Mri apparatus

Abstract

An MRI system coil insert 2 for use within a bore B of a host MRI system 1, the coil insert 2 comprising at least one gradient coil for creating a spatially varying magnetic field along a respective axis and arranged to be electrically driven at ultrasound frequencies.

Description

TECHNICAL FIELD

[0001] The present invention relates to an MRI apparatus, in particular to an MRI system coil insert for use with an MRI system, to an MRI system apparatus comprising an MRI system with a coil insert or with other components, and to an echo planar spectroscopy imaging system comprising an MRI system apparatus and method for operating an MRI system. BACKGROUND

[0002] MRI (magnetic resonance imaging) systems are widely used for imaging of subjects and in the case of MRSI (magnetic resonance spectroscopic imaging) for acquiring spectral information. An MRI system typically comprises a magnet apparatus for creating a large static magnetic field B0, a set of radio frequency coils or antennas for generating an alternating magnetic field B1 and collecting magnetic resonance signals, in other words acquiring magnetic resonance data, and a set of gradient coils allowing spatial encoding on the B0 field to enable tomographic imaging. Furthermore, in the case of MRSI, the gradient coils are also used to allow spectral encoding.

[0003] Spatial encoding of the magnetic resonance signals is typically achieved by fast switching of three magnetic field gradients (X, Y, Z) created by gradient coils disposed around the scanner bore in which the subject to be examined will be disposed.

[0004] Typically, in existing systems, the gradient coils are driven in the range of 0-10 kHz. When driving the gradient coils in the audible range (20 Hz - 20 kHz), considerable efforts have been made to reduce the noise caused by the Lorentz forces when and by the switching of the gradients. Such methods include the use of materials to suppress the created noise.

[0005] To increase the spatio-temporal resolution of MRI, the gradient system can be driven "faster" and "stronger". In other words, with higher gradient slew rates (T per m per s) and higher gradient strengths (mT per m). At current gradients, the performance can be mainly limited by the uncomfortable peripheral nerve stimulation (PNS) caused by the switching of the strong magnetic field gradients too fast. The switching of the gradients induces electric fields and currents in conducting tissue, such as muscle and nerves, and can cause nerve depolarization and eventually nerve stimulation. SUMMARY

[0006] It would therefore be desirable to develop MRI apparatus and methods of operating MRI apparatus that can produce enhanced performance while not increasing the physical discomfort of the patient due to audible effects and / or peripheral nerve stimulation. Similarly, it would be desirable to produce MRI apparatus and methods of using MRI apparatus that can reduce audible effects and / or peripheral nerve stimulation and / or other causes of discomfort, whether or not there is an increase in performance of the MRI procedure itself. It would also be of interest if scans could be completed more quickly, to minimise the discomfort of the patient and / or to obtain results that are less affected by the time taken to acquire the scan.

[0007] According to a first aspect of the application there is provided an MRI system coil insert for use within a bore of a host MRI system, the coil insert comprising at least one gradient coil for creating a spatially varying magnetic field along a respective axis and arranged to be electrically driven at an ultrasound frequency.

[0008] This can allow an examination to be performed using the host MRI system in combination with the functionality of the insert. Using an ultrasound frequency has a number of advantages. Firstly, as the time over which the Lorentz forces act is shorter, this can result in less force being experienced by the coils themselves. This means that the coils can be lighter in weight compared to driving the coils at more conventional frequencies, and as a result the coils will be physically different and the structure supporting them will also be different. Secondly, the switching of the gradients is inaudible to the patient. Thirdly, it has been found that the peripheral nerve stimulation (PNS) of the patient being examined can be lower when using an ultrasound frequency, allegedly because the nerves do not have sufficient time to react to the switched fields.

[0009] The coil insert can have a central region in which there are no gradient coil windings. This can allow a window to be provided in the insert through which the patient can see when the patient's head is located within the insert. This can be facilitated by using lighter weight coils / using less force on the coils.

[0010] The insert can generally be cylindrical. The insert can have a main axis. The main axis can be arranged to be aligned with a main axis of a bore of a host MRI system with which the insert is used. In this case, the axes of the insert and the host MRI system can be aligned by being parallel to each other or coincident with each other.

[0011] The at least one gradient coil can comprise a Z gradient coil for creating a spatially varying magnetic field along the main axis of the insert. The at least one gradient coil can comprise an X gradient coil or a Y gradient coil for creating a spatially varying magnetic field transverse to the main axis of the insert.

[0012] The coil insert can comprise a first gradient coil for creating a spatially varying magnetic field along a respective first axis and a second gradient coil for creating a spatially varying magnetic field along a respective second axis.

[0013] The first gradient coil can be a Z-gradient coil for creating a spatially varying magnetic field along a main axis of the insert, and the second gradient coil can be an X-gradient coil or a Y-gradient coil for creating a spatially varying magnetic field transverse to the main axis of the insert.

[0014] In case the coil insert comprises a first gradient coil and a second gradient coil, the coil insert can still have a central region in which no gradient coil windings are present.

[0015] The coil insert can comprise a third gradient coil for creating a spatially varying magnetic field along a respective third axis, the third axis being transverse to the first and second axes. Typically, however, it is preferred to provide one or two gradient coils and not a third gradient coil, as this facilitates providing a central region in which no gradient coil windings are present.

[0016] The main MRI system will have its own gradient coils, and in operation these can be used in cooperation with the gradient coils of the insert. Thus, for example in case the insert lacks a gradient coil for creating a spatially varying magnetic field along a particular axis, the gradient coils of the main MRI system can be used to achieve spatial encoding in that axis.

[0017] The Z-gradient coil can comprise at least one set of windings.

[0018] The Z-gradient coil can comprise a first set of windings arranged at a first end of the insert and a second set of windings arranged at a second end of the insert. In one set of embodiments, a region between the first and second sets of windings can be free of Z-gradient coil windings.

[0019] It has been determined that although creating a central region free of windings can result in a smaller linear magnetic field, this can be tolerated in the present kind of insert. This is especially the case when the insert is used for examinations involving the head of a patient. Here, the insert does not necessarily have to have a large axial length.

[0020] In some cases, the Z-gradient coil can comprise more than two sets of windings. For example, four or more sets of windings can be provided.

[0021] The windings can be arranged to allow a segmented gradient to be provided along the Z-axis. In other words, rather than providing a continuous gradient, e.g. a linear gradient, along the Z-axis, a series of gradient portions are provided along the axis. This means that, overall, a smaller maximum absolute magnetic field can be used to establish a gradient along the Z-axis. This in turn can help to minimise peripheral nerve stimulation (PNS) of the patient being examined. This arrangement is more useful for longer inserts, i.e. where the Z-axis is long. Such an insert can be used to examine a larger area of a patient, it can be a whole body insert.

[0022] In other words, the windings can be arranged to allow a spatially non-monotonic gradient to be provided along the Z-axis.

[0023] The windings can be arranged to allow a spatially multi-lobed gradient to be provided along the Z-axis.

[0024] The windings can be arranged to allow a spatially oscillating gradient to be provided along the Z-axis.

[0025] The windings can be arranged to allow a spatially polynomial or sinusoidal varying gradient to be provided along the Z-axis.

[0026] It will be understood here that when we refer to these gradient patterns we mean the variation in magnitude / size of the magnetic field as seen along the Z-axis.

[0027] The windings of the Z gradient coil can be provided in two layers, wherein the turns in a first of the two layers are provided out of alignment with the turns in a second of the two layers. This can help to improve the spatial encoding that can be achieved.

[0028] A first set of windings of the Z gradient coil can be provided in two layers, wherein the turns in a first of the two layers are provided out of alignment with the turns in a second of the two layers. A second set of windings of the Z gradient coil can be provided in two layers, wherein the turns in a first of the two layers are provided out of alignment with the turns in a second of the two layers.

[0029] The X gradient coil or Y gradient coil can comprise at least one set of windings.

[0030] The X gradient coil or Y gradient coil can comprise a pair of windings provided on diametrically opposite sides of the insert. Each winding of the pair can comprise a plurality of helically wound turns, wherein each complete turn has an inner arc segment, a first end segment extending outwardly to an outer arc segment, and a second end segment extending inwardly from the outer arc segment to a corresponding inner arc segment of a subsequent turn. Each inner arc segment can follow a side wall of the insert. Each outer arc segment can follow a side wall of the insert.

[0031] In case a Z gradient coil is provided and the Z gradient coil comprises a first set of windings and a second set of windings as defined above, an X or Y gradient coil can be provided and axially placed in the insert between the first set of windings and the second set of windings of the Z gradient coil.

[0032] The X or Y gradient coil can comprise a third set of windings and a fourth set of windings, which are disposed on radially opposite sides of the insert and axially between the first set of windings and the second set of windings of the Z gradient coil. Thus, the third set of windings and the fourth set of windings can be disposed in regions where no windings of the Z gradient coil are present. It is noted here that the third set of windings and the fourth set of windings are the same windings as the pair of windings introduced above, which in this set of embodiments are a third set of windings and a fourth set of windings in the sense that they are defined with respect to the Z gradient coil.

[0033] A circumferential gap can be provided between the third set of windings and the fourth set of windings to provide a region in the insert where no windings of the Z gradient coil and no windings of the X or Y gradient coil are present. This region can be arranged as a window through which the patient can see when the patient's head is placed in the insert.

[0034] Each of the third set of windings and the fourth set of windings can comprise a plurality of helically wound turns, wherein each complete turn has an inner arc segment, a first end segment extending outwardly to an outer arc segment, and a second end segment extending inwardly from the outer arc segment to a corresponding inner arc segment of a subsequent turn.

[0035] Each inner arc segment can follow a side wall of the insert. Each outer arc segment can follow a side wall of the insert.

[0036] Such an arrangement can help to maximize an axial length of the insert over which the X or Y gradient coil is able to generate a linear magnetic field. It can also allow for a circumferential gap between the third set of windings and the fourth set of windings to be maximized, thereby allowing for a window to be created for the patient.

[0037] The insert can be provided with partial shielding coils for the at least one gradient coil, or even without shielding coils for the at least one gradient coil. In case the insert comprises a first gradient coil and a second gradient coil, the insert can be provided with partial shielding coils for the first gradient coil and the second gradient coil, or even without shielding coils for the first gradient coil and the second gradient coil.

[0038] The insert can comprise at least one capacitor electrically connected to the at least one gradient coil to cause the respective gradient coil to resonate at a predetermined ultrasound frequency. This helps efficiency in driving the gradient coil at the predetermined frequency. It can also mean that a lower current from a high impedance signal source can be used to drive the gradient coil and this can reduce inductive coupling with other coils / metallic objects in its region.

[0039] In the case where the insert comprises a first gradient coil and a second gradient coil, at least one first capacitor can be electrically connected to the first gradient coil to cause the first gradient coil to resonate at a first predetermined ultrasound frequency and at least one second capacitor can be electrically connected to the second gradient coil to cause the second gradient coil to resonate at a second predetermined ultrasound frequency.

[0040] The first predetermined ultrasound frequency can be the same as the second predetermined ultrasound frequency.

[0041] However, preferably the first predetermined ultrasound frequency is different to the second predetermined ultrasound frequency.

[0042] This helps to operate the two gradient coils at different frequencies which in turn can result in more spatial frequencies being sampled during imaging as this combination will generate a Lissajous encoding rather than a circular or spiral encoding. This in turn can increase the potential for accelerated imaging.

[0043] A potential problem has been identified by using two frequencies: audible sound can be generated. It has been identified that this is due to a "beat" being generated between the sounds created at the two frequencies.

[0044] Preferably the frequency difference between the first predetermined ultrasound frequency and the second predetermined ultrasound frequency is an inaudible frequency. That is, an infrasonic frequency or an ultrasonic frequency. Typically, in practice, the first predetermined ultrasound frequency and the second predetermined ultrasound frequency will be chosen such that the frequency difference between them is at an infrasonic frequency.

[0045] According to a further aspect of the application there is provided an MRI system coil insert apparatus comprising a coil insert as defined above and a signal generator apparatus for electrically driving the at least one gradient coil at an ultrasound frequency.

[0046] In the case where the at least one gradient coil comprises a Z gradient coil, the winding of the coil and the signal generator apparatus can be arranged to provide a segmented gradient in the Z axis.

[0047] The windings and the signal generator arrangement can be arranged to provide a spatially non-monotonic gradient along the Z-axis.

[0048] The windings and the signal generator arrangement can be arranged to provide a spatially multi-lobe gradient along the Z-axis.

[0049] The windings and the signal generator arrangement can be arranged to provide a spatially oscillating gradient along the Z-axis.

[0050] The windings and the signal generator arrangement can be arranged to provide a spatially polynomial or sinusoidal varying gradient along the Z-axis.

[0051] In the case that the insert comprises a first gradient coil and a second gradient coil, the signal generator arrangement can be arranged to drive the first gradient coil at a first selected ultrasound frequency and to drive the second gradient coil at a second selected ultrasound frequency. The first and second frequencies can be the same as each other. The first and second frequencies can be different from each other.

[0052] Preferably, the frequency difference between the first and second selected ultrasound frequencies is an inaudible frequency. That is, an infrasound or ultrasound frequency. Typically, in practice, the first and second selected ultrasound frequencies are selected such that the frequency difference between them is at an infrasound frequency.

[0053] The first selected frequency can be the same as the first predetermined frequency. The second selected frequency can be the same as the second predetermined frequency.

[0054] Thus, it should be noted that the first and second coils can be driven at selected frequencies whether or not capacitors are provided to cause the coils to resonate at those frequencies, although it is preferred that capacitors are provided and the coils are driven at their respective resonant frequencies.

[0055] According to a further aspect of the application, there is provided an MRI system arrangement comprising an MRI system having a main bore, and an MRI system coil insert as defined above for use within the bore.

[0056] According to a further aspect of the application, there is provided an MRI system arrangement comprising an MRI system having a main bore, and an MRI system coil insert arrangement as defined above having a coil insert arranged for use within the bore.

[0057] Although the above features have been introduced in the context of MRI system coil inserts, the features and ideas defined above may be used in the MRI system itself, where the context permits.

[0058] Therefore, according to another aspect of the invention, an MRI system including a coil device is provided, the coil device including at least one gradient coil for creating a spatially varying magnetic field along a corresponding axis and arranged to be electrically driven at an ultrasonic frequency.

[0059] Generally, where the context permits, the optional features described above are also optional features in this aspect of the invention. For the sake of brevity, all content will not be repeated here, but some content will be explicitly illustrated by way of examples.

[0060] The MRI system may include a signal generator device for electrically driving the at least one gradient coil at an ultrasonic frequency.

[0061] In one set of embodiments, the at least one gradient coil includes a Z-gradient coil, and the windings of the coil and the signal generator device are arranged to provide a segmented gradient on the Z-axis.

[0062] In other words, the winding and the signal generator device can be arranged to provide a spatially non-monotonic gradient along the Z-axis.

[0063] The winding and the signal generator device can be arranged to provide a spatially multi-lobed gradient along the Z-axis.

[0064] The winding and the signal generator device can be arranged to provide a spatially oscillating gradient along the Z-axis.

[0065] The winding and the signal generator device can be arranged to provide a gradient along the Z-axis that has a polynomial or sinusoidal variation in space.

[0066] The MRI system may include at least one capacitor electrically connected to the at least one gradient coil to cause the respective gradient coil to resonate at a predetermined ultrasound frequency.

[0067] The coil device may include a first gradient coil and a second gradient coil, wherein at least one first capacitor is electrically connected to the first gradient coil to cause the first gradient coil to resonate at a first predetermined ultrasonic frequency, and at least one second capacitor is electrically connected to the second gradient coil to cause the second gradient coil to resonate at a second predetermined ultrasonic frequency.

[0068] The first predetermined ultrasonic frequency can be the same as the second predetermined ultrasonic frequency.

[0069] However, preferably the first predetermined ultrasonic frequency is different from the second predetermined ultrasonic frequency.

[0070] Preferably, the frequency difference between the first predetermined ultrasonic frequency and the second predetermined ultrasonic frequency is an inaudible frequency. That is, an infrasonic or ultrasonic frequency. Typically, in practice, the first predetermined ultrasonic frequency and the second predetermined ultrasonic frequency will be chosen such that the frequency difference between them is at an infrasonic frequency.

[0071] In the case where the coil arrangement comprises a first gradient coil and a second gradient coil, the signal generator arrangement can be arranged to drive the first gradient coil at a first selected ultrasonic frequency and to drive the second gradient coil at a second selected ultrasonic frequency. The first frequency and the second frequency can be the same as each other. The first frequency and the second frequency can be different from each other.

[0072] Preferably, the frequency difference between the first selected ultrasonic frequency and the second selected ultrasonic frequency is an inaudible frequency. That is, an infrasonic or ultrasonic frequency. Typically, in practice, the first selected ultrasonic frequency and the second selected ultrasonic frequency will be chosen such that the frequency difference between them is at an infrasonic frequency.

[0073] The first selected frequency can be the same as the first predetermined frequency. The second selected frequency can be the same as the second predetermined frequency.

[0074] According to another aspect of the application, there is provided a method of operating an MRI system arrangement as defined above.

[0075] According to another aspect of the application, there is provided an echo planar spectroscopic imaging system comprising an MRI system arrangement having an acquisition section for acquiring magnetic resonance data and a reconstruction section for reconstructing images and spectroscopic information from the acquired magnetic resonance data,

[0076] The acquisition section comprises:

[0077] an RF transmit arrangement arranged to transmit single-band RF pulses or multi-band RF pulses;

[0078] a first gradient coil arranged to be driven at an ultrasonic frequency for creating a spatially varying magnetic field along a first respective axis; a second gradient coil arranged to be driven at an ultrasonic frequency for creating a spatially varying magnetic field along a second respective axis; and

[0079] signal generator means for electrically driving the first gradient coil at a first selected ultrasonic frequency and the second gradient coil at a second selected ultrasonic frequency,

[0080] wherein the signal generator means is configured to, as part of acquiring magnetic resonance data, apply a plurality of chirp pulses to the first gradient coil and a plurality of chirp pulses to the second gradient coil during a readout period, thereby achieving spectral encoding and spatial encoding in the first respective axis and the second respective axis; and

[0081] the acquisition section is arranged to read out magnetic resonance data during the readout period, and the reconstruction section is arranged to reconstruct an image and spectral information relating to the image from the magnetic resonance data read out during the readout period.

[0082] This can allow spatial encoding to be performed within the duration of each chirp pulse, and spectral encoding to be performed within the duration of the readout period. By using ultrasonic frequencies and a series of chirp pulses, MRSI data (i.e. MRI images and associated spectral data) can be obtained in relation to an examination period which is significantly shorter than examination periods achieved by the prior art. This can avoid loss or confusion of information over time, for example in relation to the flow of metabolites or chemical changes of metabolites within the subject during the examination period.

[0083] Each chirp pulse can have a length of less than 100 milliseconds, preferably less than 10 milliseconds. In one embodiment, each chirp pulse has a length of approximately 1 millisecond. In another embodiment, each chirp pulse has a length of approximately 0.5 milliseconds.

[0084] The signal generator means can be configured to apply at least 10 chirp pulses during the readout period, preferably at least 50 pulses. In one embodiment, 200 chirp pulses can be applied in the readout period.

[0085] Thus, it can be seen that the readout period can have approximately, for example, 100 milliseconds (e.g. 200 chirp pulses every 0.5 milliseconds), or 200 milliseconds (e.g. 200 chirp pulses every 1 millisecond). This in turn can result in a bandwidth of 2 kHz and 1 kHz, and a resolution of the spectral data of approximately 10 Hz and 5 Hz respectively.

[0086] The acquisition section can be arranged to acquire magnetic resonance data during a plurality of readout periods, to produce a set of magnetic resonance data.

[0087] The acquisition section can be arranged such that the RF transmit arrangement transmits a single-band RF pulse or a multi-band RF pulse prior to the start of each readout period, and the acquisition can be arranged to apply a respective plurality of chirp pulses to the first gradient coil and a respective plurality of chirp pulses to the second gradient coil during each readout period, thereby achieving spectral encoding and spatial encoding in the first respective axis and the second respective axis.

[0088] The reconstruction section can be arranged to reconstruct an image and spectral information relating to the image from the set of magnetic resonance data read out during the plurality of readout periods.

[0089] The first selected ultrasound frequency and the second selected ultrasound frequency can be the same frequency.

[0090] Preferably, the first selected ultrasound frequency is different from the second selected ultrasound frequency.

[0091] Preferably, the frequency difference between the first selected ultrasound frequency and the second selected ultrasound frequency is an inaudible frequency. That is, an infrasound frequency or an ultrasound frequency. Typically, in practice, the first selected ultrasound frequency and the second selected ultrasound frequency will be selected such that the frequency difference between them is in the infrasound frequency.

[0092] The acquisition section can comprise at least one first capacitor electrically connected with the first gradient coil to cause the first gradient coil to resonate at a first predetermined ultrasound frequency and at least one second capacitor electrically connected with the second gradient coil to cause the second gradient coil to resonate at a second predetermined ultrasound frequency.

[0093] The first predetermined ultrasound frequency can be the same as the second predetermined ultrasound frequency.

[0094] However, preferably, the first predetermined ultrasound frequency is different from the second predetermined ultrasound frequency.

[0095] Preferably, the frequency difference between the first predetermined ultrasound frequency and the second predetermined ultrasound frequency is an inaudible frequency. That is, an infrasound frequency or an ultrasound frequency. Typically, in practice, the first predetermined ultrasound frequency and the second predetermined ultrasound frequency are selected such that the frequency difference between them is in the infrasound frequency.

[0096] The first selected frequency can be the same as the first predetermined frequency. The second selected frequency can be the same as the second predetermined frequency.

[0097] The acquisition section can further comprise a third gradient coil arranged to be electrically driven for creating a spatially varying magnetic field along a third respective axis. The signal generator arrangement can be arranged for electrically driving the third gradient coil and in particular for providing spatial encoding on the third respective axis, thereby allowing selection of a slice of the subject under examination from which the above-mentioned magnetic resonance data or set of magnetic resonance data is to be acquired during the respective readout period or respective plurality of readout periods.

[0098] The acquisition section can be arranged to acquire further magnetic resonance data, or further sets of magnetic resonance data, in subsequent runs to facilitate an improvement in the signal-to-noise ratio of the acquired data.

[0099] The acquisition section can be arranged to acquire further magnetic resonance data, or further sets of magnetic resonance data, in subsequent runs by selecting different slices of the subject under examination using spatial encoding on the third respective axis.

[0100] The MRI system arrangement can comprise an MRI system having a main bore and an MRI system coil insert arrangement for use within the bore.

[0101] The insert can comprise the first gradient coil and the second gradient coil.

[0102] The insert can comprise a coil insert according to the first aspect of the application.

[0103] The third gradient coil can be a gradient coil of the MRI system itself. This can allow the gradient coil to be further from the patient, helping to keep any windows in the insert unobstructed.

[0104] Typically, the MRI system will also comprise respective gradient coils arranged for creating a spatially varying magnetic field along the first respective axis and for creating a spatially varying magnetic field along a second respective axis. However, in performing the acquisition of magnetic resonance data according to the above-mentioned further aspect of the application, in at least some cases these other respective gradient coils can not be used.

[0105] In other embodiments, there can be no insert and the first and second gradient coils of the above-mentioned further aspect of the application are provided in the main body of the MRI system.

[0106] In other embodiments, gradient coils can be used in the main MRI system and even in the insert on the same axis. Thus, for example, the Z gradient coils in the insert and in the main MRI system can both be used for encoding.

[0107] According to another aspect of the application, there is provided a method of echo planar spectroscopic imaging using an MRI system arrangement having an acquisition section for acquiring magnetic resonance data and a reconstruction section for reconstructing an image and spectral information from the acquired magnetic resonance data,

[0108] The method comprises:

[0109] applying a single-band or multi-band RF pulse to a subject under examination;

[0110] electrically driving an arranged first gradient coil at a first ultrasound frequency for creating a spatially varying magnetic field along a first respective axis and electrically driving a second gradient coil at a second ultrasound frequency for creating a spatially varying magnetic field along a second respective axis;

[0111] applying a plurality of chirp pulses to the first gradient coil and a plurality of chirp pulses to the second gradient coil during a readout period, thereby achieving spectral encoding and spatial encoding on the first respective axis and the second respective axis, respectively, as part of acquiring magnetic resonance data;

[0112] reading out magnetic resonance data during the readout period; and

[0113] reconstructing an image and spectral information related to the image from the magnetic resonance data read out during the readout period.

[0114] Note that all other features defined above after any aspect of the application, in general and after any necessary modifications in wording, can be used as further features of all other aspects of the application defined above. These other features will not be restated after each aspect of the application only for the sake of brevity. BRIEF DESCRIPTION OF DRAWINGS

[0115] Embodiments of the application will now be described, by way of example only, with reference to the accompanying drawings in which:

[0116] Figure 1 An MRI system arrangement is schematically shown;

[0117] Figure 2 An MRI system coil insert of the type that can be used in the MRI system arrangement shown and having a Z gradient coil is schematically shown; Figure 1 An MRI system coil insert of the type that can be used in the MRI system arrangement shown and having a Z gradient coil is schematically shown;

[0118] Figure 3 A part of an alternative MRI system coil insert is schematically shown, the part showing only the Z gradient coil and the X or Y gradient coil of the insert;

[0119] Figure 4A more detailed comparison with a portion of a conventional X or Y gradient coil is shown. Figure 3 The winding pattern of the X or Y gradient coil is shown in the figure;

[0120] Figure 5 This diagram illustrates a set of alternative windings for a Z-gradient coil used to create a segmented Z-axis gradient in an alternative MRI system coil insert; and

[0121] Figure 6 Examples are shown that can be used Figure 1 The timing diagram shows the echo-plane spectroscopy imaging technique performed by the type of MRI system device shown. Detailed Implementation

[0122] Figure 1 An MRI system apparatus is schematically illustrated, which in this case includes a main MRI system 1 and an MRI system coil insert 2. In this embodiment, the structure and operation of the main MRI system 1 are largely conventional. Therefore, although several aspects of the main MRI system are shown in the figures and will be discussed below, other aspects of the MRI system 1 are not shown or described in detail, but such details are, of course, well-known and understood in the field of MRI examination.

[0123] The MRI system insert 2 is arranged to be supplied and used in conjunction with existing MRI systems. This is certainly commercially advantageous because it means that existing MRI systems can be adapted to utilize the ideas of this invention, rather than requiring the development of an entirely new MRI system. That is, in an alternative, Figure 1 The MRI system device shown can be constructed from scratch, and in other alternatives, the features and functions of insert 2 can be incorporated into the body of MRI system 1 if desired.

[0124] exist Figure 1 For clarity, the MRI system coil insert 2 is shown externally to the main MRI system 1. However, during operation, the insert 2 will be moved to a position inside the main port B of the main MRI system 1. Figure 1 The position is shown by the dashed line. Figure 2 Schematic illustration Figure 1 The type of insert 2 shown is installed on the bed 3 of the MRI system 1, thereby... Figure 2 The position shown can be slidably moved between the position inside the aperture B of the MRI system 1. Figure 2 The position shown is the same as Figure 1 The position of the insert 2 shown corresponds to the position outside the hole B of the MRI system 1.

[0125] A variety of different types of inserts can be provided.

[0126] Figure 2 The insert 2' shown includes an insert Z gradient coil 2z, which includes a first set of windings 2z1 and a second set of windings 2z2, with a set of windings provided at each end of the insert 2.

[0127] The absence of a Z-coil winding in the central region between the first winding 2z1 and the second winding 2z2 results in a suboptimal field; however, it has been determined that these defects are tolerable in at least some cases. For example, these defects are tolerable because the space between the first windings 2z1 and 2z2 in an insert designed for examining a person's head is relatively small.

[0128] Figure 1 The insert 2 shown includes a similar insert Z-gradient coil 2z, which includes a first set of windings 2z1 and a second set of windings 2z2, and the insert 2 also includes an insert X-gradient coil 2x, which includes a first set of windings 2x1 and a second set of windings 2x2. Figure 3 The windings of these groups are shown more clearly in an isolated state.

[0129] exist Figure 1 and Figure 3 Insert 2 and Figure 2 In the insert 2', each Z-winding group 2z1, 2z2 itself comprises two sets of helically wound turns 2z1a, 2z1b, 2z2a, 2z2b. The second layer 2z1b, 2z2b is wound on top of the corresponding first layer 2z1a, 2z2a but slightly misaligned with the corresponding first layer 2z1a, 2z2a, so that the conductors in the outer group can provide a reverse current direction. It has been found that this improves the shielding of the gradient field to minimize eddy currents in the surrounding conductive material.

[0130] By combining Figure 3 consider Figure 4 You can see more clearly Figure 1 and Figure 3 The winding pattern of the X gradient coil 2x of the insert 2 is 2x1 and 2x2.

[0131] Figure 4 The inner layer of the X-gradient coil, which is wound in a more conventional manner, is shown. Figure 4Compared to the prior art, the X-insertion gradient coil 2x has multiple windings 2x1 and 2x2. Each winding 2x1 and 2x2 is spirally wound, and each complete turn includes inner arc segments 2x1a and 2x2a, which are connected to outer arc segments 2x1c and 2x2c via first end segments 2x1b and 2x2b. The turn is completed by second end segments 2x1d and 2x2d, which lead inward and backward to the beginning of the next turn. The next turn begins from the corresponding inner arc segments 2x1a and 2x2a of the subsequent turn, and so on.

[0132] It can be seen that the arc of each inner arc segment has the same radius as the arc of the other inner arc segments. Similarly, the arc of each outer arc segment has the same radius as the arc of the other outer arc segments. The radius of the arc of the inner segment is smaller than the radius of the arc of the outer segment.

[0133] This winding arrangement results in a longer linear region in the axial direction of the insert compared to prior art winding arrangements, and allows for a larger circumferential spacing between the ends of the two sets of windings (2x1, 2x2) compared to prior art line profiles. There are trade-offs in the properties of the field generated by this winding, but it has been found that the benefits outweigh these issues in this system.

[0134] Figure 1 and Figure 3 The insert 2 shown is designed for use during examination of a patient's head (especially the brain). Therefore, the insert 2 is arranged to position the patient's head within the aperture of the insert. The arrangement of the Z-gradient coil 2z and X-gradient coil 2x in the insert allows for the provision of a window W (schematically shown in the image) to be placed within the insert 2. Figure 3 And its position is schematically shown in Figure 1 (As indicated in the image), the user can see through this window when their head is inserted into insert 2. If needed, this window W can be an opening in the insert, or it can be an opening filled with transparent material.

[0135] In addition, Figure 2 In the type of insert 2' shown without the X-gradient coil, it will again be possible to create one or more windows W through which the user can see when their head is inside the insert 1. Of course, providing such a window helps patients avoid claustrophobia.

[0136] The MRI system device includes a signal generator device 4, which is configured to drive the gradient coils 2z and 2x of the insert 2.

[0137] In commerce, this signal generator device 4 can be provided with the insert 2, and this signal generator device 4 and insert 2 can together be considered as an MRI system coil insert device which can be used in an existing MRI system 1. Of course, again in other alternative embodiments, where a complete system is developed, there can be no need for a separate signal generator device, but it can be incorporated into the system provided within the main MRI system.

[0138] The signal generator device 4 is arranged for driving the gradient coils 2z, 2x in the insert 2 at ultrasound frequencies. That is, frequencies above the audible range.

[0139] In the case where there are two or more gradient coils in the insert 2, for example in an insert 2 of the type shown in Figure 1 and Figure 3 In some cases, the same ultrasound frequency can be used to drive each of the gradient coils 2z, 2x.

[0140] Alternatively and preferably, in the case where there are two gradient coils, for example the two gradient coils 2z, 2x in the insert 2, the signal generator device 4 is arranged for driving these two gradient coils at respective different ultrasound frequencies.

[0141] For example, in some embodiments a single ultrasound frequency can be used and set to 20.2 kHz. In other embodiments where two different frequencies are used, these frequencies may, for example, be one of 22 kHz and the other 19.9 kHz, one frequency being used to drive the X gradient coil 2x and one frequency being used to drive the Z gradient coil 2z. In practice, as will be appreciated, there is a great deal of freedom in which frequencies can be chosen.

[0142] However, it has been determined that it is particularly advantageous if the two different frequencies are first chosen, and then if the difference between these two different frequencies is itself an inaudible frequency. This is because, as stated in the introduction, a preferred spatial encoding can be achieved in the case where the two frequencies are different, and having a frequency difference in the inaudible range avoids the generation of an audible "beat" signal created between the sounds generated at the two selected inaudible frequencies. Typically, the two frequencies can be chosen such that the frequency difference is below the range of human hearing. In other words, the frequency difference is 20 Hz or less.

[0143] As Figure 1As is schematically illustrated, the signal generator means 4 are arranged to drive each of the gradient coils 2x, 2z in the insert via respective capacitors Cx, Cz. The values of these capacitors are chosen so that the respective gradient coils 2x, 2z resonate at the frequency to be driven by the signal generator means 4. This facilitates the use of high impedance signal generators and the delivery of lower currents to the gradient coils 2x, 2c, which in turn facilitates the reduction of coupling between them.

[0144] Note that the idea of having a gradient coil resonate at a predetermined frequency includes the case where the gradient coil is one electrical entity driven by one signal generator, and the gradient coil consists of a plurality of separate electrical entities that can be driven individually. Thus, in the case where there are a plurality of independent windings in the gradient coil, each winding will resonate by providing an appropriate capacitor.

[0145] In the present arrangement, no RF shielding is provided in the insert 2 or between the insert 2 and the main MRI system. This facilitates minimising the losses caused by the establishment of eddy currents that would otherwise occur when driving the insert gradient coils 2x, 2z at ultrasound frequencies. At the same time, the insert, and in particular the gradient coils 2x, 2z, is relatively transparent to the signals to be transmitted and received by the main MRI system. Thus, the operation of the main MRI system can continue with the insert 2 in place in the bore B of the main MRI system.

[0146] In general, minimising the amount of electrically conductive material in the vicinity of the insert gradient coils 2x, 2z (or any gradient coil operated at ultrasound frequencies) facilitates improved efficiency by minimising the effects of eddy currents. This problem is mitigated as the distance between the gradient coil driven at ultrasound frequencies and metal objects increases. Thus, in the present arrangement, the fact that the active gradient field shielding is sub-optimal or even non-existent for the main MRI system, and that there are other metal objects in the main MRI system, can be tolerated. This desire to minimise metal in the vicinity of ultrasound driven gradient coils i) makes it less obvious that it is feasible to use such frequencies, and ii) makes it more convenient to include them in the insert rather than the main MRI machine in at least some cases.

[0147] Figure 5 An alternative form of Z gradient coil is schematically illustrated, which can be provided in an alternative form of insert. Similarly, again, in the alternative, this form of Z gradient coil can be provided in the main body of a newly constructed MRI machine 1.

[0148] Here, the Z gradient coil comprises four sets of windings 2z1-2z4, each set of windings having the same configuration as the multiple sets of Z windings 2z1, 2z2 described above. Again, these windings are arranged to be driven by the signal generator means 4, and are arranged to resonate at a selected drive frequency by including one or more capacitors (not shown).

[0149] In this case, rather than establishing a monotonically varying Z gradient field in the insert by the Z gradient coil as in the conventional case, in the insert described above with respect to Figure 1 to Figure 4 the Z gradient is created in segments. That is, Figure 5 the insert of is arranged to create a more complex varying Z gradient field, rather than a monotonically varying Z gradient field. In particular, this can be established as multi-lobed, and have a polynomial or sinusoidal spatial variation along the Z axis, for example. This in turn means that the maximum magnitude of the difference in gradient field from one end of the axis to the other can be controlled, whilst still providing sufficient gradient variation per unit length along the insert. It has been determined that it can be advantageous to provide a segmented Z gradient field, particularly in the case where a longer insert is to be used (i.e. an insert for examining a larger area than the bore), for example in the case where the insert is to be used for whole body examination or the gradient windings are incorporated into a whole body MRI machine. Furthermore, it has been determined that the SENSE (Sensitivity Encoding) reconstruction technique, which is well known in MRI technology, can be successfully deployed on the information obtained when using a segmented Z gradient of the type produced by the insert shown in Figure 5 addition, it has been determined that the use of such a segmented Z gradient can reduce the onset of PNS in the subject being examined, or alternatively allow a stronger Z gradient to be used before the onset of PNS is obtained.

[0150] Having briefly introduced the main MRI system 1, the operation of the MRI system apparatus will now be described.

[0151] In general, the main MRI system 1 comprises an acquisition section I for acquiring magnetic resonance data, and a reconstruction section R for reconstructing images and spectral information relating to those images from the acquired magnetic resonance data. In Figure 1 the apparatus shown, the insert 2 and the signal generator means 4 form part of the acquisition section I. That is, they cooperate with the elements of the acquisition section I of the main MRI machine to acquire the magnetic resonance data, which can then be reconstructed by the reconstruction section R.

[0152] In general, the elements of the acquisition section I in the main MRI machine 1 comprise a magnet, a coil arrangement 5 and a control system 6. The control system 6 has an output section 61 for controlling the operation of the magnet and coil arrangement 5 and a receiver section 62 for receiving back information from the magnet and coil arrangement 5. In the present arrangement, which uses a coil insert 2, the output section 61 also issues control signals to the signal generator arrangement 4 and, in some embodiments, the receiver section 62 can also receive outputs from the insert 2, although this is optional. In the arrangement now described, the reception of the magnetic resonance data is performed in the main MRI machine 1 itself.

[0153] As mentioned above in the alternatives, the components of the insert 2 and signal generator arrangement can be incorporated into the MRI machine itself.

[0154] It will be appreciated that the MRI machine will generally comprise one or more "computers" for controlling the operation and processing the received data. Each such computer can comprise a processor, a memory and at least one data storage device. The control system 6 can be computer-implemented. The reconstruction section R can be computer-implemented.

[0155] The magnet and coil arrangement 5 comprises a main magnet 51 for creating a static field, X, Y and Z gradient coils 52, a radio frequency transmit coil 53 and a radio frequency receive coil 54.

[0156] In operation, the output section 61 passes drive currents to the gradient coils 52 and causes appropriate radio frequency transmit pulses to be output by the transmit coil 53, while the receiver section 62 receives inputs from the receive coil 54.

[0157] In the present embodiment, the output section 61 also provides control trigger signals to the signal generator arrangement 4 to allow it to appropriately time the generation of the gradient drive signals for driving the insert gradient coils 2x, 2z.

[0158] In principle, any combination of the gradient coils 52 of the main MRI system 1 and the gradient coils 2x, 2z of the insert 2 can be used to give the desired encoding effect.

[0159] Most typically, these coils can be used in combination with the Y gradient coil 52y of the main MRI machine 1, possibly in the case that the insert 2 comprises an X gradient coil 2x and a Z gradient coil 2z.

[0160] Thus, in a particular embodiment, the gradient coil 52y of the main MRI machine 1 can be used for spatial encoding to select a particular slice of the subject for examination and the Z gradient coil 2z and X gradient coil 2x in the insert 2 can be used for spatial encoding within that slice.

[0161] In the case where the insert only comprises Z gradient coils (for example, in the case of the insert shown in Figure 2 The X gradient coils 52x and Y gradient coils 52y in the main MRI machine 1 can be used in conjunction with the Z gradient coils 2z in the insert 2.

[0162] In other cases, two gradient coils in one specific axis in the main MRI machine 1 and the insert 2 can be used together.

[0163] For example, in the case where the X gradient coils 52x, Y gradient coils 52y and Z gradient coils 52z from the MRI machine 1 are used in conjunction with the Z gradient coils 2z of the insert, the insert shown in Figure 2 may be used. This can provide different options for spatial encoding.

[0164] In the above cases, the gradient coils 52 in the main MRI machine 1 will be driven at a conventional frequency, while the gradient coils in the insert 2 will be driven at an ultrasound frequency.

[0165] Figure 6 A timing diagram is shown for echo planar spectroscopic imaging (EPSI) techniques, which can be performed using MRI system apparatus of the type described above. In particular, when used with an insert of the type described above in relation to Figure 1 and Figure 3 The MRI system apparatus of Figure 1 may be used as an echo planar spectroscopic imaging system, and operated in accordance with the timing diagram shown in Figure 6

[0166] In this technique, the Z gradient coils 2z of the insert 2 are used with the X gradient coils 2x of the insert and the Y gradient coils 52y of the main MRI machine 1. The timing Figure 6 of the signals applied to these gradient coils when performing the technique of Figure 6 is shown schematically. It will be understood that "Gz insert" refers to the signal applied to the Z gradient coils 2z of the insert, "Gx insert" refers to the signal applied to the X gradient coils 2x and "Gy main" refers to the signal applied to the Y gradient coils 52y of the main MRI machine.

[0167] Furthermore, in the timing diagram RF, it is indicated that the signal applied using the transmit coils 53 of the main MRI machine 1.

[0168] ​At the start of each repetition period (TR), a multi-band pulse is applied by the RF transmit coil 53, and a slice selection pulse is applied to the Y gradient coil 52y of the MRI machine 1. Then, in a subsequent readout period, a respective plurality of chirp pulses is applied to the Z gradient coil 2z of the insert 2 on the one hand, and to the X gradient coil 2x of the insert 2 on the other hand. In the present embodiment, each chirp pulse has a length of 500 microseconds, and in the readout period, a total of 200 such chirp pulses are applied to each of the Z gradient coil 2z and the X gradient coil 2x.

[0169] In the present embodiment, each chirp pulse has the same waveform as each of the other chirp pulses, and the chirp pulses on the Z gradient coil 2z and the X gradient coil 2x are applied in phase with each other. However, other possibilities are also available.

[0170] The purpose of applying the chirp pulses is to capture a large K-space (the magnitude of each axis defines the spatial resolution on that axis) as well as the distance between K-space points / circles (the decay magnitude defines the field of view).

[0171] With this technique, all spatial encoding can be defined in each chirp pulse, while spectral information is encoded over the chirp pulse group, i.e. in this embodiment, over the 200 chirp pulses. The number of chirp pulses and their length as well as the total length of the chirp pulses will determine the spectral bandwidth and resolution. Thus, in the present embodiment, with a length of 500 microseconds for each chirp pulse, the bandwidth will be 2 kHz, and with a total length of the chirp pulses of 100 milliseconds, this will result in a resolution of approximately 10 Hz (not including relaxation effects and other small order effects).

[0172] In another embodiment, the length of each chirp pulse can be one millisecond. In this case, if again 200 chirp pulses are applied, this will result in a bandwidth of 1 kHz and a resolution of approximately 5 Hz, as opposed to approximately 10 Hz in the above embodiment.

[0173] Each chirp pulse comprises a finite time-varying amplitude application of an ultrasound frequency at which the respective insert gradient coil 2z, 2x is arranged to operate. In this embodiment, the two ultrasound frequencies are identical, although in other cases they can be different, resulting in the other benefits mentioned above.

[0174] In the present embodiment, four shots are used to improve the accuracy of the results, as indicated in the timing diagram. The second multi-band pulse in MB2 is set to the start of the second shot and an appropriate slice selection signal is applied to the Y gradient coil 52y of the main MRI machine 1. Thereafter, during the readout period of this second shot, a second chirp pulse sequence is applied to the Z gradient coil 2z and the X gradient coil 2x of the insert 2. The whole procedure is repeated again in the third and fourth shots so that the acquired magnetic resonance data can be fed to the reconstruction R for reconstructing the image and the spectral data related to the image. The reconstruction system R can be arranged under software for performing SENSE (sensitivity encoding) reconstruction.

[0175] If desired, in order to obtain more data, further runs as described above can be performed to improve the signal-to-noise ratio.

[0176] Alternatively or additionally, further runs can be performed for different "Y slices" of the subject. That is, a different set of offset frequencies for slice selection can be applied to the RF coil 54 of the MRI machine 1, thereby selecting a second batch of slices for examination etc.

[0177] It will be noted that with this technique, the spatial encoding is performed in each chirp pulse, and for the complete spatial encoding and spectral encoding of a set of slices, this can be performed in about 100 milliseconds in total, using only one shot, or in about 400 milliseconds in total, using four shots as in the embodiment shown. Figure 6

[0178] This means that the image data and spectral data collected in a very short period of time can be considered. This can help to avoid information loss or results confusion that can occur in conventional techniques, which require much longer encoding times. In more traditional echo planar spectroscopic imaging techniques, the data is encoded on the region of interest one voxel at a time, with the spatial encoding being performed to effectively select a specific voxel, and then the spectral sampling is performed for that voxel before moving to the next voxel. This results in a much longer examination period of about a few seconds.​

Claims

1. An MRI system coil insert for use within a bore of a main MRI system, the coil insert comprising at least one gradient coil for creating a spatially varying magnetic field along a respective axis and arranged to be electrically driven at an ultrasonic frequency, wherein the insert comprises at least one capacitor electrically connected to the at least one gradient coil to cause the respective gradient coil to resonate at a predetermined frequency, wherein the insert comprises a first gradient coil and a second gradient coil, at least one first capacitor and at least one second capacitor, the at least one first capacitor being electrically connected to the first gradient coil to cause the first gradient coil to resonate at a first predetermined ultrasonic frequency, and the at least one second capacitor being electrically connected to the second gradient coil to cause the second gradient coil to resonate at a second predetermined ultrasonic frequency, wherein the first predetermined ultrasonic frequency is different from the second predetermined ultrasonic frequency.

2. The MRI system coil insert according to claim 1, having a central region without gradient coil windings.

3. The MRI system coil insert according to claim 2, wherein the insert has a window through which the patient can see when the patient's head is inside the insert.

4. The MRI system coil insert according to any one of claims 1-3, the MRI system coil insert comprising a Z-gradient coil for creating a spatially varying magnetic field along the main axis of the insert.

5. The MRI system coil insert according to claim 4, wherein the Z-gradient coil includes a first set of windings disposed at a first end of the insert and a second set of windings disposed at a second end of the insert.

6. The MRI system coil insert of claim 4, wherein the Z-gradient coil comprises more than two sets of windings arranged to allow segmented gradients to be provided on the Z-axis.

7. The MRI system coil insert according to any one of claims 1-3, the MRI system coil insert comprising an X-gradient coil or a Y-gradient coil for creating a spatially varying magnetic field transverse to the principal axis of the insert.

8. The MRI system coil insert of claim 5 further includes an X-gradient coil or a Y-gradient coil for creating a spatially varying magnetic field transverse to the main axis, wherein the X-gradient coil or Y-gradient coil includes a third set of windings and a fourth set of windings, the third set of windings and the fourth set of windings being disposed on radially opposite sides of the insert and axially located between the first set of windings and the second set of windings of the Z-gradient coil.

9. The MRI system coil insert of claim 8, wherein a circumferential spacing is provided between the third group of windings and the fourth group of windings, such that there is a region in the insert where neither the winding of the Z-gradient coil nor the winding of the X-gradient coil or the Y-gradient coil exists.

10. The MRI system coil insert according to claim 8 or 9, wherein each of the third winding and the fourth winding comprises a plurality of helically wound coils, wherein each complete coil has an inner arcuate segment, a first end segment and a second end segment, the first end segment extending outward to an outer arcuate segment and the second end segment extending inward from the outer arcuate segment to a corresponding inner arcuate segment of a subsequent coil.

11. The MRI system coil insert of claim 1, wherein the frequency difference between the first predetermined ultrasonic frequency and the second predetermined ultrasonic frequency is an inaudible frequency.

12. An MRI system coil insert device comprising a coil insert according to any one of claims 1-11 and a signal generator device for electrically driving the at least one gradient coil at an ultrasonic frequency.

13. The MRI system coil insert device of claim 12, wherein the insert comprises a first gradient coil and a second gradient coil, and the signal generator device is arranged to drive the first gradient coil at a first selected ultrasonic frequency and drive the second gradient coil at a second selected ultrasonic frequency.

14. The MRI system coil insert device of claim 13, wherein the frequency difference between the first selected ultrasound frequency and the second selected ultrasound frequency is an inaudible frequency.

15. The MRI system coil insert device of claim 13, wherein the first selected frequency is the same as the first predetermined frequency, and the second selected frequency is the same as the second predetermined frequency.

16. The MRI system coil insert device of claim 12, wherein the MRI system coil insert device comprises the coil insert of claim 6, and the windings of the coil and the signal generator device are arranged to provide a segmented gradient on the Z-axis.

17. An MRI system apparatus comprising an MRI system having a main port and an MRI system coil insert according to any one of claims 1 to 11, the MRI system coil insert being used within the main port.

18. An MRI system apparatus comprising an MRI system having a main aperture, and an MRI system coil insert apparatus according to any one of claims 12 to 16, wherein the coil insert is arranged for use within the aperture.

19. An echo-planar spectral imaging system, comprising an MRI system apparatus according to claim 17 or claim 18, the MRI system apparatus having an acquisition unit for acquiring magnetic resonance data and a reconstruction unit for reconstructing image and spectral information from the acquired magnetic resonance data. The acquisition unit includes: RF transmitting devices are configured to output single-band RF pulses or multi-band RF pulses; The first gradient coil of the MRI system coil insert is arranged to be driven at an ultrasonic frequency to create a spatially varying magnetic field along a first corresponding axis. Furthermore, the second gradient coil of the MRI system coil insert is arranged to be driven at an ultrasonic frequency to create a spatially varying magnetic field along a second corresponding axis. as well as A signal generator device for electrically driving the first gradient coil at a first selected ultrasonic frequency and driving the second gradient coil at a second selected ultrasonic frequency. The signal generator device is configured to apply multiple linear frequency modulated pulses to the first gradient coil and multiple linear frequency modulated pulses to the second gradient coil during the readout period as part of acquiring the magnetic resonance data, thereby achieving spectral encoding and spatial encoding on the first and second corresponding axes. as well as The acquisition unit is arranged to read out magnetic resonance data during the readout period, and the reconstruction unit is arranged to reconstruct an image and spectral information related to the image from the magnetic resonance data read out during the readout period.

20. The echo plane spectrum imaging system of claim 19, wherein each linear frequency modulated pulse has a length of less than 10 milliseconds.

21. The echo plane spectrum imaging system of claim 19 or claim 20, wherein the signal generator device is configured to apply at least 10 linear frequency modulated pulses during the readout period.

22. The echo plane spectral imaging system according to claim 19 or claim 20, wherein the acquisition unit is arranged to acquire magnetic resonance data during multiple readout periods to generate a set of magnetic resonance data, and the acquisition unit is arranged to cause the RF transmitting device to output a single-band RF pulse or a multi-band RF pulse before the start of each readout period, and the acquisition unit is arranged to apply a corresponding plurality of linear frequency modulated pulses to the first gradient coil and to apply a corresponding plurality of linear frequency modulated pulses to the second gradient coil during each readout period to achieve spectral coding and spatial coding on the first corresponding axis and the second corresponding axis.

23. The echo plane spectrum imaging system according to claim 19 or claim 20, wherein the first selected ultrasonic frequency is different from the second selected ultrasonic frequency.

24. The echo plane spectrum imaging system of claim 23, wherein the frequency difference between the first selected ultrasonic frequency and the second selected ultrasonic frequency is an inaudible frequency.

25. The echo plane spectrum imaging system of claim 19, wherein the first selected frequency is the same as the first predetermined frequency, and the second selected frequency is the same as the second predetermined frequency.

26. The echo plane spectral imaging system of claim 19 or 20, wherein the acquisition unit further comprises a third gradient coil arranged to be electrically driven to create a spatially varying magnetic field along a third corresponding axis, and the signal generator device is arranged to electrically drive the third gradient coil to provide spatial encoding on the third corresponding axis, thereby allowing selection of a slice of the object being examined from which the magnetic resonance data or the set of magnetic resonance data is acquired during a corresponding readout period or a plurality of corresponding readout periods.

27. A method for echo-plane spectral imaging using an MRI system apparatus according to claim 17 or claim 18, the MRI system apparatus having an acquisition unit for acquiring magnetic resonance data and a reconstruction unit for reconstructing image and spectral information from the acquired magnetic resonance data. The method includes: Apply a single-band or multi-band RF pulse to the object being inspected; The first gradient coil is electrically driven at a first ultrasonic frequency to create a spatially varying magnetic field along a first corresponding axis, and the second gradient coil is electrically driven at a second ultrasonic frequency to create a spatially varying magnetic field along a second corresponding axis. As part of acquiring magnetic resonance data, multiple linear frequency modulated pulses are applied to the first gradient coil and multiple linear frequency modulated pulses are applied to the second gradient coil during the readout period, thereby achieving spectral encoding and spatial encoding on the first corresponding axis and the second corresponding axis; During the readout period, magnetic resonance data is read out; as well as The image and spectral information associated with the image are reconstructed from the magnetic resonance data read out during the readout period.

Images