System and method for X-ray tube

Abstract

The invention relates to a system and method for an X-ray tube. Methods and systems are provided for preventing thermal landing of a motor (321) of an X-ray imaging system (300) in the event of power loss. In one example, a method for an X-ray tube of an imaging system (300) includes supplying energy from a primary power source (602) to the X-ray tube (316) during scanning of a subject (204) using the imaging system (300) in order to rotate a target (319) of the X-ray tube (316); selectively recovering energy from the X-ray tube (316) and storing the recovered energy in a tank circuit (342) of the imaging system (300); and detecting a loss of the main power source (602) and, in response, supplying energy from the tank circuit (342) to the X-ray tube (316) in order to rotate the target (319) at a threshold speed.

Description

TECHNICAL FIELD

[0001] Embodiments of the subject matter disclosed herein relate to imaging systems and methods, and more particularly, to control of a rotatable component of an x-ray tube in a computed tomography (CT) imaging system. BACKGROUND

[0002] In a computed tomography (CT) imaging system, an electron beam generated by a cathode is directed at a target within an x-ray source or x-ray tube. A fan or cone shaped x-ray beam generated by the electrons colliding with the target is directed at a subject, such as a patient. After being attenuated by the object, the x-rays impinge on an x-ray detector array, generating an image. In some examples, the target can be configured to rotate such that the electron beam periodically, rather than continuously, bombards a focal spot of the target, dispersing the generated heat energy. In some examples, the target can be an anode. SUMMARY

[0003] In one example, a method for an x-ray tube of an imaging system can include supplying energy from a main power source to the x-ray tube to rotate a target of the x-ray tube during a scan of a subject using 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 main power source and, in response, supplying energy from the energy storage circuit to the x-ray tube to rotate the target at a threshold speed.

[0004] The above advantages of the present specification, and other advantages and features, will be apparent from the following detailed description, when read in conjunction with the appended drawings. It should be understood that the above summary of the present specification is intended to be simply a summary of some of the concepts of the present specification. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined solely by the claims that follow this detailed description. Furthermore, the claimed subject matter is not limited to resolving any disadvantages mentioned in the background or any part of this disclosure. For a better understanding of various aspects of the present disclosure, refer to the detailed description and to the accompanying drawings in which: BRIEF DESCRIPTION OF DRAWINGS

[0005] Various aspects of the present disclosure can be better understood by reading the following detailed description in conjunction with the accompanying drawings, in which:

[0006] Figure 1 A pictorial view of a computed tomography (CT) imaging system is shown in accordance with one or more embodiments of the present disclosure.

[0007] Figure 2 A schematic block diagram of an exemplary CT imaging system is shown in accordance with one or more embodiments of the present disclosure.

[0008] Figure 3A schematic diagram of an exemplary CT imaging system is shown having an uninterruptible power supply and an energy storage recovery system coupled to a motor in a first exemplary arrangement.

[0009] Figure 4 A schematic diagram of an exemplary CT imaging system is shown having an uninterruptible power supply and an energy storage recovery system coupled to a motor in a first exemplary arrangement.

[0010] Figure 5 A schematic diagram of an exemplary CT imaging system is shown having an uninterruptible power supply and an energy storage recovery system coupled to a motor in a second exemplary arrangement.

[0011] Figure 6 A schematic diagram of a first exemplary hardware arrangement of a self-contained thermal landing protection system including an energy storage recovery system.

[0012] Figure 7 A schematic diagram of a second exemplary hardware arrangement of a self-contained thermal landing protection system.

[0013] Figure 8 A schematic diagram of a third exemplary hardware arrangement of a self-contained thermal landing protection system.

[0014] Figure 9 A time domain plot of characteristics of a CT system operating with a first energy recovery strategy under main power supply.

[0015] Figure 10 A time domain plot of characteristics of a CT system operating with a first energy recovery strategy during main power supply outage during exposure.

[0016] Figure 11 A time domain plot of characteristics of a CT system operating with a first energy recovery strategy after main power supply outage after exposure.

[0017] Figure 12A A flowchart of Figure 12B illustrates a method of a first energy recovery strategy.

[0018] Figure 13 A time domain plot of characteristics of a CT system operating with a second energy recovery strategy under main power supply.

[0019] Figure 14 A time domain plot of characteristics of a CT system operating with a second energy recovery strategy during main power supply outage.

[0020] Figure 15A A flowchart of Figure 15B illustrates a method of a second energy recovery strategy. DETAILED DESCRIPTION

[0021] The present specification and embodiments of the subject matter disclosed herein relate to a method and system for storing energy generated by a rotatable assembly of an X-ray tube within an X-ray generator and utilizing the stored energy to maintain rotation of the rotatable assembly and functionality of a cooling system in the event of a loss of primary power supply to the X-ray generator. The X-ray generator can be part of an imaging system such as a computed tomography (CT) imaging system. When imaging with the imaging system (e.g., with a CT system), an X-ray exposure can be performed via the X-ray generator. The X-ray exposure can include an X-ray beam generated by the X-ray generator (e.g., by an X-ray tube) and aimed at a subject. The X-ray can be attenuated by the subject and measured by an X-ray detector. In a CT system, a narrow beam of X-rays is generated by the X-ray tube and the X-ray tube and X-ray detector rotate around the subject to acquire a plurality of views, which can be reconstructed into one or more images.

[0022] In some examples, the X-ray tube can include a rotatable assembly driven by a motor and rotating at a high frequency. The motor can include a rotating bearing component called a sleeve, a fixed bearing component called a shaft, a rotor, and a fixed stator. Thus, the X-ray tube / motor can include a rotatable assembly that includes a target such as an anode, a sleeve, and a rotor. The motor can drive the target to rotate at a high speed (e.g., rotational speed exceeding 50 Hz), and can increase in temperature during an X-ray exposure. The rotatable assembly can be supported by a liquid metal bearing (LMB) that can absorb and dissipate excess heat. The LMB can experience a large temperature increase during an X-ray exposure. If the LMB is allowed to stop rotating (“land”) when at a high temperature, the LMB can transfer excess energy to a specific region of the LMB, and the rotating portion of the bearing (e.g., the rotor sleeve) can fuse with the fixed portion of the bearing. The phenomenon of the rotor stopping rotation when the LMB is at a high temperature can be referred to as hot landing. Fusion of the bearing shaft with the bearing sleeve will cause the motor to be inoperable, and the X-ray tube needs to be replaced to restore the X-ray generation system to an operable state. The X-ray tube is one of the most expensive components in a CT system, and avoiding replacement of the X-ray tube can save costs.

[0023] Hot landing can occur during a power outage or when the X-ray generator is unplugged during operation. In some cases, the X-ray generator can not include a backup power system to power a cooling system integrated in the X-ray generation system, nor to maintain rotation of the rotatable assembly and the LMB. Maintaining power to the coolant pump and continuous rotation of the rotatable assembly until the LMB cools to a suitable temperature can prevent fusion of the sleeve with the shaft.

[0024] Accordingly, in accordance with the embodiments disclosed herein, thermal runn aw can be prevented by an energy recovery storage distribution system of an x-ray based imaging system, such as a CT system. The energy recovery storage distribution system can include a motor / generator and a self-sufficient thermal runn aw protection system. The motor / generator is configured to drive a target of a rotatable assembly of an x-ray tube of the imaging system to rotate when an energy supply is obtained. In certain operating conditions, such as when the rotatable assembly is coasting down, the motor / generator can convert mechanical energy of the rotatable assembly into electrical energy. The electrical energy generated by the motor / generator can be stored in the self-sufficient thermal runn aw protection system and distributed to prevent thermal runn aw. The self-sufficient thermal runn aw protection system can include energy storage circuitry and hardware to facilitate distribution of the electrical energy to the motor and to a pump of a cooling system configured to cool the motor. By storing mechanical energy of the rotatable assembly as electrical energy during operation of the x-ray tube, it can be possible to maintain rotation of the rotatable assembly and power the pump of the cooling system upon loss of power using the stored electrical energy. In some example systems, energy of the rotatable assembly can be recovered each time the rotatable assembly coasts down; while in other examples, energy of the rotatable assembly can only be recovered and utilized when the system loses power. In examples in which the imaging system includes or is coupled to an uninterruptible power supply (UPS), the energy recovery storage distribution system can work in parallel with the UPS to provide power to the cooling system and the motor while the UPS provides power to other components of the imaging system. The systems and methods for storing and using electrical power to prevent thermal runn aw set forth in detail below can prevent bearing races from fusing to the shaft, thereby avoiding x-ray tube replacement.

[0025] As noted above, the energy recovery storage distribution system can be incorporated as part of an x-ray system of a computed tomography (CT) system. Figure 1 and Figure 2 An example of a CT system is shown. The energy recovery storage distribution system can be incorporated into the CT system in a variety of arrangements as shown. Figures 3-5 The energy recovery storage distribution system can be incorporated into the CT system in a variety of arrangements as shown. Figures 6-8Various electrical coupling arrangements between the self-contained thermal landing protection system, the motor, and additional components of the CT system are shown. A first energy recovery strategy includes recovering energy from the rotor upon deceleration of the rotor after each x-ray exposure. An x-ray exposure can be a period of time during which x-rays are generated and typically directed at a subject and measured by a detector array. During an exposure, a gantry containing an x-ray generator, x-ray tube, x-ray detector, and associated power electronics can be rotated about a target to capture multiple views. With the first energy recovery strategy, the stored energy can be used to accelerate the rotatable assembly to the appropriate speed for a predetermined period of time before the exposure occurs. In some examples, this predetermined period of time can be between 1 second and 10 seconds or more, but it is understood that the rotatable assembly can be accelerated to the appropriate speed well before the exposure actually begins. At the end of the exposure, there can be a predetermined delay between the end of the exposure and the start of the energy recovery sequence. In one example, this delay can be between 1 second and 10 seconds or more, depending on when the rotatable assembly begins to decelerate.

[0026] Figures 9-11 is a plot of the energy recovery and distribution process over time during operation of a CT system according to the first energy recovery strategy, an example method of which is shown in Figure 12A and Figure 12B The second energy recovery strategy includes recovering and storing the energy of the rotatable assembly only when power is off. Figures 13-14 is a plot of the energy recovery and distribution process over time during operation of a CT system according to the second energy recovery strategy, an example method of which is shown in Figure 15A and Figure 15B .

[0027] Figure 1 An example computed tomography (CT) system 100 configured for CT imaging is shown. In particular, the CT system 100 is configured to image a subject 112, such as a patient, an inanimate object, one or more manufactured parts, and / or a foreign object, such as a dental implant, stent, and / or contrast agent present within a body. The CT system 100 includes a gantry 102, which in turn can further include at least one x-ray source 104 configured to project an x-ray radiation beam 106 (see Figure 2 ), for imaging the subject 112 lying on a table 114. In particular, the x-ray source 104 is configured to project the x-ray radiation beam 106 toward a detector array 108 positioned on an opposite side of the gantry 102. Although Figure 1A single X-ray source 104 is depicted, but in certain embodiments, multiple X-ray sources and detectors can be employed to project multiple beams of X-ray radiation for acquiring projection data at the same or different energy levels corresponding to the patient. In some embodiments, the X-ray source 104 can enable dual energy spectral imaging through fast peak kilovoltage (kVp) switching. In some embodiments, the X-ray detector employed is a photon counting detector capable of distinguishing X-ray photons of different energies. In other embodiments, the X-ray detector is an energy integrating detector in which 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 to generate dual energy projections, with one set of X-ray sources and detectors set to a low kVp and the other set set to a high kVp.

[0028] In certain embodiments, the CT system 100 further includes an image processor unit 110 configured to reconstruct images of the target volume of the subject 112 using an iterative or analytical image reconstruction method. For example, the image processor unit 110 can reconstruct images of the target volume of the patient using an analytical image reconstruction method such as filtered back projection (FBP). As another example, the image processor unit 110 can reconstruct images of the target volume of the subject 112 using an iterative image reconstruction method such as advanced statistical iterative reconstruction (ASIR), conjugate gradient (CG), maximum likelihood expectation maximization (MLEM), model-based iterative reconstruction (MBIR), etc. In some examples, the image processor unit 110 can use an analytical image reconstruction method, such as FBP, in addition to an iterative image reconstruction method. In some embodiments, the image processor unit 110 can use a direct image reconstruction method, such as a neural network trained using deep learning.

[0029] In some CT imaging system configurations, the X-ray source projects a cone of X-ray radiation, defined with respect to an X-Y-Z Cartesian coordinate system, commonly referred to as the “imaging volume.” The cone of X-ray radiation passes through an object being imaged, such as a patient or subject. The cone of X-ray radiation impacts an array of detector elements after being attenuated by the object. The intensity of the attenuated X-ray radiation received at the detector array depends on the attenuation of the X-ray radiation by the object. Each detector element of the array generates a separate electrical signal that is a measure of the attenuation of the X-ray beam at the detector location. The attenuation measurements from all of the detector elements are individually acquired to produce a transmission profile.

[0030] In some CT systems, a gantry is used to rotate an x-ray source and detector array within an imaging volume around an object to be imaged, such that the angle at which the x-ray beam intersects the object is constantly changing. A set of x-ray radiation attenuation measurements (e.g., projection data) from the detector array at one gantry angle is referred to as a "view." A "scan" of an object includes a set of views taken at different gantry angles or viewing angles during one rotation of the x-ray source and detector. It is contemplated that the benefits of the methods described herein arise from medical imaging modalities other than CT, and thus as used herein, the term "view" is not limited to the use described above with respect to projection data from one gantry angle. The term "view" is used to mean one data acquisition whenever there are multiple data acquisitions from different angles, whether from CT, positron emission tomography (PET), or single photon emission CT (SPECT) acquisition, and / or any other modalities, including yet to be developed modalities, and combinations of them in fusion or hybrid implementations.

[0031] The projection data is processed to reconstruct an image corresponding to a two- dimensional slice taken through the object, or in some examples where the projection data includes multiple rotations or a two-dimensional (2D) array of detectors, a three-dimensional (3D) rendering of the object. One method for reconstructing an image from a set of projection data is known in the art as filtered back-projection techniques. Transmission and emission tomography reconstruction techniques also include statistical iterative methods such as maximum likelihood expectation maximization (MLEM) and ordered subsets expectation reconstruction techniques as well as iterative reconstruction techniques. This method can convert the attenuation measurements from a scan into values called "CT numbers" or "Hounsfield Units" (HU) that are used to control the brightness of the corresponding pixels on a display device.

[0032] To reduce the total scan time, a "helical" scan can be performed. To perform a "helical" scan, the patient is moved while data is acquired for a prescribed number of slices. In such a system, the position of the source relative to the patient follows a helical trajectory. The helical line mapped out by the source produces projection data from which an image in each of the prescribed slices can be reconstructed.

[0033] As used herein, the phrase "reconstructed image" is not intended to exclude embodiments of the present application in which data representative of an image is generated rather than a visual image. Thus, as used herein, the term "image" refers broadly to both visual images and data representative of visual images. However, many embodiments generate (or are configured to generate) at least one visual image.

[0034] Figure 2 An exemplary imaging system 200 similar to a CT system 100 of Figure 1 is illustrated. In accordance with aspects of the present disclosure, the imaging system 200 is configured for imaging a subject 204 (e.g.,Figure 1 of the subject 112) is imaged. In some embodiments, the imaging system 200 includes a detector array 108 (see Figure 1 ). The detector array 108 also includes a plurality of detector elements 202 that together sense the beam of x-ray radiation 106 (see Figure 2 ) that passes through a subject 204, such as a patient, to acquire corresponding projection data. In some embodiments, the detector array 108 can be fabricated to include a multi-slice configuration of multiple rows of cells or detector elements 202, with one or more additional rows of detector elements 202 arranged in a parallel configuration for the acquisition of projection data. The detector elements 202 can also be referred to as pixels or detector pixels.

[0035] In certain embodiments, the imaging system 200 is configured to traverse different angular positions around the subject 204 to acquire the required projection data. Thus, the gantry 102 and components mounted thereon can be configured to rotate around the rotation center 206 for the acquisition of, for example, projection data at different energy levels. Alternatively, in embodiments where the projection angle relative to the subject 204 is varied over time, the mounted components can be configured to move along a generally curved path rather than along a segment of a circle.

[0036] Thus, as the x-ray source 104 and the detector array 108 rotate, the detector array 108 collects data of the attenuated x-ray beam. The data collected by the detector array 108 is then subjected to pre-processing and calibration to condition the data to represent the line integrals of the attenuation coefficients of the scanned subject 204. The processed data is generally referred to as projections. In some examples, individual detectors or detector elements 202 in the detector array 108 can include photon counting detectors that register individual photon interactions into one or more energy bins.

[0037] The acquired projection data sets can be used for basis material decomposition (BMD). During BMD, the measured projections are converted to a set of material density projections. The material density projections can be reconstructed to form a set of material density maps or images for each respective basis material, such as bone, soft tissue, and / or contrast agent maps. The density maps or images can in turn be associated to form a 3D volume image of the basis materials (e.g., bone, soft tissue, and / or contrast agent) in the imaged volume.

[0038] Once reconstructed, the basis material images produced by the imaging system 200 show internal features of the subject 204 in terms of the densities of the two basis materials. The density images can be displayed to reveal these features. In the traditional approach to diagnosing medical conditions, such as disease states, and more generally medical events, a radiologist or physician will consider a hard copy or display of the density images to identify characteristic features of interest. Such features can include lesions, sizes, and shapes of particular anatomical structures or organs, and other features that should be discernible in the images based on the skill and knowledge of the individual practitioner.

[0039] In one embodiment, the imaging system 200 includes a control mechanism 208 to control movement of components, such as rotation of the gantry 102 and operation of the x-ray source 104. In certain embodiments, the control mechanism 208 also includes an x-ray controller 210 configured to provide power and timing signals to the x-ray source 104. Additionally, the control mechanism 208 includes a gantry motor controller 212 configured to control the rotational speed and / or position of the gantry 102 based on imaging requirements.

[0040] In certain embodiments, the control mechanism 208 also includes a data acquisition system (DAS) 214 configured to sample analog data received from the detector elements 202 and convert the analog data to digital signals for subsequent processing. The DAS 214 can be further configured to selectively aggregate data from subsets of the detector elements 202 into so-called macro-detectors. Data sampled and digitized by the DAS 214 is transmitted to a computer or computing device 216 via a current collection ring 213. In one example, the computing device 216 stores the data in a storage device or mass storage 218. For example, the storage device 218 can be any type of non-transitory memory and can include a hard disk drive, a floppy disk drive, a compact disc - read / write (CD-R / W) drive, a digital versatile disc (DVD) drive, a flash drive, and / or a solid-state storage drive.

[0041] Further, 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 for controlling system operations such as data acquisition and / or processing. In certain embodiments, the computing device 216 controls system operations based on operator input. The computing device 216 receives the operator input, which includes, for example, commands and / or scan parameters, via an operator console 220 operatively coupled to the computing device 216. The operator console 220 can include a keyboard or a touch screen to allow the operator to designate commands and / or scan parameters.

[0042] While Figure 2An operator console 220 is illustrated, although more than one operator console can be coupled to the imaging system 200, e.g., for inputting or outputting system parameters, requesting examinations, plotting data, and / or viewing images. Moreover, in certain embodiments, the imaging system 200 can be coupled to multiple displays, printers, workstations, and / or the like, e.g., located locally or remotely within an institution or hospital or at a completely different location, via one or more configurable wired and / or wireless networks, such as the Internet and / or virtual private networks, wireless telephony networks, wireless local area networks, wired local area networks, wireless wide area networks, wired wide area networks, etc.

[0043] In one embodiment, for example, the imaging system 200 includes or is coupled to a picture archiving and communication system (PACS) 224. In one example implementation, the PACS 224 is further coupled to remote systems, such as radiology information systems, hospital information systems, and / or to internal or external networks (not shown) to allow operators in different locations to supply commands and parameters and / or gain access to image data.

[0044] The computing device 216 uses the operator-supplied and / or system-defined commands and parameters to operate a table motor controller 226, which in turn can control a table 114, which can be a motorized table. In particular, the table motor controller 226 can move the table 114 to properly position the subject 204 in the gantry 102 to acquire projection data corresponding to a target volume of the subject 204.

[0045] As previously mentioned, the DAS 214 samples and digitizes the projection data acquired by the detector elements 202. Subsequently, an image reconstructor 230 uses the sampled and digitized X-ray data to perform a high-speed reconstruction. Although Figure 2 The image reconstructor 230 is illustrated as a separate entity, although in certain embodiments, the image reconstructor 230 can form part of the computing device 216. Alternatively, the image reconstructor 230 can not be present in the imaging system 200, and instead the computing device 216 can perform one or more functions of the image reconstructor 230. In addition, the image reconstructor 230 can be located locally or remotely, and can be operatively connected to the imaging system 200 using a wired network or a wireless network. In particular, one example embodiment can use computing resources in a “cloud” network cluster for the image reconstructor 230.

[0046] In one embodiment, the image reconstructor 230 stores the reconstructed images in the storage device 218. Alternatively, the image reconstructor 230 can send the reconstructed images to the computing device 216 for useable patient information for diagnosis and assessment. In certain embodiments, the computing device 216 can transmit the reconstructed images and / or patient information to a display or display device 232 communicatively coupled to the computing device 216 and / or the image reconstructor 230. In some embodiments, the reconstructed images can be transmitted from the computing device 216 or the image reconstructor 230 to the storage device 218 for short-term or long-term storage.

[0047] Information can be transmitted between components residing in the gantry 102 and external devices, such as the computing device 216 and / or the image reconstructor 230, via a slip ring 213 that facilitates electronic communication across a rotating gantry. In some examples, the gantry and internal components (e.g., the control mechanism 208, the x-ray source 104, the detector array 108) can be collectively defined as a CT scanner, and thus the computing device 216 and the image reconstructor 230 can reside outside of the scanner.

[0048] The CT system described above in connection with Figure 1 and Figure 2 The CT system described above can be one example of a system that integrates an energy recovery storage distribution system. Figure 3 is a schematic diagram of a CT system 300 that includes an energy recovery storage distribution system. The CT system 300 can include a power distribution unit (PDU) 302. The PDU 302 can be coupled to an external power source (e.g., a power grid) via an outlet. The PDU 302 can receive power from the external power source and distribute the power to a plurality of different electrical components. The PDU 302 can also have a protection function and be able to cut off current flow through the PDU 302 to prevent power surges from reaching other components of the CT system 300. The PDU can be coupled to a plurality of electronic devices, such as reconstruction hardware 304 (which is a non-limiting example of the image reconstructor 230), a blower and fan 306, a stationary power board (SPB) 308, the operator console 220, and the worktable 114, by a first power distribution path 303 that is positioned outside of the gantry and thus coupled to the gantry via the slip ring 213.

[0049] The PDU 302 can also be coupled to a second power distribution path 309 that couples the PDU 302 with elements of the rack. The second power distribution path can include parallel branches, where a first branch 311 supplies power to the X-ray tube 316, and a second branch 313 supplies power to auxiliary electronics on the rotating side of the collector ring 213. The first branch 311 can couple the PDU 302 to an X-ray inverter 312. The X-ray inverter 312 is configured to convert direct current provided by the PDU 302 to alternating current. The X-ray inverter 312 can generate alternating current at a particular frequency that depends on the specifications of other components of the CT system. The X-ray inverter 312 can be coupled across the collector ring 213 to an X-ray generator 314. The X-ray generator 314 is configured to convert the AC signal provided by the X-ray inverter to direct current and generate a high voltage that can be applied to the X-ray tube 316. The X-ray tube 316 can include a cathode that emits electrons based on the current applied to a cathode filament. The cathode can be positioned a distance from a target 319, which in some examples can be a rotatable disk-shaped anode. When the X-ray generator is energized and generates a voltage difference, a significant potential difference will form between the cathode and the anode. Due to the large potential difference, electrons released by the cathode can accelerate toward the target 319. The electrons can release X-rays when they impact the target 319. The target 319 can be driven to rotate by a motor 321 that includes a rotor 318 and a stator 324 to disperse heat generated by the electrons impacting the target 319. As previously mentioned, the motor 321 can be a motor / generator that is configured to operate as a motor under certain conditions and as a generator under other conditions.

[0050] The stator 324 is a non-rotating component of the motor 321 that can receive electrical power to drive the rotor 318 to rotate, which can be a rotatable component of the motor 321. As such, the motor 321 / X-ray tube can include a rotatable assembly 327 that includes the rotor 318, a shaft 325 of a liquid metal bearing (LMB) 320, and the target 319. The components of the rotatable 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 when the rotatable assembly 327 rotates. The LMB 320 can include a rotatable sleeve 325 that surrounds the shaft 322. The gap 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 to circulate the liquid metal to preferred areas in the gap between the sleeve and the shaft. Rotation of the rotatable assembly and circulation of the liquid metal can act to dissipate heat.

[0051] The coolant loop 332 can include a cooling channel 326 that fluidly couples the tube pump 328 and the heat exchanger 330 to the motor 321. The cooling channel 326 can include portions that are thermally coupled to one or more components of the rotatable assembly 327, such as the rotor 318, the LMB 320, the shaft sleeve 325, and / or the shaft 322. The cooling channel 326 can be a pipe that connects portions of the coolant loop 332, or the cooling channel 326 can be a channel integrated into components of the X-ray tube 316, the stator 324, the tube pump 328, and / or the heat exchanger 330. The tube pump 328 can pump coolant from the heat exchanger 330 to the motor 321 (e.g., around the LMB 320), where the coolant accumulates heat generated by the rotatable assembly 327. The coolant can return to the heat exchanger 330 (e.g., via a return path not shown in FIG. 3), where the heat accumulated in the coolant is released to the environment. Figure 3

[0052] A second leg of the second power distribution path 309 can couple the PDU 302 to an auxiliary inverter 310. The auxiliary inverter 310 can convert direct current provided by the PDU 302 to alternating current. The auxiliary inverter 310 can be electrically coupled to a rotating auxiliary power unit 334 via the slip ring 213. The rotating auxiliary power unit 334 can be capable of directing a flow of electrical power to elements of the CT system 300 that rotate within the gantry. The rotating auxiliary power unit 334 can include a rectification filter board 336 that is a circuit board configured to process AC power signals. In some examples, the rectification filter board 336 can have a frequency range between 300 MHz and 3 GHz. The rectification filter board 336 can include electrical components that can control, distribute, and filter electrical power received by the rotating auxiliary power unit 334 through the slip ring 213 so that it can be used by a plurality of electrical devices coupled to the rotating auxiliary power unit 334.

[0053] ​The rectification filter board 336 can be coupled to a rotating control board (RCB) 338 and a 48V fuse control board 340 within the rotating auxiliary power unit 334. The RCB 338 can be coupled to the stator 324 of the motor 321 via a plurality of cables, which in some examples can include three separate cables surrounded by a conductive shield. The RCB 338 can include a controller that can include a memory storing instructions for operation of the motor 321 and distribution of 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 can also be coupled to an energy storage circuit 342. The energy storage circuit 342 can include one or more batteries, capacitors, or the like configured to store energy. In some examples, the energy storage circuit 342 can include a controller that can include a memory storing instructions executable by one or more processors for recovering rotational kinetic energy from the rotatable assembly 327 and storing the rotational kinetic energy as electrical energy. As the rotatable assembly 327 slows, rotational kinetic energy can be recovered and converted to electrical energy and can be passed to the RCB 338 within the rotating auxiliary power unit 334. The recovered electrical energy can be passed from the RCB 338 to the energy storage circuit 342, where the recovered energy can be stored in one or more batteries, capacitors, or the like. The energy storage circuit 342 can issue commands to the RCB 338 related to the start and termination of the energy recovery process, which can be forwarded by the RCB 338 to the stator 324.

[0054] The energy storage circuit 342 can be coupled to a pump circuit 344. The pump circuit 344 can include a controller having a memory storing instructions related to operation of the tube pump 328, and one or more processors configured to execute the instructions. The pump circuit 344 can be coupled to the tube pump 328 and can control operation of the tube pump 328 in the event of a power outage. If a power outage occurs, the energy stored by the energy storage circuit 342 can be forwarded to the pump circuit 344 and can be delivered to the tube pump 328 according to instructions stored in the pump circuit 344. In the event of a power outage, the energy storage circuit 342 can provide power to the motor 321 by supplying power to the RCB 338, which can be distributed to the motor 321 according to instructions stored in the RCB 338.

[0055] As described above, the rectification filter board 336 can be coupled to a 48V fuse control board 340. The 48V fuse control board 340 can include a controller that can include a memory storing instructions for distributing energy to a plurality of devices, and one or more processors configured to execute the instructions stored in the memory. The 48V fuse control board 340 can include a plurality of fuses that can prevent power surges from reaching devices coupled to the 48V fuse control board 340. The 48V fuse control board 340 can power a plurality of devices by providing 48V voltage to the plurality of devices including the tube pump 328, the detector system 348, and a plurality of other 48V loads 346.

[0056] The detector system 348 can be configured to detect X-rays emitted by the X-ray tube 316 and penetrating the subject 112. The detector system 348 can 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 can receive power from the 48V fuse control board 340 and distribute the power to other components of the detector system 348. As described above in connection with the rectification filter board 336, the detector power management unit 352 can include a plurality of fuses that can prevent power surges from reaching the detector array 108. Figure 1 and Figure 2 The detector array 108 can detect X-rays that have been attenuated by an object, such as the subject 112. The detector array 108 can 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 can maintain a temperature of the detector array 108 to prevent overheating.

[0057] Figure 4 is a schematic diagram of a CT system 400, which is similar to the CT system 100 Figure 3The schematic diagram of CT system 300 is similar. Components included in CT system 300 and CT system 400 are numbered identically, and the description of these components provided above for CT system 300 applies equally to CT system 400. CT system 400 includes an uninterruptible power supply (UPS) 404. This UPS 404 can provide backup power to CT system 400 during a power loss / outage (e.g., when power from a primary power source, such as a power grid, is no longer being supplied to PDU 302). During an outage, power can be output from UPS 404 along a first path 406. First path 406 can be indicated by a series of dashed arrows originating from UPS 404. Along this first path 406, power can be output from UPS 404 to PDU 302. PDU 302 can distribute power through first power distribution path 303 to a number of off-rack devices, such as reconstruction hardware 304, blowers and fans 306, SPB 308, operator desktop console 220, and worktable 114. PDU 302 can also distribute power through second power distribution path 309 to auxiliary inverter 310, across collection ring 213 to rectification filter board 336. First path 406 can continue from rectification filter board 336 to 48V fuse control board 340. This 48V fuse control board 340 can distribute power to detector system 348 and other 48V loads 346. Via first path 406, detector system 348 and other 48V loads 346 can be powered by UPS 404. By providing power to detector system 348 and other 48V loads 346 via the UPS during an outage, it can be possible to collect scan data in the event of an outage, which can reduce the need to repeat scans during an outage, thereby preventing interruption of CT procedure scheduling.

[0058] During a power outage, other devices that can require power can be powered via the second path 408 from energy stored in the energy storage circuit 342. The energy stored in the energy storage circuit 342 can be used to power the tube pump 328 and the motor 321. Via the second path 408, energy can be dispensed from the energy storage circuit 342, through the pump circuit 344, and then to the tube pump 328. As an additional part of the second path 408, energy can be dispensed from the energy storage circuit 342 to the RCB 338, and power can be dispensed from the RCB 338 to the motor 321. When the main power supply is providing power to the CT system 400, power can flow to the tube pump 328 via the first pump system 410, which includes the 48V fuse control board 340, the rectification filter board 336, and the electrical connections between the 48V fuse control board 340 and the tube pump 328. When the main power supply loses power (e.g., due to a power outage), power can flow to the tube pump 328 via the second pump system 412, which includes the energy storage circuit 342, the pump circuit 344, and the electrical connections between the pump circuit 344 and the tube pump 328. It is to be understood that the power paths (e.g., the first path 406 and the second path 408) are shown schematically and are not intended to be independent of the electrical connections between the various devices shown in FIG. 4. For example, the power path from the RCB 338 to the motor 321 is implemented via a cable that couples the RCB 338 to the motor 321, rather than via a separate connection. Figure 4

[0059] Thus, the UPS 404 and the energy storage circuit 342 can provide power to different parts of the CT system 400. The energy storage circuit 342 can be configured to provide power to the motor 321 and the tube pump 328, while the UPS 404 can be configured to provide power to the detector system 348 and the plurality of off-rack devices.

[0060] As shown in FIG. 4, the RCB 338, the energy storage circuit 342, and the pump circuit 344 can define a self-contained hot landing protection system 402. In the example shown in FIG. 4, the self-contained hot landing protection system 402 includes components that are located on / are part of the rotating auxiliary power unit 334 (e.g., the RCB 338) and components that are 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 landing protection system 402 can be located in different locations within a CT system without departing from the scope of the present disclosure, as described in more detail below. Figure 4 Figure 3 Figure 4

[0061] ​​​​In some examples (not shown), the self-contained thermal landing protection system 402 may be included in the rotating auxiliary power supply unit 334. Within the rotating auxiliary power supply unit 334, the self-contained thermal landing protection system 402 may be coupled to the rectifier filter board 336 and the 48V fuse control board 340. The self-contained thermal landing protection system 402 may be electrically coupled to the motor 321 via multiple cables extending from the RCB 338 to the motor 321. Therefore, in these examples, the energy storage circuit 342 and the pump circuit 344 may be included within / as part of the rotating auxiliary power supply unit 334.

[0062] Figure 5 A schematic diagram of an exemplary CT system 500 is shown, in which a self-contained thermal landing protection system 402 is located at an alternative position within the CT system 500 relative to the CT system 400. Figure 5 In this configuration, the self-contained thermal landing protection system 402 is not included in the rotating auxiliary power supply unit 334, but is coupled to it. Furthermore, the self-contained thermal landing protection system 402 can be coupled to the motor 321 via three cables, and can also be coupled to the tubular pump 328 and the rectifier filter board 336 in the rotating auxiliary power supply unit 334 via corresponding cables or other coupling methods. By moving the components of the self-contained thermal landing protection system 402 out of the rotating auxiliary power supply unit 334, the self-contained thermal landing protection system 402 can be closer to the motor 321 than when its components (especially the RCB 338) are positioned on the rotating auxiliary power supply unit 334. Positioning the self-contained thermal landing protection system 402 closer to the motor 321 reduces the number of cables used to couple the motor 321 to the RCB 338, thereby reducing the required electromagnetic shielding and thus reducing manufacturing costs and complexity. In one example, the number of cables used to couple motor 321 to RCB 338 can be reduced from three cables to two cables.

[0063] There may be various coupling arrangements between the energy storage circuit 342, RCB 338 and pump circuit 344 in the self-contained thermal landing protection system 402. Figure 6 This is a schematic diagram of the motor circuit 600 including the self-contained thermal landing protection system 402. The self-contained thermal landing protection system 402 may include components coupled to the CT system 300, CT system 400, or CT system 500. Figure 6 This includes a primary power source 602 (e.g., a main power supply) that provides power to the self-contained thermal landing protection system 402. The primary power source 602 may be a rectifier filter board 336 that receives power from an auxiliary inverter 310, which in turn receives power from a PDU 302 (and ultimately from the grid), a process that has been integrated. Figure 3A diode 606 can be coupled to an outlet of the primary power source 602 to ensure that current can only flow from the primary power source 602 to the self-contained thermal landing protection system 402 in one direction.

[0064] The self-contained thermal landing protection system 402 can include an energy storage circuit 342, an RCB 338, a pump circuit 344, and a capacitor bank 604. In the motor circuit 600, the energy storage circuit 342 can be connected in series and parallel configurations with the primary power source 602. In some examples of the motor circuit 600, the energy storage circuit 342 can include galvanic isolation. The series and parallel configurations can enable the energy storage circuit 342 to control the distribution of energy through the self-contained thermal landing protection system 402. The energy storage circuit 342 can include one or more energy storage technologies, such as a battery, a capacitor, or a superconductor. The energy storage circuit 342 can be arranged in parallel with the capacitor bank 604 and the RCB 338. The capacitor bank 604 can be capable of storing energy in the self-contained thermal landing protection system 402 and reducing fluctuations in voltage provided by the primary power source 602 to the system. The capacitor bank 604 can operate as a filtering element during normal operation to limit the amount of electromagnetic interference (EMI) and electromagnetic compatibility (EMC). The capacitor bank 604 can also operate as a supplemental energy storage element. In some examples, the capacitor bank 604 can be arranged to have a different time constant than the energy storage circuit 342 to access stored energy. The capacitor bank 604 can operate as a buffer for different energy storage technologies within the energy storage circuit 342 and provide additional energy storage capabilities. The RCB 338 can be coupled to the stator 324 of the motor 321 through a plurality of cables 608. The RCB 338 can supply power from the primary power source 602 or the energy storage circuit 342 to the stator 324 of the motor 321 to drive the rotatable assembly 327 in rotation. Additionally, energy recovered from the motor 321 can be conducted through the plurality of cables 608 and the RCB 338 can distribute the recovered energy to the energy storage circuit 342. The energy storage circuit 342 can be arranged in series with the pump circuit 344 and the energy storage circuit 342 can direct power from the primary power source 602 to the pump circuit 344 or the energy storage circuit 342 can supply stored energy to the pump circuit 344. The pump circuit 344 can control operation of the tube pump 328 and direct power to the tube pump 328.

[0065] Figure 7 Alternative circuit arrangements of the energy storage circuit 342, the RCB 338, and the pump circuit 344 are shown. Figure 7 is a schematic diagram of a motor circuit 700 including the self-contained thermal landing protection system 402. The motor circuit 700 can be composed of the components described in connection with Figure 3 , Figure 4 , Figure 5 and Figure 6 . In Figure 7In the example shown, tank circuit 342 can be arranged in series with main power supply 602 and also in series with the parallel configuration of capacitor bank 604 and RCB 338. Tank circuit 342 can be arranged in series with pump circuit 344, as described above in connection with Figure 6 Motor circuit 700 can be more easily controlled than motor circuit 600, but can result in higher voltages being applied to capacitor bank 604 and RCB 338. Higher voltages applied to capacitor bank 604 and RCB 338 can increase design requirements for capacitor bank 604 and RCB 338.

[0066] Figure 8 Another alternative circuit arrangement of tank circuit 342, RCB 338, and pump circuit 344 is shown. Figure 8 is a schematic diagram of motor circuit 800 including self-contained thermal landing protection system 402. Motor circuit 800 can be constructed from the various components described in detail in connection with Figure 3 Figure 4 Figure 5 and Figure 6 In the example shown, tank circuit 342 can be arranged in series with main power supply 602 and also in series with the parallel configuration of capacitor bank 604 and RCB 338. Tank circuit 342 can be arranged in series with pump circuit 344, as described above in connection with Figure 8

[0067] ​​​Thus, the above-described system provides an energy recovery storage distribution system including a self-sufficient thermal landing protection system. The energy recovery storage distribution system is configured to recover energy from the motor of the x-ray tube and apply stored energy to the motor and / or a coolant pump, thereby ensuring continued rotation of the rotatable assembly and cooling in the event of a power outage of a main power source, such as a power grid or a generator. The energy recovery storage distribution system can be controlled to operate according to various control strategies. A first control strategy can include capturing energy of the rotatable assembly after each exposure and storing the energy for reuse in the next acceleration of the rotatable assembly or in the event of a loss of power of the main power source. In the event of a power outage, the stored energy can be used to maintain the rotatable assembly rotating at a low frequency. Energy can be recovered during a ramp down, which refers to a period of time during which the speed of the rotatable assembly gradually decreases over time after an x-ray exposure has occurred and power of the main power source is no longer applied to the motor. During the ramp down of the rotatable assembly, there is both energy recovery and thermal energy loss. The faster the rotatable assembly decreases in speed, the higher the proportion of energy recovery relative to thermal energy loss. The kinetic energy recovered as the rotatable assembly slows down can be converted to electrical energy and stored. The stored energy can be used during the next ramp up of the rotatable assembly. A ramp up refers to a period of time during which the rotatable assembly increases in speed before an exposure begins. By storing energy during the ramp down and reusing the energy during the ramp up, the additional power demand for accelerating the rotatable assembly is greatly reduced, thereby resulting in additional energy savings and a reduction in the generation of electrical stress and electromagnetic interference of the power chain subsystem. The first control strategy will be described below with reference to a plurality of time-domain graphs shown in FIGS. 6A-6D. Figures 9-11 The first control strategy is illustrated with reference to the plurality of time-domain graphs shown in FIGS. 6A-6D.

[0068] Figure 9The time-domain graph 900 illustrates rotatable 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 can be a power grid or a generator). The first sub-graph 902 includes a first curve 910 representing rotatable assembly speed over time (e.g., the speed of rotatable assembly 327); the second sub-graph 904 includes a second curve 912 representing the amount of energy recovered from rotatable assembly 327 and stored in an energy storage circuit (e.g., energy storage circuit 342) and depleted from the energy storage circuit by the energy recovery storage and distribution system; the third sub-graph 906 includes a third curve 914 representing the activity state of a tube pump (e.g., tube pump 328) over time; and the fourth sub-graph 908 includes a fourth curve 916 representing the amount of power directed to the motor (e.g., motor 321) from the main power source (shown by the dashed portion of fourth curve 916) and the energy storage circuit (shown by the solid portion of fourth curve 916). The first, second, and fourth sub-graphs 902, 904, and 908 each include respective values (e.g., rotatable assembly speed, energy, and power flow values) that increase along the y-axis, and the third sub-graph 906 shows pump operation in binary (on / off) form. The sub-graphs are synchronized in time, and a time point of interest is marked with a dashed line.

[0069] Prior to T1, an x-ray exposure is in progress, during which the rotatable assembly is rotating at a high speed (as shown by first curve 910), the pump is in operation and controlled according to a cooling strategy required by first pump system 410 (as shown by third curve 914, which indicates via hatching that the pump is being controlled by first pump system 410), and the power flow to the motor is from a connection to a main power source such as a power grid, as shown by the dashed portion of fourth curve 916. The exposure ends at T1. Between T1 and T2 is a ramp-down phase, during which the rotatable assembly speed decreases, as shown by the negative slope segment of first curve 910. Energy is recovered from the decelerating rotatable assembly, as shown by the positive slope of second curve 912 between T1 and T2. In some examples, there can be a slight delay (e.g., 1-10 seconds) between when the rotatable assembly begins to ramp down and when energy begins to be recovered from the rotatable assembly and stored in the energy storage circuit. No power is supplied to the motor during the ramp-down process, and the recovered energy is supplied to the energy storage circuit. The amount of energy supplied to the storage circuit is shown as the negative portion of fourth curve 916 between T1 and T2.

[0070] Between T2 and T3 is a rest period where no x-ray exposure is taking place. During this period, the rotatable assembly speed is maintained at a constant low speed, which can be 50 Hz or similar frequency. The low rotation speed is shown by the horizontal segment of the first curve 910 on the first sub-plot 902. The amount of stored recovered energy remains constant between T2 and T3, as shown by the horizontal segment of the second curve 912 between T2 and T3 (e.g., energy recovery stops after T2). Between T2 and T3, the main power source provides a constant low level of power current to the motor to maintain the low rotatable assembly speed, as shown by the horizontal segment of the fourth curve 916 between T2 and T3 in the fourth sub-plot 908.

[0071] Between T3 and T4, the rotatable assembly can ramp up in preparation for the next exposure. The ramp up process can include accelerating the rotatable assembly to reach a commanded / threshold speed for the next exposure. In some examples, the commanded / threshold speed can be 180 Hz for a high speed exposure and 145 Hz for a low speed exposure. In the first sub-plot 902, the accelerated rotatable assembly can be seen by the positive slope of the first curve 910 between T3 and T4. The energy stored in the energy storage circuit can be used to facilitate the ramp up, thereby reducing the amount of stored recovered energy. In the second sub-plot 904, the reduction in stored recovered energy can be seen from the negative slope of the second curve 912 between T3 and T4. The energy supplied from the energy storage circuit to the motor increases at T3 to provide sufficient energy to accelerate the rotatable assembly between T3 and T4. The exposure can occur after T4, during which the rotatable assembly rotates at high speed, as shown by the horizontal segment of the first curve 910 after T4. The pump runs as needed during this process to maintain the rotatable assembly, LMB, etc. below a threshold temperature, which process includes times before T1, after T4, and during T1-T4. While constant running of the pump is depicted in the third sub-plot 906 by the constant value of the third curve 914, it is to be understood that the speed of the pump can be adjusted and / or the pump can run in an intermittent manner in order to meet the cooling needs.

[0072] Figure 10 The time domain plot 1000 shows rotatable assembly speed, recovered stored energy, pump running, and power to the motor in a CT system, such as CT system 300, CT system 400, or CT system 500, etc., similar to Figure 9but describes operation when powered from a main power source (which can be the PDU 302) to the imaging system until a power loss is detected during an exposure and the energy stored in the self-sufficient thermal landing protection system is used to spin the rotatable assembly and operate the pump. The first sub-plot 1002 includes a first curve 1010 representing rotatable assembly speed over time; the second sub-plot 1004 includes a second curve 1012 representing the amount of energy stored in the energy storage circuit; the third sub-plot 1006 includes a third curve 1014 representing the activity state of the tube pump over time; and the fourth sub-plot 1008 includes a fourth curve 1016 representing the amount of power directed to the motor from the main power source (shown by the dashed portion of the fourth curve 1016) and the energy storage circuit (shown by the solid portion of the fourth curve 1016). The first, second, and fourth sub-plots 1002, 1004, and 1008 each include respective values (e.g., rotatable assembly speed, energy, and power flow values) that increase along the y-axis, and the third sub-plot 1006 shows pump operation in binary (on / off) form. The sub-plots are synchronized in time, and the time points of interest are marked with dashed lines.

[0073] Prior to T1, an x-ray exposure is in progress, so the rotatable assembly is spinning at a high speed, the pump is in operation and controlled according to the cooling strategy required by the first pump system 410 (as indicated by the third curve 1014, which indicates via hatching that the pump is being controlled by the first pump system 410), and the power flow to the motor is from the main power source, such as a connection to the power grid. At T1, a power loss occurs, such that the power supplied from the main power source is interrupted. After T1, the pump is forced to operate using the energy stored within the energy storage circuit 342, which is shown by the horizontal portion of the third curve 1014 that does not include a fill pattern (e.g., a white / blank segment). After the power loss, the same process described in connection with the first sub-plot 1002 occurs between T1 and T2. Thus, between T1 and T2, the rotatable assembly speed decreases, as shown by the negative slope segment of the first curve 1010. Energy is recovered from the decelerating rotatable assembly, as shown by the positive slope of the second curve 1012 between T1 and T2. In some examples, there can be a slight delay (e.g., 1-10 seconds) between the rotatable assembly beginning to ramp down and energy beginning to be recovered from the rotatable assembly and stored in the energy storage circuit. No power is supplied to the motor during the ramp down process, and all of the energy recovered as the rotatable assembly spins is supplied to the energy storage circuit. The amount of energy supplied to the storage circuit is shown as the negative portion of the fourth curve 1016 between T1 and T2. Figure 9

[0073] Prior to T1, an x-ray exposure is in progress, so the rotatable assembly is spinning at a high speed, the pump is in operation and controlled according to the cooling strategy required by the first pump system 410 (as indicated by the third curve 1014, which indicates via hatching that the pump is being controlled by the first pump system 410), and the power flow to the motor is from the main power source, such as a connection to the power grid. At T1, a power loss occurs, such that the power supplied from the main power source is interrupted. After T1, the pump is forced to operate using the energy stored within the energy storage circuit 342, which is shown by the horizontal portion of the third curve 1014 that does not include a fill pattern (e.g., a white / blank segment). After the power loss, the same process described in connection with the first sub-plot 1002 occurs between T1 and T2. Thus, between T1 and T2, the rotatable assembly speed decreases, as shown by the negative slope segment of the first curve 1010. Energy is recovered from the decelerating rotatable assembly, as shown by the positive slope of the second curve 1012 between T1 and T2. In some examples, there can be a slight delay (e.g., 1-10 seconds) between the rotatable assembly beginning to ramp down and energy beginning to be recovered from the rotatable assembly and stored in the energy storage circuit. No power is supplied to the motor during the ramp down process, and all of the energy recovered as the rotatable assembly spins is supplied to the energy storage circuit. The amount of energy supplied to the storage circuit is shown as the negative portion of the fourth curve 1016 between T1 and T2.

[0074] After T2, the rotatable assembly reaches a threshold speed (e.g., the low speed described above), and the recovered energy is used to maintain the rotatable assembly at the low speed, such as 50 Hz. Between T2 and T3, the stored energy decreases linearly, as shown by the exponential decrease of the second curve 1012 between T2 and T3 in the second sub-plot 1004. The stored energy is used to maintain operation of the pump (as shown by the third curve 1014 between T1 and T4) and to rotate the rotatable assembly at the low speed (as shown by the horizontal segment of the first curve 1010 between T2 and T3). The power to the motor is constant between T2 and T3, as shown by the horizontal segment of the fourth curve 1016 between T2 and T3. As shown by the solid portion of the fourth curve 1016, power flows from the tank circuit to the motor.

[0075] At T3, the supply of stored energy in the tank circuit reaches a lower threshold, which can indicate that there is insufficient energy remaining in the tank circuit to power both the motor and the tube pump simultaneously. Accordingly, the power supplied to the motor from the tank circuit is terminated, and the power supplied to the motor drops to 0 at T3. After T3, the rotatable assembly decelerates to a stop due to the lack of stored energy to power rotation of the rotatable assembly. The process of the rotatable assembly decelerating to a stop due to inertia is shown in the first sub-plot 1002 as the nonlinear decay of the rotatable assembly speed between T3 and T4. As the rotatable assembly ramps down, energy is recovered from the rotatable assembly, but this recovery rate decreases compared to the energy recovery rate between T2 and T3 because the speed of the rotatable assembly is decreasing. At T4, the rotatable assembly speed equals 0, indicating that the rotatable assembly has stopped. After the rotatable assembly stops at T4, the pump is deactivated, as shown by the pump activity state dropping to 0 after T4 as represented by the third curve 1014. The pump can be deactivated when the rotatable assembly speed reaches 0, as shown, or the pump can be deactivated when the stored recovered energy is depleted or when the rotatable assembly temperature reaches a threshold temperature. The pump remains in an active state until the rotatable assembly speed drops to 0 in order to provide effective cooling throughout the process and to prevent hot landing by ensuring that the LMB temperature and the rotatable assembly temperature decrease after power is removed. Rotating the rotatable assembly at a low speed for as long as possible helps to prevent hot landing by keeping the rotatable assembly and LMB in motion, thereby preventing mechanical contact and potential fusing between the bushings and the shaft within the rotatable assembly.

[0076] Figure 11 The time-domain plot 1100 of FIG. 11 shows the rotatable assembly speed, recovered stored energy, pump operation, and power to the motor of a CT system, similar to Figure 9 and Figure 10but is described as operating on power provided by the main power supply until a power loss is detected between X-ray exposures. The first sub-plot 1102 includes a first curve 1110 representing rotatable assembly speed over time; the second sub-plot 1104 includes a second curve 1112 representing the amount of energy stored in the tank circuit; the third sub-plot 1106 includes a third curve 1114 representing the activity state of the tube pump over time; and the fourth sub-plot 1108 includes a fourth curve 1116 representing the amount of power directed to the motor from the main power supply (shown by the dashed portion of the fourth curve 1116) and the tank circuit (shown by the solid portion of the fourth curve 1116). The first, second, and fourth sub-plots 1102, 1104, and 1108 each include respective values (e.g., rotatable assembly speed, energy, and power flow values) that increase along the y-axis, and the third sub-plot 1106 shows pump operation in binary (on / off) form. The sub-plots are synchronized in time, and the time points of interest are marked with dashed lines.

[0077] Prior to T1, an X-ray exposure is in progress, so the rotatable assembly is rotating at high speed, the pump is in operation and controlled according to the cooling strategy required by the first pump system 410 (as shown by the third curve 1114, which indicates via hatching that the pump is being controlled by the first pump system 410), and the power flow to the motor is from the main power supply. The exposure ends at T1, and the power supply to the motor is terminated. Between T1 and T2 is a ramp-down phase during which the rotatable assembly speed decreases, as shown by the negative slope section of the first curve 1110. Energy is recovered from the decelerating rotatable assembly, as shown by the positive slope of the second curve 1112 between T1 and T2. In some examples, there can be a slight delay (e.g., 1-10 seconds) between the start of the ramp-down of the rotatable assembly and the start of the recovery of energy from the rotatable assembly and storage in the tank circuit. No power is supplied to the motor during the ramp-down process, and the energy recovered from the rotatable assembly is supplied to the tank circuit. The amount of energy supplied to the tank circuit is shown as the negative portion of the fourth curve 1116 between T1 and T2. The pump is powered by the first pump system 410 until the power loss is detected.

[0078] At T2, the rotatable assembly reaches a threshold speed (e.g., the low speed described above). Between T2 and T3 is a rest period, during which no x-ray exposure is taking place. During this time, the rotor speed is held constant at a low speed, which can be 50 Hz or lower, and is powered by the main power source to anticipate a subsequent exposure and / or to cool the rotatable assembly. The low rotation speed is shown on the first sub-plot 1102 by the horizontal segment of the first curve 1110. The amount of stored energy remains constant between T2 and T3, as shown by the horizontal segment of the second curve 1112 between T2 and T3. Between T2 and T3, the main power source provides a constant, low level of power current to the motor to maintain the lower rotatable assembly speed, as shown by the horizontal segment of the fourth curve 1116 between T2 and T3 in the fourth sub-plot 1108.

[0079] At T3, the power is cut and the main power source is no longer supplying power. Between T3 and T4, the energy stored in the energy storage circuit is used to power the motor to maintain the rotatable assembly speed at the threshold speed (e.g., the low speed). The process of using the stored energy to power the motor and the pump circuit is shown by the linear decrease in the second curve 1112 between T3 and T4. The constant power flowing from the energy storage circuit to the motor is shown as the horizontal segment of the fourth curve 1116 between T3 and T4. Additionally, at T3, the pump is forced to run in an on state using the energy stored in the energy storage circuit, which is shown by the horizontal portion of the third curve 1114 that does not include the fill pattern (e.g., the white / blank segment).

[0080] At T4, the energy stored in the energy storage circuit reaches a lower threshold, which can indicate that there is insufficient energy remaining in the energy storage circuit to power both the motor and the tube pump. Accordingly, the power from the energy storage circuit to the motor is terminated and the power supplied to the motor drops to 0 at T4. After T4, the rotatable assembly decelerates to a stop due to inertia since there is no stored energy to turn the rotatable assembly. The process of the rotatable assembly decelerating to a stop due to inertia is shown in the first sub-plot 1102 as an exponential decay of the rotatable assembly speed between T4 and T5.

[0081] At T5, the rotatable assembly speed equals zero, indicating that the rotatable assembly has stopped. After the rotatable assembly stops at T5, the pump is deactivated, as shown by the pump activity state represented by the third curve 1114 dropping to zero at T5. The pump remains active until the rotatable assembly speed drops to zero, in order to provide effective cooling throughout the process and to prevent hot landing by ensuring that the LMB temperature and the rotatable assembly temperature decrease after power is removed. Having the rotatable assembly spin at low speed for as long as possible helps to prevent hot landing by keeping the rotatable assembly and LMB in motion, thereby preventing mechanical contact and potential fusing between the shaft and the bushings within the rotatable assembly. As the tube pump continues to run between T4 and T5, the recovered energy stored in the tank circuit continues to decrease as the rotor decelerates to a stop by inertia, but at a slower rate than the rate of use of the recovered energy between T3 and T4, because the energy in the tank circuit is only used to power the tube pump between T4 and T5. The deceleration is shown in the second sub-plot 1104, specifically by the shallower slope of the second curve 1112 between T4 and T5 relative to the slope between T3 and T4.

[0082] Referring now to Figure 12A and Figure 12BThey show a method 1200 for controlling operation of an energy recovery storage distribution system (such as the energy storage circuit 342), a cooling pump (such as the tube pump 328), and a motor (such as the motor 321) according to a first energy recovery strategy to recover energy from the motor after each exposure and to consume stored energy during a motor ramp-up or during a power outage. The method 1200 can be performed according to instructions stored in a memory of one or more controllers or computing devices included as part of and / or operatively coupled to a CT imaging system, such as the CT system 300, the CT system 400, or the CT system 500. At 1202, the method 1200 can include operating an x-ray tube to perform an examination according to one or more scan parameters. The scan parameters can include a number of exposures to be performed during the examination, a duration of each exposure, a voltage and / or a current of the x-ray tube at each exposure, and / or other parameters. Operating the x-ray tube to perform the examination can include rotating a target of the x-ray tube with a motor and transferring heat generated by the exposure to an LMB of a rotatable assembly, as indicated at 1204. The target can be rotated so that heat energy generated by electrons striking the target is distributed over a focal track composed of multiple locations on the target as the target rotates, rather than a single focal spot. Additionally, heat is generated when the rotatable assembly turns due to friction and when the motor operates to drive rotation of the rotatable assembly. Operating the x-ray tube to perform the examination can also include operating a tube pump to cool the rotatable assembly and the LMB, as indicated at 1206. The tube pump can be a component of a coolant loop and directs coolant to flow through the coolant loop to be in thermal contact with the LMB and the rotatable assembly to absorb excess heat of the LMB and the rotatable assembly. The coolant can be circulated by the pump to a heat exchanger where the temperature of the coolant is reduced.

[0083] At 1208, the method 1200 can include identifying whether a power loss has occurred. Identifying whether a power loss has occurred can include identifying a loss of power from a main power source, such as by monitoring current through one or both of an inverter or other mechanism. For example, the main power source can stop supplying power in the event of a power outage or due to an operator turning off or unplugging the CT system. Since a power loss can be identified at any time during a scan, the power loss can be monitored throughout the scan. If a power loss is detected, the method 1200 proceeds to 1210, which is described in detail below; if a power loss is not detected, the method proceeds to 1230, which is included in the method 1200. The power loss can occur at any point in the method 1200, and if a power loss is identified at any point in the scan, the method 1200 can include proceeding to 1210 immediately from the point in the method 1200 at which the power loss was detected. Figure 12B

[0084] ​At 1230, the method can include determining whether the rotatable component is spinning at a high frequency, such as above 50 Hz. One or more sensors can be integrated into the motor to measure the rate of rotation of the rotatable component. If the rotatable component is not spinning at a high frequency, the method 1200 can include determining whether the rotatable component is commanded to ramp up to a higher speed at 1242. The rotatable component can be commanded to speed up in preparation for a subsequent exposure, or to match the speed of the rotatable component to the scan parameters initiated at 1202. If no command to ramp up to a higher speed is received, the method 1200 can continue to operate the x-ray tube to perform the examination at 1202. If a command to ramp up to a higher frequency is received, the method 1200 can continue at 1240, which includes using the stored energy to accelerate the rotatable component to the higher frequency. After each exposure, mechanical energy from the decelerating rotatable component is stored as electrical energy in an energy storage circuit (e.g., energy storage circuit 342), and the recovered energy can be used to power the motor to ramp up the rotational frequency of the rotatable component to the commanded frequency. Once the commanded frequency is reached, the method 1200 can continue at 1230.

[0085] If the rotatable component is spinning at a high frequency at 1230, the method 1200 can include evaluating whether the examination is terminated at 1232. The examination can be terminated based on a scan parameter indicating that the examination is complete (e.g., the examination can be performed according to a protocol, and the examination can be terminated in response to the protocol being complete), or the examination can be manually terminated by an operator (e.g., the operator can enter an input indicating that the examination is complete). If the examination is not terminated at 1232, the method 1200 can continue to operate the x-ray tube to perform the examination according to the scan parameters at 1202.

[0086] If the check at 1232 terminates, the method 1200 can include initiating an energy recovery sequence at 1234. The energy recovery sequence can include terminating power to the rotatable assembly (e.g., from the main power supply) to slow the speed of the rotatable assembly and convert the kinetic energy of the rotatable assembly into electrical energy by slowing the speed of the rotatable assembly and store the electrical energy in an energy storage circuit for future use. The energy recovery sequence can include monitoring the rotational frequency of the rotatable assembly and at 1236, the method 1200 can include determining whether the rotatable assembly is rotating at or below a low frequency threshold. The low frequency threshold can be a frequency at which a hot landing is not likely to occur when stopping the rotatable assembly, such as a frequency below 50 Hz. If the rotational frequency of the rotatable assembly does not reach the low frequency threshold at 1236, the method 1200 can include continuing the energy recovery sequence at 1234 until the frequency of the rotatable assembly reaches the low frequency threshold. If the rotatable assembly is rotating at or below the low frequency at 1236, the method 1200 can include determining whether a request to shut down the power to the CT system has been received at 1237. If no request to shut down the power to the CT system has been received at 1237, the CT system can remain in the operational state and be ready for a continuous scan by proceeding to 1202 of the method 1200. While the CT system is in the operational state and no check is in progress, the rotatable assembly can rotate at the low frequency (e.g., 50 Hz) until the next check is initiated. If a request to shut down the power to the CT system is received at 1237, the method 1200 can proceed to 1238. At 1238, the rotatable assembly is allowed to coast down to 0. Allowing the rotatable assembly to coast down can include shutting off power to the motor and allowing the rotational frequency of the rotatable assembly to decrease to zero. The pump can be deactivated when the temperature of the rotatable assembly and the LMB drops below a certain threshold, or after the rotatable assembly coasts down for a certain amount of time, or based on another set of criteria. Once the pump is deactivated and the rotatable assembly coasts down, the method can end. It is to be appreciated that the rotatable assembly is only allowed to coast down after the duration of time that the rotatable assembly is rotating at the low frequency allows the rotatable assembly and the LMB to cool down, and power to the motor is terminated once the duration of time has passed. Further, in some examples, a new check can be initiated before the rotatable assembly coasts down, in which case the method 1200 can loop back to 1202 to operate the x-ray tube to perform the next check again.

[0087] Returning to 1208 of the method 1200, Figure 12A if a power outage is detected at 1208, the method 1200 can include using the energy stored in an energy storage circuit (such as the energy storage circuit 342 of the system 300) and Figure 3 the energy storage circuit 342 of the system 300) and Figure 6 the energy storage circuit 342 of the system 300) and Figure 7part of the energy in the capacitor bank 604 activates the pump (e.g., tube pump 328). The stored energy can be collected and stored as the rotatable assembly ramps down during a previous exposure. The pump pumps cooling fluid to cool the LMB and rotatable assembly, so power is preferentially provided to the pump to prevent overheating or hot landing. At 1212, the method can include determining whether the rotatable assembly is rotating at a high frequency (e.g., above 50 Hz, which in some examples can include a high frequency of 180 Hz or 145 Hz as described above). If the rotatable assembly is rotating at a high frequency, the method 1200 can include initiating an energy recovery sequence at 1214. The energy recovery sequence can be similar to the energy recovery sequence described above, and can include converting the kinetic energy of the rotatable assembly into electrical energy that can be stored in the energy storage circuit 342 as the rotatable assembly slows down. If the rotatable assembly is not rotating at a high frequency at 1212, the method can proceed to 1216. At 1216, the method includes rotating the rotatable assembly at a low frequency (such as a low frequency of 50 Hz) using the energy stored in the energy storage circuit. Continuing to rotate the rotatable assembly at a low frequency with the pump powered on can prevent hot landing by keeping the liquid metal moving within the LMB, while cooling the LMB through the coolant loop to prevent the bearing sleeve of the rotatable assembly from fusing with the stationary shaft.

[0088] At 1218, the method can include evaluating whether the rotatable assembly temperature is below a threshold temperature. Hot landing is more likely to occur when the rotatable assembly temperature is high, and less likely to occur when the rotatable assembly temperature is low. The threshold temperature can represent some sufficiently low temperature at which the rotatable assembly is unlikely to cause a hot landing. If the rotatable assembly temperature is below the threshold temperature, the method 1200 can include terminating power to the motor at 1220 and allowing the rotatable assembly to coast down. Terminating power to the motor can include terminating power to the stator that rotates the rotatable assembly, and allowing the rotatable assembly to slow down to a stop under the influence of friction. The pump can remain active while the rotatable assembly coasts down, to provide active cooling to the rotatable assembly and LMB. At 1222, once the rotatable assembly stops, the pump can be deactivated, and the method ends.

[0089] However, if the rotatable assembly temperature is greater than the threshold temperature at 1218, the method 1200 can proceed to 1224. At 1224, the method can include evaluating whether the remaining stored energy in the energy storage circuit is less than an energy threshold. The energy threshold can represent an amount of energy required for the pump to run during the amount of time required for the rotatable assembly to coast down to a stop. If the remaining stored energy is greater than the energy threshold, the method 1200 can proceed to 1216 to continue to turn the rotatable assembly at the low frequency using the stored energy in the energy storage circuit. If the remaining stored energy is less than the threshold energy, the method can include terminating power to the motor at 1226 and allowing the rotatable assembly to coast down to a stop. During the coast down of the rotatable assembly, power is still supplied to the pump in order to provide active cooling during the coast down. At 1228, the method 1200 can include supplying power to the pump for as long as possible until the stored energy in the energy storage circuit is depleted. Running the pump for as long as possible with the remaining stored energy can maximize the ability of the system to cool the rotatable assembly and prevent hot landings. The method 1200 then ends.

[0090] Thus, the method 1200 provides for X-ray tube operation according to a first energy recovery strategy that includes recovering energy from the rotatable assembly after each exposure and storing the energy in an energy storage circuit for reuse the next time the rotatable assembly ramps up or a power loss occurs. In the event of a power outage, the energy stored in the energy storage circuit can be used to keep the rotatable assembly turning at 50 Hz or lower. This approach achieves a "tube peak power demand savings" by storing energy during the ramp down of the rotatable assembly and reusing the energy during the ramp up, greatly reducing the extra power required for acceleration, thereby saving extra energy and reducing the electrical stress and electromagnetic interference / compatibility generated to the X-ray tube and associated components of the power chain subsystem.

[0091] As previously mentioned, the CT system described herein can operate according to a second energy recovery strategy that includes recovering energy from the rotatable assembly after each exposure and storing the energy in an energy storage circuit for reuse the next time the rotatable assembly ramps up or a power loss occurs. In the event of a power outage, the energy stored in the energy storage circuit can be used to keep the rotatable assembly turning at 50 Hz or lower. This approach achieves a "tube peak power demand savings" by storing energy during the ramp down of the rotatable assembly and reusing the energy during the ramp up, greatly reducing the extra power required for acceleration, thereby saving extra energy and reducing the electrical stress and electromagnetic interference / compatibility generated to the X-ray tube and associated components of the power chain subsystem. Figure 13 and Figure 14 are illustrated in the flowcharts of Figure 15A and Figure 15B . Figure 13The time-domain graph 1300 illustrates rotatable assembly speed, recovered stored energy, pump operation, and power to the motor for 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 and energy recovery is performed according to a second energy recovery strategy. The second energy recovery strategy can involve recovering energy only during a power loss. The first sub-graph 1302 includes a first curve 1310 representing rotatable assembly speed (e.g., of rotatable assembly 327) as a function of time; the second sub-graph 1304 includes a second curve 1312 representing the amount of energy recovered from the rotatable assembly and stored in, and depleted from, an energy recovery storage and distribution system (e.g., energy storage circuit 342) by the energy recovery storage and distribution system; the third sub-graph 1306 includes a third curve 1314 representing the active state of a tube pump (e.g., tube pump 328) as a function of time; and the fourth sub-graph 1308 includes a fourth curve 1316 representing the amount of power directed to the motor from the main power source (shown by the dashed portion of the fourth curve 1316) and from the energy recovery storage and distribution system (shown by the solid portion of the fourth curve 1316). The first, second, and fourth sub-graphs 1302, 1304, and 1308 each include respective values (e.g., of rotatable assembly speed, energy, and power flow) that increase along the y-axis, and the third sub-graph 1306 illustrates pump operation in binary (on / off) form. The sub-graphs are synchronized in time, and a time point of interest is marked with a dashed line.

[0092] Prior to T1, the x-ray exposure has ended, and the rotatable assembly speed decreases over time, as shown by the portion of the first curve 1310 that decreases over time prior to T1. The rotatable assembly speed can reach a predetermined low frequency, such as, for example, 50 Hz at T1. As shown by the negative slope segment of the fourth curve 1316, power to the motor can be supplied at a decreasing rate prior to T1 to drive the rotatable assembly to rotate at a lower frequency over time. As shown by the flat segment of the fourth curve 1316, at T1, the power to the motor is maintained at a lower level to maintain the low frequency rotation of the rotatable assembly. There is no energy recovery during the ramp-down process described above, so the second curve 1312 remains at zero around T1. The tube pump remains in an on state throughout the process in order to cool the x-ray tube. The tube pump is controlled according to a cooling strategy required by the first pump system 410 (as indicated by the third curve 1314 via hatching that the pump is being controlled by the first pump system 410), and the power to the motor comes from a connection to a main power source such as a power grid, as shown by the dashed line of the fourth curve 1316.

[0093] As previously described, the second energy recovery strategy recovers energy from the rotatable assembly only in response to a loss of power from the primary power source. If a loss of power occurs while the rotatable assembly is rotating at a high frequency during an exposure, enough energy can be recovered to power the rotatable assembly at a low frequency and operate the pump to cool the rotatable assembly and the LMB, avoiding a hot landing. Thus, the energy recovery and distribution after a loss of power during an exposure is performed in the same manner as in the first energy recovery strategy in the second energy recovery strategy. However, since energy is not recovered from the rotatable assembly after each exposure, the amount of energy stored in the energy storage circuit can be zero at any given time. Thus, if a loss of power occurs after an exposure while the rotatable assembly is slowing down or the rotatable assembly is operating at a low frequency, there can not be enough energy to continue operating the rotatable assembly and the pump. Thus, according to the second energy recovery strategy, the ramp down of the rotatable assembly after an exposure can be much slower than in the first energy recovery strategy, with the rotatable assembly maintaining a rotational speed sufficient to provide energy to avoid a hot landing in the event of a loss of power. In some examples, the speed of the rotatable assembly can be adjusted during the ramp down after an exposure based on the temperature of the LMB.

[0094] Figure 14 The time-domain graph 1400 illustrates the rotatable assembly speed, recovered stored energy, pump operation, and power to the motor in the CT system of Figure 13 The first sub-graph 1402 includes a first curve 1410 representing the rotatable assembly speed over time; the second sub-graph 1404 includes a second curve 1412 representing the amount of energy recovered from the rotatable assembly by the energy recovery storage and distribution system and stored in and depleted from the energy recovery storage and distribution system; the third sub-graph 1406 includes a third curve 1414 representing the activity state of the tube pump over time; and the fourth sub-graph 1408 includes a fourth curve 1416 representing the amount of power directed to the motor from the primary power source (shown by the dashed portion of the fourth curve 1416) and the energy recovery storage and distribution system (shown by the solid portion of the fourth curve 1416). The first, second, and fourth sub-graphs 1402, 1404, and 1408 each include respective values (e.g., values of rotatable assembly speed, energy, and power flow) increasing along the y-axis, and the third sub-graph 1406 illustrates the pump operation in binary (on / off) form. The sub-graphs are synchronized in time, and the time points of interest are marked with dashed lines.

[0095] Before T1, the rotatable assembly ramps down after the X-ray exposure terminates. The rotatable assembly rotates at a decreasing frequency, represented by the negative slope segment of the first curve 1410 before T1. There is no energy recovery, as shown by the horizontal segment of the second curve 1412 before T1, and the amount of power flowing to the motor decreases, causing the rotatable assembly to rotate at a decreasing velocity, as shown by the negative slope of the fourth curve 1416 before T1. The tube pump is activated, as shown by the constant hatching portion of the third curve 1414 before T1, to cool the X-ray tube. The tube pump is controlled according to the cooling strategy required by the first pump system 410 (as shown by the third curve 1414, which indicates via hatching that the pump is being controlled by the first pump system 410), and the power flowing to the motor comes from a connection to a main power source such as the power grid, as shown by the dashed line of the fourth curve 1416.

[0096] At T1, the power outage occurs, and the energy recovery process begins. The rotatable assembly decelerates to a low frequency, such as 50 Hz, as shown by the negative slope segment of the first curve 1410 between T1 and T2. The mechanical energy recovered from the decelerating rotatable assembly is converted to electrical energy and stored in the energy storage circuit, as shown by the positive slope segment of the second curve 1412 between T2 and T1. At T1 (or as soon as there is enough energy in the energy storage circuit), the pump power source changes, and the activity of the pump is powered by the energy storage circuit. The change in power source is represented by the portion of the third curve 1414 after T1 that does not include the fill pattern. In at least some examples, the activity of the pump remains constant, and there is no loss of functionality of the pump during the power outage. The recovered energy is represented by the negative portion of the fourth curve 1416 between T1 and T2.

[0097] After T2, the rotatable assembly rotates at a low frequency, and the pump is run by the energy stored in the energy storage circuit between T1 and T2. During this time, the amount of energy in the energy storage circuit decreases, as shown by the decreasing segment of the second curve 1412 between T2 and T3 in the second sub-plot 1404, which can be linear. The amount of power used to rotate the rotatable assembly is shown as the horizontal segment of the fourth curve 1416 between T2 and T4.

[0098] At T3, the energy in the tank reaches a lower threshold, which can indicate that there is insufficient energy remaining in the tank to power both the motor and the tube pump simultaneously. Accordingly, the power supplied to the motor from the tank is terminated, and the power supplied to the motor drops to 0 at T3. At T3, no more power is supplied to the rotation of the rotatable assembly, and the speed of the rotatable assembly ramps down, as shown by the decreasing segment of the first curve 1410 between T3 and T4 in the first sub-plot 1402. Because the tank only supplies power to the tube pump between T3 and T4, the rate of energy consumption in the tank is lower between T3 and T4 relative to between T2 and T3. At T4, the rotatable assembly speed reaches 0. The pump remains active until the rotatable assembly speed reaches 0.

[0099] Referring now to Figure 15A and Figure 15B which illustrate a method 1500 for controlling operation of an energy recovery storage distribution system (such as the tank 342), a cooling pump (such as the tube pump 328), and a motor (such as the motor 321) to recover energy from the motor after a power outage. The method 1500 can be performed in accordance with instructions stored in a memory of one or more controllers or computing devices included as part of and / or operatively coupled to a CT imaging system, such as the CT system 300, the CT system 400, or the CT system 500. At 1502, the method 1500 can include operating an x-ray tube to perform an examination in accordance with scan parameters. The scan parameters can include a number of exposures to be performed during the examination, a duration of each exposure, a voltage and / or a current of the x-ray tube at each exposure, and / or other parameters. Operating the x-ray tube to perform the examination can include rotating a target of the x-ray tube with a rotatable assembly and transferring heat generated by the exposures to an LMB of the rotatable assembly, as indicated at 1504. The target can be rotated so that heat energy generated by electrons striking the target is distributed across a focal band of multiple locations on the target as the target rotates, rather than a single focal point, during the exposures. Additionally, heat is generated when the rotatable assembly spins due to friction and when the motor operates to drive rotation of the rotatable assembly. Operating the x-ray tube to perform the examination can also include operating a pump to cool the rotatable assembly and the LMB, as indicated at 1506. The pump can be a component of a coolant loop and directs a coolant to flow through the coolant loop to be in thermal contact with the LMB and the rotatable assembly to absorb excess heat of the LMB and the rotatable assembly. The coolant can be circulated by the pump to a heat exchanger, where the temperature of the coolant is reduced.

[0100] At 1508, the method 1500 can include identifying whether a power loss has occurred. Identifying whether a power loss has occurred can include identifying a loss of power from a main power source, such as via monitoring current through one or both of an inverter or other mechanism. For example, the main power source can stop supplying power in the event of a power outage or due to an operator shutting down the CT system. Since a power loss can be identified at any time during a scan, the power loss can be monitored throughout the scan. If a power loss is detected, the method 1500 proceeds to 1509, which will be described in detail below; if a power loss is not detected, the method proceeds to 1528, which is included in Figure 15B The power loss can occur at any point in the method 1500, and if a power loss is identified at any point in the scan, the method 1500 can include proceeding to 1509 immediately from the point in the method 1500 at which the power loss was detected.

[0101] At 1528, the method 1500 can include determining whether an exposure has been requested. The exposure request can be entered by a medical service provider, or the exposure request can come from a controller integrated into the CT system. If an exposure has not been requested, the method 1500 continues at 1546; if an exposure has been requested, the method 1500 continues at 1530, which will be described in detail below. At 1546, the method 1500 can include determining whether the rotation of the rotatable assembly exceeds a low frequency threshold. As previously described, the low frequency threshold can be 50 Hz. If the frequency of rotation of the rotatable assembly does not exceed the low frequency at 1546, the method 1500 continues at 1542. If the frequency of rotation of the rotatable assembly is above the low frequency at 1546, the temperature and energy of the rotatable assembly can be evaluated at 1548. The evaluation can be done by temperature and frequency sensors coupled to the rotatable assembly. At 1550, the energy of the rotatable assembly is evaluated to determine whether enough energy can be recovered to cool the rotatable assembly if a power outage occurs. If there is enough energy at 1550, the method 1500 can include proceeding to 1542, which will be described in detail below. If there is not enough energy at 1550, the method can include accelerating the rotatable assembly at 1552. Accelerating the rotatable assembly can include issuing a command to a power source coupled to a motor, such as the RCB 338. The rotatable assembly can be accelerated to a new set frequency, which can be calculated based on the temperature of the rotatable assembly. The method 1500 can proceed from 1552 to 1548 to determine whether the rotatable assembly has been accelerated to an appropriate speed.

[0102] Returning to 1528, if an exposure request is detected, the method 1500 proceeds to 1530, which can include predicting a temperature of a target after an exposure occurs. The target can be an anode within an x-ray tube and can be coupled to / included as part of a rotatable assembly. When an x-ray exposure occurs, electrons impact the target, generating x-rays and heat. The temperature change of the target can be predicted based on a variety of factors, including a duration of the x-ray exposure, an intensity of an x-ray beam impacting the target (which can be based on a current of the x-ray tube), an efficiency of a coolant loop coupled to the rotatable assembly, and a current temperature of the rotatable assembly and the target.

[0103] At 1532, the method can include calculating an amount of energy specified to be needed to rotate the rotatable assembly at a low frequency in the event of a loss of power. The calculation can be based on a time needed to cool the rotatable assembly from a current temperature to a temperature at which a risk of hot landing is low, and an amount of energy to power a tube pump while the rotatable assembly is cooling. At 1534, the method 1500 can include determining a rotatable assembly speed needed to recover the amount of energy calculated at 1532 if a loss of power occurs. Determining the rotatable assembly speed can include calculating an energy loss between the rotatable assembly and an energy storage circuit, and an amount of kinetic energy the rotatable assembly has according to a rotational speed of the rotatable assembly.

[0104] At 1536, the method can include determining whether the determined rotatable assembly speed is greater than a maximum rotatable assembly speed. The maximum rotatable assembly speed can be based on limitations of the motor and limitations of the target. If the determined rotatable assembly speed is less than or equal to the maximum rotatable assembly speed, the method 1500 can include rotating the rotatable assembly at the determined speed at 1554. The method 1500 can continue from 1554 to 1540. If the determined rotatable assembly speed is greater than the maximum rotatable assembly speed at 1536, the method 1500 can include rotating the rotatable assembly at the maximum rotatable assembly speed at 1538, and then proceed to 1540.

[0105] At 1540, the method can include performing an exposure. The exposure can include the x-ray generator powering the x-ray tube to accelerate an electron beam toward a rotating target. The electrons can generate x-rays when they impact the target, which can be directed through a subject and detected by a detector to image the subject. In a CT system such as the CT system 400 described in connection with Figure 4 In the CT system 400 described in connection with, the x-ray generator and the x-ray tube can be integrated into a rotating gantry, and the x-ray generator, the x-ray tube, the x-ray detector, and associated power electronics can rotate during an exposure. Performing an exposure can also include, after the exposure ends, powering the motor to rotate the rotatable assembly at a rate to ensure that, in the event of a loss of power, enough energy can be recovered to rotate the rotatable assembly at a low frequency and operate the pump. As described in connection with Figure 13As shown, after exposure, instead of stopping power supply to the motor to ramp down the rotatable component to a low frequency, the rotatable component can be gradually decelerated at a certain rate based on, for example, the temperature of the LMB, so that in the event of power loss, sufficient energy can be recovered by rotating the rotatable component and operating the pump to cool the LMB. The process of ramping down the speed of the rotatable component can be performed similarly to the process described in conjunction with steps 1548, 1550, and 1552 of method 1500 above. At 1542, method 1500 may include determining whether the examination has been terminated (e.g., ended). If all exposures have been performed on the subject, the examination may be terminated / ended. If the examination has not been terminated at 1542, method 1500 may continue at 1502. The method may continue from 1502 as described above. If the examination has been terminated at 1542, method 1500 may include determining at 1543 whether a request to shut down the CT system power has been received. If no request to shut down the CT system power is received at 1543, the CT system may remain operational and ready to proceed to 1502 for continuous scanning via method 1500. If a request to shut down the CT system power is received at 1543, method 1500 may proceed to 1544. At 1544, method 1500 may include rotating the rotatable assembly and operating the pump until indicated, then allowing the rotatable assembly to decelerate inertially and stopping the pump. If the rotatable assembly temperature has reached a low temperature threshold, and if a thermal landing is unlikely if the rotatable assembly decelerates inertially at its current temperature, the rotatable assembly and pump may be instructed to stop. Decelerating the rotatable assembly inertially may include reducing the speed of the rotatable assembly over time until it stops, and this can be achieved by no longer supplying power to the motor. It should be understood that after an inspection terminates, if a new inspection begins, method 1500 may cycle back to 1502 to initiate the next inspection; in some examples, this may occur without the rotatable assembly having completely stopped.

[0106] Back Figure 15A If a power loss is detected at 1508, method 1500 may include activating a tubular pump at 1509 using recovered / stored energy, which may be stored in an energy storage circuit, such as... Figure 3At 1510, the method 1500 includes initiating energy recovery of the rotatable assembly. If the power loss occurs during exposure or during the ramp down of the rotatable assembly after exposure, energy can be recovered from the rotatable assembly as it slows to a low frequency threshold. At 1512, the method can include powering the motor using the stored energy in the energy storage circuit to rotate the rotatable assembly at a low frequency, such as 50 Hz. At 1514, the method can include determining whether the rotatable assembly temperature is below a threshold temperature. The threshold temperature can be a temperature at which the risk of hot landing is low. If the rotatable assembly temperature is less than the threshold temperature, the method 1500 can include terminating power to the motor at 1516 and allowing the rotatable assembly to coast down. Terminating power to the motor can include terminating power to the stator that rotates the rotatable assembly and allowing the rotatable assembly to slow to a stop under the influence of friction. While the rotatable assembly is coasting down, the pump can remain active to provide active cooling to the rotatable assembly and the LMB. At 1518, once the rotatable assembly stops, the pump can be deactivated and the method ends.

[0107] If at 1514, the rotatable assembly temperature is greater than or equal to the threshold temperature, the method 1500 can include determining whether the remaining stored energy in the energy storage circuit is less than an energy threshold at 1520. The energy threshold can represent the amount of energy required for the pump to operate for the amount of time required for the rotatable assembly to coast to a stop. If the remaining stored energy is greater than the energy threshold, the method 1500 can proceed to 1522 to continue rotating the rotatable 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 can include terminating power to the motor at 1522 and allowing the rotatable assembly to coast to a stop. During the coasting of the rotatable assembly, the pump is still powered to provide active cooling during the coasting. At 1524, the method 1500 can include powering the pump for as long as possible until the stored energy is depleted. Operating the pump for as long as possible with the remaining stored energy can maximize the ability of the system to cool the rotatable assembly and prevent hot landing.

[0108] The technical effect of the disclosed self-sufficient hot landing protection system is that energy is recovered from the rotatable assembly as it slows down and stored for use to power the motor and the pump in the event of a power loss, thereby preventing hot landing. The motor can be powered to maintain the rotatable assembly rotating at a low speed and the pump can be powered on to cool the rotatable assembly. Rotating the rotatable assembly at a low speed and cooling the rotatable assembly using the stored recovered energy can prevent the rotatable assembly from stopping suddenly at a high temperature, which can cause the shaft sleeve to fuse with the shaft within the rotatable assembly, which can be referred to as hot landing. Additionally, recovering energy from the rotatable assembly facilitates energy savings and reduces the amount of power required from an external source to operate the motor.

[0109] Although computed tomography (CT) systems are described by way of example, it will be appreciated that the present techniques can 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 interventional systems, X-ray C-arm systems, etc. The current discussion of CT imaging modalities is provided merely as an example of a suitable imaging modality.

[0110] The present disclosure also provides support for a method for an x-ray tube of an imaging system, the method comprising: supplying energy from a main power source to the x-ray tube to rotate a target of the x-ray tube during a scan of a subject using 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 main power source 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, supplying energy from the main power source to the x-ray tube to rotate the target of the x-ray tube comprises supplying energy from the main power source to a motor coupled to the target. In a second example of the method, optionally including the first example, selectively recovering energy from the x-ray tube comprises recovering energy from the motor in response to detecting the loss of the main power source. In a third example of the method, optionally including one or both of the first example and the second example, selectively recovering energy from the x-ray tube comprises recovering energy from the motor during a ramp down of the motor after termination of a first exposure using 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 comprises supplying energy from the main power source to the x-ray tube to rotate the target at a run speed, the run speed being higher than the threshold speed, wherein during the ramp down, no energy is supplied from the main power source 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 comprises: receiving a request to initiate a second exposure using the x-ray tube; and in response, supplying energy from the energy storage circuit to the motor to rotate the target to the run speed. In a sixth example of the method, optionally including one or more or each of the first through fifth examples, the method further comprises: 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. In a seventh example of the method, optionally including one or more or each of the first through sixth examples, the method further comprises: 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 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 comprises: supplying energy from the energy storage circuit to the pump until the target stops rotating, and then terminating the supply of energy to the pump.

[0111] The present disclosure also provides support for a computed tomography (CT) imaging system, including: an x-ray tube including a rotatable assembly including a target and a rotor of a motor; a tank circuit coupled to the motor; a memory storing instructions; and one or more processors configured to execute the instructions to: in response to a loss of a main power supply to the motor, convert rotational kinetic energy of the rotatable assembly to electrical energy as the rotatable assembly rotates after the loss of the main power supply, the electrical energy being stored in the tank circuit; and supply the electrical energy stored in the tank circuit to the motor to continue rotating the rotatable assembly at a threshold speed for a period of time. In a first example of the system, the system further includes: a coolant loop including a pump configured to supply coolant to the motor, and wherein the one or more processors are configured to execute the instructions to, in response to the loss of the main power supply, supply the electrical energy from the tank circuit to the pump. In a second example of the system, optionally including the first example, the one or more processors are configured to execute the instructions to, after the period of time, terminate the supply of the electrical energy from the tank circuit to the motor and continue the supply of the electrical energy from the tank circuit to the pump until the rotatable assembly stops rotating, and then terminate the supply of the electrical energy to the pump. In a third example of the system, optionally including one or both of the first and second examples, the period of time is based on a temperature of the motor and / or an amount of energy stored in the tank 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 the main power supply to the motor via a power path that bypasses the tank circuit. In a fifth example of the 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, in response to the loss of the main power supply, supply electrical energy to a detector system of the CT imaging system and / or one or more off-rack devices of the CT imaging system.

[0112] 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 coupled to the target and a liquid metal bearing (LMB), a shaft of the target, rotor, and LMB forming a rotatable assembly, a tank circuit coupled to the motor, a coolant loop coupled to the motor and including a pump, a memory storing instructions, and one or more processors configured to execute the instructions to: during a first exposure, supply electrical energy from a main power source to the motor to cause the rotatable assembly to rotate at an operating speed, and in response to termination of the first exposure, supply electrical energy from the main power source to the pump to cool the motor, convert rotational kinetic energy of the rotatable assembly to electrical energy as the rotatable assembly continues to rotate after termination of the first exposure, the electrical energy being stored in the tank circuit, and in response to initiation of a second exposure, supply the electrical energy stored in the tank circuit to the motor to increase a rotational speed of the rotatable assembly to the operating speed. In a first example of the system, the one or more processors are further configured to execute the instructions to, in response to a loss of the main power source to the motor during the second exposure: supply electrical energy from the tank circuit to the pump, convert rotational kinetic energy of the rotatable assembly to electrical energy as the rotatable assembly continues to rotate after the loss of the main power source, the electrical energy being stored in the tank circuit, and once the speed of the rotatable assembly reaches a lower threshold speed, supply the electrical energy stored in the tank circuit to the motor to maintain the speed of the rotatable assembly at the lower threshold speed. In a second example of the system, optionally including the first example, the one or more processors are further configured to execute the instructions to supply electrical energy from the main power source to the motor to rotate the rotatable assembly at a lower threshold speed during a period between the first exposure and the second exposure. In a third example of the system, optionally including one or both of the first example and the second example, the one or more processors are configured to execute the instructions to, after a duration of time, terminate the supply of electrical energy from the tank circuit to the motor and continue the supply of electrical energy from the tank circuit to the pump until the rotatable assembly stops rotating, and then terminate the supply of electrical energy to the pump. In a fourth example of the system, optionally including one or more or each of the first through third examples, the duration of time is based on a temperature of the motor and / or an amount of energy stored in the tank circuit.

[0113] When introducing elements of various embodiments of the disclosure, the articles "a," "an," and "the" are intended to mean that there are one or more of the elements. The terms "first," "second," and the like do not denote any order, quantity, or importance, but are used to distinguish one element from another. The terms "include" and "comprise" and "have" are intended to be inclusive and permitting of the presence of additional elements. As the term "connected" or "coupled" is used herein, one object (e.g., material, element, structure, member, etc.) can be connected or coupled to or with another object, regardless of whether it is directly connected or coupled to the other object, or there is one or more intervening objects between the one object and the other object. Also, it will be understood that a reference to "one embodiment" or "an embodiment" of the present disclosure is not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the referenced features.

[0114] In addition to any prior indicated modifications, numerous variations and alternative arrangements can be designed by those of ordinary skill in the art without departing from the spirit and scope of the description, and it is intended that the appended claims cover such modifications and arrangements. Therefore, although the description has been described in detail and with reference to specific embodiments thereof, it will be apparent to those of ordinary skill in the art that numerous modifications can be made, including but not limited to, form, function, manner of operation and use, without departing from the principles and concepts set forth herein. Also, as used in the description, the examples and embodiments are intended merely to be illustrative and are not intended to be limiting in any way.

Claims

1. A method for an x-ray tube (316) of an imaging system (300), the method comprising: supplying energy from a main power source (602) to the x-ray tube (316) to rotate a target (319) of the x-ray tube (316) during a scan of a subject using the imaging system (300); selectively recovering energy from the x-ray tube (316) and storing the recovered energy in an energy storage circuit (342) of the imaging system (300); and detecting a loss of the main power source (602) and, in response, supplying energy from the energy storage circuit (342) to the x-ray tube (316) to rotate the target (319) at a threshold speed.

2. The method of claim 1, wherein supplying energy from the main power source (602) to the x-ray tube (316) to rotate the target (319) of the x-ray tube (316) comprises supplying energy from the main power source (602) to a motor (321) coupled to the target (319).

3. The method of claim 2, wherein selectively recovering energy from the x-ray tube (316) comprises recovering energy from the motor (321) in response to detecting the loss of the main power source (602).

4. The method of claim 2, wherein selectively recovering energy from the x-ray tube (316) comprises recovering energy from the motor (321) during a ramp down of the motor (321) after termination of a first exposure using the x-ray tube (316).

5. The method of claim 4, wherein the first exposure comprises supplying energy from the main power source (602) to the x-ray tube (316) to rotate the target (319) at a run speed, the run speed being higher than the threshold speed, and wherein during the ramp down, no energy is supplied from the main power source (602) to the motor (321). receiving a request to initiate a second exposure using the x-ray tube (316); and 6. The method of claim 5, further comprising: in response, supplying energy from the energy storage circuit (342) to the motor (321) to rotate the target (319) to the run speed. in response to detecting the loss of the main power source (602), supplying energy from the energy storage circuit (342) to a pump (328) configured to supply coolant to the x-ray tube (316).

7. The method of claim 1, further comprising: supplying energy from the energy storage circuit (342) to the x-ray tube (316) to rotate the target (319) at the threshold speed until a temperature of the x-ray tube (316) reaches a threshold temperature or until an amount of energy stored in the energy storage circuit (342) reaches a threshold energy, and then terminating the supply of energy to the x-ray tube (316).

8. The method of claim 7, further comprising: supplying energy from the energy storage circuit (342) to the pump (328) until the target (319) stops rotating, and then terminating the supply of energy to the pump (328).

9. The method of claim 8, further comprising: ​ 10. A computed tomography (CT) imaging system (300), the computed tomography imaging system comprising: an x-ray tube (300) including a rotatable assembly (327) including a target (319) and a rotor (318) of a motor (321); a tank circuit (342) coupled to the motor (321); a memory storing instructions; and one or more processors configured to execute the instructions to: in response to a loss of a primary power source (602) to the motor (321), convert rotational kinetic energy of the rotatable assembly (327) to electrical energy as the rotatable assembly (327) rotates after the loss of the primary power source (602), the electrical energy stored in the tank circuit (342); and supply the electrical energy stored in the tank circuit (342) to the motor (321) to continue rotating the rotatable assembly (327) at a threshold speed for a period of time.

11. The CT imaging system (300) of claim 10, further comprising: a coolant loop (344) including a pump (328) configured to supply coolant to the motor (321), and wherein the one or more processors are configured to execute the instructions to, in response to the loss of the primary power source (602), supply the electrical energy from the tank circuit (342) to the pump (328).

12. The CT imaging system (300) of claim 11, wherein the one or more processors are configured to execute the instructions to, after the period of time, terminate the supply of the electrical energy from the tank circuit (342) to the motor (321) and continue the supply of the electrical energy from the tank circuit (342) to the pump (328) until the rotatable assembly (327) stops rotating and then terminate the supply of the electrical energy to the pump (328).

13. The CT imaging system (300) of claim 12, wherein the period of time is based on a temperature of the motor (321) and / or an amount of energy stored in the tank circuit (342).

14. The CT imaging system (300) of claim 10, further comprising: a power distribution unit (302) configured to supply electrical energy from the primary power source (602) to the motor (321) via a power path (406, 408) that bypasses the tank circuit (342).

15. The CT imaging system (300) of claim 14, further comprising: an uninterruptible power supply (404) coupled to the power distribution unit (302) and configured to, in response to the loss of the primary power source (602), supply electrical energy to a detector system (348) of the CT imaging system and / or one or more off-rack devices (346) of the CT imaging system (300).

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