JP5322389B2 - Magnetic resonance imaging system - Google Patents

Description

  The present invention relates to a magnetic resonance imaging (MRI) apparatus that enables imaging over a wide range by collecting magnetic resonance (MR) signals while moving a subject in the body axis direction.

    In the MRI method, a nuclear spin in a subject tissue placed in a static magnetic field is excited by a high-frequency signal (RF pulse) having the Larmor frequency, and image data is reconstructed from a magnetic resonance signal generated by the excitation. This is an imaging method.

  The MRI apparatus is an image diagnostic apparatus that images a subject using an MRI method. The MRI apparatus can obtain not only anatomical diagnostic information but also a lot of diagnostic information such as biochemical information and information for functional diagnosis. Therefore, the MRI apparatus is important in the field of today's image diagnosis.

FIG. 4 is a diagram schematically showing a gantry 120a of a conventional MRI apparatus. A main magnet 11a, a gradient magnetic field coil 21a, a transmission coil 31a, and a reception coil 33a are provided around an imaging field 130a provided at the center of the gantry 120a. The main magnet 11a and the gradient magnetic field coil 21a form a static magnetic field and a gradient magnetic field with respect to the subject 150 arranged in the imaging field 130a. The transmission coil 31a irradiates the subject 150 with an RF pulse. The receiving coil 33a detects the MR signal generated from the subject 150 with the irradiation of the RF pulse.

  On the other hand, a top plate 4a on which the subject 150 is placed is attached to the upper surface of a bed (not shown) so as to be slidable in the longitudinal direction (Z-axis direction). By inserting the subject 150 into the imaging field 130a together with the top 4a, a part of the subject (imaging target site) is set in the vicinity of the receiving coil 33a. In this case, the maximum imaging area is determined by the length D of the receiving coil 33a in the Z-axis direction.

  In recent years, in order to generate continuous image data for an area wider than the maximum imaging area, the MR signal collected while moving the top 4a continuously in the longitudinal direction is reconstructed to generate image data. Has been proposed (see, for example, Patent Document 1).

  According to the method proposed in Patent Literature 1, when MR signals are collected, the carrier frequency of the selective excitation RF pulse with respect to a predetermined slice cross section of the subject 150 is controlled to thereby move the subject 150 in motion. Since MR signals generated from a predetermined imaging target site can be always captured at the same frequency, a wide range of image data for the subject 150 can be generated.

In addition, an imaging method has been proposed in which the above-described method is further developed to enable a wide range of multi-slice imaging and oblique imaging (see, for example, Patent Document 2).
JP-A-8-71056 JP 2002-95646 A

  As described above, the MRI apparatus irradiates the subject 150 with an RF pulse having a frequency component in a predetermined band (for example, ± 250 KHz) centered on the Larmor frequency (for example, 63.9 MHz). An MR signal having the same frequency component as the RF pulse is received from the subject 150 to generate image data. Since this MR signal is an extremely small signal, it is necessary to eliminate noise having the same frequency component as much as possible. For this reason, the receiving coil 33a for detecting the MR signal and the gantry 120a provided with an amplification circuit (not shown) for amplifying the MR signal detected by the receiving coil 33a to a predetermined amplitude are installed in the shield room together with the bed. Has been.

  Therefore, in the generation of a wide range of image data by moving the subject 150 continuously (hereinafter referred to as wide range imaging), electromagnetic noise caused by the drive signal for moving the top 4a is caused by the reception coil 33a. There is a risk that unacceptable artifacts may occur in the image data obtained by reconstructing the MR signal.

  In particular, in an MRI apparatus in which the length D of the imaging field 130a is shortened and the opening of the imaging field 130a is widened in order to eliminate fear and anxiety of the subject 150 inserted into the imaging field 130a of the gantry 120a. Intrusion of electromagnetic noise into the coil 33a and the amplifier circuit is further facilitated.

  In addition to the drive signal for moving the top plate 4a, there are factors that cause electromagnetic noise to be mixed into the MR signal.

  The present invention has been made in consideration of such circumstances, and an object thereof is to reduce artifacts due to electromagnetic noise.

The magnetic resonance imaging apparatus according to the first aspect of the present invention irradiates an RF pulse to a subject placed on a top plate that moves in an imaging field in which a static magnetic field and a gradient magnetic field are formed. A magnetic resonance imaging apparatus that generates image data by collecting generated magnetic resonance signals while continuously moving the top plate, and a driving signal for moving the top plate during the collection period of the magnetic resonance signals Generation of.

In the magnetic resonance imaging apparatus according to the second aspect of the present invention, a magnetic field forming unit that forms a static magnetic field and a gradient magnetic field in an imaging field of magnetic resonance imaging, a top plate on which a subject is placed, and the top plate are moved. A top plate moving unit, a transmitting / receiving unit for irradiating an imaging target region of the subject located in the imaging field with an RF pulse, and receiving a magnetic resonance signal generated from the imaging target region, and a magnetic resonance signal The image data is generated based on the image data generator and continuously while the amount of the magnetic resonance signal necessary for the image data generator to generate the image data is received by the transmitter / receiver. It generates a drive signal for driving the top plate moving unit so as to move the top plate, and during the reception period of the magnetic resonance signal by the transmission / reception unit And a drive signal generating unit stops generating the serial drive signal.

Magnetic resonance imaging apparatus according to the third aspect of the present invention, the applying unit for applying a gradient magnetic field and radio frequency pulses to the subject in order to generate the magnetic resonance signals from a subject in a static magnetic field, before Ki磁 A high frequency coil for detecting a gas resonance signal, a data collection unit for collecting the magnetic resonance signal detected by the high frequency coil, and a magnetic resonance image based on the magnetic resonance signal collected by the data collection unit A reconstructing unit that reconstructs the magnetic resonance signal during a period in which the data collecting unit collects the top plate on which the subject is placed while continuously sliding in the longitudinal direction. a bed for temporarily OFF driving signal for driving the pre-SL drive signal while the OFF, and controls the application unit and the data collecting unit to collect the magnetic resonance signals And a control unit.

  A magnetic resonance imaging apparatus according to a fourth aspect of the present invention includes an application unit that applies a gradient magnetic field and a high-frequency pulse to the subject to generate a magnetic resonance signal from the subject in a static magnetic field, and the subject A bed that slides a top plate for placing the device in the longitudinal direction thereof, a high-frequency coil for detecting the magnetic resonance signal, and a data collection unit for collecting the magnetic resonance signal detected by the high-frequency coil; A reconstruction unit that reconstructs a magnetic resonance image based on the magnetic resonance signal collected by the data collection unit, and the application unit and the bed so as to collect the magnetic resonance signal while sliding the top plate And the data collection unit. The bed generates a drive signal for driving the top plate during a period in which the magnetic resonance signal is collected by the data collection unit. And a control unit for controlling so as not to.

  According to the present invention, artifacts caused by electromagnetic noise can be reduced.

  Hereinafter, an MRI apparatus 200 according to an embodiment will be described with reference to the drawings.

  A feature of the MRI apparatus 200 described below is to prevent mixing of electromagnetic noise due to the driving signal for moving the top board into the MR signal as follows. That is, the MRI apparatus 200 performs MR signals while moving a subject placed on a top plate substantially continuously at a predetermined speed in the body axis direction in an imaging field in which a static magnetic field, a gradient magnetic field, and an RF magnetic field are formed. To collect. The MRI apparatus 200 reconstructs image data relating to an area wider than the imaging field, based on MR signals obtained in time series from a plurality of imaging target parts of the subject. When performing such imaging, the MRI apparatus 200 controls generation of a drive signal based on information on MR signal acquisition timing (for example, information on acquisition start timing and information on acquisition end timing).

  Hereinafter, a case will be described in which the MRI apparatus 200 employs the spin echo (SE) method for collecting magnetic resonance data. However, other imaging methods such as a field echo (FE) method, an echo planar imaging (EPI) method, or an inversion recovery (IR) method may be employed.

The configuration of the MRI apparatus 200 will be described with reference to FIG . FIG. 1 is a block diagram showing the overall configuration of the MRI apparatus 200.

MRI apparatus 200 shown in FIG. 1 includes a static magnetic field generating unit 1, the gradient magnetic field generating section 2, the transceiver 3, the top plate 4, the moving mechanism unit 5, the image data generating unit 6, display unit 7, the input unit 8 and the control Part 9 is included.

The static magnetic field generation unit 1 includes a main magnet 11 and a static magnetic field power supply 12. As the main magnet 11, a normal conducting magnet or a superconducting magnet is applied. The static magnetic field power supply 12 supplies a current to the main magnet 11. With such a configuration, the static magnetic field generating unit 1 forms a strong static magnetic field in the imaging field of a gantry (see FIG. 4) (not shown). A permanent magnet may be applied as the main magnet 11 described above. In this case, the static magnetic field power supply 12 is not necessary.

  The gradient magnetic field generator 2 includes a gradient magnetic field coil 21 and a gradient magnetic field power supply 22. The gradient coil 21 is formed by combining three sets of coils corresponding to the X-axis direction, the Y-axis direction, and the Z-axis direction that are orthogonal to each other. The gradient magnetic field power supply 22 supplies a pulse current to each of the three sets of coils included in the gradient magnetic field coil 21. With such a configuration, the gradient magnetic field generation unit 2 superimposes a gradient magnetic field whose magnetic field strength changes in each of the X-axis direction, the Y-axis direction, and the Z-axis direction on the static magnetic field. Note that the gradient magnetic field power supply 22 encodes the imaging field based on the sequence control signal supplied from the control unit 9. That is, the gradient magnetic field power supply 22 individually adjusts the distribution of the magnetic field strength in each axial direction by controlling the pulse current supplied to the three sets of coils included in the gradient magnetic field coil 21 based on the sequence control signal. To do. Thereby, slice selection gradient magnetic field Gs, phase encoding gradient magnetic field Ge, and readout (frequency encoding) gradient magnetic field Gr orthogonal to each other are formed in desired directions, respectively.

  The transmission / reception unit 3 includes a transmission coil 31, a transmission unit 32, a reception coil 33 and a reception unit 34.

  The transmission coil 31 transmits an RF pulse into the imaging field by the RF pulse signal supplied from the transmission unit 32. Based on the sequence control signal supplied from the control unit 9, the transmission unit 32 modulates a carrier wave having the same frequency as the magnetic resonance frequency (Larmor frequency) determined by the static magnetic field strength of the main magnet 11 with a predetermined selective excitation waveform. An RF pulse current is generated. The reception coil 33 detects the MR signal generated in the subject 150 and sends it to the reception unit 34. As the receiving coil 33, in order to detect MR signals with high sensitivity, an array coil in which a plurality (N) of small-diameter coils are arranged is suitable. The reception unit 34 includes an amplification circuit, an intermediate frequency conversion circuit, a detection circuit, an analog-to-digital (A / D) converter, and a filtering circuit for N channels. The receiving unit 34 amplifies the MR signal detected by the receiving coil 33, and further performs A / D conversion after performing signal processing such as intermediate frequency conversion, phase detection, and filtering. The amplifying circuit is usually installed in the vicinity of the receiving coil 33 in order to amplify the MR signal detected by the receiving coil 33 with high S / N. However, a transmission / reception coil having the function of the transmission coil 31 and the function of the reception coil 33 in one coil may be used. In this case, the transmission / reception coil is connected to the transmission unit 32 and the reception unit 34 via a hybrid circuit or a transmission / reception switch.

The main magnet 11, the gradient magnetic field coil 21, the transmission coil 31, and the reception coil 33 are provided in the gantry of the MRI apparatus 200 in the same manner as in FIG. 4, and an imaging field is formed at the center of the gantry. That is, an imaging field in which the subject 150 is inserted together with the top 4 is provided at the center of the gantry, and around the imaging field, the reception coil 33, the transmission coil 31, the gradient magnetic field coil 21, and the main magnet 11 are Z-axis. Are arranged concentrically with the axis as the axis.

  The top plate 4 is slidably attached in the Z-axis direction on the upper surface of a bed main body (not shown) installed in the vicinity of the gantry. The longitudinal direction of the top plate 4 substantially coincides with the Z-axis direction. In addition, the subject 150 is placed on the top plate 4 in a state in which the body axis substantially coincides with the longitudinal direction of the top plate 4. By moving the top 4, an arbitrary imaging target site in the subject 150 placed on the top 4 is positioned in the imaging field. In this case, the imaging target part located in the imaging field faces the receiving coil 33.

  The movement mechanism part 5 is attached to the above-mentioned bed, for example. The movement mechanism unit 5 includes a movement mechanism 51 and a drive signal generation unit 52. The moving mechanism 51 includes a motor 51a and moves the top plate 4 at a predetermined speed in the Z-axis direction. The drive signal generation unit 52 generates a drive signal for driving the motor 51a based on the movement trigger signal (movement start trigger signal and movement stop trigger signal) supplied from the control unit 9.

  The image data generation unit 6 includes a storage unit 61 and a high speed calculation unit 62. Storage unit 61 further includes an MR signal storage unit 611 and an image data storage unit 612. The MR signal storage unit 611 stores MR signals for N channels subjected to A / D conversion by the receiving unit 34. The MR signal storage unit 611 sequentially stores MR signals that are repeatedly received while moving the subject 150. The MR signal storage unit 611 stores the imaging position information supplied from the control unit 9 as supplementary information in association with these MR signals. The image data storage unit 612 stores image data obtained by reconstruction processing based on the above-described MR signal and its imaging position information. The high-speed computing unit 62 reads the MR signal and imaging position information stored in the MR signal storage unit 611, performs reconstruction processing by two-dimensional Fourier transform, and generates image data. The high-speed computing unit 62 has a function of generating image data relating to a wider area than the imaging field based on MR signals obtained for different imaging target regions.

  The display unit 7 includes a display data generation circuit, a conversion circuit, and a monitor. The display data generation circuit generates display data by combining image data stored in the image data storage unit 612 and incidental information such as subject information supplied from the input unit 8 via the control unit 9. The conversion circuit converts display data into a predetermined display format, and further performs D / A (digital-to-analog) conversion and television format conversion to generate a video signal. The monitor displays the video represented by the video signal. As the monitor, an existing display device such as a CRT (cathode-ray tube) or a liquid crystal panel can be applied.

  The input unit 8 includes various input devices such as switches, a keyboard, or a mouse, and a display panel on the console. The input unit 8 inputs subject information, sets MR signal acquisition conditions and image data display conditions, sets the moving speed of the top 4, and inputs various command signals.

  The control unit 9 includes a main control unit 91, a sequence control unit 92, and a movement control unit 93. The main control unit 91 includes a CPU and a storage circuit. The main control unit 91 has a function of controlling the MRI apparatus 200 in an integrated manner. The storage circuit included in the main control unit 91 stores information such as object information input or set by the input unit 8, MR signal acquisition conditions, image data display conditions, or moving speed. The CPU included in the main control unit 91 generates pulse sequence information based on the above-described information input from the input unit 8 and supplies the pulse sequence information to the sequence control unit 92. The sequence information is information relating to, for example, the magnitude of the pulse current supplied to the gradient magnetic field coil 21 and the transmission coil 31, the supply time, and the supply timing. The sequence control unit 92 includes a CPU and a storage circuit. The storage circuit included in the sequence control unit 92 stores the pulse sequence information supplied from the main control unit 91. The CPU included in the sequence control unit 92 generates a sequence control signal according to the pulse sequence information, and thereby controls the gradient magnetic field power source 22 and the transmission unit 32. The movement control unit 93 generates a movement start trigger signal and a movement stop trigger signal related to the movement of the top 4 based on the pulse sequence information supplied from the main control unit 91 or the sequence control signal supplied from the sequence control unit 92. , Supplied to the moving mechanism unit 5. For example, the movement control unit 93 generates the above-described movement stop trigger signal and movement start trigger signal based on the MR signal collection start time and collection end time set by the sequence control unit 92.

Next, the operation of the MRI apparatus 200 configured as described above will be described with reference to FIG . FIG. 2 is a time chart for explaining the relationship between the MR signal acquisition period and the drive signal generation period in the MRI apparatus 200. Here, for the sake of simplicity, the case of single slice imaging will be described, but multi-slice imaging and oblique imaging can be similarly performed.

  The gradient magnetic field power supply 22 controls the pulse current for each coil in the X axis direction, the Y axis direction, and the Z axis direction in the gradient magnetic field coil 21 based on the sequence control signal supplied from the sequence control unit 92. As a result, the slice selective gradient magnetic field Gs for setting the imaging slice plane, the phase encoding gradient magnetic field Ge for encoding the generation position of the MR signal obtained from the imaging slice plane, and readout (frequency encoding). A gradient magnetic field Gr is applied to the imaging field.

  For example, when generating Na × Na image data, the application of the phase encoding gradient magnetic field Ge having Na kinds of magnetic field strengths is repeated Na times in the repetition period TR, and reading with a predetermined magnetic field strength (frequency encoding) is performed. The application of the gradient magnetic field Gr is repeated in the repetition period TR.

  The transmitter 32 supplies an RF pulse current to the transmitter coil 31 and transmits a 90-degree RF pulse during application of the first slice selection gradient magnetic field Gs. The 90-degree RF pulse is applied to a portion of the subject 150 located in the imaging field. The transmission unit 32 supplies the RF pulse current to the transmission coil 31 and transmits the 180 degree RF pulse during the application of the second slice selective gradient magnetic field Gs after the time TE / 2 from the transmission of the 90 degree RF pulse. To do. This 180 degree RF pulse is irradiated to the same site as the 90 degree RF pulse. The reception coil 33 and the reception unit 34 receive MR signals generated from the subject 150 after time TE / 2 from the irradiation of the 180-degree RF pulse.

  Then, if Na MR signals are acquired by updating the magnetic field strength of the phase encoding gradient magnetic field Ge Na times, the high-speed arithmetic unit 62 obtains Na MR signals each having Na data points. Two-dimensional Fourier transform is performed to generate image data of Na × Na pixels.

Each change of the RF pulse, the slice selection gradient magnetic field Gs, the phase encoding gradient magnetic field Ge, and the readout gradient magnetic field Gr shown in FIG. 2 is in accordance with a pulse sequence of a normal SE method. The MR signal shown in FIG. 2 schematically shows the MR signal generated in the subject 150 under the pulse sequence. Note that the 90-degree RF pulse and the 180-degree RF pulse in FIG. 2 are RF waves for supplying energy necessary to change the nuclear spin of the subject tissue by 90 degrees and 180 degrees to the nuclear spin. Time TE is the time from the irradiation of the 90-degree RF pulse until the MR signal is detected. Time TR is an MR signal detection cycle.

The movement control unit 93 generates the movement start trigger signal Ps1 at time t10. Note that the time t10 is a time before the application of the 90-degree RF pulse to the subject 150 and the application of the slice selection gradient magnetic field Gs (for example, the time when the previous acquisition of the MR signal is completed). In the movement mechanism unit 5, when the movement start trigger signal Ps1 is generated, generation of the drive signal by the drive signal generation unit 52 is started. When this drive signal is supplied to the motor 51a, the top plate 4 is moved in the Z-axis direction at a predetermined speed by the moving mechanism 51. When the supply is made in this way drive signals, electromagnetic noise is generated due to the drive signal as shown in FIG.

  Next, in a period T1 including time t11 after time t10, the slice selection gradient magnetic field Gs is applied to the imaging field, and a 90-degree RF pulse is transmitted. In a period T2 including a time t12 after the time t11, the phase encoding gradient magnetic field Ge and the frequency encoding gradient magnetic field Gr are applied to the imaging field.

  In a period T3 including time 13 when the time TE / 2 has elapsed from time t11, the slice selection gradient magnetic field Gs is applied again to the imaging field and a 180-degree RF pulse is transmitted. In a period T4 including time t14 when time TE / 2 has elapsed from time t13, the readout gradient magnetic field Gr is applied again and MR signals are collected.

  Now, when MR signals are collected by such a sequence, the movement control unit 93 generates the movement stop trigger signal Pe1 at time ts1 when application of the read gradient magnetic field Gr is started in the period T4. In the movement mechanism unit 5, when the movement stop trigger signal Pe1 is generated, the drive signal generation by the drive signal generation unit 52 is stopped. Thus, the supply of the drive signal to the motor 51a is stopped. Thereafter, the movement control unit 93 generates the movement start trigger signal Ps2 at the time Te2 when the application of the read gradient magnetic field Gr in the period T4 is stopped. Therefore, in the movement mechanism unit 5, the generation of the drive signal by the drive signal generation unit 52 is resumed in response to the generation of the movement start trigger signal Ps2.

  The MRI apparatus 200 sequentially collects MR signals emitted from each part while changing the part of the subject 150 located in the imaging field by repeatedly performing the above-described operation. Then, the high-speed calculation unit 62 reconstructs image data representing an image obtained by imaging the subject 150 with respect to an area wider than the imaging field, based on the MR signals collected in this way.

Thus, the supply of the drive signal to the motor 51a is stopped during the period in which the read gradient magnetic field Gr is applied in the period T4. Therefore, electromagnetic noise due to the drive signal does not occur when collecting MR signals as shown in FIG . Therefore, mixing of the electromagnetic noise into the MR signal can be prevented. For this reason, it is possible to generate image data with few artifacts and excellent S / N.

  Since the period T4 is usually around 10 msec, the period in which the movement of the top 4 is stopped by stopping the supply of the drive signal is extremely short. Therefore, there is almost no discomfort to the subject 150 due to the stop of the movement of the top 4. Furthermore, when inertia occurs in the moving mechanism 51, the top plate 4 can be continuously moved even during a period in which the supply of the drive signal is stopped.

  Further, according to the present embodiment, electromagnetic noise that may be mixed into the MR signal is not generated, so that the above-described electromagnetic wave is also used in an MRI apparatus in which the length of the imaging field in the gantry is shortened or the aperture is widened. Imaging that is not affected by noise becomes possible.

  This embodiment can be variously modified as follows.

  The noise of the MR signal is greatly affected by the electromagnetic noise caused by the drive signal as described above, but also the noise generated by another electric circuit such as a logic circuit mounted on the display unit 7 or the input unit 8 is also affected. There is. Therefore, even if the operation of the electric circuit serving as the noise source is stopped in the same manner as the drive signal, the mixing of noise into the MR signal can be reduced.

  As the receiving coil 33, a single coil may be applied instead of the array coil. In this case, the receiving sensitivity is deteriorated as compared with the above embodiment, but the receiving coil 33 and the receiving unit 34 can be configured easily.

Instead of the reception coil 33, for example, as shown in FIG. 3, a reception coil 33 b fixed to the top plate 4 so as to surround the entire imaging target region of the subject 150 may be used. In this case, the receiving coil 33b continuously moves in the imaging field 130b of the gantry 120b together with the top 4 to receive MR signals from a wide range of the subject 150, thereby realizing wide range imaging. As the receiving coil 33b, an array coil is usually employed, but a single coil may be employed.

  The top plate 4 may be moved stepwise at a predetermined interval. In this case, a wide range of image data may be generated by generating image data at each of a plurality of preset imaging positions and further combining these image data.

  In the above embodiment, as a method of generating image data when performing wide-range imaging while continuously moving the subject 150, the specific cross section of the subject 150 enters the imageable region and exits. By changing the frequency of the RF pulse in accordance with the change in the position of the specific cross section that moves continuously, the same cross section of the subject 150 is tracked and repeatedly excited while moving the subject 150, and 1 is extracted from the cross section. It is preferable to use a method of collecting all echoes necessary for reconstruction of a single image or a method described in US Pat. No. 7,110,805, which is incorporated herein. However, other methods can be applied. For example, in the former method, the frequency of the RF pulse may not be changed in accordance with the change in the position of the specific cross section that moves continuously.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 is a block diagram showing the overall configuration of an MRI apparatus in an embodiment of the present invention. The figure for demonstrating the relationship between the collection period of MR signal in the MRI apparatus shown in FIG. 1, and the production | generation period of a drive signal. The figure which shows other embodiment. The figure which shows typically the coil part provided in the gantry of the conventional MRI apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Static magnetic field generation part, 2 ... Gradient magnetic field generation part, 3 ... Transmission / reception part, 4 ... Top plate, 5 ... Moving mechanism part, 6 ... Image data generation part, 7 ... Display part, 8 ... Input part, 9 ... Control 91: main control unit, 92 ... sequence control unit, 93 ... movement control unit, 11 ... main magnet, 12 ... static magnetic field power source, 21 ... gradient magnetic field coil, 22 ... gradient magnetic field power source, 31 ... transmission coil, 32 ... Transmission unit 33... Reception coil 33 b reception coil 34 reception unit 51 moving mechanism 51 a motor 52 drive signal generation unit 61 storage unit 611 signal storage unit 612 image data storage , 62... High-speed computing unit, 120 b. Gantry, 130 b. Imaging field, 200. Magnetic resonance imaging apparatus (MRI apparatus).

Claims (13)

Irradiate an RF pulse to a subject placed on a top plate that moves in an imaging field where a static magnetic field and a gradient magnetic field are formed,
Collecting magnetic resonance signals generated in the subject by irradiation of the RF pulse while continuously moving the top plate;
Generating image data based on the collected magnetic resonance signals;
A magnetic resonance imaging apparatus characterized in that generation of a drive signal for moving the top plate is stopped during the collection period of the magnetic resonance signal. A magnetic field forming unit for forming a static magnetic field and a gradient magnetic field in a magnetic resonance imaging field;
A top plate on which the subject is placed;
A top plate moving unit for moving the top plate;
A transmitter / receiver that irradiates an RF pulse to an imaging target site of the subject located in the imaging field and receives a magnetic resonance signal generated from the imaging target site;
An image data generation unit that generates image data based on the magnetic resonance signal;
While the amount of the magnetic resonance signal necessary for the image data generator to generate the image data is received by the transmitter / receiver, the top plate is moved continuously or stepwise at predetermined intervals. A drive signal generating unit that generates a drive signal for driving the top plate moving unit, and includes a drive signal generating unit that stops generating the drive signal during a period of reception of the magnetic resonance signal by the transmitting / receiving unit. Resonance imaging device. The magnetic field forming unit forms a slice selection gradient magnetic field and a phase encoding gradient magnetic field included in the gradient magnetic field while the drive signal generation unit generates the drive signal, and the drive signal generation unit While stopping the generation of the drive signal, forming a readout gradient magnetic field included in the gradient magnetic field,
The transmission / reception unit irradiates the RF pulse while the drive signal generation unit generates the drive signal, and the magnetic resonance unit while the drive signal generation unit stops generating the drive signal. The magnetic resonance imaging apparatus according to claim 2, wherein the signal is received. The top plate moving unit moves the top plate in the body axis direction of the subject,
3. The transmission / reception unit irradiates an RF pulse to an imaging target site that changes as the subject moves, and receives a magnetic resonance signal generated from the imaging target site, respectively. Magnetic resonance imaging equipment.   3. The MRI according to claim 2, wherein the top plate moving unit stops the movement of the top plate by stopping the generation of the drive signal during the reception period of the magnetic resonance signal by the transmitting / receiving unit. apparatus.   The image data generation unit generates image data relating to a wide range including the plurality of imaging target parts based on magnetic resonance signals respectively obtained from the imaging target parts that change as the subject moves. The magnetic resonance imaging apparatus according to claim 2. A trigger signal generating unit that generates a movement start trigger signal and a movement stop trigger signal of the top plate based on information on application start timing and application end timing of the gradient magnetic field;
The magnetic resonance imaging apparatus according to claim 2, wherein the drive signal generation unit sets a period during which the generation of the drive signal is stopped based on the movement start trigger signal and the movement stop trigger signal. The trigger signal generation unit generates the movement start trigger signal and the movement stop trigger signal based on information on an application start timing and an application end timing of a read gradient magnetic field applied when the magnetic resonance signal is received among the gradient magnetic fields. The magnetic resonance imaging apparatus according to claim 7 , wherein the magnetic resonance imaging apparatus generates the magnetic resonance imaging apparatus. An application unit that applies a gradient magnetic field and a high-frequency pulse to the subject to generate a magnetic resonance signal from the subject in a static magnetic field;
A high frequency coil for detecting the pre Ki磁 air resonance signal,
A data collection unit for collecting the magnetic resonance signals detected by the high-frequency coil;
A reconstruction unit for reconstructing a magnetic resonance image based on the magnetic resonance signals collected by the data collection unit;
During a period in which the data collection unit collects the magnetic resonance signal, a driving signal for driving the top plate is temporarily moved while continuously sliding a top plate for placing a subject in the longitudinal direction. A bed that is turned off
A magnetic resonance imaging apparatus comprising: a control unit that controls the application unit and the data collection unit so as to collect the magnetic resonance signal while the drive signal is OFF. The controller is
While the drive signal is ON, controlling the application unit to apply the slice selection gradient magnetic field and the phase encoding gradient magnetic field included in the gradient magnetic field, and the high-frequency pulse,
The magnetic resonance imaging apparatus according to claim 9 , wherein the application unit is controlled to apply a readout gradient magnetic field included in the gradient magnetic field while the drive signal is OFF. An application unit that applies a gradient magnetic field and a high-frequency pulse to the subject to generate a magnetic resonance signal from the subject in a static magnetic field;
A bed for sliding a top plate for placing the subject in the longitudinal direction;
A high-frequency coil for detecting the magnetic resonance signal;
A data collection unit for collecting the magnetic resonance signals detected by the high-frequency coil;
A reconstruction unit for reconstructing a magnetic resonance image based on the magnetic resonance signals collected by the data collection unit;
The application unit, the bed, and the data collection unit are controlled to collect the magnetic resonance signal while sliding the top plate, and the bed collects the magnetic resonance signal by the data collection unit. The magnetic resonance imaging apparatus further comprises a control unit that controls so as not to generate a drive signal for driving the top plate. The control unit applies a slice selection gradient magnetic field and a phase encoding gradient magnetic field included in the gradient magnetic field, generates the drive signal during a period during which the high-frequency pulse is applied, and reads out a read gradient included in the gradient magnetic field. The magnetic resonance according to claim 11 , wherein the application unit, the bed, and the data collection unit are controlled so that the drive signal is not generated during a period in which the magnetic resonance signal is collected by applying a magnetic field. Imaging device. While the prior SL drive signal is generated, together form a slice selection gradient magnetic field and a phase encode gradient magnetic field contained in the gradient magnetic field, irradiating the RF pulse,
The magnetic resonance imaging apparatus according to claim 1, wherein a read gradient magnetic field included in the gradient magnetic field is applied while generation of the drive signal is stopped.

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