Specific Absorption Rate (SAR) Reduction Pads, Magnetic Resonance Imaging (MRI) Systems, and Methods of Operating MRI Systems

Abstract

The present invention relates to a specific absorption rate (SAR) reduction pad 1. The SAR reduction pad 1 comprises a pad body 2, a first surface 3 arranged on one side of the pad body 2, a second surface 4 arranged on the other side of the pad body 2 opposite the first surface 3, and distance generating means 5, 6, 7. The distance generating means 5, 6, 7 are adapted to increase the distance between the first surface 3 and the second surface 4. The present invention further relates to a magnetic resonance imaging (MRI) system 16 comprising MRI electronics, a computing unit 22, and at least one specific absorption rate (SAR) reduction pad 1 as described above. The present invention further relates to a method of operating the magnetic resonance imaging (MRI) system 16.

Description

[Technical Field]

[0001] The present invention relates to a specific absorption rate (SAR) reduction pad, a magnetic resonance imaging (MRI) system having a SAR reduction pad, and a method of operating an MRI system. [Background technology]

[0002] Magnetic resonance imaging (MRI) deposits electromagnetic (EM) energy inside the patient's body, which can cause localized heating and therefore a risk of burns. A measure of the amount of power deposited by a radio frequency magnetic field in a mass of tissue is the specific absorption rate (SAR). Summary of the Invention [Problem to be solved by the invention]

[0003] In particular, radiofrequency (RF) burns can occur when a part of the body comes into contact with a high electric field while insufficient cooling is available. This is often the case when a large portion of the body contacts the inner wall of the MR bore. In such locations, high electric fields can exist because the wall is in close proximity to the RF body coil capacitor. Furthermore, the flow of ambient air that normally provides cooling to such heated skin areas is blocked. As a mitigation measure, pad placement using, for example, a dry towel, can be proposed. However, this still substantially obstructs the airflow. Furthermore, when the patient is already inside the bore, it is difficult to accurately place the pad. However, this is necessary to address the problematic location. Therefore, this situation is a typical failure mode of reported RF burns.

[0004] Additionally, dielectric pads can be manually placed to shield the body from EM fields around metal hardware such as MR coils and cables, but the actual effectiveness of this precaution during testing is unknown.

[0005] Furthermore, proper patient positioning is highly human-dependent, and among other tasks, clinical technical staff must manually interact with the patient and the scanner to minimize superficial heating due to local variations in SAR values and ensure safe routing of cables, such as coil leads and other metal objects, connected to or routed over the patient's body. If areas with predictably high SAR values are known, the aforementioned dielectric pads to reduce SAR can be manually placed. Furthermore, during the scan, patients must be monitored for reactions that may indicate localized increased heating, such as cries of pain or sudden involuntary body movements. However, sedated, impaired, or poorly informed patients may not feel or report increased heating, which could result in minor burns or long-term skin and tissue damage.

[0006] Furthermore, regional MRI coils, such as head, neck, carotid, or shoulder coils, are difficult to position and require individual adjustment by an experienced operator. Incorrectly positioned or missing dielectric pads can reduce the allowable SAR, degrade image quality, and cause patient discomfort or pain, which must be monitored throughout the exam. In many cases, the coil and SAR pads may be tolerable for a while but then need to be removed or repositioned due to patient discomfort. Interruptions to the exam can increase exam times, with further negative impacts on patient comfort, costs, and throughput rates. [Means for solving the problem]

[0007] The invention is defined by the independent claims. The dependent claims represent advantageous embodiments.

[0008] It is therefore an object of the present invention to provide a specific absorption rate (SAR) reduction pad, a magnetic resonance imaging (MRI) system, and a method of operating an MRI system that feature improved protection of the patient from localized overheating and / or burns.

[0009] The object of the present invention is solved by the subject matter of the independent claims, further embodiments are incorporated in the dependent claims.

[0010] In one aspect of the present invention, a specific absorption rate (SAR) reduction pad is provided. In particular, the SAR reduction pad is intended for use with a magnetic resonance imaging (MRI) system. The SAR reduction pad is intended to prevent overheating and / or burns of a patient's skin and / or tissue caused by localized high electromagnetic (EM) fields generated by the MRI system and / or by hot parts of the MRI electronics, such as coils, cables, and / or capacitors. Causes of overheating and / or burns of a patient's skin and / or tissue can be localized electromagnetic field hot spots of the transmit radio frequency (RF) coil, localized overheating of RF connection cables or RF traps, malfunctioning detuning circuitry, unsoldered capacitors, or incorrect shimming during operation of the MRI system.

[0011] The SAR reduction pad has a pad body, a first surface, and a second surface. The first surface is disposed on one side of the pad body, and the second surface is disposed on the other side of the pad body opposite the first surface. Specifically, the shape of the first surface can be similar to the shape of the second surface, and the distance between the first surface and the second surface can be shorter than the dimensions of the first and / or second surfaces. Furthermore, the first surface may be at least partially adjacent to the second surface. Alternatively and / or additionally, there may be a side surface connecting the first surface and the second surface.

[0012] The SAR reduction pad further comprises a distance generating means for increasing the distance between the first surface and the second surface. Increasing the distance between the first surface and the second surface can increase the distance between the patient and the MRI electronics, between the patient and the interior wall of the MRI system, and / or between the patient and the locally high EM field. For SAR reduction pads placed between the patient and the MRI electronics and / or between the patient and the interior wall of the MRI system, the distance between the first surface and the second surface can be increased by at least 5 mm and at most 15 mm. Furthermore, the distance between the first surface and the second surface can be increased only partially, i.e., by a fraction of the maximum possible value.

[0013] The SAR reduction pad, when the distance between the first and second surfaces is increased, moves the patient away from locally high EM fields, the MRI electronics, and / or the interior walls of the MRI system, thus reducing the specific absorption rate and, therefore, the risk of overheating and / or burns to the patient's skin and / or tissue. On the other hand, when the distance between the first and second surfaces is not increased, the SAR reduction pad requires less space, and therefore, patient positioning options in particular are not limited, or are only slightly limited, by the SAR reduction pad. Furthermore, when the distance between the first and second surfaces is not increased, more free space can be maintained inside the bore of the MRI system.

[0014] According to one embodiment, the distance generating means includes at least one chamber filled with a fluid and at least one fluid inlet fluidly connected to the at least one chamber. Therefore, the distance between the first surface and the second surface can be increased by injecting fluid into the at least one chamber through the at least one fluid inlet, such that the size of the chamber increases. The at least one chamber can be disposed between the first surface and the second surface, such that the increase in the size of the chamber moves the second surface away from the first surface, increasing the distance between the first surface and the second surface. The fluid can be a liquid or a gas, particularly air or another hazardous gas. The fluid can be forced into the at least one chamber at high pressure so that the distance between the first surface and the second surface is rapidly increased, thus protecting the patient's skin and / or tissue from overheating and / or burns. There can be one chamber per SAR reduction pad, or multiple chambers (e.g., air cushions) per SAR reduction pad. When there is more than one chamber per SAR reduction pad, the individual chambers can be fluidly connected to each other and / or to separate fluid inlets. When the individual chambers are not fluidly connected to each other but to separate fluid inlets, they can also be inflated separately, for example, so that the distance between the first surface and the second surface increases only at certain locations.

[0015] According to one embodiment, the distance generating means has at least one valve disposed between the at least one fluid inlet and the at least one chamber. Therefore, when fluid is supplied to the at least one fluid inlet, opening the at least one valve can realize a fluid connection from the fluid inlet to the chamber, thereby allowing the chamber to be filled with fluid. As an example, a SAR reduction pad can have one fluid inlet and multiple valves, each connected to one chamber. Opening only some of the valves results in the inflation of only the chamber connected to the open valve, while the other chambers remain deflated. That is, individual inflation of a single air cushion is provided, and thus, the increase in the distance between the first surface and the second surface occurs only at the location where the inflation chamber is located.

[0016] According to one embodiment, the distance generating means further includes at least one fluid outlet fluidically connected to the at least one chamber for circulating fluid through the at least one chamber. By allowing fluid to enter the chamber through the at least one fluid inlet and exit the chamber through the at least one fluid outlet, a fluid flow is generated, more specifically, to provide cooling to the patient's skin. As an example, the SAR reduction pad may be implemented with a fluid inlet and a fluid outlet on both sides of the SAR reduction pad. Alternatively, the chamber may be a U-shaped cushion or tube with the fluid inlet and fluid outlet on one side of the SAR reduction pad. The required fluid flow, e.g., the required air flow, can be easily generated by known means, for example, in a technical room associated with the MRI system. The fluid can then be guided directly into the magnet room of the MRI system through a waveguide via a plastic tube. By controlling the valves, particularly the valve between the fluid inlet and the chamber, and the valve between the chamber and the fluid outlet, both the fluid flow and the degree of inflation of the chamber can be controlled.

[0017] According to one embodiment, the distance generating means comprises at least one mechanical distance generator. An example of such a mechanical distance generator is a folding strip, one end of which can be attached to a first surface and a second end of which can be attached to a second surface. The folding strip can be in a folded state and can be unfolded when the distance between the first and second surfaces is to be increased. Such unfolding can be performed, for example, by activating a motor or by pulling an auxiliary strip attached to the center of the folding strip. As another example, the mechanical distance generator can comprise a bolt and / or a threaded rod that is guided through the first surface of the SAR reduction pad and contacts the second surface of the SAR reduction pad. The bolt and / or the threaded rod can then be actuated from the outside, for example, screwed in, to push the second surface away from the first surface and thus increase the distance between the first and second surfaces.

[0018] According to one embodiment, the SAR reduction pad further comprises at least one sensor. The sensor may be a pressure sensor, e.g., a sensor measuring the force between the first surface and the second surface. The pressure sensor may be a known pressure sensor. Furthermore, the pressure sensor may be a flow sensor measuring the flow resistance of a fluid flowing through the chamber of the SAR reduction pad. The higher the pressure on the SAR reduction pad, the higher the flow resistance, which can be used to infer the pressure. As an example, the pressure may be applied to the SAR reduction pad by a patient's arm contacting the inner wall of the bore of the MRI system. The sensor may also be an electromagnetic field sensor, particularly adapted to detect high EM fields that may lead to local overheating and / or burns of the patient's skin and / or tissue. The sensor may be a temperature sensor. In particular, when the SAR reduction pad is close to or in contact with the patient's skin, an increase in temperature measured by the temperature sensor may indicate overheating of the patient's skin and / or tissue. The sensor may also be a distance sensor, such as an ultrasound, radar, lidar, and / or optical sensor, that directly measures the distance between the SAR reduction pad and the portion of the MRI system that generates the EM field, and / or the distance between the patient's skin and the portion of the MRI system that generates the EM field.

[0019] According to one embodiment, the SAR reduction pad further comprises an electrical, electronic, optical, and / or wireless connector. The electrical and / or electronic connector can provide a wired connection, for example, a low-voltage differential signaling (LVDS) digital data connection, to another SAR reduction pad and / or a computing unit of an MRI system. Similarly, the optical connector can provide an optical data connection to another SAR reduction pad and / or a computing unit of an MRI system via an optical fiber. A wireless data connection can also be established to another SAR reduction pad and / or a computing unit of an MRI system. As an example, several SAR reduction pads can be connected to each other via LVDS or optical data connections, and one of the SAR reduction pads is further connected wirelessly to the computing unit of the MRI system. The wirelessly connected SAR reduction pad distributes data received from the computing unit to other SAR reduction pads and collects and transmits data from other SAR reduction pads to the computing unit. The data received from the computing unit can include valve control data and / or mechanical distance generator commands, and the data transmitted to the computing unit can include sensor readings from the sensors of the SAR reduction pads.

[0020] In another aspect of the present invention, there is provided a magnetic resonance imaging (MRI) system comprising MRI electronics, a computing unit, and at least one SAR reduction pad according to the above description.

[0021] The MRI electronics include at least one of a transmit coil for transmitting radio frequency (RF) signals, a receive coil for receiving RF signals, a transmit / receive coil for transmitting and receiving RF signals, a cable, and a capacitor. The cable may be a cable connecting the RF coil. The MRI electronics may be a source of overheating and / or burns to the patient's skin and / or tissue due to, for example, local field hot spots of the transmit RF coil, local overheating of the RF connecting cable or RF trap, malfunction of detuning circuitry, and / or unsoldering of capacitors.

[0022] The computing unit may be a local computing unit of the MRI system, but may also be installed remotely, e.g., cloud-based. It may be a single unit or may have several connected computing devices. Part of the computing unit may also be integrated into at least one SAR reduction pad.

[0023] When there are two or more SAR reduction pads, they can be interconnected into a larger assembly using additional interconnection devices that provide mechanical, electrical, electronic, and / or optical coupling between the SAR reduction pads. Some of the SAR reduction pads can further have wireless transceivers for exchanging data with a computing unit to transmit sensor data and received control data. SAR reduction pads with wireless transceivers can pool data from other SAR reduction pads and transmit the pooled data to the computing unit via electronic and / or optical connections. Similarly, SAR reduction pads with wireless transceivers can receive data from the computing unit and then distribute the data to other SAR reduction pads via electronic and / or optical connections.

[0024] According to one embodiment, at least one SAR reduction pad is attached to the bore wall of the MRI system, particularly to the side of the bore wall. Here, the bore may be an open or closed bore and refers to the cavity in which the patient or part of the patient is placed for examination. Several options are possible, such as one or more SAR reduction pads covering the entire bore wall, or one or more SAR reduction pads placed on the sides of the bore wall, e.g., on the left and right sides of the patient. Since the SAR reduction pads do not require much space if the distance between the first and second surfaces is not increased, they can remain inside the bore without significantly interfering with workflow. However, when they are needed, they are always placed in the correct place. Alternatively, the SAR reduction pads may be removable and can be temporarily applied as an accessory if necessary.

[0025] Alternatively or additionally, at least one SAR reduction pad constitutes at least a portion of the bore wall of the MRI system. The mechanical stability of the bore can be provided by a frame, and the thickness of the solid hole wall can be reduced, or the solid bore wall can be omitted entirely. Therefore, the size of the hole can be increased, for example, by 1.5 cm in diameter, compared to a regular solid bore wall. The SAR reduction pad can then be considered an adjustable bore wall that can be adapted to the specifics of the patient inside the bore and / or the MRI scan. For example, the distance between the first and second surfaces can be increased if the patient is likely to touch the bore and / or get too close to the coil, and the distance between the first and second surfaces can remain small if there is no need for a thick bore wall, thus preserving space. Furthermore, when the distance between the first and second surfaces is small, larger patients can be scanned and / or the feeling of claustrophobia can be reduced due to the free space obtained.

[0026] Alternatively or additionally, at least one SAR reduction pad is disposed on at least one portion of the MRI electronics, for example around a cable. If necessary, the distance between the cable and its surroundings, particularly the patient, can be increased by increasing the distance between the first and second surfaces of the SAR reduction pad. In the case of a cylindrical SAR reduction pad, the first surface can be the inner surface and the second surface can be the outer surface, or vice versa.

[0027] Alternatively or additionally, at least one SAR reduction pad is attached to the patient. For example, the SAR reduction pad may be attached to the patient's clothing. By increasing the distance between the first and second surfaces of the SAR reduction pad, the patient's skin and / or tissue can be moved further away from sources of overheating, such as from locally strong EM fields and / or from hot parts of the MRI electronics.

[0028] According to one embodiment, the MRI system further includes a user interface, wherein the computing unit is configured to determine the placement of the SAR reduction pads and provide SAR reduction pad placement instructions via the user interface. To determine the placement of the SAR reduction pads, the computing unit can use data regarding the position of MRI electronics, such as coils and cables, which data can be acquired using the patient's position and / or posture and / or a radar sensor, a lidar sensor, and / or an optical positioning detection unit having at least one, preferably two or more cameras. The placement of the SAR reduction pads can be further determined based on details of the MRI scan to be performed, such as which body part to be scanned and / or the scheduled scan sequence. Furthermore, patient characteristics, such as age, size, and / or weight, as well as sedative medication, can also be used to determine the placement of the SAR reduction pads. In particular, the placement of the SAR reduction pads is determined so that the SAR reduction pads are placed in locations where there is a risk of overheating and / or burns to the patient's skin and / or tissue. The placement instructions are then provided via the user interface, which can be a display indicating the locations where the SAR reduction pads should be placed. With such placement instructions, the skill requirements for the user placing the SAR reduction pads are relatively low, and placement of the SAR reduction pads no longer depends on highly trained operator staff. Thus, automation of clinic workflow for MRI scans is possible without the need for highly trained users. Optionally, the SAR reduction pads may have identification means, such as color coding, icons, and / or alphanumeric labels, which are also displayed on the display. The position of each distinct SAR reduction pad, along with its identification, is then determined so that sensor readings from the SAR reduction pads can be assigned to specific positions on the SAR reduction pads, and instructions, in particular for increasing the distance between the first surface and the second surface, can be provided to the correct SAR reduction pad.

[0029] According to one embodiment, the computing unit is configured to selectively activate the distance generating means. This selective activation may include only partially increasing the distance between the first and second surfaces of some of the SAR reduction pads and / or portions of the SAR reduction pads. In particular, activation of the distance generating means is performed only when an increase in the distance between the first and second surfaces is required to reduce the risk of overheating and / or burns. By way of example, selective activation of the distance generating means of SAR reduction pads attached to and / or constituting the bore inner wall allows the bore inner wall to adapt to its required shape. Furthermore, by selectively activating the distance generating means, a spatial configuration of active SAR reduction pads is generated to optimize a specific local absorptivity value for a specific MRI scan sequence and a specific patient, thereby reducing the risk of overheating and / or burns. The activation of the distance generating means itself depends on the specifics of the SAR reduction pad. By way of example, the chamber can be inflated by directing airflow through a fluid inlet connected to the chamber. As another example, the mechanical distance generator can be activated by sending electrical and / or electronic impulses to the mechanical distance generator, for example via the transmitting field of the RF coil, or wirelessly, in particular with RF rectification to control an electronic on / off switch. Similarly, a valve can be opened or closed to allow fluid to fill the chamber. Furthermore, both the valve connected to the fluid inlet and the valve connected to the fluid outlet can be controlled to control both the chamber's inflation level and the fluid flow, which provides additional cooling to the patient's skin and / or tissue. In particular, activation of the distance generating means is based on sensor readings. The sensors may be radar sensors, lidar sensors, and / or optical positioning detection units that capture the patient's positioning and / or the positioning of MRI electronics such as cables and coils.Using the sensor readings, the computing unit identifies locations most susceptible to overheating and / or burns and activates distance generating means at said locations. The sensor may furthermore in particular be a pressure sensor of the SAR reduction pad, which detects, for example, when the patient touches the bore wall. The distance generating means corresponding to the location where the highest pressure is detected is then activated. The sensor may furthermore in particular be a temperature sensor and / or an EM field sensor of the SAR reduction pad, which detects an actual increase in temperature and / or a locally strong EM field, resulting in activation of the respective distance generating means. In particular, the sensor readings are continuously acquired, transmitted to the computing unit, and used by the computing unit to selectively activate the distance generating means. Furthermore, the sensor readings can be stored by the computing unit for later offline analysis and, for example, for further improvement of the MRI system and / or the computing unit. For selective activation of the SAR reduction pads, the computing unit may further take into account other data such as the planned MRI scan sequence, the age, size and / or weight of the patient, and the condition of the patient, e.g., his or her sedation state.

[0030] In some embodiments, the pads may be of the dielectric pad type, which leads to a compromise in the acceptable SAR level and allows for a further reduction in the SAR level.

[0031] In some embodiments, different types of sensors can be used. The aforementioned temperature sensor can be an infrared (IR) sensor configured to measure SAR levels. In some embodiments, the sensor can directly control the pad to initiate pad filling. In some embodiments, the temperature and / or IR sensor is configured to measure the subject's thermal physiological state and / or the local temperature / IR field spot of the coil and device surface, the MRI inner bore, and other devices of the MRI apparatus. In some embodiments, the sensor can be used in conjunction with machine learning algorithms to provide closed-look operation and control valves in the MR system. For example, if a certain threshold is passed, the distance pad can be fully activated and the MR system can be shut down, or the system can indicate that SAR / temperature / IR levels are increasing and potentially damaging to the patient.

[0032] In some embodiments, the electromagnetic field sensor can be a passive RF sensor / antenna that can couple electromagnetic energy to a rectifier. The rectifier is connected to an actuator of a valve that controls the filling of the pad. The actuator can have a melting device that opens the valve to automatically fill the pad. The melting device can be a disposable device or an actuator based on MEMS (microelectromechanical systems) technology. The melting device can have a non-magnetic spring and a locking mechanism that allows the spring to open. The passive antenna can be, for example, a loop antenna, a short dipole, a dielectric antenna, a stripline antenna, or a periodic antenna (metamaterial) that couples EM energy to the sensing device. In some embodiments, the RF sensor signal can be configured to be digitized via an ADC / SDR component, where the signal threshold is controlled in the digital domain. The digital output can control the actuator to open or close the valve in a predetermined manner. The digital controller (3) can also be coupled to an AI-trained network that further controls the MRI scanner.

[0033] In some embodiments, instead of an RF sensor, other types of sensors for measuring EM fields can be used, including any one or combination of bolometers, defined wires, electromechanical, dielectric devices, electro-optic crystal based electric field sensors, MEMS electric field sensors using force deflection with capacitance testing.

[0034] In some embodiments, a method for inflating / filling with fluid is described. It should be understood that this method, or a similar method based on the same underlying concept, can be applied to any of the embodiments described herein. In a preferred embodiment, several sensors within the MRI bore are monitored, including any one or combination of an IR camera, a bolometer, a local temperature sensor, and a distributed temperature sensor. In some embodiments, sensors for measuring patient presence can be monitored as well. One or more pads are then controlled by a pad control unit. The pad control unit can include energy harvesting and storage means (e.g., capacitors, batteries) for providing power in the event of a coil power supply interruption. Pad activation can depend on sensor data. For example, if a sensor detects heat, the pad can be deployed within a controlled time interval to avoid mechanically harming the patient. In other embodiments, the deployment force can be adapted for the clinical environment and situation. In some other embodiments, if an MRI sequence with high SAR is planned, the pad can be deployed in a prescribed manner to align a safe distance between the tissue and the object. In some embodiments, pad deployment can be prevented by the controller for specific clinical applications, individual locations, and patient weight. In some embodiments, one or more pads are deployed uniformly across the surface, or deployment parameters are tailored to the size, weight, location, and condition of the clinical setting, the individual patient's condition, and individual location. In some embodiments, one or more pads can be maintained at a defined pressure and therefore a defined distance using at least two valves, so that the flowing air pressure maintains the defined distance and further maintains the cooling effect. Pads or combinations of different pads are preferably filled with air or gas (CO2), as such air or gas is invisible in MRI images. Liquid filling of the pads can be applied in certain situations or when higher pressures are required. The liquid is preferably a non-proton-based material.

[0035] In certain situations and pads, deployment is preferably achieved only in critical situations, and therefore the pads may be disposable. The pads can be activated by liquid foam using a chemical reaction. Disposable pads can be secured to the RF coil or medical device using Velcro or a mechanical holder and can be mechanically detached from the object after use. The pads can have integrated foam or a non-magnetic spring. To deploy, a valve is opened and deployment is activated in a predetermined manner. This mechanical process is reversible. For reconfiguration, a controlled vacuum is initiated. The pad is equipped with two valves: one for inflation and one for deflation; therefore, pad filling is controlled by the two valves with vacuum and air pressure functions. Sensor data can be recorded in a local circular buffer and in local non-volatile memory to provide event timestamps and data recollection for clinical researchers. In some embodiments, machine learning is provided with the following information: temperature, patient size, age, weight, and table position. The machine learning model can take into account the following diagnostic parameters: MRI sequence information, coil design, positioning, patient history, vital signs monitoring, and compatibility with external devices such as anesthesia mask. These parameters are continuously updated, and for a clinical imaging session, the MR sequence or even the positioning may change. The sensor readings are used as input parameters for the trained network. The output of the network determines the pad deployment characteristics (delay, force, deployment time, inflation speed, threshold, trigger level). Other implementations of machine learning algorithms

[0036] It should be appreciated that in clinical settings, configurable dielectric pads may be needed to compensate for size, location, and individual subject-related tissue parameters that cannot be fully accounted for in the EM calculations that are the subject of this invention. The pads can be configured to be inflated / filled with a high-permittivity dielectric emulsion (e.g., an oil suspension containing calcium copper titanate, NPO porcelain, perfluorocarbon, and polymeric materials). These pads are placed in locations where high local SAR and inhomogeneous B1 fields are expected, such as local transmit coils used in MRI spectroscopy. The pads may be fixed, mechanically integrated, or detachable, and are placed in locations where high B1 inhomogeneities and electric fields are expected. The specified positions and configurations can be calculated and approximated by an EM field simulator. Pad expansion can also be triggered by the sensor proposed above when a specified temperature threshold is exceeded.

[0037] According to one embodiment, the computing unit is configured to issue an alert, modify the MRI scan sequence, and / or stop the MRI scan based on the sensor readings. As one example, a change in detected pressure may indicate patient movement, leading to the issuance of a patient alarm and / or a nurse call. As another example, detection of high temperatures and / or strong local EM fields may first result in activation of the distance generating means, as described above. If the activation of the distance generating means does not sufficiently reduce the temperature and / or EM field, the computing unit may modify the MRI scan sequence, for example, by performing a shorter scan, a scan with reduced EM field strength, and / or a scan with a different spatial distribution of the EM field. Alternatively, or if modifying the MRI scan sequence does not result in a sufficient reduction in the temperature and / or EM field, the computing unit may stop the MRI scan entirely to ensure patient safety.

[0038] According to one embodiment, the computing unit comprises an artificial intelligence system, particularly a trained machine learning system such as an artificial neural network. When the computing unit is configured to both determine the placement of SAR reduction pads and selectively activate the distance generating means, the computing unit may actually comprise two artificial intelligence systems, one for each task. The training of the artificial intelligence may be based on data acquired in a clinical study of routine MRI examinations, where hyperthermia is monitored by vital signs sensing, for example, using optical and / or infrared cameras and / or smart pads with temperature and / or EM magnetic field sensors. In the clinical study, the positioning of the SAR reduction pads is performed manually by a trained operator, for example, according to standard procedures. The outputs of a positioning detection unit and / or readings from both the mobile and integrated smart pads (particularly the SAR reduction pads) are collected, which may include EM field sensors, temperature sensors, and / or position sensors such as a three-axis digital accelerometer and a three-axis digital gyroscope. These data, together with MRI characteristics such as machine type and imaging sequence, and patient characteristics such as age, size, weight, anesthesia / sedation, and / or pediatric status, are used as inputs for training an artificial intelligence, in particular a neural network. The EM field sensor can comprise any means, active or passive, that can be used for and / or in connection with measuring the EM field. The EM field sensor can externally include a computing unit, in particular for activation of the distance generating means, for example, a conventional algorithm that activates the distance generating means when a predetermined threshold value of the EM field and / or temperature value is exceeded.

[0039] In yet another aspect of the present invention, there is provided a method for operating a magnetic resonance imaging (MRI) system according to the above description. According to this method, the placement of SAR reduction pads is determined by a computing unit, and the determined placement is provided to a user via a user interface. The SAR reduction pads are then placed by the user according to the determined placement of the SAR reduction pads. For this placement, a user with ordinary skills is sufficient, and a highly trained user with sufficient experience in placing SAR reduction pads is not required. Furthermore, by determining the placement of the SAR reduction pads using a computing unit, the need for a human evaluation of the patient and the planned MRI scan sequence and the placement of the SAR reduction pads based on the experience of a highly trained user is eliminated. Therefore, the workflow for placing the SAR reduction pads is improved, particularly automated, simplified, and accelerated. Once the SAR reduction pads are placed, the MRI scan and / or MRI scan sequence is performed.

[0040] According to one embodiment, sensor readings are obtained before and / or during the MRI scan and / or MRI scan sequence, and the distance generating means is selectively activated based on the obtained sensor readings, which results in a reduced risk of overheating and / or burns to the patient's skin and / or tissue.

[0041] Further details and advantages of the method of operating the magnetic resonance imaging system can be found in the above description where the operation of the MRI system is described together with a description of the MRI system itself.

[0042] It is to be understood that the invention can be advantageously combined with the dependent claims or with the above and respective independent claims.

[0043] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

[0044] Preferred embodiments of the invention will now be described, by way of example only, with reference to the drawings in which: [Brief explanation of the drawings]

[0045] [Figure 1a] 1 is a schematic cross-sectional view of an embodiment of a SAR reduction pad. [Figure 1b] 1b is a schematic cross-sectional view of the SAR reduction pad of FIG. 1a in an activated state; [Figure 2a] 10 is a schematic cross-sectional view of another embodiment of a SAR reduction pad. [Figure 2b] 2b is a schematic cross-sectional view of the SAR reduction pad of FIG. 2a in an activated state; [Figure 3a] 10 is a schematic cross-sectional view of yet another embodiment of a SAR reduction pad. [Figure 3b] 3b is a schematic cross-sectional view of the SAR reduction pad of FIG. 3a in an activated state; [Figure 4a] 10 is a schematic cross-sectional view of yet another embodiment of a SAR reduction pad. [Figure 4b] 4b is a schematic cross-sectional view of the SAR reduction pad of FIG. 4a in a partially activated state. [Figure 5] 10 is a schematic cross-sectional view of yet another embodiment of a SAR reduction pad. [Figure 6] FIG. 10 is a schematic top view of yet another embodiment of a SAR reduction pad. [Figure 7] FIG. 10 is a schematic top view of yet another embodiment of a SAR reduction pad. [Figure 8] 1 is a schematic cross-sectional view through a bore of an embodiment of an MRI system. [Figure 9] 10 is a schematic cross-sectional view through a bore of another embodiment of an MRI system. [Figure 10a] 1 is a schematic cross-sectional view of a cable having an SAR reduction pad. [Figure 10b] 10a is a schematic cross-sectional view of the cable of FIG. 10a with the SAR reduction pads activated. [Figure 11] 10 is a schematic cross-sectional view of yet another embodiment of an MRI system. [Figure 12]1A and 1B show examples of placement of SAR reduction pads on a patient. [Figure 13] 1 is a schematic diagram of yet another embodiment of an MRI system. DETAILED DESCRIPTION OF THE INVENTION

[0046] Like numbered components in these figures are either equivalent components or perform the same function. An aforementioned component is not necessarily described in a subsequent figure if the functionality is equivalent.

[0047] FIG. 1a shows a schematic cross-sectional view of a specific absorption rate (SAR) reduction pad 1 having a pad body 2, a first surface 3 disposed on one side of the pad body 2, and a second surface 4 disposed on the other side of the pad body 2 opposite to the first surface 3. The SAR reduction pad 1 further comprises a chamber 5 functioning as a distance generating means. The chamber 5 is fluidly connected to a fluid inlet 6, allowing a fluid, particularly a gas such as air or nitrogen or a liquid, to enter and expand the chamber 5. When the chamber expands, the distance between the first surface and the second surface increases, as shown in FIG. 1b. The increase in distance can move the patient's body, particularly the patient's skin, away from locations with locally strong electromagnetic (EM) fields and / or away from locations with hot spots, both of which can lead to overheating and / or burns of the patient's tissue.

[0048] In another embodiment (not shown here), the SAR reduction pad 1 can comprise a flexible foam containing multiple air chambers, which may be further combined with an engineered metamaterial, for example, such that alternating layers of foam and metamaterial are combined.

[0049] FIG. 2a shows a schematic cross-sectional view of another embodiment of a SAR reduction pad 1. Instead of the inflatable chamber 5 of the previous embodiment, this SAR reduction pad 1 has a mechanical distance generator 7 having a plate 7.1 hinged at hinge 7.2 close to the first surface 3. Plate 7.1 can be erected, for example, by activating a small electric motor, as shown in FIG. 2b, or by pulling a wire connected to plate 7.1 at a distance away from hinge 7.2 (neither option is shown here). Again, erecting plate 7.1 increases the distance between the first surface 3 and the second surface 4.

[0050] 3a shows a schematic cross-sectional view of yet another embodiment of a SAR reduction pad 1. Again, this SAR reduction pad has a mechanical distance generator 7 having a screw nut 7.3 fixed to the first surface 3 and a screw 7.4 partially threaded into the screw nut 7.3. By further threading the screw 7.4, the tip of the screw 7.4 contacts the second surface 4, as shown in FIG. 3b, and moves the second surface 4 away from the first surface 3. Again, this increases the distance between the first surface 3 and the second surface 4.

[0051] 4a shows a schematic cross-sectional view of yet another embodiment of a SAR reduction pad 1. This SAR reduction pad 1 has four chambers 5, although other numbers of chambers are possible. There are also four fluid inlets 6, each of which is fluidly connected to one of the chambers 5. To provide the best compromise between the available free space and the freedom to position the scanning arrangement on the one hand, and overheating and / or burn protection on the other hand, the chambers 5 can be inflated separately, as shown in FIG. 4b; in this example, only the two left chambers 5 are inflated, while the two right chambers 5 remain in a deflated state.

[0052] 5 shows a schematic cross-sectional view of yet another embodiment of a SAR reduction pad 1. This SAR reduction pad 1 further comprises four chambers 5. The chambers 5 are fluidly connected to a common fluid inlet 6, with valves 8 disposed between the fluid inlet 6 and the individual chambers 5. Thus, the individual chambers 5 can be individually inflated by opening and / or closing the respective valves 8.

[0053] FIG. 6 shows a schematic top view of yet another embodiment of the SAR reduction pad 1. In addition to the fluid inlet 6, this SAR reduction pad 1 also has a fluid outlet 9, which is fluidly connected to the chamber 5 via a valve 10. Therefore, by adjusting the positions of the valves 8 and 10, particularly by opening them, closing them, and / or leaving them partially open, both the degree of expansion of the chamber 5 and the fluid flow through the chamber 5 are controllable. The fluid flow can provide additional cooling to the patient's skin. Other possible shapes of the chamber 5 in the top view (not shown here) are U-shaped or toroidal. Furthermore, as another possible embodiment, a portion of the SAR reduction pad 1 can have a fixed distance between the first surface 3 and the second surface 4, for example, by having a foam structure between the first surface 3 and the second surface 4, while another portion of the SAR reduction pad 1 can have at least one chamber 5 that allows for an increased distance between the first surface 3 and the second surface 4.

[0054] 7 shows a schematic top view of yet another embodiment of a SAR reduction pad 1. Each SAR reduction pad 1 is connected to valves 8 and 10 and includes a microcontroller 11 adapted to control the valves 8 and 10. Furthermore, each SAR reduction pad 1 includes at least one sensor 12. The sensor 12 may be a pressure sensor for detecting mechanical pressure applied to the SAR reduction pad 1, an electromagnetic (EM) field sensor, a detected electromagnetic field, particularly its intensity, and / or a temperature sensor for detecting the temperature at the SAR reduction pad 1. The sensor 12 is further connected to the microcontroller 11 and provides sensor readings to the microcontroller 11. The microcontrollers 11 of the SAR reduction pads 1 are connected to each other via an interconnection device 13, which may be an electrical cable or an optical fiber. The interconnection device may be used to transfer sensor readings and control signals for the valves between the microcontrollers 11, and in some embodiments, the interconnection device 13 may further include a spacer for providing a predetermined distance between individual SAR reduction pads 1. One of the SAR reduction pads 1 further has a wireless transceiver 14 that is also connected to its respective microcontroller 11. Sensor readings collected by the microcontroller 11, either directly from the sensors 12 associated with the microcontroller 11 or via the microcontroller 11 of the other SAR reduction pad 1, may be transmitted wirelessly to a computing unit of the MRI system via the wireless transceiver 14. Furthermore, control data for the distance generating means, in this example, control data for valves 8 and 10, can be received wirelessly by the wireless transceiver 14 and then transmitted to the valves 8 and 10, either directly or via the microcontroller 11 of the other SAR reduction pad 1.

[0055] In an alternative embodiment (not shown here), the SAR reduction pads 1 may also comprise a portion of a computing unit, in particular a computing unit with an artificial intelligence system. The sensor readings may then be sent directly to the portion of the computing unit included in the respective SAR reduction pad 1, which may locally generate control data, for example, to activate the distance generation means. If the computing unit comprises an artificial intelligence system, such as an artificial neural network, decision-making for even complex tasks, for which thresholds and manually determined logic or rules may not be appropriate, may be realized.

[0056] 8 shows a schematic cross section through a bore 15 of an MRI system 16. A patient 17 to be examined is placed inside the bore 15. Furthermore, SAR reduction pads 1 are attached to the inner walls of the bore 15, for example, using screws, hooks, Velcro, or snap fasteners. In one position, the patient's arms 18 are close to or in contact with the side walls of the bore 15. This can be determined by evaluation of a captured camera image of the patient 17 inside the bore 15 or by readings of pressure sensors, in particular pressure sensor 12 of the SAR reduction pad 1. In order to protect the skin and / or tissue of the patient 17 from overheating and / or burns, the distance generating means of the SAR reduction pad 1 are activated where the patient's arms 18 are close to or in contact with the side walls of the bore 15, moving the patient's arms 18 away from the side walls of the bore 15.

[0057] FIG. 9 shows a schematic cross section through the bore 15 of another embodiment of an MRI system 16. In this embodiment, the solid bore wall is omitted entirely. Instead, a frame structure 19 provides stability to the bore 15 of the MRI system 16, and a SAR reduction pad 1 having multiple chambers 5 is disposed inside the frame structure 19. In the illustrated embodiment, a tensioning mechanism 20 biases the SAR reduction pad 1 outward, thereby firmly securing the SAR reduction pad 1 inside the frame structure 19. The tensioning mechanism 20 can also be hydraulically, pneumatically, or mechanically actuated, for example. However, other methods of securing the SAR reduction pad 1 to the frame structure 19 can also be used. A thin wall of the bore 15 is provided as long as the chambers 5 of the SAR reduction pad 1 are contracted. However, the chambers 5 can be inflated to protect the patient's skin and / or tissue from overheating and / or burns.

[0058] Figure 10a shows a cross section of a cable 21 on which a SAR reduction pad 1 is placed. The cable 21 may, for example, be a power supply cable for a coil placed on the patient 17. When a risk of overheating and / or burns to the patient's skin and / or tissue is identified, the distance creating means of the SAR reduction pad 1 is activated, as shown in Figure 10b, to move the cable 21 further away from the patient 17 and protect the patient 17 from local overheating and / or burns.

[0059] 11 shows a cross-sectional view of yet another embodiment of an MRI system 16. SAR reduction pads 1 are attached to both side walls of the bore 15 and are placed on the patient 17, for example, attached to clothing worn by the patient 17. The MRI system 16 further includes a computing unit 22 and a camera 23. The camera 23 is connected to the computing unit 22, which can receive images taken by the camera. The SAR reduction pad 1 is further connected to the computing unit 22, which can transfer both sensor readings obtained by the sensor 12 of the SAR reduction pad 1 to the computing unit 22, and control commands for controlling the distance generating means can be sent by the computing unit 22 to the SAR reduction pad 1. Although a wired or optical connection between the computing unit 22 and the SAR reduction pad 1 is shown, a wireless connection is also possible. The computing unit 22 determines potential overheating of tissue of the patient 17 based on the images taken by the camera 23 and / or the sensor readings, and activates the distance generating means of the SAR reduction pad 1 to prevent such overheating.

[0060] FIG. 12 shows an example of the placement of SAR reduction pads 1 on the patient 17. To determine such placement, the computing unit 22 of the MRI system 16 can acquire data from a lidar unit having at least two cameras, a radar unit, and / or an optical positioning detection unit. Based on the data, as well as patient characteristics such as age, size, weight, and / or sedation state, and details of the MRI scan to be performed, the computing unit 22 determines the optimal placement of the SAR reduction pads 1. The placement can be depicted on the display of a user interface in a manner similar to the example shown in FIG. 12. The user can then place the SAR reduction pads 1 on the patient 17 according to the placement determined by the computing unit 22. This can be performed by a user with ordinary skills, and highly trained operator staff are no longer required.

[0061] FIG. 13 shows a schematic diagram of yet another embodiment of an MRI system 16. A computing unit 22 is connected to an MRI scanner 24, a SAR reduction pad 1, a camera 23, and a patient information database 25 of the MRI system 16. The MRI scanner 24 can provide information regarding the scheduled MRI scan sequence to the computing unit 22. The SAR reduction pad 1 may be attached to the sidewall of the bore 15, for example, or may be individually placed on the patient 17. Instead of or in addition to the camera 23, a radar unit, a lidar unit, and / or an optical positioning detection unit can also provide information to the computing unit 22. The patient information database 25 can include information about the patient 17, such as age, size, weight, and / or sedatives. Furthermore, the computing unit 22 can obtain information regarding coil placement and / or cable routing. Based on some or all of the provided information, the computing unit 22 can determine the optimal placement of the individually configurable SAR reduction pads 1, particularly the SAR reduction pads 1 to be placed on the patient 17. Positioning instructions for the determined positioning can then be presented to the user via a user interface, for example, on a display. Additionally, or alternatively, the computing unit 22 can selectively activate the distance generating means of the SAR reduction pads 1 based on some or all of the provided information. Furthermore, if the computing unit 22 determines that activation of the SAR reduction pads 1 is not sufficient to protect the skin and / or tissue of the patient 17 from local overheating and / or burns, the computing unit 22 can modify the MRI scan sequence and / or stop the MRI scan. Furthermore, the computing unit 22 can issue a warning, for example, a nurse call, when it determines abnormal patient behavior. Data obtained by the computing unit 22 can also be stored for further analysis, particularly offline analysis to further improve the MRI system 16.

[0062] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments.

[0063] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be interpreted as limiting their scope. [Explanation of symbols]

[0064] 1 SAR reduction pad 2 Pad body 3 First Surface 4 Second Surface 5 Chambers 6 Fluid Inlet 7 Mechanical distance generator 7.1 Plates 7.2 Hinge 7.3 Lead screw nuts 7.4 Screws 8 valves 9 Fluid outlet 10 valves 11 Microcontrollers 12 sensors 13 Interconnection Devices 14 Radio Transceiver 15 bore 16 MRI systems 17 patients 18 Arm 19 Frame structure 20 Extension mechanism 21 Cable 22 Computational Units 23 Camera 24 MRI scanners 25 Patient Information Database

Claims

1. A pad with reduced specific absorption rate (SAR), The pad itself, A first surface disposed on one side of the pad body, A second surface is located on the other side of the pad body, opposite to the first surface, At least one sensor configured to detect the value of an electromagnetic field, Distance generating means for increasing the distance between the first surface and the second surface, A SAR reduction pad having a distance generation means which is activated in response to receiving a command from a calculation unit when the detected electromagnetic field value reaches a predetermined threshold.

2. The distance generating means comprises at least one chamber filled with fluid and at least one fluid inlet fluidly connected to the at least one chamber, the SAR reduction pad according to claim 1.

3. The SAR reduction pad according to claim 2, wherein the distance generating means further comprises at least one valve disposed between the at least one fluid inlet and the at least one chamber.

4. The SAR reduction pad according to claim 2 or 3, wherein the distance generating means further comprises at least one fluid outlet fluid-connected to the at least one chamber for circulating the fluid through the at least one chamber.

5. The distance generating means comprises at least one mechanical distance generator, as described in any one of claims 1 to 3, for the SAR reduction pad.

6. The SAR reduction pad according to any one of claims 1 to 3, wherein the sensor comprises at least one of a pressure sensor, an electromagnetic field sensor, and / or a temperature sensor.

7. The SAR reduction pad according to any one of claims 1 to 3, wherein the SAR reduction pad further comprises an electrical, electronic, optical and / or wireless connector.

8. A magnetic resonance imaging (MRI) system, An MRI electronic device having at least one of a transmitting coil for transmitting a high-frequency (RF) signal, a receiving coil for receiving an RF signal, a receiving coil for sending and receiving RF signals, a cable, and a capacitor, Computing unit and A specific absorption rate (SAR) reduction pad according to any one of claims 1 to 3, An MRI system that has [a certain feature].

9. The MRI system according to claim 8, wherein the at least one SAR reduction pad is attached to the bore wall of the MRI system or to the side of the bore wall, constitutes at least a portion of the bore wall of the MRI system, is positioned around at least a portion of the MRI electronic equipment or cables, and / or is attachable to a patient.

10. The MRI system further includes a user interface, The MRI system according to claim 8, wherein the calculation unit is configured to determine the arrangement of the SAR reduction pads and to provide SAR reduction pad arrangement commands via the user interface.

11. The MRI system according to claim 8, wherein the calculation unit is configured to selectively activate the distance generation means based on sensor readings.

12. The MRI system according to claim 8, wherein the calculation unit is configured to issue a warning, modify the MRI scan sequence, and / or stop the MRI scan based on sensor readings.

13. The MRI system according to claim 8, wherein the computing unit has an artificial intelligence system or a trained machine learning system.

14. A method for operating the MRI system described in claim 8, The arrangement of the SAR reduction pads is determined by the calculation unit. The determined arrangement of the SAR reduction pads is provided to the user via the user interface. The SAR reduction pad is positioned by the user according to the determined arrangement of the SAR reduction pad. A method for performing an MRI scan and / or an MRI scan sequence.

15. The method according to claim 14, wherein sensor readings are acquired before and / or during the MRI scan and / or MRI scan sequence, and the distance generation means is selectively activated based on the acquired sensor readings.

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