MRI with matching vibration state

Abstract

The invention relates to a magnetic resonance system (100) configured for acquiring magnetic resonance data from a subject (118). Execution of machine executable instructions (140) stored in a memory (134) causes a processor (130) to control the magnetic resonance system (100) using a set of waveforms and pulse sequence commands (142, 152) to prepare one or more hardware elements and / or a first vibrational state (211) of a subject (118). The preparing includes generating a vibrational matching gradient (200) that causes a first vibration (210) of the one or more hardware elements and / or the subject (118) when a net magnetization vector of the subject (118) is aligned along a longitudinal axis of a main magnetic field. The magnetic resonance system (100) is further controlled to acquire magnetic resonance data (144, 154) according to a magnetic resonance protocol. The acquiring includes sequentially generating at least two spin manipulation gradients (202, 204) for manipulating a phase of nuclear spins within the subject (118) when the net magnetization vector of the subject (118) includes a non-zero component in a transverse plane perpendicular to the longitudinal axis of the main magnetic field. A first spin manipulation gradient (202) of the at least two spin manipulation gradients is generated during the first vibrational state (211), and a second spin manipulation gradient (204) of the at least two spin manipulation gradients is generated during a second vibrational state (213) of the one or more hardware elements and / or the subject (118). The vibrational matching gradient (200) is used to match the second vibrational state (213) to the first vibrational state (211).

Description

TECHNICAL FIELD

[0001] The present invention relates to magnetic resonance data acquisition, in particular to matching of vibration states during magnetic resonance data acquisition. BACKGROUND

[0002] As part of a procedure for acquiring magnetic resonance data from within a subject, a large static magnetic field is used by a magnetic resonance (MR) scanner, such as for example a magnetic resonance imaging (MRI) system or a magnetic resonance spectroscopy (MRS) system, to generate a net magnetization vector within the subject. This large static magnetic field is referred to as the B0 field or main magnetic field. In addition, magnetic gradient fields and radio frequency pulses can be used to introduce spatial and temporal magnetic field variations and excitation of spin resonance that enable measurement of magnetic resonance data. Analysis of the acquired magnetic resonance data provides a non-invasive method for obtaining information about the internal structure and / or material composition of the subject. Various quantities or properties of the subject can thus be measured using MR. Various MR protocols can be implemented that define waveforms and pulse sequences to control the acquisition of magnetic resonance data with the MR system. Some MR techniques, for example techniques that encode for spin- spin displacement induced phase effects, require the application of strong magnetic gradients to the subject.

[0003] US patent US6201393 addresses the reduction of patient motion due to the patient being startled by a sudden sound. The known magnetic resonance imaging method proposes to avoid the patient being startled by the application of gradient pulses before the start of MRI image acquisition. Prior to a new MRI image acquisition, gradient pulses are applied at low amplitude and repeated with increasing amplitude until the sound is substantially the same as the sound produced during image acquisition. SUMMARY

[0004] The invention provides in independent claims a magnetic resonance imaging system, a computer program product and a method of operating a magnetic resonance imaging system. Embodiments are given in dependent claims.

[0005] In one aspect, the invention relates to a magnetic resonance system configured for acquiring magnetic resonance data from a subject in a data acquisition volume of the magnetic resonance system. The magnetic resonance system comprises a memory storing machine executable instructions and a set of waveforms and pulse sequence commands. The set of waveforms and pulse sequence commands are configured for generating a vibration matching gradient for causing a first vibration of one or more hardware elements of the magnetic resonance system and / or the subject. The vibration matching gradient is generated when a net magnetization vector of the subject is aligned along, i.e. parallel or anti-parallel to, a longitudinal axis of a main magnetic field generated by the magnetic resonance system.

[0006] The set of waveforms and pulse sequence commands are further configured for acquiring magnetic resonance data from the object according to a magnetic resonance protocol. The acquisition of the magnetic resonance data comprises generating at least two spin manipulation gradients for manipulating a phase of nuclear spins within the object in sequence. The at least two spin manipulation gradients are each generated when the net magnetization vector of the object comprises a non-zero component in a transverse plane perpendicular to the longitudinal axis of the main magnetic field.

[0007] The magnetic resonance system further comprises a processor for controlling the magnetic resonance system. Execution of the machine executable instructions causes the processor to control the magnetic resonance system using the set of waveforms and pulse sequence commands to prepare a first vibrational state of the one or more hardware elements and / or the object. The preparation comprises generating the vibration matching gradient that causes the first vibration of the one or more hardware elements and / or the object when the net magnetization vector of the object is aligned along the longitudinal axis of the main magnetic field.

[0008] Furthermore, the magnetic resonance data is acquired according to the magnetic resonance protocol. The acquisition comprises generating the at least two spin manipulation gradients for manipulating a phase of nuclear spins within the object in sequence when the net magnetization vector of the object comprises a non-zero component in the transverse plane perpendicular to the longitudinal axis of the main magnetic field. A first spin manipulation gradient of the at least two spin manipulation gradients is generated during the first vibrational state and a second spin manipulation gradient of the at least two spin manipulation gradients is generated during a second vibrational state of the one or more hardware elements and / or the object. The vibration matching gradient is used to match the second vibrational state to the first vibrational state.

[0009] Embodiments can have the beneficial effect that by using an additional vibration matching gradient to match the vibration states, it is possible to effectively compensate for vibration effects resulting from different vibration states that are excited during data acquisition. When using gradient coils to generate gradients, the gradient coils can cause mechanical vibrations. The mechanical vibrations can result in a vibration state for generating a subsequent gradient. This vibration state can be different from the vibration state for generating a previous gradient, resulting in vibration-induced phase effects that contaminate the measurement signal. Any pair of gradients between them that have a transverse magnetization component can be contaminated by vibration-induced phase effects.

[0010] A vibration matching gradient (VMG) is placed in front of the first spin manipulation gradient with appropriate timing, the tissue displacement pattern can become similar during both diffusion encoding gradients. The VMG is applied before the RF excitation pulse of the diffusion sensitizing module and does not disturb the transverse magnetization but only induces a mechanical vibration state. When the time interval between the VMG and the first spin manipulation gradient is equal to the diffusion time, the tissue displacement caused by the scanner table vibration during both diffusion gradients will be similar. Therefore, the accumulated phase during the diffusion encoding is similar and the occurring signal loss is mitigated. For other timings of the VMG, the mechanical vibration pattern during both diffusion gradients can become similar.

[0011] The present disclosure suggests to compensate for the vibration effects not based on a reduction of the vibrations but based on a matching of the vibration states using additional vibrations. To match a first vibration state with a second vibration state, an additional vibration matching gradient is used. The only purpose of the additional vibration matching gradient can be to induce a vibration in order to prepare a first vibration state that mimics a second vibration state. To prevent the vibration matching gradient from affecting the phase of the nuclear spins in the object, the vibration matching gradient is generated when the net magnetization vector is longitudinally oriented, i.e. when there is no transverse net magnetization.

[0012] This vibration matching gradient can be used to match the vibration states of any pair of spin manipulation gradients generated during the presence of at least some transverse net magnetization, i.e. when the net magnetization vector comprises a non-zero transverse component. Thus, the effect on the phase caused by the spin displacement accumulated by the spin manipulation gradients due to the difference between the vibration states can be reduced and / or avoided.

[0013] The vibration matching gradient, in particular a strong gradient as required for diffusion weighted MR, can be applied to the vibration states of the object and / or hardware components that equally affect the quality of the acquired magnetic resonance data.

[0014] The aforementioned vibrations can include mechanical vibrations of one or more hardware components of the magnetic resonance system as well as the object to be analyzed. The vibrations of the object as well as the vibrations of the hardware components of the MR system can lead to signal loss, measurement errors and artifacts. In particular, vibrations can occur when strong gradients are used, as in the case of diffusion gradients. Depending on the pulse sequence used, diffusion gradients can produce vibrations with amplitudes of up to 100 pm in the range of 20 Hz to 30 Hz, for example. Embodiments can have the beneficial effect of using a vibration matching gradient generated chronologically before a pulse sequence comprising a pair of spin manipulation gradients to mitigate vibration artifacts.

[0015] The object can be, for example, a human or a part of a human, such as a limb, located in the data acquisition volume. Furthermore, the object can be any kind of subject located within the data acquisition volume, for example a sample container with a sample.

[0016] According to embodiments, the second vibration state results from a second vibration caused by a first spin manipulation gradient of the at least two spin manipulation gradients. Thus, using a vibration matching gradient similar to the first spin manipulation gradient, a first vibration similar to the second vibration can be caused, resulting in a first vibration state matching the second vibration state.

[0017] According to embodiments, the magnetic resonance protocol can be a magnetic resonance imaging protocol configured for acquiring magnetic resonance imaging data. Embodiments can have the beneficial effect of mitigating vibration artifacts in magnetic resonance images using matching of vibration states. MRI provides a medical imaging technique that enables generating images or parametric maps of anatomical structures and / or physiological processes of a body of a subject, e.g., a human being.

[0018] According to embodiments, the magnetic resonance protocol can be a magnetic resonance spectroscopy protocol configured for acquiring magnetic resonance spectroscopy data. Embodiments can have the beneficial effect of mitigating vibration artifacts in magnetic resonance spectra using matching of vibration states. MRS (also known as nuclear magnetic resonance (NMR) spectroscopy) provides a non-invasive, non-ionizing radiation analysis technique that can be used, e.g., for studying metabolic changes. MRS can be used to determine the relative concentrations and / or physical properties of various biochemical substances often referred to as “metabolites” due to their role in metabolism. Like MRI, MRS can acquire signals, i.e., magnetic resonance data, from hydrogen protons, but other endogenous nuclei can also be used, e.g., phosphorus, carbon, nitrogen, sodium, or fluorine. Thus, MRS can enable obtaining chemical information, e.g., biochemical information about the tissues of a human body, whereas MRI provides structural information, such as information about the structure of a human body, e.g., the distribution of water and fat.

[0019] According to embodiments, the magnetic resonance protocol is sensitive to accumulation of spin- dephasing phases, wherein the at least two spin manipulation gradients are used to accumulate spin- dephasing phases, and the acquired magnetic resonance data encodes effects of the accumulated spin- dephasing phases.

[0020] Any contribution to spin dephasing due to differences between the vibration states of the motion spin manipulation gradients can contaminate the accumulated spin-dephasing phases. Using vibration matching gradients, such differences can be effectively avoided.

[0021] In case of a diffusion-weighted (DW) protocol with spin manipulation gradients in the form of diffusion gradients, using vibration matching gradients as described above can be beneficial, e.g., for mitigating signal loss, measurement errors, and / or artifacts.

[0022] DW allows to map the diffusion process of molecules, like water, in biological tissue in vivo and non-invasively. This molecular diffusion in tissue is typically dependent on interactions with obstacles, such as macromolecules, fibers and membranes. Thus, the pattern of molecular diffusion can reveal microscopic details about the tissue architecture. DW comprises the subsequent application of strong spin manipulation gradients in the form of diffusion gradient. Diffusion spins can change position between the application of diffusion gradients, thereby inducing diffusion spin dephasing and leading to a measurable signal attenuation.

[0023] Any motion during the diffusion sensitizing period of the diffusion weighted magnetic resonance data acquisition can cause additional accumulated phase and can eventually lead to signal cancellation due to intra-voxel dephasing. The amount of intra-voxel dephasing due to motion is proportional to the first diffusion gradient moment at the first approximation. The stronger the diffusion weighting, the stronger the dephasing effects in the presence of vibrations can be. Embodiments can have the beneficial effect of reducing these dephasing effects due to vibrations. Thus, artifacts of different vibration states excited by strong gradients, like diffusion gradients, can be avoided.

[0024] Vibration-induced artifacts can frequently occur depending on the sequence parameters and specific settings for diffusion weighted magnetic resonance. To reduce the effects of vibrations, acquisition parameters can be changed. However, such changes can negatively affect the SNR efficiency of the data acquisition. Furthermore, changes in the design of hardware components, like e.g. the gradient system or the table, have been considered to reduce the impact of vibrations. However, vibrations remain a problem even for state-of-the-art MR systems. The present disclosure suggests to mitigate artifacts by placing a vibration matching gradient prior to the diffusion preparation, e.g. according to a diffusion weighted magnetic resonance protocol. By appropriately choosing the temporal position of the vibration matching gradient, similar vibrations are induced by the vibration matching gradient as they are induced by the diffusion gradients, such that similar vibration states are generated whenever diffusion is applied.

[0025] The width of diffusion gradients can be much longer than the width of most imaging gradients. The degree of diffusion weighting increases with the b-value. The b-value reflects the strength and timing of the gradients used to generate a diffusion weighted image. The higher the b-value, the stronger the diffusion effects. To achieve large b-values, diffusion weighting gradients can be several tens of milliseconds in length, which inevitably leads to a rather long TE. However, long TE can reduce the SNR. To minimize the TE, the maximum gradient amplitudes available on the MR system can be used for DW MR. However, generating gradients with considerably larger amplitudes can cause non-negligible vibrations in the hardware components of the MR system and in the subject to be acquired MR data from.

[0026] However, the beneficial application of such vibration matching gradients is not limited to diffusion weighted magnetic resonance. According to embodiments, the magnetic resonance protocol can be one of: a diffusion weighted protocol, an apparent diffusion coefficient protocol, a diffusion tensor imaging protocol, a diffusion weighted spectroscopy protocol, a diffusion weighted preparation protocol, a high order diffusion model protocol, a phase-contrast velocity measurement protocol, a displacement encoding protocol, and a magnetic resonance elastography protocol.

[0027] According to embodiments, the execution of the machine executable instructions further causes the processor to control the magnetic resonance system to compute a representation of the acquired magnetic resonance data. The representation can comprise a graphical representation, such as an image, a graph, a spectrum, or a graph. Further, the representation can comprise a parameter of interest, like for example a scalar quantity, a vector, or a matrix. The parameter can for example be a modeled parameter that is derived as output from a computational model to which the acquired magnetic resonance is provided as input.

[0028] According to embodiments, the computation of the representation comprises using the acquired magnetic resonance data to compute one or more of: a diffusion weighted magnetic resonance image, an apparent diffusion coefficient map, a diffusion tensor image, an exponential apparent diffusion coefficient map, a fractional anisotropy image, a principal diffusion direction map, a fiber tracking map, a velocity map, a magnetic resonance spectrum, an elastography map, and a modeled parameter extracted using a signal model in cooperation with diffusion weighting, velocity encoding, and / or displacement encoding.

[0029] For example, the vibration compensation as suggested herein can be used for in-vivo fiber tracking. Fiber tracking can comprise computing one or more fiber tracking maps. For example, a seed in the back of the human brain can be used to compute fiber tracts. The resulting fiber tracts can for example be used clinically for surgery planning. Fiber tracts computed based on raw data acquired with the proposed vibration matching gradient can reveal more structures within the human brain compared to fiber tracts computed based on raw data acquired without the proposed vibration matching gradient. Fiber tracts determined using the proposed vibration matching gradient can for example be longer.

[0030] According to embodiments, the one or more hardware elements comprise a support element for supporting the subject in a data acquisition volume of the magnetic resonance system. Embodiments can have the beneficial effect of allowing efficiently and effectively compensating for differences in the state of vibration of the subject due to vibrations excited in the support element for supporting the subject. Vibrations of the support element, like a support table, can be directly transferred to the supported subject.

[0031] According to an embodiment, a first time interval between generating the vibration matching gradient and generating a first spin manipulation gradient of the at least two spin manipulation gradients is equal to a second time interval between generating the first spin manipulation gradient of the at least two spin manipulation gradients and generating a second spin manipulation gradient of the at least two spin manipulation gradients. Embodiments can have the beneficial effect that an efficient and effective matching of a first vibration state depending on the first spin manipulation gradient generated with the vibration matching gradient and a second vibration state depending on the second spin manipulation gradient generated with the first spin manipulation gradient is achieved. It has been found that the matching can be most efficient when the first and second time intervals at which the decay of the first and second vibrations occurs are equal.

[0032] According to an embodiment, an amplitude of the vibration matching gradient is equal to an amplitude of the first spin manipulation gradient of the at least two spin manipulation gradients. Embodiments can have the beneficial effect that an efficient and effective matching of the first and second vibration states is achieved when the amplitudes of the gradients causing the first and second vibrations leading to the first and second vibration states are equal. According to an embodiment, the amplitude of the vibration matching gradient is equal to the amplitudes of the two spin manipulation gradients.

[0033] According to an embodiment, the vibration matching gradient comprises a first waveform and the first spin manipulation gradient of the at least two spin manipulation gradients comprises a second waveform, wherein a slope of a flank of the first waveform is equal to a slope of a flank of the second waveform. Embodiments can have the beneficial effect that an efficient and effective matching of the first and second vibration states is achieved when the slopes of the flanks of the gradients causing the first and second vibrations leading to the first and second vibration states are equal. Equal slopes of flanks causing equal rates of change of the magnetic field can result in equal vibrations being caused. According to an embodiment, the slopes of all flanks of the first waveform are equal to the slopes of the flanks of the second waveform. A second spin manipulation gradient of the at least two spin manipulation gradients can comprise a third waveform. According to an embodiment, the slopes of the flanks of the first waveform can be equal to the slopes of the flanks of the second and third waveforms. According to an embodiment, the slopes of all flanks of the first waveform are equal to the slopes of the flanks of the second and third waveforms.

[0034] According to an embodiment, the waveforms can be rectangular, trapezoidal, sinusoidal or more complex waveforms. The waveforms can for example result from a combination and / or superposition of a plurality of individual waveforms. The individual waveforms can for example be gradient waveforms with different polarities, for example in case of acceleration compensation.

[0035] According to an embodiment, the first waveform is equal to the second waveform. Embodiments can have the beneficial effect that an efficient and effective matching of the first and second vibration states is achieved when the waveforms of the gradients causing the first and second vibrations leading to the first and second vibration states are equal. According to an embodiment, the first waveform is equal to the second waveform and a third waveform.

[0036] In another aspect, the application relates to a computer program product comprising machine executable instructions for execution by a processor controlling a magnetic resonance system configured for acquiring magnetic resonance data from a subject in a data acquisition volume of the magnetic resonance system. The computer program product further comprises a set of waveforms and pulse sequence commands. The set of waveforms and pulse sequence commands are configured for generating a vibration matching gradient for causing a first vibration of one or more hardware elements of the magnetic resonance system and / or the subject. The vibration matching gradient is generated when a net magnetization vector of the subject is aligned along, i.e. parallel or anti-parallel to, a longitudinal axis of a main magnetic field generated by the magnetic resonance system.

[0037] The set of waveforms and pulse sequence commands are further configured for acquiring magnetic resonance data from the subject according to a magnetic resonance protocol. The acquisition of the magnetic resonance data comprises generating at least two spin manipulation gradients for manipulating a phase of nuclear spins within the subject in succession. The at least two spin manipulation gradients are each generated when the net magnetization vector of the subject comprises a non-zero component in a transverse plane perpendicular to the longitudinal axis of the main magnetic field.

[0038] Execution of the machine executable instructions causes the processor to control the magnetic resonance system using the set of waveforms and pulse sequence commands to prepare a first vibration state of the one or more hardware elements and / or the subject. The preparation comprises generating the vibration matching gradient causing the first vibration of the one or more hardware elements and / or the subject when the net magnetization vector of the subject is aligned along the longitudinal axis of the main magnetic field.

[0039] Furthermore, the magnetic resonance data is acquired according to the magnetic resonance protocol. The acquisition comprises generating the at least two spin manipulation gradients for manipulating a phase of nuclear spins within the subject in succession when the net magnetization vector of the subject comprises a non-zero component in the transverse plane perpendicular to the longitudinal axis of the main magnetic field. A first spin manipulation gradient of the at least two spin manipulation gradients is generated during the first vibration state and a second spin manipulation gradient of the at least two spin manipulation gradients is generated during a second vibration state of the one or more hardware elements and / or the subject. The vibration matching gradient is for matching the second vibration state to the first vibration state.

[0040] According to embodiments, the computer program product further comprises machine executable instructions configured to implement any of the embodiments of the method described herein to be performed by the magnetic resonance system.

[0041] In another aspect, the application relates to a method for operating a magnetic resonance system configured for acquiring magnetic resonance data from a subject in a data acquisition volume of the magnetic resonance system. The magnetic resonance system comprises a memory storing machine executable instructions and a set of waveforms and pulse sequence commands. The set of waveforms and pulse sequence commands is configured for generating a vibration matching gradient for causing a first vibration of one or more hardware elements of the magnetic resonance system and / or the subject. The vibration matching gradient is generated while a net magnetization vector of the subject is aligned along, i.e. parallel or anti-parallel to, a longitudinal axis of a main magnetic field generated by the magnetic resonance system.

[0042] The set of waveforms and pulse sequence commands is further configured for acquiring magnetic resonance data from the subject according to a magnetic resonance protocol. The acquisition of the magnetic resonance data comprises generating at least two spin manipulation gradients for manipulating a phase of nuclear spins within the subject in sequence. The at least two spin manipulation gradients are each generated while the net magnetization vector of the subject comprises a non-zero component in a transverse plane perpendicular to the longitudinal axis of the main magnetic field.

[0043] The magnetic resonance system further comprises a processor for controlling the magnetic resonance system. Execution of the machine executable instructions causes the processor to control the magnetic resonance system according to the method using the set of waveforms and pulse sequence commands. The method comprises preparing a first vibration state of the one or more hardware elements and / or the subject. The preparing comprises generating the vibration matching gradient causing the first vibration of the one or more hardware elements and / or the subject while the net magnetization vector of the subject is aligned along the longitudinal axis of the main magnetic field.

[0044] Furthermore, the method comprises acquiring the magnetic resonance data according to the magnetic resonance protocol. The acquiring comprises generating the at least two spin manipulation gradients for manipulating a phase of nuclear spins within the subject in sequence while the net magnetization vector of the subject comprises a non-zero component in the transverse plane perpendicular to the longitudinal axis of the main magnetic field. A first spin manipulation gradient of the at least two spin manipulation gradients is generated during the first vibration state and a second spin manipulation gradient of the at least two spin manipulation gradients is generated during a second vibration state of the one or more hardware elements and / or the subject. The vibration matching gradient is for matching the second vibration state to the first vibration state.

[0045] According to embodiments, the method can comprise any of the embodiments of the method described herein to be performed by the magnetic resonance system.

[0046] It should be appreciated that one or more of the above-described embodiments of the present application can be combined, so long as the combined embodiments do not mutually exclude one another.

[0047] As will be appreciated by one of skill in the art, aspects of the present application can be embodied as a device, a method or a computer program product. Accordingly, aspects of the present application can 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 (in which case the entire disclosure can be referred to as a "circuit," "module" or "system"). Furthermore, aspects of the present application can take the form of a computer program product on one or more computer readable medium(s) having computer executable code embodied thereon.

[0048] Any combination of one or more computer readable medium(s) can be utilized. The computer readable medium can be a computer readable signal medium or a computer readable storage medium. "Computer readable storage medium" as used herein encompasses any tangible storage medium which can store instructions which are executable by a processor of a computing device. The computer readable storage medium can be referred to as a computer readable non-transitory storage medium. The 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 be able to store data which is able to be accessed by a processor of a computing device. Examples of computer readable storage media include, but are not limited to: a floppy disk, a magnetic hard disk drive, a solid state hard drive, flash memory, a USB thumb drive, Random Access Memory (RAM), Read Only Memory (ROM), an optical disk, a magneto-optical disk, and the register file of the processor. Examples of optical disks include Compact Disks (CDs) and Digital Versatile Disks (DVDs), such as CD-ROM, CD-RW, CD-R, DVD-ROM, DVD-RW, or DVD-R disks. The term computer readable storage medium also refers to various types of recording media capable of being accessed by a computer device. For example a recording medium can be a data storage device that can be accessed via a network or communication link. For example, a data storage device that can be accessed via the Internet or a Local Area Network. Computer executable code embodied on a computer readable medium can be transmitted using any appropriate medium, including but not limited to wireless, wired, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

[0049] A computer readable signal medium can 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 can take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium can be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport program for use by or in connection with an instruction execution system, apparatus, or device.

[0050] “Computer memory” or “memory” is an example of a computer readable storage medium. Computer memory is any memory accessible by a processor. “Computer storage” or “storage” is another example of a computer readable storage medium. Computer storage is any non-volatile computer readable storage medium. In some embodiments, computer storage can also be computer memory, or vice versa.

[0051] “Processor” as used herein encompasses an electronic component which acts to interpret and execute instructions. Reference to a computing device comprising “a processor” can thus be read to mean that the computing device includes one or more processors which can be of the same type as, or different from each other. The processor can be, for example, a multi-core processor. Processor can also refer to a collection of processors within a single computer system or distributed across multiple computer systems. The term computing device should also be read to include a collection or network of computing devices each including one or more processors. Computer executable code can be executed by multiple processors which can be within the same computing device or even distributed across multiple computing devices.

[0052] Computer executable code can comprise, for example, machine executable instructions or a program which causes a processor to perform certain activities. Computer executable code for carrying out operations for aspects of the application can be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The computer executable code can execute entirely on a 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 can 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 can be made to an external computer (for example, through the Internet using an Internet Service Provider).

[0053] 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 case, 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).

[0054] Aspects of the present invention are described with reference to the flow chart, diagram and / or block diagram of the method, device (system) and computer program product according to an embodiment of the present invention.Should be understood that, when applicable, each square frame or part of the square frame of flow chart, diagram and / or block diagram can be implemented by the computer program instruction in the form of computer executable code.It should also be understood that, when mutually non-exclusive, the combination of the square frames in different flow charts, diagrams and / or block diagrams can be combined.These computer program instructions can be provided to the processor of other programmable data processing devices of general-purpose computers, special-purpose computers or machines, so that the instruction executed via the processor of computer or other programmable data processing devices creates a unit for implementing the function / action specified in flow chart and / or one or more block diagram frames.

[0055] 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 operate in a specific manner so that the instructions stored in the computer-readable medium produce an article of manufacture including instructions for implementing the functions / actions specified in the flowchart and / or one or more block diagram blocks.

[0056] The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus, or other device to produce a computer-implemented process, such that the instructions executed on the computer or other programmable apparatus provide a process for the functions / actions specified in the flowchart and / or one or more block diagram blocks.

[0057] A "user interface" as used herein is an interface that allows a user or operator to interact with a computer or computer system. A "user interface" can also be referred to as a "human interface device." A user interface can provide information or data to the operator and / or receive information or data from the operator. A user interface can enable input from an operator to be received by the computer and can provide output to the operator from the computer. In other words, the user interface can allow an operator to control or manipulate a computer, and the interface can allow the computer to indicate the effects of the operator's control or manipulation. Display of 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, touchpad, pointing stick, graphics tablet, joystick, gamepad, webcam, headset, pedals, wired glove, remote control, and accelerometer are all examples of user interface components that enable receiving information or data from an operator.

[0058] A "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 can allow the processor to send control signals or instructions to the external computing device and / or apparatus. A hardware interface can also enable the processor to exchange data with the 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 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.

[0059] A "display" or "display device" as used herein encompasses an output device or user interface suitable for displaying images or data. A display can output visual, audio, and / or tactile data. Examples of displays include, but are not limited to: a computer monitor, a television screen, a touchscreen, a tactile electronic display, a Braille screen, a cathode ray tube (CRT), a storage tube, a bistable display, e-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.

[0060] Magnetic resonance (MR) data is defined herein as the measurement of radio frequency signals emitted by nuclear spins recorded using an antenna of a magnetic resonance system during a magnetic resonance scan. A magnetic resonance imaging (MRI) image or MR image is defined herein as a reconstructed two- or three-dimensional visualization of anatomical data contained within magnetic resonance imaging data. This visualization can be performed using a computer. BRIEF DESCRIPTION OF DRAWINGS

[0061] In the following, a preferred embodiment of the present application will be described by way of example only and with reference to the accompanying drawings, in which:

[0062] Figure 1 An example of a magnetic resonance system is illustrated;

[0063] Figure 2 An example of a magnetic resonance system is illustrated;

[0064] Figure 3 An example pulse sequence is illustrated;

[0065] Figure 4 An example dependence of the vibration compensation on T 振动 is illustrated;

[0066] Fig. 5 illustrates an example dependence of the vibration compensation on the b-value;

[0067] Figure 6 A flowchart of a method of a magnetic resonance system illustrating the operation Figure 1 and Figure 2 is shown;

[0068] Fig. 7 illustrates an example dependence of the vibration compensation on T 振动 ;

[0069] Fig. 8 illustrates an example vibration compensation;

[0070] Fig. 9 illustrates an example vibration compensation.

[0071] Figure 10 Results from a phantom scan are shown.

[0072] Figure 11 Mean ADC values obtained in the tibial bone marrow are shown.

[0073] LIST OF REFERENCE SIGNS

[0074] 100 magnetic resonance system

[0075] 104 magnet

[0076] 106 bore of the magnet

[0077] 108 data acquisition volume

[0078] 109 region of interest

[0079] 110 magnetic field gradient coil

[0080] 112 magnetic field gradient coil power supply

[0081] 114 radio frequency coil

[0082] 116 transceiver

[0083] 118 subject

[0084] 119 sample

[0085] 120 subject support

[0086] 126 computer system

[0087] 128 hardware interface

[0088] 130 processor

[0089] 132 user interface

[0090] 134 computer memory

[0091] 140 machine executable instructions

[0092] 142 waveform and pulse sequence commands

[0093] 144 magnetic resonance imaging data

[0094] 146 magnetic resonance image

[0095] 152 waveform and pulse sequence commands

[0096] 154 magnetic resonance imaging / spectroscopy data

[0097] 156 magnetic resonance image / spectroscopy

[0098] 200 wobble matching gradient

[0099] 201 pulse sequence

[0100] 203 pulse sequence

[0101] 202 spin manipulation gradient

[0102] 204 spin manipulation gradient

[0103] 206 radio frequency pulse

[0104] 208 radio frequency pulse

[0105] 210 first wobble

[0106] 211 first vibration state

[0107] 212 second vibration

[0108] 213 second vibration state

[0109] 300 2D imaging slice

[0110] 302 indication region

[0111] 304 indication region

[0112] 600 generating a vibration matching gradient

[0113] 602 acquiring magnetic resonance data using at least two spin manipulation gradients DETAILED DESCRIPTION

[0114] In these drawings, like referenced numerals in the different figures indicate like elements or perform the same function. If functionally equivalent there will be no necessarily discussion of previously discussed elements in later figures.

[0115] Figure 1 An example of a magnetic resonance system 100 is illustrated. The magnetic resonance system 100 comprises a magnet 104. The magnet 104 is a superconducting cylindrical type magnet with a bore 106 through it. The use of different types of magnets is also possible. For example, the use of both split cylindrical magnets and so-called open magnets is possible. A 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 can for example be used in combination with charged particle beam therapy. An open magnet has two magnet parts, one above the other, with a space between them large enough to receive a subject 118 to be imaged, the arrangement of the two parts regions is similar to the arrangement of Helmholtz coils. Open magnets are popular because the subject is less confined. Inside the cryostat of the cylindrical magnet there is a collection of superconducting coils. Within the bore 106 of the cylindrical magnet 104 there is a data acquisition volume 108, also referred to as the imaging zone, where the magnetic field is strong and uniform enough to perform magnetic resonance imaging. A region of interest 109 is shown within the imaging zone 108. Magnetic resonance data is typically acquired for the region of interest. The subject 118 is shown as being supported by a subject support element 120 such that at least part of the subject 118 is within the imaging zone 108 and the region of interest 109. In this example the support element 120 is a support table. In other examples other designs and / or combinations of support elements can be used to support and position the subject 118 within the imaging zone 108 and the region of interest 109.

[0116] Within the bore 106 of the magnet are a set of magnetic field gradient coils 110 which are used to generate magnetic field gradients, for example, pulsed magnetic field gradients. The set of magnetic field gradient coils 110 are used, for example, to acquire magnetic resonance data to spatially encode magnetic spins within an imaging zone 108 of the magnet 104. The magnetic field gradient coils 110 are connected to a magnetic field gradient coil power supply 112. The magnetic field gradient coils 110 are intended to be representative. Typically, the magnetic field gradient coils 110 comprise separate sets of coils for spatially 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 110 is controlled as a function of time and can be ramped or pulsed.

[0117] Adjacent to the imaging zone 108 is a radio frequency coil 114 which is used to manipulate the orientation of magnetic spins within the imaging zone 108 and to receive radio frequency transmissions from spins also within the imaging zone 108. The radio frequency antenna can comprise multiple coil elements. The radio frequency antenna can also be referred to as a channel or an antenna. The radio frequency coil 114 is connected to a radio frequency transceiver 116. The radio frequency coil 114 and the radio frequency transceiver 116 can be replaced by separate transmit and receive coils and separate transmitters and receivers. It is to be understood that the radio frequency coil 114 and the radio frequency transceiver 116 are representative. The radio frequency coil 114 is intended to also represent a dedicated transmit antenna and a dedicated receive antenna. Similarly, the transceiver 116 can also represent separate transmitters and separate receivers. The radio frequency coil 114 can also have multiple receive / transmit elements and the radio frequency transceiver 116 can have multiple receive / transmit channels. For example, if parallel imaging techniques such as SENSE are performed, the radio frequency coil 114 will have multiple coil elements.

[0118] In this example, the object 118 is positioned so that the chest region of the object is located within the region of interest 109. In other examples, other parts of the body of the object 118 can be positioned in the region of interest 109. In other examples, the object 118 can be some other object, such as, for example, a sample container as shown including a sample 119. Figure 2

[0119] ​The transceiver 116 and gradient controller 112 are shown connected to a hardware interface 128 of a computer system 126. The computer system also includes a processor 130 that communicates with the hardware interface 128, a memory 134, and a user interface 132. The memory 134 can be any combination of memories accessible to the processor 130. This can include things like main memory, cache memory, and non-volatile memory (such as flash RAM, a hard drive, or other storage devices). In some examples, the memory 134 can be considered a non-transitory computer-readable medium. The user interface 132 can enable the processor 104 to display or render images and other information that can be provided to a user or operator. The user interface 132 can also be used to receive control or input data from the user or operator. The user interface 132 can include a display for selecting and / or configuring pulse sequences and displaying the results of the magnetic resonance data acquisition and / or processing performed by the magnetic resonance system 100.

[0120] The memory 134 is shown to contain machine executable instructions 140. The machine executable instructions 140 enable the processor 130 to control the operation and functionality of the magnetic resonance system 100 to perform a magnetic resonance imaging procedure. The machine executable instructions 140 can also enable the processor 130 to perform various data analysis and computational functions, such as data processing and image processing tasks. The memory 134 is also shown to contain a set of waveforms and pulse sequence commands 142. The waveforms and pulse sequence commands 142 are instructions or data that can be converted into instructions that enable the processor 104 to control the magnetic resonance system 100 to acquire magnetic resonance imaging data 144. The set of waveforms and pulse sequence commands 142 can be configured to generate a vibration matching gradient for causing a first vibration of one or more hardware elements of the magnetic resonance system 100 and / or the object 118. The vibration matching gradient is when the net magnetization vector of the object 118 is aligned along the longitudinal axis of the main magnetic field generated by the magnetic resonance system 100, i.e., parallel or anti-parallel to the longitudinal axis of the main magnetic field generated by the magnetic resonance system 100. The set of waveforms and pulse sequence commands 142 can also be configured to acquire magnetic resonance data from the object according to a magnetic resonance protocol. The acquisition of the magnetic resonance data 144 includes generating at least two spin manipulation gradients for manipulating the phase of nuclear spins within the object 118 in the imaging volume 108 in accordance with a magnetic resonance imaging protocol. The at least two spin manipulation gradients are generated when the net magnetization vector of the object includes a non-zero component of the net magnetization in a transverse plane perpendicular to the longitudinal axis of the main magnetic field. The magnetic resonance imaging protocol can be any of the magnetic resonance imaging protocols described herein. The magnetic resonance imaging protocol may, for example, be sensitive to the accumulation of spin- displacement-induced phase. The at least two spin manipulation gradients can be used to accumulate spin-displacement-induced phase, and the acquired magnetic resonance data can include the effect of the accumulated spin-displacement-induced phase encoded therein. The memory 134 is also shown to contain the magnetic resonance imaging data 144 acquired by controlling the magnetic resonance system 100 with the waveforms and pulse sequence commands 142. In addition, the memory 110 can include one or more representations 146 of the acquired magnetic resonance data 144, such as graphical representations in the form of magnetic resonance images reconstructed using the acquired magnetic resonance imaging data 144. The one or more representations 146 can include any of the representations described herein.

[0121] Figure 2 A further exemplary embodiment of the magnetic resonance system 100 is shown Figure 1 The object 118 is provided in the form of a sample container holding a sample 119. Alternatively, the object 118 can be some other object or human being, such as Figure 1As shown, it is at least partially located within the data acquisition volume 108 and the region of interest 109. The machine executable instructions 140 stored in the memory 134 can enable the processor 130 to control the operation and functionality of the magnetic resonance system 100 to perform magnetic resonance imaging / spectroscopy using the waveforms and pulse sequence commands 152. The waveforms and pulse sequence commands 152 are instructions or data that can be converted into instructions that enable the processor 104 to control the magnetic resonance system 100 to acquire magnetic resonance imaging / spectroscopy data 154. The set of waveforms and pulse sequence commands 152 can be configured to generate a spin matching gradient for causing first vibrations while the net magnetization is longitudinally oriented without any transverse net magnetization. The set of waveforms and pulse sequence commands 152 can also be configured to acquire magnetic resonance imaging / spectroscopy data 154 from the object 118 in the data acquisition volume 108 according to a magnetic resonance imaging / spectroscopy protocol. The magnetic resonance imaging / spectroscopy protocol can be any of the magnetic resonance imaging / spectroscopy protocols described herein according to which the data acquisition includes generating at least two spin manipulation gradients for manipulating the phase of nuclear spins within the object 118 in the data acquisition volume 108 in sequence while there is at least some transverse net magnetization. The memory 110 is also shown to contain the magnetic resonance imaging / spectroscopy data 154 that has been acquired by controlling the magnetic resonance system 100 with the waveforms and pulse sequence commands 152. In addition, the memory 110 can include one or more representations 156 of the acquired magnetic resonance data 154, such as a magnetic resonance spectrum, a magnetic resonance image, or some parameter computed using the acquired magnetic resonance imaging / spectroscopy data 154.

[0122] Figure 3An exemplary pulse sequence 201 generated according to the set of waveforms and pulse sequence commands is illustrated. The pulse sequence 201 is supplemented by the generated vibration matching gradient 200 while the net magnetization vector of the object is longitudinally aligned, i.e. before any RF pulse has been applied or after the effects thereof on the net magnetization have dissipated. The pulse sequence 201 further comprises a pair of spin manipulation gradients 202, 204 for manipulating the phase of the nuclear spins, which are generated when the net magnetization vector comprises a non-zero transverse component, i.e. a non-zero component in a transverse plane perpendicular to the longitudinal axis of the net magnetic field, due to an RF pulse. The pulse sequence 201 may, for example, be implemented in the form of a vibration compensated DW spin echo (diffusion weighted spin echo) sequence, i.e. a DW spin echo sequence that has been extended by a vibration compensation gradient in the form of the vibration matching gradient 200. The DW spin echo sequence 201 comprises a 90° RF pulse and a 180° RF pulse. Symmetrically distributed around the 180° RF pulse are two spin manipulation gradients 202, 204 in the form of diffusion gradients spaced apart from each other in time by a time interval Δ. The vibration matching gradient 200 can have the same waveforms, i.e. shape and amplitude, as the diffusion gradients 202, 204. The time interval T 振动 may be equal to Δ.

[0123] The gradients 200, 202, 204 of the sequence 201 can each cause tissue displacement, i.e. vibration of the object. Without the vibration matching gradient 200, the first diffusion gradient 202 can be generated in a vibration state of the object with negligible vibration. However, the first diffusion gradient 202 can cause mechanical vibrations in the hardware components of the MR system and in the object, resulting in a tissue displacement 212. The tissue displacement 212 can decay over time, i.e. during the time interval Δ, resulting in a vibration state 213 at which the second diffusion gradient 202 is generated, which is significantly different from the vibration state at which the first diffusion gradient 202 is generated. Any magnetic resonance protocol that is sensitive to the accumulation of spin displacement induced phase will be negatively affected by this difference between the vibration states. When the vibration matching gradient 200 is added, the vibration matching gradient 200 causes additional vibration, resulting in a tissue displacement 210 that decays over time, i.e. during the time interval T 振动 . The decaying tissue displacement 210 results in a vibration state 211 at which the first diffusion gradient 202 is generated, which matches the subsequent vibration state 213. In other words, the displacements 210, 212 are similar for both diffusion gradients 202, 204. Thus, a negative effect on the accumulation of spin displacement induced phase due to the difference between the vibration states 211, 213 can be effectively prevented.

[0124] Figure 4 The vibration compensation is illustrated for a time interval T 振动Example dependencies for Figure 4 In the analysis shown, a high-b-value DW TSE sequence was used to measure lipid ADC in a water-fat phantom. The high-b-value DW TSE sequence consists of DW stimulated echo preparation with four 90° RF pulses and a monopolar diffusion-sensitizing gradient, followed by 2D-TSE readout. A vibration-matched gradient was generated prior to the diffusion preparation to match the diffusion-sensitizing gradient.

[0125] The water-fat phantom is an 80% fat fraction water-fat phantom. It contains 800 ml of oil, 200 ml of water, 4 ml of Tween 80, and 1 g of sodium benzoate. Emulsification was performed using a colloid mill at 6000 rpm. The phantom was scanned using a 3T MR system with an 8-channel wrist coil on the MR system's support table.

[0126] Time interval T 振动 50000s / mm under strong diffusion weighting 2 The b value is varied from 40ms to 525ms in order to determine the optimal T 振动 Other parameters used include (120mm) 2 Field of view (FOV), 2×2×10mm 3 voxel size, 2000ms repetition time (TR), 23ms echo time (TE), 220ms TM Prep and TE of 61ms Prep .

[0127] Figure 4 Depicts the time interval T 振动 Average signal evolution in DWI raw images of water-fat phantoms of different lengths. The depicted signals are relative signals, i.e., the signal with vibration compensation versus the signal without vibration compensation. For a time interval T equal to the time interval Δ between the first and second sensitization gradients (also called diffusion time), 振动 , a single global maximum with a relative signal amplitude of 117% of the signal value without vibration compensation can be observed. Local maxima with relative signal amplitudes greater than 100% but less than 117% are also shown. These local maxima are similar to the eigenfrequencies of the object being analyzed. Therefore, as T 振动 = Δ alternative, the time interval T of one of the local maxima 振动 can be determined and used for vibration compensation. However, the most effective and therefore preferred choice may be T 振动 =Δ.

[0128] FIG5 illustrates an exemplary dependence of vibration compensation on the b value. Figure 4As shown, a high b-value DW TSE sequence was used to measure lipid ADC in a water-fat-body phantom. 5000 s / mm was used without and with vibration-matched gradients. 2 The step can be from 5000s / mm 2 Up to 50,000s / mm 2 The b value within the range is measured ADC. Other parameters used include (120mm) 2 Field of view (FOV), 2×2×10mm 3 voxel size, TR of 2000ms, TE of 23ms, TM of 220ms Prep and TEPrep of 61 ms. The observed signal oscillations were at a frequency of approximately 11 Hz.

[0129] exist Figure 5A In the figure, the logarithm of the signal decay curve and the average ADC value of the measurement without using the vibration matching gradient are shown. The fitting of the ADC values ​​yields 1.1e -0.5 mm 2 / s. Figure 5B In the figure, the logarithm of the signal decay curve and the average ADC value of the measurement using the vibration matching gradient are shown. In this case, the fitting of the ADC value yields 7.8e -0.6 mm 2 / s. For Figure 5C and Figure 5D The measurements shown are included in the MR system and used to Figure 5A and 5B The standard scanner table for the measurement results has been replaced by a wooden support structure. This wooden support structure decouples the object located thereon from vibrations introduced by the MR system (e.g. due to the gradients generated by the MR system). Figure 5C In the figure, the logarithm of the signal decay curve and the average ADC value of the measurement for the wooden support structure without using the vibration matching gradient are shown. The fitting of the ADC values ​​yields 6.2e -0.6 mm 2 / s. Figure 5B In the figure, the logarithm of the signal decay curve and the average ADC value of the measurement for a wooden support structure using a vibration matching gradient are shown. In this case, the fitting of the ADC values ​​yields 6.1e -0.6 mm 2 / s. Therefore, when Figure 5A Measurements performed on the standard scanner stage in Figure 5C The ADC values ​​are 70% higher when compared to measurements performed on a wooden support structure in

[15] , each without any vibration compensation using a vibration matching gradient. Figure 5D In comparison, Figure 5B25% higher ADC value was measured. Figure 5C and 5D Only a minor difference of approximately 2% is observable between the wooden support structure without and with the vibration compensation gradient. This illustrates the effectiveness of vibration compensation using the method proposed herein. The ADC values ​​determined using the standard scanner table with the proposed vibration compensation method match the ADC values ​​determined using the wooden support structure (i.e., the ADC values ​​determined for the subject decoupled from the vibrations introduced by the MR system) significantly better than the ADC values ​​determined using the standard scanner table without the proposed vibration compensation method.

[0130] Figure 6 The diagram shows the operation Figure 1 and Figure 2 A flow chart of a method for an MR system is provided. In step 600, a first vibration state is prepared for one or more hardware elements of the MR system and / or a subject in a data acquisition volume of the MR system. To this end, a vibration matching gradient is generated. The vibration matching gradient is generated when the net magnetization vector of the subject is aligned parallel or antiparallel to the longitudinal axis of a main magnetic field generated by the magnetic resonance system. The generation of the vibration matching gradient induces a first vibration of the one or more hardware elements and / or the subject, thereby resulting in the first vibration state. In step 602, magnetic resonance data is acquired from the subject according to a magnetic resonance protocol (e.g., a magnetic resonance protocol sensitive to the accumulation of phase caused by spin displacement). When the net magnetization vector of the subject includes a non-zero component of the net magnetization in a transverse plane perpendicular to the longitudinal axis of the main magnetic field, at least two spin manipulation gradients for manipulating the phase of nuclear spins in the subject are sequentially generated according to the magnetic resonance protocol. The first spin manipulation gradient is generated during the first vibration state prepared using the vibration matching gradient. Because the first spin manipulation gradient itself also induces vibration (i.e., a second vibration) of the one or more hardware elements and / or the subject, a second vibration state is generated by the second vibration, during which the second spin manipulation gradient is generated. The vibration matching gradient of step 600 is configured to simulate a second vibration state using a first vibration state, thereby resulting in matching of the two states. In addition, one or more representations of the acquired magnetic resonance data can be calculated. The calculated representations can include graphical representations (such as images, graphs, spectra, or graphs), and / or the calculated representations can include parameters of interest, such as, for example, scalers, vectors, or matrices.

[0131] FIG7 illustrates the Figure 4 The setting of vibration compensation for T 振动 Example dependencies of . Figure 7A , DW images of a fat-water-phantom using a high b-value DW TSE sequence without applying a vibration-matched gradient are shown. Figure 7BDW images of a fat-water phantom using a high b-value DW TSE sequence with vibration-matched gradients are shown. 振动 Selected as T 振动 =205ms. T 振动 =205ms corresponds to Figure 4 The global minimum of the relative signal amplitude is depicted in , where the signal with vibration compensation is approximately half of the signal without vibration compensation. Figure 7C Also shown is a DWI image of a fat-water phantom using a high b-value DW TSE sequence with vibration-matched gradients. Figure 7C In the time interval T 振动 Selected as T 振动 =255ms. T 振动 =255ms corresponds to Δ, that is, Figure 4 The global maximum of the relative signal amplitude of 117% is depicted in FIG.

[0132] FIG8 illustrates exemplary vibration compensation in the context of analyzing in vivo lipid ADC in a human leg. Figure 8A The location of a 2D imaging slice 300 through the lower leg is shown. Figure 8B The corresponding fat fraction map acquired at this location is shown. Figure 8C and 8D It shows that without applying vibration matching gradient ( Figure 8C ) and when applying vibration matching gradient ( Figure 8D ADC graph obtained with ). Measurements were performed using an 8-channel end coil with the following parameters: (140 mm) 2 FOV (2.2mm) 3 voxel size, 1800ms TR, 10ms TE, 220ms TM Prep and TE of 61ms Prep The b value is related to Figure 4 , the same water-fat-body phantom experiments as shown in Figures 5 and 7. The scanning time was 4:32 min. Figure 8C and Figure 8D The comparison of 300 and 301 illustrates that the subcutaneous fat ADC is qualitatively more non-uniform without the vibration matching gradient, particularly in the region indicated by ellipse 302. More uniform ADC values ​​in the subcutaneous fat are observed with the vibration matching gradient, particularly in the region indicated by ellipse 302. Figure 8D For different segmented areas of the calf, Figure 8E The average ADC values ​​are shown in Figure 8F The corresponding standard deviations are shown in Figure 8E and Figure 8F On the left frame axis of the , the values ​​determined without vibration compensation are plotted, whileFigure 8E and Figure 8F On the right frame axis of , the values ​​determined with vibration compensation are plotted. In subcutaneous fat, according to Figure 8E , a 5% overall decrease and a 12% local decrease were observed in ADC. Figure 8F A 16% global decrease and a 43% local decrease in the ADC standard deviation were observed with the vibration-matched gradient. In the tibial and fibular bone marrow, only minor differences were observed. In summary, global and local differences in ADC values ​​and standard deviation were observed in subcutaneous fat (see Figure 8C and Figure 8D The values ​​decrease for the more rigid regions of the bone marrow in the tibia and fibula (region 302), while they remain almost constant for the more rigid regions of the bone marrow in the tibia and fibula.

[0133] FIG. 9 illustrates exemplary vibration compensation for in vivo high b-value DWI in the human brain. Figure 9A shows iso DWI of the brain without applied vibration matching gradients, whereas Figure 9B The iso DWI of the brain is shown with the application of vibration matching gradients. A 32-channel head coil with a diameter of 230 × 230 × 114 mm was used. 3 FOV, 1.5×1.5×4mm 3 The measurement was performed with a voxel size of 10,000 s / mm² using DW EPI (echo-planar imaging) with a TR of 6,070 ms, a TE of 124 ms, and a half-scan factor of 0.7. It was possible to use the same minimum TE and TR with and without the vibration compensation gradient without a severe time penalty (i.e., the time increased from 3:20 min to 3:27 min). The effect of applying the vibration matching gradient is particularly visible in the indicated region 304.

[0134] ADC measurements in phantoms

[0135] To evaluate the performance of the proposed approach, lipid ADC values were estimated within WF phantoms (6000 and 11000 rpm). Three different phantoms were used in the phantom measurements. For the lipid diffusion property measurements, two WF phantoms with a fat fraction of 80% were created (content: 800 mL sunflower oil, 200 mL water, 4 mL Tween 80 and 1 g sodium benzoate). Emulsification was performed with a colloid mill at 6000 and 11000 revolutions per minute (rpm). The obtained phantoms create different lipid droplet sizes and thus different viscosities. The experiments were performed on the scanner table and on a decoupling table made of wood, which decouples the sample and the vibrating scanner table. The following two interferometer experiments were performed with the interferometer setup to quantify the effects under investigation. The voxel of interest was placed in the middle of the WF phantom material. The experiments were repeated for the same three different measurement scenarios as performed in the interferometer measurements and with the same scan parameters. The additional sequence parameters utilized were: 16 averages per b-value (half of the averages with positive polarity and the other half with negative polarity), 1 warm-up cycle, b-values: 10000-20000-40000-60000 s / mm2, 2: 48 min scan time per phantom. Diffusion gradients were applied simultaneously on all three axes to minimize TE. 2

[0136] Figure 10 The results from the phantom scans are shown. Assuming that the phantoms on the decoupling table are not affected by the vibration artifacts, the ADC values on the decoupling table represent the true lipid ADC values. In the 6000 rpm phantom, the DW MRS experiment on the scanner table produced a 119.0% overestimation of the ADC values, while only a 5.5% relative error was observed on the scanner table with the VMG. In the 11000 rpm phantom, the obtained lipid ADC values were very similar between the different measurement scenarios and only a relative difference below 1% was observed.

[0137] ADC measurements in vivo

[0138] The bone marrow in the tibia of three healthy volunteers (Volunteer 1 : 24 years / 85 kg, Volunteer 2: 29 years / 57 kg, Volunteer 3: 28 years / 80 kg) was scanned using an 8-channel end coil without and with the VMG and with different additional weights (0 / 10 / 20 kg) placed on the scanner table. By changing the load of the scanner table, the mechanical vibrations were changed and the influence of the vibrations on the DW measurements could be investigated. Each scan was repeated three times to access the reproducibility of the ADC measurements. The DW MRS voxel was placed about 1 cm below the growth plate in the tibial marrow and was performed with the same parameters as for the phantom scans (including the same diffusion directions and b-values). Thereafter, the lipid ADC was extracted without and with the VMG for each load. ​

[0139] Figure 11 The mean obtained ADC values in the tibial marrow of three repeated measurements at different loadings of the scanner table are shown with the corresponding standard deviations. Without VMG, a dependency of the measured ADC values on the additional loading of the scanner table is observed and a larger standard deviation of the lipid ADC estimates is observed. The ADC values from different measurement combinations are comparable with and without VMG. However, in case the measurements without VMG are compared to the measurements with VMG, the coefficient of variation is reduced by 34.9% (volunteer 1), 18.9% (volunteer 2) and 24.0% (volunteer 3) in the three volunteers.

[0140] While the application 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 application is not limited to the disclosed embodiments.

[0141] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed application, from a study of the drawings, the disclosure, and the 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. The mere fact that measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. A computer program can be stored and / or 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 can also be distributed in other forms, such as via the internet or other wired or wireless telecommunication systems. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A magnetic resonance system (100) configured to acquire magnetic resonance data from a subject (118) in a data acquisition volume (108) of the magnetic resonance system (100), the magnetic resonance system (100) comprising: a memory (134) storing machine-executable instructions (140) and a set of waveform and pulse sequence commands (142, 152), wherein the set of waveform and pulse sequence commands (142, 152) is configured to generate a vibration matching gradient (200) when a net magnetization vector of the object (118) is aligned along a longitudinal axis of a main magnetic field generated by the magnetic resonance system (100), the vibration matching gradient being used to induce a first vibration (200) of one or more hardware elements of the magnetic resonance system (100) and / or the object (118) 10), wherein the set of waveform and pulse sequence commands (142, 152) is further configured for acquiring magnetic resonance data (144, 154) from the subject (118) according to a magnetic resonance protocol, wherein the acquiring of the magnetic resonance data (144, 154) comprises sequentially generating at least two spin manipulation gradients (202, 204) for manipulating the phase of nuclear spins within the subject when the net magnetization vector of the subject (118) includes a non-zero component of the net magnetization in a transverse plane perpendicular to the longitudinal axis of the main magnetic field, - a processor (130) for controlling the magnetic resonance system (100), wherein execution of the machine-executable instructions (140) causes the processor (130) to control the magnetic resonance system (100) using the set of waveform and pulse sequence commands (142, 152) to: - preparing a first vibration state (211) of the one or more hardware elements and / or the object (118), the preparation comprising generating the vibration matching gradient (200) causing the first vibration (210) of the one or more hardware elements and / or the object (118) when the net magnetization vector of the object (118) is aligned along the longitudinal axis of the main magnetic field, - acquiring the magnetic resonance data (144, 154) according to the magnetic resonance protocol, wherein the acquiring comprises sequentially generating the at least two spin manipulation gradients (202, 204) for manipulating the phase of nuclear spins in the object (118) when the net magnetization vector of the object (118) comprises a non-zero component in the transverse plane perpendicular to the longitudinal axis of the main magnetic field, wherein a first spin manipulation gradient (202) of the at least two spin manipulation gradients is generated during the first vibration state (211), and a second spin manipulation gradient (204) of the at least two spin manipulation gradients is generated during a second vibration state (213) of the one or more hardware elements and / or the object (118), the second vibration state resulting from a second vibration caused by the first spin manipulation gradient of the at least two spin manipulation gradients, wherein the vibration matching gradient (200) is used to match the second vibration state (213) to the first vibration state (211).

2. The magnetic resonance system (100) according to claim 1, wherein The magnetic resonance protocol is sensitive to accumulation of spin-shift induced phase, wherein the at least two spin manipulation gradients (202, 204) are used to accumulate the spin-shift induced phase, and the acquired magnetic resonance data encodes the effect of the accumulated spin-shift induced phase.

3. The magnetic resonance system (100) according to claim 2, wherein: The magnetic resonance protocol is one of the following: a diffusion weighted protocol, an apparent diffusion coefficient protocol, a diffusion tensor imaging protocol, a diffusion weighted spectroscopy protocol, a diffusion weighted preparation protocol, a high-order diffusion model protocol, a phase contrast velocimetry protocol, a displacement encoding protocol, and a magnetic resonance elastography protocol.

4. The magnetic resonance system (100) according to any one of claims 1 to 3, wherein: The execution of the machine-executable instructions (140) further causes the processor (130) to control the magnetic resonance system (100) to compute a representation (146, 156) of the acquired magnetic resonance data (144, 154).

5. The magnetic resonance system (100) according to claim 4, wherein: The calculation of the representation (146, 156) includes using the acquired magnetic resonance data (144, 145) to calculate one or more of the following: a diffusion-weighted magnetic resonance image, an apparent diffusion coefficient map, a diffusion tensor image, an exponential apparent diffusion coefficient map, a fractional anisotropy image, a principal diffusion direction map, a fiber tracking map, a velocity map, a magnetic resonance spectrum, an elastogram, and modeling parameters extracted using a signal model in conjunction with diffusion weighting, velocity encoding, and / or displacement encoding.

6. The magnetic resonance system (100) according to any one of claims 1 to 3, wherein: The one or more hardware elements include a support element (120) for supporting the object (118) in the data acquisition volume (108) of the magnetic resonance system (100).

7. The magnetic resonance system (100) according to any one of claims 1 to 3, wherein: A first time interval between generating the vibration matching gradient (200) and generating the first spin manipulation gradient (202) of the at least two spin manipulation gradients is equal to a second time interval between generating the first spin manipulation gradient (202) of the at least two spin manipulation gradients and generating the second spin manipulation gradient (204) of the at least two spin manipulation gradients.

8. The magnetic resonance system (100) according to any one of claims 1 to 3, wherein: The amplitude of the vibration matching gradient (200) is equal to the amplitude of the first spin manipulation gradient (202) of the at least two spin manipulation gradients.

9. The magnetic resonance system (100) according to any one of claims 1 to 3, wherein: The vibrationally matched gradient (200) includes a first waveform, and a first spin manipulation gradient (202) of the at least two spin manipulation gradients includes a second waveform, wherein a slope of a side of the first waveform is equal to a slope of a side of the second waveform.

10. The magnetic resonance system (100) according to claim 9, wherein: The first waveform is equal to the second waveform.

11. A computer program product comprising machine-executable instructions (140) for execution by a processor (130) controlling a magnetic resonance system (100), the magnetic resonance system (100) being configured to acquire magnetic resonance data from a subject (118) in a data acquisition volume (108) of the magnetic resonance system (100). in, The computer program product further comprises a set of waveform and pulse sequence commands (142, 152), wherein the set of waveform and pulse sequence commands (142, 152) are configured to generate a vibration matching gradient (200) when a net magnetization vector of the object (118) is aligned along a longitudinal axis of a main magnetic field generated by the magnetic resonance system (100), the vibration matching gradient being used to induce a first vibration (210) of one or more hardware elements of the magnetic resonance system (100) and / or the object (118), wherein the The set of waveform and pulse sequence commands (142, 152) is further configured for acquiring magnetic resonance data (144, 154) from the subject (118) according to a magnetic resonance protocol, wherein the acquiring of the magnetic resonance data (144, 154) includes sequentially generating at least two spin manipulation gradients (202, 204) for manipulating the phase of nuclear spins within the subject when the net magnetization vector of the subject (118) includes a non-zero component of the net magnetization in a transverse plane perpendicular to the longitudinal axis of the main magnetic field, and wherein execution of the machine executable instructions (140) causes the processor (130) to control the magnetic resonance system (100) using the set of waveform and pulse sequence commands (142, 152) to perform the following operations: - preparing a first vibration state (211) of the one or more hardware elements and / or the object (118), the preparation comprising generating the vibration matching gradient (200) causing the first vibration (210) of the one or more hardware elements and / or the object (118) when the net magnetization vector of the object (118) is aligned along the longitudinal axis of the main magnetic field, - acquiring the magnetic resonance data (144, 154) according to the magnetic resonance protocol, wherein the acquiring comprises sequentially generating the at least two spin manipulation gradients (202, 204) for manipulating the phase of nuclear spins in the object (118) when the net magnetization vector of the object (118) comprises a non-zero component along the transverse plane perpendicular to the longitudinal axis of the main magnetic field, wherein a first spin manipulation gradient (202) of the at least two spin manipulation gradients is generated during the first vibration state (211), and a second spin manipulation gradient (204) of the at least two spin manipulation gradients is generated during a second vibration state (213) of the one or more hardware elements and / or the object (118), the second vibration state resulting from a second vibration caused by the first spin manipulation gradient of the at least two spin manipulation gradients, wherein the vibration matching gradient (200) is used to match the second vibration state (213) to the first vibration state (211).

12. A method for operating a magnetic resonance system (100), the magnetic resonance system being configured to acquire magnetic resonance data from a subject (118) in a data acquisition volume (108) of the magnetic resonance system (100), the magnetic resonance system (100) comprising: a memory (134) storing machine-executable instructions (140) and a set of waveform and pulse sequence commands (142, 152), wherein the set of waveform and pulse sequence commands (142, 152) is configured to generate a vibration matching gradient (200) when a net magnetization vector of the object (118) is aligned along a longitudinal axis of a main magnetic field generated by the magnetic resonance system (100), the vibration matching gradient being used to induce a first vibration (210) of one or more hardware elements of the magnetic resonance system (100) and / or the object (118) 0), wherein the set of waveform and pulse sequence commands (142, 152) is further configured for acquiring magnetic resonance data (144, 154) from the subject (118) according to a magnetic resonance protocol, wherein the acquiring of the magnetic resonance data (144, 154) comprises sequentially generating at least two spin manipulation gradients (202, 204) for manipulating the phase of nuclear spins within the subject when the net magnetization vector of the subject (118) includes a non-zero component of the net magnetization in a transverse plane perpendicular to the longitudinal axis of the main magnetic field, and - a processor (130) for controlling the magnetic resonance system (100), wherein execution of the machine executable instructions (140) causes the processor (130) to control the magnetic resonance system (100) using the set of waveform and pulse sequence commands (142, 152) according to the method, wherein the method comprises: - preparing a first vibration state (211) of the one or more hardware elements and / or the object (118), the preparation comprising generating the vibration matching gradient (200) causing the first vibration (210) of the one or more hardware elements and / or the object (118) when the net magnetization vector of the object (118) is aligned along the longitudinal axis of the main magnetic field, - acquiring the magnetic resonance data (144, 154) according to the magnetic resonance protocol, wherein the acquiring comprises sequentially generating the at least two spin manipulation gradients (202, 204) for manipulating the phase of nuclear spins in the object (118) when the net magnetization vector of the object (118) comprises a non-zero component in the transverse plane perpendicular to the longitudinal axis of the main magnetic field, wherein a first spin manipulation gradient (202) of the at least two spin manipulation gradients is generated during the first vibration state (211), and a second spin manipulation gradient (204) of the at least two spin manipulation gradients is generated during a second vibration state (213) of the one or more hardware elements and / or the object (118), the second vibration state resulting from a second vibration caused by the first spin manipulation gradient of the at least two spin manipulation gradients, wherein the vibration matching gradient (200) is used to match the second vibration state (213) to the first vibration state (211).

Images