Magnetic Resonance Imaging System

Abstract

To collect an MR signal while keeping image quality when another magnetic resonance imaging apparatus is installed in the vicinity.SOLUTION: A magnetic resonance imaging apparatus is installed in the vicinity of at least another one magnetic resonance imaging apparatus, and includes a collection unit, a determination unit, and a re-collection unit. The collection unit collects an MR signal generated from a subject in response to an RF pulse applied to the subject. The determination unit determines whether or not an external RF pulse of another magnetic resonance imaging apparatus affects the MR signal being collected. When the MR signal is determined to be affected in the determination, the re-collection unit nullifies the MR signal being collected and recollects the MR signal that has been nullified.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The embodiments disclosed in the present specification and drawings relate to a magnetic resonance imaging apparatus. [Background Art]

[0002] A magnetic resonance imaging apparatus is an imaging apparatus that excites nuclear spins of a subject placed in a static magnetic field with a radio frequency (RF) signal of Larmor frequency, reconstructs magnetic resonance signals (MR (Magnetic Resonance) signals) generated from the subject along with the excitation, and generates an image therefrom.

[0003] Generally, a magnetic resonance imaging apparatus is installed with radio wave and magnetic field shielding applied. The radio wave shield can prevent the intrusion of external electromagnetic waves in frequency bands that cause image noise, and can suppress the influence of radio waves from an RF generator or the like on the operation of peripheral devices. In addition, the magnetic field shield can prevent the intrusion of magnetic fields from moving large magnetic bodies such as elevators and magnetic field fluctuation sources such as electrical rooms, which can be factors that impair magnetic field uniformity, and can suppress the influence of leakage magnetic fields on the operation of peripheral devices.

[0004] However, depending on the installation facility such as a hospital, two or more magnetic resonance imaging apparatuses are installed in close proximity, and the effects of radio wave and magnetic field shielding are not sufficient, so the quality of the reconstructed image of MR signals may not be maintained. In particular, when adjacent magnetic resonance imaging apparatuses have the same static magnetic field strength, their magnetic resonance frequencies are almost the same. For example, when RF pulses for excitation of one apparatus are mixed in during the MR signal data acquisition of another apparatus, artifacts may occur. In addition, if external electromagnetic waves as interfering signals other than the MR signal generated from the human body are received during MR signal data acquisition, noise will be mixed into the reconstructed image, which may impair image quality. [Prior Art Documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2015-136496 [Overview of the project] [Problems that the invention aims to solve]

[0006] One of the problems that the embodiments disclosed herein and in the drawings aim to solve is to acquire MR signals while maintaining image quality when other magnetic resonance imaging (MR) devices are installed in close proximity. However, the problems that the embodiments disclosed herein and in the drawings aim to solve are not limited to the above problem. Problems corresponding to the effects of each configuration shown in the embodiments described later can also be positioned as other problems. [Means for solving the problem]

[0007] A magnetic resonance imaging apparatus according to one embodiment is installed in close proximity to at least one other magnetic resonance imaging apparatus and comprises an acquisition unit, a determination unit, and a reacquisition unit. The acquisition unit collects MR signals generated from a subject in response to an RF pulse applied to the subject. The determination unit determines whether or not external RF pulses from the other magnetic resonance imaging apparatus may affect the MR signal being acquired. If the determination determines that the MR signal may be affected, the reacquisition unit invalidates the MR signal being acquired and reacquisitions the invalidated MR signal. [Brief explanation of the drawing]

[0008] [Figure 1] A schematic diagram showing an example of the overall configuration of a magnetic resonance imaging apparatus according to the first embodiment. [Figure 2] A diagram illustrating the effects of installing two or more magnetic resonance imaging (MRI) systems in close proximity. [Figure 3] A diagram illustrating the relationship between a magnetic resonance imaging apparatus according to the first embodiment and other magnetic resonance imaging apparatuses. [Figure 4] A flowchart showing an example of the operation of data acquisition of an MR signal according to the first embodiment. [Figure 5] A diagram illustrating the influence of external RF pulses on data acquisition of an MR signal according to the first embodiment. [Figure 6] A diagram illustrating an example of a method for acquiring K-space data of an MR signal according to the first embodiment. [Figure 7] A flowchart showing an example of data acquisition operation for an MR signal according to a first modification of the first embodiment. [Figure 8] A schematic diagram showing an example of the overall configuration of a magnetic resonance imaging apparatus according to a second modification of the first embodiment. [Figure 9] A diagram illustrating the influence of external RF pulses on MR signal data acquisition according to a third modification of the first embodiment. [Figure 10] This figure illustrates an example of a method for acquiring K-space data of an MR signal according to a third modification of the first embodiment. [Figure 11] A diagram illustrating the relationship between a magnetic resonance imaging apparatus according to the second embodiment and other magnetic resonance imaging apparatuses. [Figure 12] A diagram illustrating the relationship between a magnetic resonance imaging apparatus according to the third embodiment and other magnetic resonance imaging apparatuses. [Figure 13] A flowchart showing an example of data acquisition operation for MR signals according to the third embodiment. [Figure 14] A diagram illustrating the influence of interfering signals on data acquisition of MR signals according to the third embodiment. [Modes for carrying out the invention]

[0009] The following describes in detail an embodiment of the magnetic resonance imaging apparatus with reference to the drawings.

[0010] (Overall configuration of a magnetic resonance imaging system) Figure 1 is a schematic diagram showing an example of the overall configuration of a magnetic resonance imaging apparatus (MRI) 1 according to an embodiment. The magnetic resonance imaging apparatus 1 comprises a magnet stand 100, a control cabinet 300, an image processing device (e.g., a console) 400, and a patient bed 500.

[0011] The magnet stand 100 and the examination bed 500 are placed, for example, in a shielded room called an examination room. Meanwhile, the control cabinet 300 is placed, for example, in a machine room, and the console 400 is placed, for example, in an operation room.

[0012] Figure 1 shows a cylindrical magnetic resonance imaging apparatus in which the static magnetic field magnet 10, gradient magnetic field coil 11, and WB (Whole Body) coil 12 are generally cylindrical in shape. However, the magnetic resonance imaging apparatus 1 according to this embodiment may be a parallel plate type magnetic resonance imaging apparatus. In a parallel plate type magnetic resonance imaging apparatus, for example, the magnet base is a flat circular shape, and the subject P is imaged in an open space sandwiched between two parallel flat plate-shaped static magnetic field magnets. The parallel plate type magnetic resonance imaging apparatus has the same configuration as a cylindrical magnetic resonance imaging apparatus in which the static magnetic field magnet, gradient magnetic field coil, and WB coil constituting the magnet base are generally cylindrical, except that they are parallel plate shapes.

[0013] The magnet gantry 100 includes a static magnetic field magnet 10, a gradient magnetic field coil 11, and a WB coil 12, and these components are housed in a cylindrical casing. The bed 500 includes a bed main body 50 and a bed top plate 51. The magnetic resonance imaging apparatus 1 also includes an RF coil 20 disposed in proximity to a subject P. In the following description, it is explained that the RF coil 20 is one of the components of the magnetic resonance imaging apparatus 1, but the RF coil 20 may not be included in the configuration of the magnetic resonance imaging apparatus 1 in some cases. In this case, although the RF coil 20 is not included in the configuration of the magnetic resonance imaging apparatus 1, the RF coil 20 and the magnetic resonance imaging apparatus 1 are configured to be connectable to each other. More specifically, the RF coil 20 and the bed top plate 51 of the magnetic resonance imaging apparatus 1 are configured to be connectable to each other.

[0014] A control cabinet 300 includes a gradient magnetic field power supply 31 (31x for X-axis, 31y for Y-axis, 31z for Z-axis), an RF receiver 32, an RF transmitter 33, and a sequence controller 34.

[0015] The static magnetic field magnet 10 of the magnet gantry 10 has a substantially cylindrical shape, and generates a static magnetic field in a bore that is an imaging region for the subject P (the space inside the cylinder of the static magnetic field magnet 10). The static magnetic field magnet 10 incorporates a superconducting coil, and the superconducting coil is cooled to an extremely low temperature by liquid helium. The static magnetic field magnet 10 generates a static magnetic field by applying a current supplied from a static magnetic field power supply (not shown) to the superconducting coil in an excitation mode, and then after shifting to a persistent current mode, the static magnetic field power supply is disconnected. Once shifted to the persistent current mode, the static magnetic field magnet 10 continues to generate a large static magnetic field for a long time, for example, one year or more. Note that the static magnetic field magnet 10 may alternatively be configured as a permanent magnet. The static magnetic field magnet 10 may also be configured in a parallel plate shape.

[0016] The gradient magnetic field coil 11 is also roughly cylindrical in shape and is fixed inside the static magnetic field magnet 10. This gradient magnetic field coil 11 consists of three gradient magnetic field coils for the X axis, Y axis, and Z axis. Each gradient magnetic field coil is supplied with gradient magnetic field current from a gradient magnetic field power source (31x, 31y, 31z), generating gradient magnetic fields in the X, Y, and Z axes, which are applied to the subject P. If the static magnetic field magnet 10 is configured as a parallel plate shape, the gradient magnetic field coil 11 is configured with a similar shape.

[0017] The bed body 50 of the bed 500 has a bed top plate 51 that can be moved vertically and horizontally. Before imaging, the subject P, who is placed on the bed top plate 51, is moved to a predetermined height. Then, during imaging, the bed top plate 51 is moved horizontally to move the subject P into the bore.

[0018] The WB coil 12 is fixed in a roughly cylindrical shape inside the gradient magnetic field coil 11, surrounding the subject P. The WB coil 12 transmits RF pulses transmitted from the RF transmitter 33 toward the subject P, while also receiving magnetic resonance signals (i.e., MR signals) emitted from the subject P due to the excitation of hydrogen nuclei. If the static magnetic field magnet 10 is configured as a parallel plate shape, the WB coil 12 is configured in a similar shape.

[0019] The RF coil 20 receives the MR signal emitted from the subject P at a position close to the subject P. Depending on the imaging area of ​​the subject P, there are various types of RF coils 20, such as those for the head, chest, spine, lower limbs, or whole body. Figure 1 shows an example of a chest RF coil 20 being mounted. The WB coil 12 and RF coil 20 are examples of coils that receive MR signals.

[0020] The RF transmitter 33 transmits an RF pulse to the WB coil 12 based on instructions from the sequence controller 34. The RF receiver 32 detects the MR signal received by the WB coil 12 or the RF coil 20 and sends the data obtained by digitizing the detected MR signal (i.e., raw data) to the sequence controller 34.

[0021] The sequence controller 34 performs a scan of the subject P by driving the gradient power supply 31, RF transmitter 33, and RF receiver 32, respectively, under the control of the console 400. After the sequence controller 34 has performed the scan and received data from the RF receiver 32, it sends that data to the console 400.

[0022] Furthermore, the sequence controller 34 can perform processing to exclude data that may impair the quality of the MR image during MR signal data acquisition, in order to acquire data while maintaining image quality. Note that some or all of this processing may be performed on the console 400. The sequence controller 34 includes a processing circuit 340 and a storage circuit 350.

[0023] The processing circuit 340 is, for example, a circuit equipped with a CPU or a dedicated or general-purpose processor. The processor realizes various functions described later by executing various programs stored in the memory circuit 350. The processing circuit 340 may also be composed of hardware such as an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit). Various functions described later can also be realized by this hardware. Furthermore, the processing circuit 340 can realize various functions by combining software processing by the processor and programs with hardware processing.

[0024] The memory circuit 350 is a storage medium that includes ROM (Read Only Memory), RAM (Random Access Memory), and external storage devices such as HDDs (Hard Disk Drives) and optical disc drives. The memory circuit 350 stores various information and data, as well as various programs executed by the processor provided in the processing circuit 340. Furthermore, the memory circuit 350 can store information for re-collecting MR signals, such as phase encoding of invalidated MR signals, and information on predetermined thresholds for determining which MR signals to invalidate. In addition, the memory circuit 350 can store information on thresholds for invalidating MR signal data based on the signal strength of the MR signal.

[0025] The console 400 is configured as a computer having a processing circuit 40, a memory circuit 41, a display 42, and an input device 43. The console 400 is an example of an image processing device.

[0026] The configuration of the processing circuit 40 and the memory circuit 41 is equivalent to that of the processing circuit 340 and memory circuit 350 of the sequence controller 34, so a detailed explanation is omitted. The display 42 is a display device such as a liquid crystal display panel, plasma display panel, or organic EL panel. The input device 43 includes, for example, a mouse, keyboard, trackball, or touch panel, and includes various devices for the user to input various types of information.

[0027] Through these components, the console 400 controls the entire magnetic resonance imaging apparatus 1. Specifically, it receives imaging conditions and other various information and instructions from users such as medical technologists through the operation of a mouse, keyboard, or other input device 43. The processing circuit 40 then causes the sequence controller 34 to execute a scan based on the input imaging conditions, while simultaneously reconstructing the image based on the data transmitted from the sequence controller 34. The reconstructed image is displayed on the display 42 or stored in the memory circuit 41.

[0028] The magnetic resonance imaging apparatus 1 is equipped with an interface 4. Interface 4 can receive information to exclude data that may impair the quality of the MR image during MR signal data acquisition in order to acquire data while maintaining image quality. Interface 4 may be configured to receive information from other magnetic resonance imaging apparatuses. Interface 4 may be configured to receive information from an external RF pulse detector 5 (see Figure 11), which will be described later and installed in another magnetic resonance imaging apparatus. Interface 4 may be configured to receive information from an interference signal detector 6 (see Figure 12), which will be described later and installed in the examination room of the magnetic resonance imaging apparatus 1. Information reception at interface 4 may be wired or wireless.

[0029] (Influence of other magnetic resonance imaging devices) Incidentally, it is known that when two or more magnetic resonance imaging (MR) devices are installed in close proximity in facilities such as hospitals, the quality of the reconstructed MR signal image (i.e., the MR image) may not be maintained because the effects of radio wave and magnetic field shielding are insufficient.

[0030] Before describing the operation of the magnetic resonance imaging apparatus 1 according to this embodiment, we will briefly explain the acquisition of general MR images and signal intensity, as well as the effects when two or more magnetic resonance imaging apparatuses are installed in close proximity, using Figure 2.

[0031] The magnetic resonance imaging (MRI) system collects MR signals generated from a subject in response to an RF pulse applied to the subject. Positional information of the MR signal is added by collecting data while superimposing gradient magnetic fields on a static magnetic field. Gradient magnetic fields are synthesized along the X, Y, and Z axes so that mutually orthogonal slice gradient magnetic fields Gs, phase-encoded gradient magnetic fields Gp, and read (i.e., frequency-encoded) gradient magnetic fields Gr are formed in the desired direction.

[0032] For example, the slice gradient magnetic field Gs arbitrarily selects an imaging cross-section (slice), the phase encode gradient magnetic field Gp encodes the phase of MR signals in accordance with spatial positions, and the read gradient magnetic field Gr encodes the frequency of MR signals in accordance with spatial positions. Further, in the acquisition of three-dimensional MR images, the slice gradient magnetic field Gs encodes the phase of MR signals in the slice direction in accordance with spatial positions. Then, MR signal data appended with spatial position information is acquired.

[0033] An MR image is reconstructed by performing two-dimensional or three-dimensional Fourier transform on two-dimensional or three-dimensional k-space filled with acquired MR signal data.

[0034] FIG. 2 shows a state where data acquisition via a 2D spin echo (SE) method is performed in parallel by one magnetic resonance imaging apparatus, and MR signal data acquisition via a 2D gradient echo (GRE) method is performed in parallel by another magnetic resonance imaging apparatus.

[0035] In the SE method, a 90° RF pulse and a 180° RF pulse are continuously applied at a repetition time (TR) as a combination of a series of RF pulses. By continuously applying the combination of a series of RF pulses at TR, a steady state is achieved, and an MR signal is observed at an echo time (TE). The spins are refocused by application of a 180° RF pulse at TE / 2 after application of the 90° RF pulse, and a spin echo MR signal is observed at TE / 2 after application of the 180° RF pulse. MR signals are acquired as data during the sampling time (Ts) of the read gradient magnetic field Gr.

[0036] Further, spin-lattice relaxation time (T1) and spin-spin relaxation time (T2) differ depending on biological tissues, respective diseases, and the like. When TE << TR, the signal intensity formula Sig_SE for a general SE method is given by formula (1) below. ρ is the proton density.

[0037] [[MATHEMATICAL EXPRESSION]]

[0038] As shown in equation (1), by setting TR and TE to short values, such as TR=500ms and TE=15ms, contrast emphasizing T1 can be achieved. By setting TR and TE to long values, such as TR=3000ms and TE=120ms, contrast emphasizing T2 can be achieved. By combining TR and TE, an MR image with the desired contrast can be obtained.

[0039] Furthermore, in the GRE method (also called the FE method), protons are excited using an RF pulse with a flip angle θ°, and then an encoding gradient magnetic field is applied. Instead of refocusing by applying a 180° RF pulse as in the SE method, the polarity of the lead gradient magnetic field Gr is reversed, and the MR signal is observed after TE from the θ° RF pulse. The general signal intensity formula Sig_GRE for the GRE method is given by equation (2) when TR >> T2. Note that in the GRE method, due to the effects of magnetic field inhomogeneity, T2 is used instead of T2. * This is the result.

[0040]

number

[0041] As shown in equation (2), an MR image with enhanced contrast can be obtained by combining TR, TE, and flip angle. Furthermore, contrast may be adjusted by forced phase dispersion, such as RF pulse spoiling. In addition, contrast may be adjusted by other known methods, such as the inversion time (TI) in the IR method and various prepulses.

[0042] Thus, in order to acquire an MR image with the desired contrast enhanced, RF pulses are continuously applied by the TR, and the MR signal is observed in a steady state. Furthermore, as shown in equations (1) and (2), the signal intensity of the acquired MR signal differs depending on the type of pulse sequence, the setting of imaging conditions using various parameters, etc. Although Figure 2 shows the acquisition of MR signal data using the SE method and the GRE method, the type of pulse sequence may also be a high-speed imaging method such as the FSE method or the EPI method.

[0043] Next, we will explain the effects of installing two or more magnetic resonance imaging (MRI) systems in close proximity. For example, depending on the type of pulse sequence, the settings of imaging conditions using various parameters, etc., the application of external RF pulses from one MRI system may overlap with the data acquisition of the MR signal from another MRI system. Conversely, the application of RF pulses from one MRI system may overlap with the data acquisition of the MR signal from another MRI system.

[0044] In such cases, for example, if the effects of radio wave / magnetic field shielding are insufficient, external RF pulses from other magnetic resonance imaging (MMRI) devices may be mixed into the MR signal data of one MMRI device as interference signals, causing artifacts in the MR image. Furthermore, during data acquisition of the MR signal from one MMRI device, external electromagnetic waves originating from another MMRI device may be accidentally received as interference signals, impairing the quality of the MR image. This is particularly true when the static magnetic field strength of two MMRI devices installed in close proximity is the same, as the magnetic resonance frequencies (i.e., Larmor frequencies) of both devices will be almost identical, making them susceptible to adverse effects.

[0045] Furthermore, in facilities such as hospitals, when installing magnetic resonance imaging (MR) devices with the same static magnetic field strength in close proximity to each other, even if the Larmor frequencies of the two devices are slightly offset, the bandwidth of the RF pulses, the frequency offset of the RF pulses for multislice selection, etc., can cause the Larmor frequency bandwidths of the MR device and the other MR device to overlap, potentially adversely affecting the MR image.

[0046] Therefore, when the magnetic resonance imaging apparatus 1 according to this embodiment is installed in close proximity to at least one other magnetic resonance imaging apparatus, it excludes data that could impair the quality of the MR image during MR signal data acquisition in order to acquire data while maintaining image quality. In this specification, the RF pulses output by the "other magnetic resonance imaging apparatus" are called "external RF pulses," and the RF pulses output by the "magnetic resonance imaging apparatus 1" that is affected by the "other magnetic resonance imaging apparatus" are simply called "RF pulses" to distinguish between the two.

[0047] Note that the configuration and operation of other magnetic resonance imaging devices are substantially the same as the magnetic resonance imaging device 1 according to at least one embodiment described below, and therefore will not be described. Furthermore, by having other magnetic resonance imaging devices have the configuration and operation of the magnetic resonance imaging device 1 according to at least one embodiment described below, both devices can exclude data that may impair the quality of MR images during MR signal data acquisition.

[0048] In order to exclude data that may impair the quality of MR images during MR signal data acquisition, the magnetic resonance imaging apparatus 1 according to the first and second embodiments provides a method for receiving information from other magnetic resonance imaging apparatuses, and the magnetic resonance imaging apparatus 1 according to the third embodiment provides a method for detecting information in the magnetic resonance imaging apparatus 1.

[0049] (First Embodiment) Figure 3 is a diagram illustrating the relationship between the magnetic resonance imaging apparatus 1 according to the first embodiment and other magnetic resonance imaging apparatuses. The interface 4 of the magnetic resonance imaging apparatus 1 according to the first embodiment is configured to communicate with other magnetic resonance imaging apparatuses so as to receive timing signals of at least external RF pulses from pulse sequences being executed by the other magnetic resonance imaging apparatuses. The interface 4 can receive timing signals related to the application timing of external RF pulses transmitted from other magnetic resonance imaging apparatuses, for example, from timing circuits such as RF transmitters, sequence controllers, and processing circuits of the other magnetic resonance imaging apparatuses.

[0050] As shown in Figure 1, the processing circuit 340 implements the following functions: acquisition function 341, determination function 342, and reacquisition function 343. The acquisition function 341 acquires the MR signal. The determination function 342 determines whether external RF pulses from other magnetic resonance imaging devices may affect the MR signal being acquired. If the determination determines that the MR signal may be affected, the reacquisition function 343 invalidates the MR signal being acquired and reacquires the invalidated MR signal.

[0051] The configuration and operation of each of the above functions of the processing circuit 340 will be explained using the flowchart in Figure 4, Figures 5 and 6. For the sake of clarity in the following explanation, the data acquisition in step ST20 of Figure 4 will be referred to as step ST20A when data is acquired by the acquisition function 341, and as step ST20B when data is acquired by the reacquisition function 343.

[0052] First, the subject P is placed on the tabletop 15 of the bed 16. Then, the processing circuit 340 sets the sequence controller 34 to perform a scan based on imaging conditions obtained from user input, pre-set examination type, examination name, etc., such as various parameters like phase encoding count, TE, TR, etc. The phase encoding count is arbitrarily selected according to the image resolution, image signal-to-noise ratio, imaging time, etc.

[0053] Phase encoding is performed based on the number of phase encodings. For example, if the imaging conditions result in 256 phase encodings, then the case where no phase encoding gradient magnetic field is applied is defined as 0 encoding, and the phase encoding gradient magnetic field is divided into 128 segments on the positive side and 127 segments on the negative side from 0 encoding. MR signal data is then collected for all phase encodings. Half-Fourier method may also be used.

[0054] In step ST10, the acquisition function 341 sets the initial value of the phase encoding. The initial value of the phase encoding is set based on imaging conditions such as various parameters. Alternatively, it may be set based on information or tables related to phase encoding stored in the memory circuit 350.

[0055] In step ST20A, the acquisition function 341 acquires MR signal data in units of the set phase encoding repetition time. If the process proceeds from step ST10 to step ST20A, the initial phase encoding is used; if the process proceeds from step ST50A to step ST20A, the phase encoding modified in step ST50A is used. Furthermore, regardless of whether it is determined whether an external RF pulse may affect the MR signal being acquired, the acquisition function 341 acquires the MR signal while maintaining a constant repetition time and the period of RF pulse application for generating the MR signal.

[0056] In step ST30, the determination function 342 determines, for each unit of repetition time, whether or not an external RF pulse may affect the MR signal being acquired. Whether or not an external RF pulse may affect the MR signal being acquired is determined by whether or not the MR signal acquisition period, i.e., the MR signal sampling time, overlaps with an external RF pulse from another magnetic resonance imaging device.

[0057] The overlap between the sampling time of the MR signal and the external RF pulse is determined based on the timing signal of the external RF pulse application received by interface 4. The timing signal received by interface 4 only needs to indicate the timing of the external RF pulse application; instead of the timing signal of the external RF pulse application, it may be, for example, a timing signal of the gradient for selectively exciting the slice.

[0058] If, in step ST30, it is determined that an external RF pulse may affect the MR signal being acquired (i.e., YES in Figure 4), the process proceeds to step ST20B, in which the MR signal described later is acquired again in the same phase-encoded state as the invalidated MR signal.

[0059] In step ST20B, the reacquisition function 343 acquires MR signal data in units of the repetition time in phase encoding. The reacquisition function 343 acquires an MR signal with the same phase encoding as the invalidated MR signal immediately after it was invalidated. Furthermore, the reacquisition function 343 acquires the MR signal while maintaining a constant repetition time and the period of RF pulse application to generate the MR signal, regardless of whether it is determined whether an external RF pulse may affect the MR signal being acquired.

[0060] Here, using Figures 5 and 6, we will specifically explain the method for acquiring K-space data in the magnetic resonance imaging apparatus 1 when it is affected by an external RF pulse during MR signal data acquisition. The hatching in Figure 6 indicates MR signal data that has been invalidated and then reacquired. Here, "view" refers to a specific readout line in K-space that is acquired with a specific phase encoding. For example, the magnetic resonance imaging apparatus 1 uses a two-dimensional SE method to change the phase encoding up to View N (N: natural number) under steady conditions so that MR signal data for each view can be acquired, from View 1, View 2, View 3, View 4, ... As shown in Figure 5, for example, if an external RF pulse timing signal is received while acquiring data for the MR signal of View 2, the MR signal data for View 2 is invalidated. Then, the MR signal for View 2 is acquired again immediately after it was invalidated, using the same phase encoding as the invalidated MR signal.

[0061] Returning to Figure 4, if it is determined in step ST30 that the external RF pulse cannot affect the MR signal being acquired (i.e., NO in Figure 4), the process proceeds to step ST40, which determines the termination of the sequence, as described later.

[0062] In step ST40, the acquisition function 341 and the reacquisition function 343 determine whether or not data acquisition of all MR signals has been completed.

[0063] If it is determined in step ST40 that data acquisition for all MR signals has not been completed (i.e., NO in Figure 4), the process proceeds to step ST50A, which involves changing the phase encoding, as described later. If it is determined in step ST40 that data acquisition for all MR signals has been completed (i.e., YES in Figure 4), the process terminates. Once data acquisition for all MR signals is complete, the MR image is reconstructed.

[0064] In step ST50A, the acquisition function 341 changes the phase encoding. After changing the phase encoding, the process proceeds to step ST20A, where the MR signal is acquired sequentially in repeated time units. The phase encoding change is performed, for example, based on information or tables about the phase encoding stored in the memory circuit 350.

[0065] According to the magnetic resonance imaging apparatus 1 of the first embodiment, when other magnetic resonance imaging apparatuses are installed in close proximity, the timing of the application of an external RF pulse can be received, thereby excluding data that could impair the quality of the MR image during MR signal data acquisition, and enabling MR signal acquisition while maintaining image quality. Therefore, it may lead to a reduction in considerations for the installation environment, such as the installation location, when installing magnetic resonance imaging apparatuses with the same static magnetic field strength. It may also lead to a reduction in the requirements for shielded rooms such as radio wave and magnetic field shielding.

[0066] (Modified example of the first embodiment) Figure 7 is a flowchart showing an example of data acquisition operation for an MR signal according to a first modification of the first embodiment. As shown in Figure 7, in the magnetic resonance imaging apparatus 1 of the first modification of the first embodiment, when it is determined that an external RF pulse may affect the MR signal being acquired, information regarding the phase encoding of the MR signal that has been invalidated by the determination is stored, and after the completion of a sequence of phase encodings, an MR signal with the same phase encoding as the invalidated MR signal is acquired again. In this respect, it differs from the first embodiment, in which an MR signal with the same phase encoding as the invalidated MR signal was acquired again immediately after it was invalidated. Other configurations and operations are substantially the same as those of the first embodiment shown in Figure 1, so the same components are denoted by the same reference numerals and their descriptions are omitted.

[0067] For the sake of clarity in the following explanation, step ST20A will be used when data is collected by the acquisition function 341, and step ST20C will be used when data is collected by the re-acquisition function 343. Similarly, step ST50A will be used when the phase encoding is changed by the acquisition function 341, and step ST50B will be used when the phase encoding is changed by the re-acquisition function 343.

[0068] Steps ST10 and ST20A, which are substantially the same as those in the first embodiment, are denoted by the same reference numerals, and redundant explanations are omitted. After step ST20A, proceed to step ST31.

[0069] In step ST31, the determination function 342 determines, for each unit of repetition time, whether or not an external RF pulse can affect the MR signal being acquired. If it is determined that the external RF pulse can affect the MR signal being acquired, the memory circuit 350 stores information regarding the phase encoding of the MR signal that was deemed invalid by the determination. In step ST31, regardless of the determination of whether or not the external RF pulse can affect the MR signal being acquired, the process proceeds to step ST35.

[0070] In step ST35, the acquisition function 341 and the reacquisition function 343 determine whether the sequence has finished. "Sequence completion" means that the execution of the planned sequence of "group of phase encodings" has finished, regardless of whether it has been determined that an external RF pulse may affect the MR signal being acquired. "Group of phase encodings" refers to all the phase encodings required for the reconstruction of the MR image, and all the phase encodings within groups if all the phase encodings are divided into multiple groups.

[0071] If the end of a sequence is determined by whether or not all phase encoding has been completed, then after data acquisition for all phase encodings, the phase encoding data of the invalidated MR signals that were stored will be acquired again.

[0072] Furthermore, if all phase encodings are divided into multiple groups, and the end of the sequence is determined by whether the phase encoding for that group has finished, then after collecting data for a particular group's phase encoding, the data for the invalidated MR signals that were stored will be collected again. This process of data collection and re-collection will be repeated for other specific groups until data for all groups, i.e., all phase encoding data, is collected.

[0073] If it is determined in step ST35 that the sequence has not finished (i.e., NO in Figure 7), the process proceeds to step ST50A. Step ST50A is substantially the same as step ST50A in Figure 4, so redundant explanations are omitted.

[0074] If it is determined in step ST35 that the sequence has finished (i.e., YES in Figure 7), the process proceeds to step ST41. If it is determined in step ST41 that data acquisition for all MR signals has not finished (i.e., NO in Figure 7), the process proceeds to step ST60, which will be described later. If it is determined in step ST41 that data acquisition for all MR signals has finished (i.e., YES in Figure 7), the process ends. Once data acquisition for all MR signals is complete, the MR image is reconstructed.

[0075] Specifically, in step ST60, the reacquisition function 343 acquires information regarding the phase encoding of the stored invalid MR signal and sets it as a new phase encoding. Step ST60 proceeds to step ST20C.

[0076] In step ST20C, the reacquisition function 343 acquires MR signal data in units of the repetition time in phase encoding. The reacquisition function 343 acquires MR signals with the same phase encoding as the invalidated MR signal again after the sequence has finished. Furthermore, the reacquisition function 343 acquires MR signals while maintaining a constant repetition time and the period of RF pulse application to generate the MR signal, regardless of whether it is determined whether an external RF pulse may affect the MR signal being acquired.

[0077] The operation after the stored information regarding the phase encoding of the invalidated MR signal is set as the new phase encoding is substantially the same as the operation described above, except that if it is determined in step ST35 that the sequence has not finished (i.e., NO in Figure 7), the system proceeds to step ST50B. Therefore, redundant explanations are omitted.

[0078] In step ST50B, the reacquisition function 343 changes the phase encoding. After changing the phase encoding, the process proceeds to step ST20C, where the MR signal is acquired sequentially in repeated time units. The phase encoding change is performed, for example, based on information or tables about the phase encoding stored in the memory circuit 350.

[0079] (Second modified example of the first embodiment) Figure 8 is a schematic diagram showing an example of the overall configuration of a magnetic resonance imaging apparatus 1 according to a second modification of the first embodiment. As shown in Figure 8, the magnetic resonance imaging apparatus 1 according to the second modification of the first embodiment differs from the first embodiment in that it further implements a notification function 344 in the processing circuit 340. Since the other configurations and operations are substantially the same as those of the first embodiment shown in Figure 1, the same reference numerals are used for the same components and their descriptions are omitted.

[0080] If the notification function 344 determines that an external RF pulse may affect the MR signal being acquired, and the exposure time is extended due to a series of invalid MR signal data, the notification function 344 may notify the user of the extension of the exposure time via the display 42, voice, etc.

[0081] Furthermore, if the notification function 344 determines that an external RF pulse may affect the MR signal being acquired, it may notify the user via the display 42, voice, etc., of the extended imaging time newly calculated based on the number of invalidated MR signal data and imaging conditions such as TR.

[0082] According to the magnetic resonance imaging apparatus 1 relating to the second modification of the first embodiment, the user can be aware of the extension of the imaging time and can consider new responses in accordance with that extension, such as taking into consideration the burden on the patient P who is the subject.

[0083] (Third modified example of the first embodiment) In the first embodiment, data acquisition of one view of the MR signal was performed per TR, whereas the magnetic resonance imaging apparatus 1 according to the third modification of the first embodiment acquires data of multiple views of the MR signal per TR. Figures 9 and 10 illustrate the case where the MR signal is affected by an external RF pulse during data acquisition, using the two-dimensional fast spin echo (FSE) method as an example. Note that TE is the effective TE. Figures 9 and 10 show an example where the total number of views required for image generation is N, the total views are divided into four segments, and each view within one segment is acquired during the period of one TR. In other words, Figures 9 and 10 show an example where the number of echoes per TR is N / 4. Note that the number of echoes per TR can be set according to the imaging conditions.

[0084] In Figure 9, for example, in the first TR, the phase encoding is changed up to view (N-3) so that MR signal data for each view, such as view 1, view 5, view 9, ..., can be collected. In the second TR, the phase encoding is changed up to view (N-2) so that MR signal data for each view, such as view 2, view 6, view 10, ..., can be collected, until finally MR signal data from view 1 to view N (N: natural number) is collected.

[0085] For example, if an external RF pulse timing signal is received during data acquisition of the MR signal in view 6 during the second TR, the MR signal data for view 6 is invalidated. In this case, in the third TR immediately following the invalidation, the MR signal data is acquired again, including at least the MR signal for view 6, which has the same phase encoding as the invalidated MR signal. As shown by the hatching in Figure 10, for example, not only the invalidated view 6, but also the data of multiple MR signals from views 2, 6, 10, ..., and (N-2), which were acquired during the second TR, may be acquired again during the third TR.

[0086] In other words, the acquisition function 341 sequentially acquires multiple MR signals in units of repetition time while changing multiple phase encodings at predetermined repetition times, the determination function 342 determines, for each unit of repetition time, whether or not an external RF pulse can affect at least one of the multiple MR signals being acquired, and the reacquisition function 343 may reacquire the same multiple phase encodings as the multiple MR signals that were deemed invalid if it is determined that an external RF pulse can affect at least one of the multiple MR signals being acquired.

[0087] (Other modifications of the first embodiment) In the magnetic resonance imaging apparatus 1 according to the first embodiment and the third modified embodiment of the first embodiment, two-dimensional SE method and FSE method were used for the explanation. However, in addition to the SE method and FSE method, known two-dimensional and three-dimensional pulse sequences such as the IR method, SSFP method, GRE method, and EPI method can be used.

[0088] When acquiring MR signals in three dimensions, the phase encoding includes slice phase encoding using a slice gradient magnetic field Gs. The MR signals are acquired sequentially in units of repetition time while changing the slice phase encoding at predetermined repetition times. At each unit of repetition time, it is determined whether an external RF pulse can affect the MR signal being acquired, and the MR signal with the same slice phase encoding as the invalidated MR signal may be acquired again immediately after it was invalidated, or after the completion of a group of slice phase encodings. When acquiring data for all slices of MR signals for the same view, changing the view, and acquiring data for all slices of MR signals for the next view, a group of slice phase encodings may be set to, for example, all slice phase encodings for one phase encoding gradient magnetic field Gp.

[0089] Furthermore, Figures 6 and 10 illustrate a Cartesian acquisition method in which multiple MR signals with different phase encodings are collected by gradually changing the phase-encoded gradient magnetic field Gp, and the K-space is filled so that the signals are aligned in parallel directions in K-space. However, the K-space data collection method may also be a known non-Cartesian acquisition method, such as a radial acquisition method, in which the data of multiple MR signals with different rotation angles are arranged radially around the origin of K-space. For example, when collecting MR signals using the radial acquisition method, phase encoding may be performed using a phase-encoded gradient magnetic field Gp and a lead gradient magnetic field Gr. That is, if it is determined that an external RF pulse may affect the MR signal being collected by the radial acquisition method, the MR signal being collected may be invalidated, and the invalidated MR signal may be collected again.

[0090] (Second embodiment) Figure 11 illustrates the relationship between the magnetic resonance imaging apparatus 1 according to the second embodiment and another magnetic resonance imaging apparatus. As shown in Figure 11, the magnetic resonance imaging apparatus 1 according to the second embodiment differs from the first embodiment in that it receives a timing signal for the application of an external RF pulse from an external RF pulse detector 5 provided in the inspection chamber B of the other magnetic resonance imaging apparatus. Furthermore, the interface 4 of the magnetic resonance imaging apparatus 1 according to the second embodiment is configured to receive information from the external RF pulse detector 5. Other configurations and operations are substantially the same as those of the first embodiment shown in Figure 1, so the same components are denoted by the same reference numerals and their descriptions are omitted.

[0091] The magnetic resonance imaging apparatus 1 further includes an external RF pulse detector 5 in the inspection chamber B of the other magnetic resonance imaging apparatus. The external RF pulse detector 5 is configured to detect the timing signal of the external RF pulse application of the other magnetic resonance imaging apparatus. The external RF pulse detector 5 transmits the timing signal of the external RF pulse application to interface 4. Interface 4 can also receive the timing signal of the external RF pulse application from the external RF pulse detector 5. Furthermore, the operation of the magnetic resonance imaging apparatus 1 according to the second embodiment is substantially the same as that of the first embodiment shown in Figure 4, except that it utilizes the timing signal of the external RF pulse application received from the external RF pulse detector 5, so a description is omitted.

[0092] According to the magnetic resonance imaging apparatus 1 of the second embodiment, even if the magnetic resonance imaging apparatus 1 and another magnetic resonance imaging apparatus are not able to communicate with each other, such as being products of other companies, it is possible to receive the timing signal of the application of an external RF pulse, and to exclude data that may impair the quality of the MR image when acquiring MR signal data.

[0093] (Third embodiment) Figure 12 is a schematic diagram showing an example of the overall configuration of the magnetic resonance imaging apparatus 1 according to the third embodiment. As shown in Figure 12, the magnetic resonance imaging apparatus 1 according to the third embodiment differs from the first embodiment in that it further includes an interference signal detector 6 that includes an external RF pulse. In addition, the interface 4 of the magnetic resonance imaging apparatus 1 according to the third embodiment is configured to receive information from the interference signal detector 6. Other configurations and operations are substantially the same as those of the first embodiment shown in Figure 1, so the same components are denoted by the same reference numerals and their descriptions are omitted.

[0094] Figure 12 illustrates the relationship between the magnetic resonance imaging apparatus 1 according to the third embodiment and other magnetic resonance imaging apparatuses. As shown in Figure 12, an interference signal detector 6 is further provided in the examination room A where the magnetic resonance imaging apparatus 1 is installed.

[0095] The interference signal detector 6 consists of, for example, an antenna 61, a bandpass filter (BPF) 62, and a detector 63. The antenna 61 receives interference signals. Interference signals include, for example, noise generated during data acquisition of MR signals in the magnetic resonance imaging apparatus 1, external RF pulses from other magnetic resonance imaging apparatuses, or noise caused by external RF pulses. The bandpass filter 62 allows interference signals in the magnetic resonance frequency band at the static magnetic field strength of the magnetic resonance imaging apparatus 1 to pass through from the interference signals received by the antenna 61. The detector 63 detects interference signals in the frequency band that have passed through the bandpass filter 62. The interference signal detector 6 transmits information about the detected interference signals to the interface 4 of the magnetic resonance imaging apparatus 1.

[0096] Furthermore, the interference signal detector 6 is installed outside the magnetic resonance imaging apparatus 1 within examination room A. At least the antenna 61 of the interference signal detector 6 may be installed, for example, within examination room A and close to examination room B where another magnetic resonance imaging apparatus is installed. If installed close to examination room B, interference signals originating from the other magnetic resonance imaging apparatus can be received efficiently.

[0097] Figure 13 is a flowchart showing an example of the operation of MR signal data acquisition according to the third embodiment. As shown in Figure 4, in the first embodiment, it was determined whether an external RF pulse could affect the MR signal being acquired based on whether the MR signal data acquisition and the timing signal transmitted from the application of an external RF pulse by another magnetic resonance imaging device overlapped. In contrast, the third embodiment differs from the first embodiment in that it determines whether an interfering signal, including an external RF pulse, could affect the MR signal being acquired based on information about the interfering signal detected during MR signal data acquisition.

[0098] Steps ST10, ST20 (ST20A, ST20B), ST40, and ST50A, which are substantially the same as those in the first embodiment shown in Figure 4, are denoted by the same reference numerals, and redundant explanations are omitted. However, in steps ST20 (ST20A, ST20B) and ST50A, the acquisition function 341 and the reacquisition function 343 acquire the MR signal while maintaining a constant repetition time and the period of RF pulse application for generating the MR signal, regardless of whether it is determined whether an interfering signal, including an external RF pulse, may affect the MR signal being acquired.

[0099] In step ST32, the determination function 342 determines, for each unit of repetition time, whether the interfering signal can affect the MR signal being acquired, based on information about the interfering signal received by the interface 4. For example, the determination function 342 determines that the interfering signal can affect the MR signal being acquired if the interfering signal detector 6 detects an interfering signal exceeding a predetermined threshold during MR signal acquisition.

[0100] Step ST32 will now be explained in more detail using Figure 14. As shown in Figure 14, for example, the magnetic resonance imaging apparatus 1 changes the phase encoding up to view N (N: natural number) so that it can collect MR signal data for each view, view 1, view 2, view 3, view 4, ... under steady conditions, similar to the case in Figure 5. For example, if an interfering signal N1 above a predetermined threshold is detected while collecting MR signal data for view 2, the MR signal data for view 2 is invalidated. In this case, the MR signal for view 2 is collected again immediately after being invalidated, using the same phase encoding as the invalidated MR signal. While the MR signal for view 2 is being collected again, an interfering signal N2 is detected again, but since the interfering signal N2 is below a predetermined threshold, the data collected again is treated as valid, and the data for the next view, view 3, is collected.

[0101] The predetermined threshold may be set based on the signal intensity of the MR signal being collected and the signal intensity of interference signals caused by external RF pulses from other magnetic resonance imaging devices. For example, since the signal intensity of the MR signal being collected and the signal intensity of interference signals caused by external RF pulses from other magnetic resonance imaging devices are different in magnitude, the threshold can be set to exclude interference signals caused by larger external RF pulses. Alternatively, the predetermined threshold may be set from thresholds stored in the memory circuit 350 in advance, based on the efficiency of the antenna 61 and the detector 63, etc.

[0102] Furthermore, the predetermined threshold should be set so that the MR signal data is not unfairly invalidated depending on the signal strength of the MR signal being collected. For example, under conditions where the MR signal strength is high, the predetermined threshold should be set higher than under conditions where the MR signal strength is low.

[0103] The signal intensity of the acquired MR signal varies depending on the type of pulse sequence, the setting of imaging conditions using various parameters, etc., as shown in equations (1) and (2) above. A predetermined threshold may be set based on the type of pulse sequence and imaging conditions using various parameters, etc., executed by the magnetic resonance imaging apparatus. Furthermore, the signal intensity of the acquired MR signal varies depending on the magnitude of the RF pulse output applied to the subject P and the type of coil that receives the MR signal. Therefore, a predetermined threshold may be set based on the magnitude of the RF pulse output applied to the subject P by the magnetic resonance imaging apparatus and information about the coil that receives the MR signal.

[0104] According to the magnetic resonance imaging apparatus 1 of the third embodiment, invalid data can be excluded when external RF pulses from other magnetic resonance imaging apparatuses are mixed in as interfering signals during MR signal data acquisition. In addition, invalid data can also be excluded when external electromagnetic waves or the like, which may accidentally degrade the quality of MR images, are generated by other magnetic resonance imaging apparatuses and mixed in as interfering signals.

[0105] According to the magnetic resonance imaging apparatus of at least one embodiment described above, MR signals can be acquired while maintaining image quality even when other magnetic resonance imaging apparatuses are installed in close proximity.

[0106] In the above embodiments, the term "processor" refers to circuits such as dedicated or general-purpose CPUs (Central Processing Units), GPUs (Graphics Processing Units), Application Specific Integrated Circuits (ASICs), and programmable logic devices (e.g., Simple Programmable Logic Devices (SPLDs), Complex Programmable Logic Devices (CPLDs), and Field Programmable Gate Arrays (FPGAs)). When the processor is a CPU, for example, it realizes various functions by reading and executing programs stored in memory circuits. When the processor is an ASIC, for example, instead of storing programs in memory circuits, functions equivalent to those programs are directly incorporated as logic circuits within the processor's circuitry. In this case, the processor realizes various functions through hardware processing that reads and executes the programs incorporated within the circuitry. Alternatively, the processor can also realize various functions by combining software processing and hardware processing.

[0107] Furthermore, although the above embodiment shows an example where a single processor in the processing circuit implements each function, a processing circuit may be configured by combining multiple independent processors, with each processor implementing each function. Also, when multiple processors are provided, the memory circuit for storing programs may be provided individually for each processor, or a single memory circuit may store programs corresponding to the functions of all processors together.

[0108] In the description of the embodiment, the collection function 341, the determination function 342, and the re-collection function 343 are examples of the collection unit, determination unit, and re-collection unit as described in the claims, respectively.

[0109] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of Symbols]

[0110] 1 Magnetic Resonance Imaging System 4…Interface 5…External RF Pulse Detector 6…Interference Signal Detector 10…Static Magnetic Field Magnet 11…Gradient Coil 33…RF Transmitter 34…Sequence Controller 61…Antenna 62…Bandpass Filter 63…Detector P…Subject 340…Processing Circuit 350…Memory Circuit 341…Acquisition Function 342…Judgment Function 343…Re-acquisition Function 344…Notification Function

Claims

1. A magnetic resonance imaging apparatus installed in close proximity to at least one other magnetic resonance imaging apparatus, A collection unit that collects MR signals generated from a subject in response to an RF pulse applied to the subject, A determination unit that determines whether an external RF pulse from the other magnetic resonance imaging apparatus can affect the MR signal being acquired, If the determination in the above determination determines that the MR signal may be affected, the re-acquisition unit invalidates the MR signal being acquired and re-acquisitions the invalidated MR signal. A magnetic resonance imaging system equipped with the following features.

2. The acquisition unit sequentially acquires the MR signal in units of the predetermined repetition time while changing the phase encoding at predetermined repetition times. The determination unit determines, for each unit of the repetition time, whether the external RF pulse can affect the MR signal being acquired. If the reacquisition unit determines that the external RF pulse may affect the MR signal being acquired, it reacquisitions the MR signal with the same phase encoding as the invalidated MR signal. The magnetic resonance imaging apparatus according to claim 1.

3. The acquisition unit and the reacquisition unit acquire the MR signal while maintaining the repetition time and the period of applying the RF pulse to generate the MR signal at a constant level, regardless of whether the external RF pulse may affect the MR signal being acquired. The magnetic resonance imaging apparatus according to claim 2.

4. The re-collection unit re-collects the MR signal with the same phase encoding as the invalidated MR signal immediately after it was invalidated, or after the completion of a group of phase encodings. The magnetic resonance imaging apparatus according to claim 2.

5. The acquisition unit sequentially acquires multiple MR signals in units of the predetermined repetition time while changing multiple phase encodings at predetermined repetition times. The determination unit determines, for each unit of the repetition time, whether the external RF pulse can affect at least one of the multiple MR signals being acquired. If the reacquisition unit determines that the external RF pulse may affect at least one of the multiple MR signals being acquired, it reacquises the multiple phase-encoded MR signals that were invalidated. The magnetic resonance imaging apparatus according to claim 1.

6. The phase encoding, when the MR signal is acquired in three dimensions, includes slice phase encoding. The magnetic resonance imaging apparatus according to claim 2.

7. The device further comprises an interface for receiving the timing signal of the external RF pulse application of the other magnetic resonance imaging apparatus, The determination unit determines, based on the timing signal of the application of the external RF pulse received by the interface, whether or not the external RF pulse can affect the MR signal being acquired. The magnetic resonance imaging apparatus according to claim 1.

8. The interface is configured to communicate with the other magnetic resonance imaging apparatus and to receive the timing signal of the external RF pulse application transmitted from the other magnetic resonance imaging apparatus. The magnetic resonance imaging apparatus according to claim 7.

9. The inspection chamber of the other magnetic resonance imaging apparatus further includes an external RF pulse detector for detecting the timing signal of the applied external RF pulse, The interface receives the timing signal of the application of the external RF pulse from the external RF pulse detector. The magnetic resonance imaging apparatus according to claim 7.

10. A interference signal detector for detecting interference signals including the aforementioned external RF pulses, The system further comprises an interface for receiving information about the interference signal detected by the interference signal detector, The determination unit determines, based on information regarding the interference signal received by the interface, whether or not the interference signal can affect the MR signal being collected. The magnetic resonance imaging apparatus according to claim 1.

11. The determination unit determines, when the interference signal is detected by the interference signal detector at a level exceeding a predetermined threshold during the acquisition of the MR signal, that the interference signal may affect the MR signal being acquired. The magnetic resonance imaging apparatus according to claim 10.

12. The interference signal detector detects the interference signal in the magnetic resonance frequency band at the static magnetic field strength of the magnetic resonance imaging apparatus. The magnetic resonance imaging apparatus according to claim 10.

13. The predetermined threshold is set based on the signal intensity of the MR signal being collected and the signal intensity of the interference signal caused by the external RF pulse. The magnetic resonance imaging apparatus according to claim 11.

14. The predetermined threshold is set based on at least one of the following: the type of pulse sequence being performed in the magnetic resonance imaging apparatus, the imaging conditions, the magnitude of the RF pulse output, and information about the coil receiving the MR signal. The magnetic resonance imaging apparatus according to claim 11.

Images