Radiodiagnostic apparatus

Abstract

To improve image quality.SOLUTION: A radiodiagnostic apparatus comprises: a radiation detector with a plurality of pixels; an anti-scatter grid disposed on an incident side of the radiation detector; and a processing circuit for performing processing based on a detection result from the pixels. The plurality of pixels includes a first pixel disposed at a position facing the anti-scatter grid, and a second pixel disposed at a position not facing the anti-scatter grid. The processing circuit obtains a first detection result from the first pixel and a second detection result from the second pixel to calculate a deviation amount of the anti-scatter grid facing the first pixel, on the basis of the first detection result and the second detection result.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] The embodiments disclosed in the specification and drawings relate to a radiological diagnostic device.

[0002] The present disclosure relates to a radiological diagnostic device for use in a photon-counting computed tomography system. [Background technology]

[0003] In a typical scintillator detector-based computed tomography (CT) imaging system, an X-ray tube emits a fixed number of photons during irradiation of the object, and a detector array on the other side of the object measures the transmitted photons, which are normalized to an air scan with the same scan setup without the object to estimate the path length attenuation. Therefore, since the air scan and the object scan are performed at different times, it is necessary to calibrate the fluctuations of the incident X-ray beam in the time domain for accurate measurements that lead to good image quality.

[0004] However, apart from the change in X-ray tube flux, some X-ray tube types may also experience drift in the X-ray source position over time due to internal electrical steering changes and thermal expansion of the anode, as well as other design tolerances. Such position variations usually cause random anti-scatter-grid (ASG) shadow profile changes on individual detector pixels, which sometimes change the measured intensity. Such X-ray source position variations combined with non-ideal ASG angle alignment may cause different intensity drifts on detector pixels, resulting in ring artifacts in the reconstructed image. Meanwhile, the ASG may also experience certain deformations due to high-speed rotation, which may cause intensity variations that depend on pixel position and rotation speed.

[0005] For semiconductor (CdTe / CZT) based photon counting CT (PCCT), typical detector array designs usually have a much smaller pixel size compared to conventional CT detectors due to the trade-off between charge sharing and pulse pile-up effects to achieve maximum energy resolution. For example, the pixel pitch is chosen between 250 μm and 500 μm in one dimension compared to a conventional pixel pitch of 1 mm or less. Thus, the pixel area of ​​a conventional detector is usually equivalent to N × N groups of sub-pixels in PCCT, where N can be between 2 and 4. To maintain high dose efficiency, ASG designs usually keep the pixel / spacing the same as the pixel distribution of conventional systems.

[0006] One important application of PCCT is spectral imaging. To achieve good performance, precise X-ray source position and ASG alignment are required to solve the problem of measuring the viability of the detection module of the radiation detector. Current technology does not have the means to physically measure the ASG misalignment or the offset of the X-ray source position. Therefore, new design methods of radiation detectors for monitoring / calibration purposes without external measurement tools are also needed.

[0007] In pixelated photon counting detector (PCD) designs, the ASG plates typically retain the same spacing as in conventional CT designs. In an exemplary embodiment, a 3x3 subpixel scheme is used, with each subpixel being 1 / 3 or less of the conventional detector pixel size. In this design, as discussed above, the shadow of the ASG only affects subpixels 1 and 3 of each group, while the central subpixels are not affected by these effects. Therefore, even with perfect alignment of the ASG plates, the subpixel readout will always have a normalization error across the detector along the direction of x-ray source movement, which is a random correction factor that cannot be solved by existing devices. This results in ring artifacts in high-resolution images that use subpixel level readout for image reconstruction.

[0008] In fact, ASG plates almost always have certain mechanical tolerances for both positional and angular accuracy, so combined readout (e.g. 3x3 summing mode) also suffers from the same problems mentioned above, producing ring artifacts in standard resolution images reconstructed with combined pixel readout, if this effect is significant enough. [Prior art documents] [Non-patent literature]

[0009] [Non-Patent Document 1] Jorgensen at. Al., Evaluation of a photon counting Medipix3RX CZT spectral x-ray detector, Proc. SPIE Int Soc Opt Eng, 2016 Summary of the Invention [Problem to be solved by the invention]

[0010] One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to improve image quality. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problem. Problems corresponding to the effects of each configuration shown in the embodiments described later can also be positioned as other problems. [Means for solving the problem]

[0011] A radiological diagnostic apparatus according to an embodiment includes a radiation detector including a plurality of pixels, an anti-scatter grid arranged on the incident side of the radiation detector, and a processing circuit that executes processing based on detection results of the pixels. The plurality of pixels include a first pixel arranged at a position facing the anti-scatter grid, and a second pixel arranged at a position not facing the anti-scatter grid. The processing circuit obtains a first detection result from the first pixel, obtains a second detection result from the second pixel, and calculates an amount of deviation of the anti-scatter grid facing the first pixel based on the first detection result and the second detection result. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram of a radiation detector design including multiple microchannels according to an embodiment, showing an ASG mounted on multiple pixels. [Diagram 2] FIG. 2 is a diagram illustrating a design of a radiation detector including a two-dimensional array of multiple Detector Module Blades (DMBs) according to an embodiment. [Figure 3A] FIG. 3A is a diagram showing four examples of misalignment of a CZT submodule according to an embodiment. [Figure 3B] FIG. 3B is a diagram illustrating an example of misalignment of an ASG with respect to a radiation detector design according to an embodiment. [Figure 4]FIG. 4 is a schematic diagram showing ray tracing of an X-ray photon generated by an X-ray source facing a radiation detector according to an embodiment, where the ray tracing of the X-ray photon shows multiple shadows cast by the ASG on multiple pixels. [Diagram 5] FIG. 5 is a flowchart of a method for determining an ASG offset according to an embodiment. [Figure 6A] FIG. 6A is a diagram showing an example of ASG misalignment according to the embodiment. [Figure 6B] FIG. 6B is a diagram showing an example of ASG misalignment according to the embodiment. [Figure 6C] FIG. 6C is a diagram illustrating an example of ASG misalignment according to the embodiment. [Figure 6D] FIG. 6D is a diagram illustrating an example of ASG misalignment according to the embodiment. [Figure 6E] FIG. 6E is a diagram illustrating an example of ASG misalignment according to the embodiment. [Figure 6F] FIG. 6F is a diagram showing an example of ASG misalignment according to the embodiment. [Figure 7A] FIG. 7A is a schematic diagram of misalignment of an X-ray source facing a radiation detector according to an embodiment. [Figure 7B] FIG. 7B is a schematic diagram of misalignment of an X-ray source facing a radiation detector including an ASG according to an embodiment. [Figure 8] FIG. 8 is a flowchart of a method for determining the tilt angle of an X-ray source according to an embodiment. [Figure 9A] FIG. 9A is a diagram showing plots of multiple right ASG offsets and multiple left ASG offsets for positive and negative tilt angles of an X-ray source according to an embodiment. [Figure 9B] FIG. 9B illustrates a predicted tilt vs. offset table generated for a positive rotation corresponding to an ASG offset right according to an embodiment. [Figure 9C] FIG. 9C illustrates a predicted tilt vs. offset table generated for a reverse rotation corresponding to an ASG offset left, according to an embodiment. [Figure 9D] FIG. 9D illustrates an example of determining a tilt angle based on a calculated offset according to an embodiment. [Figure 9E] FIG. 9E illustrates an example of determining a tilt angle based on a calculated offset according to an embodiment. [Figure 9F] FIG. 9F illustrates an example of determining a tilt angle based on a calculated offset according to an embodiment. [Figure 10A] FIG. 10A is a diagram showing the shape of the partition walls of the ASG with respect to the inclination of the focal point according to the embodiment. [Figure 10B] FIG. 10B is a diagram showing the shape of the partition walls of the ASG with respect to the inclination of the focal point according to the embodiment. [Figure 10C] FIG. 10C illustrates an example shape for ASG offset calculation according to an embodiment. [Figure 11] FIG. 11 is a block diagram showing an example of the configuration of an X-ray CT apparatus according to the embodiment. [Figure 12] FIG. 12 illustrates an exemplary computer system configured to implement methods according to embodiments. [Figure 13] FIG. 13 illustrates another exemplary computer system configured to implement methods according to embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] In one exemplary embodiment, an apparatus is provided that includes: (1) a radiation detector including a plurality of pixels; (2) an anti-scatter grid (ASG) disposed on an incident side of the radiation detector, where, as viewed from the incident side of the radiation detector, partitions of the ASG are disposed over a portion of a first pixel of the plurality of pixels but not over any portion of a second pixel of the plurality of pixels; and (3) a processing circuit configured to receive a first detection result from the first pixel, receive a second detection result from the second pixel, and estimate a position offset (amount of deviation) of the partitions of the ASG based on the first detection result and the second detection result.

[0014] In another exemplary embodiment, an apparatus for detecting alignment misalignment of an anti-scatter grid (ASG) offset detection for a radiation detector device is provided, the apparatus comprising: (1) a radiation detector including a plurality of pixels, the plurality of pixels being arranged in a plurality of modules; and (2) a processing circuit configured to: acquire a first count obtained from a first air scan with an anti-scatter grid (ASG) having a plurality of partitions arranged on an entrance side of the radiation detector; acquire a second count obtained from a second air scan without an ASG arranged on the radiation detector; calculate a third count based on the second count by normalizing the first count; estimate a position offset (misalignment amount) of the plurality of partitions of the ASG based on the calculated third count; and determine whether a particular module of the plurality of modules is faulty based on the estimated position offset of the plurality of partitions.

[0015] In another exemplary embodiment, an apparatus for detecting a tilt angle of an x-ray source includes: (1) a radiation detector including a plurality of pixels, the plurality of pixels being arranged in a plurality of channels; (2) an anti-scatter grid (ASG) arranged on an entrance side of the radiation detector, wherein, as viewed from the entrance side of the radiation detector, for each channel of the plurality of channels, a first partition of the ASG is arranged over a portion of a first pixel of the channel but not over any portion of a second pixel of the channel adjacent to the first pixel, and a second partition of the ASG is arranged over a portion of a third pixel of the channel adjacent to the second pixel but not over any portion of the second pixel, the first, second, and third pixels forming a channel; and (3) for each channel of the plurality of channels, a first partition of the ASG is arranged over a portion of a first pixel of the channel but not over any portion of a second pixel of the channel adjacent to the first pixel, the second partition of the ASG being arranged over a portion of a third pixel of the channel adjacent to the second pixel, but not over any portion of the second pixel, the first, second, and third pixels forming a channel. and a processing circuit configured to: acquire a first detection result from the pixel, a second detection result from the second pixel, and a third detection result from the third pixel, the detection results being obtained from an air scan by an ASG using a radiation source; estimate a right offset (amount of deviation in a first direction) of the first partition based on the first detection result and the second detection result; estimate a left offset (amount of deviation in a second direction) of the second partition based on the third detection result and the second detection result; generate an average right offset (average deviation in the first direction) by averaging the estimated right offsets across each of the channels; generate an average left offset (average deviation in the second direction) by averaging the estimated left offsets across each of the multiple channels; and determine a tilt angle of the X-ray source based on the generated average right offset and the generated average left offset.

[0016] The present application will be better understood in the light of the description given in a non-limiting manner accompanied by the attached drawings, in which:

[0017] References throughout this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, material, or characteristic described in connection with an embodiment is included in at least one embodiment of the application, but do not mean that it is present in all embodiments.

[0018] Thus, the appearances of phrases such as "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment of the present application. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments.

[0019] Aspects of the present embodiment are directed to a radiation detector design for identifying ASG offset and X-ray source misalignment. The radiation detector design includes a radiation detector facing an X-ray source, which in one embodiment is comprised of a two-dimensional array of 38 DMB modules. A simulated offset was generated and compared to an average offset calculated by a method of radiation detector design corresponding to tilt angles in one embodiment.

[0020] 1 shows an exemplary embodiment of a radiation detector, in which an X-ray source is opposed by a curved detector surface, the detector surface including a plurality of macro-channels. According to one embodiment, each macro-channel is composed of three micro-channels, where an anti-scatter grid (ASG) 600 partition is disposed at the right and left ends of each of the plurality of macro-channels. According to one example, each of the micro-channels has an equal pixel width.

[0021] The X-ray source emits photons, and the microchannels are configured to absorb the emitted photons and convert the photons into an electrical signal. The photons travel along straight lines such that the partitions of the ASG600 can cast shadows (e.g., left shadow and right shadow) on adjacent microchannels, and the shadows cast by the partitions reduce photon absorption by the detector.

[0022] 2 illustrates a radiation detector including multiple DMBs. In one embodiment, the radiation detector includes 38 DMBs, each having a detector pixel facing the x-ray source. In one aspect, each of the DMBs can be further subdivided into four CZT submodules. Each of the CZT submodules can include, for example, a 36×24 array of micropixels, according to one embodiment.

[0023] In one embodiment, each row-wise micropixel of the DMB is referred to as a micro-row, and each column-wise micropixel of the DMB is referred to as a micro-channel. In one exemplary embodiment, the ASGs are arranged bisecting every third micro-channel. In this arrangement, the ASG partitions do not cast shadows on the central micro-pixels, and filter scattered X-ray photons emitted by the X-ray source, improving image quality and avoiding image-degrading problems such as ring artifacts.

[0024] In another embodiment, each of the DMBs includes an array of 12 CZT submodules arranged in a 2 x 6 grid pattern, with an ASG located at every third micropixel of each of the CZTs. In this embodiment, each partition of the ASG includes lead strips separated by low attenuation spacing material, such as carbon fiber or aluminum, that run along between every third micropixel.

[0025] FIG. 3A shows one embodiment of DMB misalignment. DMB misalignment can include rotation of the CZT submodule due to misalignment of the CZT submodule during installation. In another embodiment, CZT submodule misalignment can be due to deformation due to fast rotation of the device, causing position and rotation speed dependent intensity variations across the pixel. In another embodiment, the CZT submodules are positioned in a 2D lattice on the substrate, and the micropixels have photoelectric conversion units arranged on the scintillator.

[0026] 3B shows an example of an ASG misalignment occurring on a curved surface of a radiation detector, where an X-ray source facing the ASG emits X-ray photons in a straight line. In this example, the dashed lines represent the ideal positions of each septum of the ASG, and the offset of the ASG septum can include a left septum rotation, a right septum rotation, or a septum translation (or a combination thereof).

[0027] While some degree of ASG misalignment is tolerable in most PCCT systems, ASG misalignment that exceeds the mechanical tolerances of the PCCT system can lead to degradation of the final generated image. The present disclosure addresses the limitation of physically measuring the misalignment of both the detector elements and the ASG through a methodology described below with respect to FIGS.

[0028] Figure 4 shows an example of an ASG misalignment, where the ASG casts a shadow on some of the micropixels in a three-micropixel channel. Assuming both the ASG and the micropixels are accurately positioned and aligned, the shadow of the ASG will be consistent at all ASG septum locations and corresponding micropixels. During an air scan, the count measured for a particular micropixel is directly proportional to the unshadowed area of ​​that micropixel. As shown in Figure 4, the center microchannel of the channel has both no septum and no shadow, resulting in a full count.

[0029] However, if there is any alignment misalignment between the ASG and the micropixel, the counts and shadow lengths of the left and right micropixels of the channel will deviate from the ideal scenario, as shown in Figure 4. Based on the counts of each micropixel, the ASG partition width, and the micropixel width, the following equations (1) to (4) are used to calculate the left and right shadow lengths and the corresponding left and right ASG offsets (misalignment amounts).

[0030]

number

[0031]

number

[0032]

number

[0033]

number

[0034] Here, W p is the micropixel width, N R,ch is the air count of the right microchannel of the channel, N L,ch is the air count of the left microchannel of the channel, N C,ch is the air count of the central microchannel of the channel, ch is the channel identifier, W ASG is the bulkhead width of the ASG.

[0035] According to one embodiment, using equations (1) and (2), the processing circuitry determines the air count and W measured for the microchannel. p Based on the amount of shadow of the right and left microchannels of a given channel (shadow R ch and Shadow L ch Then, using equations (3) and (4), the processing circuitry is configured to calculate the calculated left and right shadow amounts and the corresponding ASG bulkhead widths W ASG The apparatus is configured to calculate left and right ASG offsets based on:

[0036] FIG. 5 shows a flowchart of a method using the calculations of equations (1) to (4).

[0037] In step 520, an air scan is performed using the ASG to obtain a first air scan count in each microchannel.

[0038] In step 530, an air scan is performed without the ASG to obtain a second air scan count in each microchannel.

[0039] In step 540, the second air scan count is divided by the corresponding pixel width to account for pixels of different sizes.

[0040] In step 550, the first air scan count is normalized by the second air scan count to obtain, for example, the value N R,ch , N L,ch , N C,ch get.

[0041] In step 560, the left and right offsets of the ASG septum for each channel are calculated using equations (3) and (4) above.

[0042] In step 570, the calculated offset data for each channel may be evaluated and displayed to determine, for example, whether a particular DMB module is faulty, as shown in Figures 6A-6F, described below.

[0043] Figures 6A and 6B show examples of average right and left offsets, respectively, for a system containing 16 sub-modules per DMB. The average offset value for each sub-module for a given DMB is plotted. If the average offset is within plus or minus 50 micrometers, it is considered acceptable. However, if a particular DMB displays a significantly larger offset that is outside the prescribed tolerance of the radiation detector system, it is an indication that the DMB is defective and needs to be replaced.

[0044] The average ASG offset results can be plotted as a histogram for each DMB according to another embodiment, as shown in Figure 6C, where the histograms for DMBs 11 and 13 are anomalous, indicating that the quality of the DMBs should be further investigated.

[0045] Figures 6D and 6E show the offset plotted in 3D format for each submodule of the DMB. The four plots in Figure 6D show four submodules in a good DMB, where the surface of the submodule is relatively flat and uniform, and the offset value is low. The bad DMB plots are shown in the four plots in Figure 6E, where the surface is irregular and discontinuous, and the offset value is high.

[0046] FIG. 6F shows many possible types of ASG misalignment and corresponding offset profiles. To determine the rotational and translational misalignment of the ASG offset, the offset can be plotted along the micro-row (micro-segment) direction for a particular sub-module. The plot in FIG. 6F shows various offset patterns for normal, left-right translation, and up-down rotational ASG placement.

[0047] In a second embodiment, as shown in FIG. 7A, the X-ray source of the PCCT system can be tilted by a source tilt angle ρ with respect to the isocenter at a distance STD, and this X-ray source offset can cause shadows to be cast by the ASG on the radiation detector. These shadows can affect the quality of the images generated by the radiation detector. As shown in FIG. 10A, the tilt of the X-ray source is, in one embodiment, the coordinate x S = STD·(1-cos(ρ)) and y S = STD sin(ρ), x S is the x coordinate of the X-ray source position in 2D space, and y S is the y coordinate of the position of the x-ray source in 2D space, and STD is the distance from the isocenter to the position of the x-ray source.

[0048] FIG. 7B shows the tilt of the X-ray source of FIG. 7A within the range of the ASG installed on the radiation detector of this embodiment. As with the embodiment described above with respect to FIG. 1 and FIG. 4, the PCCT imaging system of this embodiment uses ASG partitions placed between every third microchannel placed on the radiation detector. When there is no tilt of the X-ray source (ρ=0), the ASG partitions cast shadows of lengths L(0) and R(0) on the left and right micropixels on the detector, respectively. However, when the X-ray source is tilted by ρ, the shadow lengths (shadow L(ρ) and shadow R(ρ)) change with ρ. These shadow lengths can be calculated from the air count of the micropixels from the air scan and are directly proportional to the air count from the air scan. Using the above-mentioned equations (1) to (4), the shadow L(ρ), the shadow R(ρ), the left ASG offset, and the right ASG offset can be calculated.

[0049] In one embodiment, pre-calculated values ​​of the left ASG offset and the right ASG offset of an ideal PCCT imaging system are calculated by simulation for a range of corresponding input ρ values. Thus, a look-up table is generated and can be used to look up the value of ρ when the measured left ASG offset and the measured right ASG offset are provided. This approach provides a solution for identifying the tilt angle ρ via the values ​​of the left ASG offset and the right ASG offset, providing a useful tool for PCCT imaging.

[0050] 8 is a flow chart of a method for calculating the source tilt angle according to the present embodiment. As described above, a look-up table (or multiple tables depending on the sign of the tilt angle, as described below) relating the input average ASG offset and the output tilt angle ρ is pre-calculated by simulation.

[0051] In step 580, an air scan is performed with the ASG at the predetermined locations to obtain air scan counts in each microchannel, as described above.

[0052] In step 581, the left and right offsets are calculated using equations (1)-(4), as described above.

[0053] In step 582, the average right offset and the average left offset are calculated for each channel.

[0054] In step 583, the sign of the tilt (positive or negative) is determined based on the average right and left offset. In one embodiment, the sign of the tilt (positive or negative) is determined by first comparing the left and right offset graphs across all channels with the corresponding graphs shown in FIG. 9A. In particular, as shown in FIG. 9A, the shapes of the left and right offset graphs are different depending on whether the tilt is positive or negative. For a positive tilt angle, the right ASG offset is much larger than the left ASG offset. For a negative tilt angle, the opposite is true, and the right ASG offset is much smaller than the left ASG offset.

[0055] In step 584, a predefined lookup table is used to determine the value of the tilt angle. Alternatively, a single combined lookup table or other database structure may be used. In the case of a positive tilt angle determined in step 583, i.e., the average ASG right offset is greater than the average ASG left offset, the average ASG right offset table is used, e.g., as shown in FIG. 9B. In the case of a negative tilt angle determined in step 583, i.e., the average ASG right offset is less than the average ASG left offset, the average ASG left offset table is used, e.g., as shown in FIG. 9C.

[0056] In one embodiment, Figures 9D and 9E show the ASG offset data for two data sets R3 and R2. R3 was estimated (not exactly known) ρ=0.00°, and R2 was ρ=0.15°. The shape of the actual ASG offset is very noisy due to other factors such as misalignment of the individual detector CZT micropixels. However, the table is useful because it is the average ASG offset, not the shape, that is primarily affected by the tilt. For example, the measured average ASG offset for R3 was 2.77, and for R2 was 62.76. Thus, from the table, as shown, R3 was calculated to have ρ=0.00°, and R2 was calculated to have ρ=0.13°.

[0057] 10A shows a geometric example of a single ASG septum disposed on the radiation detector of FIG 1 with a tilted focal spot in an embodiment where the ASG septum is fixed to the boundary between the microchannels of FIG 1, where the coordinates of the septum at the detector center are given by the following equations in equation (5):

[0058]

number

[0059] 10B shows a geometric example of the location of the partitions in one embodiment, where the coordinates of the ASG partitions shown in FIG.

[0060]

number

[0061] Here, the parameters in equation (6) are given as the equations contained in equation (7) below.

[0062]

number

[0063] 10C shows a geometric example for performing the ASG offset calculation according to one embodiment. For example, the left offset and the right offset are given as in the following equation (8):

[0064]

number

[0065] Here, each parameter in equation (8) is given as each equation contained in equation (9) below.

[0066]

number

[0067] Furthermore, the intersection points and angles of the rays of the front septa with the detector are given by the equations contained in equation (10) below.

[0068]

number

[0069] The equations for the X-ray source-septa corner array are given as the equations contained in equation (11) below.

[0070]

number

[0071] FIG. 11 shows an embodiment of an X-ray imaging gantry included in an X-ray CT device or scanner. As shown in FIG. 11, the X-ray imaging gantry 500 is shown from a side view and further includes an X-ray tube 501, an annular frame 502, and a multi-row or two-dimensional array type X-ray detector 503. The X-ray tube 501 and the X-ray detector 503 are mounted radially across an object OBJ on the annular frame 502 that is rotatably supported about a rotation axis RA. A rotation unit 507 rotates the annular frame 502 at a high speed, such as 0.4 seconds / revolution, while the object OBJ moves along the axis RA toward or away from the illustrated page.

[0072] The X-ray computed tomography (CT) apparatus according to the present embodiment will be described below with reference to the accompanying drawings. It should be noted that the X-ray CT apparatus includes various types of apparatus, such as a rotating / rotating type apparatus in which an X-ray tube and an X-ray detector rotate together around an object to be inspected, and a fixed / rotating type apparatus in which many detector elements are arranged in a ring or plane and only the X-ray tube rotates around an object to be inspected. This embodiment can be applied to either type. Here, the rotating / rotating type, which is currently mainstream, is exemplified.

[0073] The multi-slice X-ray CT apparatus further includes a high-voltage generator 509. The high-voltage generator 509 generates a tube voltage that is applied to the X-ray tube 501 through a slip ring 508 so that the X-ray tube 501 generates X-rays. The X-rays are emitted toward the object OBJ, whose cross-sectional area is represented by a circle. For example, the X-ray tube 501 has an average X-ray energy during a first scan that is smaller than an average X-ray energy during a second scan. Thus, two or more scans corresponding to different X-ray energies can be obtained. The X-ray detector 503 is disposed on the opposite side of the X-ray tube 501 across the object OBJ to detect the irradiated X-rays propagating through the object OBJ. The X-ray detector 503 further includes individual detection elements or units.

[0074] The X-ray CT apparatus further includes other devices for processing detection signals from the X-ray detector 503. A data acquisition circuit or data acquisition system (DAS) 504 converts the signal output from the X-ray detector 503 of each channel into a voltage signal, amplifies the signal, and further converts the signal into a digital signal. The X-ray detector 503 and the DAS 504 are configured to process a predetermined total number of projections per rotation (TPPR).

[0075] The above mentioned data is sent via a non-contact data transmitter 505 to a pre-processing device 506 housed in a console outside the X-ray imaging gantry 500. The pre-processing device 506 performs certain corrections on the raw data, such as sensitivity correction. A storage device 512 stores the result data, also called projection data, at a stage just before the reconstruction process. The storage device 512 is connected to a system controller 510 via a data / control bus 511 together with a reconstruction device 514, an input device 515, and a display 516. The system controller 510 controls a current regulator 513 that limits the current to a level sufficient to drive the CT system.

[0076] The detectors are rotated and / or fixed relative to the patient in various generations of CT scanner systems. In one embodiment, the CT system described above may be an example of a combination of third and fourth generation geometry systems. In a third generation system, the X-ray tube 501 and the X-ray detector 503 are radially mounted on an annular frame 502 that rotates around the object OBJ by rotating about the rotation axis RA. In a fourth generation geometry system, the detectors are fixedly mounted around the patient and the X-ray tube rotates around the patient. In an alternative embodiment, the X-ray imaging gantry 500 has multiple detectors arranged on an annular frame 502 that is supported by a C-arm and a stand.

[0077] The storage device 512 can store measurements indicative of the irradiance of X-rays at the X-ray detector 503. Additionally, the storage device 512 can store dedicated programs for performing the various steps of the methods described herein.

[0078] The reconstruction device 514 may perform various steps of the methods described herein, and may further perform pre-reconstruction image processing, such as volume rendering and image differencing, as necessary.

[0079] The reconstruction processing of the projection data performed by the pre-processing device 506 may include, for example, detector calibration, detector non-linearity, and correction for polar effects. Furthermore, the reconstruction pre-processing may include various steps of the methods described herein.

[0080] Post-reconstruction processing performed by the reconstruction device 514 may include image filtering and smoothing, volume rendering processing, and image subtraction processing, as necessary. The image reconstruction process may implement various CT image reconstruction methods as well as various steps of the methods described herein. The reconstruction device 514 may use memory to store, for example, projection data, reconstructed images, calibration data and parameters, and computer programs.

[0081] The reconfiguration device 514 may include a CPU (processing circuitry) that may be implemented as discrete logic gates, as an Application Specific Integrated Circuit (ASIC), Field Programmable Gate Array (FPGA), or other Complex Programmable Logic Device (CPLD). The implementation of an FPGA or CPLD may be coded in VHDL, Verilog, or other hardware description language, and the code may be stored directly in electronic memory within the FPGA or CPLD or may be stored as a separate electronic memory. Furthermore, the storage device 512 may be non-volatile, such as ROM, EPROM, EEPROM, or flash memory. The storage device 512 may be volatile, such as static or dynamic RAM, and a processor, such as a microcontroller or microprocessor, may be provided to manage the electronic memory as well as the interaction between the FPGA or CPLD and the memory.

[0082] Alternatively, the CPU in the reconstruction device 514 may execute a computer program including a set of computer readable instructions to perform the functions described herein, the program being stored in any of the non-transitory electronic memories and / or hard disk drives, CDs, DVDs, flash drives, or any other known storage mediums mentioned above. Furthermore, the computer readable instructions may be provided as a utility application, background daemon, or operating system component, or combination thereof, running with a processor such as an Intel Xenon processor or an AMD Opteron processor, and an operating system such as Microsoft VISTA, UNIX, Solaris, LINUX, Apple, MAC-OS, and other operating systems known to those skilled in the art. Furthermore, the CPU may be implemented as multiple processors operating cooperatively in parallel to execute instructions.

[0083] In one embodiment, the reconstructed image may be displayed on a display 516. The display 516 may be an LCD display, a CRT display, a plasma display, an OLED, an LED, or any other display known in the art.

[0084] The storage device 512 may be a hard disk drive, a CD-ROM drive, a DVD drive, a flash drive, RAM, ROM, or any other electronic storage device known in the art.

[0085] The radiation detector device data and functional operation embodiments described herein can be implemented by digital electronic circuitry, in tangibly embodied computer software or firmware, computer hardware including the structures disclosed herein and their structural equivalents, or one or more combinations thereof. The subject matter described herein can be implemented as one or more computer programs, i.e., one or more modules of computer program instructions encoded on a tangible non-transitory program carrier for execution by or for controlling the operation of a data processing device, such as a networked device or server, a user device, etc. The computer storage medium can be a machine-readable storage device, a machine-readable storage substrate, a random or serial access memory device, or one or more combinations thereof.

[0086] The term "data processing apparatus" refers to data processing hardware and may encompass any type of apparatus, device, and machine for processing data, including, by way of example, a programmable processor, a computer, or multiple processors or computers. An apparatus may also be or further include special purpose logic circuitry, such as an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit). In addition to hardware, an apparatus may optionally include code that establishes an execution environment for a computer program, such as code that constitutes a processor firmware, a protocol stack, a database management system, an operating system, or one or more combinations thereof.

[0087] A computer program may also be referred to or written as a program, software, software application, module, software module, script, or code, and may be written in any form of programming language, including compiled or interpreted languages, or declarative or procedural languages, and may be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program may correspond to a file in a file system, but need not correspond to one. A program may be stored in a portion of a file that holds other programs or data, e.g., one or more scripts stored in a markup language document, in a single file dedicated to the program in question, or in multiple cooperating files, e.g., files that store one or more modules, subprograms, or portions of code. A computer program may be deployed to run on one computer, or to run on multiple computers located at one site or distributed across multiple sites and interconnected by a data communications network.

[0088] According to embodiments, the processes and logic flows described herein may be executed by one or more programmable computers executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows may also be executed by, and apparatus may be so implemented as, special purpose logic circuitry, such as, for example, an FPGA or ASIC.

[0089] Computers suitable for executing computer programs include, by way of example, general-purpose or special-purpose microprocessors, or both, or any other type of central processing unit. Typically, a CPU receives instructions and data from a read-only memory or a random access memory, or both. The components of a computer are a CPU for performing or executing instructions, and one or more memory devices for storing instructions and data. Typically, a computer includes one or more mass storage devices, such as magnetic disks, magneto-optical disks, or optical disks, for storing data, or is operatively coupled to receive data from or transfer data to the mass storage devices, or both. However, a computer need not have such devices. Furthermore, a computer can be incorporated into other devices, such as a mobile phone, a Personal Digital Assistant (PDA), a portable audio or video player, a game console, a Global Positioning System (GPS) receiver, or a portable storage device, such as a Universal Serial Bus (USB) flash drive, and the like. Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media and memory devices, including, by way of example, semiconductor memory devices such as EPROM, EEPROM and flash memory devices, internal hard disks or removable disks, magneto-optical disks and magnetic disks such as CD-ROM and DVD-ROM disks. The processor and memory may be supplemented by, or incorporated in, special purpose logic circuitry.

[0090] To provide for user interaction, embodiments of the subject matter described herein can be implemented on a computer having a display device, such as a CRT (cathode ray tube) or LCD (liquid crystal display) monitor, for displaying information to the user, and a keyboard and pointing device, such as a mouse or trackball, by which the user can provide input to the computer. Other types of devices can also be used to provide user interaction, e.g., feedback provided to the user can be any form of sensory feedback, such as visual feedback, auditory feedback, or tactile feedback, and input from the user can be received in any form, such as acoustic input, speech input, or tactile input. Additionally, the computer can interact with the user by sending documents to and receiving documents from a device used by the user, e.g., sending a web page to a web browser on the user's device in response to a request received from the web browser.

[0091] In another embodiment, the subject matter described herein can be implemented in a computing system, which includes a back-end component, e.g., a data server, or includes a middleware component, such as an application server, or includes a front-end component, such as a client computer with a graphical user interface, or a web browser through which a user can interact with an implementation of the subject matter described herein, or any combination of one or more of such back-end, middleware, or front-end components. The components of the system can be interconnected by any form or medium of digital data communication, e.g., a communication network. Examples of communication networks include a Local Area Network (LAN) and a Wide Area Network (WAN), e.g., the Internet.

[0092] FIG. 12 shows a hardware diagram of a device 1201 according to an exemplary embodiment. In FIG. 12, the device 1201, which may be any of the devices mentioned above, including a server and a user device, includes a processing circuit. The processing circuit includes one or more of the elements described below with reference to FIG. 12. Data and instructions of the process may be stored in a memory 1202. These processes and instructions may be stored in a storage medium disk 1204, such as a hard drive (HDD) or a portable storage medium, or may be stored in a remote location. Furthermore, the claimed advancement is not limited by the form of the computer-readable medium on which the instructions of the inventive process are stored. For example, the instructions may be stored in a CD, DVD, flash memory, RAM, ROM, PROM, EPROM, EEPROM, hard disk, or other information processing device with which the device 1201 communicates, such as a server or computer.

[0093] Further, the claimed advancements may be provided as a utility application, background daemon, or operating system component, or combination thereof, and execute in cooperation with CPU 1200 and an operating system, such as Microsoft Windows®, UNIX®, Solaris, LINUX, Apple MAC-OS, and other systems known to those skilled in the art.

[0094] The hardware elements for implementing device 1201 may be implemented by various circuit elements known to those skilled in the art. For example, CPU 1200 may be an Intel Xenon or Core processor, or an AMD Opteron processor, or other processor types recognized by those skilled in the art. Alternatively, CPU 1200 may be implemented using FPGA, ASIC, PLD, or discrete logic circuitry, as recognized by those skilled in the art. Furthermore, CPU 1200 may be implemented as multiple processors cooperating in parallel to execute instructions of the processes described above.

[0095] The device 1201 of FIG. 12 also includes a network controller 1206, such as an Intel Ethernet PRO network interface card from Intel Corporation, USA, for interfacing with a network 1250 and communicating with other devices. As can be appreciated, the network 1250 can be a public network, such as the Internet, a private network, such as a LAN or WAN network, or any combination thereof, and can include a PSTN or ISDN sub-network. The network 1250 can be wired, such as an Ethernet network, or wireless, such as a cellular network, including EDGE, 3G, 4G, and 5G wireless cellular systems. The wireless network can be WiFi, Bluetooth, or any other known form of wireless communication.

[0096] The device 1201 further includes a display controller 1208, such as an NVIDIA GeForce GTX or Quadro graphics adapter from NVIDIA Corporation, USA, for interfacing with a display 1210, such as an LCD monitor. A general purpose I / O interface 1212 interfaces with a keyboard and / or mouse 1214, and a touch screen panel 1216 on or separate from the display 1210. The general purpose I / O interface also connects to a variety of peripherals 1218, including printers and scanners.

[0097] A generic storage controller 1224 connects the storage media disk 1204 to a communication bus 1226, which may be ISA, EISA, VESA, PCI, or the like, for interconnecting all components of the device 1201. A description of the general features and functionality of the display 1210, keyboard and / or mouse 1214, as well as the display controller 1208, storage controller 1224, network controller 1206, sound controller 1220, and generic I / O interface 1212 is omitted herein for the sake of brevity, as these features are known.

[0098] FIG. 13 illustrates an example of a type of computer. The computer 1300, according to one embodiment, can be used for the operations described in connection with any of the computer-implemented methods described above. For example, the computer 1300 can be an example of a network device, such as a server, that includes a processing circuit, as described herein. The processing circuit includes one or more of the elements described below with reference to FIG. 13. In FIG. 13, the computer 1300 includes a processor 1310, a memory 1320, a storage device 1330, and an input / output device 1340. Each of the components 1310, 1320, 1330, and 1340 are interconnected using a system bus 1350. The processor 1310 can process instructions for execution within the system 1300. In one embodiment, the processor 1310 is a single-threaded processor. In another embodiment, the processor 1310 is a multi-threaded processor. The processor 1310 can process instructions stored in the memory 1320 or the storage device 1330 to display graphical information of a user interface on the input / output device 1340.

[0099] The memory 1320 stores information within the computer 1300. In one embodiment, the memory 1320 is a computer-readable medium. In one embodiment, the memory 1320 is a volatile memory unit. In another embodiment, the memory 1320 is a non-volatile memory unit.

[0100] The storage device 1330 is capable of providing mass storage to the computer 1300. In one embodiment, the storage device 1330 is a computer-readable medium. In various different implementations, the storage device 1330 may be a floppy disk device, a hard disk device, an optical disk device, or a tape device.

[0101] The input / output devices 1340 provide input / output operations to the computer 1300. In one embodiment, the input / output devices 1340 include a keyboard and / or a pointing device. In another embodiment, the input / output devices 1340 include a display unit for displaying a graphical user interface.

[0102] Although many specific implementation details are set forth in this specification, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments.

[0103] Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in a particular combination, and even initially claimed as such, in some instances one or more features of a claimed combination can be deleted from the combination. A claimed combination can also be directed to subcombinations or variations of subcombinations.

[0104] Similarly, in the figures, operations are depicted in a particular order, but this should not be understood as requiring the particular order depicted, or sequential order, or that all of the depicted operations be performed, to achieve desirable results. In certain situations, multitasking and parallel processing may be advantageous. Moreover, the separation of various system modules and components in the above-described embodiments should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems may generally be integrated together into a single software product or packaged into multiple software products.

[0105] According to at least one of the embodiments described above, image quality can be improved.

[0106] Specific embodiments of the subject matter have been described. Other embodiments are within the scope of the claims of the present invention. For example, the actions recited in the claims can be performed in a different order and still achieve desirable results. By way of example, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some cases, multitasking and parallel processing may be advantageous. It is apparent that numerous modifications and variations of the embodiments presented herein are possible in light of the above teachings. It is therefore to be understood that within the scope of the claims, the present disclosure may be practiced in ways other than as specifically described herein. [Explanation of symbols]

[0107] 501 X-ray tube 503 X-ray detector 514 Reconstruction Device 600 Anti-scatter grid

Claims

1. a radiation detector including a plurality of pixels; an anti-scatter grid disposed on the incident side of the radiation detector; a processing circuit for performing processing based on the detection result of the pixel; Equipped with the plurality of pixels include a first pixel disposed at a position facing the anti-scatter grid and a second pixel disposed at a position not facing the anti-scatter grid, The processing circuitry includes: Obtaining a first detection result from the first pixel; Obtaining a second detection result from the second pixel; a radiation diagnostic apparatus that calculates an amount of deviation of the anti-scatter grid facing the first pixel based on the first detection result and the second detection result.

2. 2. The radiation diagnostic apparatus according to claim 1, wherein the processing circuitry estimates a length of a shadow cast by the anti-scatter grid facing the first pixel based on the first detection result and the second detection result, and calculates a deviation amount of the anti-scatter grid based on the length of the shadow.

3. 3. The radiological diagnostic apparatus of claim 2, wherein the processing circuitry estimates a length of the shadow based on a width of the first pixel, and calculates a displacement of the anti-scatter grid based on a width of the anti-scatter grid.

4. The radiological diagnostic apparatus of claim 1 , wherein the processing circuitry calculates one of an amount of displacement of the anti-scatter grid in a first direction and an amount of displacement of the anti-scatter grid in a second direction different from the first direction.

5. The radiological diagnostic apparatus of claim 1 , wherein the processing circuitry calculates one of an amount of deviation of the anti-scatter grid in a first rotational direction and an amount of deviation in a second rotational direction different from the first rotational direction.

6. The anti-scatter grid has a plurality of partitions which are radiation absorbing members, and a plurality of radiation transparent members which are alternately arranged in a slit or matrix shape, The radiation detector includes a plurality of detector module blades; each of the plurality of detector module blades includes a plurality of sub-modules having a two-dimensional array of pixels arranged in a plurality of rows and a plurality of columns; the plurality of rows of each of the plurality of sub-modules are arranged into three rows of channels, each of the channels including a left micro-channel, a center micro-channel and a right micro-channel; 2. The radiological diagnostic apparatus of claim 1, wherein a first partition of the anti-scatter grid is disposed at a left end of the left micro-channel and a second partition of the anti-scatter grid is disposed at a right end of the right micro-channel.

7. a radiation detector including a plurality of pixels, the plurality of pixels being arranged in a plurality of modules; an anti-scatter grid disposed on the incident side of the radiation detector; a processing circuit for executing a process based on a counting result by the radiation detector; Equipped with The processing circuitry includes: obtaining a first counting result obtained from a first air scan using the anti-scatter grid and a second counting result obtained from a second air scan without the anti-scatter grid; Calculating a third count result by normalizing the first count result based on the second count result; calculating a deviation of the anti-scatter grid based on the third counting result; The radiation diagnostic apparatus determines whether or not any of the plurality of modules is faulty based on the amount of deviation.

8. The radiological diagnostic apparatus of claim 7 , wherein the processing circuitry modifies the second counting result based on a size of the plurality of pixels.

9. 8. The radiological diagnostic apparatus of claim 7, wherein the processing circuitry determines whether or not a particular module among the plurality of modules has failed based on an average displacement calculated for a group of a plurality of partitions of the anti-scatter grid in the particular module.

10. a radiation detector including a plurality of pixels, the plurality of pixels being arranged in a plurality of channels respectively; an anti-scatter grid disposed on the incident side of the radiation detector; a processing circuit for performing processing based on the detection result of the pixel; Equipped with each of the plurality of channels includes a first pixel, a portion of which faces a first partition of the anti-scatter grid; a second pixel adjacent to the first pixel and not facing the partition of the anti-scatter grid; and a third pixel adjacent to the second pixel and a portion of which faces the second partition of the anti-scatter grid; The processing circuitry includes: For each channel of the plurality of channels, obtaining a first detection result from the first pixel, obtaining a second detection result from the second pixel, and obtaining a third detection result from the third pixel by an air scan using the anti-scatter grid; calculating an amount of deviation of the first partition wall in a first direction based on the first detection result and the second detection result; calculating an amount of deviation of the second partition wall in a second direction different from the first direction based on the third detection result and the second detection result; calculating an average shift amount in the first direction by averaging the shift amount in the first direction across the plurality of channels, and calculating an average shift amount in the second direction by averaging the shift amount in the second direction across the plurality of channels; a tilt angle of an X-ray source based on the average displacement amount in the first direction and the average displacement amount in the second direction;

11. The processing circuitry includes: determining whether the tilt angle is positive or negative based on the average deviation amount in the first direction and the average deviation amount in the second direction; Selecting a corresponding lookup table based on whether the tilt angle is positive or negative; The radiological diagnostic apparatus of claim 10 , further comprising: determining a value of the tilt angle based on one of an average displacement in the first direction and an average displacement in the second direction using a selected lookup table.

12. The processing circuitry includes: selecting a lookup table corresponding to the first direction when the average deviation amount in the first direction is greater than the average deviation amount in the second direction; The radiological diagnostic apparatus according to claim 11 , wherein when the average amount of deviation in the first direction is smaller than the average amount of deviation in the second direction, the lookup table corresponding to the second direction is selected.

13. The processing circuitry includes: determining whether the tilt angle is positive or negative when the average deviation amount in the first direction is greater than the average deviation amount in the second direction; The radiation diagnostic apparatus according to claim 11 , wherein the tilt angle is determined to be negative when the average deviation amount in the first direction is smaller than the average deviation amount in the second direction.

14. The processing circuitry includes: Obtaining simulated count data for each tilt angle in the range of positive tilt angles and the range of negative tilt angles; calculating a deviation amount in the first direction and a deviation amount in the second direction for each of the plurality of channels for each tilt angle; Calculating an average deviation amount in the first direction and an average deviation amount in the second direction for each tilt angle; generating a lookup table corresponding to the first direction by associating, for each positive tilt angle, an average deviation in the corresponding first direction; The radiological diagnostic apparatus according to claim 12 , further comprising: a lookup table for generating a lookup table corresponding to the second direction by associating an average deviation amount in the second direction with each negative tilt angle.

15. The radiological diagnostic apparatus of claim 10 , wherein the processing circuitry determines the tilt angle of the x-ray source relative to an isocenter and a centerline of the radiation detector.

16. The processing circuitry includes: estimating a length of a shadow of the first partition on the first pixel based on the first detection result and the second detection result; calculating a shift amount of the first partition wall in the first direction based on a length of a shadow of the first partition wall; estimating a length of a shadow of the second partition on the third pixel based on the third detection result and the second detection result; The radiological diagnostic apparatus according to claim 10 , further comprising: estimating an amount of deviation of the second septum in the second direction based on a length of a shadow of the second septum.

17. The processing circuitry includes: further estimating a length of a shadow of the first partition based on a width of the first pixel, and estimating a shift amount of the first partition in the first direction based on a width of the first partition; 17. The radiological diagnostic apparatus of claim 16, further estimating the length of the shadow of the second septum based on a width of the third pixel, and estimating an amount of deviation of the second septum in the second direction based on a width of the second septum.

Images