X-ray system and method with digital image acquisition

The contents disclosed in this document relate to an X-ray imaging system, and more specifically to an X-ray imaging system using a digital detector.

The advent of digital X-ray detectors has improved workflows and brought higher image quality for medical imaging. However, previous radiation imaging systems used conventional film-based X-ray imaging and / or computer-based radiography. In order to obtain images from these systems, the imaging medium must be transported and processed after each irradiation, resulting in a time delay in obtaining the desired image. Digital radiography provides an alternative method that allows the acquisition of image data and reconstructed images on the fly for quick observation and diagnosis. However, the cost of replacing a previous conventional radiation imaging system with a digital radiation imaging system can be burdensome for hospitals or tertiary care centers. Therefore, there is a need to retroactively incorporate digital radiography into previous radiation imaging systems in a cost-effective manner, including reducing the number of system components as much as possible.

According to one embodiment, an X-ray imaging system is provided, which is coupled to an X-ray source and directs the emission of X-rays for imaging irradiation. Communication with the configured radiation source control device, a digital X-ray detector configured to acquire X-ray image data without communication from the radiation source control device, and the digital X-ray detector. Includes a portable detector controller that is configured to.

According to another embodiment, an X-ray imaging method is provided, which comprises commanding a detector preparation signal from a portable detector controller to a digital X-ray detector. The method also comprises the X-ray radiation source so that the X-ray source control device performs X-ray irradiation even if the source control device coupled to the X-ray radiation source does not communicate with the X-ray detector. Has a stage to direct to. The method further includes the step of acquiring the X-ray image data from the detector by the portable detector control device.

According to yet another embodiment, an X-ray imaging system is provided, which acquires X-ray image data for processing and image preview without communication from a source controller. Includes a digital X-ray detector that is configured to send X-ray image data to a portable detector controller. The radiation source control device is configured to command the emission of X-rays from an X-ray radiation source for imaging irradiation.

These and other features, aspects and advantages of the present invention will be better understood by reading the following detailed description with reference to the accompanying drawings. In the drawings, similar reference numerals represent similar parts throughout the drawings.

<figref num="1">FIG. 1 is a perspective view of an exemplary fixed X-ray system equipped according to various aspects of the invention.</figref><figref num="2">FIG. 2 is a perspective view of an exemplary mobile X-ray system equipped according to various aspects of the invention.</figref><figref num="3">FIG. 3 is a schematic configuration diagram of the X-ray system of FIGS. 1 and 2.</figref><figref num="4">FIG. 4 is a schematic diagram showing functional components in the detectors of the systems of FIGS. 1 to 3.</figref><figref num="5">FIG. 5 is a schematic representation of a bidirectional interaction between a detector and a portable detector controller according to various aspects of the invention.</figref><figref num="6">FIG. 6 is a flow diagram of a method for a workflow between a detector and a portable detector controller according to various aspects of the invention.</figref><figref num="7">FIG. 7 is a diagram showing the sampling of X-ray image data from two imaging frames according to various aspects of the invention.</figref><figref num="8">FIG. 8 is a diagram showing the sampling and combination of X-ray image data from three imaging frames according to various aspects of the present invention.</figref><figref num="9">FIG. 9 is a diagram showing the sampling and combination of X-ray image data from one imaging frame according to various aspects of the present invention.</figref><figref num="10">FIG. 10 is a flow diagram of a method for creating X-ray image data that can be reconstructed into a user-observable image by sampling and combining X-ray image data according to various aspects of the present invention. is there.</figref><figref num="11">FIG. 11 is a schematic representation of a workflow during an acquisition sequence in which both image data and offset data are acquired to create a user-observable image according to various aspects of the invention.</figref><figref num="12">FIG. 12 is a diagram showing an acquisition sequence in which different voltages are applied to reduce transistor leakage while sampling image data, according to various aspects of the invention.</figref><figref num="13">FIG. 13 is a flow diagram of a method for sampling data from a detector before and after X-ray irradiation while applying different voltages to reduce transistor leakage according to various aspects of the invention.</figref>

Generally, to explain FIG. 1, the X-ray system is generally represented by the reference digit 10. In the illustrated embodiment, the X-ray system 10 is a digital X-ray system when adapted. The X-ray system 10 is designed to acquire image data and process the image data for display in accordance with the techniques of the present invention. However, throughout the following description, basic background information is provided for digital X-ray systems used in medical diagnostic applications, but various aspects of the technique of the invention have different settings (eg, projected X-rays, etc.). Note that it can be applied to digital detectors (including X-ray detectors) used for computed tomography imaging, tomosynthesis imaging, etc. and for different purposes (eg, parcel, luggage, vehicle and parts inspection, etc.). I want to.

In the embodiment illustrated in FIG. 1, the X-ray system 10 includes an imaging system 12. The imaging system 12 may be a conventional analog imaging system modified for digital image data acquisition and processing as described below. In one embodiment, the imaging system 12 can be a stationary system located in a fixed X-ray imaging chamber, as outlined in FIG. 1 and described below. However, it will be appreciated that the techniques disclosed herein can also be used for other imaging systems, including mobile X-ray units and systems in other embodiments. The imaging system 12 includes an overhead X-ray tube support arm 14 for positioning a radiation source 16 such as an X-ray tube and a collimator 18 with respect to the patient 20 and the detector 22. The detector 22 includes a digital X-ray detector. In some embodiments, the detector 22 can be selected from a plurality of detectors 22 (represented by the detector 24) from the dock 26 (eg, charging dock). Each detector 22 of the plurality of detectors 22 can be labeled and designated for a particular type of imaging (eg, fluoroscopy and X-ray imaging). The detector 22 is configured to acquire X-ray image data without communication from the control device of the X-ray radiation source 16. In other words, the detector 22 does not receive a timing signal from the control device of the source 16 regarding X-ray irradiation. As a result, in preparation for acquiring the X-ray image data, the detector 22 is configured to continuously sample the data before and after the X-ray irradiation. The detector 22 is also configured to combine a plurality of frames containing imaging data to generate an X-ray image. Further, the detector 22 is configured to process the X-ray image data at least partially.

In one embodiment, the imaging system 12 can be used in cooperation with one or both of the patient table 28 and the wall stand 30 to facilitate image acquisition. More specifically, the table 28 and the wall stand 30 can be configured to receive the detector 22. For example, the detector 22 can be placed on the upper, lower or intermediate surface of the table 28, and the patient 20 (more specifically, the anatomical region of interest of the patient 20) can be detected. It can be positioned on the table 28 between the vessel 22 and the radiation source 16. Also, the wall stand 30 can include a receptive structure 32 suitable for receiving the detector 22, and the patient 20 is positioned adjacent to the wall stand 30 so that image data can be acquired by the detector 22. can do. The receiving structure 32 can be moved vertically along the wall stand 30.

Also, as shown in FIG. 1, the imaging system 12 includes a workstation 34, a display device 36, and a printer 37. In one embodiment, workstation 34 includes or provides the functionality of imaging system 12 so that user 38 can control the operation of source 16 and detector 22 by interacting with workstation 34. can do. In other embodiments, the functions of the imaging system 12 are distributed, some functions of the imaging system 12 (eg, the function of controlling the operation of the source 16) are performed on the workstation 34, and others. Functions (eg, functions that control the operation of the detector 22) can be performed by another component of the X-ray system 10, such as the portable detector controller 40. The portable detector controller 40 can be a personal digital assistant (PDA), palmtop computer, laptop computer, smart phone, tablet computer (eg, iPad®), or any suitable general purpose or A dedicated portable interface device can be included. The portable detector controller 40 is configured to be held by the user 38 and wirelessly communicate with the detector 22. The detector 22 and portable detector controller 40 utilize any suitable wireless communication protocol, such as the IEEE802.15.4 protocol, ultra-wideband (UBW) communication standard, Bluetooth communication standard, or any IEEE802.11 communication standard. Note that you can. Instead, the portable detector controller can be configured to tether or detachably moor to the detector 22 for communication over a wired connection.

The portable detector controller 40 is also configured to send a command (eg, detector operating mode) to the detector 22 to acquire X-ray image data. In that case, the detector 22 prepares for X-ray irradiation in response to a command from the portable detector controller 40, indicating that the detector 22 is ready to receive X-ray irradiation. It is configured to send a ready signal to device 40. The device 40 can also be configured to transmit patient information or X-ray technical information to the detector 22. Like the detector 22, device 40 has no communication from the control device of the X-ray source 16. Further, the portable detector controller 40 is configured to receive X-ray image data from the detector 22 for processing and image reconstruction. In fact, both the detector 22 and the portable detector controller 40 are configured to process the X-ray image data at least partially. However, in certain embodiments, the detector 22 and / or the portable detector controller 40 is configured to completely process the X-ray image data. The detector 22 and / or device 40 is also configured to generate a DICOM compliant data file based on X-ray image data, patient information, and other information. Further, the detector 22 and / or the device 40 wirelessly transmits the processed X-ray image data (for example, partially or completely processed X-ray image data) to the in-facility image review and storage system via the network 42. It is configured to send (or make a wired connection). Institutional image review and storage systems can include hospital information systems (HIS), radiological information systems (RIS), and / or image storage communication systems (PACS). In some embodiments, the in-facility image review and storage system can process x-ray image data. In one embodiment, workstation 34 can be configured to act as a server for instructions and / or content on network 42 of a medical facility. The detector 22 and / or device 40 also processed the X via a wired or wireless connection.

The portable detector control device 40 includes a user-observable screen 44 and is configured to display patient data and a reconstructed X-ray image on the screen 44 based on the X-ray image data. The screen 44 can include a touch screen and / or an input device (eg, a keyboard) configured to enter data (eg, patient data) and / or commands (eg, to a detector). For example, device 40 can be used to input patient information and other imaging related information (eg, source 16 type, imaging parameters, etc.) to form a DICOM image header. In one embodiment, patient information can be transferred from the patient database via a network or wireless or wired connection from workstation 34 to device 40. The detector 22 and / or the device can generate a DICOM compliant data file by incorporating the information for the image header together with the X-ray image. The device 40 can also be used to navigate the X-ray image displayed on the screen 44. In addition, device 40 can be used to modify an X-ray image, for example by adding a position marker (eg, "L" for the left and "R" for the right) on the image. In one embodiment, a metal marker can be placed on the detector 22 to generate a position marker.

In one embodiment, the imaging system 12 can be a stationary system located in a fixed X-ray imaging chamber, as outlined in FIG. 1 and described above. However, it will be appreciated that the techniques disclosed herein can also be used for other imaging systems, including mobile X-ray units and systems in other embodiments.

For example, as illustrated in the X-ray system of FIG. 2, the imaging system 12 can image the patient 20 without the need to transport the patient 20 to a dedicated (ie, fixed) X-ray imaging system. It can be moved to a patient recovery room, emergency room, operating room, or any other space that allows it. The imaging system 12 includes a mobile X-ray base station 39 and a detector 22. As mentioned earlier, the imaging system 12 may be a conventional analog imaging system modified for digital image data acquisition and processing. In one embodiment, the support arm 41 can be moved vertically along the stanchion 43 to facilitate positioning of the radiation source 16 and the collimator 18 with respect to the patient 20. Further, one or both of the support arm 41 and the strut 43 can also be configured to allow the radiation source 16 to rotate around an axis. Further, the X-ray base station 39 has a wheeled base 45 for moving the station 39. A system electronic circuit 46 with a base unit 47 powers and controls the X-ray source 16 and the wheeled base 45 in the imaging system 12. The base unit 47 also has an operator workstation 34 and a display device 36, which allows the user 38 to operate the X-ray system 10. The operator workstation 34 may include buttons, switches, etc. to facilitate the operation of the X-ray source 16. Similar to the X-ray system 10 in FIG. 1, the system 10 includes a portable controller 40. The detector 22 and the portable control device 40 are as described above. In an X-ray system, patient 20 may be placed on bed 49 (or gantry, table, or any other support) between X-ray source 16 and detector 22 to irradiate X-rays. Yes, the X-ray passes through patient 20 and is received by detector 22.

FIG. 3 is a schematic configuration diagram of the X-ray system 10 of FIGS. 1 and 2, showing the components of the system 10 in more detail. The imaging system 10 includes an X-ray radiation source 16 located adjacent to the collimator 18. The collimator 18 can pass a radiation flow 48 through the area where the object 20 (eg, patient 20) is located. Part of the radiation 50 passes through or around the object 20 and collides with the digital X-ray detector 22. As described in more detail below, the detector 22 converts the X-ray photons received on that surface into photons of relatively low energy and then into electrical signals. These electrical signals are acquired and processed to reconstruct images that represent various features inside the object 20.

The source 16 is coupled to a power supply 52 that supplies power for the inspection sequence. The source 16 and power supply 52 are coupled to a source control device 54 that is configured to direct the emission of X-rays for imaging irradiation. As described above, the detector 22 is configured to acquire the X-ray image data even if there is no communication from the radiation source control device 54. In an alternative embodiment, the detector 22 responds to a portable detector controller configured to transmit instructions to the detector 22 for acquisition of X-ray image data. Further, the portable detector controller 40 is configured to receive X-ray image data from the detector 22 for processing and image reconstruction.

The detector 22 includes a wireless communication interface 56 for wireless communication with the device 40, and also includes a wired communication interface 58 for communicating with the device 40 when the device 40 is moored to the detector 22. The detector 22 and the device 40 can also communicate with the in-facility image review and storage system via the network 42 via a wired or wireless connection. As mentioned earlier, institutional image review and storage systems can include PACS60, RIS62 and HIS64. It should be noted that the wireless communication interface 56 can utilize any suitable wireless communication protocol, such as an ultra-wideband (UBW) communication standard, a Bluetooth communication standard, or any IEEE 802.11 communication standard. Further, the detector 22 is coupled to a detector controller 66 that coordinates control of various detector functions. For example, the detector controller 66 can perform various signal processing and filtering functions such as initial adjustment of dynamic range, interleaving of digital image data, and the like. The detector controller 66 responds to the signal from the device 40. The detector controller 66 is connected to the processor 68. The processor 68, the detector controller 66, and all circuits receive power from the power supply 70. The power supply 70 can include one or more storage batteries.

Further, the processor 68 is connected to the detector interface circuit 72. The detector 22 can convert the X-ray photons received on its surface into photons with relatively low energy. The detector 22 includes a detector array 74, which contains an array of photodetectors that convert photons of light into electrical signals. Instead, the detector 22 can convert X-ray photons directly into electrical signals. These electrical signals are converted to digital values by the detector interface circuit 72, the detector interface circuit 72 supplies those values to processor 68, and those values are converted to imaging data by processor 68 to be the object. It is sent to device 40 to reconstruct images of various features in 20. In one embodiment, the detector 22 can process the imaging data at least partially or completely. Instead, the imaging data can be sent from the detector 22 to the server to process the imaging data.

The processor 68 is also connected to the lighting circuit 76. The detector controller 66 sends a signal to the processor 68 in response to the signal received from the device 40, which indicates that the detector 22 is ready to receive X-ray irradiation in response to the signal. Therefore, the lighting circuit 76 can be operated to turn on the light 78. In fact, the detector 22 can turn on or switch from idle to active in response to a signal from device 40. Instead, the detector 22 can be turned on or switched from idle to active by the user (eg, by pressing an on / off button located on the detector 22).

In addition, the processor is attached to memory 80. The memory 80 can store various configuration parameters, calibration files, and detector identification data. In addition, the memory 80 can receive and store patient information to be combined with image data from the device 40 in order to generate a DICOM compliant data file. Further, the memory 80 can store the sampled data collected during the imaging mode together with the X-ray image. As mentioned earlier, in some embodiments, device 40 can perform image processing and incorporate DICOM headers to generate DICOM compliant data files.

FIG. 4 is a schematic view showing the functional components of the digital detector 22. As shown, the detector control circuit 84 receives DC power from the power source roughly represented by reference numeral 86. The detector control circuit 84 is configured to generate timing and control commands for row and column electronic elements used to acquire image data during the data acquisition stage of system operation. Therefore, circuit 84 sends power and control signals to reference / regulator circuit 88 and also receives digital image pixel data from circuit 88.

In one embodiment, the detector 22 comprises a scintillator that converts X-ray photons received on the surface of the detector into photons of relatively low energy (light). An array of photodetectors converts the photons of those lights into electrical signals. The electrical signal represents the number of photons or the intensity of radiation that collide with individual pixel areas or pixels on the surface of the detector. In currently conceivable embodiments, X-ray photons can be directly converted into electrical signals. The resulting analog signal is converted into a digital value by a readout electronic device, and the digital value can be processed, stored, and displayed by the device 40 or the like after image reconstruction. In one form, the photodetector array is made of amorphous silicon. An array of photodetectors or individual pixels is arranged in rows and columns, each individual pixel consisting of a photodiode and a thin film transistor. The cathode of each diode is connected to the source of the transistor and the anodes of all diodes are connected to a negative bias voltage. The gates of the transistors in each row are connected together and the column electrodes are connected to the scanning electrodes as described below. The drains of a row of transistors are connected together, and the electrodes in each row are connected to the individual channels of the readout electronics.

As described in more detail below, the detector control circuit 84 is configured to sample data from individual pixels before and during X-ray irradiation. Also, the detector control circuit 84 is configured to apply a first voltage to the transistors of the individual pixels before receiving X-ray irradiation (eg, when the detector 22 is maintained in idle mode). .. Further, the detector control circuit 84 acquires the X-ray image data while applying a second voltage (higher than the first voltage) to the transistor of the individual pixel which has not been sampled before being irradiated with X-ray. It is configured to sample data from ready individual pixels. The sampled data collected prior to X-ray irradiation is stored by the detector control circuit 84 for use in reconstructing a user-observable image from the X-ray image data. Further, the detector control circuit 84 samples data (including X-ray image data) from the individual pixels while applying a second voltage to the transistors of the individual pixels that have not been sampled while receiving X-ray irradiation. It is configured to do. After the end of the X-ray irradiation time, the detector control circuit is configured to resume applying the first voltage to the transistors of the individual pixels.

To restate the embodiment shown in FIG. 4, as an example, the line bus 90 enables reading from various lines of the detector 22 and also disables those lines. Impossible) and contains multiple conductors to apply charge compensation voltage to the selected rows if desired. The column bus 92 includes a plurality of separate conductors for commanding reads from the column while the rows are sequentially enabled. The generatrix 90 is coupled to a series of row drives 94, each of which commands the enablement of a series of rows in the detector 22. Similarly, the readout electronic device 96 is coupled to the column bus 92 to direct the readout of all columns of the detector.

In the illustrated embodiment, the row drive device 94 and the readout electronics device 96 are coupled to the detector panel 98, which can be divided into a plurality of compartments 100. Each compartment 100 is coupled to the row drive 94 one by one and contains a plurality of rows. Similarly, each row drive 96 is coupled into a series of rows. Thereby, the previously described photodiode and thin film transistor configuration defines a series of pixels or individual pixels 102, the individual pixels of which are arranged in a plurality of rows 104 and a plurality of columns 106. These rows and columns define an image matrix 108 with a height of 110 and a width of 112.

Further, as shown in FIG. 4, each pixel 102 is generally defined by the intersection of rows and columns, at which the column electrode 114 intersects the row electrode 116. As described above, the thin film transistor 118 is provided at the position of each intersection for each pixel, and the photodiode 120 is also provided in the same manner. When each row is enabled by row drive 94, the signal from each photodiode 120 can be read by the readout electronics 96 and converted to a digital signal for subsequent processing and image reconstruction. Thus, the pixels 102 of the entire row in the array are controlled simultaneously when the scan lines attached to the gates of all the transistors 118 of the pixels 102 in that row are activated. As a result, each pixel 102 in that particular row is connected to a data line via a switch, which switch is used by the readout electronics to restore the charge to the photodiode 120.

Here, in some systems, when all pixels 102 in one row are simultaneously recharged by each of the associated dedicated read channels, the readout electronics will take measurements from the previous row. Note the conversion from analog values to digital values. Furthermore, the readout electronics can transfer the digital values from the previous line to the acquisition subsystem, which performs some processing before displaying the diagnostic image or writing it on film.

The circuit used to enable the row is, in this example, with a row enable or field effect transistor (FET) circuit based on the use of a field effect transistor for such enable operation (row drive). Can be called. The FETs associated with the row enable circuit described above are turned "on" or conductive to enable the row and "off" or non-conductive when the row is not enabled for reading. Apart from such terms, the particular circuit components used for row drive and column readout electronics can be modified, and the invention is not limited to the use of FETs or specific circuit components. Please note.

As mentioned earlier, the detector 22 has no communication from the source controller 54 and therefore has no a priori knowledge of the start and end points of irradiation. In one embodiment, the detector 22 is configured to automatically continue to detect the start and end of X-ray irradiation and form an X-ray image without communication with the detector control device 40. In another embodiment, the detector 22 remains in idle power mode and is configured to switch to imaging power mode after receiving a command from the detector controller 40. The detector 22 begins to detect the start and end of X-ray irradiation after being switched to full power mode. This results in a unique dynamic workflow between the X-ray system 12, the detector 22 and the portable detector controller 40, as illustrated in FIGS. 5 and 6. FIG. 5 is a schematic diagram showing a bidirectional interaction between the detector 22 and the portable detector controller 40. FIG. 5 illustrates an imaging system 12 in which patient 20 on table 28 is positioned between X-ray source 16 and detector 22. As mentioned earlier, the imaging system 12 may be a fixed or mobile system. FIG. 6 is a flow diagram of method 124 for a workflow between the detector 22 and the portable detector controller 40. First, the user turns on detector 22 (block 126). The detector 22 remains in idle mode when it is on. As shown in FIG. 5, the detector 22 is placed directly below the object 20. Before or after turning on the detector 22, the user inputs patient information or other information (eg, X-ray technology) related to imaging (eg, image parameters) into device 40 (blocking). 128). In some embodiments, the detector controller 40 may transmit information to the detector 22 to form, for example, a DICOM compliant data file. In other embodiments, DICOM-compliant data files are formed within the detector controller 40 so that patient information does not need to be transferred to the detector 22.

The user sends a detector preparation command signal from device 40 to detector 22 (block 130). When the detector 22 receives the preparation command from the device 40, the detector 22 prepares for the acquisition of the X-ray image data. Specifically, the detector 22 switches from idle mode to imaging power mode to scrubbing the panel of the detector 22. Start (ie, prepare and refresh the detector circuit) to equilibrate the panel. After scrubbing, the detector 22 reads or acquires one or more offset frames prior to irradiation. More specifically, the detector 22 prepares for irradiation by initiating sampling of data from the matrix of detector elements. After preparation, detector 22 sends a detector ready signal to device 40 (block 132). In one embodiment, the detector 22 can also provide a visible display (eg, flashing light) or an audible display indicating that the detector is ready. In another embodiment, the detector controller 40 can provide a visible and / or audible display. The user then commands the X-ray source 16 to perform X-ray irradiation via the source controller 54 coupled to the source 16 (block 134).

During and after irradiation, the detector 22 samples data from the matrix of detector elements. In certain embodiments, the detector 22 processes the X-ray image data at least partially (block 136). Instead, the detector 22 can completely process the X-ray image data. The process involves determining when the irradiation begins and ends based on a comparison of the sampled image data generated by the detector 22. As described in more detail below, the sampled image data can be collected from one or more frames and combined to generate a reconstructed image. The detector 22 stops sampling after determining the end of irradiation and after sampling all of the X-ray image data from the plurality of frames. During and after irradiation, the detector controller 40 acquires X-ray image data from the detector 22 (block 138), at which time the detector 22 shifts from imaging power mode to idle mode. In certain embodiments, device 40 processes X-ray image data at least partially (block 140). In some embodiments, the device 40 completely processes the X-ray image data. Instead, device 40 acquires fully processed X-ray image data from the detector. In another embodiment, neither the detector 22 nor the device 24 completely processes the X-ray image data and sends the X-ray image data to an in-facility image review and storage system for subsequent processing.

As seen in FIG. 5, a reconstructed image 122 based on the X-ray image data is displayed on screen 44 of device 40 (block 142). In fact, the reconstructed image 122 can be displayed on the apparatus 40 while the imaging object 20 is present at the location where the X-ray image data is acquired. After displaying the image 122 on the device 40, the user determines if the image is acceptable (block 144). If the image is unacceptable due to positioning issues, the imaging object 20 can be repositioned for yet another irradiation (block 146). If the image is acceptable, the user selects the part of the image of interest, adds an "L" and / or "R" position mark, and detects the processed X-ray image data in the detector 22 and / or It can be sent to the in-facility image review and storage system by device 40 (block 148).

Since no timing signal is transmitted from the source controller 54 to the detector 22 regarding the performance of the irradiation by the source 16, the detector may have one or more frames (eg, before, during, and after the irradiation). Data from offset frames and imaging frames) are sampled. The length of X-ray irradiation depends on a number of factors, such as the type of x-ray examination and the size of the object. For example, irradiation may overlap in multiple frames, and sampled X-ray data from at least two imaging frames may need to be combined. However, in order to do this, it is necessary to determine the start and end frames that extend for at least the duration of the irradiation.

FIG. 7 is a diagram showing the sampling and combination of X-ray image data when irradiation occurs within a single readout or sampling period. FIG. 7 illustrates a plurality of frames 150 obtained by sampling a matrix of detector elements. These frames 150 include offset frames 152 and 154 and imaging frames 156 and 158. Offset-corrected X-ray images by combining the sampled data from imaging frames 156 and 158 with the sampled data collected prior to obtaining imaging frames 156 (eg, offset data from offset frame 152). Is generated. The offset frame 152 is acquired prior to the start of irradiation. Offset frames 154 are acquired after irradiation is complete and those frames 150 do not contain any further image data. Neither offset frames 152 nor 154 contain image data.

Row averaging is calculated for each frame 150 to determine the start and end of irradiation and imaging data. The row average reflects the average amount of charge supplied to each detector element in a row of detector elements in the detector array to fully charge each detector element. The illustrated curve 159, drawn from top to bottom, shows the row average of each row along a plurality of frames 150. Row averaging at the upper portion 160 of the offset frame 152 and the imaging frame 156 is shown at portion 162 of curve 159 because no irradiation has been made and the detector element remains fully charged. As it is, it can be ignored. The start and end of irradiation are indicated by lines 164 and 166, respectively. Line 164 produces 0% irradiation (ie, zero percent of the total irradiation length), while line 166 produces 100% irradiation. As a result, during irradiation, each row is read sequentially within region 170, so that the row mean increases linearly, as shown by part 168 of curve 159. More specifically, because each subsequent row is exposed to a larger percentage (longer time) and the detector elements in those rows require more charge recovery (supply). , The row mean in part 168 increases. For example, the first row read after the start of irradiation can receive 10% irradiation before reading, while the last row read can receive 100% irradiation before reading. Can be done.

Both imaging frames 156 and 158 contain the image data shown in the oblique parallel pattern regions 172 and 174, respectively, since the irradiation was completed within a single sampling or reading period. The flat portion 176 of curve 159 indicates that rows in regions 178 and 180 of imaging frames 156 and 158 were irradiated to 100% irradiation prior to reading. Lines 182 and 184 indicate the start and end of a row read in area 186 of frame 158, which corresponds to area 170 of frame 156, respectively. As shown by part 188 of curve 159, the row mean decreases linearly as each row in region 186 is read sequentially. More specifically, in region 186, the row average is reduced because each subsequent row receives a smaller percentage of irradiation after the first read of the rows in region 170 of read frame 156. In other words, the row mean in region 186 reflects the image due to residual irradiation after the last read of the row. For example, the first row read in region 180 of frame 158 is 90% illuminated after the first read of the first row in region 170 of frame 156, whereas the last row read in region 180. Will have received 10% irradiation after the first read of the last row in region 170 of frame 156. Part 190 of curve 159 shows that the row averaging at the lower part 192 of the imaging frame 158 and the offset frame 154 is negligible because the detector element has been recharged since the last read. As a result, the start and end of irradiation and the start and end of imaging data can be determined by determining the row average.

All frames 150 (eg, frames 156 and 158) containing the image data are combined (ie, added) to obtain an X-ray image. To obtain an offset-corrected X-ray image, the total number of frames 150 used to create the X-ray image (eg, 2 (frames 156 and 158)) is combined with the calculated offset image (eg, offset frame 152). Is then subtracted from the X-ray image to form an offset-corrected X-ray image.

Row averaging can also be used when the irradiation spans more than one read or sampling period. FIG. 8 is a diagram showing the sampling and combination of X-ray image data when irradiation occurs over two readout or sampling periods. Similar to FIG. 7, FIG. 8 illustrates a plurality of frames 150 obtained by sampling a matrix of detector elements. The plurality of frames 150 include offset frames 194 and 196, as well as imaging frames 198, 200 and 202. The offset frame 194 is acquired prior to the start of irradiation. The offset frame 196 is acquired after the irradiation is finished, and the frame 150 does not contain any more image data. As mentioned earlier, neither offset frames 194 nor 196 contain image data.

As in the case of FIG. 7, the row average is calculated for each frame 150 in FIG. Curve 204 shows the row mean of each row from top to bottom along a plurality of frames 150. Row averaging at the upper portion 206 of the offset frame 194 and the imaging frame 198 is shown by portion 208 of curve 204 because no irradiation has been made and the detector element remains fully charged. As it is, it can be ignored. The start and end of irradiation are indicated by lines 210 and 212, respectively. Line 210 produces 0% irradiation and line 212 produces 100% irradiation. As shown, the irradiation spans two sampling periods, and thus two imaging frames 198 and 200. Similar to FIG. 7, FIG. 8 contains a linearly increasing row mean as shown by part 214 of curve 204 corresponding to regions 216 and 218 of imaging frames 198 and 200. Also, the flat portion 220 of curve 204 corresponds to region 222 of the imaging frame 200, indicating that those rows were 100% illuminated prior to reading. Part 220 is much shorter than part 176 in FIG. 7 because the irradiation in FIG. 8 is relatively long over two or more imaging frames, which is 100% irradiated prior to reading. This means that the number of detector elements is smaller. In addition, portion 224 of curve 204 corresponds to regions 226 and 228 of the imaging frames 200 and 202, respectively, and contains a linearly decreasing row mean. The portions 214 and 224 of the curve 204 have a smaller slope than the portions 168 and 188 of the curve 159 in FIG. 7 because the irradiation is relatively long in FIG.

Due to the long irradiation over the two sampling periods, the imaging frames 198, 200 and 202 contain the image data shown in the oblique parallel pattern regions 230, 232 and 234, respectively. As mentioned earlier, the start and end of irradiation and the start and end of imaging data can be determined by determining the row mean.

All frames 150 containing image data (eg, multiple frames 198, 200 and 202) are combined (ie, added) to obtain an X-ray image. To obtain an offset-corrected X-ray image, the total number of frames 150 used to create the X-ray image (eg, 3 (frames 198, 200 and 202)) is calculated as the offset image (eg, offset frame). 194) is then multiplied and then subtracted from the X-ray image.

In an alternative form, X-ray irradiation may occur between read periods. FIG. 9 is a diagram showing sampling of X-ray image data when irradiation occurs between the end of one readout period and before the start of the next readout. Similar to the previous case, FIG. 9 illustrates a plurality of frames 150 obtained from sampling a matrix of detector elements. These frames 150 include offset frames 221 and 223, as well as imaging frames 225. The offset frame 221 is acquired prior to the start of irradiation. The offset frame 223 is acquired after the irradiation is finished, and the frame 150 does not contain any more image data. Neither offset frames 221 and 223 contain image data. As in the case of FIGS. 7 and 8, in FIG. 9, the row average is calculated for each frame. Curve 227 shows the row mean for each row from top to bottom along a plurality of frames 150. The row averaging at the offset frame 221 can be ignored because no irradiation has been made and the detector element remains fully charged. The start and end of irradiation are indicated by lines 229 and 231 respectively. As shown, irradiation occurs between reads of frames 221 and 225. Therefore, part 233 of curve 227 represents that all rows have been 100% irradiated prior to reading. As a result, the image data represented by the oblique parallel pattern region 235 is located in a single frame 225, so it is not necessary to combine the imaging frame 225 with any other frame. To obtain an offset-corrected X-ray image, the calculated offset image (eg, offset frame 221) is subtracted from the X-ray image (eg, frame 225).

Electronic noise when combining sampled X-ray image data from multiple frames (eg, at least two imaging frames) to create X-ray image data that can be reconstructed into a user-observable image. May occur. For example, suppose you want to obtain an X-ray image by combining three imaging frames with the same offset, O_{i, j}Given the pixel P as representing the offset value_{i, j}The final value of the pixel is the value represented by the following equation (1).

<maths num="1"><img id="000002" he="28" wi="158" file="JP6074366B2_D0001.tif" img-format="tif" img-content="drawing" /></maths> The average of electronic noise is expressed by the following equation (2).

<maths num="2"><img id="000003" he="29" wi="159" file="JP6074366B2_D0001.tif" img-format="tif" img-content="drawing" /></maths>The dispersion of electronic noise is expressed by the following equation (3).

<maths num="3"><img id="000004" he="26" wi="159" file="JP6074366B2_D0001.tif" img-format="tif" img-content="drawing" /></maths> As shown in the above equation, the electronic noise has an average value of zero, and the four values P_{i, j}⁽¹⁾, P_{i, j}⁽²⁾, P_{i, j}⁽³⁾And P_{i, j}⁽⁴⁾Are independent of each other, so by combining N offset-corrected images with the same offset, the electronic noise of the X-ray image becomes the value expressed by the following equation (4) with σ as the standard deviation.

<maths num="4"><img id="000005" he="37" wi="158" file="JP6074366B2_D0001.tif" img-format="tif" img-content="drawing" /></maths> Another way to reduce electronic noise is to use different offsets for each imaging frame. In that case, the electronic noise becomes the value expressed by the following equation (5).

<maths num="5"><img id="000006" he="21" wi="116" file="JP6074366B2_D0001.tif" img-format="tif" img-content="drawing" /></maths> Yet another way to reduce electronic noise is to use an average offset for each read frame. It is assumed that the offset is calculated by averaging M dark frames (ie, offset frames). The offset noise has a value expressed by the following equation (6).

<maths num="6"><img id="000007" he="27" wi="137" file="JP6074366B2_D0001.tif" img-format="tif" img-content="drawing" /></maths>In addition, the noise of the combined image has a value represented by the following equation (7).

<maths num="7"><img id="000008" he="24" wi="115" file="JP6074366B2_D0001.tif" img-format="tif" img-content="drawing" /></maths> When M&gt; N, equation (7) is smaller than equation (5). Therefore, when the number of imaging frames is small (eg N = 2), the average offset is preferred. However, when the number of imaging frames to be combined is larger, it is preferable to use the same offset or different offsets.

FIG. 10 is a flow chart of a method 236 incorporating the above-mentioned technique for creating X-ray image data that can be reconstructed into a user-observable image by sampling and combining the X-ray image data. Method 236 includes the step of preparing the detector 22 (block 238). Preparation of the detector 22 can include initiating sampling of data (eg, offset data) prior to the start of irradiation or independently of the start of irradiation. After the preparation of the detector 22, method 236 includes performing X-ray irradiation by the X-ray source 16 if the X-ray source responds to the source controller 54 (block 240). After the start of irradiation, even if there is no a priori knowledge about the start and end points of X-ray irradiation (that is, without the transmission of the timing signal from the source controller 54), the X-ray image by the detector 22 Data sampling occurs (block 242). In fact, sampling of X-ray image data can occur during X-ray irradiation. Method 236 further includes determining the start and end frames (eg, imaging frames) of the X-ray image data (block 244). The start and end frames extend at least for the duration of the irradiation. As mentioned earlier, irradiation can occur in a single imaging frame, but X-ray image data can also reside in multiple imaging frames. Thus, the start and end frames can include data sampled during the duration of irradiation and data sampled outside the duration of irradiation. In particular, the start and end frames are determined by at least comparing the sampled data of each frame and end frame. As mentioned earlier, start and end frames are determined by identifying changes in sampled data values (eg, row averages) that represent X-ray doses.

Furthermore, Method 236 can be user-observable by combining sampled X-ray image data from at least two imaging frames, at least one of which extends over the duration of the irradiation. Including the step of creating X-ray image data that can be reconstructed into a simple image (block 246). As mentioned earlier, X-ray image data that can be reconstructed into a user-observable image is created by generating offset-corrected image data based on data sampled from at least two imaging frames. can do. For example, offset-corrected image data is generated by combining sampled data prior to the start imaging frame with data sampled from at least two imaging frames, as described above. Further, the step of combining the sampled X-ray image data of at least two imaging frames involves selecting the combination method based on the noise parameters. In other words, as mentioned earlier, the noise calculation depends on the number of imaging and offset frames (ie, offset frames) sampled before and during irradiation, and is more than one. An appropriate formula is selected from the above formulas so as to reduce electronic noise when the data sampled from the frame is combined.

The technique described above is illustrated in FIG. 11, which is a diagram representing a workflow in an acquisition sequence in which both image data and offset data are acquired to create a user-observable image. FIG. 11 includes the acquisition sequence 248 of the detector 22 corresponding to the interaction between the detector 22 and the portable detector controller 40 and the operator or user 38 and the X-ray source 16. The operation of the detector 22, the device 40, and the source 16 is as described above. While the detector 22 is in idle mode represented by region 250 in sequence 248, operator 38 configures source 16 as indicated by arrow 252. The configuration settings of the radiation source 16 can include settings of irradiation parameters and irradiation types. Also, the operator can position the imaging object and the source 16 while the detector 22 remains in idle mode. Further, the operator 38 inputs an instruction to the device 40 and sends an instruction 256 to the detector 22 in preparation for irradiation, as indicated by the arrow 254.

Upon receiving an instruction to prepare for the acquisition of X-ray image data, the detector 22 enters imaging power mode 258. The detector 22 initiates scrubbing of the panel, as shown in region 260 of acquisition sequence 248, to balance the circuits on the panel. The detector 22 then reads one or more offset frames from the panel (eg, region 262), at which time the detector 22 sends a detector ready signal 264 to device 40. In one embodiment, the device 40 provides a visible display to indicate the ready state of the detector 22. In another embodiment, the device 40 provides an audible display. In another embodiment, device 40 provides both video and audible display. In yet another embodiment, the detector 22 provides a visible display (eg, a flashing LED) to indicate the ready state of the detector 22. In another embodiment, the detector 22 provides an audible display. In yet another embodiment, the detector 22 provides both video and audible display. Operator 38 receives a readiness signal at device 40, as indicated by arrow 266. Once the detector 22 is ready, the detector 22 begins continuously sampling or reading frames, as shown in region 268 of acquisition sequence 248, to detect irradiation. At any time, the operator can start irradiation from source 16 as indicated by arrow 270. When irradiation is initiated, detector 22 receives X-ray 272 from source 16. The detector 22 samples a plurality of frames to determine the start and end frames (eg, frames 274 and 276) that extend over the irradiation. After the irradiation is complete, the detector 22 processes the acquired image data and sends a preview of the reconstructed image to the device 40 for observation by the operator 38, as indicated by arrow 278. Instead, the data can be sent to device 40 for further processing and generation of reconstructed images. After irradiation is complete, detector 22 is shown in region 280 of acquisition sequence 248.

As mentioned earlier, the detector 22 transitions from idle mode to imaging power mode. In imaging power mode, the detector 22 reads the panel continuously as there is no a priori knowledge (or data) about when irradiation can occur. Therefore, reading or sampling of data from the panel occurs during irradiation. The individual pixel transistors being sampled (eg, FETs) are in a conductive state when the row is enabled for reading. However, leakage (eg, FET leakage) can occur from unsampled individual pixel transistors (ie, transistors that are non-conductive when rows are not enabled for reading). Voltage (V) that keeps unsampled transistors non-conductive_off) Can be increased to reduce FET leakage. However, the reduction in leakage may not persist if the transistor is biased for a short time due to bias aging.

12 and 13 illustrate embodiments of techniques that overcome these problems. FIG. 12 is a diagram showing an acquisition sequence 282 in which different voltages are applied to reduce transistor leakage while sampling image data, especially during irradiation. The acquisition signal 282 in FIG. 12 is the same as the acquisition signal 248 described in FIG. The acquisition signal 282 includes regions 250 and 280 that keep the detector 22 in idle mode. The acquisition signal 282 also includes a region where the detector 22 scrubs the panel (eg, region 260) and a period during which the panel is sampled or read (eg, regions 262 and 268). The detector 22 has a first voltage of 284 (eg, a small negative V) on the transistors of the individual pixels when the detector 22 is kept in idle mode (eg regions 250 and 280)._off) Is applied. Therefore, the detector 22 applies a first voltage 284 to the transistors of the individual pixels before receiving X-rays (eg, region 250). The detector 22 is second to the unsampled individual pixel transistor when the detector 22 moves into imaging power mode 258 (eg, regions 260, 262 and 268) and begins sampling data from the individual pixels. Voltage of 286 (for example, greater negative V_off) Is applied. In one embodiment, a first voltage 284 can be applied instead of a second voltage 286 during panel scrubbing (ie, region 260). Applying a second voltage 286 to an unsampled individual pixel transistor also occurs when receiving X-rays from the detector 22. At the end of sampling data from the individual pixels (eg, region 280), the detector 22 reapplies a first voltage 284 to the transistors of the individual pixels after the detector 22 has finished receiving X-rays.

The second voltage 286 is a negative voltage greater than the first voltage 284. The second voltage 286 can be at least about 1.3 times the first voltage 284. For example, the first voltage 284 can be equal to or less than about -11 volts. The second voltage 286 can be equal to or greater than about -15 volts. The first and second voltages 284 and 286 keep the transistor non-conductive. By maintaining the second voltage 286 only during imaging power mode 258 and shifting to the first voltage 284 in idle mode (eg regions 250 and 280), transistor leakage is reduced while avoiding bias aging. be able to.

FIG. 13 is a flow diagram of method 288 for sampling data from the detector before and after X-ray irradiation while applying different voltages to reduce transistor leakage. Method 288 comprises applying a first voltage 284 to the transistors of the individual pixels (eg, when the detector 22 is maintained in idle mode) (block 290). While preparing for the acquisition of X-ray image data, method 288 is to unsampled individual pixel transistors if the second voltage 286 is a negative voltage greater than the first voltage 284. It includes the step of sampling data from individual pixels while applying a second voltage 286 (block 292). When sampling data while applying a second voltage 286, the detector 22 collects the sampled data prior to X-ray irradiation for use in reconstructing a user-observable image from the X-ray image data. Can be saved (block 294). Method 288 also includes the step of receiving X-ray irradiation from the X-ray source 16 at the detector 22 (block 296). After irradiation, X-ray image data is sampled from the individual pixels while applying a second voltage 286 to the transistors of the individual pixels that have not been sampled (block 298). Sampling of data from individual pixels is also done while receiving X-rays. After the end of receiving the X-rays, the detector 22 finishes sampling the X-ray image data from the individual pixels (block 300) and also, for example, during the transition to idle mode, first to the transistors of the individual pixels. Reapply voltage 284 (block 302). As mentioned earlier, by maintaining the second voltage 286 only during the imaging power mode and shifting it to the first voltage 284 in idle mode, transistor leakage can be reduced while avoiding bias aging. it can.

The technical effects of various embodiments include providing methods and systems that can modify conventional X-ray systems by replacing film cassettes with digital X-ray detectors. When modifying an X-ray system, the digital X-ray detector does not communicate with the X-ray imaging system. Instead, the detector communicates with the portable detector controller to receive instructions. Since the detector does not communicate with the X-ray system, the detector lacks data indicating the timing signal for X-ray irradiation. There, the detector can continuously read the panel of the detector during preparation for irradiation and during irradiation. The detector determines the beginning and end of irradiation and imaging data, collects and combines X-ray image data from multiple frames, and factors that can adversely affect image quality (eg, electrical noise and). Techniques for reducing transistor leakage) can be included.

The present invention includes the present invention, including the best embodiments, to disclose the present invention, and to allow one of ordinary skill in the art to create and use any device or system to carry out any adopted method. Various examples were used to enable the implementation of. The patentable scope of the present invention is set forth in the description of "Claims" and may include other examples conceivable to those skilled in the art. Other examples of such are cases where they have structural elements that are substantially the same as the literal description of the "Claims", or they are substantial from the literal description of the "Claims". If it contains equivalent structural elements with no difference, it shall be within the scope of the claims.

10 X-ray system 12 Imaging system 14 Overhead X-ray tube support arm 16 Radiation source 18 Collimator 20 patients 22 Detector 24 detector 26 dock 28 Patient table 30 wall stand 32 Receptive structure 34 workstation 36 Display device 37 printer 38 users 39 Mobile X-ray Base Station 40 Portable detector controller 41 Support arm 42 network 43 props 44 User-observable screen 45 Wheeled base 46 System electronic circuit 47 base unit 49 beds 48 Radiation 50 radiation 78 lights 86 power supply 90 Generatrix 92 row bus 94 line drive 96 Read electronic device 98 Detector panel 100 parcels 102 individual pixels 104 lines 106 columns 108 Image Matrix 110 height 112 width 114 row electrodes 116 row electrode 118 Thin film transistor 120 photodiode 122 Reconstructed image 124 Methods for workflow between detector and portable detector controller 150 multiple frames 152, 154 offset frame 156, 158 Imaging frame 159 Row average curve 160 Upper part of frame 156 162, 168, 176, 188, 190 Curve 159 164 Line indicating the start of irradiation 166 Line indicating the end of irradiation 170, 178 Frame 156 area 172, 174 Oblique parallel pattern area containing image data 180, 186 Frame 158 area 182 Line indicating the start of reading Line indicating the end of reading 184 lines 192 Lower part of frame 158 194, 196 offset frame 198, 200, 202 Imaging Frame 204 Row average curve 206 Upper part of frame 198 208, 214, 220, 224 Curve 204 210 Line indicating the start of irradiation 212 Line indicating the end of irradiation 216 frames 198 areas Area of 218, 222, 226 frame 200 228 Area of frame 202 230, 232, 234 Oblique parallel pattern area containing image data 221,223 offset frame 225 Imaging Frame 227 Curve showing row mean 229 Line indicating the start of irradiation 231 Line indicating the end of irradiation 233 Part of curve 227 235 Oblique parallel pattern area containing image data 236 How to create X-ray image data 248 acquisition sequence 250, 260, 262, 268, 280 Region of acquisition sequence 248 254 Instructions to the device 256 Irradiation preparation instructions 266 Ready signal 282 Acquisition sequence 288 How to sample data from a detector