Multi-channel pilot tone motion detection

Abstract

A medical system (100, 300, 500, 700) is disclosed, comprising: a memory (128) storing machine executable instructions (130); a processor (122) configured to control the medical system; and a pilot tone system (106). The pilot tone system comprises a radio frequency system (108), the radio frequency system comprising a plurality of transmit channels (110) and a plurality of receive channels (112). The plurality of transmit channels are configured to transmit unique pilot tone signals (132) via a plurality of transmit coils, respectively. The plurality of receive channels are configured to receive multi-channel pilot tone data (134) via a plurality of receive coils. Execution of the machine executable instructions causes the processor to: transmit (200) a multi-channel pilot tone signal by controlling at least a portion of the plurality of transmit channels to transmit the unique pilot tone signal; collect (202) the multi-channel pilot tone data by controlling at least a portion of the plurality of receive channels to receive the multi-channel pilot tone data (134); and determine (204) a motion state (136) of an object using the multi-channel pilot tone data.

Description

Technical Field

[0001] The present invention relates to tomographic medical imaging and, more particularly, to the detection of object motion using pilot tones. Background Art

[0002] In tomographic medical imaging techniques such as magnetic resonance imaging, X-ray computed tomography, positron emission tomography, etc., data is collected from a subject over a period of time and used to reconstruct a medical image. This enables a doctor or other healthcare professional to accurately image the internal anatomy of the subject. A disadvantage of these techniques is that the subject can move during the acquisition of the medical imaging data, which can result in artifacts in the medical image.

[0003] There are various techniques for correcting or compensating for object motion. One technique is the pilot tone technique. In magnetic resonance imaging, a transmit coil is used to transmit a radio frequency signal, and another receive coil is used to receive the signal. The amount of coupling between the object and the two coils determines the strength of the received signal. Motions such as heart motion, breathing motion, and whole body motion can be detected in the changes in signal strength.

[0004] US patent application publication US20150320342 A1 discloses a magnetic resonance device, which includes a radio frequency unit, which includes a radio frequency antenna, at least one radio frequency line, and at least one radio frequency injection point. The radio frequency signal is transmitted to the radio frequency antenna through at least one radio frequency line, and the radio frequency signal is coupled into the radio frequency antenna at at least one radio frequency injection point. The magnetic resonance device also includes a patient receiving area and a motion detection unit, wherein the patient receiving area is at least partially surrounded by the radio frequency antenna, and the motion detection unit is used to detect the movement of a patient who can be positioned in the patient receiving area. At least one radio frequency line includes at least one injection element, and at least one motion detection signal of the motion detection unit is coupled into the radio frequency line through the injection element.

[0005] US patent application US2015 / 002331 discloses a computed tomography system provided with a radar system.This known radar system is operative to detect motion in an examination region of the computed tomography system. Summary of the invention

[0006] The present invention provides, in one aspect, a medical system, a computer program product and a method. In another aspect, embodiments are provided.

[0007] Embodiments of the present invention may provide an improved pilot tone system. This may be achieved by using multiple transmit channels and multiple receive channels. Multiple transmit channels may be used to transmit a multi-channel pilot tone signal consisting of unique pilot tone signals. Multiple receive channels receive these signals as multi-channel pilot tone data. This provides much more information than a conventional pilot tone system. In the framework of the present invention, the pilot tone system is based on the transmission of a pilot tone signal as an electromagnetic signal in a radio frequency range of, for example, 40-400 MHz. The pilot tone signal is transmitted in a continuous wave (cw) mode, and the pilot tone data is generated due to an impedance response to the transmitted pilot tone signal. The response is represented by a change in the amplitude and phase of the pilot tone data relative to the amplitude and phase of the transmitted pilot tone signal. The pilot tone data represents a frequency domain response to the pilot tone signal, and the spectrum resolution information is carried by the pilot tone data.

[0008] In one aspect, the present invention provides a medical system. The medical system includes a memory storing machine executable instructions. The medical system also includes a processor configured to control the medical system. The medical system also includes a pilot tone system. The pilot tone system includes a radio frequency system. The radio frequency system includes multiple transmit channels and multiple receive channels. The multiple transmit channels are configured to transmit unique pilot tone signals via multiple transmit coils, respectively. The multiple receive channels are configured to receive pilot tone data via multiple receive coils. The multiple receive coils may be configured to receive the unique pilot tone signals.

[0009] The pilot tone data is an electrical signal generated by a unique pilot tone signal in multiple receiving channels. Execution of the machine executable instructions causes the processor to transmit a multi-channel pilot tone signal by controlling at least part of the transmitting channels to transmit the unique pilot tone signal. Execution of the machine executable instructions also causes the processor to collect the multi-channel pilot tone data by controlling at least part of the multiple receiving channels to receive the multi-channel pilot tone data. Execution of the machine executable instructions also causes the processor to use the multi-channel pilot tone data to determine the motion state of the object.

[0010] The motion state may describe the periodic motion of the object (e.g., breathing or heartbeat), and, in other examples, the motion state may describe the overall motion or whole body motion of the object. This embodiment may be beneficial because the motion state may be useful in monitoring the position or motion of the object during a medical procedure such as a tomographic imaging procedure.

[0011] In another embodiment, the radio frequency system is configured to encode each of the unique pilot tone signals using frequency encoding.

[0012] In another embodiment, the radio frequency system is configured to encode each of the unique pilot tone signals using phase encoding.

[0013] In another embodiment, the radio frequency system is configured to encode each of the unique pilot tone signals using complex modulation.

[0014] In another embodiment, the radio frequency system is configured to encode each of the unique pilot tone signals using CDMA encoding.

[0015] In another embodiment, the motion state of the object is any of the following: object motion position; motion vector; object motion classification; respiratory state; cardiac motion state; translation vector describing at least part of the object; rotation describing at least part of the object; and combinations thereof. This embodiment can be beneficial because these are all various steps and motions that can be tracked using a multi-channel pilot tone system.

[0016] In another embodiment, execution of the machine executable instructions further causes the processor to determine the motion state using a recurrent neural network configured to receive the multi-channel pilot tone data and the unique pilot tone signal and configured to output the motion state. The unique pilot tone signal is essentially a signal transmitted by multiple transmit channels, and the multi-channel pilot tone data is data received by multiple receive channels. These can all be input into a trained recurrent neural network to analyze time-dependent signals based on both. This can be useful in outputting the motion state.

[0017] In another embodiment, the machine executable instructions cause the processor to determine the motion state by detecting the distance between the object and each of the plurality of receiving coils. The plurality of receiving coils may be offset from the object by a certain distance. The strength of the signal may then be used to measure the distance between the object and the individual receiving coils. This enables the position of the object to be mapped using a simple model.

[0018] In another embodiment, execution of the machine executable instructions causes the processor to use a digital filter to determine the motion state. In a pilot tone system, a digital filter is relatively intuitive to detect periodic motion. For example, motion due to the heart has a frequency component similar to the frequency of a beating heart. A digital filter can then be used to isolate this signal from the heartbeat. Similarly, motion of the subject due to breathing will also cause a frequency component similar to the subject's breathing rate. Thus, a digital filter simply enables the determination of certain types of periodic motion.

[0019] In another embodiment, execution of the machine executable instructions causes the processor to determine the motion state using principal component analysis.This machine learning technique is effective in detecting various types of signals that may be indicative of motion.

[0020] In another embodiment, the medical system further comprises a magnetic resonance imaging system.

[0021] In another embodiment, the magnetic resonance imaging system further comprises a magnetic resonance imaging coil. The magnetic resonance imaging coil comprises a plurality of pilot tone transmitting coils and a plurality of receiving coils. This embodiment may be beneficial because the pilot tone transmitting coil and the plurality of receiving coils may be easily integrated into the magnetic resonance imaging coil.

[0022] In another embodiment, the magnetic resonance imaging system is further configured to acquire magnetic resonance imaging data within an imaging frequency range. The plurality of transmit channels are configured to transmit the unique pilot tone signal outside the imaging frequency range. This may be beneficial because the electromagnetic signal used by the pilot tone signal does not interfere with the acquisition of magnetic resonance imaging data. This may, for example, enable simultaneous acquisition of magnetic resonance imaging data and operation of the pilot tone signal.

[0023] In another embodiment, the memory further comprises pulse sequence commands, the pulse sequence commands being configured to control the magnetic resonance imaging system to acquire magnetic resonance imaging data. Execution of the machine executable instructions further causes the processor to control the magnetic resonance imaging system to acquire the magnetic resonance imaging data using the pulse sequence commands. Execution of the machine executable instructions causes the processor to perform the following operations during control of the magnetic resonance imaging system using the pulse sequence commands: transmitting the multi-channel pilot tone signal; acquiring the multi-channel pilot tone data; and using the multi-channel pilot tone data to determine the motion state of the object. This embodiment is beneficial because the motion state determined from the pilot tone system can be used to simultaneously control the acquisition of the magnetic resonance imaging system and / or motion correction of the magnetic resonance imaging data later.

[0024] In another embodiment, execution of the machine executable instructions further causes the processor to determine a current gradient pulse frequency using the pulse sequence command. The current gradient pulse frequency is the frequency at which the gradient coil is currently oscillating. Execution of the machine executable instructions further causes the processor to detect subject motion having a periodicity within a predetermined range of the current gradient pulse frequency using a motion state derived from the multi-channel pilot tone data. Execution of the machine executable instructions further causes the processor to provide a peripheral nerve stimulation warning signal if the subject motion is detected.

[0025] The gradient coils in a magnetic resonance imaging system can generate an electric current or electric field in a subject. This can cause so-called peripheral nerve stimulation and cause the muscle tissue of the subject to move. In this embodiment, the frequency of the generated gradient pulses is compared with the multi-channel pilot tone data. If a frequency component is determined to be above a predetermined threshold, this can indicate peripheral nerve stimulation of the subject being examined. The frequency can also be compared or correlated with the actual gradient signal. This can be used to further increase the confidence that peripheral nerve stimulation has occurred.

[0026] In another embodiment, execution of the machine executable instructions further causes the processor to select an alternative pulse sequence command in the event that the peripheral nerve stimulation warning signal is provided. For example, a medical system may have a set of different pulse sequence commands that can be used, and in the event that peripheral nerve stimulation is detected using the system, the system may select an alternative pulse sequence command.

[0027] In another embodiment, execution of the machine executable instructions further causes the processor to modify the pulse sequence command if the peripheral nerve stimulation warning signal is provided. For example, the processor may cause the frequency or intensity of individual gradient pulses to be modified.

[0028] In another embodiment, execution of the machine executable instructions further causes the processor to cancel execution of the pulse sequence command if the peripheral nerve stimulation warning signal is provided. For example, if the peripheral nerve stimulation warning signal is above a critical threshold or a danger threshold, the system can automatically terminate the acquisition of magnetic resonance imaging data.

[0029] The pilot tone system also includes the plurality of transmit coils and the plurality of receive coils.

[0030] In another embodiment, the medical system further comprises a tomographic imaging system configured to acquire tomographic imaging data from an object within an imaging zone. Execution of the machine executable instructions further causes the processor to control the tomographic imaging system to acquire the tomographic imaging data. Execution of the machine executable instructions causes the processor to perform the following operations during control of the tomographic imaging system to acquire the tomographic imaging data: transmit the multi-channel pilot tone signal; acquire the multi-channel pilot tone data; and use the multi-channel pilot tone data to determine the motion state of the object. This embodiment may be beneficial because, in addition to being applied only to magnetic resonance imaging, pilot tones may also be applied to other imaging modalities.

[0031] In another embodiment, execution of the machine executable instructions further causes the processor to reconstruct a medical image using the tomographic imaging data. Execution of the machine executable instructions further causes the processor to use the motion state of the object to correct the reconstruction of the medical image. For example, if the motion state or position of the object is known, this can assist in reconstructing the medical image to compensate for the motion of the object.

[0032] In another embodiment, the tomographic imaging system is a positron emission tomography system.

[0033] In another embodiment, the tomographic imaging system is a single photon emission tomography system.

[0034] In another embodiment, the tomographic imaging system is an X-ray computed tomography system.

[0035] In another embodiment, the tomographic imaging system comprises an object support for supporting at least part of the object in the imaging zone. At least part of the plurality of transmit coils and at least part of the plurality of receive coils are integrated into the object support. This may be beneficial because this may provide an effective means of integrating a pilot tone signal into a tomographic imaging system that is different from a magnetic resonance imaging system.

[0036] In one aspect, the present invention provides a computer program product comprising machine executable instructions, the machine executable instructions being executed by a processor controlling a medical system. The medical system comprises a pilot tone system. The pilot tone system comprises a radio frequency system, the radio frequency system comprising a plurality of transmit channels and a plurality of receive channels. The plurality of transmit channels are configured to transmit a unique pilot tone signal each via a plurality of transmit coils. The plurality of receive channels are configured to receive multi-channel pilot tone data via a plurality of receive coils. Execution of the machine executable instructions causes the processor to transmit a multi-channel pilot tone signal by controlling at least a portion of the plurality of transmit channels to transmit the unique pilot tone signal.

[0037] Execution of the machine executable instructions causes the processor to collect the multi-channel pilot tone data by controlling at least part of the plurality of receiving channels to receive the multi-channel pilot tone data. Execution of the machine executable instructions causes the processor to use the multi-channel pilot tone data to determine a motion state of an object.

[0038] In another aspect, the present invention provides a method of operating a medical system. The medical system includes a pilot tone system. The pilot tone system includes a radio frequency system, and the radio frequency system includes multiple transmit channels and multiple receive channels. The multiple transmit channels are configured to transmit unique pilot tone signals via multiple transmit coils respectively. The multiple receive channels are configured to receive multi-channel pilot tone data via multiple receive coils. The method includes transmitting a multi-channel pilot tone signal by controlling at least part of the multiple transmit channels to transmit the unique pilot tone signal. The method also includes collecting the multi-channel pilot tone data by controlling at least part of the multiple receive channels to receive the multi-channel pilot tone data. The method also includes using the multi-channel pilot tone data to determine the motion state of an object.

[0039] In an example, a magnetic resonance imaging system includes: a memory storing machine executable instructions; and a pulse sequence command configured to control the magnetic resonance imaging system to acquire magnetic resonance imaging data. The magnetic resonance imaging system also includes a processor configured to control the magnetic resonance imaging system to acquire magnetic resonance imaging data. The magnetic resonance imaging system also includes a pilot tone system. The pilot tone system includes a radio frequency system including at least one transmit channel and at least one receive channel. The plurality of receive channels are configured to receive the pilot tone data via the at least one transmit channel.

[0040] Execution of the machine executable instructions further causes the processor to transmit at least one pilot tone signal by controlling at least one transmit channel. Execution of the machine executable instructions further causes the processor to collect pilot tone data by controlling at least one receive channel to receive pilot tone data. Execution of the machine executable instructions further causes the processor to use the pilot tone data to determine a motion state of the object. Execution of the machine executable instructions further causes the processor to use the pulse sequence command to determine a current gradient pulse frequency. Execution of the machine executable instructions further causes the processor to use the pilot tone data to detect object motion having a periodicity within a predetermined range of the current gradient pulse frequency.

[0041] Execution of the machine executable instructions also causes the processor to provide a peripheral nerve stimulation warning signal if subject motion is detected. There may also be a threshold for determining whether the subject motion is above a certain critical level or predetermined motion level that would require intervention from an operator or physician. Subject motion can also be detected by determining a correlation between the subject's motion state and current or actual gradient pulses generated by the gradient coils of the magnetic resonance imaging system. This embodiment may be beneficial because it may provide a means of automatically detecting whether the subject has motion due to peripheral nerve stimulation. This may, for example, improve the safety of the magnetic resonance imaging system and may be useful in improving image quality because the subject's motion is reduced.

[0042] In another embodiment, execution of the machine executable instructions further causes the processor to provide any of the following if a peripheral nerve stimulation warning is provided: selecting an alternative pulse sequence command; modifying the pulse sequence command; canceling execution of the pulse sequence command; and displaying a visible signal or an audible signal.

[0043] In another embodiment, the magnetic resonance imaging system further comprises a magnetic resonance imaging coil. The magnetic resonance imaging coil comprises at least one pilot tone transmit coil and at least one receive coil. In another embodiment, the magnetic resonance imaging system comprises a subject support, and at least parts of the at least one pilot tone transmit coil and the at least one receive coil are integrated into the subject support.

[0044] In another embodiment, the magnetic resonance imaging system is configured to acquire magnetic resonance imaging data within an imaging frequency range. A plurality of transmit channels are configured to transmit a unique pilot tone signal outside the imaging frequency range. This can be beneficial because the operation of the pilot tone system does not interfere with the acquisition of magnetic resonance imaging data.

[0045] In another embodiment, the at least one transmit channel is a plurality of transmit channels.

[0046] In another embodiment, the at least one receiving channel is a plurality of receiving channels.

[0047] In another embodiment, the at least one transmit channel is a single transmit channel.

[0048] In another embodiment, the at least one receive channel is a single receive channel.

[0049] It should be understood that one or more of the aforementioned embodiments of the present invention may be combined as long as the combined embodiments are not mutually exclusive.

[0050] Those skilled in the art will appreciate that aspects of the present invention may be implemented as devices, methods, or computer program products. Therefore, aspects of the present invention may take the form of a complete hardware embodiment, a complete software embodiment (including firmware, resident software, microcode, etc.), or an embodiment that combines software and hardware aspects, all of which are generally referred to herein as "circuits," "modules," or "systems." In addition, aspects of the present invention may take the form of a computer program product implemented in one or more computer-readable media having a computer executable code implemented thereon.

[0051] Any combination of one or more computer-readable media can be utilized. A computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium. As used herein, "computer-readable storage medium" encompasses any tangible storage medium that can store instructions that can be executed by a processor of a computing device. A computer-readable storage medium can be referred to as a computer-readable non-transient storage medium. A computer-readable storage medium can also be referred to as a tangible computer-readable medium. In some embodiments, a computer-readable storage medium can also store data that can be accessed by a processor of a computing device. Examples of computer-readable storage media include, but are not limited to, floppy disks, magnetic hard disk drives, solid-state hard disks, flash memories, USB thumb drives, random access memories (RAM), read-only memories (ROM), optical disks, magneto-optical disks, and register files of processors. Examples of optical disks include compact disks (CDs) and digital versatile disks (DVDs), such as CD-ROMs, CD-RWs, CD-Rs, DVD-ROMs, DVD-RWs, or DVD-R disks. The term "computer-readable storage medium" also refers to various types of recording media that can be accessed by a computer device via a network or communication link. For example, data can be retrieved on a modem, on the Internet, or on a local area network. Computer executable code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

[0052] A computer readable signal medium may include, for example, a propagated data signal in which a computer executable code is implemented, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electromagnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that is capable of conveying, propagating, or transmitting a program for use by or in conjunction with an instruction execution system, apparatus, or device.

[0053] "Computer memory" or "memory" is an example of a computer-readable storage medium. Computer memory is any memory that can be directly accessed by a processor. "Computer storage" or "storage device" is another example of a computer-readable storage medium. A computer storage device is any non-volatile computer-readable storage medium. In some embodiments, a computer storage device may also be computer memory, or vice versa.

[0054] As used herein, "processor" encompasses an electronic component capable of running a program or machine executable instructions or computer executable code. References to computing devices including "processors" should be interpreted as possibly including more than one processor or processing core. The processor may be, for example, a multi-core processor. A processor may also refer to a collection of processors within a single computer system or distributed between multiple computer systems. The term "computing device" should also be interpreted as possibly referring to a collection or network of multiple computing devices, each of which includes one or more processors. Computer executable code may be executed by multiple processors that may be within the same computing device or may even be distributed on multiple computing devices.

[0055] Computer executable code may include machine executable instructions or programs that cause a processor to perform an aspect of the present invention. Computer executable code for performing operations for various aspects of the present invention may be written in any combination of one or more programming languages, including object-oriented programming languages ​​(e.g., Java, Smalltalk, C++, etc.) and conventional procedural programming languages ​​(e.g., "C" programming language or similar programming languages), and compiled into machine executable instructions. In some instances, the computer executable code may be in the form of a high-level language or in a precompiled form, and may be used in conjunction with an interpreter that generates machine executable instructions during operation.

[0056] The computer executable code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer, or entirely on a remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., through the Internet using an Internet service provider).

[0057] Various aspects of the present invention are described with reference to flowchart illustrations and / or block diagrams of methods, devices (systems) and computer program products according to embodiments of the present invention. It should be understood that each frame or part of the frame of a flowchart, diagram and / or block diagram can be implemented by a computer program instruction in the form of computer executable code when appropriate. It should also be understood that when mutually non-exclusive, the frames in different flowcharts, diagrams and / or block diagrams can be combined. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer or other programmable data processing device to produce a machine, so that the instructions executed by the processor of a computer or other programmable data processing device create a unit for implementing the function / action specified in one or more frames of a flowchart and / or block diagram.

[0058] These computer program instructions may also be stored in a computer-readable medium that can direct a computer, other programmable data processing apparatus, or other device to function in a specific manner so that the instructions stored in the computer-readable medium produce an article of manufacture that includes instructions for implementing the functions / actions specified in the flowchart and / or one or more block diagram blocks.

[0059] The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus, or other devices, thereby producing a computer-implemented process, such that the instructions running on the computer or other programmable apparatus provide a process for implementing the functions / actions specified in the flowchart and / or one or more block diagram blocks.

[0060] "User interface" used herein is an interface that allows a user or operator to interact with a computer or computer system. "User interface" may also be referred to as a "human-machine interface device". A user interface may provide information or data to an operator and / or receive information or data from an operator. A user interface may enable the input from an operator to be received by the computer, and may provide output to a user from the computer. In other words, a user interface may allow an operator to control or manipulate a computer, and an interface may allow a computer to indicate the effect of the control or manipulation of an operator. Displaying data or information on a display or graphical user interface is an example of providing information to an operator. Receiving data by a keyboard, mouse, tracking ball, touch pad, pointing stick, graphic input board, joystick, game controller, webcam, head mounted device, foot pedal, wired gloves, remote controller, and accelerometer is all examples of user interface components that enable receiving information or data from an operator.

[0061] "Hardware interface" as used herein encompasses an interface that enables a processor of a computer system to interact with and / or control an external computing device and / or apparatus. A hardware interface may allow a processor to send a control signal or instruction to an external computing device and / or apparatus. A hardware interface may also enable a processor to exchange data with an external computing device and / or apparatus. Examples of hardware interfaces include, but are not limited to, a universal serial bus, an IEEE 1394 port, a parallel port, an IEEE 1284 port, a serial port, an RS-232 port, an IEEE-488 port, a Bluetooth connection, a wireless LAN connection, a TCP / IP connection, an Ethernet connection, a control voltage interface, a MIDI interface, an analog input interface, and a digital input interface.

[0062] As used herein, a "display" or "display device" encompasses an output device or user interface suitable for displaying images or data. A display may output visual, auditory, and / or tactile data. Examples of displays include, but are not limited to: a computer monitor, a television screen, a touch screen, a tactile electronic display, a Braille screen, a cathode ray tube (CRT), a memory tube, a bi-stable display, an electronic paper, a vector display, a flat panel display, a vacuum fluorescent display (VF), a light emitting diode (LED) display, an electroluminescent display (ELD), a plasma display panel (PDP), a liquid crystal display (LCD), an organic light emitting diode display (OLED), a projector, and a head mounted display.

[0063] Medical image data is defined herein as two-dimensional or three-dimensional data that has been acquired using a medical imaging scanner. A medical imaging scanner is defined herein as being suitable for acquiring information about a patient's body structure and constructing a collection of two-dimensional or three-dimensional medical image data. The medical image data can be used to construct visualizations that are useful to a physician for diagnosis. Such visualizations can be performed using a computer.

[0064] Magnetic resonance (MR) data is defined herein as the measurement of radio frequency signals emitted by atomic spins recorded using the antenna of a magnetic resonance device during a magnetic resonance imaging scan. Magnetic resonance data is an example of medical image data. A magnetic resonance imaging (MRI) image or MR image is defined herein as a two-dimensional or three-dimensional visualization reconstructed from anatomical data contained within the magnetic resonance imaging data. Such visualization can be performed using a computer. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0066] Figure 1 An example of a medical system is illustrated;

[0067] Figure 2 The diagram shows the operation Figure 1 A flowchart of a method of a medical system;

[0068] Figure 3 Further examples of medical systems are illustrated;

[0069] Figure 4 The diagram shows the operation Figure 3 A flowchart of a method of a medical system;

[0070] Figure 5 Further examples of medical systems are illustrated;

[0071] Figure 6 The diagram shows the operation Figure 5 A flowchart of a method of a medical system;

[0072] Figure 7 Further examples of medical systems are illustrated;

[0073] Figure 8 The diagram shows the operation Figure 5 A flowchart of a method of a medical system;

[0074] Fig. 9 An example of multi-channel pilot tone data is shown;

[0075] Fig.10 Shown according to Fig. 9 An example of a motion state derived from multi-channel pilot tone data;

[0076] Fig.11 An example of a combined MRI and pilot tone coil is illustrated;

[0077] Fig.12 illustrates an example of a software system for a medical system; and

[0078] Fig.13 Further examples of software systems for medical systems are illustrated.

[0079] Reference numerals list

[0080] 100 Medical System

[0081] 102 Objects

[0082] 104 Object Support

[0083] 106 Pilot Tone System

[0084] 108 RF System

[0085] 108' individual radio frequency system

[0086] More than 110 transmission channels

[0087] 110' At least one transmission channel

[0088] More than 112 receiving channels

[0089] 112'At least one receiving channel

[0090] 114+ transmitting coils

[0091] 114' at least one transmitting coil

[0092] 116+ receiving coils

[0093] 116' at least one receiving coil

[0094] 120 Computer

[0095] 122 processors

[0096] 124 Hardware Interface

[0097] 126 User Interface

[0098] 128 Memory

[0099] 130 machine executable instructions

[0100] 132 Unique pilot tone signal

[0101] 132'One or more pilot tone signals

[0102] 134 multi-channel pilot tone data

[0103] 134' Pilot tone data

[0104] 136 Movement Status

[0105] 138 Recurrent Neural Networks

[0106] 200 transmits a unique pilot tone signal by controlling at least part of the plurality of transmission channels to transmit

[0107] Multi-channel pilot tone signal

[0108] 202 collects the multi-channel pilot tone data by controlling at least part of the multiple receiving channels to receive the multi-channel pilot tone data

[0109] Multi-channel pilot tone data

[0110] 204 Using multi-channel pilot tone data to determine the motion state of the object

[0111] 300 Medical System

[0112] 302 Tomography Imaging System

[0113] 304 Imaging Area

[0114] 310 Control Command

[0115] 312 Tomographic imaging data

[0116] 314 Tomographic Medical Images

[0117] 400 Acquiring tomographic imaging data from an object within an imaging region

[0118] 500 Medical Imaging Systems

[0119] 502 Magnetic Resonance Imaging System

[0120] 504 Magnet

[0121] 506 Magnet bore

[0122] 508 Imaging Area

[0123] 509 Area of ​​Interest

[0124] 510 Magnetic Field Gradient Coil

[0125] 512 Magnetic Field Gradient Coil Power Supply

[0126] 514 Magnetic Resonance Antenna

[0127] 516 RF Coil

[0128] 530 Pulse sequence command

[0129] 532 MRI data

[0130] 534 Magnetic Resonance Images

[0131] 600 Acquisition of MRI Data

[0132] 700 Medical Systems

[0133] 710 Time-dependent gradient pulse frequency

[0134] 712 Peripheral nerve irritation warning signs

[0135] 800 Use pulse sequence command to determine current gradient pulse frequency

[0136] 802 uses the pilot tone data to detect a frequency within a predetermined range of the current gradient pulse frequency.

[0137] Periodic object motion

[0138] 804 provides a peripheral nerve stimulation warning signal when subject motion is detected

[0139] 1000 Synthesized heart signal

[0140] 1002 Synthesized breathing signal

[0141] 1100 combined MR and pilot tone coil

[0142] 1102 Coil

[0143] 1104 Digital Transmitter

[0144] 1106 Pilot Tone Digital Receiver

[0145] 1108 Antenna pilot tone

[0146] 1110 Controller

[0147] 1112 Optical communications DETAILED DESCRIPTION

[0148] In the drawings, components with the same reference numerals are either equivalent elements or perform the same function. If the function is equivalent, it will not be necessary to discuss previously discussed elements in subsequent drawings.

[0149] Figure 1 An example of a medical system 100 is illustrated. The medical system 100 is shown examining a subject 102. The subject 102 is shown on a subject support 104. The subject support 104 is optional. The medical system 100 includes a pilot tone system 106. The pilot tone system has a radio frequency system 108 having a plurality of transmit channels 110 and a plurality of receive channels 112. The plurality of transmit channels 110 are connected to a plurality of transmit coils 114. The plurality of receive channels 112 are connected to a plurality of receive coils 116. The medical system 100 is also shown to include a computer 120 that includes a processor 122. The processor 122 is intended to represent one or more processors.

[0150] The processor 122 may, for example, represent multiple processing cores and processors 122 distributed in multiple computer systems. The processor 122 is connected to a hardware interface 124, which enables the processor 122 to control other components of the medical system 100. The hardware interface 124 may also, for example, be used as a network interface and enables the processor 122 to communicate with other processors and / or computer systems. The computer 120 is also shown to include an optional user interface 126, which may, for example, be used by an operator to control the medical system 100. The computer 120 is also shown to include a memory 128.

[0151] Memory 128 may be any combination of memory accessible by processor 122. This may include memory such as main memory, cache memory, and may also include non-volatile memory such as flash RAM, hard drive, or other storage devices. In some examples, memory 128 may be considered a non-transitory computer-readable medium.

[0152] The memory 128 is shown as containing machine executable instructions 130. The machine executable instructions 130 enable the processor 122 to control the operation and function of the medical system 100. The machine executable instructions 130 may also, for example, enable the processor 122 to perform various data analysis and image processing techniques. The memory 128 is also shown as containing a unique pilot tone signal 132 that has been constructed for each of the multiple transmit channels 110. For example, the unique pilot tone signal 132 can be transmitted to the radio frequency system 108 via the processor 122 for transmission. The memory 128 is also shown as containing multi-channel pilot tone data 134. The multi-channel pilot tone data 134 is digitized data recorded by the multiple receive channels 112. The transmit channels transmit unique pilot tone signals 132, and this causes some portions of these signals to be received in the receive channels. This is the multi-channel pilot tone data 134.

[0153] The combination of the unique pilot tone signals 132 results in a multi-channel pilot tone signal that is transmitted together. The memory 128 is also shown as containing a motion state 136 that has been calculated using the multi-channel pilot tone data 134 and the unique pilot tone signal 132 or the multi-channel pilot signal. The motion state 136 can be calculated using a variety of different models for signal processing techniques. As an example, the memory 128 is shown as containing a recurrent neural network 138. The recurrent neural network 138 receives the unique pilot tone signal 132, and the multi-channel pilot tone data 134 is input, and then the recurrent neural network 138 outputs the motion state 136.

[0154] exist Figure 1 In one example, components of the pilot tone system are also integrated into the object support. For example, the pilot tone system can be completely contained within the object support. This can be achieved, for example, by using the object support to add the pilot tone system to a medical imaging system such as an MRI system or an X-ray system. The object support can also be used for different imaging techniques, for example, magnetic resonance imaging. A single object support can be moved to different imaging systems and different types of imaging systems.

[0155] Figure 2 The diagram shows the operation Figure 1 Flow chart of a method of a medical system 100 of the present invention. First, in step 200, a multi-channel pilot tone signal 132 is transmitted by controlling at least part of the plurality of transmission channels 110. The multi-channel pilot tone signal is formed by the individual unique pilot tone signals 132. Next, in step 202, multi-channel pilot tone data 134 is collected by controlling at least part of the plurality of reception channels 112.

[0156] Finally, in step 204, the motion state 136 of the object 102 is determined using the multi-channel pilot tone data 134. In the case of the recurrent neural network 138, both the multi-channel pilot tone data 134 and the individual unique pilot tone signal 132 are likely to be input. In other cases, the motion state 136 can be determined based on the multi-channel pilot tone data 134 alone. For example, the periodic respiratory motion or cardiac motion of the object 102 can cause the multi-channel pilot tone data 134 to have a frequency component that is equal to or approximately equal to the heart rate and / or respiratory rate. Therefore, the cardiac motion and / or respiratory motion can be determined by the multi-channel pilot tone data 134 alone.

[0157] Figure 3 A further example of a medical system 300 is illustrated. Figure 3 The medical system 300 in is similar to Figure 1 304. The medical system 300 is shown in FIG. 300 , except that the medical system 300 additionally includes a tomographic imaging system 302. The tomographic imaging system can be, for example, a positron emission tomography system, a single photon emission tomography system, or an X-ray computed tomography system. In this example, the tomographic imaging system 302 has cylindrical symmetry; however, this is not a requirement. The object support 104 is shown as supporting a portion of the object 102 within an imaging zone 304. The imaging zone 304 is a location in space in which the tomographic imaging system 302 can acquire tomographic imaging data 312.

[0158] The memory 128 is also shown as containing control commands 310 that enable the processor 122 to control the tomographic imaging system 302 to acquire tomographic imaging data 312. The memory 128 is also shown as containing the tomographic imaging data 312 acquired by controlling the tomographic imaging system 302 using the control commands 310. The memory 128 is also shown as containing a tomographic medical image 314 reconstructed from the tomographic imaging data 312. For example, the multi-channel pilot tone data 134 can be acquired while the tomographic imaging data 312 is being acquired. This enables various means that can be used to account for the motion of the object 102. For example, the multi-channel pilot tone data 134 and the resulting motion state 136 can be used to gate the acquisition of the tomographic imaging data 312. In other examples, the motion of the object 102 can be determined in more detail, and the motion state 136 can be used during the reconstruction of the tomographic medical image 314.

[0159] Figure 4 The diagram shows the operation Figure 3 First, in step 400, the processor 122 controls the tomographic imaging system 302 using the control command 310. At the same time, the following steps are executed: Figure 2Steps 200, 202 and 204 are shown.

[0160] Figure 5 A further example of a medical system 500 is illustrated. Figure 5 The medical system in Figure 3 The medical system 300 in FIG. 1 is different in that the tomographic imaging system is specifically a magnetic resonance imaging system 502 .

[0161] The magnetic resonance imaging system 502 includes a magnet 504. The magnet 504 is a superconducting cylindrical type magnet having a bore 506 passing therethrough. Different types of magnets may also be used; for example, split cylindrical magnets and so-called open magnets may also be used. A split cylindrical magnet is similar to a standard cylindrical magnet, except that the cryostat has been divided into two parts to allow access to the isoplane of the magnet, such a magnet may be used, for example, in conjunction with charged particle beam therapy. An open magnet has two magnet parts, one above the other, with a space between the two magnets sufficient to receive a subject: the area arrangement of the two parts is similar to a Helmholtz coil. Open magnets are popular because the subject is less constrained. Inside the cryostat of the cylindrical magnet there is a collection of superconducting coils.

[0162] Within the bore 506 of the cylindrical magnet 504 is an imaging zone 508 in which the magnetic field is sufficiently strong and uniform to perform magnetic resonance imaging. A region of interest 509 is shown within the imaging zone 508. Magnetic resonance imaging data is typically acquired for the region of interest. The subject 102 is shown supported by the subject support 104 so that at least a portion of the subject 102 is within the imaging zone 508 and the region of interest 509.

[0163] Also provided within the bore 506 of the magnet is a collection of magnetic field gradient coils 510 for collecting preliminary magnetic resonance imaging data to spatially encode magnetic spins within the imaging zone 508 of the magnet 504. The magnetic field gradient coils 510 are connected to a magnetic field gradient coil power supply 512. The magnetic field gradient coils 510 are intended to be representative. Typically, the magnetic field gradient coils 510 include three independent coil sets, which are used to perform spatial encoding in three orthogonal spatial directions. The magnetic field gradient power supply supplies current to the magnetic field gradient coils. The current supplied to the magnetic field gradient coils 510 is controlled according to time and the current can be ramped or pulsed.

[0164] Within the bore 506 of the magnet 504 is a magnetic resonance imaging antenna 514. The magnetic resonance imaging antenna 514 is shown to include a plurality of transmit coils 114 and a plurality of receive coils 116. The magnetic resonance imaging antenna 514 also includes a plurality of radio frequency coils 516, which are used to perform magnetic resonance imaging. The radio frequency system 108 is also connected to the radio frequency coils 516. Figure 5 The arrangement shown enables acquisition of magnetic resonance imaging data while using a pilot tone system. In other examples, the radio frequency coil 516 may also be used as multiple transceiver coils 114 and / or multiple receive coils 116 .

[0165] The radio frequency coil 516 may also be referred to as a channel or antenna. The magnetic resonance antenna 514 is connected to the radio frequency system 108. The magnetic resonance antenna 514 and the radio frequency system 108 may be replaced with separate transmit and receive coils and separate transmitters and receivers. It should be understood that the magnetic resonance antenna 514 and the radio frequency system 108 are representative. The magnetic resonance antenna 514 is intended to also represent a dedicated transmit antenna and a dedicated receive antenna. Likewise, the radio frequency coil 516 may also represent a separate transmitter and receiver. The magnetic resonance antenna 514 may also have multiple receive / transmit elements, and the radio frequency system 108 may have multiple receive / transmit channels. For example, if a parallel imaging technique such as SENSE is performed, the radio frequency system 108 may have multiple coil elements.

[0166] The radio frequency system 108 and the magnetic field gradient coil power supply 512 are shown as being connected to the hardware interface 124 of the computer system 128. The memory 128 is shown as containing pulse sequence commands 530 instead of control commands. The pulse sequence commands 530 are commands for controlling the operation of the magnetic resonance imaging system 502 or data that can be converted into such commands. The memory 128 is also shown as containing magnetic resonance imaging data 532 acquired by controlling the magnetic resonance imaging system using the pulse sequence commands 530.

[0167] The memory 128 is also shown as containing a magnetic resonance image 534 reconstructed from the magnetic resonance imaging data 532. Figure 3 As with the medical system 300 in FIG. 5 , the motion state 136 may be used in different ways. For example, the motion state 136 may be used to gate the acquisition of magnetic resonance imaging data 532 and may be used in the reconstruction of a magnetic resonance image 534 .

[0168] Figure 6 Graphically shows the control Figure 5 First, in step 600, the magnetic resonance imaging system 502 is controlled to acquire magnetic resonance imaging data 532 using a pulse sequence command 530. When step 600 is executed, the command from Figure 2 Steps 200, 202 and 204.

[0169] Figure 7 A further example of a medical system 700 is illustrated. Figure 7 The medical system in Figure 5 Medical system. However, there are several variations. The plurality of transmit coils 114 may also be at least one transmit coil 114'. The plurality of receive coils may be at least one receive coil 116'. Likewise, the plurality of receive channels may be at least one receive channel 112', and the plurality of transmit coils may be at least one transmit coil 114'.

[0170] The memory 128 may also include a time-dependent gradient pulse frequency 710 determined from the pulse sequence command 530. The motion state 136 may be compared to the time-dependent gradient pulse frequency 710 to determine whether peripheral nerve stimulation is present in the subject 102. If the motion state is correlated with the detected motion above a certain degree or above a certain magnitude within the same frequency range, a peripheral nerve stimulation warning signal 712 may be generated.

[0171] Figure 8 The diagram shows the operation Figure 7 Flow chart of a method of a medical system 700. The method is similar to Figure 6 To get started, Figure 6 Steps 600, 200, 202, 204 are performed as in . After performing step 204 or before performing step 800, the pulse sequence command 530 is used to determine the time-dependent gradient pulse frequency 710. Next, in step 802, the motion state 136 is used to detect the object motion with periodicity within a predetermined range or the object motion with correlation with the time-dependent gradient pulse frequency. For example, the motion state can be compared with the time-dependent gradient pulse frequency 710, or the correlation can be calculated, for example, on the fly. Finally, in step 804, a peripheral nerve stimulation warning signal 712 is generated in the event that the object motion is detected.

[0172] Some examples may be distributed pilot / reference signals in the coil array or antenna of a magnetic resonance imaging system. A complete digital pilot tone integration is obtained in the receive array. The optimal pilot signal is selected by the transmit matrix and the receive matrix. The individual pilot tones can be different in frequency-phase-complex modulation.

[0173] For autonomous imaging, this enables ECG-free heartbeat detection as well as separation and quantification of head-body motion in combination with camera-based approaches.

[0174] Both MRI scans and CT scans may require many input parameters and appropriate scan preparation. Depending on the size, weight, position of the patient to be scanned and the anatomy, the protocol is selected and modified to fit the patient. Typically, this data is entered manually. Special sensors can be used to measure physiological parameters (e.g., necessary for triggering the scan). Recently, it has been demonstrated that the relevant parameters can be derived from a live video stream from a camera viewing the patient during the scan.

[0175] During the MRI procedure, the patient is covered by clothing and, for most applications, by RF coils (e.g., head coil and / or (anterior) surface coil). The pilot tone method can be used as a contactless electromagnetic navigator that can monitor cardiac and respiratory motion independently of the acquisition.

[0176] Examples may have one or more of the following benefits:

[0177] Heartbeat detection without ECG

[0178] Separation and quantification of head-body motion

[0179] Export triggers for cardiac and respiratory motion

[0180] Application of MR LINAC-radiotherapy

[0181] Considering the sheer number of parameters as well as the nonlinear (amplifier gain, fixed parameter limits) interdependencies of parameters, it can be difficult to analytically optimize dozens of input and output parameters from an RF sensor within a given time frame.

[0182] Camera-based motion detection systems suffer from distribution issues in the compact bores of current MR and CT scanners. On the other hand, a single source / receiver pilot tone system is only suitable for serving one function. Patient diversity and parameter requirements make it difficult to optimize a single pilot tone system.

[0183] The signal-to-noise ratio depends on the location of the pilot tone antenna / coil. In experiments, it was determined that multiple channels can be beneficial for extracting different types and directions of head motion, requiring multiple pilot tone sources distributed around the head / subject. Using multiple channels can provide one or more of the following features or benefits:

[0184] Fixed frequency crystal oscillator

[0185] Additional Parts

[0186] Localization of pilot transmitters

[0187] For cardiac sensing / respiratory restricted applications

[0188] Workflow: Additional steps for your workflow

[0189] The battery needs to be charged or replaced

[0190] Optimal reflection and motion signal depends on frequency

[0191] The signal depends on the moving body

[0192] Choosing the optimal frequency is important

[0193] Movement of organs (breathing)

[0194] Movement of body and limbs

[0195] Using multiple channels also enables measurements of one or more of the following:

[0196] Electrical parameters (dielectric constant and load)

[0197] Coil loading conditions

[0198] Examples can provide distributed pilot / reference signals in the coil array. A complete digital pilot tone integration is obtained in the receiving array. This can, for example, provide an optimal pilot signal selected by the transmit matrix and the receive matrix. The individual pilot tones can be different in frequency-phase-complex modulation. By filtering and post-processing the measurement data, different types of motion can be detected and distinguished, even allowing the movement to be localized. By using a combination of N receive coil elements with M local transmitters, we obtain N×M signals simultaneously. This allows the derivation of motion vectors.

[0199] With a fully digital local transmitter, individual pilot tones can be separated by signal processing (e.g. via code division multiple access CDMA) Therefore, fully parallel pilot tones (multi-channel pilot tone signals) are feasible, including the reconstruction of low-resolution images and applications of multi-band MRI.

[0200] Fig. 9 An example of multi-channel pilot tone data 134 is illustrated. The plot shown at 134 shows multiple plots of measured individual pilot tone signals. The cardiac signal and respiratory motion are well detected, but they strongly depend on how strong the cardiac signal or respiratory signal respectively is in each individual coil channel.

[0201] The local coil is able to receive narrowband signals outside the image band (pilot tone). Here, the frequency is close to the MR frequency. By using additional RF channels, we integrate broadband receiving antennas (or different frequencies) in the MR coil. These additional RF channels receive motion modulated (amplitude and phase) signals at selected frequencies optimized for motion detection.

[0202] The data (multi-channel pilot tone data) can also feed a convolutional neural network or a recurrent neural network. A recurrent neural network (RNN) is a type of artificial neural network in which the connections between nodes form a directed graph along a sequence. This allows it to exhibit dynamic temporal behavior for time series. Unlike feedforward neural networks, RNNs can use their internal state (memory) to process sequences of inputs (here different frequencies). This makes them suitable for tasks such as unsegmented, connected motion recognition or pilot tone motion recognition.

[0203] Fig.10 The diagram shows Fig. 9 1000 and 1002. FIG. 1000 is an example of a motion state 136 determined from a multi-channel pilot tone signal 134 in FIG. Shown in the plot is a synthesized heart signal 1000 and a synthesized respiration signal 1002.

[0204] Fig.11 An example of a combined magnetic resonance and pilot tone coil system 1100 is illustrated. Antenna 1100 includes a plurality of coil elements 1102. The coil elements in this figure are used as receiving coils for a magnetic resonance imaging system and a plurality of receiving coils 116. The coils are connected to individual radio frequency systems 108'. In this example, there is one radio frequency system 108' for each channel. The coil elements 1102 are each connected to a digital receiving unit 1104. The digital receiving unit is connected to a controller 1110, which is able to communicate with the rest of the magnetic resonance imaging system via an optical communication system 1112. The controller 1110 is also connected to a pilot tone digital transmitter 1106. The pilot tone digital transmitter is connected to a plurality of individual transmit coils 114. A unique pilot tone signal is transmitted on the plurality of transmit coils 114. The pilot tone data is then received by the coil 1102. Each digital pilot transmitter may have a local antenna (strip line, dielectric).

[0205] Fig.11 A distributed digital pilot tone transceiver array is shown. Each pilot antenna is decoupled from the local MRI coil to obtain maximum value. Decoupling is performed to prevent saturation of the preamplifier. Alternatively, the pilot tone is injected into the MR preamplifier in reverse phase to prevent saturation. Operations to avoid preamplifier saturation are performed in the analog domain. For multi-band MRI, pilot tones and / or coded pilot tones can be transmitted at individual frequencies.

[0206] The individual transmitters can be at a higher frequency then the MRI frequency. The downsampled signal is folded back in the image domain and further processed.

[0207] Fig.12 The diagram shows the operation Figure 5 and Figure 7Flowchart of the method of the medical system 500 and 700 of the present invention. First, in step 1200, a patient magnetic resonance sequence is selected / received. Next, in step 1202, a magnetic resonance imaging coil is selected. In step 1204, a reference signal and a pilot signal are defined. Then, in step 1204, a pilot tone antenna is selected and there is a preparation phase. For example, if the pilot tone antenna is integrated into a magnetic resonance imaging antenna, the pilot tone antenna can be placed or positioned on the object.

[0208] Then, in step 1208, a pilot tone signal is transmitted and received. This is equivalent to steps 200 and 202. Then, in step 1210, there is signaling processing of the pilot tone data to determine the motion state. This can be performed, for example, using signal processing or using deep learning or other neural networks. This can be equivalent to step 204. After step 1210, two separate steps can be performed. In step 1212, the motion state is used to trigger a magnetic resonance imaging sequence. For example, magnetic resonance imaging can be triggered at a specific respiratory phase or cardiac phase. After step 1210, step 1214 can also be performed. In this step, the motion state is used to process the magnetic resonance imaging data or predict the motion of the object, and the motion state can be used thereafter to correct the image or correct the acquisition of predictors to improve quality.

[0209] For distributed pilot tones, the MRI system is able to define the optimal locations of transmitters and receivers to obtain the highest pilot signal sensitivity, such as Fig.12 As shown. A pilot tone is sent simultaneously. Decoding is performed by individual modulation of the individual transmitters.

[0210] Another application is the detection of peripheral nerve stimulation during magnetic resonance imaging. The pilot tone signal acquired by the receive coil array can be used and correlated with the gradient waveform signal to detect and trigger PNS detection. The complete matrix of receive coils is measured and correlated with the gradient waveform to detect PNS.

[0211] If certain thresholds are reached, the MR sequence is adjusted to reduce PNS. The sequence is automatically adjusted for patient comfort parameters. Measurements: change readout direction, change sequence, gradient strength, reposition patient. The data (multi-channel pilot tone data) can also feed a convolutional neural network or a recurrent neural network.

[0212] The strong gradients applied during an MRI examination can trigger peripheral nerve stimulation, causing movement of muscle fibers or entire muscles.

[0213] PNS……

[0214] Patient is uncomfortable

[0215] The level is the patient's individual

[0216] Set limits globally, ignoring individual sensitivity of PNS

[0217] Unable to communicate with mentally retarded or medically sedated patients. No quantitative feedback for operators

[0218] Not detectable by camera-based methods

[0219] Can cause artifacts due to motion

[0220] Can result in accidental scans when patient call operator is due

[0221] PNS detection may be performed by detecting the PNS using a pilot tone signal picked up by a receive coil array.

[0222] Generally, the effect of PNS on the pilot tone signal is expected to be lower than the effect of, for example, breathing. In view of this and in order to distinguish other movements, the pilot tone signal acquired by the receiving coil can be correlated with the gradient waveform.

[0223] If certain thresholds are reached, the MR sequence is adjusted to reduce PNS. The sequence is automatically adjusted to parameters that are comfortable for the patient. Possible measures are to change:

[0224] Change the read direction,

[0225] Change the sequence,

[0226] Gradient strength,

[0227] Patient position / posture

[0228] Other complementary data may also be used, such as optical, camera, radar, and ultrasonic acoustic detection.

[0229] Current MRI scanners employ a low power transmit path that is independent of the transmit chain of the body coil for calibration purposes. Here, a small off-resonance coil is attached to the RF screen and to the body coil. The transmit power of this coil is adjusted so that the RF signal is in the same order as that originating from the spin system. Reception is done using a standard MRI coil.

[0230] Pilot tone measurements can be interleaved or combined with the MR sequence. Tests have shown that this setup allows detection of motion caused by respiration. Further tests are being performed to increase the sensitivity of the setup.

[0231] Above Fig. 9An example of a pilot tone amplitude signal is shown. Additional information can be obtained while observing the phase of the acquired signal. The ideal position of the off-resonance coil was determined in testing to provide the most sensitive results to respiratory and cardiac motion. In the given experiment, the best setup was to place the coil on top of the patient's sternum. Using all available receive coils to acquire the pilot tone allows for (limited) spatial sensitivity.

[0232] This insight can be used to distinguish between different types of movement.

[0233] Another location may be more appropriate for PNS detection, for example, near the long muscles of the patient's back.

[0234] The data (multi-channel pilot tone data) can also feed a convolutional neural network or a recurrent neural network. A recurrent neural network (RNN) is a type of artificial neural network in which the connections between nodes form a directed graph along the sequence. This allows it to exhibit dynamic temporal behavior for time series. Unlike feedforward neural networks, RNNs are able to use their internal state (memory) to process sequences of inputs (here, different frequencies). This makes them suitable for tasks such as unsegmented, connected motion recognition or camera motion recognition (see below Fig.13 ).

[0235] Fig.13 The software algorithms and functional building blocks of the system are illustrated, which may be incorporated into, for example, Figure 7 13. In a magnetic resonance imaging system such as the medical system 700 shown in FIG. 13. Block 1300 represents a pilot tone system and a radio frequency reference coil array. Block 1302 represents a gradient waveform from a pulse sequence command. Block 1304 represents a software component that is a peripheral nerve stimulation detector and / or correlator 1304. The detector or correlator 1304 can obtain information about the gradient waveform 1302 from the pilot tone data 1300 to detect whether peripheral nerve stimulation is present. This information is then fed into a controller 1306.

[0236] For example, the controller 1306 may be equivalent to the processor 122. This information may then be forwarded or processed from the controller and fed to the neural network 1308, which may be, for example, equivalent to the neural network 138. The controller 1306 can use the detection of peripheral nerve stimulation to, for example, modify the behavior of the gradient amplifier 1310, and may even be able to modify the behavior or change the pulse sequence commands 530. This data may also be provided to the peripheral nerve stimulation monitor 1314. This data may be provided, for example, via the user interface 126.

[0237] Fig.13 The following scheme shown illustrates how the pilot tone data is processed and used.

[0238] In the first step, the pilot tone data is correlated with the gradient waveform. Depending on the level of signal correlation, the controller decides: Correlation below first threshold = No low PNS: Run sequence as planned

[0239] Correlation below the second threshold = considerable PNS: Adjusted series

[0240] Correlation above second threshold = PNS at pain limit or expected considerable image artifacts: terminate scan by gradient amplifier interlock

[0241] 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.

[0242] Those skilled in the art can understand and implement other variations of the disclosed embodiments when practicing the claimed invention by studying the drawings, the disclosure and the claims. In the claims, the word "comprising" does not exclude other components or steps, and the words "one" or "an" do not exclude multiple. A single processor or other unit can implement the functions of several items recorded in the claims. Although certain measures are recorded in mutually different dependent claims, this does not indicate that a combination of these measures cannot be used to advantage. The computer program may be stored / distributed on a suitable medium, for example, an optical storage medium or solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, for example, via the Internet or other wired or wireless telecommunications systems. Any reference numerals in the claims should not be interpreted as limiting the scope.

Claims

1. A medical system (100, 300, 500, 700), comprising: a memory (128) storing machine-executable instructions (130); a processor (122) configured to control the medical system; A magnetic resonance imaging system (502); as well as A pilot tone system (106); Wherein, the pilot tone system comprises: A radio frequency system (108) comprising a plurality of transmit channels (110) and a plurality of receive channels (112), wherein the plurality of transmit channels are configured to transmit a unique pilot tone signal (132) via a plurality of transmit coils (114), wherein the radio frequency system is configured to encode each of the unique pilot tone signals using any of the following: frequency encoding, phase encoding, complex modulation, CDMA encoding, and combinations thereof, wherein the plurality of receive channels are configured to receive multi-channel pilot tone data (134) via a plurality of receive coils (116), wherein each of the plurality of receive channels comprises: (i) one of the plurality of receive coils (116) configured as a magnetic resonance imaging coil (1102), and (ii) a radio frequency system (108) comprising one of the plurality of pilot tone transmit coils (114), wherein the magnetic resonance imaging coil (1102) is decoupled from the pilot tone transmit coil within each of the receive channels; wherein execution of the machine executable instructions causes the processor to: transmitting (200) a multi-channel pilot tone signal by controlling at least a portion of the plurality of transmit channels to transmit the unique pilot tone signal; Acquiring (202) the multi-channel pilot tone data by controlling at least a portion of the plurality of receiving channels to receive the multi-channel pilot tone data (134); and The motion state (136) of the object is determined (204) using the multi-channel pilot tone data.

2. The medical system according to claim 1, wherein: The motion state is any one of the following: Object motion position; Motion vectors; Object motion classification; Respiratory status; Cardiac motion status; a translation vector describing at least a portion of the object; describing a rotation of at least a portion of the object; and Its combination.

3. The medical system according to claim 1, wherein: Execution of the machine executable instructions causes the processor to determine the motion state using any of: using a recurrent neural network configured to receive the multi-channel pilot tone data and the unique pilot tone signal and configured to output the motion state; detecting a distance between the object and each of the plurality of receiving coils; Use digital filters; Use principal component analysis; and Its combination.

4. The medical system according to claim 1, wherein: The radio frequency system includes a digital receiver (1104) coupled to the magnetic resonance imaging coil (1102) and a pilot tone digital transmitter (1106) coupled to the pilot tone transmit coil (114).

5. The medical system according to claim 1, wherein: The magnetic resonance imaging system is configured to acquire magnetic resonance imaging data within an imaging frequency range, wherein the plurality of transmit channels are configured to transmit the unique pilot tone signal outside the imaging frequency range.

6. The medical system according to claim 5, wherein: The memory further comprises a pulse sequence command, wherein the pulse sequence command is configured to control the magnetic resonance imaging system to acquire magnetic resonance imaging data, wherein the execution of the machine executable instructions further causes the processor to control the magnetic resonance imaging system to acquire the magnetic resonance imaging data using the pulse sequence command, wherein the execution of the machine executable instructions causes the processor to perform the following operations during the control of the magnetic resonance imaging system using the pulse sequence command: transmitting the multi-channel pilot tone signal; collecting the multi-channel pilot tone data; and The motion state of the object is determined using the multi-channel pilot tone data.

7. The medical system according to claim 6, wherein: Execution of the machine executable instructions further causes the processor to: using the pulse sequence command to determine a current gradient pulse frequency; using the motion state to detect object motion having a periodicity within a predetermined range of the current gradient pulse frequency; A peripheral nerve stimulation warning signal is provided if motion of the subject is detected.

8. The medical system according to claim 7, wherein: Execution of the machine executable instructions further causes the processor to perform any of the following if the peripheral nerve stimulation warning signal is provided: Select the alternate pulse sequence command; modifying the pulse sequence command; and Cancels the execution of the pulse sequence command.

9. The medical system according to claim 1, wherein: The pilot tone system further comprises the plurality of transmitting coils and the plurality of receiving coils; wherein the medical system further comprises a tomographic imaging system (302) for acquiring tomographic imaging data from an object within an imaging region, wherein execution of the machine executable instructions further causes the processor to control the tomographic imaging system to acquire the tomographic imaging data; wherein execution of the machine executable instructions causes the processor to perform the following operations during control of the tomographic imaging system to acquire the tomographic imaging data: transmitting the multi-channel pilot tone signal; collecting the multi-channel pilot tone data; and The motion state of the object is determined using the multi-channel pilot tone data.

10. The medical system according to claim 9, wherein: Execution of the machine executable instructions further causes the processor to: reconstructing a medical image (314) using the tomographic imaging data (312); and The reconstruction of the medical image is corrected using the motion state of the object.

11. The medical system according to claim 9, wherein: The tomographic imaging system is any one of: a positron emission tomography system, a single photon emission tomography system, and an X-ray computed tomography system.

12. A computer program product comprising machine executable instructions (130) executed by a processor (122) controlling a medical system (100, 300, 500, 700), wherein: The medical system comprises a magnetic resonance imaging system (502), wherein the medical system comprises a pilot tone system (106), wherein the pilot tone system comprises a radio frequency system (108), wherein the radio frequency system comprises a plurality of transmit channels (110) and a plurality of receive channels (112), wherein the plurality of transmit channels are configured to transmit a unique pilot tone signal (132) via a plurality of transmit coils (114), respectively, wherein the radio frequency system is configured to encode each of the unique pilot tone signals using any of the following: frequency encoding, phase encoding, code, complex modulation, CDMA coding and combinations thereof, wherein the plurality of receiving channels are configured to receive multi-channel pilot tone data via a plurality of receiving coils (116), wherein each of the plurality of receiving channels comprises: (i) one receiving coil of the plurality of receiving coils (116) configured as a magnetic resonance imaging coil (1102), and (ii) a radio frequency system (108) comprising one pilot tone transmitting coil of a plurality of pilot tone transmitting coils (114), wherein the magnetic resonance imaging coil (1102) is decoupled from the pilot tone transmitting coil in each of the receiving channels; wherein execution of the machine executable instructions causes the processor to: transmitting (200) a multi-channel pilot tone signal by controlling at least a portion of the plurality of transmit channels to transmit the unique pilot tone signal; Acquiring (202) the multi-channel pilot tone data by controlling at least a portion of the plurality of receiving channels to receive the multi-channel pilot tone data (134); and The motion state (136) of the object is determined (204) using the multi-channel pilot tone data.

13. A method of operating a medical system (100, 300, 500, 700), wherein: The medical system comprises a pilot tone system (106), wherein the medical system comprises a magnetic resonance imaging system (502), wherein the pilot tone system comprises a radio frequency system (108), the radio frequency system comprising a plurality of transmit channels (110) and a plurality of receive channels (112), wherein the plurality of transmit channels are configured to transmit a unique pilot tone signal each via a plurality of transmit coils (114), wherein the radio frequency system is configured to encode each of the unique pilot tone signals using any of the following: frequency encoding, phase encoding, complex modulation, C DMA encoding and combinations thereof, wherein the plurality of receive channels are configured to receive multi-channel pilot tone data via a plurality of receive coils (116), wherein each of the plurality of receive channels comprises: (i) one of the plurality of receive coils (116) configured as a magnetic resonance imaging coil (1102), and (ii) a radio frequency system (108) comprising one of a plurality of pilot tone transmit coils (114), wherein the magnetic resonance imaging coil (1102) is decoupled from the pilot tone transmit coil within each of the receive channels, wherein the method comprises: transmitting (200) a multi-channel pilot tone signal by controlling at least a portion of the plurality of transmit channels to transmit the unique pilot tone signal; Acquiring (202) the multi-channel pilot tone data by controlling at least a portion of the plurality of receiving channels to receive the multi-channel pilot tone data (134); and The motion state (136) of the object is determined (204) using the multi-channel pilot tone data.

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