System and method for x-ray tube

Abstract

To provide a method and system for preventing a hot landing of a motor of an X-ray imaging system at the time of power loss.SOLUTION: In one example, a method for an X-ray tube of an imaging system includes: a step for supplying the X-ray tube with an energy from a main power source for rotating a target of the X-ray tube during a scanning of the subject by the imaging system; a step for selectively collecting the energy from the X-ray tube and storing the collected energy in an energy storage circuit of the imaging system; and a step for detecting a loss of the main power source, and in response supplying the energy from the energy storage circuit to the X-ray tube to rotate the target at the threshold speed.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] FIELD OF THE INVENTION Embodiments of the subject matter disclosed herein relate to imaging systems and methods, and more particularly to controlling the rotation assembly of an x-ray tube in a computed tomography (CT) imaging system. [Background technology]

[0002] In a computed tomography (CT) imaging system, an electron beam generated by a cathode is directed at a target inside an x-ray source or x-ray tube. A fan- or cone-shaped beam of x-rays is generated by the electrons colliding with the target and directed at a subject, such as a patient. After being attenuated by the object, the x-rays strike an array of x-ray detectors to form an image. In some examples, the target can be configured to rotate, allowing the focal spot on the target to be struck by the electron beam periodically, rather than continuously, to disperse the resulting thermal energy. In some examples, the target can be an anode. Summary of the Invention

[0003] In one example, a method for an x-ray tube in an imaging system includes supplying energy from a mains power supply to the x-ray tube to rotate a target of the x-ray tube while the imaging system is scanning a subject, selectively recovering energy from the x-ray tube and storing the recovered energy in an energy storage circuit of the imaging system, and detecting a loss of the mains power supply and, in response, supplying energy from the energy storage circuit to the x-ray tube to rotate the target at a threshold speed.

[0004] These and other advantages and features of the present description 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 present various concepts in a simplified form that are further described in the Detailed Description. Such description is not intended to identify key or essential features 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 any disadvantages described above or elsewhere in this disclosure. [Brief explanation of the drawings]

[0005] Various aspects of the present disclosure will be more fully understood upon reading the following detailed description and upon consideration of the accompanying drawings.

[0006] [Figure 1] FIG. 1 is a diagram of a computed tomography (CT) imaging system in accordance with one or more embodiments of the present disclosure. [Figure 2] FIG. 1 is a block diagram of an example CT imaging system in accordance with one or more embodiments of the present disclosure. [Figure 3] FIG. 1 is a schematic diagram of an example of a CT imaging system in which an energy storage and recovery system is coupled to a motor in a first example configuration. [Figure 4] FIG. 1 is a schematic diagram of an example of a CT imaging system in which an uninterruptible power supply and an energy storage and recovery system are coupled to a motor in a first example configuration. [Figure 5] FIG. 10 is a schematic diagram of an example of a CT imaging system in which an uninterruptible power supply and an energy storage and recovery system are coupled to a motor in a second example configuration. [Figure 6] 1 is a schematic diagram of a first example of a hardware configuration for a self-contained hot shutdown protection system including an energy storage and recovery system; [Figure 7] FIG. 2 is a schematic diagram of a second example of a hardware configuration for a self-contained hot shutdown protection system. [Figure 8] FIG. 10 is a schematic diagram of a third example of a hardware configuration for a self-contained hot shutdown protection system. [Figure 9] 1 is a time domain plot of the characteristics of a CT system operating under a first energy recovery scheme with mains power; [Figure 10] 1 is a time domain plot of the characteristics of a CT system operating under a first energy recovery strategy when a mains power outage occurs during an exposure. [Figure 11] 1 is a time domain plot of the characteristics of a CT system operating under a first energy recovery strategy when a mains power outage occurs after an exposure. [Figure 12A] 1 is a flow chart illustrating a method for a first energy recovery plan. [Figure 12B] 1 is a flow chart illustrating a method for a first energy recovery plan. [Figure 13] 10 is a time domain plot of the characteristics of a CT system operating under a second energy recovery scheme with mains power; [Figure 14] 10 is a time domain plot of the characteristics of a CT system operating under a second energy recovery scheme when a mains power outage occurs. [Figure 15A] 10 is a flow chart illustrating a method for a second energy recovery plan. [Figure 15B] 10 is a flow chart illustrating a method for a second energy recovery plan. DETAILED DESCRIPTION OF THE INVENTION

[0007] This description and embodiments of the subject matter disclosed herein relate to methods and systems for storing energy generated by a rotating assembly of an X-ray tube within an X-ray generator and using the stored energy to continue the rotation of the rotating assembly and the operation of a cooling system if the X-ray generator loses power from a main power source. The X-ray generator may be part of an imaging system, such as a computed tomography (CT) imaging system. During imaging with an imaging system (e.g., a CT system), X-ray exposure may be performed via the X-ray generator. The X-ray exposure may include a beam of X-rays generated by the X-ray generator (e.g., an X-ray tube) and directed at a subject. The X-rays may be attenuated by the subject and measured by an X-ray detector. In a CT system, a thin beam of X-rays is generated by the X-ray tube, and the X-ray tube and X-ray detector are rotated around the subject to obtain multiple views that may be reconstructed into one or more images.

[0008] In some examples, an x-ray tube may include a rotating assembly rotated at high frequencies by a motor. The motor may include a rotating bearing component called a sleeve, a stationary bearing component called a shaft, a rotor, and a stationary stator. The x-ray tube / motor may thus include a rotating assembly including a target such as an anode, a sleeve, and a rotor. The motor can rotate the target at high speeds (e.g., greater than 50 Hz), which can cause the temperature to rise during x-ray exposure. The rotating assembly may be supported by liquid metal bearings (LMBs), which can absorb and dissipate excess heat. The LMBs can experience significant temperature increases during x-ray exposure. If the rotating assembly is stopped from rotating when the LMB temperature is high, the LMB may transfer excessive energy to certain areas of the LMB, causing the rotating portion of the bearing (e.g., the rotor sleeve) to melt and adhere to the stationary portion of the bearing. A rotor stopping rotation while the LMB temperature is high is sometimes referred to as a hot landing. If the bearing shaft melts and adheres to the bearing sleeve, the motor may become inoperable and the X-ray tube may need to be replaced to restore the X-ray generating system to operation. X-ray tubes are one of the most expensive components in a CT system, and avoiding X-ray tube replacements can save money.

[0009] A hot trip can occur during a power outage or if the X-ray generator is unplugged while in operation. In some cases, the X-ray generator may not include a backup power system to power the cooling system integrated into the X-ray generation system or to keep the rotating assembly and LMB rotating. Maintaining power to the coolant pump and keeping the rotating assembly rotating until the LMB cools to a suitable temperature can prevent the sleeve from melting and adhering to the shaft.

[0010] Thus, according to embodiments disclosed herein, an energy recovery, storage, and distribution system for an X-ray imaging system, such as a CT system, can prevent hot trips. The energy recovery, storage, and distribution system can include a motor / generator and a self-contained hot trip protection system. The motor / generator can be configured to rotate a target on a rotating assembly of an X-ray tube of the imaging system when supplied with energy. During certain conditions, such as when the rotating assembly is rotating at a reduced speed, the motor / generator can convert the mechanical energy of the rotating assembly into electrical energy. The electrical energy generated by the motor / generator can be stored and distributed by the self-contained hot trip protection system to prevent hot trips. The self-contained hot trip protection system can include energy storage circuitry and hardware that facilitates distribution of electrical energy to the motor and to a pump of a cooling system configured to cool the motor. Storing mechanical energy from the rotating assembly as electrical energy during operation of the X-ray tube can enable the stored electrical energy to rotate the rotating assembly and power the pump of the cooling system in the event of a power outage. In some example systems, energy from the rotating assembly can be recovered at every moment of deceleration of the rotating assembly, while in other examples, energy from the rotating assembly can be recovered and utilized only when a power outage occurs in the system. In examples where the imaging system includes or is coupled to an uninterruptible power supply (UPS), an energy recovery, storage, and distribution system can operate in parallel with the UPS to power the cooling system and motor while the UPS provides energy to other components of the imaging system. Systems and methods for storing and utilizing power to prevent hot shutdowns, described in more detail below, can prevent bearing sleeves from melting and adhering to the shaft, thereby preventing x-ray tube replacement.

[0011] As described above, the energy recovery, storage, and distribution system can be included as part of the X-ray system of a computed tomography (CT) system. An example of a CT system is shown in FIGS. 1 and 2. The energy recovery, storage, and distribution system can be integrated into the CT system in several configurations, as shown in FIGS. 3 through 5. Various electrical coupling configurations between the self-contained hot stop protection system, the motor, and additional components of the CT system are shown in FIGS. 6 through 8. A first energy recovery strategy involves recovering energy from the rotor each time the rotor decelerates following an X-ray exposure. An X-ray exposure can be a period during which X-rays are generated, which are typically irradiated onto the subject and measured by a detector array. During an exposure, a gantry containing an X-ray generator, an X-ray tube, an X-ray detector, and associated power electronics can rotate around the target to capture multiple views. Under the first energy recovery strategy, stored energy can be used to accelerate the rotating assembly to an appropriate speed for a predetermined period before an exposure occurs. In some examples, this predetermined period of time may be between 1 and 10 seconds or longer, although it should be appreciated that the rotating assembly may be accelerated to an appropriate speed well before the exposure actually occurs. When the exposure is terminated, there may be a predetermined delay between the termination of the exposure and the initiation of the energy recovery sequence. In one example, the delay may be between 1 and 10 seconds or longer, depending on when the deceleration of the rotating assembly occurs.

[0012] Figures 9-11 are plots over time of the energy recovery and distribution process during operation of the CT system according to a first energy recovery scheme, and an example method for this is shown in Figures 12(A) and 12(B). A second energy recovery scheme involves recovering and storing energy from the rotating assembly only if a power outage occurs. Figures 13 and 14 are plots over time of the energy recovery and distribution process during operation of the CT system according to a second energy recovery scheme, and an example method for this is shown in Figures 15(A) and 15(B).

[0013] FIG. 1 illustrates an exemplary computed tomography (CT) system 100 configured for CT imaging. Specifically, 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 body present in the body, such as a dental implant, a stent, and / or a contrast agent. CT system 100 includes a gantry 102, which may further include at least one X-ray source 104 configured to project a beam 106 of X-ray radiation (see FIG. 2 ) that is used to image subject 112 residing on a table 114. Specifically, X-ray source 104 is configured to project beam 106 of X-ray radiation toward a detector array 108 disposed on the opposite side of gantry 102. While FIG. 1 illustrates a single X-ray source 104, in some embodiments, multiple X-ray sources and detectors may be used to project multiple beams of X-ray radiation to acquire projection data at the same or different energy levels corresponding to the patient. In some embodiments, the X-ray source 104 may enable dual-energy spectral imaging with rapid peak kilovoltage (kVp) switching. In some embodiments, the X-ray detector used is a photon-counting detector capable of discriminating between X-ray photons of different energies. In other embodiments, the X-ray detector is an energy-integrating detector, where the detected signal is proportional to the total energy deposited by all photons without specific information about each individual photon or its energy. In some embodiments, two sets of X-ray sources and detectors are used, one set at low kVp and the other at high kVp, to generate dual-energy projections.

[0014] In some embodiments, the CT system 100 further includes an image processor unit 110 configured to reconstruct an image of a target volume of the subject 112 using an iterative or analytical image reconstruction method. For example, the image processor unit 110 may reconstruct an image of the target volume of the subject 112 using an analytical image reconstruction approach such as filtered back projection (FBP). As another example, the image processor unit 110 may reconstruct an image 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 unit 110 may use an analytical image reconstruction approach such as FBP in addition to an iterative image reconstruction approach. In some embodiments, the image processor unit 110 may use a direct image reconstruction approach, such as using a neural network trained with deep learning.

[0015] In some CT imaging system configurations, an x-ray source projects a cone-shaped x-ray beam defined with respect to an XYZ Cartesian coordinate system, commonly referred to as the "imaging volume." The x-ray radiation beam passes through an imaging object, such as a patient or subject. 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 beam received at the detector array depends on the attenuation of the x-ray radiation beam by the object. Each x-ray detector element in the array generates a separate electrical signal, which is a measurement of the x-ray beam attenuation at the detector location. Attenuation measurements from all detector elements are acquired separately to generate a transmission profile.

[0016] In some CT systems, the x-ray source and detector array are rotated around the object within the imaging volume by a gantry so that the angle at which the x-ray beam intersects the object is constantly changing. A group of x-ray radiation attenuation measurements, e.g., projection data, from the detector array at one gantry angle is called a "view." A "scan" of an object includes a set of views made at different gantry angles, or view angles, during one rotation of the x-ray source and detector. Because it is contemplated that the benefits of the methods described herein may be obtained with medical imaging modalities other than CT, the term "view" as used herein is not limited to its use as described above with respect to projection data from one gantry angle. The term "view" is used to refer to one data acquisition whenever there are multiple data acquisitions from different angles, whether from CT, positron emission tomography (PET), single photon emission CT (SPECT) acquisitions, and / or any other modality, including modalities under development, and combinations thereof in fused or hybrid embodiments.

[0017] The projection data is processed to reconstruct an image corresponding to a two-dimensional slice through the object, or, in some instances where the projection data includes multiple rotations or scans of a two-dimensional (2D) array of detectors, to reconstruct an image corresponding to a three-dimensional (3D) rendering of the object. One method for reconstructing an image from a set of projection data is referred to in the art as a filtered backprojection technique. Transmission and emission tomography reconstruction techniques also include iterative reconstruction techniques, as well as statistical iterative methods such as maximum likelihood expectation maximization (MLEM) and ordered subset expectation reconstruction. This process can convert attenuation measurements from the scan into values ​​called "CT numbers" or "Hounsfield units" (HU), which are used to control the brightness of corresponding pixels on a display device.

[0018] To reduce the total scan time, a "helical" scan can be performed. To perform a "helical" scan, the patient is moved while data for a predetermined number of slices is acquired. In such a system, the position of the source relative to the patient describes a spiral. The spiral mapped out by the source produces projection data from which an image in each predetermined slice can be reconstructed.

[0019] The phrase "reconstructing an image," as used herein, is not intended to exclude embodiments of the invention in which data representing an image is generated but no visible image is formed. Thus, as used herein, the term "image" broadly refers to both a visible image and data representing a visible image. However, many embodiments form (or are configured to form) at least one visible image.

[0020] FIG. 2 illustrates an exemplary imaging system 200 similar to the CT system 100 of FIG. 1. In accordance with an aspect of the present disclosure, the imaging system 200 is configured to image a subject 204 (e.g., subject 112 of FIG. 1). In some embodiments, 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 collectively 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 may be fabricated in 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.

[0021] In some embodiments, imaging system 200 is configured to traverse different angular positions about object 204 to acquire desired projection data. Thus, gantry 102 and components mounted to gantry 102 may be configured to rotate about center of rotation 206 to acquire projection data at different energy levels, for example. Alternatively, in embodiments where 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 the arc of a circle.

[0022] 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 examples, 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.

[0023] The acquired projection data set may be subjected to basis material decomposition (BMD). During BMD, the measured projections are converted into a set of material density projections. The material density projections can be reconstructed to form a set of material density maps or images of each respective basis material, such as a bone map, a soft tissue map, and / or a contrast agent map. These density maps or images can then be correlated to form a 3D volumetric image of the basis materials, e.g., bone, soft tissue, and / or contrast agent, in the imaged volume.

[0024] Once reconstructed, the basis material image formed by the imaging system 200 reveals internal features of the subject 204, represented as the densities of two basis materials. The density image may be displayed to show these features. In a traditional approach to diagnosing a medical condition, such as a disease state or, more generally, a medical event, a radiologist or physician examines a hard copy or display of the density image to identify salient features of interest. Such features may include lesions, the size and shape of particular anatomical structures or organs, and other features that may be identified in the image based on the skill and knowledge of the individual physician.

[0025] In one embodiment, imaging system 200 includes a control mechanism 208 that controls 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.

[0026] In some 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 sum data from a subset of the detector elements 202 into a so-called macro-detector. The sampled and digitized data by the DAS 214 is communicated via slip rings 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 any type of non-transitory memory and 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.

[0027] 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 some embodiments, the computing device 216 controls system operations based on operator input. The computing device 216 receives operator input, including, for example, commands and / or scanning parameters, via an operator console 220 operatively coupled to the computing device 216. The operator console 220 may include a keyboard (not shown) or a touch screen that allows an operator to specify commands and / or scanning parameters.

[0028] 2 shows one operator console 220, more than one operator console may be coupled to imaging system 200, for example, to input and output system parameters, request exams, plot data, and / or view images. Additionally, in some embodiments, imaging system 200 may be coupled to multiple displays, printers, workstations, and / or similar devices, which may be located locally or remotely, for example, within a facility or hospital, or in entirely different locations, and may be coupled via one or more configurable wired and / or wireless networks, such as the Internet and / or virtual private networks, wireless telephone networks, wireless local area networks, wired local area networks, wireless wide area networks, and wired wide area networks, etc.

[0029] In one embodiment, for example, imaging system 200 may include or be coupled to a picture archiving and communication system (PACS) 224. In one implementation, PACS 224 may be further coupled to a remote system, such as a radiology information system or a hospital information system, and / or a local or external network (not shown), allowing operators at various locations to provide commands and parameters and access image data.

[0030] The computing device 216 uses operator-provided and / or system-defined commands and parameters to operate the table motor controller 226, which in turn may control the table 114, which may be a motorized table. Specifically, the table motor controller 226 may move the table 114 to properly position the subject 204 in the gantry 102 in order to acquire projection data corresponding to a target volume of the subject 204.

[0031] As previously described, 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 depicts image reconstructor 230 as a separate entity, in some embodiments, image reconstructor 230 may form part of computing device 216. Alternatively, image reconstructor 230 may not be present in CT imaging system 200; instead, computing device 216 may perform one or more functions of image reconstructor 230. Also, image reconstructor 230 may be located locally or remotely and operatively connected to imaging system 200 using a wired or wireless network. Specifically, an example embodiment may use the computational resources of a “cloud” network cluster for image reconstructor 230.

[0032] In one embodiment, image reconstructor 230 stores the reconstructed images in storage device 218. Alternatively, image reconstructor 230 may transmit the reconstructed images to computing device 216 to generate patient information useful for diagnosis and evaluation. In some embodiments, computing device 216 may transmit the reconstructed images 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 images may be transmitted from computing device 216 or image reconstructor 230 to storage device 218 for short-term or long-term storage.

[0033] Information can be transferred between components residing in the gantry 102 and external devices (such as the computing device 216 and / or the image reconstructor 230) via slip rings 213 that facilitate electronic communication across the rotating gantry. In some examples, the gantry and its internal components (e.g., the control mechanism 208, the x-ray source 104, and the detector array 108) can be collectively defined as a CT scanner, and as such, the computing device 216 and the image reconstructor 230 can reside external to the scanner.

[0034] The CT system described above with respect to Figures 1 and 2 may be an example of a system that integrates the energy recovery, storage, and distribution systems described below. Figure 3 is a schematic diagram of a CT system 300 that includes an energy recovery, storage, and distribution system. The CT system 300 may include a power distribution unit (PDU) 302. The PDU 302 may be coupled to an external power source, such as a power grid, via an outlet. The PDU 302 may receive power from the external power source and allocate this power to various different electrical components. The PDU 302 may also have protective functions and may be able to disrupt the flow of power through the PDU 302 to prevent power surges from reaching other components of the CT system 300. The PDU may be coupled through a first power distribution path 303 to a number of electronic devices located off the gantry, such as reconstruction hardware 304 (a non-limiting example of an image reconstructor 230), blowers and fans 306, a stationary power board (SPB) 308, an operator console 220, and a table 114, which may therefore be coupled to the gantry via slip rings 213.

[0035] The PDU 302 may further be coupled to a second power distribution path 309 that couples the PDU 302 to each element of the gantry. The second power distribution path may include parallel branches, with a first branch 311 conducting power to the X-ray tube 316 and a second branch 313 conducting power to the auxiliary electronics on the rotating side of the slip ring 213. The first branch 311 may couple the PDU 302 to an X-ray inverter 312. The X-ray inverter 312 is configured to convert the direct current supplied by the PDU 302 into alternating current. The X-ray inverter 312 may generate alternating current at a particular frequency, which may depend on the specifications of the other components of the CT system. The X-ray inverter 312 may be coupled across the slip ring 213 to an X-ray generator 314. The X-ray generator 314 is configured to convert the AC signal supplied by the X-ray inverter to DC current to generate a high voltage that may be applied across the X-ray tube 316. The X-ray tube 316 may include a cathode that emits electrons based on an electric current applied to the cathode filament. The cathode may be positioned a fixed distance from a target 319, which in some instances may be a rotating, disk-shaped anode. When the X-ray generator is turned on, a significant potential difference is generated between the cathode and the anode, creating a voltage difference. Electrons emitted by the cathode may be accelerated toward the target 319 due to the large potential difference. X-rays may be emitted when the anode strikes the target 319. The target 319 is rotated by a motor 321, including a rotor 318 and a stator 324, to dissipate heat generated from electrons striking the target 319. As previously mentioned, the motor 321 may be a motor / generator configured to operate as a motor during some conditions and as a generator during other conditions.

[0036] The stator 324 is a non-rotating component of the motor 321 and can receive power to rotate the rotor 318, which can be a rotating component of the motor 321. The motor 321 / X-ray tube can thereby include a rotating assembly 327 that includes the rotor 318, a sleeve 325 of a liquid metal bearing (LMB) 320, and a target 319. The components of the rotating assembly 327 can be rotatably coupled and rotate when the rotor 318 receives torque from the stator 324. The LMB 320 can include a shaft 322 that remains stationary while the rotating assembly 327 rotates. The LMB 320 can include a rotating sleeve 325 that surrounds the shaft 322. The space between the sleeve 325 and the shaft 322 can be filled with a liquid metal, such as a gallium alloy. In some examples, the shaft 322 and / or the sleeve 325 can include grooves that allow the liquid metal to circulate to a preferred region within the space between the sleeve and the shaft. The rotation of the rotating assembly and the circulation of the liquid metal may act to dissipate heat.

[0037] Coolant circuit 332 may include a cooling passage 326 that fluidly couples tube pump 328 and heat exchanger 330 to motor 321. Coolant passage 326 may include portions that are thermally coupled to one or more components of rotating assembly 327, such as rotor 318, LMB 320, sleeve 325, and / or shaft 322. Coolant passage 326 may be tubing connecting portions of coolant circuit 332 or may be passages integrated into components of X-Ray tube 316, stator 324, tube pump 328, and / or heat exchanger 330. Tube pump 328 may pump coolant from heat exchanger 330 to motor 321 (e.g., around LMB 320), where the coolant accumulates heat from rotating assembly 327. The coolant may be returned to heat exchanger 330 (e.g., via a return path not shown in FIG. 3 ), where heat accumulated in the coolant may be released to the environment.

[0038] A second branch of second power distribution path 309 may couple PDU 302 to auxiliary inverter 310. Auxiliary inverter 310 may convert the direct current provided by PDU 302 to alternating current. Auxiliary inverter 310 may be electrically coupled to rotating auxiliary power unit 334 via slip ring 213. Rotating auxiliary power unit 334 may be capable of directing the flow of power to elements of CT system 300 that rotate within the gantry. Rotating auxiliary power unit 334 may include rectification and filtering board 336, which is a circuit board configured to operate with AC power signals. The frequency range of rectification and filtering board 336 may be between 300 MHz and 3 GHz in some examples. Rectification and filtering board 336 may include electrical components capable of controlling, distributing, and filtering the power received by rotating auxiliary power unit 334 through slip ring 213 so that it is available to multiple electrical devices coupled to rotating auxiliary power unit 334.

[0039] The rectification and filtering board 336 may be coupled to a rotation control board (RCB) 338 and a 48V fuse and control board 340 within the rotating auxiliary power unit 334. The RCB 338 may be coupled to the stator 324 of the motor 321 via multiple cables, which in some examples may include three separate cables surrounded by a conductive shield. The RCB 338 may include a controller, which may include a memory storing instructions for operating the motor 321 and distributing power to devices coupled to the RCB 338, and one or more processors configured to execute the instructions stored in the memory. The RCB 338 may be coupled to an energy storage circuit 342. The energy storage circuit 342 may include one or more batteries, capacitors, and the like configured to store energy. In some examples, the energy storage circuit 342 may include a controller, which may include a memory storing instructions executable by one or more processors to recover and store rotational energy from the rotating assembly 327 as electrical energy. Rotational energy may be recovered as rotating assembly 327 decelerates, converted to electrical energy, and transmitted to RCB 338 within rotating auxiliary power unit 334. The recovered electrical energy may be transmitted from RCB 338 to energy storage circuit 342, where it may be stored in one or more batteries, capacitors, or the like. Energy storage circuit 342 may issue commands to RCB 338 regarding the initiation and termination of the energy recovery process, which may be relayed by RCB 338 to stator 324.

[0040] Energy storage circuit 342 may be coupled to pump circuit 344. Pump circuit 344 may include a controller having a memory storing instructions related to operating tube pump 328 and one or more processors configured to execute the instructions. Pump circuit 344 may be coupled to tube pump 328 and may control the operation of tube pump 328 if a power outage occurs. If a power outage occurs, stored energy from energy storage circuit 342 may be relayed to pump circuit 344 and delivered to tube pump 328 according to instructions stored therein. In the event of a power outage, energy storage circuit 342 may provide power to motor 321 by providing power to RCB 338, which may be distributed to motor 321 according to instructions stored in RCB 338.

[0041] As mentioned above, the rectification and filtering board 336 may be coupled to the 48V fuse and control board 340. The 48V fuse and control board 340 may include a controller, which may include a memory that stores instructions for distributing energy to multiple devices and one or more processors configured to execute the instructions stored in the memory. The 48V fuse and control board 340 may include multiple fuses that may prevent power surges from reaching the devices coupled to the 48V fuse and control board 340. The 48V fuse and control board 340 may power multiple devices by providing a 48V voltage to multiple devices, including the tube pump 328, the detector system 348, and multiple other 48V loads 346.

[0042] The detector system 348 may be configured to detect x-rays emitted by the x-ray tube 316 and passing through the subject 112. The detector system 348 may include a detector power management unit 352, the detector array 108, one or more fans 350, and a heat exchanger 354. The detector power management unit 352 may receive power from a 48V fuse and control board 340 and distribute the power to the other components of the detector system 348. As described above with respect to FIGS. 1 and 2 , the detector array 108 may detect x-rays attenuated by an object, such as the subject 112. The detector array 108 may be cooled by the one or more fans 350 and the heat exchanger 354. The one or more fans 350 and the heat exchanger 354 may maintain the temperature of the detector array 108 to prevent overheating.

[0043] FIG. 4 is a schematic diagram of a CT system 400 similar to the schematic diagram of CT system 300 shown in FIG. Components included in both CT system 300 and CT system 400 are similarly numbered, and the component descriptions provided above with respect to CT system 300 equally apply to CT system 400. CT system 400 includes an uninterruptible power supply (UPS) 404. UPS 404 can provide backup power to CT system 400 during a power loss / outage (e.g., when power from a main power source, such as an electrical grid, is no longer provided to PDU 302). During an outage, power can be directed from UPS 404 along a first path 406. First path 406 can be represented by a series of dashed arrows originating from UPS 404. Power can be directed from UPS 404 to PDU 302 along first path 406. The PDU 302 can distribute this power to multiple off-gantry devices, such as the reconfiguration hardware 304, blowers and fans 306, SPB 308, operator desktop console 220, and table 114, via a first power distribution path 303. The PDU 302 can also distribute power to the auxiliary inverter 310 via a second power distribution path 309 and to the rectification and filtering board 336 via slip rings 213. A first path 406 can continue from the rectification and filtering board 336 to a 48V fuse and control board 340. The 48V fuse and control board 340 can distribute power to a detector system 348 and other 48V loads 346. Via the first path 406, the detector system 348 and other 48V loads 346 can be powered by the UPS 404. Powering the detector system 348 and other 48V loads 346 via a UPS during a power outage prevents disruption to the CT procedure plan by allowing data from scans to be collected despite the power outage and reducing the need to repeat scans that occur during the power outage.

[0044] Other devices that may be supplied during a power outage may be powered via second path 408 by energy stored in energy storage circuit 342. The stored energy in energy storage circuit 342 may be used to power tube pump 328 and motor 321. Via second path 408, energy may be distributed from energy storage circuit 342 through pump circuit 344 before being distributed to tube pump 328. As an additional part of second path 408, energy may also be distributed from energy storage circuit 342 to RCB 338, and power may be distributed from RCB 338 to motor 321. When power is supplied to CT system 400 by the mains, power flow to tube pump 328 may occur via first pump circuit 410, which includes 48V fuse and control board 340, rectification and filtering board 336, and electrical connections between 48V fuse and control board 340 and tube pump 328. When the main power source is lost (e.g., due to a power outage), power flow to the tube pump 328 may occur via a second pump system 412 that includes an energy storage circuit 342, a pump circuit 344, and an electrical connection between the pump circuit 344 and the tube pump 328. It should be appreciated that the power paths (e.g., first path 406 and second path 408) are illustrated schematically and are not intended to be separate from the electrical connections between devices shown in Figure 4. For example, the power path from the RCB 338 to the motor 321 occurs via a cable coupling the RCB 338 to the motor 321, not via a separate connection.

[0045] Thus, the UPS 404 and the energy storage circuit 342 may provide power to different portions of the CT system 400. The energy storage circuit 342 may be configured to provide power to the motor 321 and the tube pump 328, while the UPS 404 may be configured to power the detector system 348 and multiple off-gantry devices.

[0046] As seen in Figure 4, the RCB 338, the energy storage circuit 342, and the pump circuit 344 may define a self-contained hot trip protection system 402. In the example shown in Figures 3 and 4, the self-contained hot trip protection system 402 includes components located on-board and as part of the rotating auxiliary power unit 334 (e.g., the RCB 338) and components located off of the rotating auxiliary power unit 334 (e.g., the energy storage circuit 342 and the pump circuit 344). However, the self-contained hot trip protection system 402 may be located in different locations within the CT system without departing from the scope of the present disclosure, as will be discussed in more detail below.

[0047] In some examples (not shown), self-contained hot trip protection system 402 may be included in rotating auxiliary power unit 334. Within rotating auxiliary power unit 334, self-contained hot trip protection system 402 may be coupled to rectification and filtering board 336 and 48V fuse and control board 340. Self-contained hot trip protection system 402 may be electrically coupled to motor 321 by multiple cables extending from RCB 338 to motor 321. Thus, in these examples, energy storage circuit 342 and pump circuit 344 may be included within / as part of rotating auxiliary power unit 334.

[0048] 5 shows a schematic diagram of an example CT system 500 in which a self-contained hot shutdown protection system 402 is located in an alternative location within the CT system 500 compared to the CT system 400. In FIG. 5 , the self-contained hot shutdown protection system 402 is coupled to the rotating auxiliary power unit 334 rather than being included in the rotating auxiliary power unit 334. Additionally, the self-contained hot shutdown protection system 402 may be coupled to the motor 321 by three cables, and may be coupled to the tube pump 328 and the rectification and filtering board 336 within the rotating auxiliary power unit 334 by respective cables or other coupling methods. By moving the components of the self-contained hot shutdown protection system 402 off the rotating auxiliary power unit 334, the self-contained hot shutdown protection system 402 may be located closer to the motor 321 than when the components of the self-contained hot shutdown protection system 402 (specifically, the RCB 338) are located in the rotating auxiliary power unit 334. Locating the self-contained hot shutdown protection system 402 closer to the motor 321 can reduce the amount of cabling used to couple the motor 321 to the RCB 338, thus reducing the amount of electromagnetic shielding required and thereby reducing manufacturing cost and complexity. In one example, the number of cables used to couple the motor 321 to the RCB 338 can be reduced from three cables to two cables.

[0049] Multiple coupling configurations are possible between the energy storage circuit 342, the RCB 338, and the pump circuit 344 within the self-contained hot trip protection system 402. FIG. 6 is a schematic diagram of a motor circuit 600 that includes the self-contained hot trip protection system 402. The self-contained hot trip protection system 402 can include and be coupled to components of the CT system 300, the CT system 400, or the CT system 500. FIG. 6 includes a main power source 602 (e.g., a main power supply) that provides power to the self-contained hot trip protection system 402. The main power source 602 can be the rectification and filtering board 336, which can receive power from the auxiliary inverter 310, which in turn receives power from the PDU 302 (and ultimately the power grid) as described with respect to FIG. 3. A diode 606 may be coupled to one outlet of the main power supply 602 to ensure that current flows in only one direction, from the main power supply 602 to the self-contained hot trip protection system 402 .

[0050] The self-contained hot trip protection system 402 may include an energy storage circuit 342, an RCB 338, a pump circuit 344, and a capacitor string 604. In the motor circuit 600, the energy storage circuit 342 may be connected in a series-parallel configuration to the main power source 602. In some examples of the motor circuit 600, the storage circuit 342 may include electrical isolation. The series-parallel configuration may allow the energy storage circuit 342 to control the distribution of energy through the self-contained hot trip protection system 402. The energy storage circuit 342 may include one or more energy storage technologies, such as batteries, capacitors, or superconductors. The energy storage circuit 342 may be configured in parallel with the capacitor string 604 and the RCB 338. The capacitor string 604 may be able to store energy in the self-contained hot trip protection system 402 and reduce fluctuations in the voltage supplied to the system by the main power source 602. The capacitor string 604 can act as a filtering element during normal operation to limit the amount of electromagnetic interference (EMI) and electromagnetic compatibility (EMC). The capacitor string 604 can also act as a supplemental energy storage element. In some examples, the capacitor string 604 can be configured to have a different time constant for accessing stored energy than the energy storage circuit 342. The capacitor string 604 can act as a buffer to different energy storage technologies within the energy storage circuit 342 and can provide additional energy storage capacity. The RCB 338 can be coupled to the stator 324 of the motor 321 by multiple cables 608. The RCB 338 can supply power from the main power supply 602 or the energy storage circuit 342 to the stator 324 of the motor 321 to rotate the rotating assembly 327. Additionally, energy recovered from the motor 321 can be conducted through the multiple cables 608, and the RCB 338 can distribute the recovered energy to the energy storage circuit 342. The energy storage circuit 342 may be configured in series with the pump circuit 344 and may direct power from the main power supply 602 to the pump circuit 344 or may provide stored energy to the pump circuit 344. The pump circuit 344 may control the operation of the tube pump 328 and direct power to the tube pump 328.

[0051] Alternative circuit configurations for the energy storage circuit 342, the RCB 338, and the pump circuit 344 are shown in FIG. 7. FIG. 7 is a schematic diagram of a motor circuit 700 including a self-contained hot-shutdown protection system 402. The motor circuit 700 may be composed of several components described with respect to FIGS. 3, 4, 5, and 6. In the example shown in FIG. 7, the energy storage circuit 342 may be configured in series with the main power supply 602 and with a parallel configuration of the capacitor string 604 and the RCB 338. The energy storage circuit 342 may be configured in series with the pump circuit 344, as described above with respect to FIG. 6. The motor circuit 700 may be easier to control than the motor circuit 600, but may require larger voltages across the capacitor string 604 and the RCB 338. The larger voltages across the capacitor string 604 and the RCB 338 may increase the design requirements for the capacitor string 604 and the RCB 338.

[0052] Another alternative circuit configuration for the energy storage circuit 342, the RCB 338, and the pump circuit 344 is shown in FIG. 8. FIG. 8 is a schematic diagram of a motor circuit 800 including a self-contained hot trip protection system 402. The motor circuit 800 may be comprised of several components described in further detail with respect to FIGS. 3, 4, 5, and 6. In the example shown in FIG. 8, the energy storage circuit 342 may be configured in parallel with the capacitor bank 604 and the RCB 338. The pump circuit 344 may be coupled in series with the energy storage circuit 342. In the motor circuit 800, the energy storage circuit 342 may include a buck-boost element to couple the energy storage circuit 342, which is at a low voltage, to the voltage required to power the motor.

[0053] Thus, each of the above-described systems provides an energy recovery, storage, and distribution system, including a self-contained hot shutdown protection system, configured to recover energy from the X-ray tube motor and apply the stored energy to the motor and / or coolant pump to ensure the continuing rotation and cooling of the rotating assembly in the event of a power outage from a main power source, such as an electrical grid or generator. The energy recovery, storage, and distribution system can be controlled to operate according to various control strategies. A first control strategy can involve capturing energy from the rotating assembly after each exposure and storing the energy to be reused to increase the speed of the rotating assembly the next time or if a power loss from the main power source occurs. In the event of a power outage, the stored energy can be used to keep the rotating assembly rotating at a low frequency. Energy can be recovered during speed ramp-down, the process by which the rotating assembly speed decreases over a period of time after an X-ray exposure has occurred and power from the main power source is no longer applied to the motor. During speed ramp-down, energy is both recovered and lost as heat. The faster the rotating assembly speed is reduced, the greater the proportion of energy recovered compared to energy lost to heat. The kinetic energy recovered as the rotating assembly slows can be converted to electrical energy and stored. The stored energy can be utilized during the next speed ramp-up of the rotating assembly, a process in which the speed of the rotating assembly increases before an exposure begins. Storing energy during the speed ramp-up and reusing it during the speed ramp-up significantly reduces the additional power demands for accelerating the rotating assembly, resulting in further energy savings and reduced electrical stress on the power chain subsystems and reduced electromagnetic interference generation. A first control strategy is described below with reference to several time domain plots shown in Figures 9 through 11.

[0054] FIG. 9 is a time domain plot 900 illustrating the rotating assembly speed, recovered energy, pump operation, and power flow to the motor in a CT system, such as CT system 300, CT system 400, or CT system 500, when power is supplied to the imaging system from a main power source, which may be the electrical grid or a generator. A first subplot 902 includes a first curve 910 representing the rotating assembly speed (e.g., the speed of rotating assembly 327) over time, a second subplot 904 includes a second curve 912 representing the amount of energy recovered from rotating assembly 327 by the energy recovery, storage, and distribution system, stored in an energy storage circuit (e.g., energy storage circuit 342), and consumed from the energy storage circuit, a third subplot 906 includes a third curve 914 representing the operation of a tube pump (e.g., tube pump 328) over time, and a fourth subplot 908 includes a fourth curve 916 representing the amount of power being directed to a motor (e.g., motor 321), representing the amount of power from the mains power supply (indicated by the dotted portion of fourth curve 916) and the amount of power from the energy storage circuit (indicated by the solid portion of fourth curve 916). A first subplot 902, a second subplot 904, and a fourth subplot 908 each include respective values ​​(e.g., rotating assembly speed, energy, and power flow values) that increase along the y-axis, and a third subplot 906 shows pump operation as a binary value (on / off). Each of the subplots is aligned in time, with time points of interest marked with dashed lines.

[0055] An x-ray exposure occurs before T1, during which the rotating assembly is rotating at high speed (as indicated by the first curve 910), the pump is operational and controlled according to the required cooling schedule by the first pumping system 410 (as indicated by the third curve 914, which shows the pump controlled by the first pumping system 410 via shading), and power flows to the motor from a main power source, such as a connection to an electrical grid, as indicated by the dashed line in the fourth curve 916. The exposure ends at T1. Between T1 and T2 is a speed drop period during which the rotating assembly speed decreases, as indicated by the negatively sloping section of the first curve 910. Energy is recovered from the slowing rotating assembly, as indicated by the positive slope of the second curve 912 between T1 and T2. In some instances, there may be a slight delay (e.g., 1 to 10 seconds) between the start of the rotating assembly speed drop and when energy begins to be recovered from the rotating assembly and stored in the energy storage circuit. During the speed reduction process, no power is supplied to the motor and the recovered energy is supplied to the energy storage circuit, the amount of energy being supplied to the storage circuit being represented by the negative portion of the fourth curve 916 between T1 and T2.

[0056] Between T2 and T3 is a quiescent period during which no x-ray exposure occurs. During this period, the rotating assembly speed is maintained at a constant, low speed, which may be 50 Hz or a similar frequency. The low rotational speed is indicated by the horizontal section of the first curve 910 in the first subplot 902. The amount of stored recovered energy remains constant between T2 and T3, indicated by the horizontal section of the second curve 912 between T2 and T3 (e.g., energy recovery stops after T2). Between T2 and T3, there is a low, constant power flow from the mains to the motor, maintaining the low rotating assembly speed, indicated by the horizontal section of the fourth curve 916 between T2 and T3 in the fourth subplot 908.

[0057] Between T3 and T4, the rotating assembly may ramp up to prepare for the next exposure. The ramp-up process may include accelerating the rotating assembly to reach a commanded / threshold speed for the next exposure. In some examples, the commanded / threshold speed may be 180 Hz for high-speed exposures and 145 Hz for low-speed exposures. The accelerating rotating assembly is seen in the first subplot 902 by the positive slope of the first curve 910 between T3 and T4. The stored energy in the energy storage circuit may be used to facilitate the ramp-up, thereby reducing the amount of stored recovered energy. The reduction in stored recovered energy is seen in the second subplot 904 by the negative slope of the second curve 912 between T3 and T4. The energy supplied to the motor from the energy storage circuit increases at T3, providing enough energy to accelerate the rotating assembly between T3 and T4. The exposure may occur after T4, during which the rotating assembly rotates at a high speed, shown as the horizontal segment of the first curve 910 after T4. The pump operates for the duration of the process required to keep the rotating assembly, LMB, etc. below the threshold temperature, which includes the time before T1 and after T4, as well as the duration between T1 and T4. The third subplot 906 shows steady-state operation of the pump represented by the constant values ​​of the third curve 914, although the speed of the pump may be adjusted and / or the pump may be operated in an intermittent manner to meet cooling demands.

[0058] FIG. 10 is a time domain plot 1000 illustrating the rotating assembly speed, recovered and stored energy, pump operation, and power flow to the motor in a CT system, such as CT system 300, CT system 400, or CT system 500, similar to FIG. 9, but illustrating operation when power is supplied to the imaging system from a main power source, which may be PDU 302, and eventually a power outage is detected during an exposure, causing the rotating assembly to rotate and the pump to operate using energy stored within a self-contained hot trip protection system. A first subplot 1002 includes a first curve 1010 representing the rotating assembly speed over time, a second subplot 1004 includes a second curve 1012 representing the amount of energy stored in the energy storage circuit, a third subplot 1006 includes a third curve 1014 representing the operation of the tube pump over time, and a fourth subplot 1008 includes a fourth curve 1016 representing the amount of power being directed to a motor (e.g., motor 321), representing the amount of power from the main power supply (shown by the dotted portion of the fourth curve 1016) and the amount of power from the energy storage circuit (shown by the solid portion of the fourth curve 1016). First subplot 1002, second subplot 1004, and fourth subplot 1008 each include respective values ​​(e.g., rotating assembly speed, energy, and power flow values) that increase along the y-axis, and third subplot 1006 shows pump operation as a binary value (on / off). Each of the subplots is aligned in time, with time points of interest marked with dashed lines.

[0059] Before T1, an X-ray exposure occurs, so the rotating assembly rotates at high speed, the pump is operational and controlled according to the required cooling schedule by the first pump system 410 (as seen by the third curve 1014, which indicates via shading that the pump is controlled by the first pump system 410), and power to the motor comes from a main power source, such as a connection to an electrical grid. At T1, a power loss occurs, as the power supplied from the main power source is interrupted. After T1, the pump is forced to operate using energy stored within the energy storage circuit 342, as shown by the horizontal portion (e.g., the white blank section) of the third curve 1014. After the power outage, a speed reduction process occurs between T1 and T2, following the same process described with reference to FIG. 9 . Thus, during the period between T1 and T2, the rotating assembly speed decreases, as shown by the negatively sloping section of the first curve 1010. Energy is recovered from the slowing rotating assembly, as shown by the positive slope of the second curve 1012 between T1 and T2. In some instances, there may be a small delay (e.g., 1 to 10 seconds) between the start of the slowdown of the rotating assembly and the time when energy begins to be recovered from the rotating assembly and stored in the energy storage circuit. During the slowdown process, no power is supplied to the motor, and all of the energy recovered while the rotating assembly is rotating is supplied to the energy storage circuit. The amount of energy supplied to the storage circuit is represented by the negative portion of the fourth curve 1016 between T1 and T2.

[0060] After T2, the rotating assembly reaches a threshold speed (e.g., the low speed described above), and the recovered energy is used to maintain the rotating assembly at a low speed, such as 50 Hz. Between T2 and T3, the stored energy decreases linearly, as shown by the sharp drop in the second curve 1012 between T2 and T3 in the second subplot 1004. The stored energy is used to maintain pump operation, as shown by the third curve 1014 between T1 and T4, and to rotate the rotating assembly at a low speed, as shown by the horizontal segment of the first curve 1010 between T2 and T3. The power flow to the motor between T2 and T3 is constant, as shown by the horizontal segment of the fourth curve 1016 between T2 and T3. Power flows from the energy storage circuit to the motor, as seen by the solid-line portion of the fourth curve 1016.

[0061] At T3, the stored energy supply of the energy storage circuit reaches a lower threshold, which may indicate insufficient energy remaining in the energy storage circuit to power both the motor and the tube pump. As such, power supplied to the motor from the energy storage circuit is terminated, and power supplied to the motor decreases to zero at T3. After T3, there is no stored energy available to power the rotation of the rotating assembly, so the rotating assembly coasts to a stop. The coasting of the rotating assembly to a stop is indicated by the nonlinear decay of the rotating assembly speed between T3 and T4 in the first subplot 1002. Power is recovered from the rotating assembly as it slows down, but the recovery rate is low compared to the energy recovery rate between T2 and T3 because the rotating assembly speed is decelerating. At T4, the rotating assembly speed equals zero, indicating the rotating assembly has stopped. The pump stops operating after the rotating assembly stops at T4, as indicated by the pump action represented by the third curve 1014 descending to zero after T4. The pump may be shut down when the rotating assembly speed reaches zero as shown, or it may be shut down when stored recovered energy is depleted or the rotating assembly temperature reaches a threshold temperature. The pump is kept on until the rotating assembly speed drops to zero to provide effective cooling throughout the process and to prevent hot trips by ensuring that the LMB and rotating assembly temperatures drop after a power outage. Keeping the rotating assembly rotating at a slow speed for as long as possible also helps prevent hot trips by keeping the rotating assembly and LMB moving to prevent mechanical contact and possible melting between the sleeve and shaft inside the rotating assembly.

[0062] 11 is a time domain plot 1100 illustrating rotating assembly speed, recovered and stored energy, pump operation, and power flow to the motor for a CT system similar to FIGS. 9 and 10, but operating from power supplied by the mains until a power outage is detected between X-ray exposures. A first subplot 1102 includes a first curve 1110 representing rotating assembly speed over time, a second subplot 1104 includes a second curve 1112 representing the amount of energy stored in the energy storage circuit, a third subplot 1106 includes a third curve 1114 representing the operation of the tube pump over time, and a fourth subplot 1108 includes a fourth curve 1116 representing the amount of power directed to the motor, the amount of power from the mains (shown by the dashed portion of fourth curve 1116) and the amount of power from the energy storage circuit (shown by the solid portion of fourth curve 1116). First subplot 1102, second subplot 1104, and fourth subplot 1108 each include respective values ​​(e.g., rotating assembly speed, energy, and power flow values) that increase along the y-axis, and third subplot 1106 shows pump operation as a binary value (on / off). Each of the subplots is aligned in time, with time points of interest marked with dashed lines.

[0063] Before T1, an x-ray exposure occurs, so the rotating assembly is rotating at high speed, the pump is operational and controlled by the first pump system 410 according to the required cooling schedule (as seen by the third curve 1114, which indicates via shading that the pump is controlled by the first pump system 410), and power flows to the motor from the main power supply. The exposure ends at T1, and power to the motor is terminated. Between T1 and T2 is a speed-down period during which the rotating assembly speed decreases, as indicated by the negatively sloping section of the first curve 1110. Energy is recovered from the slowing rotating assembly, as indicated by the positive slope of the second curve 1112 between T1 and T2. In some instances, there may be a slight delay (e.g., 1 to 10 seconds) between the start of the rotating assembly speed-down and when energy begins to be recovered from the rotating assembly and stored in the energy storage circuit. During the speed-down process, power is not supplied to the motor, and energy recovered from the rotating assembly is supplied to the energy storage circuit. The amount of energy supplied to the storage circuit is represented by the negative portion of the fourth curve 1116 between T1 and T2. The pump is powered by the first pump system 410 until a power loss is detected.

[0064] At T2, the rotating assembly reaches a threshold speed (e.g., the low speed described above). Between T2 and T3 is a quiescent period during which no x-ray exposures occur. During this period, the rotor speed is maintained at a constant low speed, which may be 50 Hz or less, and power is supplied from the main power supply in anticipation of subsequent exposures and / or to cool the rotating assembly. The low rotational speed is indicated by the horizontal section of the first curve 1110 in the first subplot 1102. The amount of stored energy remains constant between T2 and T3, indicated by the horizontal section of the second curve 1112 between T2 and T3. Between T2 and T3, there is a low, constant power flow from the main power supply to the motor to maintain the low rotating assembly speed, indicated by the horizontal section of the fourth curve 1116 between T2 and T3 in the fourth subplot 1108.

[0065] At T3, a power outage occurs and power from the main power supply is no longer available. Between T3 and T4, stored energy in the energy storage circuit is used to power the motor to maintain the rotating assembly speed at a threshold speed (e.g., slow). The use of stored energy to power the motor and pump circuit is shown by the linear decrease between T3 and T4 in the second curve 1112. The constant power flow from the energy storage circuit to the motor is shown as the horizontal section between T3 and T4 in the fourth curve 1116. Additionally, at T3, the pump is forced to operate “on” using stored energy from the energy storage circuit, as shown by the horizontal section (e.g., the white blank section) in the third curve 1114.

[0066] At T4, the stored energy in the energy storage circuit reaches a lower threshold, which may indicate that there is insufficient energy left in the energy storage circuit to power both the motor and the tube pump. As such, power supplied to the motor from the energy storage circuit is terminated, and power supplied to the motor decreases to zero at T4. After T4, there is no stored energy available to rotate the rotating assembly, so the rotating assembly coasts to a stop. The coasting of the rotating assembly to a stop is indicated in first subplot 1102 by the rapid decay in rotating assembly speed between T4 and T5.

[0067] At T5, the rotating assembly speed equals zero, indicating that the rotating assembly has stopped. The pump is deactivated after the rotating assembly has stopped at T5, as indicated by the pump action represented by the third curve 1114 descending to zero at T5. The pump remains operational until the rotating assembly speed drops to zero to provide effective cooling throughout the process and prevent a hot trip by ensuring that the LMB and rotating assembly temperatures drop after a power outage. Keeping the rotating assembly rotating at a slow speed for as long as possible also helps prevent a hot trip by keeping the rotating assembly and LMB moving to prevent mechanical contact and possible melting between the sleeve and shaft inside the rotating assembly. Because the tube pump continues to operate between T4 and T5, the amount of recovered energy stored in the energy storage circuit continues to decrease as the rotor coasts to a stop; however, because energy in the energy storage circuit is only used to power the tube pump between T4 and T5, the recovered energy decreases at a slower rate than it does between T3 and T4. This lower velocity is indicated in the second subplot 1104 by the shallower slope of the second curve 1112 between T4 and T5 relative to between T3 and T4.

[0068] 12(A) and 12(B), which illustrate a method 1200 for controlling the operation of an energy recovery, storage, and distribution system, such as energy storage circuit 342, a coolant pump, such as tube pump 328, and a motor, such as motor 321, according to a first energy recovery scheme to recover energy from the motor after each exposure and consume the stored energy during motor ramp-up or power outages. Method 1200 may be performed according to instructions stored in the memory of one or more controllers or computing devices included as part of and / or operatively coupled to a CT imaging system, such as CT system 300, CT system 400, or CT system 500. At block 1202, method 1200 may include operating an x-ray tube to perform an examination according to one or more scan parameters. The scan parameters may include the number of exposures to be performed during the examination, the length of each exposure, the x-ray tube voltage and / or current for each exposure, and / or other parameters. Operating the X-ray tube to perform an inspection may include rotating the X-ray tube target with a motor to transfer heat resulting from the exposure to the LMB of the rotating assembly, as shown in block 1204. The target rotates so that thermal energy from electrons striking the target during an exposure can be distributed to a focal zone consisting of multiple locations on the target as the target rotates, rather than a single focal point. Additionally, as the rotating assembly rotates, heat may be generated due to friction and as a product of the operation of the motor that rotates the rotating assembly. Operating the X-ray tube to perform an inspection may further include operating a tube pump to cool the rotating assembly and the LMB, as shown in block 1206. The tube pump may be a component of a coolant circuit that flows coolant through the coolant circuit to form thermal contact with the LMB and the rotating assembly and absorb excess heat from the LMB and the rotating assembly. The coolant may be circulated by the pump to a heat exchanger, where the temperature of the coolant is reduced.

[0069] In block 1208, method 1200 may include identifying whether a power loss has occurred. Identifying whether a power loss has occurred may include identifying a loss of power from a main power source, such as through monitoring current through one or both of an inverter or other mechanism. The main power source may stop providing power during a power outage or when, for example, an operator turns off or unplugs the CT system. Monitoring for a power loss may occur throughout the scan, as a power loss may be identified at any time within the scan. If a power loss is detected, method 1200 proceeds to block 1210, which is described in more detail below. Alternatively, if a power loss is not detected, the method proceeds to block 1230, included in FIG. 12(B). A power loss may occur at any point in method 1200, and if a power loss is identified at any point in the scan, method 1200 may include proceeding directly to block 1210 from the point in method 1200 where the power loss was detected.

[0070] At block 1230, the method may include determining whether the rotating assembly is rotating at a high frequency, such as greater than 50 Hz. One or more sensors may be integrated into the motor to measure the speed of rotation of the rotating assembly. If the rotating assembly is not rotating at a high frequency, method 1200 may include determining whether the rotating assembly is commanded to speed up to a higher speed at block 1242. The rotating assembly may have been commanded to speed up in preparation for a subsequent exposure, i.e., to match the rotating assembly speed to the scan parameters initialized at block 1202. If a command to speed up to a higher speed has not been received, method 1200 may continue operating the x-ray tube to perform the examination at block 1202. If a command to speed up to a higher frequency has been received, method 1200 may continue to block 1240, which includes accelerating the rotating assembly to a higher frequency using stored energy. Mechanical energy from the decelerating rotating assembly is stored as electrical energy in an energy storage circuit (e.g., energy storage circuit 342) after each exposure, and the recovered energy can be used to power a motor to speed up the rotational frequency of the rotating assembly to the commanded frequency. Once the commanded frequency is reached, method 1200 can continue to block 1230.

[0071] If the rotating assembly is rotating at a high frequency in block 1230, method 1200 may include evaluating whether the examination is terminated in block 1232. The examination may be terminated based on scan parameters indicating that the examination is complete (e.g., the examination may be performed according to a protocol and may be terminated in response to the protocol being completed) or may be terminated manually by an operator (e.g., the operator may enter an input indicating that the examination is complete). If the examination is not terminated in block 1232, method 1200 may continue to operate the x-ray tube to perform the examination according to the scan parameters in block 1202.

[0072] If the test is terminated at block 1232, method 1200 may include initiating an energy recovery sequence at block 1234. The energy recovery sequence may include terminating power to the rotating assembly (e.g., from a main power source) to slow the rotating assembly, converting the kinetic energy of the rotating assembly into electrical energy by slowing the rotating assembly, and storing the electrical energy in an energy storage circuit for later use. The energy recovery sequence may include monitoring the rotational frequency of the rotating assembly, and at block 1236, method 1200 may include determining whether the rotating assembly is rotating at or below a low frequency threshold. The low frequency threshold may be a frequency at which a hot stop is unlikely to occur if the rotating assembly is stopped, such as a frequency below 50 Hz. If the rotational frequency of the rotating assembly has not reached the low frequency threshold at block 1236, method 1200 may include continuing the energy recovery sequence at block 1234 until the frequency of the rotating assembly reaches the low frequency threshold. If the rotating assembly is rotating at a low frequency or lower in block 1236, method 1200 may include determining whether a request to power down the CT system has been received in block 1237. If a request to power down the CT system has not been received in block 1237, the CT system remains operational, ready for the next scan according to method 1200, and proceeds to block 1202. When the CT system is operational and no examination is occurring, the rotating assembly may be rotated at a low frequency (e.g., 50 Hz) until the next examination begins. If a request to power down the CT system is received in block 1237, method 1200 may proceed to block 1238. In block 1238, the rotating assembly is decelerated and coasted to zero speed. Decelerating and coasting the rotating assembly may include turning off power to the motor to reduce the rotating assembly rotational frequency to zero.The pump may be deactivated when the temperature of the rotating assembly and LMB drops past some threshold, may be deactivated some amount of time after the rotating assembly has coasted, or may be deactivated based on an additional set of criteria. Once the pump is deactivated and the rotating assembly has coasted, the method may end. It should be appreciated that the rotating assembly may be allowed to coast only after it has rotated at a low frequency for a duration that allows the rotating assembly and LMB to cool, and once this duration has elapsed, power to the motor may be terminated. Furthermore, in some examples, a new test may be initiated prior to coasting of the rotating assembly, in which case method 1200 may loop back to block 1202 to again operate the X-ray tube to perform the next test.

[0073] Returning to block 1208 of FIG. 12(A), if a power outage is detected in block 1208, method 1200 may include, in block 1210, starting a pump (e.g., tube pump 328) using energy stored within an energy storage circuit, such as energy storage circuit 342 of FIG. 3, and a portion of the energy in capacitor array 604 of FIGS. 6 and 7. The stored energy may have been accumulated and stored when the rotating assembly slowed down during a previous exposure. The pump pumps cooling fluid to cool the LMB and rotating assembly, thus prioritizing powering the pump to prevent overheating or hot shutdown. In block 1212, the method may include determining whether the rotating assembly is rotating at a high frequency (e.g., greater than 50 Hz, which in some examples may include frequencies as high as 180 Hz or 145 Hz, as described above). If the rotating assembly is rotating at a high frequency, method 1200 may include initiating an energy recovery sequence in block 1214. The energy recovery sequence may be similar to the energy recovery sequence described above and may include converting the kinetic energy of the rotating assembly into electrical energy that can be stored in the energy storage circuit 342 as the rotating assembly slows down. If the rotating assembly is not rotating at a high frequency at block 1212, the method may proceed to block 1216. At block 1216, the method includes using the stored energy in the energy storage circuit to rotate the rotating assembly at a low frequency (e.g., a low frequency such as 50 Hz). Turning on the pump to continue rotating the rotating assembly at a low frequency may prevent a hot shutdown by keeping the liquid metal inside the LMB moving while the LMB is cooled by the coolant circuit, preventing the rotating assembly's bearing sleeve from melting and adhering to the stationary shaft.

[0074] At block 1218, the method may include evaluating whether the rotating assembly temperature is below a threshold temperature. Hot stoppage is more likely when the rotating assembly temperature is high and less likely when the rotating assembly temperature is low. The threshold temperature may correspond to a temperature at which the rotating assembly is low enough that a hot stoppage is unlikely. If the rotating assembly temperature is below the threshold temperature, method 1200 may include, at block 1220, terminating energy to the motor to coast the rotating assembly. Terminating power to the motor may include terminating power to a stator that rotates the rotating assembly to slow the rotating assembly to a stop under the influence of frictional forces. The pump may remain operational while the rotating assembly is coasting to provide active cooling to the rotating assembly and the LMB. At block 1222, the pump may be deactivated once the rotating assembly has stopped, and the method ends.

[0075] However, if, at block 1218, the rotating assembly temperature is greater than the threshold temperature, method 1200 may proceed to block 1224. In block 1224, the method may include evaluating whether the remaining stored energy in the energy storage circuit is less than an energy threshold. The energy threshold may correspond to the amount of energy to operate the pump during the amount of time it takes for the rotating assembly to coast to a stop. If the remaining stored energy is greater than the energy threshold, method 1200 proceeds to block 1216 to continue rotating the rotating assembly at a low frequency using the stored energy in the energy storage circuit. If the remaining stored energy is less than the threshold energy, the method may include, at block 1226, terminating the energy supply to the motor to coast the rotating assembly to a stop. During the time the rotating assembly is coasting, power is still supplied to the pump to provide active cooling during the coast-to-stop process. In block 1228, method 1200 may include supplying power to the pump for as long as possible until the stored energy in the energy storage circuit is depleted. Using the remaining stored energy to run the pump for as long as possible maximizes the system's ability to cool the rotating assembly and prevent hot shutdown. The method 1200 then ends.

[0076] Thus, method 1200 provides for x-ray tube operation according to a first energy recovery scheme, which involves recovering energy from the rotating assembly after each exposure and storing the energy in an energy storage circuit to be reused for the next speed increase of the rotating assembly or in the event of a power loss. In the event of a power outage, the stored energy in the energy storage circuit can be used to keep the rotating assembly rotating at 50 Hz or lower. This approach enables "tube peak power demand reduction" by storing energy during the speed decrease of the rotating assembly and reusing the energy during the speed increase, significantly reducing the additional power demand for acceleration, resulting in additional energy savings and reduced electrical stress and electromagnetic interference / electromagnetic compatibility on the power chain subsystem of the x-ray tube and associated components.

[0077] As previously mentioned, the CT systems described herein can operate according to a second energy recovery scheme, which is illustrated in the plots of Figures 13 and 14 and in the flow charts of Figures 15(A) and 15(B). Figure 13 is a time-domain plot 1300 illustrating the rotating assembly speed, recovered and stored energy, pump operation, and power flow to the motor in a CT system, such as CT system 300, CT system 400, or CT system 500, when power is supplied to the imaging system from a mains power source and energy recovery is performed according to a second energy recovery scheme. The second energy recovery scheme can include recovering energy only during a power loss. A first partial plot 1302 includes a first curve 1310 representing the rotating assembly speed of a rotating assembly (e.g., rotating assembly 327) over time, a second partial plot 1304 includes a second curve 1312 representing the amount of energy recovered from the rotating assembly by the energy recovery, storage, and distribution system and stored in and consumed from the energy recovery, storage, and distribution system (e.g., energy storage circuit 342), a third partial plot 1306 includes a third curve 1314 representing the operation of a tube pump (e.g., tube pump 328) over time, and a fourth partial plot 1308 includes a fourth curve 1316 representing the amount of power directed to the motor, representing the amount of power from the main power supply (shown by the dotted portion of fourth curve 1316) and the amount of power from the energy recovery, storage, and distribution system (shown by the solid portion of fourth curve 1316). First subplot 1302, second subplot 1304, and fourth subplot 1308 each include respective values ​​(e.g., rotating assembly speed, energy, and power flow values) that increase along the y-axis, and third subplot 1306 shows pump operation as a binary value (on / off). Each of the subplots is aligned in time, with time points of interest marked with dashed lines.

[0078] Before T1, the x-ray exposure ends, and the rotating assembly speed decreases over time, as shown in the portion of the first curve 1310 that decreases over time before T1. At T1, the rotating assembly speed may reach a predetermined low frequency, such as 50 Hz. Before T1, power may be supplied to the motor at a decreasing speed, causing the rotating assembly to rotate at a decreasing frequency over time, as shown by the negatively sloping section of the fourth curve 1316. At T1, power to the motor continues at a low level to maintain a low frequency rotation of the rotating assembly, as shown by the flat section of the fourth curve 1316. Because no energy is recovered during the speed decrease process, the second curve 1312 remains zero before and after T1. The tube pump remains "on" throughout the entire process to cool the x-ray tube. The tube pump is controlled according to the cooling schedule required by the first pumping system 410 (as seen by the third curve 1314, which indicates via shading that the pump is controlled by the first pumping system 410), and power flow to the motor comes from a mains power source, such as a connection to an electrical grid, as seen by the dashed line in the fourth curve 1316.

[0079] As previously described, the second energy recovery scheme recovers energy from the rotating assembly only in response to a loss of power from the main power source. If a power loss occurs during an exposure when the rotating assembly is rotating at a high frequency, sufficient energy can be recovered to power the rotating assembly at a low frequency and to cool the rotating assembly and LMB and operate the pump to avoid a hot shutdown. As such, energy recovery and distribution following a power loss during an exposure can be performed in the same manner as the first energy recovery scheme. However, because energy from the rotating assembly is not recovered after each exposure, the energy stored in the energy storage circuit may be zero at any given time. As such, if a power loss occurs after an exposure while the rotating assembly is rotating at a reduced speed or operating at a low frequency, there may be insufficient energy available to continue operating the rotating assembly and pump. As such, the speed of the rotating assembly following an exposure can be reduced significantly more slowly under the second energy recovery scheme than under the first energy recovery scheme, and the rotating assembly is maintained at a rotational speed sufficient to provide energy to avoid a hot shutdown if a power loss occurs. In some examples, the speed of the rotating assembly may be adjusted during the speed ramp following the exposure based on the temperature of the LMB.

[0080] FIG. 14 is a time domain plot 1400 showing the rotating assembly speed, recovered and stored energy, pump operation, and power flow to the motor in the CT system of FIG. 13, but showing power loss after an exposure. The first partial plot 1402 includes a first curve 1410 representing the rotating assembly speed over time, the second partial plot 1404 includes a second curve 1412 representing the amount of energy recovered from the rotating assembly by the energy recovery, storage, and distribution system and stored in and consumed from the energy recovery, storage, and distribution system, the third partial plot 1406 includes a third curve 1414 representing the operation of the tube pump over time, and the fourth partial plot 1408 includes a fourth curve 1416 representing the amount of power directed to the motor, representing the amount of power from the main power supply (shown by the dotted portion of the fourth curve 1416) and the amount of power from the energy recovery, storage, and distribution system (shown by the solid portion of the fourth curve 1416). First subplot 1402, second subplot 1404, and fourth subplot 1408 each include respective values ​​(e.g., rotating assembly speed, energy, and power flow values) that increase along the y-axis, and third subplot 1406 shows pump operation as a binary value (on / off). Each of the subplots is aligned in time, with time points of interest marked with dashed lines.

[0081] Before T1, the rotating assembly slows down following the end of the X-ray exposure. The rotating assembly rotates at a decreasing frequency, as represented by the negative slope of the section of the first curve 1410 before T1. Energy is not being recovered, as indicated by the horizontal section of the second curve 1412 before T1, and the amount of power flow to the motor is reduced to rotate the rotating assembly at a decreasing speed, as indicated by the negative slope of the section of the fourth curve 1416 before T1. The tube pump begins operating, as indicated by the constant shading in the third curve 1414 before T1, thereby cooling the X-ray tube. The tube pump is controlled according to a required cooling schedule by the first pumping system 410 (as seen by the third curve 1414 indicating via shading that the pump is controlled by the first pumping system 410), and power flow to the motor is from a mains power source, such as a connection to an electrical grid, as seen by the dashed line in the fourth curve 1416.

[0082] At T1, a power outage occurs and the energy recovery process begins. The rotating assembly slows down to a low frequency, such as 50 Hz, as indicated by the negative slope of the section between T1 and T2 of the first curve 1410. The mechanical energy recovered from the slowing rotating assembly is converted to electrical energy and stored in the energy storage circuit, as indicated by the positive slope of the section between T2 and T1 of the second curve 1412. At T1 (or as soon as sufficient energy is available in the energy storage circuit), the pump power source is changed and pumping operation is now powered by the energy storage circuit. The change in power source is indicated by the portion of the third curve 1414 after T1 that does not contain a solid pattern. Pumping operation remains constant, and in at least some instances, no pumping action is lost during the power outage. The recovered energy is indicated by the negative portion of the fourth curve 1416 between T1 and T2.

[0083] After T2, the rotating assembly rotates at a lower frequency and the pump operates on the energy stored in the energy storage circuit between T1 and T2. During this period, the amount of energy in the energy storage circuit decreases, as shown in second subplot 1404 by the linearly decreasing section between T2 and T3 of second curve 1412. The amount of power used to rotate the rotating assembly is shown as the horizontal section between T2 and T4 of fourth curve 1416.

[0084] At T3, the energy within the energy storage circuit reaches a lower threshold, which may indicate that there is insufficient energy remaining in the energy storage circuit to power both the motor and the tube pump. As such, power supplied to the motor from the energy storage circuit is terminated, and the power supplied to the motor decreases to zero at T3. At T3, power is no longer being supplied to rotate the rotating assembly, and the rotating assembly speed drops, as indicated by the decreasing section of first curve 1410 between T3 and T4 in first subplot 1402. Because the energy storage circuit is only supplying power to the tube pump between T3 and T4, the rate at which energy in the energy storage circuit is consumed is lower between T3 and T4 than between T2 and T3. At T4, the rotating assembly speed reaches zero. The pump remains operational until the rotating assembly speed reaches zero.

[0085] 15(A) and 15(B), which illustrate a method 1500 for controlling the operation of an energy recovery, storage, and distribution system, such as energy storage circuit 342, a cooling pump, such as tube pump 328, and a motor, such as motor 321, to recover energy from the motor following a power outage. Method 1500 may be performed according to instructions stored in the memory of one or more controllers or computing devices included as part of and / or operatively coupled to a CT imaging system, such as CT system 300, CT system 400, or CT system 500. At block 1502, method 1500 may include operating an x-ray tube to perform an examination according to scan parameters. The scan parameters may include the number of exposures to be performed during the examination, the length of each exposure, the x-ray tube voltage and / or current for each exposure, and / or other parameters. Operating the X-ray tube to perform an inspection may include rotating the X-ray tube target with the rotating assembly to transfer heat resulting from the exposure to the LMB of the rotating assembly, as shown in block 1504. The target rotates so that thermal energy from electrons striking the target during an exposure can be distributed across a focal zone consisting of multiple locations on the target as the target rotates, rather than a single focal point. Additionally, as the rotating assembly rotates, heat may be generated due to friction and as a product of operating the motor that rotates the rotating assembly. Operating the X-ray tube to perform an inspection may further include operating a pump to cool the rotating assembly and the LMB, as shown in block 1506. The pump may be a component of a coolant circuit that flows coolant through the coolant circuit to form thermal contact with the LMB and the rotating assembly and absorb excess heat from the LMB and the rotating assembly. The coolant may be circulated by the pump to a heat exchanger, where the temperature of the coolant is reduced.

[0086] At block 1508, method 1500 may include identifying whether a power loss has occurred. Identifying whether a power loss has occurred may include identifying a loss of power from a main power source, such as through monitoring current through one or both of an inverter or other mechanism. The main power source may stop providing power during a power outage or when, for example, an operator turns off the CT system. Monitoring for a power loss may occur throughout the scan, as a power loss may be identified at any time within the scan. If a power loss is detected, method 1500 proceeds to block 1509, which is described in more detail below. If a power loss is not detected, the method proceeds to block 1528, included in FIG. 15(B). A power loss may occur at any point in method 1500, and if a power loss is identified at any point in the scan, method 1500 may include proceeding directly to block 1509 from the point in method 1500 where the power loss was detected.

[0087] At block 1528, method 1500 may include determining whether an exposure is requested. The exposure request may be entered by a healthcare provider or may originate from a controller integrated into the CT system. If an exposure is not requested, method 1500 continues to block 1546; if an exposure is requested, method 1500 continues to block 1530, which is described in more detail below. At block 1546, method 1500 may include determining whether the rotating assembly is rotating above a low frequency threshold. The low frequency threshold may be 50 Hz, as described above. If the rotating assembly is not rotating above the low frequency at block 1546, method 1500 continues to block 1542. If the rotating assembly is rotating above the low frequency at block 1546, the temperature and energy of the rotating assembly may be evaluated at block 1548. The evaluation may be accomplished by temperature and frequency sensors coupled to the rotating assembly. At block 1550, the energy of the rotating assembly is evaluated to determine whether sufficient energy could have been recovered to cool the rotating assembly if a power outage had occurred. If sufficient energy is present at block 1550, method 1500 may include proceeding to 1542, which is described in more detail below. If insufficient energy is present at block 1550, the method may include accelerating the rotating assembly at block 1552. Accelerating the rotating assembly may include issuing a command to a power source coupled to the motor, such as RCB 338. The rotating assembly may be accelerated to a new set frequency, which may be calculated based on the temperature of the rotating assembly. From block 1552, method 1500 may proceed to block 1548 to determine whether the rotating assembly has accelerated to the appropriate speed.

[0088] Returning to block 1528, if an exposure request is detected, method 1500 proceeds to block 1530, which may include predicting the temperature of the target after the exposure occurs. The target may be an anode in an x-ray tube and may be coupled to or included as part of the rotating assembly. When an x-ray exposure occurs, electrons strike the target, generating x-rays and heat. The temperature change of the target may be predicted based on several factors, including the duration of the x-ray exposure, the intensity of the x-ray beam striking the target (which may be based on the x-ray tube current), the efficiency of a coolant circuit coupled to the rotating assembly, and the current temperature of the rotating assembly and target.

[0089] At block 1532, the method may include calculating an amount of energy designated to rotate the rotating assembly at a reduced frequency if power is lost. This calculation may be based on the amount of time it takes to cool the rotating assembly from its current temperature to a temperature where the risk of a hot trip is low and the amount of energy to power the tube pump while the rotating assembly is cooling. At block 1534, the method 1500 may include determining a rotating assembly speed required to recover the amount of energy calculated at block 1532 if a power loss occurs. Determining the rotating assembly speed may include a calculation that accounts for energy losses between the rotating assembly and the energy storage circuit and the amount of kinetic energy the rotating assembly possesses, which depends on the rotational speed of the rotating assembly.

[0090] At block 1536, the method may include determining whether the determined rotating assembly speed is greater than a maximum rotating assembly speed. The maximum rotating assembly speed may be based on motor limitations and target limitations. If the determined rotating assembly speed is less than or equal to the maximum rotating assembly speed, method 1500 may include, at block 1554, rotating the rotating assembly at the determined speed. Method 1500 continues from block 1554 to block 1540. If, at block 1536, the determined rotating assembly speed is greater than the maximum rotating assembly speed, method 1500 may include, at block 1538, rotating the rotating assembly at the maximum rotating assembly speed before proceeding to block 1540.

[0091] At block 1540, the method may include performing an exposure. The exposure may include an x-ray generator powering an x-ray tube to accelerate a beam of electrons toward a rotating target. The electrons may generate x-rays as they strike the target, and the x-rays may pass through the subject and be detected by a detector to image the subject. In a CT system such as the CT system 400 described with reference to FIG. 4, the x-ray generator and tube may be integrated into a rotating gantry, allowing the x-ray generator, x-ray tube, x-ray detector, and associated power electronics to rotate during the exposure. The exposure may additionally include powering a motor to rotate the rotating assembly at a speed such that, upon completion of the exposure, sufficient energy can be recovered to rotate the rotating assembly at a low frequency to operate the pump in the event of a power loss. As shown in FIG. 13 , following completion of an exposure, rather than terminating power to the motor to slow the rotating assembly to a lower frequency, the rotating assembly can be gradually slowed down, for example, at a rate based on the temperature of the LMB, so that sufficient energy can be recovered to cool the LMB via rotating the rotating assembly and running the pump in the event of a power loss. The process of slowing down the rotating assembly speed can be performed similarly to the processes described above with respect to blocks 1548, 1550, and 1552 of method 1500 described above. In block 1542, method 1500 can include determining whether the test is terminated (e.g., completed). The test can be terminated / completed if all exposures of the subject have been performed. If the test is not terminated at block 1542, method 1500 can continue to block 1502. The method can continue from block 1502 in the manner described above. If the examination is concluded at block 1542, method 1500 may include determining whether a request to power down the CT system has been received at block 1543. If a request to power down the CT system has not been received at block 1543, the CT system remains operational and ready for the next scan according to method 1500, proceeding to block 1502.If a request to power down the CT system is received at block 1543, method 1500 may proceed to block 1544. At block 1544, method 1500 may include rotating the rotating assembly and running the pump until instructed, and then coasting the rotating assembly and shutting down the pump at block 1544. The rotating assembly and pump may be instructed to stop if the rotating assembly temperature reaches a low temperature threshold and coasting the rotating assembly at the current temperature is unlikely to result in a hot stall. Coasting the rotating assembly may include gradually decreasing the speed of the rotating assembly to a stop, which may be achieved by no longer supplying power to the motor. At the conclusion of the test, if a new test is to be started, method 1500 may loop back to block 1502 to start the next test, although it should be appreciated that in some instances this may occur without bringing the rotating assembly to a complete stop.

[0092] Returning to block 1508 of FIG. 15(A), if a power loss is detected in block 1508, method 1500 may include, in block 1509, commencing operation of the tube pump using recovered / stored energy, which may be stored in an energy storage circuit, such as energy storage circuit 342 from FIG. 3. In block 1510, method 1500 includes initiating energy recovery from the rotating assembly. If the power loss occurs during an exposure or during a speed reduction of the rotating assembly following an exposure, energy from the rotating assembly may be recovered while the rotating assembly rotates down to a low frequency threshold. In block 1512, the method may include powering a motor using energy stored in the stored energy circuit to rotate the rotating assembly at a low frequency, such as 50 Hz. In block 1514, the method may include determining whether the rotating assembly temperature is below a threshold temperature. The threshold temperature may be a temperature below which there is a low risk of a hot trip. If the rotating assembly temperature is below the threshold temperature, method 1500 may include, at block 1516, terminating energy to the motor to coast the rotating assembly. Terminating power to the motor may include terminating power to a stator that rotates the rotating assembly to slow the rotating assembly to a stop under the influence of frictional forces. The pump may remain operational while the rotating assembly is coasting to provide active cooling to the rotating assembly and LMB. At block 1518, the pump may be deactivated once the rotating assembly has come to a stop, and the method ends.

[0093] If the rotating assembly temperature is greater than or equal to the threshold temperature at block 1514, method 1500 may include, at block 1520, determining whether the remaining stored energy in the energy storage circuit is less than an energy threshold. The energy threshold may correspond to the amount of energy to operate the pump during the amount of time it takes to coast the rotating assembly to a stop. If the remaining stored energy is greater than the energy threshold, method 1500 proceeds to block 1522 to continue rotating the rotating assembly at a low frequency using the stored energy. If the remaining stored energy is less than or equal to the energy threshold, the method may include, at block 1522, terminating the energy supply to the motor and coasting the rotating assembly to a stop. During the time the rotating assembly is coasting, power is still supplied to the pump to provide active cooling during the coasting process. At block 1524, method 1500 may include powering the pump for as long as possible until the stored energy is depleted. Using the remaining stored energy to run the pump for as long as possible maximizes the system's ability to cool the rotating assembly and prevent hot shutdowns.

[0094] The technical effect of the disclosed self-contained hot trip protection system is the prevention of hot trips in the event of a power outage by recovering energy from the rotating assembly as it slows down and storing this energy for use in powering the motor and tubing pump. The motor can be powered to keep the rotating assembly rotating at a slow speed, and the tubing pump can be powered to cool the rotating assembly. Rotating the rotating assembly at a slow speed and using the stored recovered energy to cool the rotating assembly prevents the rotating assembly from suddenly stopping at a high temperature, which can cause the sleeve inside the rotating assembly to melt and adhere to the shaft, also known as a hot trip. Additionally, recovering energy from a rotating rotating assembly facilitates energy conservation and reduces the amount of power required from an external source to operate the motor.

[0095] Although a computed tomography (CT) system is described as an example, it is understood that the present techniques may also be useful when applied to other x-ray imaging modalities, such as x-ray angiography systems, x-ray tomosynthesis systems, x-ray mammography systems, x-ray fluoroscopy systems, x-ray invasive systems, x-ray C-arm systems, etc. This discussion of the CT imaging modality is provided only as an example of one suitable imaging modality.

[0096] The present disclosure also provides support for a method for an X-ray tube in an imaging system, the method including the steps of: supplying energy from a mains power supply to the X-ray tube to rotate a target of the X-ray tube during a scan of a subject by the imaging system; selectively recovering energy from the X-ray tube and storing the recovered energy in an energy storage circuit of the imaging system; and detecting a loss of the mains power supply and, in response, supplying energy from the energy storage circuit to the X-ray tube to rotate the target at a threshold speed. In a first example of the method, the step of supplying energy from the mains power supply to the X-ray tube to rotate a target of the X-ray tube includes supplying energy from the mains power supply to a motor coupled to the target. In a second example of the method, which optionally includes the first example, the step of selectively recovering energy from the X-ray tube includes recovering energy from the motor in response to detecting a loss of the mains power supply. In a third example of the method, optionally including one or both of the first and second examples, the step of selectively recovering energy from the X-ray tube includes recovering energy from the motor during a speed ramp-down of the motor following completion of a first exposure by the X-ray tube. In a fourth example of the method, optionally including one or more or each of the first through third examples, the first exposure includes supplying energy from the mains power supply to the X-ray tube to rotate the target at an operating speed above a threshold speed, and during the speed ramp-down, no energy from the mains power supply is supplied to the motor. In a fifth example of the method, optionally including one or more or each of the first through fourth examples, the method further includes receiving a request to initiate a second exposure by the X-ray tube and, in response, supplying energy from an energy storage circuit to the motor to rotate the target to the operating speed. In a sixth example of the method, optionally including one or more or each of the first through fifth examples, the method further includes, in response to detecting a loss of mains power, supplying energy from the energy storage circuit to a pump configured to supply coolant to the X-ray tube.In a seventh example of the method, optionally including one or more or each of the first through sixth examples, the method further includes supplying energy from the energy storage circuit to the x-ray tube to rotate the target at a threshold speed until the temperature of the x-ray tube reaches a threshold temperature or until the amount of energy stored in the energy storage circuit reaches a threshold energy, and then terminating the supply of energy to the x-ray tube. In an eighth example of the method, optionally including one or more or each of the first through seventh examples, the method further includes supplying energy from the energy storage circuit to a pump until the target stops rotating, and then terminating the supply of energy to the pump.

[0097] The present disclosure also provides support for a computed tomography (CT) imaging system, the CT imaging system including an X-ray tube including a rotating assembly, the rotating assembly including a target and a motor rotor, an energy storage circuit coupled to the motor, a memory storing instructions, and one or more processors configured to execute the instructions, the one or more processors being configured to: in response to a loss of main power to the motor, convert rotational energy of the rotating assembly into electrical energy as the rotating assembly rotates following the loss of main power, the electrical energy being stored in the energy storage circuit; and supply the electrical energy stored in the energy storage circuit to the motor to continue rotating the rotating assembly at a threshold speed for a duration. In a first example of the system, the system further includes a coolant circuit including a pump configured to supply coolant to the motor, the one or more processors being configured to execute the instructions to supply electrical energy from the energy storage circuit to the pump in response to a loss of main power. In a second example of the system, optionally including the first example, the one or more processors are configured to execute instructions to terminate the supply of electrical energy from the energy storage circuit to the motor after the duration, continue supplying electrical energy from the energy storage circuit to the pump until the rotating assembly stops rotating, and then terminate the supply of electrical energy to the pump. In a third example of the system, optionally including one or both of the first and second examples, the duration is based on a temperature of the motor and / or an amount of energy stored in the energy storage circuit. In a fourth example of the system, optionally including one or more or each of the first through third examples, the system further includes a power distribution unit configured to supply electrical energy from a main power source to the motor via a power path that bypasses the energy storage circuit.In a fifth example of a system optionally including one or more or each of the first through fourth examples, the system further includes an uninterruptible power supply coupled to the power distribution unit and configured to supply electrical energy to a detector system of the CT imaging system and / or one or more extra-gantry devices of the CT imaging system in response to a loss of mains power.

[0098] The present disclosure also provides support for a computed tomography (CT) imaging system including an x-ray tube including a target, a motor including a rotor and a liquid metal bearing (LMB) coupled to the target, wherein the target, the rotor, and a sleeve of the LMB form a rotating assembly, an energy storage circuit coupled to the motor, a coolant circuit coupled to the motor and including a pump, a memory storing instructions, and one or more processors configured to execute the instructions, wherein the one or more processors control the rotating assembly at an operating speed during a first exposure. and to supply electrical energy from the main power supply to the motor to rotate the rotating assembly at a speed of about 1000 W and to supply electrical energy from the main power supply to the pump to cool the motor; in response to termination of the first exposure, converting rotational energy of the rotating assembly into electrical energy as the rotating assembly continues to rotate following termination of the first exposure, the electrical energy being stored in an energy storage circuit; and in response to initiation of the second exposure, supplying electrical energy stored in the energy storage circuit to the motor to increase the rotational speed of the rotating assembly to an operating speed. In a first example of the system, the one or more processors are further configured to execute instructions: in response to a loss of primary power to the motor during the second exposure, to supply electrical energy from an energy storage circuit to the pump; instructions to convert rotational energy of the rotating assembly into electrical energy as the rotating assembly continues to rotate following the loss of primary power, the electrical energy being stored in the energy storage circuit; and instructions to supply electrical energy stored in the energy storage circuit to the motor once the speed of the rotating assembly reaches the lower threshold speed to maintain the speed of the rotating assembly at the lower threshold speed. In a second example of the system that optionally includes the first example, the one or more processors are further configured to execute instructions to supply electrical energy from the primary power source to the motor to rotate the rotating assembly at the lower threshold speed during a period between the first exposure and the second exposure.In a third example of a system optionally including one or both of the first and second examples, the one or more processors are further configured to execute instructions to terminate the supply of electrical energy from the energy storage circuit to the motor after a duration, continue supplying electrical energy from the energy storage circuit to the pump until the rotating assembly stops rotating, and then terminate the supply of electrical energy to the pump. In a fourth example of a system optionally including one or more or each of the first through third examples, the duration is based on a temperature of the motor and / or an amount of energy stored in the energy storage circuit.

[0099] When describing elements of various embodiments of the present disclosure, terms such as "the," "said," "the," and the like are intended to mean that there are one or more of the elements in question. Terms such as "first," "second," and the like do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Furthermore, the terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements. When terms such as "connected" and "coupled" are used herein, they refer to one object (e.g., a material, element, structure, member, etc.) being connected or coupled to another object, whether the object is directly connected or coupled to the other object or whether there are one or more intervening objects between the two. In addition, references to "one embodiment" or "an embodiment" in this disclosure should not be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.

[0100] In addition to any modifications set forth above, many other variations and alternative arrangements can be devised by those skilled in the art without departing from the spirit and scope of the present description, and the following claims are intended to cover such modifications and arrangements. Thus, while the information has been described above with specificity and detail in connection with what is presently considered to be the most practical and preferred aspects, it will be apparent to those skilled in the art that many modifications, including but not limited to form, function, modes of operation, and usage, can be made without departing from the principles and concepts described herein. Also, as used herein, the examples and embodiments are in all respects illustrative only and should not be construed as limiting in any manner. [Explanation of symbols]

[0101] 100 Computed Tomography (CT) System 102 Gantry 104 X-ray source 106 X-ray radiation beam 108 detector array 112 Subject 114 Tables 200 Imaging System 202 detector element 204 Subject 206 Center of rotation 208 Control Mechanism 213 Slip Ring 214 Data Acquisition System (DAS) 220 Operator Console 232 Display device 300 CT System 302 Power Distribution Unit (PDU) 303 First Power Distribution Path 304 Reconfigurable Hardware 306 Blowers and fans 308 Stationary power supply board (SPB) 309 Second Power Distribution Path 310 Auxiliary Inverter 311 First Branch 312 X-ray inverter 313 Second Branch 314 X-ray generator 316 X-ray tube 318 Rotor 319 Target 320 Liquid Metal Bearing (LMB) 321 Motor 322 Shaft 324 Stator 325 sleeve 326 Cooling Channel 327 Rotating Assembly 328 Pipe Pump 330 heat exchanger 332 Coolant circuit 334 Rotating Auxiliary Power Unit 336 Rectification and Filtering Board 338 Rotation Control Board (RCB) 340 48V fuse and control board 342 Energy Storage Circuit 344 Pump Circuit 346 48V load 348 Detector System 350 Fan 352 Detector Power Management Unit 354 Heat exchanger 400 CT System 402 Self-contained hot shutdown protection system 404 Uninterruptible power supply (UPS) 406 First Route (UPS) 408 Second Path (Energy Storage Circuit) 410 First pump system (main power) 412 Second pump system (in case of loss of main power) 500 CT System 600 Motor Circuit 602 Main power supply 604 capacitor array 606 Diode 608 Cable 700, 800 motor circuit 900, 1000, 1100, 1300, 1400 Time domain plot 902, 1002, 1102, 1302, 1402 First subplot 904, 1004, 1104, 1304, 1404 Second subplot 906, 1006, 1106, 1306, 1406 Third subplot 908, 1008, 1108, 1308, 1408 Fourth subplot 910, 1010, 1110, 1310, 1410 First curve 912, 1012, 1112, 1312, 1412 Second curve 914, 1014, 1114, 1314, 1414 Third Curve 916, 1016, 1116, 1316, 1416 Fourth Curve 1200, 1500 Energy recovery, storage, and distribution systems, cooling pumps, and methods for controlling motor operation

Claims

1. 1. A method for an x-ray tube of an imaging system, comprising: supplying energy from a mains power supply to the x-ray tube to rotate a target of the x-ray tube while the imaging system scans the subject; selectively recovering energy from the x-ray tube and storing the recovered energy in an energy storage circuit of the imaging system; detecting a loss of the main power supply and, in response, supplying energy from the energy storage circuit to the x-ray tube to rotate the target at a threshold speed; A method comprising:

2. 2. The method of claim 1, wherein the step of supplying energy from the main power supply to the X-ray tube to rotate the target of the X-ray tube comprises supplying energy from the main power supply to a motor coupled to the target.

3. 3. The method of claim 2, wherein selectively recovering energy from the x-ray tube comprises recovering energy from the motor in response to detecting the loss of the main power supply.

4. 3. The method of claim 2, wherein selectively recovering energy from the x-ray tube comprises recovering energy from the motor during a slowdown of the motor following the termination of a first exposure by the x-ray tube.

5. 5. The method of claim 4, wherein the first exposure includes supplying energy from the mains power supply to the x-ray tube to rotate the target at an operating speed greater than the threshold speed, and wherein the energy from the mains power supply is not supplied to the motor during the speed reduction.

6. 6. The method of claim 5, further comprising receiving a request to initiate a second exposure by the x-ray tube and, in response, supplying energy from the energy storage circuit to the motor to rotate the target to the operating speed.

7. 10. The method of claim 1, further comprising the step of, in response to detecting the loss of the main power source, supplying energy from the energy storage circuit to a pump configured to supply coolant to the x-ray tube.

8. 8. The method of claim 7, further comprising the steps of: supplying energy from the energy storage circuit to the X-ray tube to rotate the target at the threshold speed until a temperature of the X-ray tube reaches a threshold temperature or until an amount of energy stored in the energy storage circuit reaches a threshold energy; and then terminating the supply of the energy to the X-ray tube.

9. 9. The method of claim 8, further comprising the steps of supplying energy from the energy storage circuit to the pump until the target stops rotating, and then terminating the supply of the energy to the pump.

10. an x-ray tube including a rotating assembly, the rotating assembly including a target and a rotor of a motor; an energy storage circuit coupled to the motor; a memory storing instructions; one or more processors configured to execute the instructions; 1. A computed tomography (CT) imaging system comprising: instructions, in response to a loss of primary power to the motor, to convert rotational energy of the rotating assembly into electrical energy as the rotating assembly rotates following the loss of primary power, the electrical energy being stored in the energy storage circuit; commands to supply the electrical energy stored in the energy storage circuit to the motor to continue rotating the rotating assembly at a threshold speed for a duration; 1. A computed tomography (CT) imaging system configured to perform:

11. 11. The CT imaging system of claim 10, further comprising a coolant circuit including a pump configured to supply coolant to the motor, wherein the one or more processors are configured to execute instructions to supply the electrical energy from the energy storage circuit to the pump in response to the loss of the main power source.

12. 12. The CT imaging system of claim 11, wherein the one or more processors are configured to execute instructions to terminate the supply of the electrical energy from the energy storage circuit to the motor after the duration, continue supplying the electrical energy from the energy storage circuit to the pump until the rotating assembly stops rotating, and then terminate the supply of the electrical energy to the pump.

13. 13. The CT imaging system of claim 12, wherein the duration is based on a temperature of the motor and / or an amount of energy stored in the energy storage circuit.

14. 11. The CT imaging system of claim 10, further comprising a power distribution unit configured to supply electrical energy from the main power supply to the motor via a power path that bypasses the energy storage circuit.

15. 15. The CT imaging system of claim 14, further comprising an uninterruptible power supply coupled to the power distribution unit and configured to supply electrical energy to a detector system of the CT imaging system and / or one or more extra-gantry devices of the CT imaging system in response to the loss of the main power source.

16. an x-ray tube including a target; a motor including a rotor and a liquid metal bearing (LMB) coupled to the target, the target, the rotor, and the sleeve of the LMB forming a rotating assembly; an energy storage circuit coupled to the motor; a coolant circuit coupled to the motor and including a pump; a memory storing instructions; one or more processors configured to execute the instructions; 1. A computed tomography (CT) imaging system comprising: instructions to supply electrical energy from a main power supply to the motor to rotate the rotating assembly at an operating speed during a first exposure and to supply electrical energy from the main power supply to the pump to cool the motor; instructions, in response to a termination of the first exposure, to convert rotational energy of the rotating assembly into electrical energy as the rotating assembly continues to rotate following the termination of the first exposure, the electrical energy being stored in the energy storage circuit; and in response to initiation of a second exposure, supplying the electrical energy stored in the energy storage circuit to the motor to increase the rotational speed of the rotating assembly to the operating speed; 1. A computed tomography (CT) imaging system configured to perform:

17. The one or more processors further comprise: in response to a loss of main power to the motor during the second exposure: instructions to supply electrical energy from the energy storage circuit to the pump; instructions to convert rotational energy of the rotating assembly into electrical energy as the rotating assembly continues to rotate following the loss of the main power source, the electrical energy being stored in the energy storage circuit; and once the speed of the rotating assembly reaches a lower threshold speed, commands to supply the electrical energy stored in the energy storage circuit to the motor so as to maintain the speed of the rotating assembly at the lower threshold speed; 17. The CT imaging system of claim 16, configured to perform:

18. 18. The CT imaging system of claim 17, wherein the one or more processors are further configured to execute instructions to supply electrical energy from the main power supply to the motor to rotate the rotating assembly at the lower threshold speed during a period between the first exposure and the second exposure.

19. 20. The CT imaging system of claim 18, wherein the one or more processors are further configured to execute instructions to terminate the supply of the electrical energy from the energy storage circuit to the motor after a duration to continue supplying the electrical energy from the energy storage circuit to the pump until the rotating assembly stops rotating, and then to terminate the supply of the electrical energy to the pump.

20. 20. The CT imaging system of claim 19, wherein the duration is based on a temperature of the motor and / or an amount of energy stored in the energy storage circuit.

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