The subject matter disclosed herein relates generally to apparatus and methods for cooling of an MRI system, such as during powered off periods of the MRI system.
For cryogenically cooled MR magnets, helium used for cooling the magnets may evaporate when a system including the MR magnets is powered off. For example, the system may be powered off for transportation from one location to a different location. When the system is powered off, the helium may warm and vaporize, resulting in loss of helium.
In one example embodiment, a thermal management system is provided that includes a cold-head cryocooler and a cooling jacket. The cold-head cryocooler is configured to be operably coupled to a helium vessel of an MRI system, and is configured to cool at least one of superconducting magnet coils or a thermal shield of the MRI system. The cooling jacket has an outer surface defining a sleeve exterior, and includes a pathway disposed radially internally of the sleeve exterior defined by the cooling jacket. The cooling jacket is configured to receive boil-off gas from the helium vessel to be circulated through the pathway to cool the cold-head cryocooler.
In another example embodiment, a method is provided that includes coupling a cold-head cryocooler configured to a helium vessel of an MRI system. The cold-head cryocooler is configured to cool at least one of superconducting magnets or a thermal shield of the MRI system. The method also includes providing a cooling jacket disposed about at least a portion of the cold-head cryocooler. The cooling jacket has an outer surface defining a sleeve exterior, and includes a pathway disposed radially internally of the exterior defined by the cooling jacket. The cooling jacket is configured to receive boil-off gas from the helium vessel to be circulated through the pathway to cool the cold-head cryocooler.
In another example embodiment, a thermal management system is provided that includes a cold-head cryocooler and a cooling member. The cold-head cryocooler is configured to be operably coupled to a helium vessel of an MRI system, and is configured to cool at least one of superconducting magnets or a thermal shield of the MRI system. The cooling member is coupled to the cold-head cryocooler and includes a pathway configured to receive boil-off gas from the helium vessel to be circulated through the pathway to cool the cold-head cryocooler. The pathway includes an interior cross-section.
The following detailed description of certain embodiments will be better understood when read in conjunction with the appended drawings. To the extent that the figures illustrate diagrams of the functional blocks of various embodiments, the functional blocks are not necessarily indicative of the division between hardware. It should be understood that the various embodiments are not limited to the arrangements and instrumentality shown in the drawings.
As used herein, an element or step recited in the singular and preceded with the word “a” or “an” should be understood as not excluding plural of said elements or steps, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” of are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising” or “having” an element or a plurality of elements having a particular property may include additional elements not having that property.
Various embodiments provide systems and methods for improving cooling of MRI systems and/or reducing helium loss during the power off situation of the cold head cryocooler such as MRI system transportation or cold head malfunctioning. Various embodiments provide use of a cold head sleeve having a passageway for boil-off gas to improve operation of a cold-head cryocooler. Various embodiments utilize traditional manufacturing such as welding and brazing or non-conventional manufacturing such as additive manufacturing to provide a heat exchanger cross-section for a cold head sleeve (or other passageway, such as an outer tube). In various embodiments, boil-off gas is used to cool a cold head sleeve (e.g., first stage of a cold head sleeve) using a heat exchanger on the sleeve body. Additionally or alternatively, various embodiments utilize insulation around portions of a cold head cryocooler extending beyond a housing. Various embodiments receive boil-off gas from a helium vessel to be circulated through a pathway to cool a cold-head cryocooler and associated cryocooler sleeve by intercepting the heat from outside, which can result in reduced helium lost.
A technical embodiment of various embodiments includes improved cooling of MRI systems (e.g., during powered off conditions). A technical embodiment of various embodiments includes reduced helium loss during powered off conditions, and reduced cost to refill helium in a helium vessel.
In various embodiments, the coils on superconducting magnets of the MRI system 102 are cryogenically cooled using the helium vessel 104. During operation of the cold-head cryocooler 110, the cold-head cryocooler 110 (which may be disposed within a sleeve) functions to recondense vaporized cryogen to continually cool the superconducting magnet coils and/or thermal shield 103 of the MRI system 102. For example, the vaporized cryogen may be supplied to a recondenser 116 via a conduit 118. During the use of the cold-head cryocooler 110, a cold head sleeve 111 acts as a vacuum barrier between a vacuum chamber and external environment to preserve a vacuum seal. A housing 117 in the illustrated embodiment is disposed about a portion of the cold-head cryocooler 110 and cooperates with the cold head sleeve 111 to provide a vacuum.
As seen in
Generally, the cooling member 120 is configured to receive boil-off gas from the helium vessel 104, and to act as a heat exchanger using the boil-off gas to cool the cold-head cryocooler 110 (e.g., by cooling a sleeve surrounding the cryocooler). For example, in various embodiments the cooling member 120 includes a pathway configured to receive boil-off gas from the helium vessel 104 to be circulated through the pathway to cool the cold-head cryocooler 110. In various embodiments, the pathway has an interior cross-section configured to act as a heat exchanger. Various different manufacturing techniques may be employed to form the cross-section. As one example, the interior cross-section may be formed by additive manufacturing (e.g., 3D printing). For example, additive manufacturing may be employed to provide complex internal shapes to direct boil-off gas flow that are not possible or practical with other manufacturing techniques. In other embodiments, the interior cross section may be formed by alternate manufacturing techniques, such as welding, brazing, or casting.
The cooling member 120 is schematically depicted as a block in
In various embodiments, the cooling member 120 is configured as a cooling sleeve or jacket. The cooling jacket in various embodiments defines a generally cylindrically shaped structure having an inner wall and outer wall extending along a length of the cold-head cryocooler and surrounding the cold-head cryocooler, with the pathway that receives the boil-off gas extending in the volume between the inner wall and the outer wall. The outer wall and inner wall may each define a continuous cylindrical surface. For example,
The depicted cooling jacket 122 includes an outer surface 124 that defines a sleeve exterior 126. Also, the depicted cooling jacket 122 includes a pathway 128 disposed radially inwardly of the sleeve exterior 126 defined by the cooling jacket 122 (e.g., defined by the outer surface 124). The cooling jacket 122 is configured to receive boil-off gas from the helium vessel 104 to be circulated through the pathway 128 to cool the cold-head cryocooler. In the illustrated embodiment, the cooling jacket 122 includes access ports 121 that may be used as inlets and outlets for the boil-off gas. It may be noted that the access ports can be in any shape and orientation. In various embodiments, the cooling jacket is made of a thermally conductive metal, such as aluminum, copper, or stainless steel, by way of example. It may be noted that in various embodiments, the cooling jacket 122 (or aspects thereof) may be built by any type of non-conventional and conventional manufacturing methods.
In various embodiments, the cooling jacket 122 may be disposed about the first stage 112 (or portions thereof) and/or the second stage 114 (or portions thereof). For example,
As discussed above, in various embodiments, the pathway 128 (or aspects thereof) may be formed in various embodiments to provide complex interior shapes between the inner surface 125 and outer surface 124 of the cooling jacket, or to provide complex interior shapes within an interior of tubing wrapped around one or more aspects of the cold-head cryocooler 110. As one example, additive manufacturing may be utilized to help provide complex passageways for improved thermal performance in various embodiments. Other manufacturing techniques may be used additionally or alternatively in various embodiments.
It may be noted that the inner surface 125 and/or outer surface 124 of the cooling jacket 122 need not necessarily by straight. For example,
Additionally or alternatively to a sleeve including a pathway for boil-off gas radially inward of an exterior of the sleeve, in various embodiments a pathway for boil-off gas may be provided via a tube disposed radially outward of the exterior of the sleeve. For example,
Additionally or alternatively to the sleeves and tubes discussed in connection with
At 802, a cold-head cryocooler (e.g., cold-head cryocooler 110) is coupled to a helium vessel of an MRI system (e.g., helium vessel 104 of MRI system 102). The cold-head cryocooler is configured to cool at least one of superconducting magnets or a thermal shield of the MRI system. For example, the cold-head cryocooler may be used to cool vaporized cryogen which is then returned to the helium vessel. The cold-head cryocooler may be coupled to the helium vessel mechanically and fluidly, either directly or indirectly. For example, the cold-head cryocooler may be indirectly mounted mechanically to the helium vessel by being mounted to a structure that is in turn mounted to the helium vessel. The cold-head cryocooler is fluidly coupled to the helium vessel (e.g., via a conduit) to receive vaporized cryogen from the helium vessel.
At 804, a cooling jacket (e.g., cooling jacket 122) is disposed about at least a portion of the cold-head cryocooler. The cooling jacket has an outer surface that defines a sleeve exterior, and includes a pathway disposed radially inwardly of the sleeve exterior. (See, e.g.,
In various embodiments, the cooling jacket includes a pathway formed or defined to act as a heat exchanger. In some embodiments, the pathway is formed using using additive manufacturing. In some embodiments, an open pathway devoid of channels is formed. In some embodiments, the pathway is additively manufactured to have a cross-section defining a honeycomb arrangement. As one more example, in some embodiments, the pathway is additively manufactured to have a cross-section defining an open-cell arrangement.
As discussed herein, the cooling jacket in various embodiments is disposed about a first stage of the cold-head cryocooler. In the illustrated example, at 808, the cooling jacket is disposed about the first stage. For example, at 810, the cooling jacket is joined to a second stage sleeve (e.g., second stage sleeve 140) with an adaptor plate (e.g., adaptor plate 130).
At 812, an outer tube (e.g., outer tube 150) is disposed about the sleeve exterior of the cooling jacket. The outer tube is configured to receive boil-off gas from the helium vessel and has an additively manufactured internal structure to define a pathway through which the boil-off gas flows. It may be noted that in some embodiments, the outer tube may be used alternatively to a cooling sleeve as discussed herein. Generally, the outer tube is wrapped in a helical fashion about an exterior of a cold-head sleeve. The outer may be wrapped about a first stage (or portions thereof) and/or a second stage (or portions thereof) of the cold-head cryocooler in various embodiments.
At 814, of the illustrated embodiment, insulation is disposed around at least a portion of the exterior of the cold-head cryocooler. (See, e.g.,
As discussed herein various methods and/or systems (and/or aspects thereof) described herein may be implemented in connection with an MRI system. For example,
The system control 32 includes a set of modules connected together by a backplane 32a. These include a CPU module 36 and a pulse generator module 38 which connects to the operator console 12 through a serial link 40. It is through link 40 that the system control 32 receives commands from the operator to indicate the san sequence that is to be performed. The pulse generator module 38 operates the system components to carry out the desired scan sequence and produce data which indicates the timing, strength and shape of the RF pulses produced, and the timing and length of the data acquisition window. The pulse generator module 38 connects to a set of gradient amplifiers 42, to indicate the timing and shape of the gradient pulses that are produced during the scan. The pulse generator module 38 can also receive patient data from a physiological acquisition controller 44 that receives signals from a number of different sensor connected to the patient or subject, such as ECG signals from electrodes attached to the patient. And finally, the pulse generator module 38 connects to a scan room interface circuit 46 which receives signals from various sensors associated with the condition of the patient and the magnet system. It is also through the scan room interface circuit 46 that a patient positioning system 48 receives commands to move the patient to the desired position for the scan.
The gradient waveforms produced by the pulse generator module 38 are applied to the gradient amplifier system 42 having Gx, Gy, and Gz amplifiers. Each gradient amplifier excites a corresponding physical gradient coil in a gradient coil assembly generally designated 50 to produce the magnetic field gradients used for spatially encoding acquired signals. The gradient coil assembly 50 and RF shield (not shown) form a part of a magnet assembly 52 which includes a polarizing magnet 54 and a RF coil assembly 56. A transceiver module 58 in the system control 32 produces pulses which are amplified by an RF amplifier 60 and coupled to the RF coil assembly 56 by a transmit/receive switch 62. The resulting signals emitted by the excited nuclei in the patient may be sensed by the same RF coil assembly 56 or apportion thereof and coupled through transmit/receive switch 62 to a preamplifier 64. The amplified MR signals are demodulated, filtered, and digitized in the receive section of the transceiver 58. The transmit/receive switch 62 is controlled by a signal from the pulse generator module 38 to electrically connect the RF amplifier 60 to the coil assembly 56 during the transmit mode and to connect the preamplifier 64 to the coil assembly 56 during the receive mode. The transmit/receive switch 62 can also enable a separate RF coil (for example, a surface coil) to be used in either the transmit or receive mode. The magnet assembly 52 may be cooled cryogenically. For example, the magnet assembly 52 of the depicted embodiment is disposed within a helium vessel 53 that utilizes helium to cryogenically cool the magnet assembly 52. A thermal shield 55 is also disposed about the magnet assembly 52.
The MR signals picked up by the selected RF coil are digitized by the transceiver module 58 and transferred to a memory module 66 in the system control 32. A scan is complete when an array of raw k-space data has been acquired in the memory module 66. This raw k-space data is rearranged into separate k-space data arrays for each image to be reconstructed, and each of these is input to an array processor 68 which operates to Fourier transform the data into an array of image data. This image data is conveyed through the serial link 34 to the computer system 20 where it is stored in memory, such as disk storage 28. In response to commands received from the operator console 12, this image data may be archived in long term storage, such as on the tape drive 30, or it may be further processed by the image processor 22 and conveyed to the operator console 12 and presented on the display 16.
It should be noted that the various embodiments may be implemented in hardware, software or a combination thereof. The various embodiments and/or components, for example, the modules, or components and controllers therein, also may be implemented as part of one or more computers or processors. The computer or processor may include a computing device, an input device, a display unit and an interface, for example, for accessing the Internet. The computer or processor may include a microprocessor. The microprocessor may be connected to a communication bus. The computer or processor may also include a memory. The memory may include Random Access Memory (RAM) and Read Only Memory (ROM). The computer or processor further may include a storage device, which may be a hard disk drive or a removable storage drive such as a solid-state drive, optical disk drive, and the like. The storage device may also be other similar means for loading computer programs or other instructions into the computer or processor.
As used herein, the term “computer” or “module” may include any processor-based or microprocessor-based system including systems using microcontrollers, reduced instruction set computers (RISC), ASICs, logic circuits, and any other circuit or processor capable of executing the functions described herein. The above examples are exemplary only, and are thus not intended to limit in any way the definition and/or meaning of the term “computer”.
The computer or processor executes a set of instructions that are stored in one or more storage elements, in order to process input data. The storage elements may also store data or other information as desired or needed. The storage element may be in the form of an information source or a physical memory element within a processing machine.
The set of instructions may include various commands that instruct the computer or processor as a processing machine to perform specific operations such as the methods and processes of the various embodiments. The set of instructions may be in the form of a software program. The software may be in various forms such as system software or application software and which may be embodied as a tangible and non-transitory computer readable medium. Further, the software may be in the form of a collection of separate programs or modules, a program module within a larger program or a portion of a program module. The software also may include modular programming in the form of object-oriented programming. The processing of input data by the processing machine may be in response to operator commands, or in response to results of previous processing, or in response to a request made by another processing machine.
As used herein, a structure, limitation, or element that is “configured to” perform a task or operation is particularly structurally formed, constructed, or adapted in a manner corresponding to the task or operation. For purposes of clarity and the avoidance of doubt, an object that is merely capable of being modified to perform the task or operation is not “configured to” perform the task or operation as used herein. Instead, the use of “configured to” as used herein denotes structural adaptations or characteristics, and denotes structural requirements of any structure, limitation, or element that is described as being “configured to” perform the task or operation. For example, a processing unit, processor, or computer that is “configured to” perform a task or operation may be understood as being particularly structured to perform the task or operation (e.g., having one or more programs or instructions stored thereon or used in conjunction therewith tailored or intended to perform the task or operation, and/or having an arrangement of processing circuitry tailored or intended to perform the task or operation). For the purposes of clarity and the avoidance of doubt, a general purpose computer (which may become “configured to” perform the task or operation if appropriately programmed) is not “configured to” perform a task or operation unless or until specifically programmed or structurally modified to perform the task or operation.
As used herein, the terms “software” and “firmware” are interchangeable, and include any computer program stored in memory for execution by a computer, including RAM memory, ROM memory, EPROM memory, EEPROM memory, and non-volatile RAM (NVRAM) memory. The above memory types are exemplary only, and are thus not limiting as to the types of memory usable for storage of a computer program.
It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the various embodiments without departing from their scope. While the dimensions and types of materials described herein are intended to define the parameters of the various embodiments, they are by no means limiting and are merely exemplary. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the various embodiments should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted based on 35 U.S.C. § 112(f) unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.
This written description uses examples to disclose the various embodiments, including the best mode, and also to enable any person skilled in the art to practice the various embodiments, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the various embodiments is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if the examples have structural elements that do not differ from the literal language of the claims, or the examples include equivalent structural elements with insubstantial differences from the literal language of the claims.