment force) or not. If reached, jump to step S612. If not, go to the next step S4.

[0076] (Step S4) Raise K by 1

Subscript K is incremented by one to prepare for the next sampling, acquisition of the lag image (before correction) and acquisition of correction factors.

[0077] Reject X-ray detection signal before (Step S51)

As in the first embodiment described above, the oldest X-ray detection signal is no longer necessary and is rejected. In other words, as described above, the non-irradiation signal memory unit 11a always stores eight X-ray detection signals, and in step S2, the latest X-ray detection signal is newly not irradiated. When stored in the signal memory unit 11a, only the oldest X-ray detection signal is rejected.

[0078] (Step S2) Acquisition of X-ray detection signal at non-irradiation

As in the first embodiment described above, a new X-ray detection signal is acquired during non-irradiation. And

Step S21 for the next sampling, acquisition of the lag image (before correction) and acquisition of the correction coefficient. Repeat S4, S51, and S2. By repeating this, the correction coefficient C obtained in step S611 is also updated by incrementing the value of the subscript K by one.

K

[0079] (Step S612) Analogize the lag image using the correction coefficient

When the sampling time in step S3 reaches the start of X-ray irradiation in the current imaging, it was acquired in step S21 using the correction coefficient C obtained in step S611 (

N

It is corrected by acting on the lag image L before correction. Open X-ray irradiation in this imaging

N

Since the sampling point that reached the beginning is a point when K = N + 1, the correction coefficient obtained in step S611 is C, and the lag image (before correction) acquired in step S21 is L. The

N N

Using the correction coefficient C obtained in step S611, the lag image L is

N X

Ask.

[0080] L = C X L--(2) '

X N N

The coefficient C in the above equation (2) in the first embodiment is the correction factor in the above equation (2) 'in the second embodiment.

N

The number C. The lag image acquired immediately before the start of X-ray irradiation as shown in equation (2) 'above.

N

By multiplying L by the correction coefficient C, the lag image L is corrected and the corrected lag image L is Analogy. Then, the corrected lag image L estimated by the lag image analogizing unit 9c is used as the lag image.

X

Write to memory 1 lb for storage. This step S612 including the above-described step S611 corresponds to the lag image analogy process in the present invention.

[0081] In the second embodiment, as described in the description of the image processing unit 9, after the acquisition of the lag image in the lag image acquisition process, the lag image was obtained in advance. The lag image is corrected in the lag image acquisition process (before correction). Therefore, in the case of the second embodiment, the analogy of the lag image includes the function of correcting the lag image obtained previously.

[0082] (Step S7) Acquisition of X-ray detection signal during irradiation

Since it is the same as the first embodiment described above, description thereof is omitted.

[0083] (Step S8) Acquisition of X-ray image by current imaging

[0084] (Step S9) Lag Correction

According to the second embodiment configured as described above, as in the first embodiment described above, a plurality of X-ray detection signals (this book) acquired at the time of non-irradiation before X-ray irradiation in imaging are used. In Example 2, II

N-7, 1

Among the lag information based on (N-6, ... N-1, N), the past lag information (in the second embodiment, the previous lag image L and correction coefficient C) is used to determine the current lag information ( Corrected lag

K- 1 K

Since the image L) is obtained and analogized, the past lag information (in the second embodiment, the previous lag image)

X

L and the correction factor C) can be inferred, and this analogy

K- 1 K

By simply removing the lag using the lag image, it is possible to easily remove the time lag included in the X-ray detection signal from the X-ray detection signal while properly analogizing the lag data that is the time lag. .

[0086] In the second embodiment, the lag image L (before correction) is obtained by directly using eight X-ray detection signals.

K

The number of X-ray detection signals to be used is not limited. Also, the force that found the lag image L by the average of the signals, for example, the lag image L obtained by the median, or the signal strength

K K

Taking a histogram of degree, the histogram power is also determined as the lag image L.

K

The specific method for obtaining the lag image L is not particularly limited.

K

[0087] It should be noted that the correction coefficient C is obtained for each pixel in the second embodiment, including the third embodiment described later. Therefore, each correction coefficient is applied to the lag image L (before correction) for each pixel for correction.

N

preferable. Since the attenuation characteristics of lag data differ for each pixel, a high-quality X-ray image without lag can be obtained by calculating in this way.

Example 3

Next, Embodiment 3 of the present invention will be described with reference to the drawings. FIG. 13 is a schematic diagram illustrating a data flow regarding the image processing unit and the memory unit according to the third embodiment. The parts common to the above-described embodiments 1 and 2 are denoted by the same reference numerals and the description thereof is omitted. Further, the X-ray fluoroscopic apparatus according to the third embodiment has the same configuration as that of the X-ray fluoroscopic apparatus according to the second embodiment except for the data flow related to the image processing unit 9 and the memory unit 11 in FIG. is there. Also, a series of signal processing by the non-irradiation signal acquisition unit 9a, lag image acquisition unit 9b, lag image analogy unit 9c, irradiation signal acquisition unit 9d, X-ray image acquisition unit 9e, and lag correction unit 9f This is different from Examples 1 and 2.

In Example 3, as shown in FIG. 13, the non-irradiation X-ray detection signal read from the non-irradiation signal memory unit 11a and the lag image memory unit 1 lb were read out. Based on the previous lag image (before correction), the lag image acquisition unit 9b acquires the lag image L (before correction) by recursive calculation processing. Regarding the acquisition of lag image L by recursive calculation processing,

K K

This will be described with reference to the flowchart of FIG. A lag image L (before correction) is acquired through recursive calculation processing. For other data flows, the above-mentioned implementation

K

Same as Example 2.

[0090] Next, by the non-irradiation signal acquisition unit 9a, the lag image acquisition unit 9b, the lag image estimation unit 9c, the irradiation signal acquisition unit 9d, the X-ray image acquisition unit 9e, and the lag correction unit 9f according to the third embodiment. A series of signal processing will be described with reference to the flowchart of FIG. Note that the steps common to the above-described embodiments 1 and 2 are denoted by the same reference numerals and description thereof is omitted.

[0091] (Step S1) Has the waiting time elapsed?

As in the first and second embodiments described above, it is determined whether or not the waiting time T has elapsed since the end of X-ray irradiation in the previous imaging. After waiting time T has passed, the next step S

W W

Proceed to 102.

[0092] (Step S102) Acquisition of X-ray Detection Signal Immediately after Elapse of Waiting Time As in Examples 1 and 2 above, each X-ray detection signal is not irradiated after waiting time T has elapsed.

W

The signal is acquired sequentially every sampling time ΔΤ1 interval (for example, 1Z30 seconds). First, the X-ray detection signal I immediately after the elapse of the waiting time Τ is acquired. This waiting time

The X-ray detection signal I acquired at W 0 W is written and stored in the non-irradiation signal memory unit 1 la.

0

[0093] (Step S103) Acquisition of Initial Value Lag Image

Then, the lag image acquisition unit 9b sends the X-ray detection signal I to the non-irradiation signal memory unit 11a.

0

The X-ray detection signal I is read as the lag image L, which is the initial value of the lag image L.

0 K 0 get. Then, the initial value of the lag image L acquired by the lag image acquisition unit 9b is converted into the lag image.

0 Image memory unit Write to 1 lb and store.

[0094] (Step S2) Acquisition of X-ray detection signal at non-irradiation

Obtain the second X-ray detection signal I at the sampling time (K = l). The second X-ray detection signal I is written and stored in the non-irradiation signal memory unit 11a.

[0095] (Step S21), (Step S611), (Step S3), (Step S4), (Step S51), (Step S2), (Step S612), (Step S7) to (Step S9)

When the second X-ray detection signal I is obtained in step S2, steps S21, S611, S3, S4, S51, S2, S612, and S7 to S9 similar to those in the second embodiment are performed. However, when the lag image L (before correction) is acquired in step S21, the (K + 1) -th lag image L is not illuminated.

K K

Non-irradiation X-ray detection signal I and lag image read from the emission signal memory unit 11a

K

It is obtained by recursive calculation processing based on the previous lag image L read from the memory unit l ib.

K- 1

I will. In the third embodiment, the lag image L is acquired by the recursive weighted average (hereinafter referred to as “recursive processing” as appropriate) as shown in the following equation (3).

K

[0096] L = (1 -P) X L + P X I · '· (3)

Κ Κ- 1 κ

However, as described above, I = L. P is a weighted ratio and takes a value between 0 and 1.

0 0

[0097] Further, through these series of recursive processes, the lag image obtained at the sampling time point when the X-ray irradiation start in the current imaging is reached becomes L. And step S61

N

As in step 1, the correction coefficient C is calculated using the above equation (1) 'and the same as step S612.

K

Similarly, the lag image L is obtained by using the above equation (2) ′. According to the third embodiment configured as described above, the past lag information (the previous lag image L and the correction coefficient C in the third embodiment) is the same as in the first and second embodiments described above. Based on

K- 1 K

Since the current lag information (corrected lag image L) is obtained and analogized, past lag information (this

X

In Example ³ , the lag image considering the previous lag image L and the correction coefficient C) is analogized.

K- 1 K

By simply removing the lag using this analogized lag image, the time lag included in the X-ray detection signal can be converted to the X-ray detection signal power while properly analogizing the lag data. It can be easily removed.

[0099] In the case of the third embodiment, since the lag image is acquired by the recursive processing (see the above formula (3)) that is a recursive weighted average as the recursive arithmetic processing, the lag correction is more reliably performed. It can be carried out.

[0100] Fig. 15 shows the results of applying Example 3 to actual data measured using a 17-inch direct conversion flat panel X-ray detector (FPD). At time 0 seconds, X-ray conditions (125 KV, 3.2 mAs) equivalent to frontal chest imaging were performed! The force was also plotted for 60 seconds of non-irradiated data (ie, lag). In the figure, S is the lag of the direct irradiation part, S is

A C

Copper plate lmm transmission X-ray lugs are shown respectively. The signal attenuation of this lag indicates that, for example, if imaging is performed at 15 seconds (see the arrow in the figure), afterimages, the afterimage of the previous imaging with a signal value of about 70 overlaps on the direct line. .

[0101] On the other hand, when Example 3 is applied, the signal attenuation of the lag is S or S.

B D

become. S is the lag correction of the direct irradiation part, S is the transmission plate X-ray lag correction of the copper plate lmm

B D

Each is shown below. As can be seen from the graph in Fig. 15, significant lag correction is possible. In Fig. 15, the lag of the previous imaging can be corrected even if the next imaging is performed 5 seconds after the previous imaging in which the short-Z medium time constant component is dominant.

[0102] The present invention is not limited to the above-described embodiment, and can be modified as follows.

(1) In each of the above-described embodiments, the X-ray fluoroscopic apparatus as shown in FIG. 1 has been described as an example. However, the present invention is, for example, an X-ray fluoroscopic apparatus disposed on a C-type arm. It may also be applied to equipment. The present invention may also be applied to an X-ray CT apparatus. Note that the present invention is particularly useful when performing actual imaging (not through fluoroscopic imaging) like an X-ray imaging apparatus. (2) In each of the above-described embodiments, the flat panel X-ray detector (FPD) 3 has been described as an example. However, the present invention can be applied to any X-ray detection means that is normally used. can do.

[0105] (3) In each of the above-described embodiments, an X-ray detector for detecting X-rays has been described as an example. However, the present invention provides a radioisotope (RI) as in an ECT (Emission Computed Tomography) apparatus. ) Is not particularly limited as long as it is a radiation detector that detects radiation, as exemplified by a γ-ray detector that detects y-rays radiated from a subject administered. Similarly, the present invention is not particularly limited as long as it is an apparatus that detects an image by detecting radiation as exemplified by the ECT apparatus described above.

[0106] (4) In each of the above-described embodiments, the FPD 3 includes a radiation (X-ray in the embodiment) sensitive semiconductor, and directly converts the incident radiation into a charge signal with the radiation sensitive semiconductor. This is a conversion-type detector, but instead of a radiation-sensitive type, it is equipped with a photo-sensitive type semiconductor and a scintillator. The incident radiation is converted into light by the scintillator, and the converted light is converted into a photo-sensitive type semiconductor. This is an indirect conversion detector that converts the signal into a charge signal.

(5) In each of the above-described embodiments, the X-ray irradiation power in the previous imaging is a predetermined time (in each embodiment, the waiting time Τ) X

The force that started acquiring the line detection signal when no irradiation was performed after the elapse of W Good. The same applies to radiation other than X-rays. Conventionally, the time constant component of the short Ζ is dominant, but the time constant of the short ζ is obtained by analogizing the lag image by obtaining the current lag information based on the past lag information as in the present invention. It is possible to infer a lag image that takes into account past lag information including the time delay of the component, and the X-ray irradiation power in the previous imaging is also a predetermined time (wait time τ in each example)

W

Even after the lapse of time, the time delay component of the short time constant component can be correctly removed.

(6) In each of the embodiments described above, the lag image that is the basis of lag correction is the X-ray detection signal I acquired immediately before the start of X-ray irradiation in the current imaging.

The force that included the spider data is always the X-ray detection signal I

It is not necessary to include cocoon data. However, since the data power S immediately before S is more reliable, the lag image including the data of the X-ray detection signal I is used as in each example. It is preferable to perform lag correction by acquiring an image and removing the lag using the lag image. The same applies to radiation other than X-rays.

[0109] (7) In each of the embodiments described above, an example of past information is a coefficient represented by a signal ratio related to a radiation detection signal acquired at the time of past non-irradiation, and this time based on the coefficient. An example of combining the above-described example of finding the lag information and estimating the lag image with Example 1 and correcting the lag image by applying the correction coefficient to the lag image (before correction) The force described as an example of combining the above-described example of estimating the corrected lag image as the lag information this time and the second and third embodiments is not limited to this.

[8] (8) In each of the above-described examples, the past information is a coefficient (correction coefficient in Examples 2 and 3) represented by a signal ratio related to the radiation detection signal acquired at the past non-irradiation. However, it is not limited to such a signal ratio, and the radiation detection signal itself acquired at the time of past non-irradiation or a signal obtained by multiplying the signal by a constant may be used.

(9) In each of the above-described embodiments, the coefficient (the correction coefficient in Embodiments 2 and 3) is represented by the signal ratio as in the above equation (1) or (1) '. It is not limited. That is, in each embodiment, the coefficient C (which is a signal ratio) is maintained after one sampling (after one frame).

K

Assume that. For this ratio, it can be considered that the next frame (that is, the next sampling time point) is approximated by a constant value and is updated sequentially. Therefore, the case of generalization to the nth order will be described in detail below.

[0112] Since the lag decreases momentarily over time, the ratio can be considered as a function of time, and if it changes sufficiently smoothly, until the next frame (the next sampling point) If the time is limited, the coefficient C is approximated by the following equation (4)

K

(Kappa is time).

[0113] C = AXK ^N + AXK ^N_1 H—— hA Χ Κ '+ Α ·' · (4)

Κ Ν Ν- 1 1 0

The order する is determined separately as appropriate. The signal ratio C changes with time.

Κ

It can also be regarded as a “signal intensity change ratio”.

[0114] Taking Examples 2 and 3 as an example, a plurality of lag images before correction are represented as L 1, L 2, κ-τ K-T + 1

· · · · L (where τ is any positive number). Each of these lag images and (K + 1) th

K- 1

The signal ratio is determined by the ratio to the X-ray detection signal I. C, c ,… ゝ C, C = 1 ÷ L, C = 1 ÷ L,… ゝ C = I ÷ L

K K-T + l K K-T K-T + 2 K K-T + l K K K-l Each signal ratio is determined.

[0115] A specific polynomial (polynomial coefficient A) is determined from these equations, and the polynomial is used.

I

Therefore, the correction coefficient C for the next frame (at the next sampling time) is predicted and included in the X-ray image.

K +1

Analogize the lag image L. It should be noted that the above-described Examples 2 and 3 are assumed to follow the 0th order equation.

X

Make it.

[0116] For example, if the signal ratio (signal strength change ratio) follows the following formula: C = 1 / L

K-l K Κ-2

, C = 1 ÷ L, find each coefficient of the polynomial, and according to the determined C polynomial,

K K K-l K

Eventually, the correction coefficient for the next frame (next sampling time) can be obtained as shown in the following equation (5).

[0117] C = 2XC C --- (5)

K + l K K-1

C and C on the right side of equation (5) above are obtained from C = 1 / L and C = 1 / L

Κ Κ-1 Κ-1 Κ Κ-2 Κ Κ Κ-1

, C on the left side, which is the correction coefficient for the next frame (next sampling time)

K + 1

Ask. When Κ is raised by 1 at the next frame (at the next sampling time), the right side of equation (5) is also the force that raises to C and C respectively.

Κ + 1 Κ

C and C on the right side of Eq. (5) are calculated as follows: C = 1 ÷ L

Κ + 1 Κ +1 κ κ κ κ-ι

Find C = 1 ÷ L, and find C on the left side from Equation (5).

K + 1 K K K + 2

[0118] When the start of X-ray irradiation in the current imaging is reached, that is, when X-ray irradiation is performed, the correction coefficient at the sampling time point when the X-ray irradiation starts in the current imaging is reached is C. , Find C and C from known L, L, 1 and correspond to the right side of equation (5)

N +1 N-2 N-1 N N-1 N

Ask for C, Jikamoji. Then, using the correction coefficient C, the lag before correction

N-1 N N + 1 N + 1

By correcting the image L, the lag image L included in the X-ray image is analogized (L = C X

N X X N + 1

L).

N

[0119] If the signal ratio (signal strength change ratio) follows the quadratic equation, C = 1 / L,

K-2 K K-3

Polynomial of C determined by calculating each coefficient of the polynomial from C = 1 ÷ L and C = 1 ÷ L

According to the equation K-l K K-2 K K K-l K, the correction coefficient for the next frame (next sampling point) can be finally obtained as shown in equation (6) below.

[0120] C = 3XC -3XC + C --- (6)

K + 1 K Kl K-2 C is obtained in the same manner as in the case of following the linear equation, and the lag image is obtained using the correction coefficient C.

N + 1 N + 1

Analogy with L. In the same way, even if the order increases with the cubic, quartic, etc.

Calculate from X N + 1 value.

[0121] Increasing the order can reduce errors and increase accuracy. If the order increases, the necessary past lag information is required according to the order, and the amount of calculation increases. Therefore, the order may be determined by a trade-off between the required accuracy and the allowable calculation time. Note that the coefficient C described above depends on the lag image L before correction.

K K

Since it is updated every time, even if not much time (within 1 minute) has elapsed since the X-ray irradiation in the previous imaging, it can be flexibly followed.

(10) In Embodiment 3 described above, the recursive weighted average (recursive processing) as shown in the above equation (3) is used. It is not limited to this, and recursive calculation processing without weight may be used. Therefore, X-ray detection signal I

The function f (I, L) represented by K and the lag image L should be represented by the lag image L (before correction).

K- 1 K K- 1 K

Yes.

Claims

The scope of the claims

[1] A radiation imaging apparatus for obtaining a radiation image based on a radiation detection signal, a radiation irradiating means for irradiating radiation toward a subject, and a radiation detecting means for detecting radiation transmitted through the subject; Based on the non-irradiation signal acquisition means for acquiring a plurality of radiation detection signals detected from the radiation detection means at the time of non-irradiation before irradiation of radiation in the image and the radiation detection signals acquired by the non-irradiation signal acquisition means Among the lag information, the lag image estimation means that obtains the current lag information based on the past lag information and analogizes the lag image, and the radiation detection signal detected from the radiation detection means is acquired at the time of radiation irradiation in imaging. Irradiation signal acquisition means; and radiation image acquisition means for acquiring a radiographic image to be imaged based on the radiation detection signal acquired by the irradiation signal acquisition means! The time delay included in the radiation detection signal is removed from the radiation image acquired by the radiation image acquisition means using the lag image estimated by the lag image analogization means. A radiation imaging apparatus, comprising: lag correction means for performing lag correction related to a time delay due to operation.

[2] In the radiation imaging apparatus according to claim 1, based on the plurality of radiation detection signals acquired by the non-irradiation signal acquisition means! A lag image acquisition means for acquiring a lag image is provided, and the lag image acquisition means and the lag image analogy means are combined to acquire the lag image by the lag image acquisition means. A radiation imaging apparatus characterized by analogizing a lag image by analogy means.

[3] In the radiation imaging apparatus according to claim 1, based on the plurality of radiation detection signals acquired by the non-irradiation signal acquisition means! A lag image acquisition means for acquiring a lag image is provided, and the lag image analogization means is corrected by correcting the lag image acquired by the lag image acquisition means based on the past lag information! Is a radiation imaging apparatus characterized by analogizing a lag image after correction.

[4] A radiation detection signal processing method for performing signal processing for obtaining a radiographic image based on a radiation detection signal detected by irradiating a subject, wherein the signal processing includes a plurality of radiation detection signals. The non-irradiation signal acquisition process acquired at the time of non-irradiation before irradiation in imaging, and the lag information based on those radiation detection signals acquired in the non-irradiation signal acquisition process The lag image analogy process that obtains the current lag information based on the past lag information and analogizes the lag image, the irradiation signal acquisition process that acquires the radiation detection signal at the time of radiation irradiation in imaging, and the Based on the radiation detection signal acquired in the irradiation signal acquisition step, the lag image is acquired from the radiation image acquisition step of acquiring a radiation image to be imaged and the radiation image acquired in the radiation image acquisition step. A lag correction step for performing a lag correction on the time delay by removing the radiation detection signal force from the time delay included in the radiation detection signal by removing the lag using the lag image estimated in the analogy process. A radiation detection signal processing method characterized by comprising:

[5] The radiation detection signal processing method according to claim 4, wherein the past information is a coefficient represented by a signal ratio related to a radiation detection signal acquired at the time of past non-irradiation, and the lag A radiation detection signal processing method characterized in that, in the image analogizing step, the lag information of this time is obtained based on the coefficient to analogize the lag image.

[6] The radiation detection signal processing method according to claim 4, further comprising: a lag image acquisition step for acquiring a lag image based on the radiation detection signals acquired in the non-irradiation signal acquisition step. The signal processing is provided, and the lag image acquisition process and the lag image analogization process are the same process, and the lag image is acquired in the lag image acquisition process. A radiation detection signal processing method characterized by performing analogy.

[7] The radiation detection signal processing method according to claim 4, further comprising: a lag image acquisition step of acquiring a lag image based on the radiation detection signals acquired in the non-irradiation signal acquisition step. The signal processing is provided, and by correcting the lag image acquired in the lag image acquisition step based on the past lag information, the lag image corrected in the lag image acquisition step is analogized. A radiation detection signal processing method.

[8] The radiation detection signal processing method according to claim 6, wherein the past information is a coefficient represented by a signal ratio regarding the past radiation detection signal acquired in the non-irradiation signal acquisition step, A radiation detection signal processing method characterized in that, in a lag image analogizing step, the lag information of the current time is obtained on the basis of the coefficient to estimate the lag image.

[9] In the radiation detection signal processing method according to claim 7, the past information is represented by a signal ratio related to the past radiation detection signal acquired in the non-irradiation signal acquisition step. The correction coefficient is corrected by applying the correction coefficient to the lag image acquired in the lag image acquisition step and correcting the lag image as the current lag information. A radiation detection signal processing method characterized by analogizing.

10. The radiation detection signal processing method according to claim 8, wherein the coefficient is obtained for each pixel, and the current lag information is obtained for each pixel based on the coefficient. Method.

[11] The radiation detection signal processing method according to claim 9, wherein the correction coefficient is obtained for each pixel, and correction is performed by applying each correction coefficient to the lag image for each pixel. Radiation detection signal processing method.