Imaging system phantom

Abstract

To provide an embodiment of a phantom for calibrating an imaging system.SOLUTION: In an example, a phantom for an imaging system includes: a base formed of a first material; a plurality of layers arranged on the base, each layer of the plurality of layers being formed of the first material or one or more additional materials; and a plug connected to a front face of the base and the plurality of layers, the plug being configured to be connected to an accessory slot of a patient table of the imaging system.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] FIELD OF THE INVENTION Embodiments of the subject matter disclosed herein relate to phantoms, and more particularly to phantoms used to calibrate photon-counting computed tomography (CT) scanners. [Background technology]

[0002] In a computed tomography (CT) imaging system, a beam of electrons generated from a cathode is directed toward a target in an X-ray source, or X-ray tube. The electrons strike the target, producing a fan- or cone-shaped X-ray beam that is then directed toward a subject, such as a patient. After being attenuated by the subject, the X-rays strike an array of X-ray detectors, producing an image. One example of a CT system is a photon-counting CT (PCCT), in which the X-ray detectors are photon-counting detectors, and photons are counted to provide spectral information. A calibration process may be periodically performed on a PCCT system to obtain projection data for materials simulating various human tissue densities. The calibration process may involve performing the CT imaging procedure on an object called a phantom. Summary of the Invention

[0003] In one embodiment, a phantom for an imaging system includes a base constructed from a first material, a plurality of layers disposed on the base, each layer of the plurality of layers constructed from the first material or one or more additional materials, and a plug coupled to a front surface of the base and the plurality of layers, the plug configured to couple to an accessory slot of a patient table of the imaging system.

[0004] The above advantages and other advantages and features of the present specification will become readily apparent from the following detailed description, taken alone or in conjunction with the accompanying drawings. It should be understood that the foregoing summary is provided to introduce in a simplified form a selection of concepts that are further described in the detailed description. It is not intended to identify key features or essential characteristics of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Moreover, the claimed subject matter is not limited to implementations that solve shortcomings noted above or in any part of this disclosure. [Brief explanation of the drawings]

[0005] The various aspects of the present disclosure will be better understood by reading the following detailed description and by reviewing the drawings, in which: [Figure 1] 1 is a pictorial diagram of a computed tomography (CT) imaging system in accordance with one or more embodiments of the present disclosure. [Figure 2] 1 is a block schematic diagram of an exemplary CT imaging system in accordance with one or more embodiments of the present disclosure. [Figure 3] FIG. 1 is a perspective view of a phantom according to a first embodiment of the present disclosure. [Figure 4] FIG. 4 is a front view of the phantom of FIG. 3. [Figure 5] FIG. 4 is a top view of the phantom of FIG. 3. [Figure 6] FIG. 1 is a perspective view of a cover for a phantom according to an embodiment of the present disclosure. [Figure 7] FIG. 10 is a perspective view of a phantom according to a second embodiment of the present disclosure. [Figure 8] FIG. 10 is a perspective view of a phantom according to a third embodiment of the present disclosure. [Figure 9A] Examples of mechanical indicators that may be included on the phantom are shown to visually indicate secure connection of the phantom to the patient table. [Figure 9B] Examples of mechanical indicators that may be included on the phantom are shown to visually indicate secure connection of the phantom to the patient table. [Figure 10] FIG. 8 is a side view of the phantom of FIG. 7 positioned within a CT imaging system. [Figure 11] FIG. 8 is a perspective view of the phantom of FIG. 7 placed in a CT imaging system. [Figure 12] 10 is a flowchart illustrating a method for performing a calibration scan using a phantom according to an embodiment of the present disclosure. [Figure 13] 7 is a perspective view of the phantom of FIG. 3 coupled to the cover of FIG. 6. DETAILED DESCRIPTION OF THE INVENTION

[0006] Descriptions and embodiments of the subject matter disclosed herein relate to phantoms for calibration scans of imaging systems, such as photon-counting computed tomography (PCCT) systems. Imaging systems, such as PCCT systems, may require periodic calibration scans, such as daily or weekly calibration scans, to offset hardware-induced gain drift, such as changes in the focal spot position of an X-ray tube or radiation degradation of detectors. Furthermore, PCCT systems can obtain spectral information that enables the generation of basis material decomposition (BMD) images. Calibrating a PCCT system may require obtaining calibration projection data that mimics the materials and material thicknesses of the human body. Therefore, phantoms for calibrating PCCT systems can include multiple different materials, such as polyvinyl chloride (PVC) and polyethylene (PE). However, such phantoms are relatively heavy, making it difficult for all users to move the phantom on and off the patient table each time a calibration scan is performed. Many phantoms are not ergonomically sound and can cause discomfort to the user when lifting or carrying the phantom.

[0007] Thus, disclosed herein are embodiments of a lightweight, ergonomic phantom for calibrating imaging systems, such as PCCT systems. The phantoms disclosed herein may be composed of multiple layers of material stacked on top of each other to form a single-piece phantom. Different layers of the phantom can have different lengths, such that different vertical slices in different portions of the phantom are composed of different layers of material. A vertical slice containing one or more layers may be referred to as a stack. The entire length of the stack contains layers of the same material. Each stack has a width comparable to the width of an x-ray beam. In some embodiments, the phantom can include a foam cover with an integrated handle to facilitate handling of the phantom. In other embodiments, the phantom can include handles integrated into the base and / or top of the phantom. The foam cover can also cover sharp edges of the phantom to facilitate handling.

[0008] The phantoms disclosed herein may include a plug that allows the phantom to be coupled to an accessory slot in the patient table of an imaging system. By coupling the phantom to the accessory slot in the patient table, the phantom may be manipulated by moving the patient table, potentially enabling accurate and consistent placement of the phantom within the imaging system. Furthermore, the phantoms disclosed herein may be configured to be positioned as close as possible to the x-ray tube during calibration scans due to the location of the plug on the phantom (which allows the phantom to be positioned relatively close to the bottom of the imaging system bore and therefore the x-ray tube). By positioning the phantom closer to the x-ray tube, the phantom may include a thinner layer of material than would be possible if the phantom were positioned further away from the x-ray tube, thereby reducing the phantom's weight. Furthermore, the phantoms disclosed herein may have a trapezoidal shape that matches the shape of the x-ray beam, further reducing the phantom's weight by eliminating unnecessary material.

[0009] A calibration scan can be performed on the phantom, which involves scanning a stack, adjusting the table position to move the next stack of phantoms into the x-ray beam, and then scanning the next stack of phantoms. Accurate positioning of the phantom is particularly useful in systems such as PCCT systems that require frequent calibration because calibration scans can easily be duplicated. The phantom can also include a visual indicator to inform the user that the phantom is properly installed in the table's accessory slot.

[0010] 1 illustrates an exemplary PCCT system 100 (also referred to as a photon-counting X-ray imaging system) configured to perform CT imaging using photon-counting detectors. In particular, the PCCT system 100 is configured to image a subject 112, such as a patient, an inanimate object, one or more manufactured parts, and / or foreign objects present in the body, such as dental implants, stents, and / or contrast media. The PCCT system 100 includes a gantry 102, which may further include at least one X-ray source 104 configured to project a beam of X-ray radiation 106 (see FIG. 2 ) for use in imaging the subject 112 residing on a table 114. Specifically, the X-ray source 104 is configured to project the beam of X-ray radiation 106 toward a detector array 108 disposed on the opposite side of the gantry 102. 1 depicts a single X-ray source 104, in certain embodiments, multiple X-ray sources and detectors can be employed to project multiple X-ray radiation beams for acquiring projection data at the same or different energy levels corresponding to the patient. In some embodiments, the X-ray source 104 can enable dual-energy gemstone spectral imaging (GSI) through rapid peak kilovoltage (kVp) switching. In the embodiments described herein, the X-ray detector employed is a photon-counting detector capable of distinguishing between X-ray photons of different energies.

[0011] In certain embodiments, the PCCT system 100 further includes an image processor unit 110 configured to reconstruct images of a target volume of the subject 112 using an iterative or analytical image reconstruction approach. For example, the image processor unit 110 may reconstruct images of a target volume of the patient using an analytic image reconstruction approach, such as filtered back projection (FBP). As another example, the image processor unit 110 may reconstruct images of the target volume of the subject 112 using an iterative image reconstruction approach, such as advanced statistical iterative reconstruction (ASIR), conjugate gradient (CG), maximum likelihood expectation maximization (MLEM), model-based iterative reconstruction (MBIR), etc. In some examples, the image processor 110 may use an analytic image reconstruction approach, such as FBP, in addition to an iterative image reconstruction approach.

[0012] In some CT imaging system configurations, an x-ray source projects a cone-shaped beam of x-ray radiation, defined with respect to an XYZ Cartesian coordinate system and commonly referred to as an "imaging volume." The x-ray radiation beam passes through an imaging object, such as a patient or object. After being attenuated by the object, the x-ray radiation beam impinges on an array of detector elements. The intensity of the attenuated x-ray radiation beam received at the detector array depends on the attenuation of the x-ray radiation beam by the object. Each detector element in the array produces a separate electrical signal that is a measurement of the attenuation of the x-ray beam at the detector location. The attenuation measurements from all detector elements are acquired separately to create a transmission profile.

[0013] In some CT systems, the x-ray source and detector array are rotated with a gantry within the imaging volume and around the object being imaged so that the angle at which the x-ray beam intersects the object is constantly changing. A set of x-ray radiation attenuation measurements, e.g., projection data, from the detector array at a given gantry angle is called a "view." A "scan" of the object involves a series of views made at different gantry angles (view angles) during one revolution of the x-ray source and detector.

[0014] FIG. 2 illustrates an exemplary imaging system 200 similar to the PCCT system 100 of FIG. 1. In accordance with aspects of the present disclosure, the imaging system 200 is configured to image a subject 204 (e.g., subject 112 of FIG. 1). During a particular scan, the subject may be a phantom. The phantom may be an object configured to be scanned by the PCCT system as part of a calibration process for the PCCT system. In one embodiment, the imaging system 200 includes a detector array 108 (see FIG. 1). The detector array 108 further includes a plurality of detector elements 202 that together sense an x-ray radiation beam 106 (see FIG. 2) passing through the subject 204 (e.g., a patient) to acquire corresponding projection data. In some embodiments, the detector array 108 is a multi-slice configuration including multiple rows of cells or detector elements 202, where one or more additional rows of detector elements 202 are arranged in a parallel configuration to acquire projection data. The detector elements 202 may also be referred to as pixels or detector pixels.

[0015] In certain embodiments, imaging system 200 is configured to traverse different angular positions around object 204 to acquire desired projection data. Thus, gantry 102 and the components mounted thereon 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 204 changes as a function of time, the mounted components may be configured to move along a general curve rather than along a segment of a circle.

[0016] As the x-ray source 104 and detector array 108 rotate, the detector array 108 collects data of the attenuated x-ray beam. The data collected by the detector array 108 undergoes pre-processing and calibration to condition the data to represent line integrals of the attenuation coefficients of the scanned object 204. The processed data are commonly referred to as projections. In some embodiments, individual detectors or detector elements 202 of the detector array 108 may include photon-counting detectors that register individual photon interactions into one or more energy bins.

[0017] The acquired set of projection data can be used for basis material decomposition (BMD). During BMD, the measured projections are converted into a set of material density projections. The material density projections may be reconstructed to form a set of material density maps or images of each basis material, such as bone, soft tissue, and / or contrast agent maps. The density maps or images may then be correlated to form a 3D volumetric image of the basis materials, e.g., bone, soft tissue, and / or contrast agent, within the imaged volume.

[0018] Once reconstructed, the basis material images generated by the imaging system 200 reveal internal features of the subject 204, which are represented by the densities of the two basis materials. The density images may be displayed to illustrate these features. In a traditional approach to diagnosing medical conditions, such as medical conditions, or more generally, medical events, a radiologist or physician considers a hard copy or display of the density images to identify characteristic features of interest. Such features include lesions, the size and shape of particular anatomical structures or organs, and other features identifiable from the images based on the skill and knowledge of the individual medical practitioner.

[0019] 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 source 104. In some embodiments, control mechanism 208 further includes an x-ray controller 210 configured to provide power and timing signals to x-ray source 104. Additionally, control mechanism 208 includes a gantry motor controller 212 configured to control the rotational speed and / or position of gantry 102 based on imaging requirements.

[0020] In certain embodiments, the control mechanism 208 further includes a data acquisition system (DAS) 214 configured to sample analog data received from the detector elements 202 and convert the analog data to a digital signal for subsequent processing. The DAS 214 may be further configured to selectively aggregate data from a subset of the detector elements 202 into a so-called macro-detector. The data sampled and digitized by the DAS 214 is transmitted via slip ring 213 to a computer or computing device 216. In one example, the computing device 216 stores the data in a storage device or mass storage device 218. The storage device 218 may be, for example, any type of non-transitory memory and may include 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.

[0021] 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 operations, such as data acquisition and / or processing. In certain embodiments, the computing device 216 controls system operations based on operator input. The computing device 216 receives operator input, including commands and / or scan parameters, for example, via an operator console 220 operably coupled to the computing device 216. The operator console 220 may include a keyboard (not shown) or a touch screen to enable an operator to specify commands and / or scan parameters.

[0022] 2, multiple operator consoles may be coupled to imaging system 200, for example, to input or output system parameters, request examinations, plot data, and / or view images. Additionally, in certain embodiments, imaging system 200 may be coupled to multiple displays, printers, workstations, and / or similar devices located either locally or remotely, for example, within an institution or hospital, or at entirely different locations, via one or more configurable wired and / or wireless networks, such as the Internet and / or a virtual private network, a wireless telephone network, a wireless local area network, a wired local area network, a wireless wide area network, a wired wide area network, or the like.

[0023] In one embodiment, for example, imaging 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 a remote system, such as a radiology department information system, a hospital information system, and / or an internal or external network (not shown), allowing operators at different locations to provide commands and parameters and / or access image data.

[0024] The computing device 216 uses operator-supplied and / or system-defined commands and parameters to operate a table motor controller 226, which may control the table 114, which may be a motorized table. In particular, the table motor controller 226 may move the table 114 to properly position the subject 204 within the gantry 102 to acquire projection data corresponding to a target volume of the subject 204.

[0025] As mentioned 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 FIG. 2 illustrates image reconstructor 230 as a separate entity, in certain embodiments, image reconstructor 230 may form part of computing device 216. Alternatively, image reconstructor 230 may not be present in imaging system 200; instead, computing device 216 may perform one or more functions of image reconstructor 230. Furthermore, image reconstructor 230 may be located locally or remotely and may be operably connected to imaging system 200 using a wired or wireless network. In particular, in one exemplary embodiment, computing resources in a “cloud” network cluster may be used for image reconstructor 230.

[0026] In one embodiment, image reconstructor 230 stores the reconstructed image in storage device 218. Alternatively, image reconstructor 230 may transmit the reconstructed image to computing device 216 to generate useful patient information for diagnosis and evaluation. In certain embodiments, computing device 216 may transmit the reconstructed image and / or patient information to a display or display device 232 communicatively coupled to computing device 216 and / or image reconstructor 230. In some embodiments, the reconstructed image may be transmitted from computing device 216 or image reconstructor 230 to storage device 218 for short-term or long-term storage.

[0027] Information may be transferred between components residing within the gantry 102 and external devices (such as the computing device 216 and / or the image reconstructor 230) via slip rings 213, which facilitate electronic communication across the rotating gantry. In some embodiments, the gantry and internal components (e.g., the control mechanism 208, the x-ray source 104, the detector array 108) may be collectively defined as a PCCT scanner, and as such, the computing device 216 and the image reconstructor 230 may reside outside the scanner.

[0028] FIG. 3 is a perspective view of an example phantom 300, FIG. 4 is a front view of an example phantom 300, and FIG. 5 is a top view of an example phantom 300; such FIGS. 3, 4, and 5 may be collectively described. Each of FIGS. 3-5 includes a Cartesian coordinate system 301. In one example, the z-axis of coordinate system 301 may be a vertical axis (e.g., parallel to the gravity axis), the y-axis of coordinate system 301 may be a vertical axis (e.g., horizontal axis), and / or the x-axis of coordinate system 301 may be a horizontal axis. However, the axes may have other directions in other examples. When referring to directions, positive may point in the direction of the x-axis, y-axis, or z-axis arrow, and negative may point in the opposite direction of the x-axis, y-axis, or z-axis arrow. Filled circles may represent arrows and axes pointing toward or positively relative to the field of view. Unfilled circles may represent arrows and axes pointing away from the field of view, i.e., negative relative to the field of view. Additionally, although Figures 3-8 and 13 are drawn to scale, other relative dimensions may be used as desired.

[0029] Phantom 300 may be comprised of a body 303, a plug section 315, and a coupling portion 310 that couples plug section 315 to body 303. Body 303 may have a trapezoidal prism shape. However, in other examples, phantom 300 may include a body of a different shape, such as a rectangular parallelepiped or a cylinder. Body 303 may include a base 302 made of a first material, such as PVC, on which multiple layers of different materials (e.g., PVC and PE) are disposed. The trapezoidal shape of body 303 may allow each layer to match the width of the x-ray beam at the height of each layer when phantom 300 is placed in the gantry of an imaging system and an x-ray tube is positioned below the phantom, as shown in FIGS. 10 and 11 and described in more detail below. Because the x-ray beam expands as it extends from the x-ray source, the top layer of the material of the body 303 may be struck by a wider x-ray beam than a lower layer of the material of the body 303 (e.g., base 302). In the example shown in FIG. 3, the multiple layers include a first layer 304, a second layer 306, and a third layer 308 disposed on the base 302. The multiple layers may be composed of a first material and a second material (e.g., PE). The layers may be made of PVC, PE, or other materials. For example, the first layer 304 may be composed of PE, the second layer 306 may be composed of PVC, and the third layer may be composed of PE. However, the layers may be made of any combination of materials in any order. In some examples, the layers may all be made of the same material.

[0030] The body 303 of the phantom 300 may include a top portion 398 (e.g., upper surface) and a base bottom portion 326 (e.g., bottom surface). The top portion 398 may have a stepped profile composed of multiple layers of material (which may, in some examples, include at least two different materials). A longitudinal axis 311 extends along the y-axis of the Cartesian coordinate system 301, and the phantom 300 may be symmetrical about the longitudinal axis 311. A vertical axis 313 extends along the z-axis of the Cartesian coordinate system 301, and the phantom 300 may be symmetrical about the longitudinal axis 313. The body 303 of the phantom 300 may have a front surface 309, a back surface (not shown), a first side 305, and a second side 307. The first side 305 and the second side 307 may be composed of sides of the base 302 and sides of multiple layers of material stacked on the base 302. The base bottom 326 may be narrower than the top 398. The first side 305 and the second side 307 may extend away from the vertical axis 313 at an angle greater than 90 degrees (e.g., a 120 degree angle) from the base bottom 326 to the top 398. In one example, the phantom 300 may measure between 5 mm and 400 mm along the z-axis, between 20 mm and 450 mm along the y-axis, and between 250 mm and 650 mm along the x-axis of the Cartesian coordinate system 301.

[0031] The base 302 may be a trapezoidal prism having a trapezoidal front base surface 322 and a trapezoidal back base surface 324. The base 302 may have a base bottom 326 and a base top 328, each having a rectangular shape. The base bottom 326 may have a narrower width along the x-axis than the base top 328, but the base bottom 326 and the base top 328 may have the same length along the y-axis. For example, the base bottom 326 and the base top 328 may have a first length 325. Similarly, the base bottom 326 may have a first width 327, and the base top 328 may have a second width 329. The first width 327 may be greater than the second width 329. The base 302 may have a first base side 330 and a second base side 332. In the illustrated example, first base side 330 and second base side 332 may each be a rectangular surface extending at a 120-degree angle 334 from base bottom 326 to base top 328. Similarly, first base side 330 and second base side 332 may connect front base surface 322 to back base surface 324. In examples where body 303 is trapezoidal in shape, the trapezoidal shape of phantom 300 may reduce weight (e.g., when compared to a square phantom large enough to contain the beam). However, in other embodiments, the phantom may be another shape, such as square, rectangular, circular, etc.

[0032] The first layer 304 is coupled to a base top 328. The first layer 304 may be a trapezoidal prism. The first layer may have a first layer bottom 336 and a first layer top 338. The first layer bottom 336 may be the same shape and size as the base top 328, and the first layer top 338 may be rectangular, having the same length as the first layer bottom 336 but a wider width than the first layer bottom 336. For example, the first layer bottom 336 and the first layer top 338 may each have a first length 325. The first layer bottom 336 may have a second width 329. Similarly, the first layer top 338 may have a third width 331. The third width 331 may be greater than the second width 329. The first layer bottom 336 is in face-sharing contact with the base top 328 along the entire extent of each of the first layer bottom 336 and the base top 328. The first layer 304 may have a first layer front 342 and a first layer back (not shown) connected by a first layer first side 344 and a first layer second side 346. The first layer first side 344 and the first layer second side 346 may join the first layer front 342 to the first layer back and join the first layer top 338 to the first layer bottom 336. The first layer first side 344 and the first layer second side 346 may be coplanar and disposed at an angle 340 from the first layer bottom 336.

[0033] The second layer 306 may be disposed on the first layer 304. The second layer 306 may, at least in some examples, be made of a different material than the first layer 304. The second layer 306 is a trapezoidal prism that may have a shorter length than the first layer 304. The second layer 306 may have a second layer bottom 348 and a second layer top 350 that are rectangular and of the same length. The second layer bottom 348 may have the same width as the first layer top 338. The second layer bottom 348 is in surface-shaping contact with the first layer top 338 along the entire extent of each of the second layer bottom 348 and the first layer top 338. The second layer top 350 may be wider than the second layer bottom 348. For example, the second layer bottom 348 and the second layer top 350 may each have a second length 333. Second layer bottom 348 may have a third width 331. Similarly, second layer top 350 may have a fourth width 335. Fourth width 335 may be greater than third width 331. Second layer 306 may have a second layer front 356 and a second layer back (not shown), which may be two identical trapezoidal surfaces. The second layer may have a second layer first side 352 and a second layer second side 354. Second layer first side 352 and second layer second side 354 may connect second layer bottom 348 to second layer top 350 and connect second layer front 356 to second layer back. Second layer first side 352 and second layer second side 354 may extend from second layer bottom 348 at angle 358, which is the same as angle 340 and angle 334. In the exemplary phantom 300 shown in FIG. 3 , base 302 has a first height along the z-axis, and first layer 304 has a second height along the z-axis that is less than the first height. Second layer 306 has a third height that is greater than the second height of first layer 304 but less than the first height of base 302. However, in other embodiments, second layer 306 may have a height greater than or equal to first layer 304.

[0034] The third layer 308 may be disposed above the second layer 306 and, in at least some examples, may be made of a different material than the first layer 304 and / or the second layer 306. The third layer 308 may have a stepped side profile composed of a first L-shaped side 360 ​​and a second L-shaped side 362. The third layer 308 includes a first step 318 and a second step 320. In the exemplary phantom 300, the third layer 308 has a shorter length than the second layer 306. The third layer 308 may include a third layer front portion 370 and a third layer rear portion (not shown), which may be trapezoidal in shape. The third layer 308 may include a third layer bottom portion 364, a first step apex portion 366, and a second step apex portion 368. The third layer bottom 364 may have the same width as the second layer top 350 and may have a shorter length 337 than the second layer top 350. The first step apex 366 and the second step apex 368 may each be rectangular and half the length of the third layer bottom 364. For example, the first step apex 366 may have a length 341, and the second step apex 368 may have a length 339. The second step apex 368 may be wider than the first step apex 366. For example, the third layer bottom 364 may have a fourth width 335, the first step apex 366 may have a fifth width 343, and the second step apex 368 may have a sixth width 345. The sixth width 345 may be greater than the fifth width 343, and the fifth width 343 may be greater than the fourth width 335. The third layer 308 may have a second height and a fourth height (from the third layer bottom 364 to the second step apex 368) that is greater than the third height and less than the first height, although in other embodiments the fourth height may be equal to the second height or the third height, less than the third height, or another suitable height. The first L-shaped side 360 ​​and the second L-shaped side 362 may connect the third layer bottom 364 to the first step apex 366, the second step apex 368, the third layer front 370, and the third layer rear. The first L-shaped side 360 ​​and the second L-shaped side 362 may extend at an angle 372 from the third layer bottom 364.

[0035] In some examples, the base 302, the first layer 304, the second layer 306, and the third layer 308 may be fused at the interfaces between the layers. For example, the phantom 300 may be injection molded. In other examples, the base 302, the first layer 304, the second layer 306, and the third layer 308 may be formed separately and then bonded together using adhesive, heat, and / or another bonding mechanism. In one example, the layers may be bonded together by fasteners such as bolts located outside the path of the x-ray beam. In other examples, the layers may be bonded together by features such as a press fit or interface fit, a tongue and groove fit, or an adhesive applied between the layers.

[0036] According to the above description, the top 398 of the phantom 300 may be stepped in profile based on the diminishing lengths of the first layer 304, the second layer 306, and the third layer 308. Each step may constitute a stack, which is a vertical section of the phantom 300 containing the material of that step. The phantom 300 may include a first vertical stack including the base 302 and the first layer 304, a second vertical stack including the base 302, the first layer 304, and the second layer 306, a third vertical stack including a first step 318 in the base 302, the first layer 304, the second layer 306, and the third layer 308, and a fourth vertical stack including a second step 320 in the base 302, the first layer 304, the second layer 306, and the third layer 308. However, in instances where one or more of the first layer 304, second layer 306, and third layer 308 share the same length, the configuration of the vertical stack may be different. For example, if the second layer 306 has the same length as the first layer 304, the first stack may include the base 302, the first layer 304, and the second layer 306.

[0037] The coupling section 310 of the phantom 300 may include a first arm 374, a second arm 376, and a fastening plate 312. Each of the first arm 374 and the second arm 376 may be comprised of an extension of the base 302, the first layer 304, the second layer 306, and the third layer 308 (e.g., extending from the front surface of each layer and extending from the body 303 of the phantom 300). The first arm 374 and the second arm 376 may be identical, may extend a specific distance from the front surface of each layer of the body, and each arm may have a specific width. The first arm 374 and the second arm 376 may have a flat rectangular top that is integrated into the second step 320. The first arm 374 and the second arm 376 may extend outward from the entire vertical extent of the first layer 304, the second layer 306, and the third layer 308 and may extend outward from a portion of the base 302. The first arm 374 may intersect the front surface of each layer of the body at a first rounded corner 378 and a second rounded corner 382. The second arm 376 may intersect the front surface of each layer of the body at a third rounded corner 380 and a fourth rounded corner 384. The corners may be rounded to allow an operator to interact with the arms without being exposed to sharp corners. The first arm 374 and the second arm 376 may be separated by an opening. The first arm 374 may have a first arm front surface 386, which may be a rectangular surface extending the height of the first arm 374. The second arm 376 can have a second arm front 388 that is a rectangular face that extends the height of the second arm 376. The first arm front 386 and the second arm front 388 can lie in the same zx plane.

[0038] The fastening plate 312 may be coupled to the first arm front portion 386 and the second arm front portion 388. The fastening plate 312 may have a rectangular shape with rounded corners. The fastening plate 312 may have a width equal to the span from the first arm 374 to the second arm 376 and a height equal to the height of the first arm 374 and the second arm 376. The plug section 315 may include a plug base 316 fixed to the fastening plate 312 and a plug 314 extending outward (e.g., in the -y direction) from the plug base 316. The plug base 316 may be a trapezoidal prism having a vertical side 390 that contacts the fastening plate 312. The vertical side 390 may be the same width as the fastening plate 312 or may be attached to the center of the fastening plate 312 depending on the height of the fastening plate 312. The vertical side 390 may have a specific height along the z-axis. The plug base 316 may have a plug bottom 394 and a plug top 392. The plug bottom 394 and the plug top 392 may be long along the x-axis, similar to the fastening plate 312, but the plug bottom 394 may be wider along the y-axis than the plug top 392. The plug base 316 may further include a sloped side 396 that may couple the plug bottom 394 to the plug top 392. The plug 314 may extend from the sloped side 396. The plug 314 may be arc-shaped and may have a specific length, width, and radius of curvature for coupling to an accessory slot of the patient table (e.g., the length, width, thickness, and radius of curvature may match / complement an accessory slot of the patient table such that the plug 314 can be slidably received by the accessory slot and secured via a locking mechanism of the accessory slot).

[0039] FIG. 6 is a perspective view of a cover 600 for a phantom, such as phantom 300. Cover 600 may be made of a foam material to protect phantom 300 from deterioration and may cover any edges of phantom 300 to facilitate handling / moving phantom 300. To couple phantom 300 to cover 600, phantom 300 can be inserted into cover 600. Cover 600 may include a bottom 606, a first side 610, a second side 612, a top 609 consisting of a flat top 608 and a sloped top 614, and a front cover surface 624. Each of bottom 606, first side 610, second side 612, and top 609 includes an outer surface facing the environment and an inner surface facing the hollow interior of cover 600. The bottom 606 may be a rectangular piece of foam that is flat in the x-y plane. The bottom 606 may be sized to accommodate the base bottom 326 (e.g., the inner surface of the bottom 606 may have a length and width that match the length and width of the base bottom 326, with a small tolerance to allow for movement of the phantom in and out of the cover). The first side 610 and the second side 612 may extend away from the bottom 606 at a 120-degree angle. The first side 610 and the second side 612 may be identical irregular pentagons that may be constructed from foam. Although more features of the second side 612 are visible in FIG. 6 than the first side 610, both sides are identical, and therefore, descriptions of the features of the second side 612 may also apply to similar features of the first side 610.

[0040] The second side 612 may be defined by a leading edge 626, a first top edge 628, a second top edge 630, a trailing edge 632, and a bottom edge 634. The first top edge 628 may be a straight edge where the second side 612 is joined to the flat top portion 608. The second top edge 630 is a straight edge where the second side 612 is joined to the sloped top portion 614. The second top edge 630 may be angled in the -z direction. The trailing edge 632 may be a straight edge where the second side 612 is joined to the cover back surface 616.

[0041] The leading edge 626 may be a straight edge that forms a portion of the cover front surface 624. The leading edge 626 may further include a handle edge 636 that extends from the leading edge 626 in the x-direction to form a second handle 602. The second handle 602 may extend from a second side 612 of the cover 600. The second handle 602 may have a width along the x-axis suitable for a person to grasp the second handle 602 and may include a rounded edge 638 at the bottom. The rounded edge 638 may extend from the surface of the second side 612 to form a gap configured to accommodate a user's fingers when moving the cover 600. The first side 610 may have a first handle 604. When the phantom 300 is inserted into the cover 600, the first handle 604 and the second handle 602 may be used together by one or more people to lift and move the phantom 300 and the cover 600.

[0042] The top 609 of the cover 600 may include a flat top 608 that is a rectangular piece of foam extending in the xy plane between the tops of the first side 610 and the second side 612. The flat top 608 may be joined to a sloped top 614. The sloped top 614 may be a rectangular piece of foam that is also joined to the first side 610 and the second side 612. The cover 600 may have a back cover 616 that may be open. The back cover 616 may be an opening defined by the sloped top 614, the first side 610, the second side 612, the bottom 606, and the sloped top 614. In some examples, the cover back 616 may be closed and may include a flat, rectangular piece of foam joined to a first side 610, a second side 612, a bottom 606, and a sloped top 614. It should be understood that each piece of foam described herein may be a separate piece joined together, or the cover 600 may be molded or otherwise formed such that the cover 600 is comprised of one single piece of material. In such cases, the different pieces described herein may not be separate pieces.

[0043] The cover front surface 624 may include a planar front surface extending between an outer perimeter (defined by the outer edges of the bottom 606, first side 610, second side 612, and flat top 608) and an inner perimeter 625 defined by the inner edges of the bottom 606, first side 610, second side 612, and flat top 608. The space within the inner perimeter 625 may define a front opening of the cover 600. Thus, the cover front surface 624 may be open to the hollow interior of the cover 600. The inner surface of the top 609 (e.g., the inner surfaces of the flat top portion 608 and the sloped top 614) may form an interior roof 640 of the cover 600. The roof 640 may include a plurality of rectangular protrusions extending from the roof 640 to match the stepped top of the phantom 300, which is composed of the first layer 304, the second layer 306, the first step 318, and the second step 320. The plurality of protrusions may include a first rectangular protrusion 618, a second rectangular protrusion 620, and a third rectangular protrusion 622. The first rectangular protrusion 618 may be shaped to fit into the space between the second step 320 and the first step 318 when the phantom 300 is inserted into the cover 600. The first rectangular protrusion 618 can make surface contact with the first step 318 when the phantom 300 is housed in the cover 600. The second rectangular protrusion 620 may be shaped to fit into the space between the first step 318 and the second layer 306 when the phantom 300 is inserted into the cover 600. The second rectangular protrusion 620 may come into surface contact with the second layer 306 when the phantom 300 is housed in the cover 600. The third rectangular protrusion 622 may have a shape that fits into the space between the second layer 306 and the first layer 304 when the phantom 300 is inserted into the cover 600. The third rectangular protrusion 622 may come into surface contact with the first layer 304 when the phantom 300 is housed in the cover 600.

[0044] Thus, the interior of the cover 600 can have a shape that matches (e.g., is complementary to) the outer shape of the body 303 of the phantom 300 and is configured to accommodate the body 303 of the phantom 300 in a surface-to-surface contact manner. In examples where one or more of the phantom's layers, such as the first layer 304, the second layer 306, or the third layer 308, are the same length, the top of the phantom may have a different profile than that of the phantom 300. In that example, the shape of the interior of the cover may be adjusted to achieve surface-to-surface contact with the adjusted shape of the top of the phantom. Similarly, if the phantom is rectangular rather than trapezoidal in shape, the interior and exterior shapes of the cover 600 may be tailored to the shape of the phantom, with the first and second sides of the cover 600 being straight rather than angled. The cover 600 may be constructed of a lightweight yet sturdy material, such as foam, and may have sufficient flexibility or dimensional tolerances to allow for insertion and removal of the phantom 300.

[0045] FIG. 13 is a perspective view 1300 of a phantom 300 housed within a cover 600. As shown in FIG. 13 , when housed within the cover 600, the front surfaces of the various layers of the body 303 of the phantom 300 (e.g., the base front surface 322, the first layer front portion 342, the second layer front portion 356, and the third layer front portion 370) may lie flush with the planar front surface of the cover front surface 624. The first arm 374 and the second arm 376 and the plug base 316 and the plug 314 may extend from the cover 600. In other examples, the front surface may be slightly recessed into the hollow interior of the cover 600. In examples where the front surface is slightly recessed into the hollow interior of the cover 600, portions of the first arm 374 and the second arm 376 may also be recessed into the hollow interior of the cover 600. However, portions of the plug base 316 and plug 314, as well as the first arm 374 and second arm 376, may extend from the cover 600. This allows the cover 600 to protect the user from touching the edges of the phantom 300 and facilitate movement of the phantom 300 via handles on either side of the cover 600. In some embodiments, the cover 600 may be constructed of a radiolucent material so that the cover 600 can remain on the phantom 300 during calibration scans. In other examples, the cover 600 may be removable during scanning (e.g., the cover 600 may be removed from the phantom 300 once the plug 314 is secured to the patient table). The phantom 300 includes a trapezoidal prism-shaped body. However, in other embodiments, the phantom may have alternative shapes, such as a cylinder, a cube, a rectangular prism, or other shapes. In an example where the phantom body is a square pillar (rectangular prism), the phantom may have flat rectangular front and back surfaces of the same size and shape, two identical flat rectangular sides, and a flat rectangular bottom. The top of the phantom may be rectangular with the same area as the bottom, as described above, with a stepped profile of layers stacked on top of the bottom. To maintain the rectangular shape of the phantom body, the layers may all have the same width and straight sides at right angles to their respective bases.In an example where the phantom body is a rectangular parallelepiped, the cover may be shaped to fit the phantom. The cover may be similar in structure to cover 600, but adapted to fit a rectangular phantom. The cover may have two identical rectangular sides, including handles. The rectangular sides may be attached perpendicular to the rectangular base. The cover may include a top attached perpendicular to the sides of the cover. The top of the cover may include a flat portion and a sloped portion, similar to top 609 of cover 600. The top of the cover may have an internal step to match the contour of the top of the phantom. The front of the cover may be a rectangular opening into which the rectangular phantom is inserted. The back of the phantom may be a rectangular opening.

[0046] FIG. 7 is a perspective view of a phantom 700 according to a second embodiment of the present disclosure. Phantom 700 is similar to phantom 300 described with reference to FIGS. 3-5 in that it includes a body 703 including a base 702 on which three layers of PVC, PE, and / or another material are laminated. Phantom 700 may include a first layer 704, a second layer 706, and a third layer 708 composed of a first step 709 and a second step 711. Phantom 700 may further include a plug portion 705 consisting of a plug 710 and a plug base 712. Plug 710 and plug base 712 may be similar to plug 314 and plug base 316, respectively. Phantom 700 may be identical to phantom 300, except for the differences described below.

[0047] Rather than being a cover like cover 600, phantom 700 includes a handle integrated into base 702. FIG. 7 shows handle 715 coupled to base 702 by first fastener protrusion 714 and second fastener protrusion 716. Handle 715 may be a cylinder made of the same material as base 702. First fastener protrusion 714 may be a rectangular extension of base 702 with a rounded front surface. First fastener protrusion 714 may be coupled to handle 715. Second fastener protrusion 716 may have a greater height than first fastener protrusion 714. For example, first fastener protrusion 714 may have a first height 730, and second fastener protrusion 716 may have a second height 732. Second height 732 may be greater than first height 730. The second fastener protrusion 716 may be a rounded protrusion, including a rounded protrusion where the base 702, first layer 704, second layer 706, and third layer 708 are stacked on top of one another. A handle 715 may be coupled to the portion of the second fastener protrusion 716 formed from the base 702. The handle 715 is coupled to the first fastener protrusion 714 and the second fastener protrusion 716 at the same height. The phantom 700 may include identical handles and fastener protrusions on opposite sides of the phantom 700. For example, a fourth fastener protrusion 717 is shown extending from the opposite side of the phantom 700 from the handle 715. Although not shown in FIG. 7 , it should be understood that a third fastener protrusion similar to the first fastener protrusion 714 and a second handle similar to the handle 715 are also included on the opposite side of the phantom 700.

[0048] Furthermore, phantom 700 does not include a first arm or a second arm like first arm 374 and second arm 376 of phantom 300, and phantom 700 does not include a fastening plate like fastening plate 312 of phantom 300. Instead, phantom 700 includes a rectangular coupling base 718 that is coupled to plug base 712. Rectangular coupling base 718 may be made of the same material as plug base 712 and is a rectangular prism spanning the width of phantom 700 that includes second fastening protrusions 716 and fourth fastening protrusions 717. Rectangular coupling base 718 can be fastened to second fastening protrusions 716 by first fasteners 720 and second fasteners 722. First fasteners 720 and second fasteners 722 may be screws, bolts, or other fasteners. The rectangular coupling base 718 presents an alternative attachment site for the plug base compared to the first arm 374 and second arm 376 included in the phantom 300. In some embodiments, the rectangular coupling base 718 may be included in the phantom 300 rather than the coupling arms and plates described above.

[0049] FIG. 8 is a perspective view of a phantom 800 according to a third embodiment of the present disclosure. The phantom 800 is identical to the phantom 300 described with reference to FIGS. 3-5, except that the phantom 800 includes a first handle 802 and a second handle 804. The second handle 804 may be comprised of a first cylinder 806, a second cylinder 808, and a third cylinder 810. The first cylinder 806 extends in the positive z-direction from the first arm 374 of the phantom 800, and the second cylinder 808 extends in the positive z-direction from the second arm 376 of the phantom 800. The first cylinder 806 and the second cylinder 808 may have the same height and diameter and may be joined at a right angle to the third cylinder 810 by rounded corners. For example, the first cylinder 806 may be connected to the third cylinder 810 via a first rounded corner 816. The second cylinder 808 may be connected to the third cylinder 810 via a second rounded corner 818. The third cylinder 810 may be the same diameter as the first cylinder 806 and the second cylinder 808 and may have a length that spans the distance between the first cylinder 806 and the second cylinder 808. The first handle 802 may be substantially similar to the second handle 804 (e.g., the first handle 802 may include two cylinders extending outward in the −y direction and a third cylinder coupled between the two cylinders) and may be coupled to the center of the back surface 324 of the phantom 800. The first handle 802 and the second handle 804 may allow the phantom 800 to be easily picked up and handled without a cover such as cover 600.

[0050] FIG. 9A shows a mechanical indicator 902 that may be integrated into a plug base (e.g., plug base 316) of a phantom such as phantom 300. FIG. 9B is an enlarged, separated view of the mechanical indicator 902. Specifically, FIG. 9A is a cross-sectional view of a simplified version of phantom 300 showing cross-sections of plug 314 and plug base 316. The mechanical indicator 902 may be positioned above plug 314 within plug base 316, and may be positioned such that a contact end 904 of the mechanical indicator 902 is positioned outside of plug base 316 and configured to contact a patient table above an accessory slot in the patient table when plug 314 is installed in the accessory slot. The contact end 904 may be hemispherical and coupled to a cylindrical body 906 of the mechanical indicator 902. The cylindrical body 906 may be hollow and may house a spring that surrounds a bolt. The mechanical indicator 902 may further include a vertical indicator body 908 that houses a vertical extension of the bolt within the cylindrical body 906. The vertical indicator body 908 may include an upper surface comprising a first indicator 910 and a second indicator 912. The first indicator 910 and the second indicator 912 may be visible from the outside of the plug base 316 (e.g., the plug base 316 may include an opening on its upper surface, with the first indicator 910 or the second indicator 912 being visible through the opening). The second indicator 912 may be visible through the opening in the surface of the plug base 316 when the phantom plug 314 is not secured in a desired position in the accessory slot. However, when mechanical pressure is applied to the mechanical indicator 902, such as when the plug 314 is secured in the accessory slot and the contact end 904 is brought into contact with a patient table, the vertical indicator body 908 may move relative to the plug base 316, and the first indicator 910 may become visible through the opening in the surface of the plug base 316.In one example, the first indicator 910 may be a different color than the second indicator 912 (e.g., the first indicator 910 may be green and the second indicator 912 may be red, although other methods of visually distinguishing the first indicator 910 and the second indicator 912 are possible). When the first indicator 910 is visible, the user knows that the phantom's plug is fully inserted into the accessory slot and securely connected. When the phantom is removed from the patient table, a spring surrounding the bolt in the cylindrical body 906 urges the mechanical indicator 902 back to its original position where the second indicator 912 is visible. While the mechanical indicator 902 is shown and described as being located on the phantom 300, it should be understood that the mechanical indicator 902 may additionally or alternatively be located on the phantom 700 and / or phantom 800.

[0051] FIG. 10 is a side view of a phantom 700 positioned within a PCCT system such as PCCT system 100, and FIG. 11 is a perspective view of the phantom 700 within a PCCT system such as system 100. FIGS. 10 and 11 are taken together. The phantom 700 is coupled to the table 114 by a plug 710 installed in an accessory slot of the table 114. The phantom 700 may be positioned within the gantry 102 by moving the table 114 horizontally (e.g., along the y-axis) to position the phantom 700 at a desired horizontal location within the gantry 102 (e.g., depending on which stack is being scanned). Additionally, the table 114 may be moved vertically (e.g., along the z-axis) to move the phantom 700 to a desired vertical position such that it is proximate to the x-ray source 104. The x-ray source 104 generates an x-ray radiation beam 106 that strikes the phantom 700 and is attenuated by the phantom 700 before striking the detector 108. The phantom 700 is positioned within the X-ray beam 106 with the X-ray beam 106 intersecting / passing through the first step 709. The width of the X-ray radiation beam 106 is equal to the width of the first step 709. Thus, the X-ray radiation beam 106 is attenuated by the stack of materials made up of the first step 709, the second layer 706, the first layer 704, and the base 702. The horizontal position of the phantom 700 can be adjusted by moving and adjusting the position of the table 114 to scan different stacks.

[0052] 11 , the trapezoidal shape of the phantom 700 matches the shape of the X-ray radiation beam 106. Furthermore, the X-ray source 104 is located on the opposite side of the gantry 102 from the bore in which the phantom 700 is located. The trapezoidal shape of the phantom 700, due to the sloping sides of the phantom 700, allows the phantom 700 to be located near the bottom of the gantry 102. Furthermore, as can be seen in FIG. 10 , the plug 710 may extend from the vertical center of the phantom 700 (e.g., the center of the thickest part of the phantom 700, which may be the stack including the second step 711); therefore, approximately half of the phantom 700 may extend below the plug 710, and at least a portion of the phantom may extend below the table 114. This configuration allows the phantom 700 to be positioned closer to the bottom of the bore (and thus the X-ray source 104) than, for example, a configuration in which the phantom is placed on the table 114, while still maintaining a safe position during the scan. During a calibration scan, the gantry 102 may be positioned so that the X-ray source 104 is at its lowest vertical position. Therefore, positioning the phantom 700 as shown allows the phantom 700 to be as close as possible to the X-ray source 104 during the calibration scan, thereby allowing for a relatively thin layer of phantom material to obtain projection data of sufficient quality. If the phantom were positioned farther from the X-ray source 104 during the scan, a thicker layer of phantom 700 may be required to obtain high-quality projection data. Additionally, as shown in FIG. 10 , the plug base 712 may have sloped sides that match the angle of the front surface of the table 114. 10 such that the angled side of the plug base contacts the front surface of the table 114. In some embodiments, the front surface of the table 114 may include foam inserts to ensure a snug fit between the plug base 712 and the front surface of the table 114.

[0053] 10 and 11 show phantom 700 positioned in system 100, it should be understood that phantom 300 and / or phantom 800 may be positioned in system 100 in a similar manner. For example, phantom 300 may be positioned in front of table 114 by inserting plug 314 into the accessory slot until plug base 316 of phantom 300 contacts the front surface of table 114. Table 114 may be moved vertically and horizontally to position the desired stack of phantoms 300 in the path of x-ray radiation beam 106. Phantom 300 may be extended with base 302 above x-ray source 104 and a portion of base 302 below table 114.

[0054] FIG. 12 illustrates a method 1200 for using a phantom such as phantom 300 to calibrate a CT scanner, such as the PCCT system shown in FIG. 1 . At least some aspects of method 1200 can be stored in memory and executed by one or more processors of the PCCT system, for example, via the computing device 216. At 1202, method 1200 can include inserting the phantom into an accessory slot of a patient table. The phantom includes a plug configured to mate with the accessory slot of the patient table. When the plug is fully inserted into the accessory slot, the weight of the phantom is supported by the plug secured in the accessory slot, and the phantom is securely secured to the patient table. The phantom can include a handle (integrated with the phantom or on a cover configured to be removably disposed on / around the phantom) to be manipulated by one or more users to insert the plug into the accessory slot. At 1204, the method can include initiating a scan sequence to calibrate the PCCT system. The scan sequence can be initiated by the computing device in response to user input. At 1206, performing the scan sequence may include moving a table to a first position to center a first stack of the phantom at a scan position (e.g., a position where the first stack is in the path of an X-ray beam generated by an X-ray source of the PCCT system). In an example where the phantom 300 is scanned, the first stack may include a base and a first layer. The table may be positioned so that the first stack is centered in the X-ray beam and intercepts the entire X-ray beam. At 1208, performing the scan sequence may include scanning the first stack. Scanning the first stack may include the PCCT system generating an X-ray beam that is attenuated by the first stack and detecting photons of the attenuated X-ray beam with a detector of the PCCT system.In 1210, executing the scan sequence may include moving the table position to center the next stack at the scan location. The next stack may be adjacent to the first stack on the phantom. For example, the second stack of phantom 300 may include a base, a first layer, and a second layer. The table may be moved laterally to center the next stack at the scan location. The trapezoidal shape of the phantom may allow for stacks with more layers to match the width of the x-ray beam at the surface of the stack without moving the patient table up or down. However, the table may be moved up or down to adjust the position of the phantom, particularly before scanning the stack. In 1211, the scan sequence may include scanning the next stack in the same manner as the first stack was scanned in 1206. In 1212, the scan sequence may include determining whether all stacks have been scanned. If all stacks have not been scanned, the scan sequence may proceed to 1210 to center the next stack (e.g., a third stack, which may include a base, a first layer, a second layer, and a first step of a third layer; or a fourth stack, which may include a base, a first layer, a second layer, and a second step of a third layer). The table movement and stack scanning may be repeated until all stacks have been scanned. If all stacks have been scanned at 1212, the scan sequence may include indicating that the scan sequence is complete at 1214. If the scan sequence is complete, method 1200 may include removing the phantom from the accessory slot at 1216.

[0055] Thus, the base and multiple layers of the phantom each form multiple vertical stacks configured to intersect with an X-ray beam during a calibration scan. The multiple vertical stacks may include a first vertical stack including the base and the first layer (but not the second or third layer). During the calibration scan, the first vertical stack may be scanned with the table in a first position so that the X-ray beam intersects the first vertical stack (but not the other vertical stacks of the phantom). The multiple vertical stacks may further include a second vertical stack including the base, the first layer, and the second layer (but not the third layer). During the calibration scan, the second vertical stack may be scanned with the table in a second position so that the X-ray beam intersects the second vertical stack (but not the other vertical stacks of the phantom). The multiple stacks may further include a third vertical stack including the base, the first layer, the second layer, and a first step (e.g., thickness) of the third layer. During the calibration scan, the third vertical stack may be scanned with the table in a third position such that the x-ray beam intersects the third vertical stack (and not the other vertical stacks in the phantom). The multiple vertical stacks may include a fourth vertical stack including a base, a first layer, a second layer, and a second step (e.g., thickness) of the third layer. During the calibration scan, the fourth vertical stack may be scanned with the table in a fourth position such that the x-ray beam intersects the fourth vertical stack (and not the other vertical stacks in the phantom).

[0056] It should be understood that a scan sequence may include scanning the stacks in reverse order (e.g., starting with the fourth stack and ending with the first stack). Additionally, depending on the desired calibration, not all stacks may be scanned. For example, some calibrations may dictate scanning only one stack (e.g., the third stack), while other calibrations may dictate scanning only two or three stacks. By utilizing the integrated phantoms disclosed herein (e.g., Phantom 300, Phantom 700, or Phantom 800), one or more desired stacks may be scanned without adjusting the phantom between stack scans other than moving the table to the desired scan position.

[0057] The present disclosure also provides a support for a phantom for calibrating an imaging system, the support including: a base comprised of a first material; a plurality of layers positioned on the base, each layer of the plurality of layers comprised of the first material or one or more additional materials; and a plug coupled to a front face of the base and the plurality of layers, the plug configured to couple to an accessory slot of a patient table of the imaging system. In a first example of the system, the plurality of layers includes a first layer positioned on the base, a second layer positioned on the first layer, and a third layer positioned on the second layer.In a second example of the system, optionally including the first example, the base has a first length from the front face of the base to a back face of the base, wherein the first layer has the first length, wherein the second layer has a second length equal to or shorter than the first length, and wherein the third layer has a third length equal to or shorter than the second length. In a third example of the system, optionally including one or both of the first and second examples, the base has a first height from a bottom of the base to a top of the base, wherein the first layer has a second height, smaller than the first height, and wherein the second layer has a third height, larger than the second height.In a fourth example of the system, optionally including one or more or each of the first through third examples, the third layer comprises a first step and a second step, wherein the first step has the third height, and wherein the second step has a fourth height, larger than the third height. In a fifth example of the system, optionally including one or more or each of the first through fourth examples, the phantom has slanted sides to form a trapezoid shape, such that a first width of the base is narrower than a second width of the first layer, a third width of the second layer is wider than the second width, and a fourth width of the third layer is wider than the third width.In a sixth example of the system, optionally including one or more or each of the first through fifth examples, the base and the plurality of layers form a plurality of vertical stacks each configured to intersect an X-ray beam during a calibration scan.In a seventh example of the system, optionally including one or more or each of the first through sixth examples, the plurality of vertical stacks includes a first vertical stack that includes the base and the first layer, a second vertical stack that includes the base, the first layer, and the second layer, a third vertical stack that includes the base, the first layer, the second layer, and a first step of the third layer, and a fourth vertical stack that includes the base, the first layer, the second layer, and a second step of the third layer.In an eighth example of the system, optionally including one or more or each of the first through seventh examples, the system further comprises: a first handle extending on a first side of the base and a second handle extending on a second side of the base. In a ninth example of the system, optionally including one or more or each of the first through eighth examples, the system further comprises: a first arm and a second arm each extending out from the front face of the base and the plurality of layers, a fastening plate coupled to the first arm and the second arm, and a plug base coupled to the fastening plate, wherein the plug extends out from the plug base.In a tenth example of the system, optionally including one or more or each of the first through ninth examples, the system further comprises a first handle extending on the back of the base and a second handle extending from the first arm and the second arm. In an eleventh example of the system, optionally including one or more or each of the first through tenth examples, the system further comprises a mechanical indicator configured to visually indicate a position of the phantom relative to the patient table.

[0058] The present disclosure also provides a support for a phantom system for an imaging system, the phantom including: a body including a base made of a first material; multiple layers disposed on the base, each layer made of the first material or one or more additional materials; a plug; a plug base coupled between the plug and the body, the plug configured to couple to an accessory slot in a table of the imaging system; and a cover configured to house the phantom. In a first embodiment of the system, the cover includes an integrated handle. In a second embodiment of the system, optionally including the first embodiment, the cover includes a hollow interior accessible through a top, bottom, two side, and front openings. In a third embodiment of the system, optionally including one or both of the first and second embodiments, the hollow interior is defined by the inner surfaces of the top, bottom, and two side surfaces and has a size and shape complementary to the size and shape of the body of the phantom. In a fourth embodiment of the system, optionally including one or more or each of the first to third embodiments, when the phantom is housed within the cover, the base and the plurality of layers are disposed within the hollow interior and the plug is disposed outside the cover.

[0059] The present disclosure also provides support for a method for calibrating an imaging system, including: positioning a phantom within a bore of the imaging system by moving a table of the imaging system, the phantom being coupled to the table via a phantom plug housed in an accessory slot of the table, the phantom including a body coupled to the plug, the step and the body including a base constructed of a first material and multiple layers disposed on the base, each layer of the multiple layers being constructed of the first material or one or more additional materials; scanning a first vertical stack of bodies, the first vertical stack including at least the base and the first layer of the multiple layers; in a first embodiment of the method, the first vertical stack includes only the base and the first layer, and further scanning a second vertical stack of bodies, the second vertical stack including the base, the first layer, and a second layer of the multiple layers, and moving the table between scanning the first vertical stack and scanning the second vertical stack. In a second embodiment of the method, optionally including the first embodiment, positioning the phantom in the bore of the imaging system by moving the table includes moving the table horizontally to position the phantom at a first scan position for scanning the first vertical stack, and moving the table vertically to position the phantom at a defined position relative to an X-ray source of the imaging system.

[0060] 3-11 and 13 illustrate example configurations with relative positional relationships of various components. When elements are shown in direct contact with or directly coupled to each other, such elements may, in at least one example, be referred to as being in direct contact with or directly coupled to each other, respectively. Similarly, elements shown continuous or adjacent to each other may, in at least one example, be continuous or adjacent, respectively. As an example, components laid out in surface contact with each other may be referred to as being in surface contact. As another example, in at least one example, elements spaced apart from each other with only a space between them and no other components may be referred to as such. As yet another example, elements shown above / below each other, opposite each other, or to the left / right of each other may be referred to as such relative to each other. Furthermore, as shown in the figures, in at least one example, the topmost element or point of an element may be referred to as the “top” of the element, and the bottommost element or point of an element may be referred to as the “bottom” of the element. As used herein, top / bottom, upper / lower, above / below are relative to the vertical axis of the figure and may be used to describe the positional relationship of elements of the figure relative to one another. Thus, elements shown above other elements are, in one example, vertically disposed above the other elements. As yet another example, the shapes of elements depicted in the figures may be referred to as having those shapes (e.g., circular, rectilinear, flat, curved, rounded, chamfered, angled, etc.). Furthermore, elements shown to intersect one another may, in at least one example, be referred to as intersecting elements or intersecting elements. Furthermore, elements shown within or outside of other elements may, by way of example, be so referred to.

[0061] When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” and “the” are intended to mean the presence of one or more of the element. The terms “first,” “second,” etc. do not denote order, quantity, or importance, but rather are used to distinguish one element from another. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. As used herein, terms such as “connected,” “coupled,” etc., refer to one object (e.g., a material, element, structure, member, etc.) being connected to or coupled to another object, regardless of whether the one object is directly connected or coupled to the other object, or whether there are one or more intervening objects between the one object and the other object. Additionally, references to “one embodiment” or “an embodiment” in the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the referenced features.

[0062] In addition to the modifications set forth above, numerous other variations and alternative arrangements may be devised by those skilled in the art without departing from the spirit and scope of the present specification, and the appended claims are intended to cover such modifications and arrangements. Thus, while the present specification has been described above with specificity and detail in connection with what are presently considered to be the most practical and preferred embodiments, it will be apparent to those skilled in the art that numerous changes, including but not limited to form, function, method of operation, and method of use, can be made without departing from the principles and concepts described herein. Moreover, the examples and embodiments, as used herein, are intended to be illustrative in all respects and should not be construed as limiting in any manner. [Explanation of symbols]

[0063] 100: PCCT system 100 / photon counting X-ray imaging system 102: Gantry 104: X-ray source 106: X-ray radiation beam 108: Detector array 110: Image processing unit 112: Subject 114: Table 200: Imaging system 202: Cell / detector element 204: Subject 206: Center of rotation 208: Control mechanism 210: X-ray controller 212: Gantry motor controller 213: Slip ring 214: Data acquisition system / DAS 216: Computing device 218: Storage / mass storage device 220: Operator console 224: Picture archiving and communication system / PACS 226: Table motor controller 230: Image reconstructor 232: Display / display device 300: Phantom 301: Cartesian coordinate system 302: Base 303: Body 304: First layer 305: First side 306: Second layer 307: Second side 308: Third layer 309: Front surface 310: Joint 311: Longitudinal axis 312: Fastening plate 313: Longitudinal axis 314: Plug 315: Plug section 316: Plug base 318: First step 320: Second step 322: Front base 324: Back base 325: First length 326: Base bottom 327: First width 328: Base top 329: Second width 330: First base side 331: Third width 332: Second base side 333: Second length 334: Angle 335: Fourth width 336: First layer bottom 337: Length 338: First layer top 339: length 340: angle 341: length 342: first layer front 343: fifth width 344: first layer first side 345: sixth width 346: first layer second side 348: second layer bottom 350: second layer top 352: second layer first side 354;Second layer second side 356: Second layer front 358: Angle 360: First L-shaped side 362: Second L-shaped side 364: Third layer bottom 366: First step top 368: Second step top 370: Third layer front 372: Angle 374: First arm 376: Second arm 378: First rounded corner 380: Third rounded corner 382: Second rounded corner 384: Fourth rounded corner 386: First arm front 388: Second arm front 390: Vertical side 392: Plug top 394: Plug bottom 396: Sloped side 398: Top 600: Cover 602: Second handle 604: First handle 606: Bottom 608: Flat top 609: Top 610: First side 612: Second side 614: Sloped top 616: Back of cover 618: First rectangular protrusion 620: Second rectangular protrusion 622: Third rectangular protrusion 624: Front of cover 625: Inner periphery 626: Front edge 628: First top edge 630: Second top edge 632: Rear edge 634: Bottom edge 636: Handle edge 638: Rounded edge 640: Roof 700: Phantom 702: Base 703: Body 704: First layer 705: Plug 706: Second layer 708: Third layer 709: First step 710: Plug 711: Second step 712: Plug base 714: First fastening protrusion 715: Handle 716: Second fastening protrusion 717: Fourth fastening protrusion 718: Rectangular coupling base 720: First fastener 722: Second fastener 730: First height 732: Second height 800: Phantom 802: First handle 804: Second handle 806: First cylinder 808: Second cylinder 810: Third cylinder 816: First rounded corner 818: Second rounded corner 902: Mechanical indicator 904: Contact tip 906: Cylindrical body 908: Vertical indicator body 910: First indicator 912: Second indicator;

Claims

1. 1. A phantom for calibrating an imaging system, comprising: a base constructed from a first material; a plurality of layers disposed on the base, each layer of the plurality of layers being composed of the first material or one or more additional materials; a plug coupled to the base and a front surface of the plurality of layers, the plug configured to couple to an accessory slot of a patient table of the imaging system; Including, Phantom.

2. 2. The phantom of claim 1, wherein the plurality of layers includes a first layer disposed on the base, a second layer disposed on the first layer, and a third layer disposed on the second layer.

3. 3. The phantom of claim 2, wherein the base has a first length from a front surface of the base to a back surface of the base, the first layer has the first length, the second layer has a second length that is equal to or less than the first length, and the third layer has a third length that is equal to or less than the second length.

4. 3. The phantom of claim 2, wherein the base has a first height from a bottom of the base to a top of the base, the first layer has a second height less than the first height, and the second layer has a third height greater than the second height.

5. 5. The phantom of claim 4, wherein the third layer has a first step and a second step, the first step having the third height, and the second step having a fourth height greater than the third height.

6. 3. The phantom of claim 2, wherein the phantom has sloped sides such that the phantom forms a trapezoidal shape, such that a first width of the base is narrower than a second width of the first layer, a third width of the second layer is wider than the second width, and a fourth width of the third layer is wider than the third width.

7. The phantom of claim 2 , wherein the base and the plurality of layers respectively form a plurality of vertical stacks configured to intersect an x-ray beam during a calibration scan.

8. 8. The phantom of claim 7, wherein the plurality of vertical stacks include a first vertical stack including the base and the first layer, a second vertical stack including the base, the first layer, and the second layer, a third vertical stack including the base, the first layer, the second layer, and a first step of the third layer, and a fourth vertical stack including the base, the first layer, the second layer, and a second step of the third layer.

9. The phantom of claim 1 , further comprising a first handle extending from a first side of the base and a second handle extending from a second side of the base.

10. 2. The phantom of claim 1, further comprising: a first arm and a second arm extending from a front surface of the base and the plurality of layers, respectively; a fastening plate coupled to the first arm and the second arm; and a plug base coupled to the fastening plate, the plug extending from the plug base.

11. The phantom of claim 10 , further comprising a first handle extending from a rear surface of the base and a second handle extending from the first arm and the second arm.

12. The phantom of claim 1 , further comprising a mechanical indicator configured to visually indicate the position of the phantom relative to the patient table.

13. 1. A phantom system for an imaging system, comprising a phantom, The phantom is a body including a base made of a first material and a plurality of layers disposed on the base, each layer of the plurality of layers being made of the first material or one or more additional materials; Plug and a plug base coupled between the plug and the body, the plug configured to couple to an accessory slot of a table of the imaging system; and Including, The phantom system comprises: A phantom system including a cover configured to house the phantom.

14. The phantom system of claim 13 , wherein the cover includes an integrated handle.

15. The phantom system of claim 13 , wherein the cover includes a hollow interior accessible via a top, a bottom, two side, and a front opening.

16. 16. The phantom system of claim 15, wherein the hollow interior is defined by the inner surfaces of the top, bottom, and two sides and has a size and shape complementary to the size and shape of the body of the phantom.

17. 17. The phantom system of claim 16, wherein when the phantom is housed within the cover, the base and the plurality of layers are disposed within the hollow interior and the plug is disposed outside the cover.

18. 1. A method of calibrating an imaging system, comprising: positioning a phantom within a bore of an imaging system by moving a table of the imaging system, the phantom being coupled to the table via a plug of the phantom housed in an accessory slot of the table, the phantom including a body coupled to the plug, the body including a base comprised of a first material and a plurality of layers positioned on the base, each layer of the plurality of layers being comprised of the first material or one or more additional materials; scanning a first vertical stack of said bodies; wherein the first vertical stack includes at least the base and a first layer of the plurality of layers.

19. 20. The method of claim 18, wherein the first vertical stack includes only the base and the first layer, further comprising scanning a second vertical stack of the body, the second vertical stack including the base, the first layer, and a second layer of the plurality of layers, and the table is moved between scanning the first vertical stack and scanning the second vertical stack.

20. 20. The method of claim 18, wherein positioning the phantom in the bore of the imaging system by moving the table comprises: moving the table horizontally to position the phantom at a first scan position for scanning the first vertical stack; and moving the table vertically to position the phantom at a defined position relative to an x-ray source of the imaging system.

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