Radiation imaging system

A radiation imaging system comprising a radiation imaging apparatus in which pixels are arranged, a radiation source, a display unit, and a controller is provided. The controller causes, during radiation irradiation, the radiation imaging apparatus to repeat a generation operation of generating one image data by causing the pixels to perform an accumulating operation and a readout operation. When it is instructed to terminate the radiation irradiation, the controller causes the radiation source to stop the radiation irradiation in accordance with completion of the accumulating operation and the readout operation of the last row in the generation operation during which it was instructed to terminate the radiation irradiation, and causes the display unit to display an image based on last image data generated by the generation operation during which it was instructed to terminate the radiation irradiation.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a radiation imaging system.

Description of the Related Art

In medical image diagnosis and nondestructive inspection, a radiation imaging apparatus using an FPD (Flat Panel Detector) made of a semiconductor material is widely used. The radiation imaging apparatus is used for fluoroscopic imaging to capture a moving image. Japanese Patent Laid-Open No. 2008-154893 discloses an X-ray imaging apparatus that has a last image hold function in which, when fluoroscopic imaging is interrupted, the last image in the fluoroscopic imaging is displayed on a monitor.

SUMMARY OF THE INVENTION

When executing fluoroscopic imaging while using an FPD of line exposure sequential readout type, which accumulates signals and reads out signals for each row, and performing continuous radiation irradiation, the accumulation time from the start of signal accumulation to the end of irradiation can change for each row at the time of termination of the radiation irradiation. If the signal accumulation time change for each row, shading may occur in a last image obtained at the time of termination of the radiation irradiation.

Some embodiments of the present invention provide a technique advantageous in, in a radiation imaging system having a last image hold function, improving the quality of an image displayed when fluoroscopic imaging is interrupted.

According to some embodiments, a radiation imaging system comprising a radiation imaging apparatus in which a plurality of pixels are arranged in a matrix to acquire a radiation image, a radiation source configured to continuously irradiate the radiation imaging apparatus with radiation, a display unit, and a controller configured to control an operation of the radiation imaging apparatus, wherein the controller is configured to cause, during radiation irradiation, the radiation imaging apparatus to repeat a generation operation of generating one image data by causing the plurality of pixels to perform an accumulating operation and a readout operation at least row by row from a first row to a last row, and when it is instructed to terminate the radiation irradiation, the controller is configured to cause the radiation source to stop the radiation irradiation in accordance with completion of the accumulating operation and the readout operation of the last row in, among the generation operations, the generation operation during which it was instructed to terminate the radiation irradiation, and cause the display unit to display an image based on last image data generated by, among the generation operations, the generation operation during which it was instructed to terminate the radiation irradiation, is provided.

According to some other embodiments, a radiation imaging system comprising a radiation imaging apparatus in which a plurality of pixels are arranged in a matrix to acquire a radiation image, a radiation source configured to continuously irradiate the radiation imaging apparatus with radiation, a display unit, and a controller configured to control an operation of the radiation imaging apparatus, wherein the controller is configured to cause, during radiation irradiation, the radiation imaging apparatus to repeat a generation operation of generating one image data by causing the plurality of pixels to perform an accumulating operation and a readout operation at least row by row from a first row to a last row, and when it is instructed to terminate the radiation irradiation, the controller is configured to cause the radiation source to stop the radiation irradiation, and cause the display unit to display an image based on last image data generated by, among the generation operations, the generation operation at least one before the generation operation during which it was instructed to terminate the radiation irradiation, is provided.

According to still other embodiments, a radiation imaging system comprising a radiation imaging apparatus in which a plurality of pixels are arranged in a matrix to acquire a radiation image, a radiation source configured to continuously irradiate the radiation imaging apparatus with radiation, a display unit, and a controller configured to control an operation of the radiation imaging apparatus, wherein the controller is configured to cause, during radiation irradiation, the radiation imaging apparatus to repeat a generation operation of generating one image data by causing the plurality of pixels to perform an accumulating operation and a readout operation at least row by row from a first row to a last row, and when it is instructed to terminate the radiation irradiation, the controller is configured to causes the radiation imaging apparatus to operate by selecting one of a first terminating operation in which the radiation source is caused to stop the radiation irradiation in accordance with completion of the accumulating operation and the readout operation of the last row in, among the generation operations, the generation operation during which it was instructed to terminate the radiation irradiation, and the display unit is caused to display an image based on last image data generated by, among the generation operations, the generation operation during which it was instructed to terminate the radiation irradiation, and a second terminating operation in which the radiation source is caused to stop the radiation irradiation, and the display unit is caused to display an image based on last image data generated by, among the generation operations, the generation operation at least one before the generation operation during which it was instructed to terminate the radiation irradiation, is provided.

According to yet other embodiments, a radiation imaging system comprising a radiation imaging apparatus in which a plurality of pixels are arranged in a matrix to acquire a radiation image, a radiation source configured to continuously irradiate the radiation imaging apparatus with radiation, a display unit, and a controller configured to control an operation of the radiation imaging apparatus, wherein the controller is configured to causes, during radiation irradiation, the radiation imaging apparatus to repeat a generation operation of generating one image data by causing the plurality of pixels to perform an accumulating operation and a readout operation at least row by row from a first row in a region of interest, which is set in advance with respect to the plurality of pixels arranged in the matrix, to a last row in the region of interest, and when it is instructed to terminate the radiation irradiation, the controller is configured to cause the radiation source to stop the radiation irradiation in accordance with completion of the accumulating operation and the readout operation of the last row in the region of interest in, among the generation operations, the generation operation during which it was instructed to terminate the radiation irradiation, and cause the display unit to display an image based on last image data generated by, among the generation operations, the generation operation during which it was instructed to terminate the radiation irradiation, is provided.

According to further embodiments, a radiation imaging system comprising a radiation imaging apparatus in which a plurality of pixels are arranged in a matrix to acquire a radiation image, a radiation source configured to continuously irradiate the radiation imaging apparatus with radiation, a display unit, and a controller configured to control an operation of the radiation imaging apparatus, wherein the controller is configured to cause, during radiation irradiation, the radiation imaging apparatus to repeat a generation operation of generating one image data by causing the plurality of pixels to perform an accumulating operation and a readout operation at least row by row from a first row in a region of interest, which is set in advance with respect to the plurality of pixels arranged in the matrix, to a last row in the region of interest, and when it is instructed to terminate the radiation irradiation, the controller is configured to cause the radiation imaging apparatus to operate by selecting one of a first terminating operation in which the radiation source is caused to stop the radiation irradiation in accordance with completion of the accumulating operation and the readout operation of the last row in the region of interest in, among the generation operations, the generation operation during which it was instructed to terminate the radiation irradiation, and the display unit is caused to display an image based on last image data generated by, among the generation operations, the generation operation during which it was instructed to terminate the radiation irradiation, and a second terminating operation in which the radiation source is caused to stop the radiation irradiation, and the display unit is caused to display an image based on last image data generated by, among the generation operations, the generation operation at least one before the generation operation during which it was instructed to terminate the radiation irradiation, is provided.

DESCRIPTION OF THE EMBODIMENTS

Radiation in the present invention can include α-rays, β-rays, γ-rays, and the like which are beams generated by particles (including photons) emitted by radiation decay, as well as beams having the similar or higher energy, for example, X-rays, particle beams, cosmic rays, and the like.

With reference toFIGS.1to8, the configuration and operation of a radiation imaging system according to this embodiment will be described.FIG.1is a block diagram showing a configuration example of a radiation imaging system SYS according to this embodiment. The radiation imaging system SYS according to this embodiment can be used for, for example, medical purposes.

The radiation imaging system SYS includes a radiation imaging apparatus100, a radiation source301, and a control apparatus400including a display unit406. The radiation imaging apparatus100includes a detection unit200in which a plurality of pixels used to acquire a radiation image corresponding to incident radiation are arranged in a matrix. The radiation source301is controlled by a radiation source control apparatus300, and irradiates the radiation imaging apparatus100with radiation. The control apparatus400controls the radiation imaging apparatus100and the radiation source control apparatus300. The control apparatus400communicates control signals with the radiation imaging apparatus100to collect radiation image data from the radiation imaging apparatus100and display a radiation image based on the radiation image data. Further, the control apparatus400includes a radiation imaging application404that can accept an imaging order and register imaging information for generating a control signal including the imaging mode for acquiring a radiation image by the detection unit200.

The control apparatus400is connected to an in-hospital network600formed by, for example, a LAN (Local Area Network). An HIS (Hospital Information System)/RIS (Radiology Information System)601is connected to the in-hospital network600. The control apparatus400and the HIS/RIS601can communicate with each other and exchange, for example, the imaging order of a radiation image, imaging information including patient information, and radiation image data in the hospital.

The radiation imaging apparatus100includes the detection unit200, a controller101, and a power supply unit115. The detection unit detects the radiation entering the detection unit200, and generates image data corresponding to the dose of the detected radiation. The controller101controls respective components arranged in the radiation imaging apparatus100. The controller101includes a driving controller102, an image processing unit106, an offset controller108, a storage unit109, a communication unit112, a timer113, and an irradiation timing controller114. The driving controller102controls the operation of the detection unit200so as to acquire radiation image data corresponding to radiation irradiation and offset image data used to correct the radiation image data. The image processing unit106performs image processing on image data acquired from the detection unit200. The offset controller108controls the timing of updating an offset image. The storage unit109stores acquired image data. The communication unit112controls the communication with the control apparatus400and the communication with the radiation source control apparatus300. For example, the communication unit112receives, from the control apparatus400, a control signal including the imaging mode for acquiring a radiation image by the detection unit200. The timer113acquires an imaging time, an elapse time, and the like. The irradiation timing controller114controls transition to the imaging operation of the detection unit200in accordance with a radiation irradiation signal from the radiation source control apparatus300to the radiation source301. The power supply unit115supplies power to the respective components in the radiation imaging apparatus100.

For example, the controller101may read out a program stored in the storage unit109and control the entire radiation imaging apparatus100based on the readout program. Further, the controller101may include a control signal generation circuit such as an ASIC and control the radiation imaging apparatus100. Furthermore, control of the entire radiation imaging apparatus100may be implemented by both the program and the control signal generation circuit.

The driving controller102controls the detection unit200by switching a plurality of control modes including imaging preparation driving control103, radiation image acquiring control104, and offset image acquiring control105. The imaging preparation driving control103is control for preparing the detection unit200in a state in which a radiation image can be captured. The radiation image acquiring control104is control for driving the detection unit200so as to acquire radiation image data. The offset image acquiring control105is control for driving the detection unit200so as to acquire offset image data. In the imaging preparation driving control103, the driving controller102causes the detection unit200to periodically read out electric charges while applying a voltage similar to that upon imaging, so that dark charges accumulated in the respective pixels arranged in the detection unit200are reset. The signal read out from the pixel at this time is not handled as image data so may not be stored in the storage unit109. In the radiation image acquiring control104, the driving controller102drives the detection unit200as in the imaging preparation driving control103, so that electric charges corresponding to radiation irradiation are accumulated in the pixels arranged in the detection unit200. Then, the electric charges accumulated in the pixels are read out as radiation image data110and stored in the storage unit109. A moving image can be captured by the driving controller102continuously performing the radiation image acquiring control104. In the offset image acquiring control105, the driving controller102drives the detection unit200as in the imaging preparation driving control103, and stores image data, which is read out in a state in which no radiation irradiation is performed, as offset image data111in the storage unit109.

On the radiation image data110acquired from the detection unit200by the radiation image acquiring control104, offset correction is performed using the offset image data111acquired in advance by the offset image acquiring control105. The processing of offset correction may be performed by an offset correction unit107of the image processing unit106. The radiation image data having undergone the offset correction is transferred to the control apparatus400via the communication unit112. Although only the processing of offset correction is described here, the image processing unit106may perform another correction processing such as defective pixel correction or gain correction of correcting the gain variation of the amplifier arranged in the detection unit200. Alternatively, the correction processing as described above may not be performed in the radiation imaging apparatus100. For example, the acquired radiation image data110and offset image data111may be transferred to the control apparatus400without undergoing the correction processing or the like, and the control apparatus400may perform the correction processing as described above. As the offset image data used for offset correction, for example, image data generated by acquiring a plurality of offset image data and performing noise component reduction processing by averaging or the like may be used.

The radiation source control apparatus300includes an operation UI302used to operate the radiation source control apparatus300. The operation UI302can include a keyboard, a mouse, an exposure switch, and the like. A user may set a radiation irradiation condition or perform radiation irradiation using the operation UI302. The radiation source control apparatus300and the radiation imaging apparatus100can exchange information using a dedicated signal line. The radiation source control apparatus300and the radiation imaging apparatus100may exchange, for example, synchronization signals such as a notification of the start or end of radiation irradiation and a notification of the radiation irradiation enable timing. With this, the radiation imaging apparatus100and the radiation source301controlled by the radiation source control apparatus300are configured to be capable of capturing a radiation image without intervention of the control apparatus400.

The control apparatus400includes an imaging controller402, an irradiation controller403, a communication unit401, the radiation imaging application404, the display unit406, an operation UI407, and a power supply unit405, and controls the respective components of the radiation imaging system SYS. The imaging controller402controls, in accordance with the user setting received via the radiation imaging application404, the radiation imaging apparatus100to control the timing of acquiring image data, set the imaging conditions including the imaging mode for acquiring a radiation image by the detection unit200, and the like. The irradiation controller403controls, in accordance with the user setting received via the radiation imaging application404, the irradiation condition of radiation applied form the radiation source301by controlling the radiation source control apparatus300. The communication unit401controls the communication with the radiation imaging apparatus100, the radiation source control apparatus300, and the in-hospital network600. The radiation imaging application404accepts the imaging order and registers the imaging information. The display unit406displays a radiation image based on radiation image data acquired by the radiation imaging apparatus100or the information of an imaging condition such as the imaging mode for performing imaging. The operation UI407can be a mouse or keyboard used to operate the radiation imaging application404. The power supply unit405supplies power to the respective components in the control apparatus400.

Here, the communication between the control apparatus400and the radiation imaging apparatus100and the communication between the control apparatus400and the radiation source control apparatus300may be cable connection communication using a standard such as RS232C, USB, or Ethernet. Further, the communication between the control apparatus400and the radiation imaging apparatus100and the communication between the control apparatus400and the radiation source control apparatus300may be communication using a dedicated signal line, or may be wireless communication. Furthermore, the communication between the control apparatus400and the radiation imaging apparatus100and the communication between the control apparatus400and the radiation source control apparatus300may be a combination of wired communication and wireless communication.

In the communication between the control apparatus400and the radiation imaging apparatus100, for example, image data and a signal indicating the apparatus status of the radiation imaging apparatus100are transmitted from the radiation imaging apparatus100to the control apparatus400. Further, for example, a control signal including a signal indicating the condition setting such as the imaging mode for acquiring image data is transmitted from the control apparatus400to the radiation imaging apparatus100. In the communication between the control apparatus400and the radiation source control apparatus300, for example, a signal indicating the setting of a radiation irradiation condition and the like are transmitted from the control apparatus400to the radiation source control apparatus300. Further, for example, a signal indicating the apparatus status of the radiation source control apparatus300and a signal indicating the actual irradiation information at the time of radiation irradiation are transmitted from the radiation source control apparatus300to the control apparatus400.

FIG.2is a block diagram showing an arrangement example of the detection unit200of the radiation imaging apparatus100. The detection unit200includes a sensor array204including a plurality of pixels207arrayed in a two-dimensional array so as to form a plurality of rows and a plurality of columns to acquire a radiation image corresponding to incident radiation. The pixel207arranged in the sensor array204includes, for example, a switch element208such as a TFT (Thin Film Transistor) and a photoelectric conversion element209, and a scintillator (not shown) can be arranged on the pixel207(photoelectric conversion element209). The scintillator can be integrally formed in the sensor array204. If the pixel207includes the scintillator and the photoelectric conversion element209, the radiation entering the detection unit200is converted into visible light by the scintillator, the converted visible light enters the photoelectric conversion element209of the pixel207, and electric charges corresponding to the visible light are generated in the photoelectric conversion element209. In this manner, a so-called indirect conversion type conversion element which converts the incident radiation into electric charges by the scintillator and the photoelectric conversion element209may be used as the pixel207. Alternatively, for example, a so-called direct conversion type conversion element which is not provided with the scintillator and directly converts the incident radiation into electric charges may be used as the pixel207. By switching the switch element208between the ON (conductive) state and the OFF (non-conductive) state, accumulation of the electric charges generated by the photoelectric conversion element209and readout of the electric charges are performed, and radiation image data can be acquired.

In the pixel207arranged in the sensor array204of the detection unit200, the switch element208is set in the ON state when a voltage for setting the switch element208in the ON state is applied for each row from a drive circuit201via a common driving line211. When the switch element208is set in the ON state, a signal corresponding to the electric charges accumulated in the pixel207is transferred to a sample hold circuit202via a signal line210connected to each pixel207. After that, the signals output from the pixels207and held in the sample hold circuit202are sequentially read out via a multiplexer203, amplified by an amplifier205, and converted into digital value image data by an A/D converter206. When a voltage for setting the switch element208in the OFF state is applied from the drive circuit201via the driving line211, the pixel207in which readout of the electric charges is completed returns to a state of accumulating electric charges. In this manner, the drive circuit201sequentially scans the pixels207arranged on the sensor array204for each line, and signals finally output from all the pixels207are converted into a digital value. With this, the image data for generating a radiation image can be read out. Control for the above-described driving operation, readout operation, or the like of the detection unit200is performed by the driving controller102of the controller101. The image data converted into the digital value may be, for example, temporarily stored in the storage unit109shown inFIG.1.

Next, an operation of the radiation imaging system SYS in this embodiment will be described.FIG.3is a timing chart showing an operation example of the radiation imaging system SYS in this embodiment. In this embodiment, in accordance with a user operation, the radiation source301continuously irradiate the radiation imaging apparatus100with radiation to capture a moving image (continuous fluoroscopy). When fluoroscopic imaging is interrupted or terminated, a last image hold operation of displaying the last image in the fluoroscopic imaging on the display unit406is performed.FIG.3shows a sequence of operations of the radiation imaging apparatus100and the radiation source301(radiation source control apparatus300) in the continuous fluoroscopy.

“Operation UI302input” indicates a signal for the user to request capturing of a radiation image. InFIG.3, for example, when the user presses an exposure switch for starting continuous fluoroscopy, “operation UI302input” changes to high level. “Detection unit200operation” indicates the operation state of the sensor array204of the detection unit200. “Readout processing” indicates an operation of transferring image data from the detection unit200to the controller101in the radiation imaging apparatus100. “Storage unit109storage operation” indicates an operation of storing, in the storage unit109, the image data transferred to the controller101. “Irradiation instruction” indicates a signal from the irradiation timing controller114instructing the radiation source control apparatus300to perform radiation irradiation. “Radiation source301irradiation instruction” indicates a signal from the radiation source control apparatus300instructing the radiation source301to perform radiation irradiation in accordance with “irradiation instruction”. InFIG.3, while “radiation source301irradiation instruction” is at high level, the radiation source301performs radiation irradiation. “Radiation imaging apparatus100output operation” indicates an operation of transferring image data from the radiation imaging apparatus100to the control apparatus400.

Next, operations of the radiation imaging apparatus100and the radiation source301(radiation source control apparatus300) in continuous fluoroscopy will be described. Before it is instructed by the user, via the operation UI302, to start radiation irradiation, the control apparatus400causes the radiation imaging apparatus100to start a generation operation for generating image data. The generation operation is an operation of generating one image data by causing the detection unit200of the radiation imaging apparatus100to cause the plurality of pixels207to perform an accumulating operation500and a readout operation510at least row by row from the first row to the last row. By repeating the generation operation, a moving image can be captured.

As indicated by “detection unit200operation” and “readout processing”, the accumulating operation500and the readout operation510are repeated prior to the start of radiation irradiation. This operation can be also referred to as reset driving for suppressing the influence of dark charges generated in the pixel207or the like. The signal read out from the pixel207at this time is not handled as image data so may not be stored in the storage unit109.

Then, when it is instructed by the user to start radiation irradiation by pressing the exposure switch of the operation UI302or the like, the radiation imaging system SYS starts continuous fluoroscopy. When the readout operation510of the last row (shown as the Nth row inFIG.3) of the plurality of pixels207arranged in the sensor array204is completed, the irradiation timing controller114transmits, to the radiation source control apparatus300, a signal instructing to start radiation irradiation. The radiation source control apparatus300, which has received the signal instructing to start radiation irradiation, instructs the radiation source301to perform radiation irradiation, and the radiation source301starts radiation irradiation. That is, when it is instructed to start radiation irradiation, the radiation source301is caused to start radiation irradiation in accordance with the completion of the readout operation510of the last row in, among the generation operations, the generation operation during which it was instructed to start irradiation radiation.

During radiation irradiation, the radiation imaging apparatus100repeats the above-described generation operation. By the generation operation, one image data is generated in one frame. The image data read out by the readout operation510is transferred to the controller101and stored as the radiation image data110in the storage unit109. The image data stored as the radiation image data110in the storage unit109undergoes offset correction processing by the offset correction unit107using the offset image data111stored in the storage unit109in advance, and the processed image data is transferred to the control apparatus400via the communication unit112. An image based on the image data transferred to the control apparatus400is displayed on the display unit406. By repeating these operations, continuous fluoroscopy is executed.

As shown inFIG.3, when generating the image data for the first frame, the radiation irradiation time in the accumulating operation500changes for each row. Therefore, shading can occur in the image generated from the image data for the first frame. On the other hand, after the second frame, the radiation irradiation time in the accumulating operation500does not change for each row, so that shading can be suppressed.

Next, a case will be described in which, for example, the user returns the exposure switch of the operation UI302in the Nth frame to interrupt or terminate the continuous fluoroscopy. When it is instructed to terminate the radiation irradiation, the irradiation timing controller114maintains the “irradiation instruction” signal at high level until the timing at which the readout operation510of the last row (Nth row) of the plurality of pixels207arranged in the sensor array204is completed in the Nth frame where the accumulating operation500has been already started. When the readout operations of all the rows in the Nth frame are completed, the “irradiation instruction” signal is changed to low level. In accordance with the change of the “irradiation instruction” signal to low level, the radiation source control apparatus300changes the “radiation source301irradiation instruction” signal output to the radiation source301to low level. Thus, the radiation source301stops the radiation irradiation in accordance with the completion of the accumulating operation500and the readout operation510of the last row in, among the generation operations, the generation operation in the Nth frame during which it was instructed to terminate the radiation irradiation.

Since the radiation irradiation is performed until the accumulating operation500and the readout operation510of the last row in the generation operation in the Nth frame are completed, the image data for the Nth frame during which it was instructed to terminate the radiation irradiation is data of the time at which the radiation irradiation times in the accumulating operations500are equal to each other for the respective rows. Further, the image data for the Nth frame can be data of the time at which the radiation irradiation times in the accumulating operations500are equal to each other for the respective rows. The control apparatus400causes the display unit406to display an image based on the last image data generated by the generation operation in the Nth frame during which it was instructed to terminate the radiation irradiation. Thus, it is possible to provide the radiation imaging system SYS that can obtain, even when the continuous fluoroscopy is terminated or interrupted, a clear image in which each of the plurality of pixels207arranged in the sensor array204is irradiated with radiation.

The operation shown inFIG.3shows that the accumulating operation500and the readout operation510are performed row by row from the first row to the Nth row (last row), but the present invention is not limited to this. For example, the accumulating operation500and the readout operation510may be performed for multiple rows such as for two rows or for three rows. Further, the radiation source301stops the radiation irradiation in accordance with the completion of the accumulating operation500and the readout operation510of the last row in the generation operation in the Nth frame, but the present invention is not limited to this. The radiation source301may stop the radiation irradiation in accordance with the completion of the accumulating operation500of the last row in the generation operation in the Nth frame. Even in this case, the radiation irradiation times in the accumulating operations500can be equal to each other for the respective rows.

After it is instructed to terminate the radiation irradiation, the control apparatus400causes the radiation imaging apparatus100to stop the generation operation in which the accumulating operation500and the readout operation510are performed. In this case, the control apparatus400may not cause the radiation imaging apparatus100to output, to the control apparatus400, the image data generated by the generation operation performed after the generation operation in which the last image data was generated. Alternatively, in this case, the image data generated by the generation operation performed after the generation operation in which the last image data was generated may not be transferred from the detection unit200to the controller101. Alternatively, for example, the image data generated by the generation operation performed after the generation operation in which the last image data was generated may not be stored in the storage unit109. Since the image data generated by the generation operation performed after the generation operation in which the last image data was generated is not transferred to the storage unit109or the communication unit112, it is not output from the radiation imaging apparatus100.

For example, the image displayed on the display unit406after the radiation irradiation is terminated is not limited to an image based on the last image data alone. The control apparatus400may cause the display unit406to display an image based on a plurality of image data including the last image data generated in the Nth frame and the image data generated by the generation operation one before (in the (N−1)th frame) the generation operation in which the last image data was generated. A composite image based on the data generated by adding or averaging the plurality of image data can be displayed on the display unit406. The incident radiation dose in fluoroscopy imaging is often smaller than in still image capturing. By generating an image based on a plurality of image data, noise components in the image displayed on the display unit406are suppressed, and the image quality can be improved.

FIG.4is a timing chart showing a modification of the operations of the radiation imaging apparatus100and the radiation source301(radiation source control apparatus300) in continuous fluoroscopy shown inFIG.3. As in the operations shown inFIG.3,FIG.4shows a case in which it is instructed to terminate the radiation irradiation in the Nth frame from the start of continuous fluoroscopy.

In the operations shown inFIG.4, when an instruction to terminate the radiation irradiation is input, the irradiation timing controller114changes the “irradiation instruction” signal to low level. In accordance with the change of the “irradiation instruction” signal to low level, the radiation source control apparatus300changes the “radiation source301irradiation instruction” signal output to the radiation source301to low level. Thus, the radiation source301stops the radiation irradiation. Therefore, the image data for the Nth frame is data in which the radiation irradiation time in the accumulating operation500changes each row. Accordingly, when the display unit406displays an image based on the image data for the Nth frame, shading may occur in the displayed image.

To prevent this, the control apparatus400causes the display unit406to display an image based on the image data (last image data) generated by the generation operation in the (N−1)th frame one before the generation operation in the Nth frame during which it was instructed to terminate the radiation irradiation. That is, the image displayed on the display unit406is an image based on the image data of the time at which the radiation irradiation times in the accumulating operations500are equal to each other for the respective rows. Thus, also in the operation shown inFIG.4, as in the operation shown inFIG.3, it is possible to provide the radiation imaging system SYS that can obtain a clear image in which each of the plurality of pixels207arranged in the sensor array204is irradiated with radiation.

Also in the operation shown inFIG.4, the image data generated by the generation operations (in the Nth and subsequent frames) performed after the generation operation in which the last image data was generated may not be transferred from the radiation imaging apparatus100to the control apparatus400. Alternatively, the image data generated by the generation operations in the Nth and subsequent frames may not be transferred from the detection unit200to the controller101, or may not be stored in the storage unit109. The image to be displayed on the display unit406may be generated from the last image data and one or more image data generated by the generation operations in the frames before the frame in which the last image data was generated. Alternatively, the image to be displayed on the display unit406may be generated using the last image data and the image data generated by the generation operation in the frame two frames before the frame in which the last image data was generated. That is, the image to be displayed on the display unit406may be generated using the last image data and the image data generated by the generation operation in the frame at least one frame before the frame in which the last image data was generated.

When the exposure switch is released, the radiation imaging apparatus100may determine whether to extend the radiation irradiation by continuing the “irradiation instruction” signal until the timing at which the readout operation510of the last row (Nth row) in the Nth frame is completed as shown inFIG.3, or to immediately stop the radiation irradiation as shown inFIG.4, and switch the terminating operation of terminating (interrupting) the continuous fluoroscopy. An example of the terminating operation determination procedure in the continuous fluoroscopy in this case will be described with reference toFIG.5.

First, for example, when the user releases the exposure switch of the operation UI302in the Nth frame, the controller101of the radiation imaging apparatus100detects (recognizes) turn-off of the exposure switch (step S101). At this time, the controller101uses, for example, the timer113to obtain a time Toff from the completion of the readout operation510of the last row (Nth row) in the immediately preceding (N−1)th frame to the detection of the turn-off of the exposure switch. Then, the controller101obtains a time ΔT from the turn-off of the exposure switch to the completion of the readout operation510of the last row in the Nth frame. For example, by using a time Tcyc of one cycle of a frame for the continuous fluoroscopy imaging mode currently in operation, the time ΔT until the completion of the readout operation510of the last row in the Nth frame can be calculated as ΔT=Tcyc−Toff (step S102).

Then, the controller101determines whether the time ΔT is smaller than a predetermined threshold value Tth (step S103). Here, if the time ΔT is smaller than the threshold value Tth (YES in step S103), the controller101operates so as to maintain the “irradiation instruction” signal at high level (irradiation) until the completion of the readout operation510of the last row (Nth row) in the Nth frame as shown inFIG.3(step S104). Further, the control apparatus400causes the display unit406to display an image based on the last image data generated by the generation operation in the Nth frame during which it was instructed to terminate the radiation irradiation (step S105).

On the other hand, if the time ΔT is equal to or larger than the threshold value Tth (NO in step S103), if the “irradiation instruction” signal is maintained at high level until the completion of the readout operation510of the last row (Nth row) in the Nth frame, the radiation irradiation is performed for a predetermined period or more even though the exposure switch has been released. Particularly, when the frame rate for the continuous fluoroscopy imaging mode in operation is low, this leads to a long radiation irradiation time after the turn-off of the exposure switch. In such a case, as shown inFIG.4, in accordance with the user instruction to terminate the radiation irradiation, the “irradiation instruction” signal is immediately changed to low level to stop the radiation irradiation (step S106). Further, the control apparatus400causes the display unit406to display an image based on the image data (last image data) generated by the generation operation in the (N−1)th frame one before the generation operation in the Nth frame during which it was instructed to terminate the radiation irradiation (step S107). In this manner, in accordance with the timing of the release of the exposure switch, it is possible to select the appropriate continuous fluoroscopy terminating operation without excessive continuation of the radiation irradiation after the release of the exposure switch to terminate the radiation irradiation.

The method of selecting the continuous fluoroscopy terminating operation is not limited to the method described above. For example, the terminating operation may be uniquely determined in accordance with the frame rate of the generation operation for the used continuous fluoroscopy imaging mode. For example, if the frame rate is equal to or higher than a predetermined frame rate, the controller101may control so as to continue the “irradiation instruction” signal until the completion of the readout operation510of the last row in the Nth frame as shown inFIG.3. If the frame rate is lower than the predetermined frame rate, since the period from the release of the exposure switch to the stop of the radiation irradiation may become long, the controller101may control so as to immediately stop the “irradiation instruction” signal as shown inFIG.4. By controlling as described above, in accordance with the frame rate for the used continuous fluoroscopy imaging mode, it is possible to select the appropriate continuous fluoroscopy terminating operation without excessive continuation of the radiation irradiation after the release of the exposure switch. Here, the frame rate is defined by the generation operation (the accumulating operation500and the readout operation510) to be performed on each row. For example, the frame rate can be the number of the generation operations to be performed on one row in a predetermined time.

In the radiation imaging apparatus100, imaging may be performed using not all the rows in the sensor array204. Here, a continuous fluoroscopy terminating operation which is preformed when a predetermined region of interest (ROI)702in the sensor array204is designated as the region to be used for imaging will be described. In this embodiment, in accordance with the timing at which the user instructs, by releasing the exposure switch or the like, to terminate the radiation irradiation and the designated ROI702, a period to maintain the “irradiation instruction” signal at high level upon terminating the continuous fluoroscopy is changed.

First, with reference toFIG.6, an example of the image data readout direction in the sensor array204and the ROI702will be described. As has been described above, the controller101of the radiation imaging apparatus100controls the plurality of pixels207arranged in the sensor array204so as to perform the readout operation on a row basis. Here, as shown inFIG.6, the image data readout operation is performed from the upper portion (first row) to the lower portion (Nth row) of the sensor array204in the direction indicated by an arrow703.

Here, for example, the ROI702may indicate the effective region of an image defined in advance for each imaging mode, or may be individually defined as a region of interest set for each imaging procedure or each protocol. Alternatively, for the ROI702, the radiation imaging apparatus100may obtain the stop information of a collimator connected to the radiation source301, and the radiation irradiation range obtained from the stop information may be defined as the ROI702. Here, a case in which the ROI702is set in the center of the sensor array204as shown inFIG.6will be taken as an example and described.

As shown inFIG.6, a readout period Trd of reading out image data from the respective pixels207in the sensor array204for each row includes a readout period Tout_u for image data from the first row to the (Roi1−1)th row outside the region of interest, a readout period Troi for image data in the ROI702(from the (Roi1)th row to the (RoiM)th row), and a readout period Tout_1 for image data from the (RoiM+1)th row to the Nth row outside the region of interest. An example of the operation timing control during continuous fluoroscopy performed when the ROI702is set as shown inFIG.6will be described with reference toFIG.7. The operation upon starting continuous fluoroscopy may be similar to that shown inFIG.3, so that the description thereof will be omitted here.

A case will be described in which continuous fluoroscopy is interrupted or terminated by the user returning the exposure switch of the operation UT302in the Nth frame. When it is instructed to terminate the radiation irradiation, the irradiation timing controller114maintains the “irradiation instruction” signal at high level until the timing at which the readout operation510of the last row ((RoiM)th row) in the ROI702is completed in the Nth frame in which the accumulating operation500has been already started. When the readout operations510of all the rows in the ROI702in the Nth frame are completed, the irradiation timing controller114changes the “irradiation instruction” signal to low level to stop the radiation irradiation.

Thus, since the radiation irradiation is performed until the accumulating operation and the readout operation of the last row in the ROI702in the generation operation in the Nth frame are completed, the image data for the Nth frame during which it was instructed to terminate the radiation irradiation is data of the time at which the radiation irradiation times are equal to each other for the respective rows at least in the ROI702. The control apparatus400causes the display unit406to display an image based on the last image data generated by the generation operation in the Nth frame during which it was instructed to terminate the radiation irradiation. Thus, it is possible to provide the radiation imaging system SYS that can obtain, even when the continuous fluoroscopy is terminated or interrupted, a clear image in which each pixel207at least in the ROI702is irradiated with radiation.

Further, a case will be described in which the exposure switch is released between the (RoiM+1)th row and the Nth row (the period Tout_1 shown inFIG.6) during the readout operation in the (N−1)th frame shown inFIG.7. In this case, since the readout operation510of the last row ((RoiM)th row) in the ROI702in the (N−1)th frame is already completed, the irradiation timing controller114maintains the “irradiation instruction” signal at high level until the readout operation510of the last row ((RoiM)th row) in the ROI702in the next Nth frame is completed. When the readout operations510of all the rows in the ROI702in the Nth frame are completed, the irradiation timing controller114changes the “irradiation instruction” signal to low level to stop the radiation irradiation. Thus, the irradiation instruction may be continued until the timing of the completion of the readout operation510of the last row ((RoiM)th row) in the ROI702in the next frame after the exposure switch is released.

The operation shown inFIG.7shows that the accumulating operation500and the readout operation510are performed row by row from the first row to the Nth row (last row), but the present invention is not limited to this. For example, the accumulating operation500and the readout operation510may be performed for multiple rows such as for two rows or for three rows. Further, the radiation source301stops the radiation irradiation in accordance with the completion of the accumulating operation500and the readout operation510of the last row ((RoiM)th row) in the ROI702in the generation operation in the Nth frame, but the present invention is not limited to this. The radiation source301may stop the radiation irradiation in accordance with the completion of the accumulating operation500of the last row ((RoiM)th row) in the ROI702in the generation operation in the Nth frame. Even in this case, the radiation irradiation times in the accumulating operations500can be equal to each other for the respective rows in the ROI702.

In the region from the (RoiM+1)th row to the Nth row outside the ROI702, the radiation irradiation time in the accumulating operation500changes for each row. Therefore, in the image generated in the Nth frame, shading can occur in the region outside the ROI702. However, since this is not the image data of the region used for observation, diagnosis, or the like, a problem is unlikely to occur in observation, diagnosis, or the like using the obtained image.

After it is instructed to terminate the radiation irradiation, the control apparatus400causes the radiation imaging apparatus100to stop the generation operation in which the accumulating operation500and the readout operation510are performed. In this case, the control apparatus400may not cause the radiation imaging apparatus100to output, to the control apparatus400, the image data generated by the generation operation performed after the generation operation in which the last image data was generated. Alternatively, in this case, the image data generated by the generation operation performed after the generation operation in which the last image data was generated may not be transferred from the detection unit200to the controller101. Alternatively, for example, the image data generated by the generation operation performed after the generation operation in which the last image data was generated may not be stored in the storage unit109. Since the image data generated by the generation operation performed after the generation operation in which the last image data was generated is not transferred to the storage unit109or the communication unit112, it is not output from the radiation imaging apparatus100. These operations may be similar to the operations described above with reference toFIG.3.

For example, the image displayed on the display unit406after the radiation irradiation is terminated is not limited to an image based on the last image data alone. An image based on a plurality of image data may be displayed. This operation may be similar to the operation described above with reference toFIG.3.

Also in the continuous fluoroscopy for which the predetermined region of interest (ROI)702in the sensor array204is designated as the region used for imaging, it is possible to perform the continuous fluoroscopy terminating operation as shown inFIG.4described above. The operation in this case is similar to the operation shown inFIG.4. When an instruction to terminate the radiation irradiation is input, the irradiation timing controller114changes the “irradiation instruction” signal to low level to stop the radiation irradiation.

When the exposure switch is released, the radiation imaging apparatus100may determine whether to extend the radiation irradiation by maintaining the “irradiation instruction” signal until the completion of the readout operation510of the last row ((RoiM)th row) in the ROI702in the Nth frame as shown inFIG.7, or to immediately stop the radiation irradiation as shown inFIG.4, and switch the terminating operation. An example of the terminating operation determination procedure in the continuous fluoroscopy in this case will be described with reference toFIG.8.

First, for example, when the user releases the exposure switch of the operation UI302in a period from the completion of the readout operation510of the last row ((RoiM)th row) in the ROI702(the start of the readout operation510of the (RoiM+1)th row) in the (N−1)th frame to the readout operation510of the last row ((RoiM)th row) in the ROI702in the Nth frame, the controller101of the radiation imaging apparatus detects turn-off of the exposure switch (step S201). At this time, the controller101uses, for example, the timer113to obtain the time Toff from the completion of the readout operation510of the last row ((RoiM)th row) in the ROI702in the immediately preceding (N−1)th frame to the detection of the turn-off of the exposure switch. Then, the controller101obtains the time ΔT from the turn-off of the exposure switch to the completion of the readout operation510of the last row ((RoiM)th row) in the ROI702in the Nth frame. For example, by using the time Tcyc of one cycle of a frame for the continuous fluoroscopy imaging mode currently in operation, the time ΔT from the turn-off of the exposure switch to the completion of the readout operation510of the last row ((RoiM)th row) in the ROI702in the Nth frame can be calculated as ΔT=Tcyc−Toff (step S202).

Then, the controller101determines whether the time ΔT is smaller than the predetermined threshold value Tth (step S203). Here, if the time ΔT is smaller than the threshold value Tth (YES in step S203), the controller101operates so as to maintain the “irradiation instruction” signal at high level (irradiation) until the completion of the readout operation510of the last row ((RoiM)th row) in the ROI702in the Nth frame as shown inFIG.7(step S204). Further, the control apparatus400causes the display unit406to display an image based on the last image data generated by the generation operation in the Nth frame (step S205).

On the other hand, if the time ΔT is equal to or larger than the threshold value Tth (NO in step S203), as shown inFIG.4, the irradiation timing controller114immediately changes the “irradiation instruction” signal to low level to stop the radiation irradiation (step S206). Further, the control apparatus400causes the display unit406to display an image based on the image data (last image data) generated by the generation operation in the (N−1)th frame one before the generation operation in the Nth frame during which it was instructed to terminate the radiation irradiation (step S207). In this manner, in accordance with the timing of the release of the exposure switch, it is possible to select the appropriate continuous fluoroscopy terminating operation without excessive continuation of the radiation irradiation after the release of the exposure switch to terminate the radiation irradiation.

The method of selecting the terminating operation during continuous fluoroscopy is not limited to the method described above. For example, the terminating operation may be uniquely determined in accordance with the frame rate of the generation operation for the used continuous fluoroscopy imaging mode. For example, if the frame rate is equal to or higher than a predetermined frame rate, the controller101may control so as to continue the “irradiation instruction” signal until the completion of the readout operation510of the last row ((RoiM)th row) in the ROI702in the Nth frame as shown inFIG.7. If the frame rate is lower than the predetermined frame rate, since the period from the release of the exposure switch to the stop of the radiation irradiation may become long, the controller101may control so as to immediately stop the “irradiation instruction” signal as shown inFIG.4. By controlling as described above, in accordance with the frame rate for the used continuous fluoroscopy imaging mode, it is possible to select the continuous fluoroscopy terminating operation with which occurrence of shading in the image at least in the ROI702is suppressed without excessive continuation of the radiation irradiation after the release of the exposure switch.

In this embodiment, it has been described that the ROI702is set in the center of the sensor array204as shown inFIG.6. However, the preset invention is not limited to this, and similar control can be applied to the ROI702set in an arbitrary location.

As has been described above, in the radiation imaging system SYS having the last image hold function, an image to be displayed on the display unit406when fluoroscopic imaging is interrupted is generated from image data in which the radiation irradiation times in the accumulating operations500are equal to each other for the respective rows. Thus, shading in the image displayed when fluoroscopic imaging is interrupted is suppressed, so that the image quality improves and the more user-friendly radiation imaging system SYS can be implemented.

This application claims the benefit of Japanese Patent Application No. 2021-021262, filed Feb. 12, 2021, and Japanese Patent Application No. 2021-198700, filed Dec. 7, 2021 which are hereby incorporated by reference herein in their entirety.