Wide-angle automatic irradiation control in tomography

Abstract

The present application discloses a system and method for calculating an automatic exposure control (AEC) calibration dose for tomosynthesis scanning. For example, a reference image can be obtained, and a corresponding reference detector count map can be generated and stored for a plurality of projection angles using a tomosynthesis imaging system. The tomosynthesis imaging system can then obtain a scout image using a scout dose, identify the highest density region within the scout image, and calculate an average detector count value associated with the highest density region. The AEC calibration dose can be calculated based on the ratio of the average reference detector count value of the reference image corresponding to the detector count value of a pixel to the corresponding highest density region, and the calculated average detector count value.

Description

Background Art

[0001] (Cross - reference to related applications) This application is filed on June 30, 2023, as a PCT international patent application claiming the priority and benefit of U.S. Provisional Application No. 63 / 358,350, filed on July 5, 2022, which is incorporated herein by reference in its entirety.

[0002] Breast cancer and other breast lesions continue to be a major threat to women's health. Mammography and tomosynthesis are the most widely used tools for early detection, screening, and diagnosis. Tomosynthesis is a technique that enables a physician to view multiple images of the breast rather than a single image available from a conventional mammogram.

[0003] For example, conventional mammography provides a single two - dimensional (2D) image to a physician for evaluating the breast. However, this can be limited due to overlapping layers of tissue, which can result in unclear results, false positives, or lead a physician to miss a cancerous growth. In contrast, tomosynthesis generates multiple X - ray images of the breast as the X - ray source moves relative to the breast. The X - ray images are then processed into a stack of 2D images representing the entire volume of the breast, which enables a physician to better evaluate the patient's breast.

Summary of the Invention

Means for Solving the Problems

[0004] Examples of the present disclosure are directed to an automatic irradiation control method and system for wide - angle tomosynthesis.

[0005] In a first example, a method for performing an automatic exposure control (AEC) operation using a tomosynthesis system is disclosed. The method includes obtaining a scout image of a patient's breast at a first projection angle by emitting a scout x-ray dose toward the patient's breast using the tomosynthesis system, the scout image including a plurality of pixels, each of the plurality of pixels being associated with a detector count value from among a plurality of detector count values; identifying a first region on the scout image corresponding to a highest density portion of the patient's breast; calculating an average detector count value by averaging one or more detector count values corresponding to one or more pixels within the first region; identifying a second region on a first reference image associated with the first projection angle, the second region corresponding to a location on the first reference image that aligns with a location of the first region on the scout image; obtaining one or more reference detector count values associated with one or more reference pixels within the second region of the first reference image; calculating an average reference detector count value by averaging the one or more reference detector count values; calculating an AEC calibration dose to be used in a tomosynthesis scan based on a ratio between the average reference detector count value and the average detector count value; and setting a radiation dose for a tomosynthesis sweep at a plurality of projection angles in the patient's breast to the AEC calibration dose.

[0006] In a second example, a tomosynthesis system for performing an automatic exposure control (AEC) operation is disclosed. The system includes a processor and a memory containing instructions that, when executed by the processor, cause the tomosynthesis system to obtain a scout image of a patient's breast at a first projection angle by emitting a scout x-ray dose toward the patient's breast, where the scout image includes a plurality of pixels, each of the plurality of pixels being associated with a detector count value from among a plurality of detector count values; identify a first region on the scout image corresponding to the highest density portion of the patient's breast; calculate an average detector count value by averaging one or more detector count values corresponding to one or more pixels within the first region; identify a second region on a first reference image associated with the first projection angle, where the second region corresponds to a location on the first reference image that aligns with the location of the first region on the scout image; obtain one or more reference detector count values associated with one or more reference pixels within the second region of the first reference image; calculate an average reference detector count value by averaging the one or more reference detector count values; calculate an AEC calibration dose to be used in a tomosynthesis scan based on a ratio between the average reference detector count value and the average detector count value; and cause the processor to set a radiation dose for tomosynthesis sweeps at a plurality of projection angles in the patient's breast to the AEC calibration dose.

[0007] In a third example, a method for performing a calibration operation associated with an automatic exposure control (AEC) operation using a tomosynthesis system is disclosed. The method includes obtaining a plurality of reference images of a phantom at a plurality of projection angles, each of the plurality of reference images including a plurality of reference image pixels, and for each of the plurality of reference images, generating a plurality of reference image detector count maps corresponding to the plurality of reference image pixels associated therewith by editing the corresponding reference image detector count values, storing the plurality of reference image detector count maps, obtaining a scout image of a patient's breast at a first projection angle by emitting a scout x-ray dose towards the patient's breast using the tomosynthesis system, the scout image including a plurality of pixels, each of the plurality of pixels being associated with a detector count value from among the plurality of detector count values, identifying a first region on the scout image corresponding to the highest density portion of the patient's breast, calculating an average detector count value by averaging one or more detector count values corresponding to one or more pixels within the first region, identifying a second region on a first reference image associated with the first projection angle, the second region corresponding to a location on the first reference image that coincides with the location of the first region on the scout image, the first projection angle being one of the plurality of projection angles and the first reference image being one of the plurality of reference images, obtaining one or more reference detector count values associated with one or more reference pixels within the second region of the first reference image, calculating an average reference detector count value by averaging the one or more reference detector count values, calculating an AEC calibration dose to be used in a tomosynthesis scan based on a ratio between the average reference detector count value and the average detector count value, and setting a radiation dose for tomosynthesis sweeps at a plurality of projection angles in the patient's breast to the AEC calibration dose.

Brief Description of the Drawings

[0008] The following drawings are illustrative of specific examples of the present disclosure and, accordingly, do not limit the scope of the present disclosure. The drawings are not to scale and are intended for use in conjunction with the description in the following detailed explanation. Examples of the present disclosure will hereinafter be described in conjunction with the accompanying drawings in which like numbers represent like elements.

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[0019] The various examples will be described in detail with reference to the drawings, in which like reference numerals represent like parts and assemblies throughout the several views. The reference to the various examples does not limit the scope of the claims appended hereto. Additionally, none of the examples described herein are intended to be limiting, but rather merely describe some of the many possible examples related to the appended claims.

[0020] Digital tomosynthesis is a process in which several two-dimensional projection views are obtained at different projection angles. The total range of angles at which x-ray images are acquired is typically about + / -7.5 degrees. Each of the images is obtained using a lower x-ray dose compared to a conventional mammogram. The obtained two-dimensional projection views can be along any desired plane within the breast and can be reconstructed into tomosynthesis slice views representing any thickness of breast tissue. Thus, the set of reconstructed tomosynthesis images that are combined represents the entire volume of the breast in a stack of two-dimensional images. For tomosynthesis, the breast is immobilized or compressed to the same or a lesser extent as in conventional mammography.

[0021] Typically, a tomosynthesis system may use an automatic exposure control (AEC) system and method to automatically control the amount of radiation delivered to a patient's breast. The AEC system may automatically terminate the irradiation when the desired amount of radiation has been delivered. The desired amount of radiation is based on balancing the need to minimize the amount of radiation exposure to the patient and generating a properly irradiated image.

[0022] The AEC system may operate by controlling one or more technical factors to obtain the desired amount of radiation. The one or more technical factors include the kilovoltage peak (kVp), which is the difference in potential applied across the X-ray cathode and X-ray anode tube, and the milliampere seconds (mAs), which is a measure of the current from the X-ray cathode to the X-ray anode applied over a set amount of time through the X-ray tube. The combination of the kVp and mAs values directly affects the radiation dose delivered to the patient's breast and the image quality of the mammogram. In some examples, an operator of the tomosynthesis system may select the kVp value based on the thickness of the patient's breast, and the mAs value may be varied by the AEC system to achieve the desired radiation level. In other examples, the AEC system may similarly select both the kVp and mAs values.

[0023] Generally, the AEC system may first deliver a short, low-dose X-ray pulse or emission to the patient's breast. The resulting scout image of the receptor is read by a computer process to determine the breast area of maximum radiation density. Based on the detector values in the breast area of maximum radiation density in the scout image, the AEC system may calculate the correct final AEC dose, including the kVp and mAs values, and generate a properly irradiated final image.

[0024] However, AEC for wide - angle tomosynthesis has several issues not seen in narrow - angle tomosynthesis. Here, "wide - angle tomosynthesis" can be defined as a range exceeding approximately + / - 15 degrees. In a typical tomosynthesis system, scout irradiation and images are obtained at an angle of zero degrees with respect to the breast. In wide - angle tomosynthesis, scout irradiation can be performed at a large angle of incidence with respect to the breast, far from the zero - degree normal direction to the breast. For example, the scout irradiation angle can range between approximately + / - 30 degrees or + / - 60 degrees. Scout irradiation can typically be obtained at any angle within the range of angles at which the X - ray source and tomosynthesis equipment are positioned after the previous use of the equipment. In other words, the tomosynthesis equipment does not need to be reset or aligned to a particular angle, such as 0 degrees, to perform scout irradiation. This allows the tomosynthesis equipment to be used without wasting time by resetting the equipment to a 0 - degree angle during use. Rather, the disclosed systems and methods account for the angle of incidence to accurately obtain images when the angle of incidence of the scout irradiation is anywhere within the range of angles. At large angles of incidence, the X - ray path length through the breast is much longer than the breast compression thickness. Therefore, for accurate calculation of the AEC dose, the AEC system needs to consider parameters such as the angle of emission and the "heel effect". The heel effect is caused by a reduction in X - ray intensity along the direction from the chest wall to the nipple.

[0025] For example, the angle and heel effect affect the accuracy of the calculated AEC dose because the detector count value at the detector center from the scout irradiation decreases as the AEC tube angle increases. In other words, the larger the projection angle, the smaller the detector count from the scout irradiation of the same X-ray dose. Additionally, detector pixels on the far side of the detector relative to the chest wall tend to experience lower counts than those pixels on the chest wall side of the detector. Further, as the projection angle varies, the central location of the breast as projected on the detector shifts. Since the highest density portion of the breast is typically selected for dose calculation from the central location of the breast, the shift in the central location must be taken into account in order to accurately calculate the AEC dose.

[0026] To accurately calculate the radiation dose that results in an appropriately irradiated image that meets the image quality threshold from the wide-angle tomosynthesis process, the present disclosure generates a reference detector count map at each of the projection angles. For example, one or more wide-angle tomosynthesis scans with a high X-ray dose can be performed on a uniform phantom at one or more projection angles to generate a reference detector count map for each of the one or more separate angles. A look-up table with a scale factor can also be used to generate reference detector count maps for different breast thicknesses. Curve fitting can be applied to the reference detector count map to derive the detector count values at intermediate projection angles. The reference detector count maps associated with each of the plurality of projection angles are stored and can be used in calculating the AEC X-ray dose required to obtain an X-ray image during the tomosynthesis scan.

[0027] The process of calculating the X-ray dose starts by obtaining a scout image of the patient's breast at a first projection angle using the scout dose. Once the scout image is obtained, the highest density portion of the patient's breast is identified within the scout image, and the average detector count value associated with the identified highest density portion of the patient's breast is calculated. A reference image and a corresponding reference detector count map associated with the first projection angle are then retrieved. A second region corresponding to the location of the first region on the scout image is then identified within the reference image. The reference detector count map is used to determine the reference detector count value associated with the second region on the reference image, and the average reference detector count value associated with the second region is calculated. The ratio of the reference X-ray dose value to the average detector count value of the reference detector count value can be used to calculate the X-ray dose required for the tomosynthesis scan.

[0028] Figure 1A is a schematic view of an exemplary imaging system 100, and Figure 1B is a perspective view of the imaging system 100. Referring simultaneously to Figures 1A and 1B, not all of the elements described below are depicted in both figures. The imaging system 100 immobilizes a patient's breast 102 for X-ray imaging (one or both of mammography, tomosynthesis, or other imaging modalities) via a breast compression immobilizer unit 104, and the breast compression immobilizer unit includes a static breast support platform 106 and a movable paddle 108. Different paddles, each having a different purpose, are known in the art. One exemplary paddle is also described herein for context. Each of the breast support platform 106 and the paddle 108 has a compression surface 110 and 112, respectively, and the compression surfaces 110 and 112 compress, immobilize, stabilize, or otherwise hold and fix the breast 102 by moving towards each other during the imaging procedure. In known systems, the compression surfaces 110, 112 are exposed to directly contact the breast 102. One or both of these compression surfaces 110, 112 can be, for example, hard plastic, flexible plastic, elastic foam, mesh, or screen. The platform 106 also houses the receptor 116, and optionally, the tilt mechanism 118, and optionally, an anti-scatter grid (not depicted but disposed above the receptor 116). The immobilizer unit 104 is in the path of the imaging beam 120 emitted from the X-ray source 122, whereby the beam 120 impinges on the receptor 116.

[0029] The immobilizer unit 104 is supported on the first support arm 124 via the compression arm 134, and the compression arm 134 is configured to be raised or lowered along the support arm 124. The X-ray source 122 is supported on a second support arm, also referred to as the tube head 126. For mammography, the support arms 124 and 126 can rotate integrally about the axis 128 between different imaging orientations, such as CC and MLO, so that the system 100 can take mammogram projection images in each orientation. During operation, the receiver 116 remains in a fixed position relative to the platform 106 while an image is being taken. The immobilizer unit 104 releases the breast 102 for movement of the arms 124, 126 to different imaging orientations. For tomosynthesis, while the support arm 124 remains in a fixed position and the breast 102 is immobilized, at least the second support arm 126 rotates the X-ray source 122 about the axis 128 relative to the immobilizer unit 104 and the compressed breast 102. The system 100 takes a plurality of tomosynthesis projection images of the breast 102 at respective projection angles of the beam 120 with respect to the breast 102.

[0030] Simultaneously and optionally, the receptor 116 can be tilted relative to the breast support platform 106 and in synchronization with the rotation of the second support arm 126. The tilt can be such that the beam 120 can be made through the same angle as the rotation of the x-ray source 122, but can also be through different selected angles so as to remain substantially at the same position on the receptor 116 for each of a plurality of images. The tilt can be about an axis 130, which axis 130 can, although not necessarily, be within the image plane of the receptor 116. A tilt mechanism 118 coupled to the receptor 116 can drive the receptor 116 in a tilting motion. For tomosynthesis imaging and / or CT imaging, the breast support platform 106 can be horizontal or at an angle relative to horizontal, for example, in a similar orientation to that for conventional MLO imaging in mammography. The system 100 can be, alone, a mammography system, a CT system, or can be, alone, a tomosynthesis system, another modality such as ultrasound, or can be a "combo" system capable of performing multiple forms of imaging. An example of the system is provided by the assignee of this specification under the trade name "Selenia Dimensions".

[0031] When the system is operated, the receptor 116 generates imaging information in response to illumination by the imaging beam 120 and supplies it to an image processor 132 for processing and generating a breast x-ray image.

[0032] The system control and workstation unit 138, including software, controls the operation of the system, interacts with the operator to receive commands, and delivers information including the processed radiographic image. The system control and workstation unit 138 can include an automatic exposure control (AEC) engine, which can be configured to calculate the AEC x-ray dose required to perform x-ray imaging such as tomosynthesis scanning on a patient's breast. The configuration of the AEC engine is described in more detail in relation to FIG. 2.

[0033] The imaging system 100 includes a floor-mounted portion or base 140 for supporting the imaging system 100 on the floor. A gantry 142 extends upward from the floor-mounted portion 140 and rotatably supports both the tube head 126 and the support arm 124. The tube head 126 and the support arm 124 are configured to rotate separately from each other and can be raised and lowered along the plane 144 of the gantry 142 to accommodate patients of different heights. The X-ray source 122 is disposed within the tube head 126. The tube head 126 and the support arm 124 together may be referred to as a C-arm 144.

[0034] Several interfaces and display screens are disposed on the imaging system 100. These include a foot display screen 146, a gantry interface 148, a support arm interface 150, and a compression arm interface 152. In general, the various interfaces 148, 150, and 152 may include one or more display screens including capacitive touchscreens with one or more tangible buttons, knobs, switches, and a graphical user interface (GUI) to enable user interaction with and control of the imaging system 100. In general, the foot display screen 146 is primarily a display screen, but a capacitive touchscreen may be utilized if required or desired.

[0035] FIG. 2 illustrates an exemplary configuration 200 of an automatic exposure control (AEC) engine 202 of the system of FIG. 1A. The AEC engine 202 may be configured within the workstation 138 of the imaging system 100. The description of FIG. 2 refers to the components depicted in FIGS. 1A and 1B and is appropriately numbered.

[0036] The AEC engine 202 may include a reference detector count map generation module 204 and an AEC dose calibration module 206. Other types of modules are also possible. The AEC engine is configured to calculate an AEC X-ray dose that should be used during X-ray imaging of a patient's breast, including during a full tomosynthesis sweep process. The AEC X-ray dose may include an X-ray dose calculated to balance the need to reduce the amount of radiation to which the patient is exposed with the need to obtain an image that is sufficiently clear to detect potentially abnormal regions within the patient's breast.

[0037] The reference detector count map generation module 204 may be configured to generate a reference detector count map for each of a plurality of projection angles for which the imaging system 100 may be configured to operate. For example, with respect to a wide-angle tomosynthesis sweep, the range of projection angles for which the imaging system 100 may operate may typically extend from +30 to -30 degrees and, in some cases, may also extend between +60 and -60 degrees. The reference detector count map generation module 204 may obtain a reference detector count map at each of the separate projection angles for which the imaging system 100 may operate.

[0038] For an imaging system that may operate at + / -30 degrees, the reference detector count map generation module 204 may obtain a reference image and generate a reference detector count map for each of the 61 separate projection angles that exist from +30 degrees to -30 degrees in 1-degree increments. In some examples, the reference detector count map generation module 204 may similarly obtain a reference detector count map at intermediate projection angles. In other examples, the reference detector count map for intermediate projection angles may be pre-calculated and stored or may be calculated in real time using a curve approximation operation that is described in more detail in connection with FIG. 6.

[0039] The reference detector count map generation module 204 irradiates a uniform-thickness anthropomorphic phantom with X-ray radiation of a reference dose, obtains the resulting reference image, determines the detector count value for each of the pixels in the reference image, and generates a map associating the determined detector count values with each of the pixels in the reference image, thereby enabling the imaging system 100 to generate a reference detector count map at each of a plurality of projection angles.

[0040] The reference dose used to generate the reference image is known to result in an X-ray image with sufficient sharpness and can be an X-ray dose typically used in a clinical setting. For example, a typical reference X-ray radiation dose can be 5 mGy to 10 mGy for a 4 cm thick uniform anthropomorphic phantom.

[0041] Once the reference detector count maps for each of the plurality of projection angles are generated, the reference detector count maps are stored in a local data store or an external data store communicatively connected to the imaging system 100. As will be described below in connection with the AEC dose calibration module 206 and FIG. 7, the reference detector count maps for each projection angle can then be used by the AEC dose calibration module 206 to calculate the AEC X-ray dose required for the wide-angle tomosynthesis imaging process. As explained above, the term "AEC X-ray dose" is defined as the X-ray dose that balances the need to reduce the amount of radiation to which the patient is exposed with the need to obtain an image that is sufficiently sharp to detect potentially abnormal regions within the patient's breast. In other words, the "AEC X-ray dose" as used within the present application is the minimum amount of X-ray dose required to obtain an X-ray image with an image quality that is sufficient to detect potential abnormalities within the patient's breast. The process of generating the reference detector count map is described in more detail in connection with FIGS. 3-6.

[0042] The AEC dose calibration module 206 is configured to automatically calculate the AEC x-ray dose required to obtain a properly sharp x-ray image of a patient's breast during a tomosynthesis scanning process. The AEC dose calibration module 206 may use a stored reference detector count map in calculating the AEC dose.

[0043] In some examples, the AEC dose calibration module 206 may move components of the imaging system 100 to a specific projection angle to initiate the dose calibration process. In other examples, the AEC dose calibration module 206 may initiate the dose calibration process from any projection angle at which the components of the imaging system 100 are currently positioned.

[0044] The AEC dose calibration process may be initiated by obtaining a scout image of the patient's breast using a low x-ray dose. The low x-ray dose may be a dose that is part of a typical x-ray dose, such as 5% or 10% of a typical x-ray dose. The AEC x-ray dose to be used during the tomosynthesis process may be calculated by comparing the detector count value associated with the scout image to the reference detector count value associated with a reference image from a reference detector count map obtained and stored by the reference detector count map generation module 204. The process of calculating the AEC calibrated x-ray radiation dose to be used during the tomosynthesis process is described in more detail in connection with FIGS. 6-7.

[0045] FIG. 3 illustrates an exemplary schematic diagram 300 of the imaging system 100 during generation of a reference image. The imaging system 100 immobilizes a phantom 302 that simulates a patient's breast for X-ray imaging via a breast compression immobilizer unit 104 (not shown in FIG. 3) that includes a movable paddle 108. The support arm rotates an X-ray source 122 (not shown in FIG. 3) around an axis with respect to the immobilizer unit 104 that includes the movable paddle 108 and the phantom 302. The receptor 116 generates imaging information in response to illumination by an imaging beam 120 from the X-ray source 122 as the support arm rotates the X-ray source 122 along each of a plurality of projection angles 304. Thus, the imaging system 100 can obtain a plurality of reference images 306 with at least one reference image at each of the respective projection angles 304.

[0046] FIG. 3 illustrates projection angles 304 from -30 degrees to +30 degrees, although the projection angles can extend over a larger or smaller range depending on the type of the imaging system 100. Generation of a reference detector count map from each of the plurality of reference images 306 is described in further detail in connection with FIG. 4.

[0047] FIG. 4 illustrates an exemplary schematic diagram 400 of a reference image and a corresponding reference detector count map generated by a reference detector count map generation module 204 of the imaging system 100.

[0048] Each reference image 402 among the plurality of reference images 306 generated by the imaging system 100 includes a plurality of pixels 404. The plurality of pixels 404 in the reference image 402 of FIG. 4 are labeled with numbers ranging from 1 to 100, although in reality, the plurality of pixels 404 can extend over a larger or smaller range of pixels.

[0049] When the reference detector count map generation module 204 of the AEC engine 202 obtains a reference image 402 as described in connection with FIG. 3, it can determine the reference detector count values associated with each of the plurality of pixels 404 by communicating with the receiver 116 and the image processor 132 to determine the digital counts of the X-ray signals received by the receiver when the anthropomorphic phantom 302 is irradiated with X-ray radiation from the X-ray source 122.

[0050] Based on the reference detector count values communicated by the receiver 116 and the image processor 132, the reference detector count map generation module 204 of the AEC engine 202 can generate a reference detector count map 406 for each reference image 402. In some examples, the reference detector count map 406 can include a table in which each of the plurality of pixels 404 is listed in one column and the corresponding detector count values are listed in a second column. In other examples, the plurality of pixels 404 and the corresponding detector count values can be arranged differently. Once generated, the reference detector count map 406 can be stored in a local data store within the imaging system 100 or in an external data store communicatively coupled to the imaging system 100.

[0051] FIG. 5 illustrates an exemplary schematic diagram 500 of a curve approximation operation for estimating reference detector count values at intermediate projection angles. As described in connection with FIG. 3, the reference image 306 is captured only at certain projection angles. The reference image 306 is typically captured at projection angles that are 1-degree increments within the range of projection angles at which the imaging system operates. The reference image 306 and the corresponding reference detector count map 406 may not be available or generated for intermediate projection angles. To calculate the AEC dose, the AEC dose calibration module 206 of the AEC engine 202 may require the reference detector count map 406 at intermediate projection angles while the reference detector image 306 may not be available from the reference detector count map generation module 204. In such cases, the reference detector count values for intermediate projection angles can be estimated based on the reference detector count map 406 stored for adjacent individual projection angles by performing a curve approximation operation on the data from the stored reference detector count map.

[0052] The exemplary schematic diagram 500 illustrates a curve approximation operation associated with one of the pixels, pixel number 65 from FIG. 4 (from among the plurality of pixels 404). The exemplary schematic diagram 500 includes a plot 502 with an x-axis and a y-axis. The x-axis may include a range of projection angles. In this example, the projection angles can range from -30 to +30 degrees. The y-axis may include a range of detector count values.

[0053] To perform the curve approximation operation, for each pixel of the plurality of pixels 404, the reference detector count values corresponding to each of the plurality of projection angles on the x-axis can be plotted as a graphical representation. For each pixel of the plurality of pixels 404, for example, the plot 502 associated with pixel number 65 as illustrated in FIG. 5 can include a plot of each of the detector count values 504 corresponding to each of the plurality of projection angles, and each of the detector count values 504 can be extracted from the reference detector count map 406 corresponding to a particular projection angle.

[0054] For example, at a projection angle of -30 degrees, a reference detector count map 406 for -30 degrees can be read from the data store, and a reference detector count value associated with pixel number 65 can be identified. The process can be repeated for each projection angle for projection angles ranging from -30 degrees to +30 degrees using each reference detector count map 406 to capture the detector count value 504 in plot 502.

[0055] When plot 502 is generated, a curve approximation function can be used to generate a curve 506 that fits the detector count value 504. Curve approximation can be a process of constructing a curve or mathematical function that best fits a series of data points. In some examples, curve approximation can be performed using an interpolation function or an extrapolation function. In other examples, a polynomial curve approximation where a polynomial function is fitted to a series of data points can be used to generate curve 506.

[0056] When polynomial curve approximation is used, the degree of the polynomial function can range from a low order such as first order to a high order such as fifth or sixth order. Generally, when generating a curve 506 that fits the detector count value 504, a fourth-order polynomial function such as "y = ax 4 + bx 3 + cx 2 + dx + e" can be used. When a polynomial function representing curve 506 that fits the detector count value 504 is generated using regression analysis, the coefficients of the generated polynomial function can be stored in the data store. The polynomial coefficients can later be used by the AEC dose calibration module 206 to estimate detector count values at intermediate projection angles or angles outside the + / - 30-degree scan angle range, almost in real time.

[0057] Figure 6 illustrates an exemplary method 600 for generating a reference detector count map 406 at each of a plurality of projection angles 304 using the reference detector count map generation module 204 of the imaging system 100. Method 600 begins at operation 602. At operation 602, the reference detector count map generation module 204 of the imaging system 100 may obtain a reference image 306 of the anthropomorphic phantom 302 at each of the plurality of projection angles 304. For example, the reference detector count map generation module 204 may cause the anthropomorphic phantom 302 to be irradiated with the imaging system 100 using a reference radiation dose and obtain the resulting X-ray images for each of the plurality of projection angles 306.

[0058] The reference radiation dose may include any dose of radiation that is effective in producing an X-ray image that meets at least a threshold image quality level. The anthropomorphic phantom 302 used in generating the reference image may generally be made of a uniform material and have a uniform thickness. In some examples, for each of the plurality of projection angles 304, the reference detector count map 406 may be generated using an anthropomorphic phantom 302 with a thickness that mimics an average patient breast. In other examples, the reference detector count map 406 may be generated using anthropomorphic phantoms of different thicknesses.

[0059] Although the reference detector count map 406 for each of the plurality of projection angles 304 is generated using an anthropomorphic phantom 302 of a particular thickness, reference detector count maps corresponding to other breast thicknesses may be derived from the reference detector count map obtained using an anthropomorphic phantom 302 of average thickness by applying a scale factor from a previously generated look-up table. The process of obtaining reference detector count maps for different breast thicknesses is further described in FIG. 7.

[0060] In some examples, the plurality of projection angles 404 for which the reference image 306 is obtained for generating the reference detector count map may include each of the separate projection angles within the range of projection angles included within the tomosynthesis sweep performed by the imaging system 100. In some examples, the range of projection angles may be +30 degrees to -30 degrees. In such a case, the separate projection angles may include each of the 61 separate projection angles from +30 degrees to -30 degrees. In other examples, the range of projection angles may be +60 degrees to -60 degrees, in which case the separate projection angles may include each of the 121 separate projection angles from +60 degrees to -60 degrees. In other examples, instead of obtaining the reference image at 1-degree increments, the reference image may be obtained at other regular intervals, such as every 2 degrees or every 5 degrees, etc.

[0061] In some examples, the plurality of projection angles for which the reference image is obtained for generating the reference detector count map may include a greater or lesser number of projection angles, may include angles that are between separate angles such as projection angles at 0.5-degree increments, or may include angles outside the range of angles for which the reference image is obtained. In other examples, a curve approximation operation, such as described in connection with FIG. 5, may be implemented, and in the case of a polynomial curve approximation operation, the corresponding polynomial coefficients may be stored and used to generate estimated detector count values at intermediate projection angles or at scan angles outside the range in real time or near real time.

[0062] In operation 604, the reference detector count map generation module 204 of the imaging system 100 may determine a reference detector count value associated with each of the plurality of pixels within each of the reference images 306 for each of the reference images 306 obtained in operation 602.

[0063] Each of the reference images obtained in operation 602 includes a plurality of pixels 404. For example, the reference detector count map generation module 204 can communicate with the receiver 116 and the image processor 132 to determine the digital count of the X-ray signal received by the receiver 116 when the anthropomorphic phantom 302 is irradiated with the reference X-ray dose in operation 602. The count of the X-ray signal associated with a particular pixel of the reference image 402 is determined to be the reference detector count value associated with the particular pixel of the reference image 402. Thus, the reference detector count value for each of the plurality of pixels 404 within each of the reference images 306 obtained in operation 602 can be determined in operation 604.

[0064] In operation 606, the reference detector count map generation module 204 can generate a reference detector count map for each of the plurality of projection angles 304 based on the reference detector count values determined in operation 604 for each of the reference images 306 obtained in operation 602. The reference detector count map 406 can include a map between each pixel in the reference image and the corresponding reference detector count value measured at the receiver 116 when the reference X-ray dose is emitted onto the anthropomorphic phantom.

[0065] In operation 608, the reference detector count map generation module 204 can store the reference detector count maps 406 generated for each of the plurality of projection angles 304, the corresponding projection angle information, and the reference X-ray dose information in a data store local to the imaging system 100 or in a data store communicatively connected to the imaging system 100 but external to the imaging system 100. The stored reference detector count maps and reference X-ray dose information can be read out and used in the calculation of the AEC X-ray dose as described in FIG. 7.

[0066] When a reference detector count value for a projection angle is required in calculating the AEC x-ray dose while a reference image and corresponding reference detector count map are not available, a curve approximation operation can be performed to obtain the reference detector count value, as further described above in connection with FIG. 5.

[0067] FIG. 7 illustrates an exemplary method 700 for calculating an AEC x-ray dose required to perform x-ray imaging, including wide-angle tomosynthesis scanning of a patient's breast, using the imaging system 100. In operation 702, the AEC dose calibration module 206 may cause the imaging system 100 to obtain a scout image of the patient's breast at a first projection angle. In some examples, and in a typical tomosynthesis system, the first projection angle may be a particular projection angle from among a plurality of projection angles 304, such as 0 degrees. However, rather than moving the support arms 124 and 126 of the imaging system 100 to a particular projection angle, the AEC dose calibration module 206 may cause the imaging system 100 to obtain a scout image from the current positions of the support arms 124 and 126. The current positions of the support arms 124 and 126 may simply be based on whatever position the support arms 124 and 126 were left at after the previous operation of the imaging system 100. Moving the support arms 124, 126 before starting each tomosynthesis process and resetting the support arms 124, 126 to an angle of 0 degrees or a particular angle requires time and effort. Additionally, moving the support arms 124, 126 to an exact position is difficult to achieve and often results in a margin of error of several degrees. Thus, having the ability to obtain a scout image from any current position results in obtaining a more accurate scout image.

[0068] Scout images of a patient's breast can be obtained using low X-ray doses. Typically, 5% or 10% of the reference dose can be used in obtaining the scout image. The scout image is used as a starting point in the calculation of the actual dose required to perform a full tomosynthesis sweep according to the AEC process. Thus, a low X-ray dose is used to obtain the scout image in order to limit radiation exposure to the patient.

[0069] In operation 704, the AEC dose calibration module 206 may identify a first region on the scout image obtained during operation 702 as corresponding to the highest density portion of the patient's breast. Generally, the highest density portion of the patient's breast is identified to determine the minimum amount of X-ray dose required to obtain an acceptable detector count value even at the highest density portion of the patient's breast. In other words, the highest density portion of the patient's breast is typically the region through which X-rays pass most difficultly and thus requires the most amount of dose to generate an image of adequate quality. Thus, when the X-ray radiation dose is calibrated with respect to the highest density region of the patient's breast, the X-ray radiation dose is typically appropriate with respect to the remaining regions of the patient's breast.

[0070] The highest density region of the patient's breast can be determined by first flattening the scout image by applying a gain map associated with the first projection angle to calibrate the scout image with respect to the angle effect and the heel effect.

[0071] When a digital flat panel X-ray imaging receptor is used, one of the practical requirements is to provide gain calibration. The imaging receptor may comprise a two-dimensional array of millions of imaging pixels, and there may be inherent differences in the responses of different imaging pixels to impinging X-rays. When all imaging pixels are subjected to the same X-ray irradiation, ideally each should provide the same electrical output signal (pixel value). However, in practice this may not be the case, and typically there are differences between the pixel values provided by different imaging pixels when irradiated with the same X-ray input. In addition, the incident X-ray intensity across the detector surface is usually non-uniform, and for example, due to the "heel effect", the X-ray intensity decreases along the direction from the chest wall to the nipple. Various gain calibration and image correction techniques are employed to correct for differences in pixel values in response to uniform X-ray irradiation and to correct for non-uniform X-ray intensity distributions across the X-ray imaging detector surface area. Typically, in conventional X-ray mammography, the flat panel imager is exposed to the X-ray field through a "flat field" phantom that simulates the patient's breast, has a uniform thickness, and is made of a uniform material, and the differences between pixel values are recorded and a gain correction map that takes into account such differences at each of the projection angles is generated. Each gain correction map corresponding to each projection angle can be stored locally in a data store within the imaging system 100 or in an external data store communicatively connected to the imaging system 100.

[0072] When a scout image is generated by exposing the patient's breast to X-ray radiation at a first projection angle, the gain correction map corresponding to the first projection angle is read from the data store and the gain correction map and applied to the scout image to flatten the scout image and minimize the angle and heel effect. The angle-corrected scout image can then be used to identify the highest density portion of the patient's breast.

[0073] For example, the highest density portion of a patient's breast is typically found at the center of the breast and is associated with the lowest detector count value. Thus, a simplified method of identifying the highest density portion of a patient's breast involves identifying a first region with a group of pixels having the lowest corresponding detector count value within a specific area of a scout image that is likely to include the center of the breast. Once the first region that includes the group of pixels with the lowest detector count value is identified, a specific location on the scout image that includes the first region is determined to be the highest density portion of the patient's breast.

[0074] In operation 706, the AEC dose calibration module 206 may calculate an average detector count value associated with the group of pixels within the first region of the scout image. For example, the average detector count value may be determined by determining the detector count value associated with each pixel within the group of pixels located within the first region identified in operation 704 and averaging the detector count values to arrive at the average detector count value.

[0075] In operation 708, the AEC dose calibration module 206 of the AEC engine 202 may read from the data store a reference image and a reference detector count map corresponding to the first projection angle, where the reference detector count map was generated by the reference detector count map generation module 204 and stored in the data store in operation 608 from FIG. 6. If the reference image and the reference detector count map for the first projection angle are not available in the data store because the first projection angle is an angle or outside the scan range while the reference detector count map generation module 204 was not generating the reference image or the reference detector count map, the AEC dose calibration module 206 may proceed to operation 712, where a polynomial curve approximation operation or an interpolation or extrapolation operation may be used to generate the reference detector count values that are required in real time or near real time.

[0076] In operation 710, the AEC dose calibration module 206 of the AEC engine 202 may identify a second region on the read reference image, where the second region corresponds to the first region from the scout image as identified in operation 704 in terms of position. As an example, if the first region identified in operation 704 includes pixels corresponding to pixel numbers 56, 57, 66, 67 on the scout image, the second region associated with the reference image may also include pixels corresponding to pixel numbers 56, 57, 66, 67.

[0077] In operation 712, after identifying the second region corresponding to the reference image, the AEC dose calibration module 206 may determine the reference detector count values corresponding to the pixels within the second region.

[0078] If the first projection angle is an angle during which the reference image and the corresponding reference detector count map were not available or generated, the AEC dose calibration module 206 may estimate the reference detector count values for the pixels within the second region using a polynomial curve approximation function or an interpolation function in real time or near real time, as described in FIG. 5. In other examples, instead of using curve approximation only to generate the reference detector count values for the pixels within the second region, the curve approximation function may be applied to generate a complete reference image and the corresponding reference detector count map.

[0079] In operation 714, the AEC dose calibration module 206 may also adjust the detector count values based on the patient's breast size. As described above, the reference image and the corresponding reference detector count map are based on the anthropomorphic phantom 302 corresponding to the average patient breast thickness. In some examples, the anthropomorphic phantom 302 may have a thickness of 4 cm, and the reference detector count values included in the reference detector count map may function as reference values for patients with a breast thickness of approximately 4 cm. However, when the patient's breast thickness is significantly higher or lower, the reference detector count values may need to be adjusted.

[0080] Generally, a look-up table including a scale factor corresponding to a method of adjusting a detector count value when the thickness of a patient's breast is different from the thickness of the anthropomorphic model 302 can be used to adjust the reference detector count value associated with the pixels in the second region. For example, the look-up table may indicate that the scale factor associated with a patient breast thickness of 6 cm may be 1.2. In such a case, as determined in operation 712, the reference detector count value for the pixels in the second region determined by the AEC dose calibration module 206 may be multiplied by a factor of 1.2 to reach the adjusted reference detector count value.

[0081] Alternatively, the reference image and the corresponding reference detector count map can be obtained, generated, and stored for anthropomorphic models of different sizes. In other words, instead of obtaining a reference image and generating a reference detector count map based on the anthropomorphic model 302 corresponding to the average patient breast thickness, the process described in FIG. 6 can be repeated for different anthropomorphic model thicknesses, and the reference image and the reference detector count map corresponding to each anthropomorphic model thickness can be stored. In such a case, in operation 708, the reference image and the reference detector count map corresponding to the anthropomorphic model thickness matching the patient's breast thickness can be read out, and the adjustment operation outlined above in relation to operation 714 can be omitted since the reference detector count value already takes into account the factor corresponding to the patient's breast thickness.

[0082] In operation 716, the AEC dose calibration module 206 can calculate the average reference detector count value associated with the pixels in the second region. The calculation of the average reference detector count value can be based on the adjusted reference count value as determined in operation 714. To calculate the average reference detector count value, the AEC dose calibration module 206 can simply calculate the average value corresponding to the adjusted reference detector count values corresponding to the pixels in the second region of the reference image.

[0083] In operation 718, the AEC dose calibration module 206 may calculate the dose to be used in the full tomosynthesis scan based on the ratio of the average reference detector count value to the average detector count value. For example, the AEC calibration x-ray radiation dose for a full tomosynthesis sweep may be calculated based on the following formula.

Number

[0084] In operation 720, the AEC dose calibration module 206 sets the AEC calibration x-ray radiation dose level of the imaging system 100 to the value calculated in operation 718, and may cause the imaging system 100 to perform a tomosynthesis sweep over the entire range of projection angles using the set AEC calibration x-ray radiation dose. The AEC calibration x-ray radiation dose calculated in operation 718 also balances the need to generate tomosynthesis x-ray images properly irradiated at a plurality of projection angles while minimizing the amount of radiation exposure to the patient.

[0085] FIG. 8 illustrates an example of a suitable operating environment 800 in which one or more of the examples described herein can be implemented. This operating environment can be incorporated directly into the visualization systems disclosed herein, or can be incorporated into a computer system that is separate from but used to control the breast imaging systems described herein, such a computer system can be, for example, the workstation depicted in FIG. 1A. This is merely an example of a suitable operating environment and is not intended to suggest any limitation as to the scope of use or functionality. Other well-known computing systems, environments, and / or configurations that may be suitable for use include, but are not limited to, imaging systems, personal computers, server computers, handheld or laptop devices, multiprocessor systems, microprocessor-based systems, programmable consumer electronics such as smart phones, network PCs, minicomputers, mainframe computers, tablets, distributed computing environments including any of the above systems or devices, and the like.

[0086] In its most basic configuration, the operating environment 800 typically includes at least one processing unit 802 and a memory 804. Depending on the exact configuration and type of computing device, the memory 804, which stores instructions 806 (for reading from data storage devices or sensors or for performing other methods disclosed herein), can be volatile 808 (such as RAM), non-volatile 810 (such as ROM, flash memory, etc.), or a combination of the two. The instructions 806, when executed by the processing unit 802, can include AEC engine instructions that cause the processing unit 802 to perform operations further described in relation to FIGS. 2-7 on the AEC engine 202. The most basic configuration is illustrated in FIG. 8 by the dashed line 812. Further, the environment 800 can also include, but is not limited to, storage devices (removable 814 and / or non-removable 816) including magnetic or optical disks or tapes. Similarly, the environment 800 can also have input devices 820 such as touchscreens, keyboards, mice, pens, voice inputs, etc., and / or output devices 822 such as displays, speakers, printers, etc. One or more communication connections 818 such as LAN, WAN, point-to-point, Bluetooth®, RF, etc. can also be included in the environment.

[0087] The operating environment 800 typically includes at least some form of computer-readable medium. A computer-readable medium can be any available medium that can be accessed by a processing unit 802 or other device having the operating environment. By way of example, and not limitation, computer-readable media can include computer storage media and communication media. Computer storage media includes volatile and nonvolatile, removable and nonremovable media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules, or other data. Computer storage media includes RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, solid state storage devices, or any other tangible medium which can be used to store the desired information. Communication media includes any information delivery media which embodies computer-readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism. The term "modulated data signal" means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared, and other wireless media. Any combination of the above should also be included within the scope of computer-readable media. A computer-readable device is a hardware device that incorporates computer storage media.

[0088] The operating environment 800 can be a single computer operating within a networked environment that uses logical connections to one or more remote computers. The remote computers can be personal computers, servers, routers, network PCs, peer devices, or other common network nodes, and typically include many or all of the elements described above, as well as others not so mentioned. The logical connections can include any method supported by available communication media. Such networked environments are common in offices, enterprise-wide computer networks, intranets, and the Internet.

[0089] In some examples, the components described herein include such modules or instructions executable by a computer system 800 stored on a computer storage medium and other tangible media and transmitted within a communication medium. The computer storage medium includes volatile and nonvolatile, removable and nonremovable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules, or other data. Any combination of the above should be included within the scope of readable media. In some examples, the computer system 800 is part of a network that stores data in a remote storage medium for use by the computer system 800.

[0090] FIG. 9 is an example of a network 900 in which the various systems and methods disclosed herein may operate. In the example, a client device, such as client device 902, may communicate with one or more servers, such as servers 904 and 906, via network 900. In the example, the client device may be a stand-alone imaging system (e.g., imaging system 100 depicted in FIG. 1A) that includes all of the functionality described herein. The client device may include or incorporate any other type of computing device, such as a laptop, personal computer, smartphone, PDA, netbook, or a computing device such as that in FIG. 8. In the example, such a client device may be connected to the imaging system. In the example, servers 904 and 906 may also be any type of computing device, such as the computing devices illustrated in FIG. 8. Network 900 may be any type of network capable of facilitating communication between the client device and the one or more servers 904 and 906. For example, surface image data and internal image data may be obtained locally via the imaging system and communicated to another computing device, such as an image acquisition workstation or a cloud-based service, for further processing. Examples of such networks include, but are not limited to, LANs, WANs, cellular networks, and / or the Internet.

[0091] In the example, the various systems and methods disclosed herein may be implemented by one or more server devices. For example, in one instance, a single server, such as server 904, may be employed to implement the systems and methods disclosed herein, such as the methods for imaging discussed herein. Client device 902 may interact with server 904 via network 900. In a further example, client device 902 may also implement functionality disclosed herein, such as scanning and image processing, which may then be provided to server 904 and / or 906.

[0092] The present disclosure has described some examples of the present technology with reference to the accompanying drawings in which only some of the possible examples are shown. However, other aspects can also be embodied in many different forms and should not be construed as limited to the examples described herein. Rather, these examples are provided so that the present disclosure will be thorough and complete and will fully convey the scope of possible examples to those skilled in the art.

[0093] Specific examples have been described herein, but the scope of the present technology is not limited to those specific examples. Those skilled in the art will recognize other examples or improvements within the scope of the present technology. Accordingly, specific structures, acts, or media are disclosed only as illustrative examples. Examples according to the present technology may also generally be disclosed, although not explicitly illustrated in combination, elements or components that may be combined, unless otherwise described herein. The scope of the present technology is defined by the following claims and any equivalents thereof.

[0094] Illustrative examples of the systems and methods described herein are provided below. Embodiments of the systems or methods described herein may include any one or more of the appendices described below, and any combination thereof.

[0095] Appendix 1. A tomosynthesis system for performing automatic exposure control (AEC) operation, the system comprising a processor and a memory containing instructions, which when executed by the processor, obtain a scout image of a patient's breast at a first projection angle related to the normal direction of 0 degrees with respect to the patient's breast by emitting a scout x-ray dose towards the patient's breast using the tomosynthesis system, the scout image including a plurality of pixels, each of the plurality of pixels being associated with a detector count value from among a plurality of detector count values, identifying a first region on the scout image so as to correspond to the highest density portion of the patient's breast, calculating an average detector count value by averaging one or more detector count values corresponding to one or more pixels within the first region, identifying a second region on a first reference image associated with the first projection angle, the second region corresponding to a location on the first reference image that coincides with the location of the first region on the scout image, obtaining one or more reference detector count values associated with one or more reference pixels within the second region of the first reference image, calculating an average reference detector count value by averaging the one or more reference detector count values, calculating an AEC calibration dose to be used in the tomosynthesis scan based on the ratio between the average reference detector count value and the average detector count value, and causing the processor to set the radiation dose for the tomosynthesis sweep at a plurality of projection angles in the patient's breast to the AEC calibration dose.

[0096] Appendix 2. Obtaining one or more reference detector count values includes extracting one or more reference detector count values from a reference detector count map associated with the first projection angle, the reference detector count map associated with the first projection angle being one of a plurality of reference detector count maps generated in a calibration process prior to obtaining the scout image, the tomosynthesis system according to Appendix 1.

[0097] Appendix 3. Calibration involves obtaining a plurality of reference images of a human body model, each of the plurality of reference images being obtained using a tomosynthesis system at each of a plurality of projection angles, each of the plurality of reference images including a plurality of reference image pixels, and determining detector count values corresponding to each of the plurality of reference image pixels within each of the plurality of reference images, and generating a plurality of reference detector count maps corresponding to each of the plurality of projection angles by editing the plurality of reference image pixels and the corresponding detector count values associated with each of the plurality of projection angles, the tomosynthesis system according to Appendix 2.

[0098] Appendix 4. When the first projection angle is not one of the plurality of projection angles including the reference detector count map, obtaining reference detector count values associated with one or more reference pixels from a second region of the first reference image includes estimating the reference detector count values by performing (i) an interpolation function, (ii) an extrapolation function, or (iii) a polynomial curve approximation function, the tomosynthesis system according to Appendices 2-3.

[0099] Appendix 5. The plurality of projection angles includes an angular range of from about -60 degrees to about +60 degrees with respect to the patient's breast, the tomosynthesis system according to Appendix 1.

[0100] Appendix 6. Calculating the AEC calculation dose includes multiplying the scout X-ray dose by the ratio between the average reference detector count value and the average detector count value and a global scaling factor, the tomosynthesis system according to Appendix 1.

[0101] Appendix 7. The scout X-ray dose includes a combination of the voltage (kV) used to generate radiation from the X-ray source, the X-ray cathode-anode tube current (mA), and the length of time (seconds) the patient is exposed to the radiation, the tomosynthesis system according to Appendix 1.

[0102] Appendix 8. The scout X-ray dose is less than 10% of the AEC calculation dose, the tomosynthesis system according to Appendix 1.

[0103] Supplementary Note 9. Identifying the highest density part of a patient's breast includes applying a gain map associated with a first projection angle to a scout image to compensate for the angular effect and identifying pixels within a pre-identified central region that includes a minimum detector count value, in the tomosynthesis system according to Supplementary Note 1.

[0104] Supplementary Note 10. A method for performing an automatic exposure control (AEC) operation using a tomosynthesis system, the method comprising obtaining a scout image of a patient's breast at a first projection angle by emitting a scout X-ray dose towards the patient's breast using the tomosynthesis system, the scout image including a plurality of pixels, each of the plurality of pixels being associated with a detector count value from among a plurality of detector count values, identifying a first region on the scout image so as to correspond to the highest density part of the patient's breast, calculating an average detector count value by averaging one or more detector count values corresponding to one or more pixels within the first region, identifying a second region on a first reference image associated with the first projection angle, the second region corresponding to a location on the first reference image that coincides with the location of the first region on the scout image, obtaining one or more reference detector count values associated with one or more reference pixels within the second region of the first reference image, calculating an average reference detector count value by averaging the one or more reference detector count values, calculating an AEC calibration dose to be used in a tomosynthesis scan based on a ratio between the average reference detector count value and the average detector count value, and setting a radiation dose for a tomosynthesis sweep at a plurality of projection angles in the patient's breast to the AEC calibration dose.

[0105] Appendix 11. Obtaining one or more reference detector count values includes extracting one or more reference detector count values from a reference detector count map associated with a first projection angle, where the reference detector count map associated with the first projection angle is one of a plurality of reference detector count maps generated in a calibration process prior to obtaining a scout image, the method described in Appendix 10.

[0106] Appendix 12. The calibration process includes obtaining a plurality of reference images of a anthropomorphic phantom, where each of the plurality of reference images is obtained using a tomosynthesis system at each of a plurality of projection angles, and each of the plurality of reference images includes a plurality of reference image pixels, and determining a reference image detector count value corresponding to each of the plurality of reference image pixels within each of the plurality of reference images, and generating a plurality of reference image detector count maps corresponding to each of the plurality of projection angles by editing the plurality of reference image pixels and the corresponding reference image detector count values associated with each of the plurality of projection angles, the method described in Appendix 11.

[0107] Appendix 13. When the first projection angle is not one of the plurality of projection angles including the reference detector count map, obtaining a reference detector count value associated with one or more reference pixels from a second region of the first reference image includes estimating the reference detector count value by implementing (i) an interpolation function, (ii) an extrapolation function, or (iii) a polynomial curve approximation function, the method described in Appendices 11-12.

[0108] Appendix 14. The plurality of projection angles includes an angular range of from about -60 degrees to about +60 degrees corresponding to a patient's breast, the method described in Appendix 10.

[0109] Appendix 15. Calculating the AEC calculation dose includes multiplying the scout X-ray dose by the ratio between the average reference detector count value and the average detector count value and a global scaling factor, the method described in Appendix 10.

[0110] Appendix 16. The first projection angle is the method described in Appendix 10 based on the current position of the tomosynthesis system prior to obtaining the scout image.

[0111] Appendix 17. The current position is the method described in Appendix 16 that is different from an angle of 0 degrees with respect to the patient's breast.

[0112] Appendix 18. The method described in Appendix 10 further includes obtaining a scout image of the patient's breast at a second projection angle different from the first projection angle.

[0113] Appendix 19. Identifying the highest density portion of the patient's breast includes applying a gain map associated with the first projection angle to the scout image to compensate for the angle effect and identifying pixels within a pre-identified central region that includes the minimum detector count value, the method described in Appendix 10.

[0114] A method of performing a calibration operation associated with an automatic exposure control (AEC) operation using a tomosynthesis system, the method comprising: obtaining a plurality of reference images of a phantom at a plurality of projection angles, each of the plurality of reference images including a plurality of reference image pixels; generating, for each of the plurality of reference images, a plurality of reference image detector count maps by editing the plurality of reference image pixels associated therewith and corresponding reference image detector count values; storing the plurality of reference image detector count maps; obtaining a scout image of a patient's breast at a first projection angle by emitting a scout x-ray dose towards the patient's breast using the tomosynthesis system, the scout image including a plurality of pixels, each of the plurality of pixels being associated with a detector count value from among the plurality of detector count values; identifying a first region on the scout image corresponding to the highest density portion of the patient's breast; calculating an average detector count value by averaging one or more detector count values corresponding to one or more pixels within the first region; identifying a second region on a first reference image associated with the first projection angle, the second region corresponding to a location on the first reference image that coincides with the location of the first region on the scout image, the first projection angle being one of the plurality of projection angles, and the first reference image being one of the plurality of reference images; obtaining one or more reference detector count values associated with one or more reference pixels within the second region of the first reference image; calculating an average reference detector count value by averaging the one or more reference detector count values; calculating an AEC calibration dose to be used in a tomosynthesis scan based on a ratio between the average reference detector count value and the average detector count value; and setting a radiation dose for tomosynthesis sweeps at a plurality of projection angles in the patient's breast to the AEC calibration dose.

Claims

1. A tomosynthesis system for performing automatic irradiation control (AEC) operation, wherein the system is Processor and Memory containing instructions and Equipped with, When the aforementioned instruction is executed by the processor, The method involves obtaining a scout image of the patient's breast at a first projection angle by emitting a scout X-ray dose toward the patient's breast using the tomosynthesis system, wherein the first projection angle is related to the normal direction of 0 degrees to the patient's breast, and the scout image includes a plurality of pixels, each of which is associated with a detector count value from among a plurality of detector count values. Identifying a first region on the scout image to correspond to the densest part of the patient's breast, The average detector count value is calculated by averaging the one or more detector count values ​​corresponding to one or more pixels in the first region, Identifying a second region on a first reference image associated with the first projection angle, wherein the second region corresponds to a location on the first reference image that matches the location of the first region on the scout image. Obtaining one or more reference detector count values ​​associated with one or more reference pixels in the second region of the first reference image, The average reference detector count value is calculated by averaging the one or more reference detector count values. Based on the ratio between the average reference detector count value and the average detector count value, the AEC calibration dose to be used in tomosynthesis scanning is calculated. The radiation dose for tomosynthesis sweeping at multiple projection angles in the patient's breast is set to the AEC calibration dose. A tomosynthesis system that causes the aforementioned processor to perform this operation.

2. Obtaining the one or more reference detector count values ​​mentioned above is: This includes extracting one or more reference detector count values ​​from a reference detector count map associated with the first projection angle, The tomosynthesis system according to claim 1, wherein the reference detector count map associated with the first projection angle is one of a plurality of reference detector count maps generated in a calibration process prior to obtaining the scout image.

3. The aforementioned calibration is Obtaining multiple reference images of a human body model, each of which is obtained using the tomosynthesis system at each of the multiple projection angles, and each of which includes multiple reference image pixels, Determining the detector count value corresponding to each of the multiple reference image pixels in each of the multiple reference images, By editing the plurality of reference image pixels and the corresponding detector count values ​​associated with each of the plurality of projection angles, the plurality of reference detector count maps corresponding to each of the plurality of projection angles are generated. The tomosynthesis system according to claim 2, including the above.

4. When the first projection angle is not one of the plurality of projection angles including the reference detector count map, obtaining the reference detector count value associated with one or more reference pixels from the second region of the first reference image is: The tomosynthesis system according to claim 3, comprising estimating the reference detector count value by performing (i) an interpolation function, (ii) an extrapolation function, or (iii) a polynomial curve approximation function.

5. The tomosynthesis system according to claim 1, wherein the plurality of projection angles include an angle range of approximately -60 degrees to approximately +60 degrees with respect to the patient's breast.

6. The tomosynthesis system according to claim 1, wherein calculating the AEC calculated dose includes multiplying the scout X-ray dose by the ratio between the average reference detector count value and the average detector count value and a global scaling coefficient.

7. The tomosynthesis system according to claim 1, wherein the scout X-ray dose includes a combination of a voltage (kV) used to generate radiation from an X-ray source, an X-ray cathode-anode tube current (mA), and a length of time (seconds) for which the patient is exposed to the radiation.

8. The tomosynthesis system according to claim 1, wherein the scout X-ray dose is less than 10% of the AEC calculated dose.

9. Identifying the densest portion of the patient's breast is, The gain map associated with the first projection angle is applied to the scout image to compensate for the angular effect, Identifying pixels within a pre-identified central region that includes the lowest detector count value. A tomosynthesis system according to claim 1, comprising:

10. A method for performing automatic irradiation control (AEC) operation using a tomosynthesis system, wherein the method is: The method involves obtaining a scout image of the patient's breast at a first projection angle by emitting a scout X-ray dose toward the patient's breast using the tomosynthesis system, wherein the scout image includes a plurality of pixels, and each of the plurality of pixels is associated with a detector count value from among a plurality of detector count values. Identifying a first region on the scout image to correspond to the densest part of the patient's breast, The average detector count value is calculated by averaging the one or more detector count values ​​corresponding to one or more pixels in the first region, Identifying a second region on a first reference image associated with the first projection angle, wherein the second region corresponds to a location on the first reference image that matches the location of the first region on the scout image. Obtaining one or more reference detector count values ​​associated with one or more reference pixels in the second region of the first reference image, The average reference detector count value is calculated by averaging the one or more reference detector count values. Based on the ratio between the average reference detector count value and the average detector count value, the AEC calibration dose to be used in tomosynthesis scanning is calculated. The radiation dose for tomosynthesis sweeping at multiple projection angles in the patient's breast is set to the AEC calibration dose. Methods that include...

11. Obtaining the one or more reference detector count values ​​mentioned above is: This includes extracting one or more reference detector count values ​​from a reference detector count map associated with the first projection angle, The method according to claim 10, wherein the reference detector count map associated with the first projection angle is one of a plurality of reference detector count maps generated in a calibration process prior to obtaining the scout image.

12. The calibration process described above is: Obtaining multiple reference images of a human body model, each of which is obtained using the tomosynthesis system at each of the multiple projection angles, and each of which includes multiple reference image pixels, Determining the reference image detector count value corresponding to each of the multiple reference image pixels in each of the multiple reference images, By editing the plurality of reference image pixels and the corresponding reference image detector count values ​​associated with each of the plurality of projection angles, a plurality of reference image detector count maps corresponding to each of the plurality of projection angles are generated. The method according to claim 11, including the method described in claim 11.

13. When the first projection angle is not one of the plurality of projection angles including the reference detector count map, obtaining the reference detector count value associated with one or more reference pixels from the second region of the first reference image is: The method according to claim 12, comprising estimating the reference detector count value by performing (i) an interpolation function, (ii) an extrapolation function, or (iii) a polynomial curve approximation function.

14. The method according to claim 10, wherein the plurality of projection angles include a range of angles from approximately -60 degrees to approximately +60 degrees with respect to the patient's breast.

15. The method according to claim 10, wherein calculating the AEC calculated dose includes multiplying the scout X-ray dose by the ratio between the average reference detector count value and the average detector count value and a global scaling coefficient.

16. The method according to claim 10, wherein the first projection angle is based on the current position of the tomosynthesis system prior to obtaining the scout image.

17. The method according to claim 16, wherein the current position is different from an angle of 0 degrees with respect to the patient's breast.

18. The method according to claim 10, further comprising obtaining a scout image of the patient's breast at a second projection angle different from the first projection angle.

19. Identifying the densest portion of the patient's breast is, The gain map associated with the first projection angle is applied to the scout image to compensate for the angular effect, Identifying pixels within a pre-identified central region that includes the lowest detector count value. The method according to claim 10, including the method described in claim 10.

20. A method for performing a calibration operation associated with automatic irradiation control (AEC) operation using a tomosynthesis system, wherein the method is: Obtaining multiple reference images of a human body model at multiple projection angles, wherein each of the multiple reference images includes multiple reference image pixels, For each of the aforementioned multiple reference images, a plurality of reference image detector count maps corresponding to each of the aforementioned multiple reference images are generated by editing the associated plurality of reference image pixels and the corresponding reference image detector count values. The storage of the aforementioned multiple reference image detector count maps, Obtaining a scout image of the patient's breast at the first projection angle by emitting a scout X-ray dose toward the patient's breast using the tomosynthesis system, wherein the scout image includes a plurality of pixels, and each of the plurality of pixels is associated with a detector count value from among a plurality of detector count values. Identifying a first region on the scout image to correspond to the densest part of the patient's breast, The average detector count value is calculated by averaging the one or more detector count values ​​corresponding to one or more pixels in the first region, Identifying a second region on a first reference image associated with a first projection angle, wherein the second region corresponds to a location on the first reference image that matches the location of the first region on the scout image, the first projection angle is one of a plurality of projection angles, and the first reference image is one of the plurality of reference images. Obtaining one or more reference detector count values ​​associated with one or more reference pixels in the second region of the first reference image, The average reference detector count value is calculated by averaging the one or more reference detector count values. Based on the ratio between the average reference detector count value and the average detector count value, the AEC calibration dose to be used in tomosynthesis scanning is calculated. The radiation dose for tomosynthesis sweeping at multiple projection angles in the patient's breast is set to the AEC calibration dose. Methods that include...

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