Method and system for an integrated phantom system

Abstract

an imaging system (200) including a gantry (322) including a radiation source (302) and a detector (314); a housing (306) positioned within the gantry near the radiation source; and a slab phantom set (304) positioned within the housing, the slab phantom set including at least one slab phantom (324, 326), the slab phantom set being configured such that at least one slab phantom of the slab phantom set is independently movable, and one or more slab phantoms of the at least one slab phantom of the slab phantom set can be selectively positioned in a path (312) of a radiation beam (308) between the radiation source and the detector. Effect: One or more slab phantoms can be positioned more quickly and accurately, making the calibration process more efficient.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION Embodiments of the subject matter disclosed herein relate to diagnostic medical imaging, and more particularly to a computed tomography imaging setup with an integrated phantom assembly. [Background technology]

[0002] In computed tomography (CT imaging systems), a beam of electrons generated by a cathode is directed toward a target inside an x-ray tube. The electrons strike the target, producing a fan- or cone-shaped x-ray beam that is directed toward the object being examined (such as a patient). After the x-rays are attenuated by the object, they strike an array of radiation detectors. Each detector element generates an electrical signal, which is used to reconstruct an image of the object. Each electrical signal corresponds to a voxel / pixel in the image.

[0003] Image quality in terms of resolution, contrast-to-noise ratio, and other measures depends on the alignment of each detector element in the detector array. Misalignment of detector elements can increase the number of artifacts in the image and / or degrade the image quality. A calibration process can be periodically performed on the system to obtain projection data for materials that simulate the densities of various human tissues. The calibration process can include performing an x-ray scanning procedure on an object called a phantom. Physical misalignment of the phantom during the calibration process can result in an inaccurate calibration of the CT system. Summary of the Invention

[0004] Various methods and systems are provided for a slab phantom set for an imaging system. The imaging system includes a gantry including a radiation source and a detector. A housing is disposed within the gantry near the radiation source. The housing contains a slab phantom set including at least one slab phantom. The slab phantom set is configured such that at least one slab phantom of the slab phantom set is independently movable, and one or more of the at least one slab phantom of the slab phantom set is selectively positioned on a path of a radiation beam between the radiation source and the detector.

[0005] It should be understood that the foregoing summary is provided to introduce in a simplified form selected concepts that are further described in the detailed description. The foregoing summary is not intended to identify key or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims. Moreover, the claimed subject matter is not limited to implementations that solve shortcomings noted above or anywhere in this disclosure. [Brief explanation of the drawings]

[0006] The invention can be better understood from the following description of non-limiting embodiments, taken in conjunction with the accompanying drawings, in which: [Figure 1] 1 shows a diagram of an imaging system according to one embodiment of the present invention; [Figure 2] 1 is a block schematic diagram of an imaging system including a gantry that houses a radiation source, a detector, a beam filtering device, and a housing positioned near the radiation source. [Figure 3] 3 illustrates the configuration of the imaging system of FIG. 2, showing the beam filtering device and elements of the slab phantom set housed in a housing. [Figure 4]3 illustrates the configuration of the imaging system of FIG. 2, showing elements of the beam filtering device housed within the beam filtering device and the slab phantom set positioned within the housing. [Figure 5] The configuration of the imaging system is shown in Figure 4, showing the slab phantoms of the slab phantom set positioned in the path of the X-ray beam emitted by the radiation source. [Figure 6] FIG. 3 is a side view showing the configuration of the imaging system of FIG. 2. [Figure 7A] 3 shows a side view of the imaging system configuration of FIG. 2, illustrating various bowtie filters of the beam filtering device and / or slab phantoms of the slab phantom set positioned in the path of the x-ray beam. [Figure 7B] 3 shows a side view of the imaging system configuration of FIG. 2, illustrating various bowtie filters of the beam filtering device and / or slab phantoms of the slab phantom set positioned in the path of the x-ray beam. [Figure 8A] 3 illustrates the configuration of the imaging system of FIG. 2, showing the beam filter device and housing containing the slab phantom of the slab phantom set. [Figure 8B] 3 illustrates the configuration of the imaging system of FIG. 2, showing the beam filter device and housing containing the slab phantom of the slab phantom set. [Figure 9] 3 illustrates the configuration of the imaging system of FIG. 2, showing how one or more slab phantoms of a set of slab phantoms can be moved by a single motor. [Figure 10] 3 is a side view of the imaging system of FIG. 2, showing how the housing is configured to be selectively positioned in the path of the x-ray beam via a hinge. [Figure 11] FIG. 11 is a side view of the configuration of FIG. 10. [Figure 12]3 illustrates a configuration of the imaging system of FIG. 2, showing how the housing is configured to be selectively positioned in the path of the x-ray beam through a linear track. [Figure 13] 1 shows a flowchart of a method for performing a calibration procedure for an imaging system. DETAILED DESCRIPTION OF THE INVENTION

[0007] The following description relates to various embodiments of an X-ray imaging system. Some imaging systems, such as computed tomography (CT) or photon-counting computed tomography (PCT) systems, require periodic calibration (e.g., daily or weekly calibration scans) to compensate for gain variations due to hardware, such as changes in the focal spot position of the X-ray tube or radiation degradation of the detector. Furthermore, PCT or CT systems can acquire spectral information, which can be used to generate reference material differentiation (BMD) images. Therefore, when calibrating a PCCT system, it may be necessary to acquire calibration projection data that simulates the materials and material thicknesses of the human body. Therefore, phantoms for calibrating PCCT systems can include several different materials, such as polyvinyl chloride (PVC) and polyethylene (PE). Several types of phantoms, such as slab phantoms, step phantoms, and pillar phantoms, can be used for calibration.

[0008] Calibration using slab phantoms often requires the selection of slabs of different thicknesses, densities, and / or materials to construct a single phantom for use in the calibration scan protocol. These slabs are placed in a bore and attached to the table, typically via an accessory slot in the front of the table. The process of constructing such slab phantoms and positioning them within the imaging system is time-consuming and prone to human error (e.g., positioning, slab selection, etc.). Furthermore, slab phantoms containing slabs of multiple types of materials and densities are often large, heavy, and physically cumbersome to move. Furthermore, large slabs occupy facility storage space required for storing other materials and consumables.

[0009] Accordingly, systems and methods are provided herein that at least partially address these issues. In particular, systems and methods for integrated phantom systems are provided herein. The integrated phantom system disclosed herein includes a slab phantom stored within the gantry of an imaging system. For example, a slab phantom set can be stored within a beam filtering device (e.g., a collimator housing that also stores filters, such as bowtie filters, used in diagnostic protocols) or in a separate housing near the radiation source. Each slab phantom of the set can be individually operated to move into the field of view of the X-ray source (e.g., the path from the radiation source to the detector) based on a selected calibration protocol, thereby reducing the time an operator spends manually selecting multiple slabs and assembling the phantom. Furthermore, because the housing in which the slab phantoms are located is located near the radiation source of the imaging system, the field of view intersected by the phantoms can be reduced, thereby reducing the size and overall footprint of the phantom slabs. The slab phantom can be automatically moved into and out of the x-ray beam, allowing for faster and more accurate positioning of one or more slab phantoms and streamlining the calibration process.

[0010] The systems and methods disclosed herein are described, by way of example, with reference to the figures: Figures 1 and 2 show exemplary imaging systems, Figures 3-12 show various configurations of integrated slab phantom systems for the imaging systems of Figures 1-2, and Figure 13 shows a flow chart illustrating a method for slab selection for an integrated phantom system.

[0011] FIG. 1 illustrates an exemplary CT system 100. In one example, the CT system 100 may be a PCCT system. In particular, the CT system 100 is configured to image a subject 112 (such as a patient, an inanimate object, one or more manufactured parts, and / or a foreign object (such as a dental implant, a stent, and / or a contrast agent present within the body or the subject)) positioned on a table 114. The table 114 may be motorized and selectively movable. In one embodiment, the CT system 100 includes a gantry 102, which may further include at least one X-ray radiation source 104 configured to project an X-ray beam 106 used to image the subject 112. The X-ray radiation source 104 includes an X-ray tube and a target. The X-ray tube generates X-rays by accelerating and focusing a high-energy electron beam onto a rotating target. As individual electrons strike the target, the energy released upon interaction with target atoms generates X-ray photons isotropically in a polychromatic spectrum, with the maximum energy of the X-ray photons matching the maximum energy of the incident electrons. The X-ray photons leave the X-ray tube and pass through a window that defines the X-ray beam. The beam is then collimated and tuned using collimator blades and filters.

[0012] Specifically, the radiation source 104 is configured to project an x-ray beam 106 toward a detector array 108 located on the opposite side of the gantry 102. Although a single radiation source 104 is shown in Figure 1, in certain embodiments, multiple radiation sources may be employed to project multiple x-ray beams 106 at different energy levels to acquire projection data corresponding to the object 112. The radiation source may include an x-ray target made of graphite and metal.

[0013] In certain embodiments, the CT system 100 further includes an image processor unit 110 having one or more processors configured to reconstruct an image of a target volume of the object 112 using an iterative image reconstruction method or an analytical image reconstruction method. For example, the image processor unit 110 may use an analytical image reconstruction method (such as filtered back projection (FBP)) to reconstruct an image of the target volume of the object 112. In another example, the image processor unit 110 may use an iterative image reconstruction method (such as advanced statistical iterative reconstruction (ASIR), conjugate gradient (CG), maximum likelihood expectation maximization (MLEM), model-based iterative reconstruction (MBIR), etc.) to reconstruct an image of the target volume of the object 112.

[0014] 2 illustrates an exemplary imaging system 200 similar to the CT system 100 of FIG. 1. The imaging system 200 includes at least some of the elements of the CT system 100. In one embodiment, the system 200 includes a detector array 108. The detector array 108 further includes a plurality of detector elements 202 that sense the x-ray beam 106 passing through an object 112 (e.g., a patient) and acquire corresponding projection data. In one embodiment, the detector array 108 can be fabricated in a multi-slice configuration including multiple rows of cells or detector elements 202. In such a configuration, one or more additional rows of detector elements 202 are arranged in a parallel configuration to acquire projection data.

[0015] The beam filtering device 240 can be mounted within the gantry 102 between the radiation source 104 and the subject 112. The beam filtering device 240 can have components that move in and out of the beam in the z-direction while the beam is emitted substantially in the y-direction. In some examples, the beam filtering device 240 can be configured to store one or more filters (e.g., bowtie filters configured for use in diagnostic protocols) and one or more slab phantoms configured for use in calibration protocols. The beam filtering device 240 can perform the function of a pre-collimator (filtering and collimating the beam for diagnostic imaging) and / or filtering the beam for other purposes (e.g., calibration). In some embodiments, a housing 242 can be positioned adjacent to and separate from the beam filtering device 240, with the beam filtering device 240 storing one or more filters (e.g., bowtie filters) and the housing 242 storing one or more phantom slabs. 3 may be positioned directly adjacent to the beam filtering device 240 within the rotating portion of the gantry 102 of the imaging system 200. In either example, the phantom slab may be moved in and out of the beam according to a selected calibration protocol, separate from one or more filters that may be moved in and out of the beam based on a selected diagnostic protocol.

[0016] In certain embodiments, system 200 is configured to be able to move through different angular positions around object 112 to acquire desired projection data. Thus, gantry 102 and gantry-mounted components (such as radiation source 104, beam filtering device 240, housing 242, and detector array 108) may be configured to rotate about center of rotation 206 to acquire projection data at different energy levels, for example. Alternatively, in embodiments in which the projection angle relative to object 112 varies with time, the mounted components may be configured to move along a general curve rather than along a portion of a circle.

[0017] In one embodiment, imaging system 200 includes a control mechanism 208 that controls the movement of components, such as the rotation of gantry 102 and the operation of x-ray radiation source 104. In certain embodiments, control mechanism 208 further includes an x-ray controller 210 configured to provide power and timing signals to radiation source 104. Additionally, control mechanism 208 includes a gantry motor controller 212 configured to control the rotational speed and / or rotational position of gantry 102 based on imaging requirements.

[0018] In certain embodiments, the control mechanism 208 further includes a data acquisition system (DAS) 214 that samples analog data received from the detector elements 202 and converts the analog data to digital signals for subsequent processing. The data sampled and digitized by the DAS 214 is transmitted to a computing device (also referred to as a processor) 216. In one example, the computing device 216 stores the data in a storage device 218. The storage device 218 may include, for example, a hard disk drive, a floppy disk drive, a compact disk read / write (CD-R / W) drive, a digital versatile disk (DVD) drive, a flash drive, and / or a solid-state storage drive.

[0019] Additionally, the computing device 216 provides commands and parameters to one or more of the DAS 214, the X-ray controller 210, and the gantry motor controller 212 to control system operation (e.g., data acquisition and / or data processing). In certain embodiments, the computing device 216 controls system operation based on operator input. The computing device 216 receives operator input, including, for example, commands and / or scan parameters, through an operator console 220 operably coupled to the computing device 216. The operator console 220 may include a keyboard or touch screen to enable an operator to specify commands and / or scan parameters.

[0020] 2 shows one operator console 220, multiple operator consoles may be coupled to system 200, for example, to input or output system parameters, request tests, and / or display images. Additionally, in certain embodiments, system 200 may be coupled through one or more configurable wired and / or wireless networks (such as the Internet and / or a virtual private network) to multiple displays, printers, workstations, and / or similar devices, located locally, remotely, or at entirely different locations, for example, within a facility or hospital.

[0021] In one embodiment, for example, system 200 includes or is coupled to a picture archiving and communication system (PACS) 224. In an exemplary implementation, PACS 224 is further coupled to remote systems (such as a radiology information system, a hospital information system, and / or an internal or external network (not shown)) to enable operators at different locations to provide commands and parameters and / or access image data.

[0022] The computing device 216 may use operator-supplied and / or system-defined commands and parameters to operate a table motor controller 226, which in turn may control the table 114. For example, the table 114 may be driven by a motor. The table motor controller 226 may activate the motor of the table 114 to move the table 114 so that the subject 112 is properly positioned within the gantry 102 to acquire projection data corresponding to a target volume of the subject 112.

[0023] As described above, DAS 214 samples and digitizes the projection data acquired by detector elements 202. Image reconstructor 230 then performs high-speed reconstruction using the sampled and digitized x-ray data. While image reconstructor 230 is shown as a separate entity in FIG. 2 , in certain embodiments, image reconstructor 230 may form part of computing device 216. Alternatively, image reconstructor 230 may not be present in system 200, and computing device 216 may perform one or more functions of image reconstructor 230. Furthermore, image reconstructor 230 may be located locally or remotely, and image reconstructor 230 may be operably connected to system 100 using a wired or wireless network. Notably, in one exemplary embodiment, the computing resources of a “cloud” network cluster may be used for image reconstructor 230.

[0024] In one embodiment, image reconstructor 230 stores the reconstructed image in storage device 218. Alternatively, image reconstructor 230 can transmit the reconstructed image to computing device 216 for generating patient information useful for diagnosis and evaluation. In certain embodiments, computing device 216 can transmit the reconstructed image and / or patient information to a display 232 communicatively coupled to computing device 216 and / or image reconstructor 230.

[0025] As described further herein with respect to FIGS. 3-13 , the imaging system 200 can be calibrated by performing one or more calibration scan protocols. A user can request a calibration scan protocol through the operator console 220. The computing device 216 can identify the requested calibration scan protocol and determine a slab phantom corresponding to the identified calibration scan protocol. The slab phantom can include one or more slab phantoms of a slab phantom set housed in the beam filtering device 240 and / or the housing 242. The computing device 216 can identify a subset of slabs of the slab phantom set incorporated in the housing 242 and / or the beam filtering device 240 of the imaging system 200 that form the slab phantom corresponding to the identified calibration scan protocol. The computing device 216 can actuate one or more motors coupled to the identified subset of slabs to move the subset of slabs into the path of the radiation beam (e.g., the x-ray beam 106). Thus, the imaging system 200 can perform a calibration scan of the slab phantom.

[0026] FIG. 3 illustrates a configuration 300 of the imaging system 200 of FIG. 2 , in which the gantry 102 houses the radiation source 104, the beam filtering device 240, the housing 242, and the detector array 108. In the configuration illustrated in FIG. 3 , the housing 242 and the beam filtering device 240 are combined into a single housing 306 that includes elements of the beam filtering device 240 and elements of the housing 242. For example, a slab phantom set 304 is disposed within the single housing 306 of the imaging system 200, as described further herein. Additionally, in this illustrated embodiment, one or more exemplary bowtie filters 320 are disposed within the single housing 306. Alternatively, one or more exemplary bowtie filters 320 may be disposed within the beam filtering device 240, as described further with respect to FIGS. 4-12 . In this illustrated example, the phantoms of the slab phantom set 304 and other filters (e.g., bowtie filters) of the imaging system 200 move parallel to the x-axis. Alternatively, the slab phantom set 304 and single housing 306 can be positioned so that the slab phantom set 304 moves parallel to the z-axis. An axis system 299 is shown in Figure 3, where the x-axis is the horizontal axis, the y-axis is the vertical (e.g., gravity) axis, and the z-axis is the longitudinal axis (e.g., the direction into and out of the gantry).

[0027] The configuration 300 of the imaging system 200 includes an X-ray source 302 (e.g., radiation source 104 of FIGS. 1-2) configured to emit an X-ray beam (e.g., X-ray beam 106) 308. The X-ray beam 308 travels along a path 312 from the X-ray source 302 to a detector 314 (e.g., detector array 108) of the imaging system 200. The detector 314 is disposed within a rotating portion 334 of a gantry housing 322 (e.g., gantry housing 102 of FIGS. 1 and 2). The detector 314 is disposed on an opposite side of a bore 316 of the gantry housing 322 from the X-ray source 302. The rotating portion 334 further houses the X-ray source 302 and a single housing 306 that houses a slab phantom set 304. The single housing 306 is positioned within the rotating section 334 so as to be located near the x-ray source 302 , with the single housing 306 being in the path 312 of the x-ray beam 308 .

[0028] In the example of FIG. 3 , the unitary housing 306 is made of metal (e.g., aluminum). Alternatively, the housing may be made of an X-ray transparent material. The unitary housing 306 includes a first gap 336 on a first side 390 of the unitary housing 306 that is closer to the X-ray source 302, and a second gap 338 on a second side 392 of the unitary housing 306 that is opposite the first side 390. The first gap 336 and the second gap 338 are aligned (e.g., along the y-axis) such that the X-ray beam 308 passes through the first gap 336 and the second gap 338. The unitary housing 306 includes a collimator configured to condition and / or focus the X-ray beam 308. For example, the unitary housing 306 may include one or more bowtie filters 320. The one or more bowtie filters 320, when placed in the path 312 of the x-ray beam 308, are configured to modify one or more configurations of the x-ray beam, for example, to reduce the amount of radiation delivered to the patient's periphery. In some examples, one bowtie filter 320 is placed in the path of the x-ray beam 308. In some embodiments, two or more filters (e.g., additional bowtie filters 320, different filters) may be placed in the path of the x-ray beam 308 along with the one exemplary bowtie filter 320. The bowtie filters 320 are positioned in the single housing 306 on a first side 390 of the single housing 306. The bowtie filters 320 can be configured for use in a diagnostic imaging protocol, and can be moved into and out of intersection with the x-ray beam 308 during the diagnostic protocol. In contrast, the slab phantom set 304 can be configured for use in a calibration protocol, and can be moved into and out of intersection with the x-ray beam 308 during a calibration scan.

[0029] In the embodiment shown in FIG. 3 , the slab phantom set 304 is disposed in a single housing 306. The slab phantom set 304 includes multiple phantom slabs. As described herein, a slab phantom is a piece of material configured to mimic a particular density of human tissue (e.g., bone, blood, cerebral matter, etc.). Using known parameters of the slabs and the group of slabs forming a selected slab phantom, calibration of the imaging system 200 can be performed by comparing various outputs of a calibration scan with standard values. The slab phantom set 304 can include a first slab phantom 324 having a first thickness (the first thickness is a thickness parallel to the direction of the path 312 (e.g., parallel to the y-axis)). The first slab phantom 324 is formed of a first material. The slab phantom set 304 can further include a second slab phantom 326 having a second thickness (the second thickness is a thickness parallel to the direction of the path 312 (e.g., parallel to the y-axis)). The second slab phantom 326 is formed of a second material. The second thickness can be different from the first thickness. The second material can be different from the first material. The slab phantom set 304 can include additional slabs, each of which can be formed of the same and / or different material as the first and / or second material. In the example of FIG. 3 , the slab phantom set 304 includes six phantom slabs. Different combinations of the six available slabs can be preprogrammed as slab phantoms for the system, thereby allowing selection of the first slab phantom to trigger selection of a first subset of available slabs. Each of the additional slabs can have a thickness parallel to the y-axis that is greater than, less than, and / or equal to the first and / or second thicknesses. Each of the additional slabs can have a different thickness.The spacing between the slabs of the slab phantom set 304 (e.g., the spacing in the y-axis direction between the first slab phantom 324 and the second slab phantom 326) allows multiple slabs to be stacked along the y-axis in the path 312 of the x-ray beam 308 to create a single filtering phantom. Exemplary combinations of slab phantoms are shown in Figures 5 and 7B.

[0030] The slab phantom set 304 is disposed on a second side 392 of the unitary housing 306, opposite the first side 390. The unitary housing 306 is disposed such that the bowtie filter 320 is close to the X-ray source 302 (e.g., no components of the unitary housing 306 are between the bowtie filter 320 and the X-ray source 302). In other words, the slab phantom set 304 and the bowtie filter 320 can be stacked vertically in the y-axis. The slab phantom set 304 is disposed away from the X-ray source 302, with the bowtie filter 320 and the wall of the unitary housing 306 on the first side 390 of the unitary housing 306 positioned between the slab phantom set 304 and the X-ray source 302. Thus, the slab phantom set 304 and the bowtie filter can be incorporated into the same housing, allowing the slab to be stored within the imaging system rather than external to the imaging system.

[0031] Furthermore, by placing the slab phantom set 304 closer to the X-ray source 302 than the detector 314 (e.g., on the same side of the bore 316 as the X-ray source 302, but opposite the detector), the size of each slab in the slab phantom set 304 can be reduced compared to conventional slab phantoms. For example, in a conventional calibration procedure for calibrating an imaging system (e.g., imaging system 200), one or more slab phantoms can be placed in the path 312 of the X-ray beam 308 by placing one or more slabs on an imaging plane (e.g., table 114). The imaging plane is inserted into the bore 316. As shown in FIG. 3 , the width of the X-ray beam 308 within the bore 316 is wider than the width of the X-ray beam 308 near the X-ray source 302 outside the bore 316. For example, a first width 332 of the X-ray beam 308 within the bore 316 is wider than a second width 330 of the X-ray beam 308 passing through the single housing 306. To image the entire selected slab phantom (e.g., to allow the X-ray beam 308 received by the detector 314 to pass through the slab phantom), the width of the slab (e.g., width parallel to the x-axis) moving across the X-ray beam 308 is configured to be at least equal to and / or wider than the width of the X-ray beam 308 at the location of the phantom in the X-ray beam 308. Thus, by positioning the slab phantom set 304 and the slabs of the slab phantom set 304 closer to the X-ray source 302, the width of each slab can be narrower than the width of a slab phantom positioned further in the path 312 of the X-ray beam 308 (e.g., positioned closer to the detector 314) to achieve the same desired filtering. Thus, the footprint and weight of each slab phantom (and of the slab phantom set 304) can be reduced. Furthermore, because the slab phantom set 304 is stored in a single housing 306 integrated into the imaging system 200, the complexity, space, and labor requirements for storing the slab phantom set 304 can be reduced and / or eliminated.7-13, one or more slab phantoms of slab phantom set 304 may be automatically moved into and / or out of X-ray beam 308 during different calibration procedures of imaging system 200. This may further reduce the burden on a user to manually move and / or manually adjust the position of one or more slab phantoms in the path 312 of X-ray beam 308 (e.g., on table 114). Thus, the time required to perform a calibration procedure may be reduced. Furthermore, automatically positioning a slab phantom in X-ray beam 308 in response to selection of one or more calibration procedures may improve the accuracy of the calibration of the imaging system.

[0032] The geometric configuration of a single housing 306 containing a slab phantom set 304 and one or more bowtie filters 320 shown in FIG. 3 can be implemented in a CT imaging system having a detector 314 with a relatively short length in the x-direction. In this illustrated configuration, the bowties 320 and slab phantom set 304 move in the x-direction to intersect with the x-ray beam 308. In other configurations, the bowties 320 and slab phantom set 304 move in the z-direction to intersect with the x-ray beam 308. Due to limited physical space available in a CT imaging system, moving the bowties 320 and slab sets 304 in the z-direction is preferred for detectors 314 with a medium to large range. This is because the required size of the bowtie filters 320 and slab sets 304 to completely cover the x-ray beam 308 would not provide the physical space in the gantry 102.

[0033] 4-12 , one or more slab phantoms of slab phantom set 304 can be independently positioned in and / or moved out of path 312 of x-ray beam 308. In FIG. 3 , the slab phantoms of slab phantom set 304 are shown positioned on either side of x-ray beam 308 (e.g., not positioned in x-ray beam 308). One or more motors (not shown in FIG. 3 ) are coupled to one or more slabs of slab phantom set 304 and / or to bowtie filter 320, and the one or more motors are configured to independently move the slabs (e.g., slab phantoms, bowtie filters, etc.) into and / or out of path 312 of x-ray beam 308. Thus, imaging system 200 includes a single holder (e.g., housing 306) that houses a slab phantom (e.g., slab phantom set 304) and a pre-collimator (e.g., bowtie filter 320) used to calibrate imaging system 200.

[0034] FIG. 4 illustrates a configuration 400 of the imaging system 200 of FIGS. 2-3 in which components of the beam filtering device 240 (e.g., one or more bowtie filters 320) are housed in the beam filtering device 240 and the slab phantom set 304 is housed in a housing 242. In the configuration 400, the housing 242 is a separate structure from the beam filtering device 240. The configuration 400 may include at least some of the same components as the imaging system 200 of FIGS. 2-3, which are labeled in FIG. 4 and will not be described again for brevity. The beam filtering device 240 includes a first gap 436 on a first side 390 of the beam filtering device 240 near the X-ray source 302. The housing 242 includes a second gap 438 on a second side 392 opposite the first side 390 of the housing 242. Both the housing 242 and the beam filtering device 240 include a third gap 440 on each side where the housing 242 and the beam filtering device face each other. The first gap 436, the second gap 438, and the third gap 440 are aligned (e.g., along the y-axis) such that the x-ray beam 308 passes through the first gap 436, the second gap 438, and the third gap 440. The housing 242 can be rigidly positioned in the path 312 of the x-ray beam 308. For example, the housing 242 can be coupled to the beam filtering device 240 by, for example, welding, bolts, clamps, and / or other rigid fasteners. In other embodiments, the housing 242 can be rigidly coupled to another portion of the rotating portion 334 of the gantry housing 322, rigidly positioning the housing 242 in the path 312 of the x-ray beam 308. In other embodiments, the housing 242 can be selectively coupled to the beam filtering device 240, as described with respect to FIGS. 9-12 . The beam filtering device 240 is disposed between the housing 242 and the x-ray source 302 .7-13, the multiple slabs of the slab phantom set 304 can be independently and selectively positioned in the path 312 of the x-ray beam 308 during calibration operations of the imaging system 200. Thus, the x-ray beam 308 can pass through a bowtie filter 320 before passing through one or more filters of the slab phantom set 304.

[0035] FIG. 5 shows a view 500 of the configuration 400 of FIG. 4. In the view 500 of FIG. 5, a slab phantom of the slab phantom set 304 is positioned in the path 312 of the x-ray beam 308. In the example of FIG. 5, the slab phantom set 304 includes four slabs. Each slab phantom of the first slab phantom 324, the second slab phantom 326, the third slab phantom 524, and the fourth slab phantom 526 of the slab phantom set 304 may have the same width in a direction perpendicular to the path 312 of the x-ray beam 308 (e.g., in a direction parallel to the X-axis). The width of each slab phantom is configured to be at least equal to or wider than the width of the x-ray beam 308 at the position of the slab phantom. For example, first width 530 of first slab phantom 324 is wider than second width 532 of x-ray beam 308 at the location of first slab phantom 324. In this manner, first slab phantom 324 is positioned completely in path 312 of x-ray beam 308, and the entire x-ray beam 308 passes through first slab phantom 324 on path 312 from x-ray source 302 to detector 314.

[0036] 3, one or more of the slabs in the slab phantom set 304 may be formed of the same material or different materials. Furthermore, one or more of the slab phantoms in the slab phantom set 304 may have the same thickness or different thicknesses in a direction parallel to the path 312 of the x-ray beam 308 (e.g., parallel to the y-axis). Thus, different slabs may be selected or predetermined to be part of a given slab phantom.

[0037] 7-13 , the multiple slabs of the slab phantom set 304 can be independently and selectively positioned in the path 312 of the x-ray beam 308 during calibration operations of the imaging system 200. For example, as shown in FIG. 5 , one or more of the multiple slabs of the slab phantom set 304 can be simultaneously positioned in the path 312 of the x-ray beam 308. The bowties 320 and slab sets 304 move in the z-direction to move in and out of the x-ray beam 308. Due to limited physical space on the rotating gantry 102, a configuration in which the bowties 320 and slab sets 304 move in the z-direction is preferred when the detectors 314 span a moderate to wide range in the x-direction.

[0038] FIG. 6 shows a side view 600 of the configuration of imaging system 200 of FIG. 2. Some components of imaging system 200 have been omitted from side view 600 for clarity. Some components of imaging system 200 described with respect to FIGS. 3-5 are included in the configuration of FIG. 6 and will not be described again for brevity. Side view 600 of FIG. 6 shows first slab phantom 324, second slab phantom 326, third slab phantom 524, and fourth slab phantom 526 of slab phantom set 304. Slab phantom set 304 may further include fifth slab phantom 624, sixth slab phantom 626, and seventh slab phantom 628. Each of the multiple slab phantoms in slab phantom set 304 may have a different thickness in a direction along path 312 of x-ray beam 308 (e.g., a direction parallel to the y-axis). Additionally, one or more of the slabs in the slab phantom set 304 may be formed from different materials configured to simulate different human tissues.

[0039] Each slab may have a corresponding motor and drive shaft. The motor may actuate the slab's drive shaft to move the slab across the path 312 based on a selected calibration scan protocol, as described further below. The configuration 400 includes one or more bowtie filters 320. As shown in FIG. 6 , the beam filtering device 240 may include three bowtie filters 320 and two apertures 618. The function of the apertures 618 is to increase or decrease the coverage of the x-ray beam 308 in the z-direction. The collimator apertures 618 are configured to direct the x-ray beam 308 along the path 312 from the x-ray source 302 to the detector 314. As mentioned above, the bowtie filters 320 may be configured to change the shape or size of the x-ray beam 308 as it passes through the subject during diagnostic image acquisition. In other embodiments, the beam filtering device 240 may include more or fewer bowtie filters 320 and / or apertures 618 than those shown. The bowtie filter 320 is disposed on a first side 390 of the beam filtering device 240, and the aperture 618 is disposed on a second side 392 of the beam filtering device 240. The aperture 618 may be movably disposed within the beam filtering device 240 using, for example, a drive system (such as a motor and drive shaft (not shown)). Each bowtie filter may be coupled to the drive system including the motor and drive shaft. For example, each bowtie filter 320 may be attached to a drive shaft of a motor configured to selectively and / or independently move the bowtie filter 320 into and / or out of the path 312 of the X-ray beam 308. For example, the first motor 602 may have a first drive shaft 606 extending therefrom. The first bowtie filter 320 a may be attached to and / or coupled to the first drive shaft 606. The first motor 602 can be actuated to selectively move the first bowtie filter 320 a into and / or out of the path 312 of the x-ray beam 308 .The second motor 604 can have a second drive shaft 608 extending therefrom. The second bowtie filter 320 b and the third bowtie filter 320 c can be attached to and / or coupled to the second drive shaft 608. The second motor 604 can be actuated to selectively move the second bowtie filter 320 b and / or the third bowtie filter 320 c into and / or out of the path 312 of the X-ray beam 308.

[0040] Similarly, each of the various slabs in slab phantom set 304 is coupled to a drive system including a motor having a drive shaft, and the motor can move the corresponding slab so that the corresponding slab intersects path 312 based on a selected protocol. For example, a first protocol can indicate that a first slab phantom should be imaged for a calibration scan. The first slab phantom can include a first subset of slabs in slab phantom set 304. When the first protocol is selected, the respective drive systems corresponding to the first subset of slabs actuate the first subset of slabs to move the first subset of slabs along path 312, but do not actuate other slabs not included in the first subset of slab phantom set 304 to move. In this manner, the first slab phantom can be imaged for calibration of the imaging system according to a selected calibration scan protocol. When a second, different calibration protocol is selected, a corresponding, different drive system can actuate a second subset of slab phantom set 304 to move along path 312, where the second subset of slabs forms a second slab phantom corresponding to the selected second calibration protocol.

[0041] In some examples, the selected calibration protocol may include a bowtie filter, and therefore the motors and drive shafts corresponding to the bowtie filter (e.g., first motor 602 and second motor 604 and first drive shaft 606 and second drive shaft 608) may be activated during the calibration protocol. In other examples, the selected calibration protocol may not include the bowtie filter, and therefore the bowtie filter is not activated to move in a path during the calibration scan. Similarly, the motors and drive shafts corresponding to slab phantom set 304 are not activated during the diagnostic imaging protocol because the phantoms are intended for calibration purposes, not diagnostic purposes.

[0042] 7A and 7B illustrate side views 700 of the configuration shown in FIG. 6 of imaging system 200. The numerals of some components have been omitted from one or more of the side views 700 of FIGS. 7A and 7B for clarity. It should be understood that the same elements are shown in each of the side views 700 of FIGS. 7A and 7B. The side views 700 illustrate various combinations of bowtie filters and / or slab phantoms selectively positioned in the path 312 of the x-ray beam 308. The diagrams of FIGS. 7A and 7B illustrate how the slabs of the slab phantom set 304 and the bowtie filters 320 can be independently moved into and / or out of the path of the x-ray beam 308, thereby allowing the slabs to be used individually and / or in combination with other slab phantoms and / or bowtie filters 320. The slab and bowtie filter 320 is described herein as being moved into and / or out of the x-ray beam 308 by a motor with a drive shaft. Other types of drive mechanisms may be used to selectively and independently move the filter into and / or out of the x-ray beam 308 without departing from the scope of this disclosure.

[0043] In the first diagram 702, the first motor 602 is actuated, causing the first drive shaft 606 to extend and position the first bowtie filter 320a in the path 312 of the x-ray beam 308. The motors coupled to the slabs of the slab phantom set 304 are not actuated, and therefore none of the slabs of the slab phantom set 304 are positioned in the path 312 of the x-ray beam 308. The first diagram 702 is an example of a configuration of the imaging system 200 during a conventional diagnostic imaging procedure (e.g., an imaging procedure that is not a calibration procedure of the imaging system). By placing the first bowtie filter 320a in the path 312 of the x-ray beam 308, the first bowtie filter 320a can be used to change the size, shape, or configuration of the beam during a diagnostic scan performed by the imaging system.

[0044] The imaging system 200 can include a third motor 712 having a third drive shaft 705 extending therefrom. A fifth slab phantom 624 is disposed on and / or coupled to the third drive shaft 705. In the second diagram 704, the third motor 712 is actuated, causing the third drive shaft 705 to extend and position the fifth slab phantom 624 in the path 312 of the x-ray beam 308. The motors coupled to the other slabs in the slab phantom set 304 are not actuated, and therefore the first slab phantom 324, the second slab phantom 326, the third slab phantom 524, the fourth slab phantom 526, the sixth slab phantom 626, and the seventh slab phantom 628 are not positioned in the x-ray beam 308. Additionally, first motor 602 and second motor 604 are not operating, and therefore first bowtie filter 320a, second bowtie filter 320b, and third bowtie filter 320c are not positioned in x-ray beam 308. Therefore, second diagram 704 shows an exemplary configuration in which a single slab is positioned in x-ray beam 308. Second diagram 704 can be configured when performing a first calibration procedure of imaging system 200.

[0045] The imaging system 200 may further include a fourth motor 714 having a fourth drive shaft 716 extending therefrom. A sixth slab phantom 626 is disposed on and / or coupled to the fourth drive shaft 716. In the third diagram 706, the fourth motor 714 is actuated to extend the fourth drive shaft 716 and position the sixth slab phantom 626 in the path 312 of the x-ray beam 308. Additionally, the third motor 712 is actuated to operate the third drive shaft 705 to position the fifth slab phantom 624 in the path 312 of the x-ray beam 308. The motors coupled to the other slab phantoms in slab phantom set 304 are not activated, and therefore first slab phantom 324, second slab phantom 326, third slab phantom 524, fourth slab phantom 526, and seventh slab phantom 628 are not positioned in x-ray beam 308. Furthermore, first motor 602 and second motor 604 are not activated, and therefore first bowtie filter 320a, second bowtie filter 320b, and third bowtie filter 320c are not positioned in x-ray beam 308. Thus, third diagram 706 illustrates an exemplary configuration in which multiple slabs forming a single slab phantom are positioned in x-ray beam 308. In the example of third diagram 706, the phantom slabs positioned in x-ray beam 308 are housed on and extend from the same side of housing 242 (e.g., on first side 790 of x-ray beam 308). The third diagram 706 can be configured when performing a second calibration procedure of the imaging system 200, the second calibration procedure being different from the first calibration procedure that uses the second diagram 704.

[0046] The imaging system 200 can include a fifth motor 718 having a fifth drive shaft 720 extending therefrom. A seventh slab phantom 628 is disposed on and / or coupled to the fifth drive shaft 720. In the fourth diagram 708, the fifth motor 718 is actuated to extend the fifth drive shaft 720, thereby positioning the seventh slab phantom 628 in the path 312 of the x-ray beam 308. Additionally, the third motor 712 is actuated to extend the third drive shaft 705, thereby positioning the fifth slab phantom 624 in the path 312 of the x-ray beam 308. The motors coupled to the other slabs in slab phantom set 304 are not activated, and therefore first slab phantom 324, second slab phantom 326, third slab phantom 524, fourth slab phantom 526, and sixth slab phantom 626 are not positioned in x-ray beam 308. Furthermore, first motor 602 and second motor 604 are not activated, and therefore first bowtie filter 320a, second bowtie filter 320b, and third bowtie filter 320c are not positioned in x-ray beam 308. Thus, fourth diagram 708 illustrates an exemplary configuration in which multiple slabs forming the slab phantoms are positioned in x-ray beam 308. In the example of the fourth diagram 708, the slab positioned in the X-ray beam 308 is housed on opposite sides of the housing 242 (e.g., a first side 790 relative to the X-ray beam 308 and a second side 792 opposite the first side 790 along the z-axis relative to the X-ray beam 308) and extends from opposite sides of the housing 242. The fourth diagram 708 can be configured when performing a third calibration procedure of the imaging system 200, the third calibration procedure being different from the first calibration procedure using the second diagram 704 and the second calibration procedure using the third diagram 706.

[0047] By independently and selectively placing one or more slabs of slab phantom set 304 in the path of the x-ray beam, different combinations of slabs can be used to perform calibration procedures and / or diagnostic imaging procedures. Different combinations can form different slab phantoms having different material, density, and thickness configurations and arrangements configured to simulate different types of human tissue. For example, a first slab phantom can include a selected group of slabs in a particular configuration configured to simulate a human torso, while a second slab phantom can include a different selected group of slabs in a different configuration configured to simulate a human brain. In this manner, different slab phantoms that can be utilized in the system can be selected using the same slab set, rather than requiring multiple identical slabs to form different individual slab phantoms outside of the imaging system.

[0048] 8A and 8B show a configuration 800 of the imaging system 200 of FIG. 2 in which the beam filtering device 240 and housing 242 include a slab phantom of the slab phantom set 304. Some components of the imaging system 200 described with respect to FIGS. 3-7 are included in the configurations of FIGS. 8A-8B and will not be described again for brevity. Configuration 800 further illustrates how the slabs of the slab phantom set 304 and the bowtie filters 320 can be independently moved into and / or out of the path of the x-ray beam 308, and thus can be used individually and / or in combination with other slabs and / or bowtie filters 320 (as slab phantoms). The slabs and bowtie filters 320 are described herein as being moved into and / or out of the x-ray beam 308 by motors with drive shafts. Other types of drive mechanisms may be used to selectively and independently move the filters into the X-ray beam 308 and / or to selectively and independently move the filters out of the X-ray beam 308 without departing from the scope of the present disclosure.

[0049] The slabs of slab phantom set 304 are disposed in beam filtering apparatus 240, which also houses bowtie filter 320 and aperture 618. In addition to first bowtie filter 320, an eighth slab 824 is coupled to first drive shaft 606 of first motor 602. In addition to second bowtie filter 320b and third bowtie filter 320c, a ninth slab 826 is coupled to second drive shaft 608 of second motor 604. In first diagram 802, neither first motor 602 nor second motor 604 is operating, and therefore none of first bowtie filter 320a, second bowtie filter 320b, third bowtie filter 320c, eighth slab 824, or ninth slab 826 is disposed in x-ray beam 308. Each of the first motor 602 and the second motor 604 can be independently actuated to extend its drive shaft (e.g., first drive shaft 606 and second drive shaft 608) and independently position each of the filters and slabs attached to the shaft in the X-ray beam 308. For example, in the second diagram 804, the second motor 604 is actuated. The second motor 604 extends the second drive shaft 608 to a first position such that the ninth slab 826 is positioned in the X-ray beam 308. The second bowtie filter 320b and the third bowtie filter 320c are not positioned in the X-ray beam 308 when the second drive shaft 608 is in the first position. In the second diagram 804, the second bowtie filter 320b and the third bowtie filter 320c are positioned on the second side 792 of the X-ray beam 308 (e.g., on the same side as the first bowtie filter 320a and the eighth slab 824). By actuating the second motor 604 and adjusting the second drive shaft 608 to extend to another position (e.g., in a direction parallel to the z-axis), the third bowtie filter 320c and the second bowtie filter 320b can be switched into position with the X-ray beam 308. In this manner, the slab and bowtie filters can be positioned on the same drive shaft and within the same housing, thereby reducing the number of system components and the complexity of the system.

[0050] In third diagram 806 and fourth diagram 808, as described with respect to FIGS. 4-7B, housing 242 is coupled to beam filtering device 240, and additional slabs of slab phantom set 304 are positioned in housing 242. In third diagram 806, none of the motors on which the slabs and / or one or more bowtie filters are positioned are activated, and therefore the slabs and bowtie filters are not positioned in the path 312 of x-ray beam 308. In fourth diagram 808, second motor 604 is activated, extending second drive shaft 608 and positioning ninth slab 826 in x-ray beam 308. Additionally, fourth motor 714 is activated, extending fourth drive shaft 716 and positioning sixth slab phantom 626 in the path 312 of x-ray beam 308. In this manner, the slab disposed in the beam filtering device 240 and the slab disposed within the housing 242 are positioned in the path 312 of the x-ray beam 308. Thus, a slab phantom containing both a slab of the beam filtering device and a slab of the phantom housing can be imaged in a calibration scan without having to independently assemble the slab phantom outside of the imaging system.

[0051] FIG. 9 illustrates a configuration 900 of the imaging system 200 of FIG. 2, in which the housing 242 is configured to be selectively positioned in the path 312 of the x-ray beam 308. Some components of the imaging system 200 described with respect to FIGS. 3-8B are included in the configuration of FIG. 6 and will not be described again for brevity. In the example of FIG. 9, the beam filtering device 240 includes an aperture 618, a slab, and a bowtie filter. The eighth slab 824 and the first bowtie filter 320a can be disposed on the first drive shaft 606 of the first motor 602. The second bowtie filter 320b and the third bowtie filter 320c can be coupled to the second drive shaft 608 of the second motor 604.

[0052] In the first diagram 902, neither the motor nor the drive shaft is activated, and therefore neither the bowtie filter nor the slabs are positioned to intersect the beam. In the second diagram 904, the fifth motor 908, to which the tenth slab 910 and the eleventh slab 912 are coupled, is activated such that the fifth drive shaft 914 extends to a first position. In the first position, the eleventh slab 912 intersects the X-ray beam, but the tenth slab 910 does not.

[0053] In the third diagram 906, the fifth motor 908 is actuated to extend the fifth drive shaft 914 to a second position where the tenth slab 910 intersects the x-ray beam 308 but the eleventh slab 912 does not. In this manner, by using different positions of the drive shaft, a single drive shaft can be coupled to multiple slabs and selected slabs can be positioned to intersect the beam based on the position corresponding to the selected slab.

[0054] FIG. 10 shows a side view of a configuration 1000 of the imaging system of FIG. 2 , in which a housing is configured to be selectively positioned in the path 312 of the x-ray beam 308. In the configuration 1000, a slab phantom set 304 can be integrated into the housing 242. The housing 242 can be coupled to the beam filtering device 240 via a hinge 1002. By rotating the housing 242 about the hinge 1002, the housing 242 can be rotated from a first position 1004 to a second position 1006. In the first position 1004, the slab phantom set 304 is not positioned within the bore and therefore does not intersect with the x-ray beam. However, upon rotation to the second position 1006, the slab phantom set 304 is positioned to intersect with the x-ray beam. In this example, slabs in the set can be manually selected, and all slabs in the set can be imaged when all slabs in the set are in the second position 1006. In some embodiments, rotating the housing 242 about the hinge 1002 can further include removing the scan window before moving the housing into the path 312 of the x-ray beam 308 .

[0055] FIG. 11 shows a side view 1100 of the configuration 1000 of FIG. 10 . In the side view 1100, the beam filtering device 240 is separated from the housing 242, as described above. The housing 242 can be a hinged or rotating component that is stored within the rotating gantry during diagnostic protocols. In some embodiments, the housing 242 can be fixedly coupled to the beam filtering device 240 using fasteners 1102 when in the configuration shown at 1000. When a calibration protocol is selected, the housing 242 rotates adjacent to the beam filtering device 240. Motors and drive shafts can then move the different slabs into position to intersect the beam, as described above. In this manner, the slabs can be kept out of the way during diagnostic procedures, reducing the risk of artifacts or other interference, and the slabs can be moved into position for the calibration protocol. In some examples of the configuration 1000, the imaging system 200 includes a scan window 1108. The scan window 1108 can be removed before moving the housing 242 into the path 312 of the radiation beam by rotating the housing 242 about the hinge 1002 .

[0056] 12 illustrates a configuration 1200 of the imaging system of FIG. 2 in which the housing 242 is configured to be selectively positioned in the path 312 of the x-ray beam 308. In the configuration 1200, a sliding mechanism can be used to move the housing 242 into position for a calibration protocol. The sliding mechanism can include, by way of example, a housing motor 1202 and a housing drive shaft 1204 configured to move the housing 242 along a track 1206 perpendicular to the path of the radiation beam, although it should be understood that other sliding mechanisms are also contemplated.

[0057] 13 is a flowchart illustrating a method 1300 for performing a calibration scan of a slab phantom. Method 1300 may be performed by one or more processors based on instructions stored in non-transitory memory. For example, method 1300 may be performed according to instructions stored in memory and executed by one or more processors of computing device 216 of imaging system 200 described above.

[0058] In step 1302, the method 1300 includes receiving a calibration scan request. In some examples, receiving the calibration scan request may include receiving user input provided to an operator console. For example, a user may click on an item to initiate a calibration scan.

[0059] In step 1304, method 1300 includes identifying a calibration scan protocol. The calibration scan protocol may be selected by a user. For example, a user may select a desired calibration protocol from a drop-down menu of available calibration protocols. Notably, these available calibration protocols do not include diagnostic protocols; for example, these calibration protocols may vary in radiation dose, beam configuration, etc.

[0060] In step 1306, method 1300 includes determining a slab phantom corresponding to the identified calibration scan protocol. Each available calibration scan protocol corresponds to a specific slab phantom. Each slab phantom can include a subset of slabs from a slab phantom set (e.g., slab phantom set 304 described above). A slab phantom set can include a variety of different slabs having different densities and thicknesses and formed from different materials. In some examples, multiple copies of the same slab can be included in a slab phantom set. As described above, a slab phantom set can be integrated into an imaging system. For example, a slab phantom set can be incorporated into a beam filtering device that also houses filters (e.g., bowtie filters) used during diagnostic scanning protocols. In another example, a slab phantom set can be incorporated into a separate phantom housing located elsewhere in the imaging system (e.g., near the beam filtering device, in the gantry, etc.). Thus, a slab phantom set can include various combinations of slabs and various sub-combinations of slabs to form different slab phantoms.

[0061] Thus, determining a slab phantom corresponding to the identified calibration protocol may include identifying a subset of slabs of a slab phantom set integrated into the imaging system, as shown at 1308. The subset of slabs may form a slab phantom to be imaged in a calibration scan. For example, for a first calibration scan protocol, a first subset of slabs including a first slab, a second slab, and a third slab may form a first slab phantom corresponding to the first calibration scan protocol. For a second calibration scan protocol, a second subset of slabs including a first slab, a second slab, and a fourth slab may form a second slab phantom corresponding to the second calibration scan protocol. If the identified calibration scan protocol is the first calibration scan protocol, the first subset of slabs may be identified. If the identified calibration scan protocol is the second calibration scan protocol, the second subset of slabs may be identified. Because the calibration scan protocol is for calibrating the imaging system, filters configured for the diagnostic protocol (such as bowtie filters) may not be specified.

[0062] In step 1310, method 1300 includes moving a subset of slabs into the path of the X-ray beam. As described with respect to FIGS. 8-10 , each slab can be coupled to a drive shaft of a motor. The motor can actuate the drive shaft to move the corresponding slab to a position where it intersects the beam. In some embodiments, multiple slabs are coupled to the same drive shaft, in which case the motor can actuate the drive shaft to a specific position corresponding to a selected slab. Thus, the motor corresponding to each slab in the subset of slabs can be actuated to move each slab into a position where it intersects the beam. Motors corresponding to slabs not included in the subset of slabs are not actuated, and therefore, the slabs not included in the subset of slabs do not move and can remain outside the path of the beam.

[0063] For example, if a first calibration scan protocol is specified, the first, second, and third slabs are moved to intersect the beam, while the fourth slab does not move. If a second calibration scan protocol is specified, the first, second, and fourth slabs are moved to intersect the beam, while the third slab does not move. In this manner, slabs of interest in a slab phantom intended to be imaged in the calibration scan can be moved to intersect the beam.

[0064] As described herein, the intersection with the radiation beam can include a perpendicular intersection, whereby the slab moves linearly in a direction perpendicular to the path of the radiation beam. In some embodiments, the drive shaft can be rotated to rotate the slab into the path of the radiation beam.

[0065] Furthermore, since the calibration scan protocol has been identified, the filters for the diagnostic protocol (such as bowtie filters) are not moved to a position that intersects the beam. In some examples, the bowtie filters can be coupled to the same drive shaft as the slabs of the identified subset. In such examples, the drive shaft can be moved to a position corresponding to a state in which the slabs intersect the beam and the bowtie filters do not intersect the beam.

[0066] In step 1312, method 1300 includes performing a calibration scan of the slab phantom according to the identified calibration scan protocol. Once the subset of slabs is positioned in the path of the beam, a calibration scan can be performed in which x-rays are passed through the slab phantom to image the slab phantom and data can be acquired. The output image of the slab phantom can be used for calibration purposes of the imaging system (e.g., compared to known standards to assess drift or other common system errors).

[0067] Thus, a technical effect of the systems and methods provided herein is that slabs can be stored in an integrated manner within the imaging system itself. Therefore, the slabs do not need to be stored elsewhere, thereby reducing the space occupied by the slabs. Furthermore, the integrated phantom system can automatically and independently move individual slabs of a selected slab phantom into position without user assistance, thereby reducing operator time. Automatically positioning such slab phantoms can also reduce human error when positioning the phantoms and increase calibration accuracy.

[0068] Furthermore, the housing in which the set of phantom slabs is placed can be located closer to the x-ray source of the imaging system, allowing the size (e.g., width) of the individual slabs to be reduced because the x-ray beam that intersects the slabs is narrower near the x-ray source than at the isocenter, where manually placed phantoms are typically placed. Reducing the size of the slabs allows for more space-efficient storage within the system.

[0069] The present disclosure also provides support for an imaging system including: a gantry including a radiation source and a detector; a housing disposed within the gantry near the radiation source; and a slab phantom set disposed within the housing, the slab phantom set including at least one slab phantom, wherein at least one slab phantom of the slab phantom set is configured to be independently movable, and wherein one or more of the at least one slab phantoms of the slab phantom set can be selectively positioned in a path of a radiation beam between the radiation source and the detector. In a first embodiment of the system, the housing includes a collimator configured to condition and / or narrow the radiation beam, and the housing includes one or more bowtie filters and an aperture. In a second embodiment of the system that optionally includes the first embodiment, the one or more bowtie filters are disposed at a first end of the housing, the slab phantom set is disposed at a second end of the housing, and the aperture is disposed between the one or more bowtie filters and the slab phantom set. In a third embodiment of the system that optionally includes one or both of the first and second embodiments, the one or more bowtie filters are disposed at a first end of the housing, the slab phantom set is disposed to be positioned horizontally relative to the one or more bowtie filters, and the aperture is disposed at a second end of the housing to be positioned vertically relative to the one or more bowtie filters.In a fourth embodiment of the system optionally including one or more of the first to third embodiments, the at least one slab phantom includes a first slab phantom and a second slab phantom, and further includes at least one motor configured to selectively position a selected bowtie filter of the one or more bowtie filters, the first slab phantom, and one or more of the second slab phantom in a path of the radiation beam. In a fifth embodiment of the system optionally including one or more of the first to fourth embodiments, the system further includes a motor coupled to at least one bowtie filter of the one or more bowtie filters, and configured to move a selected bowtie filter of the one or more bowtie filters to selectively position the selected bowtie filter of the one or more bowtie filters in a path of the radiation beam. In a sixth embodiment of a system optionally including one or more of the first to fifth embodiments or each embodiment, the at least one slab phantom includes a first slab phantom and a second slab phantom, the imaging system further includes a first motor coupled to the first slab phantom, the first motor configured to selectively position the first slab phantom in a path of a radiation beam between the radiation source and the detector, and a first width of the first slab phantom is approximately equal to a width of the radiation beam in which the first slab phantom is selectively positioned. In a seventh embodiment of the system optionally including one or more of the first to sixth embodiments or each embodiment, the system further includes a second motor coupled to the second slab phantom, the second motor configured to move the second slab phantom to selectively position the second slab phantom in a path of a radiation beam between the radiation source and the detector, and a second width of the second slab phantom is approximately equal to the width of the radiation beam in which the second slab phantom is selectively positioned.In an eighth embodiment of the system optionally including the or each of the first to seventh embodiments, the housing is rigidly coupled to a beam filtering device, the beam filtering device being located between the housing and the radiation source. In a ninth embodiment of the system optionally including the or each of the first to eighth embodiments, the housing is configured to be selectively positioned in a path of the radiation beam and configured to move into and out of the path of the radiation beam by rotating about a hinge. In a tenth embodiment of the system optionally including the or each of the first to ninth embodiments, the housing is configured to be selectively positioned in the path of the radiation beam and configured to move into and out of the path of the radiation beam by moving linearly along a track. In an eleventh embodiment of the system optionally including the or each of one or more of the first to tenth embodiments, the at least one slab phantom comprises a first slab phantom, a second slab phantom, and a third slab phantom of the slab phantom set, the third slab phantom being independently movable with respect to the first slab phantom and the second slab phantom such that the third slab phantom is selectively positioned in a path of the radiation beam. In a twelfth embodiment of the system optionally including the or each of one or more of the first to eleventh embodiments, the at least one slab phantom comprises a first slab phantom and a second slab phantom, the first slab phantom being formed of a first material and the second slab phantom being formed of a second material different from the first material. In a thirteenth embodiment of a system optionally including one or more of the first to twelfth embodiments, the at least one slab phantom includes a first slab phantom and a second slab phantom, the first slab phantom having a first thickness and the second slab phantom having a second thickness different from the first thickness.

[0070] The present disclosure also provides support for a method for calibrating an imaging system, the method including: identifying a required calibration scan protocol; determining a slab phantom corresponding to the specified calibration scan protocol; identifying a subset of slabs of a set of slab phantoms incorporated into a housing of the imaging system, the subset of slabs forming the slab phantom corresponding to the specified calibration scan protocol; moving the subset of slabs into a path of a radiation beam; and acquiring a calibration scan of the slab phantom. In a first embodiment of the method, the subset of slabs includes a first slab phantom, and moving the first slab phantom includes actuating a first motor coupled to the first slab phantom via a first shaft, the first shaft operative to move the first slab phantom in a direction perpendicular to the path of the radiation beam. In a second embodiment of the method, which optionally includes the first embodiment, further comprises moving the housing into the path of the radiation beam by rotating the housing about a hinge and / or linearly translating the housing along a track perpendicular to the path of the radiation beam, wherein the slab phantom set is disposed in the housing. In a third embodiment of the method, which optionally includes one or both of the first and second embodiments, further comprises removing a scan window before moving the housing into the path of the radiation beam by rotating the housing about a hinge.

[0071] The present disclosure also provides support for imaging systems. The imaging system includes a gantry including a bore configured to accept a subject to be imaged, a radiation source disposed within the gantry and configured to emit a radiation beam, a detector disposed within the gantry on an opposite side of the radiation source, a housing disposed within the gantry near the radiation source, wherein a first slab phantom and a second slab phantom are disposed within the housing, a first drive system configured to move the first slab phantom into and out of the path of the radiation beam, a second drive system configured to move the second slab phantom into and out of the radiation beam, and a computing device using instructions stored in a non-transitory memory, which, when executed by a processor, cause the processor to identify a calibration scan protocol, operate one or more of the first drive system and the second drive system to move the first slab phantom and / or the second slab phantom into the path of the radiation beam based on the identified calibration scan protocol, and perform a calibration procedure. In a first embodiment of the system, the housing includes at least one bowtie filter and an aperture, the aperture being disposed between the at least one bowtie filter and the first slab phantom and the second slab phantom.

[0072] 1-12 illustrate example configurations of the relative positions of various components. When elements are shown as being in direct contact with or directly coupled to one another, they can, in at least one example, be referred to as being in direct contact with or directly coupled to one another. Similarly, elements shown as being continuous or adjacent to one another can, in at least one example, be referred to as being continuous with or adjacent to one another. As one example, components in surface contact with one another can be referred to as being in surface contact with one another. As another example, elements spaced apart from one another with only a space between them and no other components present can, in at least one example, be referred to as having such an aspect. As yet another example, elements shown above and below one another, opposite one another, or left and right of one another can be referred to as having such an aspect relative to one another. Furthermore, as shown in the figures, in at least one example, the topmost element or a point on that element can be referred to as the “top” of the element, and the bottommost element or a point on that element can be referred to as the “bottom” of the element. As used herein, top / bottom, upper / lower, and above / below are relative to the vertical axis of the figure and can be used to describe the placement of elements in the figure relative to one another. For example, if an element is shown above another element, the element is, by way of example, vertically disposed above the other element. As yet another example, the shape of an element shown in a figure can be referred to as having that shape (e.g., a circular shape, a rectilinear shape, a planar shape, a curvilinear shape, a rounded shape, a chamfered shape, an angled shape, etc.). Furthermore, elements shown intersecting one another can, at least in one example, be referred to as the elements intersecting or intersecting one another. Furthermore, in one example, if an element is shown within or outside another element, the element can be referred to as having such an aspect.

[0073] As used herein, elements or steps described in the singular and preceded by the words "a" or "an" should be understood not to exclude a plurality of such elements or steps, unless the exclusion of a plurality of such elements or steps is expressly stated. Furthermore, references to "one embodiment" of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Furthermore, unless expressly stated to the contrary, embodiments "comprising," "including," or "having" an element or elements having a particular characteristic may include additional such elements that do not have that characteristic. The terms "including" and "in which" are used as shorthand for the terms "comprising" and "wherein," respectively. Furthermore, terms such as "first," "second," and "third" are used merely as labels, and are not intended to impose numerical requirements or a specific positional order on the objects of these terms.

[0074] This specification uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the relevant art to practice the invention (e.g., to make and use the devices or systems, and to perform the incorporated methods). The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements that do not differ insubstantially from the literal language of the claims. [Explanation of symbols]

[0075] 100 CT System 106 X-ray beam 108 detector array 110 Image Processor Unit 112 Subject 114 Tables 202 detector elements 206 Center of rotation 208 Control Mechanism 210 X-ray controller 212 Gantry motor controller 214 Data Acquisition System (DAS) 216 Computing Devices 218 Storage device 220 Operator Console 226 Table Motor Controller 230 Image Composer 232 Display 240 Beam Filtering Device 242 Housing 299 Axis system 302 X-ray source 308 X-ray beam 312 Routes 314 Detector 316 Bore 320a First Bowtie Filter 320b Second Bowtie Filter 320c Third Bowtie Filter 322 Gantry Housing 324 First Slab Phantom 326 Second Slab Phantom 330 Second width 332 First Width 334 Rotating part 336 First Gap 338 Second Gap 390 First Side 392 Second Side 436 First Gap 438 Second Gap 440 The Third Gap 500 views 524 Third Slab Phantom 526 Fourth Slab Phantom 530 First Width 532 Second Width 602 First Motor 604 Second Motor 606 First drive shaft 608 Second drive shaft 618 Aperture 624 The 5th Slab Phantom 626 The 6th Slab Phantom 628 The 7th Slab Phantom 705 Third Drive Shaft 712 Third Motor 714 Fourth Motor 716 Fourth Drive Shaft 718 Fifth Motor 720 5th drive shaft 790 First Side 792 Second Side 824 Eighth Slab 826 9th Slab 908 5th Motor 910 10th Slab 912 11th Slab 914 5th drive shaft 1002 Hinge 1004 1st position 1006 Second position 1102 fasteners 1108 Scan window 1202 Housing Motor 1204 Housing drive shaft 1206 Trucks 1300 methods

Claims

1. a gantry containing a radiation source and a detector; a housing disposed within the gantry near the radiation source; a slab phantom set disposed within the housing, the slab phantom set including at least one slab phantom, the slab phantom set configured such that at least one slab phantom of the slab phantom set is independently movable, and one or more slab phantoms of the at least one slab phantom of the slab phantom set can be selectively positioned in a path of a radiation beam between the radiation source and the detector. an imaging system comprising:

2. The imaging system of claim 1 , wherein the housing includes a collimator configured to condition and / or narrow the radiation beam, and the housing includes one or more bowtie filters and an aperture.

3. 3. The imaging system of claim 2, wherein the one or more bowtie filters are disposed at a first end of the housing, the slab phantom set is disposed at a second end of the housing, and the aperture is disposed between the one or more bowtie filters and the slab phantom set.

4. 3. The imaging system of claim 2, wherein the one or more bowtie filters are disposed at a first end (390) of the housing, the slab phantom set is disposed so as to be positioned horizontally relative to the one or more bowtie filters, and the aperture is disposed at a second end (392) of the housing so as to be positioned vertically relative to the one or more bowtie filters.

5. 3. The imaging system of claim 2, wherein the at least one slab phantom comprises a first slab phantom and a second slab phantom, and further comprises at least one motor configured to selectively position one or more of a selected bowtie filter of the one or more bowtie filters, the first slab phantom, and the second slab phantom in a path of the radiation beam.

6. 3. The imaging system of claim 2, further comprising a motor coupled to at least one bowtie filter of the one or more bowtie filters, the motor configured to move a selected bowtie filter of the one or more bowtie filters to selectively position the selected bowtie filter of the one or more bowtie filters in a path of the radiation beam.

7. 2. The imaging system of claim 1, wherein the at least one slab phantom includes a first slab phantom and a second slab phantom, the imaging system further includes a first motor coupled to the first slab phantom, the first motor configured to selectively position the first slab phantom in a path of a radiation beam between the radiation source and the detector, and a first width of the first slab phantom approximately equal to a width of the radiation beam in which the first slab phantom is selectively positioned.

8. 8. The imaging system of claim 7, further comprising a second motor coupled to the second slab phantom, the second motor configured to move the second slab phantom to selectively position the second slab phantom in a path of a radiation beam between the radiation source and the detector, and a second width of the second slab phantom approximately equal to a width of the radiation beam in which the second slab phantom is selectively positioned.

9. The imaging system of claim 1 , wherein the housing is rigidly coupled to a beam filtering device, the beam filtering device being disposed between the housing and the radiation source.

10. 2. The imaging system of claim 1, wherein the housing is configured to be selectively positioned in a path of the radiation beam and configured to move into and out of the path of the radiation beam by rotating about a hinge.

11. 2. The imaging system of claim 1, wherein the housing is configured to be selectively positioned in a path of the radiation beam and configured to move into and out of the path of the radiation beam by moving linearly along a track.

12. 2. The imaging system of claim 1, wherein the at least one slab phantom comprises a first slab phantom, a second slab phantom, and a third slab phantom of the slab phantom set, the third slab phantom being independently movable relative to the first slab phantom and the second slab phantom such that the third slab phantom is selectively positioned in a path of the radiation beam.

13. 2. The imaging system of claim 1, wherein the at least one slab phantom includes a first slab phantom and a second slab phantom, the first slab phantom being formed of a first material and the second slab phantom being formed of a second material different from the first material.

14. 2. The imaging system of claim 1, wherein the at least one slab phantom comprises a first slab phantom and a second slab phantom, the first slab phantom having a first thickness and the second slab phantom having a second thickness different from the first thickness.

15. 1. A method of calibrating an imaging system, comprising: Identifying the requested calibration scan protocol; determining a slab phantom corresponding to the identified calibration scan protocol; identifying a subset of slabs of a set of slab phantoms installed in a housing of the imaging system, the subset of slabs forming a slab phantom corresponding to the identified calibration scan protocol; moving a subset of the slab into the path of the radiation beam; and acquiring a calibration scan of said slab phantom; A method comprising:

16. 16. The method of claim 15, wherein the subset of slabs includes a first slab phantom, and moving the first slab phantom includes actuating a first motor coupled to the first slab phantom via a first shaft, the first shaft operative to move the first slab phantom in a direction perpendicular to a path of the radiation beam.

17. 16. The method of claim 15, further comprising moving the housing into the path of the radiation beam by rotating the housing about a hinge and / or translating the housing linearly along a track perpendicular to the path of the radiation beam, and wherein the slab phantom set is disposed in the housing.

18. 18. The method of claim 17, further comprising removing a scan window before moving the housing into the path of the radiation beam by rotating the housing about a hinge.

19. a gantry including a bore configured to receive a subject to be imaged; a radiation source disposed within the gantry and configured to emit a radiation beam; a detector positioned within the gantry opposite the radiation source; a housing disposed within the gantry near the radiation source, the housing having a first slab phantom and a second slab phantom disposed therein; a first drive system configured to move the first slab phantom into and out of the path of the radiation beam; a second drive system configured to move the second slab phantom into and out of the radiation beam; and A computing device using instructions stored in a non-transitory memory, the instructions, when executed by a processor, causing the processor to Identifying a calibration scan protocol; activating one or more of the first drive system and the second drive system to move the first slab phantom and / or the second slab phantom, respectively, into the path of the radiation beam based on an identified calibration scan protocol; Performing a calibration procedure a computing device that executes an imaging system comprising:

20. 20. The imaging system of claim 19, wherein the housing includes at least one bowtie filter and an aperture, the aperture being disposed between the at least one bowtie filter and the first and second slab phantoms.

Images