阅读说明：本技术 多通道导频音运动检测 (Multi-channel pilot tone motion detection ) 是由 C·G·洛斯勒 C·芬德科里 J·J·迈内克 P·韦尔尼科尔 P·柯肯 于 2020-05-18 设计创作，主要内容包括：公开了一种医学系统(100、300、500、700),包括：存储器(128),其存储机器可执行指令(130)；处理器(122),其被配置用于控制所述医学系统；以及导频音系统(106)。所述导频音系统包括射频系统(108),所述射频系统包括多条发射通道(110)和多条接收通道(112)。所述多条发射通道被配置用于各自经由多个发射线圈来发射独特的导频音信号(132)。所述多条接收通道被配置用于经由多个接收线圈来接收多通道导频音数据(134)。对所述机器可执行指令的执行使所述处理器：通过控制所述多条发射通道的至少部分发射所述独特的导频音信号来发射(200)多通道导频音信号；通过控制所述多条接收通道的至少部分接收多通道导频音数据(134)来采集(202)所述多通道导频音数据；并且使用所述多通道导频音数据来确定(204)对象的运动状态(136)。(A medical system (100, 300, 500, 700) is disclosed, comprising: a memory (128) storing machine executable instructions (130); a processor (122) configured for controlling the medical system; and a pilot tone system (106). The pilot tone system includes a radio frequency system (108) including a plurality of transmit channels (110) and a plurality of receive channels (112). The plurality of transmit channels are configured to each transmit a unique pilot tone signal (132) via a plurality of transmit coils. 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: transmitting (200) a multi-channel pilot tone signal by controlling at least part of the plurality of transmit channels to transmit the unique pilot tone signal; acquiring (202) multi-channel pilot tone data (134) by controlling at least part of the plurality of receive channels to receive the multi-channel pilot tone data; and determining (204) a motion state (136) of the object using the multi-channel pilot tone data.)

1. A medical system (100, 300, 500, 700) comprising:

a memory (128) storing machine executable instructions (130);

a processor (122) configured for controlling the medical system; and

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 each transmit a unique pilot tone signal (132) via a plurality of transmit coils (114), wherein the plurality of receive channels are configured to receive multi-channel pilot tone data (134) via a plurality of receive coils (116);

wherein execution of the machine-executable instructions causes the processor to:

transmitting (200) a multi-channel pilot tone signal by controlling at least part of the plurality of transmit channels to transmit the unique pilot tone signal;

acquiring (202) multi-channel pilot tone data (134) by controlling at least part of the plurality of receive channels to receive the multi-channel pilot tone data; and is

Determining (204) a motion state (136) of an object using the multi-channel pilot tone data.

2. The medical system of claim 1, wherein the radio frequency system is configured to encode each of the unique pilot tone signals using any one of: frequency coding, phase coding, complex modulation, CDMA coding, and combinations thereof.

3. The medical system of claim 1 or 2, wherein the motion state is any one of:

a subject motion position;

a motion vector;

classifying the motion of the object;

a respiratory state;

a cardiac motion state;

a translation vector describing at least a portion of the object;

describing a rotation of at least a portion of the object; and

combinations thereof.

4. The medical system of any one of claims 1 to 3, wherein execution of the machine executable instructions causes the processor to determine the motion state using any one of:

using a recurrent neural network configured to receive the multi-channel pilot tone data and the distinctive pilot tone signal and configured to output the motion state;

detecting a distance between the object and each of the plurality of receive coils;

using a digital filter;

using principal component analysis; and

combinations thereof.

5. The medical system of any one of the preceding claims, wherein the medical system further comprises a magnetic resonance imaging system (502), wherein an individual receiving channel 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) including one of a plurality of pilot tone transmit coils (114), the magnetic resonance imaging coil (1102) being decoupled from the pilot tone transmit coils within individual receiver channels.

6. The medical system of claim 5, 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).

7. The medical system of claim 5 or 6, wherein the magnetic resonance imaging system is configured for acquiring magnetic resonance imaging data within an imaging frequency range, wherein the plurality of transmit channels are configured for transmitting the unique pilot tone signals outside the imaging frequency range.

8. The medical system of claim 7, wherein the memory further contains pulse sequence commands configured to control the magnetic resonance imaging system to acquire magnetic resonance imaging data, wherein execution of the machine executable instructions further causes the processor to control the magnetic resonance imaging system to acquire the magnetic resonance imaging data with the pulse sequence commands, wherein execution of the machine executable instructions causes the processor to perform the following operations during control of the magnetic resonance imaging system with the pulse sequence commands:

transmitting the multi-channel pilot tone signal;

collecting the multi-channel pilot tone data; and is

Determining the motion state of the object using the multi-channel pilot tone data.

9. The medical system of claim 8, wherein execution of the machine executable instructions further causes the processor to:

determining a current gradient pulse frequency using the pulse sequence commands;

using the motion state to detect object motion having a periodicity within a predetermined range of the current gradient pulse frequency;

providing a peripheral nerve stimulation warning signal if motion of the subject is detected.

10. The medical system of claim 9, wherein execution of the machine executable instructions further causes the processor, if the peripheral nerve stimulation warning signal is provided, to perform any one of:

selecting a substitute pulse sequence command;

modifying the pulse sequence command; and

cancelling execution of the pulse sequence command.

11. The medical system of any one of claims 1 to 4, wherein the pilot tone system further comprises the plurality of transmit coils and the plurality of receive coils; wherein the medical system further comprises a tomographic imaging system (302) for acquiring (300) tomographic imaging data from an object within an imaging zone, 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 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 is

Determining the motion state of the object using the multi-channel pilot tone data.

12. The medical system of claim 11, wherein execution of the machine executable instructions further causes the processor to:

reconstructing a medical image (314) using the tomographic imaging data (312); and is

Correcting the reconstruction of the medical image using the motion state of the object.

13. The medical system of claim 11 or 12, wherein the tomographic imaging system is any one of: positron emission tomography systems, single photon emission tomography systems, and X-ray computed tomography systems.

14. A computer program product comprising machine executable instructions (130) for execution by a processor (122) controlling a medical system (100, 300, 500, 700), wherein the medical system comprises a pilot tone system (106), wherein the pilot tone system comprises a radio frequency system (108) comprising a plurality of transmit channels (114) and a plurality of receive channels (112), wherein the plurality of transmit channels are configured to each transmit a unique pilot tone signal (132) via a plurality of transmit coils (114), wherein the plurality of receive channels are configured to receive multi-channel pilot tone data via a plurality of receive coils (116);

wherein execution of the machine-executable instructions causes the processor to:

transmitting (200) a multi-channel pilot tone signal by controlling at least part of the plurality of transmit channels to transmit the unique pilot tone signal;

acquiring (202) multi-channel pilot tone data (134) by controlling at least part of the plurality of receive channels to receive the multi-channel pilot tone data; and is

Determining (204) a motion state (136) of an object using the multi-channel pilot tone data.

15. A method of operating a medical system (100, 300, 500, 700), wherein the medical system comprises a pilot tone system (106), wherein the pilot tone system comprises a radio frequency system (108) comprising a plurality of transmit channels (114) and a plurality of receive channels (112), wherein the plurality of transmit channels are configured to each transmit a unique pilot tone signal via a plurality of transmit coils (114), wherein the plurality of receive channels are configured to receive multi-channel pilot tone data via a plurality of receive coils (116), wherein the method comprises:

transmitting (200) a multi-channel pilot tone signal by controlling at least part of the plurality of transmit channels to transmit the unique pilot tone signal;

acquiring (202) multi-channel pilot tone data (134) by controlling at least part of the plurality of receive channels to receive the multi-channel pilot tone data; and is

Determining (204) a motion state (136) of an object using the multi-channel pilot tone data.

Technical Field

The present invention relates to tomographic medical imaging, and in particular to the detection of object motion using pilot tones.

Background

In tomographic medical imaging techniques, such as magnetic resonance imaging, X-ray computed tomography, positron emission tomography, etc., data is acquired from an object over a period of time and used to reconstruct a medical image. This enables a physician or other healthcare professional to accurately image the internal anatomy of the subject. A drawback of these techniques is that the object can move during the acquisition of medical imaging data, which can lead to artifacts in the medical images.

Various techniques exist for correcting or compensating for object motion. One technique is pilot tone technology. 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. Motion such as cardiac motion, respiratory motion, and whole body motion can be detected in changes in signal strength.

US patent application publication US 20150320342 a1 discloses a magnetic resonance apparatus comprising a radio frequency unit comprising 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 coupled into the radio frequency antenna at least one radio frequency injection point. The magnetic resonance apparatus further comprises a patient receiving zone at least partially surrounded by the radio frequency antenna and a motion detection unit for detecting movements of a patient that may be positioned within the patient receiving zone. At least one radio frequency line comprises at least one injection element by means of which at least one motion detection signal of the motion detection unit is coupled into the radio frequency line.

Disclosure of Invention

The invention provides a medical system, a computer program product and a method in the independent claims. Embodiments are given in the dependent claims.

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 comprised of a unique pilot tone signal. Multiple receive channels receive these signals as multi-channel pilot tone data. This provides much more information than conventional pilot tone systems. Within the framework of the invention, the pilot tone system is based on the transmission of a pilot tone signal as an electromagnetic signal in the 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 the change in 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 spectral analysis information is carried by the pilot tone data.

In one aspect, the invention provides a medical system. The medical system includes a memory storing machine executable instructions. The medical system further comprises a processor configured for controlling the medical system. The medical system further comprises a pilot tone system. The pilot tone system includes a radio frequency system. The radio frequency system includes a plurality of transmit channels and a plurality of receive channels. The plurality of transmit channels are configured to each transmit a unique pilot tone signal via a plurality of transmit coils. The plurality of receive channels are configured to receive pilot tone data via a plurality of receive coils. The plurality of receive coils may be configured to receive the unique pilot tone signal.

The pilot tone data is an electrical signal generated in a plurality of reception channels by a unique pilot tone signal. 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 transmit channels to transmit the unique pilot tone signals. Execution of the machine-executable instructions further cause the processor to acquire 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. Execution of the machine-executable instructions further causes the processor to determine a motion state of an object using the multi-channel pilot tone data.

The motion state may describe periodic motion of the subject (e.g., breathing or heartbeat), and in other examples, the motion state may describe overall motion or whole body motion of the subject. 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.

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

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

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

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

In another embodiment, the motion state of the object is any one of: a subject motion position; a motion vector; classifying the motion of the object; a respiratory state; a cardiac motion state; a translation vector describing at least a portion of the object; describing a rotation of at least a portion of the object; and combinations thereof. This embodiment may be beneficial because these are all the various steps and motions that may be tracked using the multi-channel pilot tone system.

In another embodiment, execution of the machine-executable instructions further causes the processor to determine the motion state by 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 the signal transmitted by the plurality of transmit channels and the multi-channel pilot tone data is the data received by the plurality of receive channels. These can be input into a trained recurrent neural network to analyze the time-dependent signals from both. This may be useful in outputting the motion state.

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

In another embodiment, execution of the machine-executable instructions causes the processor to determine the motion state using a digital filter. In pilot tone systems, the digital filter is relatively intuitive to detect periodic motion. For example, motion due to the heart has frequency components similar to the frequency of a beating heart. The signal can then be isolated from the heartbeat using a digital filter. Likewise, motion of the subject due to breathing will also cause a frequency component similar to the breathing rate of the subject. Thus, the digital filter simply enables certain types of periodic motion to be determined.

In another embodiment, execution of the machine-executable instructions causes the processor to determine the motion state using principal component analysis. The machine learning techniques are effective in detecting various types of signals that may indicate motion.

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

In another embodiment, the magnetic resonance imaging system further comprises a magnetic resonance imaging coil. The magnetic resonance imaging coil includes a plurality of pilot tone transmit coils and a plurality of receive coils. This embodiment may be beneficial because the pilot tone transmit coil and the plurality of receive coils may be easily integrated into the magnetic resonance imaging coil.

In another embodiment, the magnetic resonance imaging system is further configured for acquiring magnetic resonance imaging data in an imaging frequency range. The plurality of transmit channels are configured to transmit the unique pilot tone signals outside the imaging frequency range. This may be beneficial because the electromagnetic signal used for the pilot tone signal does not interfere with the acquisition of the magnetic resonance imaging data. This may for example enable the acquisition of magnetic resonance imaging data and the manipulation of the pilot tone signal to be performed simultaneously.

In another embodiment, the memory further contains pulse sequence commands 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 with 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 with the pulse sequence commands: transmitting the multi-channel pilot tone signal; collecting 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 advantageous in that 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 the later motion correction of the magnetic resonance imaging data.

In another embodiment, execution of the machine-executable instructions further causes the processor to determine a current gradient pulse frequency using the pulse sequence commands. The current gradient pulse frequency is the frequency at which the gradient coil is currently oscillating. Execution of the machine-executable instructions further cause the processor to detect object motion having a periodicity within a predetermined range of the current gradient pulse frequency using motion states 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 motion of the subject is detected.

Gradient coils in a magnetic resonance imaging system may generate electrical currents or fields in a subject. This can cause so-called peripheral nerve stimulation and cause movement of the subject's muscle tissue. In this embodiment, the frequencies at which the gradient pulses are generated are compared to the multi-channel pilot tone data. If the frequency component is determined to be above a predetermined threshold, this may indicate that peripheral nerve stimulation of the subject is being examined. The frequency may also be compared or correlated with the actual gradient signal. This can be used to further increase the confidence that peripheral nerve stimulation is occurring.

In another embodiment, execution of the machine-executable instructions further causes the processor to select an alternate pulse sequence command if 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 alternate pulse sequence command.

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

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

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

In another embodiment, the medical system further comprises a tomographic imaging system configured for acquiring tomographic imaging data from an object within the 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, 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 using the multi-channel pilot tone data to determine the motion state of the object. This embodiment may be beneficial because the pilot tone may be applied to other imaging modalities than just magnetic resonance imaging.

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 correct the reconstruction of the medical image using the motion state of the object. For example, if the motion state or position of the object is known, this may assist in reconstructing the medical image to compensate for the motion of the object.

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

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

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

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 a portion of the plurality of transmit coils and at least a portion of the plurality of receive coils are integrated into the subject support. This may be beneficial as it may provide an efficient means of integrating the pilot tone signal into a tomography imaging system different from the magnetic resonance imaging system.

In one aspect, the invention provides a computer program product comprising machine executable instructions for execution by a processor controlling a medical system. The medical system includes a pilot tone system. The pilot tone system includes a radio frequency system including a plurality of transmit channels and a plurality of receive channels. The plurality of transmit channels are configured to each transmit a unique pilot tone signal 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 signals.

Execution of the machine-executable instructions causes the processor to acquire 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. Execution of the machine-executable instructions causes the processor to determine a motion state of an object using the multi-channel pilot tone data.

In another aspect, the 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 including a plurality of transmit channels and a plurality of receive channels. The plurality of transmit channels are configured to each transmit a unique pilot tone signal 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. The method includes transmitting 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. The method also includes acquiring 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. The method also includes determining a motion state of the object using the multi-channel pilot tone data.

In an example, a magnetic resonance imaging system includes: a memory storing machine executable instructions; and pulse sequence commands configured for controlling the magnetic resonance imaging system to acquire magnetic resonance imaging data. The magnetic resonance imaging system further comprises a processor configured for controlling the magnetic resonance imaging system to acquire magnetic resonance imaging data. The magnetic resonance imaging system further comprises 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 pilot tone data via at least one transmit channel.

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 acquire 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 determine a motion state of the object using the pilot tone data. Execution of the machine-executable instructions further causes the processor to determine a current gradient pulse frequency using the pulse sequence commands. Execution of the machine-executable instructions further causes the processor to detect object motion having a periodicity within a predetermined range of the current gradient pulse frequency using the pilot tone data.

Execution of the machine-executable instructions further causes the processor to provide a peripheral nerve stimulation warning signal if motion of the subject is detected. There may also be a threshold for determining whether the subject motion is above a certain critical or predetermined motion level that would require intervention from an operator or physician. Object motion can also be detected by determining a correlation between the motion state of the object and the 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 to automatically detect whether a 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 the image quality, as the motion of the object is reduced.

In another embodiment, execution of the machine-executable instructions further causes the processor, if a peripheral nerve stimulation alert is provided, to provide any one of: selecting a substitute pulse sequence command; modifying the pulse sequence command; canceling execution of the pulse sequence command; and displaying a visible signal or an audible signal.

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

In another embodiment, the magnetic resonance imaging system is configured for acquiring magnetic resonance imaging data in an imaging frequency range. The plurality of transmit channels are configured to transmit unique pilot tone signals outside of the image frequency range. This may be beneficial because operation of the pilot tone system does not interfere with the acquisition of magnetic resonance imaging data.

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

In another embodiment, the at least one receive channel is a plurality of receive channels.

In another embodiment, the at least one transmit lane is a single transmit lane.

In another embodiment, the at least one receive lane is a single receive lane.

It should be appreciated that one or more of the foregoing embodiments of the invention may be combined, as long as the combined embodiments are not mutually exclusive.

As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as an apparatus, method or computer program product. Accordingly, aspects of the present invention may take the form of: an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a "circuit," module "or" system. Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer-readable media having computer-executable code embodied thereon.

Any combination of one or more computer-readable media may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. "computer-readable storage medium" as used herein encompasses any tangible storage medium that can store instructions that are executable by a processor of a computing device. The computer-readable storage medium may be referred to as a computer-readable non-transitory storage medium. The computer readable storage medium may also be referred to as a tangible computer readable medium. In some embodiments, the computer-readable storage medium is also capable of storing data that is accessible by a processor of the computing device. Examples of computer-readable storage media include, but are not limited to: a floppy disk, a magnetic hard drive, a solid state disk, flash memory, a USB thumb drive, Random Access Memory (RAM), Read Only Memory (ROM), an optical disk, a magneto-optical disk, and a register file for a processor. Examples of optical disks include Compact Disks (CDs) and Digital Versatile Disks (DVDs), e.g., CD-ROMs, CD-RWs, CD-R, 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 a communication link. For example, data may be retrieved over a modem, over the internet, or over 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, wired, fiber optic cable, RF, etc., or any suitable combination of the foregoing.

A computer readable signal medium may include a propagated data signal with computer executable code embodied therein, for example, 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. The computer readable signal medium may be any computer readable medium that: the computer readable medium is not a computer readable storage medium and can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.

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

"processor" as used herein encompasses an electronic component capable of executing a program or machine-executable instructions or computer-executable code. References to a computing device that includes a "processor" should be interpreted as potentially containing 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 among multiple computer systems. The term "computing device" should also be read to possibly refer to a collection or network of multiple computing devices, each of which includes one or more processors. The computer executable code may be executed by multiple processors, which may be within the same computing device or even distributed across multiple computing devices.

The 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 aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language (e.g., Java, Smalltalk, C + +, etc.) and a conventional procedural programming language (e.g., the "C" programming language or similar programming languages), and compiled as machine executable instructions. In some instances, the computer executable code may be in a high level language form or in a pre-compiled form, and may be used in conjunction with an interpreter that generates the machine executable instructions on the fly.

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 the 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 the connection may be made to an external computer (for example, through the Internet using an Internet service provider).

Aspects of the present invention are described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block or portion of the blocks of the flowchart, illustrations and/or block diagrams can be implemented by computer program instructions in computer-executable code where appropriate. It will also be understood that blocks of the various flow diagrams, illustrations, and/or block diagrams, when not mutually exclusive, may be combined. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

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 devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks.

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 to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

As used herein, a "user interface" is an interface that allows a user or operator to interact with a computer or computer system. The "user interface" may also be referred to as a "human interface device". The user interface may provide information or data to and/or receive information or data from an operator. The user interface may enable input from an operator to be received by the computer and may provide output from the computer to a user. In other words, the user interface may allow an operator to control or manipulate the computer, and the interface may allow the computer to indicate the effect of the operator's control or manipulation. Displaying data or information on a display or graphical user interface is an example of providing information to an operator. Receiving data through a keyboard, mouse, trackball, trackpad, pointing stick, tablet, joystick, gamepad, webcam, head-mounted device, foot pedal, wired glove, remote control, and accelerometer are all examples of user interface components that enable receiving information or data from an operator.

As used herein, "hardware interface" encompasses an interface that enables a processor of a computer system to interact with and/or control an external computing device and/or apparatus. The hardware interface may allow the processor to send control signals or instructions to an external computing device and/or apparatus. The hardware interface may also enable the processor to exchange data with external computing devices 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 local area network connection, a TCP/IP connection, an Ethernet connection, a control voltage interface, a MIDI interface, an analog input interface, and a digital input interface.

"display" or "display device" as used herein encompasses an output device or user interface suitable for displaying images or data. The display may output visual, auditory, and/or tactile data. Examples of displays include, but are not limited to: computer monitors, television screens, touch screens, tactile electronic displays, braille screens, Cathode Ray Tubes (CRTs), memory tubes, bi-stable displays, electronic paper, vector displays, flat panel displays, vacuum fluorescent displays (VFs), Light Emitting Diode (LED) displays, electroluminescent displays (ELDs), Plasma Display Panels (PDPs), Liquid Crystal Displays (LCDs), organic light emitting diode displays (OLEDs), projectors, and head mounted displays.

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 a set adapted to acquire information about the body structure of a patient and to construct two-dimensional or three-dimensional medical image data. Medical image data can be used to construct visualizations that are useful for physician diagnosis. Such visualization can be performed using a computer.

Magnetic Resonance (MR) data is defined herein as being the recorded measurements of radio frequency signals emitted by atomic spins using an antenna of a magnetic resonance apparatus 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 being a two-dimensional visualization or a three-dimensional visualization of the reconstruction of anatomical data contained within the magnetic resonance imaging data. Such visualization can be performed using a computer.

Drawings

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

FIG. 1 illustrates an example of a medical system;

FIG. 2 shows a flow chart illustrating a method of operating the medical system of FIG. 1;

fig. 3 illustrates a further example of a medical system;

FIG. 4 shows a flow chart illustrating a method of operating the medical system of FIG. 3;

fig. 5 illustrates a further example of a medical system;

FIG. 6 shows a flow chart illustrating a method of operating the medical system of FIG. 5;

fig. 7 illustrates a further example of a medical system;

FIG. 8 shows a flow chart illustrating a method of operating the medical system of FIG. 5;

FIG. 9 illustrates an example of multi-channel pilot tone data;

FIG. 10 illustrates an example of a motion state derived from the multi-channel pilot tone data of FIG. 9;

FIG. 11 illustrates an example of a combined MRI and pilot tone coil;

FIG. 12 illustrates an example of a software system for a medical system; and is

Fig. 13 illustrates a further example of a software system for a medical system.

List of reference numerals

100 medical system

102 object

104 object support

106 pilot tone system

108 radio frequency system

108' individual radio frequency system

110 multiple transmit channels

110' at least one emission channel

112 multiple receiving channels

112' at least one receiving channel

114 multiple transmitting coils

114' at least one transmitting coil

116 multiple receiving coils

116' at least one receiving coil

120 computer

122 processor

124 hardware interface

126 user interface

128 memory

130 machine-executable instructions

132 unique pilot tone signal

132' one or more pilot tone signals

134 multichannel pilot tone data

134' pilot tone data

136 state of motion

138 recurrent neural network

200 transmit multi-channel pilot tone signals by controlling at least portions of a plurality of transmit channels to transmit unique pilot tone signals

202 acquire multi-channel pilot tone data by controlling at least a portion of a plurality of receive channels to receive multi-channel pilot tone data

204 use of multi-channel pilot tone data to determine a motion state of an object

300 medical system

302 tomographic imaging system

304 imaging area

310 control command

312 tomographic imaging data

314 tomographic medical image

Acquiring tomographic imaging data from an object within an imaging zone 400

500 medical imaging system

502 magnetic resonance imaging system

504 magnet

506 bore of magnet

508 imaging zone

509 region of interest

510 magnetic field gradient coil

512 magnetic field gradient coil power supply

514 magnetic resonance antenna

516 radio frequency coil

530 pulse sequence commands

532 magnetic resonance imaging data

534 magnetic resonance image

600 acquiring magnetic resonance imaging data

700 medical system

710 time dependent gradient pulse frequency

712 peripheral nerve stimulation warning signal

800 determining a current gradient pulse frequency using pulse sequence commands

802 use pilot tone data to detect object motion having a periodicity within a predetermined range of a current gradient pulse frequency

804 provides a peripheral nerve stimulation warning signal in the event that subject motion is detected

1000 synthetic cardiac signal

1002 synthesized respiratory signal

1100 Combined MR and Pilot tone coil

1102 coil

1104 digital transmitter

1106 Pilot tone digital receiver

1108 antenna pilot tone

1110 controller

1112 optical communication

Detailed Description

In the drawings, like numbered elements are either equivalent elements or perform the same function. Elements that have been previously discussed will not necessarily be discussed in subsequent figures if their functions are equivalent.

Fig. 1 illustrates an example of a medical system 100. 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, the 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, the computer 120 containing a processor 122. Processor 122 is intended to represent one or more processors.

Processor 122 may, for example, represent multiple processing cores and processor 122 distributed across multiple computer systems. The processor 122 is connected to a hardware interface 124, the hardware interface 124 enabling the processor 122 to control other components of the medical system 100. The hardware interface 124 may also, for example, serve as a network interface and enable the processor 122 to communicate with other processors and/or computer systems. The computer 120 is also shown as containing an optional user interface 126, the optional user interface 126 may be used, for example, by an operator to control the medical system 100. The computer 120 is also shown as including a memory 128.

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

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 functions 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 to contain a unique pilot tone signal 132 that has been constructed for each of the plurality of transmit channels 110. For example, the unique pilot tone signal 132 may be transmitted to the radio frequency system 108 for transmission via the processor 122. 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 plurality of receive channels 112. The transmit channel transmits a unique pilot tone signal 132 and this causes some portion of these signals to be received in the receive channel. This is the multi-channel pilot tone data 134.

The combination of the unique pilot tone signals 132 results in a co-transmitted multi-channel pilot tone signal. The memory 128 is also shown to contain motion states 136 that have been calculated using multi-channel pilot tone data 134 and unique pilot tone signals 132 or multi-channel pilot signals. The motion state 136 may be calculated using a variety of different models for signal processing techniques. As one example, the memory 128 is shown as containing a recurrent neural network 138. The recurrent neural network 138 receives the distinctive 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.

In one example of fig. 1, the components of the pilot tone system are also integrated into the subject support. For example, the pilot tone system may be fully contained within the subject support. This may for example be achieved by using an object support to add a pilot tone system to a medical imaging system such as an MRI system or an X-ray system. The subject support may also be used for different imaging techniques, e.g. magnetic resonance imaging. A single subject support may be moved to different imaging systems as well as different types of imaging systems.

Fig. 2 shows a flow chart illustrating a method of operating the medical system 100 of fig. 1. First, in step 200, a multi-channel pilot tone signal 132 is transmitted by controlling at least a portion of the plurality of transmit channels 110. The multi-channel pilot tone signal is collectively formed from individually unique pilot tone signals 132. Next, in step 202, multi-channel pilot tone data 134 is acquired by controlling at least a portion of the plurality of receive channels 112.

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, it is likely that both the multi-channel pilot tone data 134 and the individual unique pilot tone signals 132 will be input. In other cases, the motion state 136 can be determined from the multi-channel pilot tone data 134 alone. For example, periodic respiratory motion or cardiac motion of the subject 102 may cause the multi-channel pilot tone data 134 to have a frequency component equal to or approximately equal to the heart rate and/or respiratory rate. Thus, cardiac motion and/or respiratory motion may be determined solely by the multi-channel pilot tone data 134.

Fig. 3 illustrates a further example of a medical system 300. Medical system 300 in fig. 3 is similar to medical system 100 in fig. 1, except that medical system 300 additionally includes a tomographic imaging system 302. The tomographic imaging system may 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 subject support 104 is shown supporting a portion of the subject 102 within an imaging zone 304. The imaging zone 304 is a location in space where the tomographic imaging system 302 is capable of acquiring tomographic imaging data 312.

The memory 128 is also shown as containing control commands 310, the control commands 310 enabling the processor 122 to control the tomographic imaging system 302 to acquire tomographic imaging data 312. The memory 128 is also shown as containing tomographic imaging data 312 acquired by controlling the tomographic imaging system 302 with 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 may be acquired at the same time the tomographic imaging data 312 is 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 states 136 can be used to gate acquisition of 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 reconstruction of the tomographic medical image 314.

Fig. 4 shows a flow chart illustrating a method of operating the medical system 300 of fig. 3. First, in step 400, the processor 122 controls the tomographic imaging system 302 using the control commands 310. At the same time, steps 200, 202 and 204 as shown in fig. 2 are performed.

Fig. 5 illustrates a further example of a medical system 500. The medical system in fig. 5 is similar to the medical system 300 in fig. 3, with the difference that the tomographic imaging system is in particular a magnetic resonance imaging system 502.

The magnetic resonance imaging system 502 comprises a magnet 504. The magnet 504 is a superconducting cylindrical type magnet having a bore 506 therethrough. Different types of magnets may also be used; for example, a split cylindrical magnet and a so-called open magnet may also be used. The split cylindrical magnet is similar to a standard cylindrical magnet, except that the cryostat has been split into two parts to allow access to the iso-plane of the magnet, such a magnet may be used, for example, in conjunction with charged particle beam therapy. An open magnet has two magnet portions, one above the other, with a space between them sufficient to receive an object: the regional arrangement of these 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.

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

Also within the bore 506 of the magnet is a set of magnetic field gradient coils 510, the magnetic field gradient coils 510 being used to acquire 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 contain three independent sets of coils that are used for spatial encoding in three orthogonal spatial directions. A 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 as a function of time and may be ramped or pulsed.

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 further comprises a plurality of radio frequency coils 516, the plurality of radio frequency coils 516 being used to perform magnetic resonance imaging. The radio frequency system 108 is also connected to a radio frequency coil 516. The arrangement shown in figure 5 enables the acquisition of magnetic resonance imaging data while using a pilot tone system. In other examples, the radio frequency coil 516 may also function as multiple transceiver coils 114 and/or multiple receive coils 116.

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 appreciated 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, system 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.

The radio frequency system 516 and the gradient controller 512 are shown connected to the hardware interface 124 of the computer system 128. Memory 128 is shown as containing pulse sequence commands 530 rather than control commands. The pulse sequence commands 530 are commands for controlling the operation of the magnetic resonance imaging system 502 or data that may 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 with pulse sequence commands 530.

The memory 128 is also shown as containing a magnetic resonance image 534 reconstructed from the magnetic resonance imaging data 532. As with medical system 300 in FIG. 3, 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 for reconstruction of a magnetic resonance image 534.

Fig. 6 illustrates a method of controlling the medical system 500 of fig. 5. First, in step 600, the magnetic resonance imaging system 502 is controlled to acquire magnetic resonance imaging data 534 with pulse sequence commands 530. When step 600 is performed, steps 200, 202 and 204 from fig. 2 are performed simultaneously.

Fig. 7 illustrates a further example of a medical system 700. The medical system in fig. 7 is similar to the medical system of fig. 5. 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'.

The memory 128 may also include a time dependent gradient pulse frequency 710 determined from the pulse sequence commands 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 correlation of the motion state to the detected motion is above a certain degree or above a certain amplitude within the same frequency range, there may be a generated peripheral nerve stimulation warning signal 712.

Fig. 8 shows a flow chart illustrating a method of operating the medical system 700 of fig. 7. This method is similar to the method shown in fig. 6. To start, steps 600, 200, 202, 204 are performed as in fig. 6. After step 204 is performed or before step 800 is performed, the time dependent gradient pulse frequency 710 is determined using the pulse sequence command 530. Next, in step 802, the motion state 136 is used to detect object motion having a periodicity within a predetermined range or a correlation with a 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 case a subject motion is detected.

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

For autonomous imaging, this may enable ECG-free heartbeat detection and separation and quantification of head-body motion in conjunction with camera-based methods.

Both MRI and CT scans may require many input parameters and proper scan preparation. Depending on the body shape, weight, patient position to be scanned and anatomy, the protocol is selected and modified to fit the patient. Typically, this data is entered manually. A dedicated sensor may be used to measure a physiological parameter (e.g., necessary for triggering a scan). It has recently been demonstrated that: the relevant parameters can be derived from a live video stream from a camera observing the patient during the scan.

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

Examples may have one or more of the following benefits:

ECG-less heartbeat detection

Separation and quantification of head-body motion

Deriving triggers for cardiac and respiratory motion

Application to MR LINAC-radiation therapy

Given the number of pure parameters and the interdependence of parameter non-linearities (amplifier gain, fixed parameter limits), it may be difficult to analytically optimize tens of input and output parameters from an RF sensor over a given time frame.

Camera-based motion detection systems suffer from allocation problems in the compact bore 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.

The signal-to-noise ratio depends on the position of the pilot tone antenna/coil. In experiments, determining multiple channels may be beneficial for extracting different types and different directions of head motion, requiring multiple pilot sources distributed around the head/object. The use of multiple channels may provide one or more of the following features or benefits:

fixed frequency crystal oscillator

Additional components

Localization of pilot transmitters

For applications where cardiac sensing/respiration is limited

The working process is as follows: additional steps for workflow

The battery needs to be charged and replaced

Optimal reflection and motion signal depends on frequency

The signals being dependent on the body in motion

It is important to select the optimum frequency

Movement of organs (respiration)

Movement of the body and limbs

Using multiple channels may also enable measurements of one or more of the following:

electrical parameters (dielectric constant and load)

Coil load condition

Examples may provide distributed pilot/reference signals in a coil array. A complete digital pilot tone integral is obtained in the receive array. This may provide, for example, the optimal pilot signal selected by the transmit matrix and the receive matrix. 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 if the movement is allowed to be localized. By using a combination of N receive coil elements and M local transmitters, we obtain N × M signals simultaneously. This allows motion vectors to be derived.

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

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

The local coils are capable of receiving narrowband signals that lie outside of the image bands (pilot tones). Here, the frequency is close to the MR frequency. By using an additional RF channel we integrate a broadband receiving antenna (or different frequency) in the MR coil. These additional RF channels receive motion modulated (amplitude and phase) signals at selected frequencies optimized for motion detection.

The data (multi-channel pilot tone data) can also feed a convolutional neural network or a cyclic neural network. A Recurrent Neural Network (RNN) is a type of artificial neural network in which connections between nodes form a directed graph along a sequence. This allows it to exhibit dynamic temporal behavior with respect to a temporal sequence. Unlike feed-forward neural networks, RNNs are able to process input sequences (here different frequencies) using their internal state (memory). This makes them suitable for tasks such as undivided, concatenated motion identification or pilot tone motion identification.

FIG. 10 illustrates an example of a motion state 136 determined from the multi-channel pilot tone signal 134 of FIG. 9. Shown in the plot is a synthesized cardiac signal 1000 and a synthesized respiratory signal 1002.

Figure 11 illustrates an example of a combined magnetic resonance and pilot tone coil system 1100. The antenna 1100 includes a plurality of coil elements 1102. The coil elements in this figure serve as receive coils for the magnetic resonance imaging system and a plurality of receive coils 116. The coils are connected to an individual radio frequency system 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, the controller 1110 being capable of communicating 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 transmitters are connected to a plurality of individual transmit coils 114. A unique pilot tone signal is transmitted on the plurality of transmit coils 114. Pilot tone data is then received by coil 1102. Each digital pilot transmitter may have a local antenna (stripline, dielectric).

Fig. 11 shows a distributed digital pilot tone transceiver array. Each pilot antenna is decoupled from the local MRI coil to obtain a maximum. Decoupling to prevent saturation of the preamplifier. Alternatively, the pilot tone is injected into the MR preamplifier in anti-phase to prevent saturation. The operation of avoiding saturation of the preamplifier is performed in the analog domain. For multi-band MRI, pilot tones may be transmitted and/or encoded at individual frequencies.

The individual transmitters can be at a higher frequency, followed by an MRI frequency. The down-sampled signal is folded back in the image domain and further processed.

Fig. 12 shows a flow chart illustrating a method of operating the medical systems 500 and 700 of fig. 5 and 7. 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, reference signals and pilot signals 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 may be placed or positioned on the subject.

Then, in step 1208, pilot tone signals are 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 may 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 may be triggered at a particular respiratory phase or cardiac phase. After step 1210, step 1214 may also be performed. In this step the motion state is used to process the magnetic resonance imaging data or to predict the motion of the object, and thereafter the motion state may be used to correct the image or to correct the acquisition of the predictor to improve quality.

For distributed pilot tones, the MRI system can define the optimal locations of the transmitter and receiver to obtain the highest pilot signal sensitivity, as shown in fig. 12. Pilot tones are transmitted simultaneously. The decoding is performed by individual modulation of individual transmitters.

Another application is the detection of peripheral nerve stimulation during magnetic resonance imaging. Pilot tone signals acquired by the receive coil array may be used and correlated with the gradient waveform signals to detect and trigger PNS detection. The complete matrix of receive coils is measured and correlated with the gradient waveforms to detect PNS.

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

A strong gradient applied during an MRI examination can trigger peripheral nerve stimulation, causing movement of muscle fibers or the entire muscle.

PNS……

Patient discomfort

The rank is individual to the patient

Setting limits on a global scale, ignoring individual sensitivities of PNS

There is no communication with patients suffering from either mental retardation or drug sedation. Operator no quantitative feedback

Inability to detect by camera-based methods

Can cause artifacts due to motion

When a patient call operator expires, an accidental scan can result

PNS detection may be performed by detecting PNS using pilot tone signals acquired by a receive coil array.

Typically, the PNS is expected to have a lower effect on the pilot tone signal than, for example, respiration. In view of this and in order to distinguish between other movements, the pilot tone signal acquired by the receive coil may be correlated with the gradient waveforms.

If certain thresholds are reached, the MR sequence is adjusted to reduce PNS. The sequence is automatically adjusted for the parameters of patient comfort. Possible measures are changes:

the direction of the readout is changed,

the sequence is changed in such a way that,

the strength of the gradient is set to be,

position/posture of patient

Other supplemental data may also be used, such as optical, camera, radar, and ultrasonic acoustic detection.

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 offset resonance coil is attached to the RF screen and to the body coil. The transmit power of the coil is adjusted so that the RF signals are in the same order from the spin system. The reception is performed using standard MRI coils.

Pilot tone measurements can be interleaved with the MR sequence or combined. The test shows that: this arrangement allows detection of movement caused by breathing. Further tests are performed to increase the sensitivity of the setup.

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

This insight can be used to distinguish between different types of movements.

For PNS detection, another location may be more appropriate, for example, a location of the long muscle near the back of the patient.

The data (multi-channel pilot tone data) can also feed a convolutional neural network or a cyclic neural network. A Recurrent Neural Network (RNN) is a type of artificial neural network in which connections between nodes form a directed graph along a sequence. This allows it to exhibit dynamic temporal behavior with respect to a temporal sequence. Unlike feed-forward neural networks, RNNs are able to process input sequences (here different frequencies) using their internal state (memory). This makes them suitable for tasks such as undivided, connected motion recognition or camera motion recognition (see fig. 13 below).

Fig. 13 illustrates software algorithms and functional building blocks of a system that may be incorporated, for example, in a magnetic resonance imaging system such as the medical system 700 shown in fig. 7. Block 1300 represents the pilot tone system and the radio frequency reference coil array. Block 1302 represents gradient waveforms from the pulse sequence commands. Block 1304 represents software components that are peripheral nerve stimulation detectors and/or correlators 1304. A detector or correlator 1304 can obtain information about the gradient waveform 1302 from the pilot tone data 1300 to detect the presence or absence of peripheral nerve stimulation. This information is then fed into the controller 1306.

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 that behavior or change the pulse sequence commands 530. This data may also be provided to peripheral nerve stimulation monitor 1314. The data may be provided, for example, via the user interface 126.

The following scheme, shown in fig. 13, illustrates how pilot tone data is processed and used.

In a first step, pilot tone data is correlated with the gradient waveforms. Depending on the level of signal correlation, the controller decides: correlation below the first threshold-no low PNS: run sequence as planned

The correlation below the second threshold is a significant PNS: adjustment sequence

Correlation above the second threshold — PNS at the pain limit or considerable image artifact expected: terminating scanning by gradient amplifier interlock

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.

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 words "a" or "an" do not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. Although some measures are recited in mutually different dependent claims, this does not indicate that a combination of these measures cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the internet or other wired or wireless telecommunication systems. Any reference signs in the claims shall not be construed as limiting the scope.