WO2015093296A1 - 磁気共鳴イメージング装置およびその制御方法 - Google Patents
磁気共鳴イメージング装置およびその制御方法 Download PDFInfo
- Publication number
- WO2015093296A1 WO2015093296A1 PCT/JP2014/082057 JP2014082057W WO2015093296A1 WO 2015093296 A1 WO2015093296 A1 WO 2015093296A1 JP 2014082057 W JP2014082057 W JP 2014082057W WO 2015093296 A1 WO2015093296 A1 WO 2015093296A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- sar
- biological information
- predicted value
- magnetic resonance
- magnetic field
- Prior art date
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/288—Provisions within MR facilities for enhancing safety during MR, e.g. reduction of the specific absorption rate [SAR], detection of ferromagnetic objects in the scanner room
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
- G01R33/48—NMR imaging systems
- G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
- G01R33/56—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution
- G01R33/567—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution gated by physiological signals, i.e. synchronization of acquired MR data with periodical motion of an object of interest, e.g. monitoring or triggering system for cardiac or respiratory gating
- G01R33/5673—Gating or triggering based on a physiological signal other than an MR signal, e.g. ECG gating or motion monitoring using optical systems for monitoring the motion of a fiducial marker
Definitions
- the present invention relates to a magnetic resonance imaging (hereinafter referred to as MRI) apparatus.
- MRI magnetic resonance imaging
- An MRI apparatus measures a nuclear magnetic resonance (hereinafter referred to as NMR) signal generated by a nuclear spin of an object, particularly an atom constituting a human tissue, for example, a hydrogen atom, for example, a head, abdomen, limb, etc.
- NMR nuclear magnetic resonance
- This is an apparatus for imaging two-dimensionally or three-dimensionally.
- the NMR signal is given different phase encoding depending on the gradient magnetic field and is frequency-encoded and measured as time-series data.
- the measured NMR signal is reconstructed into an image by two-dimensional or three-dimensional Fourier transform.
- the whole body SAR is obtained by dividing the energy W of the electromagnetic wave absorbed by the whole body of the subject by the mass M of the subject, and the body part SAR is the energy of the electromagnetic wave absorbed by a desired part of the subject.
- W p is divided by the mass M p of the desired part of the subject, and the local SAR is energy per unit time absorbed by an arbitrary 10 g.
- Patent Document 1 describes changing parameters so as not to exceed the SAR limit especially for multiple scans.
- Patent Document 2 describes SAR prediction of scan and prediction of multiple scans.
- Patent Document 1 and Patent Document 2 describe SAR prediction, but do not mention SAR prediction or imaging control when biological information changes. That is, the patent document does not consider changes in biological information and does not mention the necessity of consideration.
- the subject 11 can be not only a relatively healthy person but also people with various diseases. Of course, it is desirable to consider the case where a person with a severe medical condition has a higher need for examination than a healthy person and the subject has a serious disease. In a subject with a serious disease, biological information can often be suddenly disturbed.
- An object of the present invention is to provide an MRI apparatus capable of suppressing interruption of imaging due to an actual measurement value of SAR exceeding a limit value.
- the magnetic resonance imaging apparatus of the present invention includes a static magnetic field generator that generates a static magnetic field in a space that accommodates a subject, a gradient magnetic field generator that generates a gradient magnetic field superimposed on the static magnetic field, and irradiates the subject
- a high-frequency magnetic field generating unit for generating a high-frequency magnetic field a sequencer for controlling the generation of the gradient magnetic field and the generation of the high-frequency magnetic field according to a pulse sequence, a signal detection unit for detecting a nuclear magnetic resonance signal, and a predicted value of SAR
- a biological information receiver (90) that receives biological information, and the sequencer controls the generation of the gradient magnetic field and the generation of the high-frequency magnetic field in synchronization with the biological information
- the control unit calculates a predicted value of SAR based on a cycle length of the biological information to determine whether the predicted value of SAR exceeds a limit value, and the predicted value of SAR is the limit value The value Based on the determination by the control unit that it does not exceed, the generation
- the block diagram which shows the structure of the MRI apparatus which is one Embodiment of this invention The flowchart which shows the outline
- Time table showing SAR prediction calculation and actual measurement SAR measurement operation in the flowchart shown in FIG. The flowchart which shows operation
- the time table of a method for performing SAR prediction from the previous cycle of biological information which is still another embodiment of the present invention
- the time table of a method for performing SAR prediction from past changes in biological information which is still another embodiment of the present invention
- the time table which shows correspondence when the SAR predicted value exceeds the limit value which is still another embodiment of the present invention
- FIG. 11 is an explanatory diagram showing the display contents displayed on the display in the flowchart shown in FIG. Time table showing a method of automatically skipping application by a pulse sequence when the predicted SAR value exceeds a limit value, which is still another embodiment of the present invention.
- FIG. 14 is an explanatory diagram showing display contents displayed on the display in the flowchart shown in FIG.
- 16 is a flowchart showing the operation of the control unit in the time table shown in FIG.
- FIG. 17 is an explanatory diagram showing display contents displayed on the display in the flowchart shown in FIG.
- FIG. 1 is a block diagram showing the overall configuration of an embodiment of an MRI apparatus to which the present invention is applied.
- This MRI apparatus obtains a tomographic image of a subject using an NMR phenomenon.
- the MRI apparatus 10 includes a static magnetic field generator that generates a static magnetic field in a static magnetic field space 20 indicated by a dotted frame, a gradient magnetic field generator 30 that generates a gradient magnetic field, a sequencer 40, a high frequency A magnetic field generation unit 50, a signal detection unit 60, a processing unit 70, an operation unit 80, and a biological information reception unit 90 are provided.
- the static magnetic field generator is not shown.
- the subject 11 In the static magnetic field space 20, the subject 11 is placed inside, in the direction perpendicular to the body axis of the subject 11 in the case of the vertical magnetic field method, in the body axis direction of the subject 11 in the case of the horizontal magnetic field method, A uniform static magnetic field is generated.
- a permanent magnet type, normal conducting type or superconducting type static magnetic field generating source is arranged around the subject 11.
- the gradient magnetic field generating unit 30 is a gradient magnetic field coil that superimposes the static magnetic field in the static magnetic field space 20 and generates a gradient magnetic field in the three axis directions of X, Y, and Z that are the coordinate system (static coordinate system) of the MRI apparatus 10 31 and a gradient magnetic field power source 32 for driving each gradient coil.
- gradient magnetic fields G x , G y , and G z are generated in the three axis directions of X, Y, and Z.
- a slice direction gradient magnetic field pulse (G s ) is applied in a direction orthogonal to the slice plane (imaging cross section) to set a slice plane for the subject 11, and the remaining planes orthogonal to the slice plane and orthogonal to each other are set.
- a phase encoding direction gradient magnetic field pulse (G p ) and a frequency encoding direction gradient magnetic field pulse (G f ) are applied in two directions, and position information in each direction is encoded in the echo signal.
- the sequencer 40 repeatedly applies a control signal according to a predetermined pulse sequence of a high-frequency magnetic field pulse (hereinafter referred to as RF pulse) and a gradient magnetic field pulse.
- the sequencer 40 operates under the control of a central processing unit (hereinafter referred to as CPU) 71, and various commands necessary for collecting tomographic image data of the subject 11 are supplied to the gradient magnetic field generator 30, the high frequency magnetic field generator 50, The signal is sent to the signal detector 60.
- CPU central processing unit
- the CPU 71 operates as a control unit that controls the operation of the MRI apparatus 10.
- the control unit may be configured by one CPU 71 or may be configured by a plurality of processing devices (CPUs) that divide and share necessary functions.
- the control unit performs not only control but also arithmetic processing.
- the biological information 92 is received from the biological information receiving unit 90 described below, and the sequencer 40 is controlled so that a pulse sequence is performed in synchronization with the biological information 92.
- the high-frequency magnetic field generator 50 irradiates the subject 11 with an RF pulse in order to cause nuclear magnetic resonance to occur in the nuclear spins of the atoms constituting the living tissue of the subject 11.
- the high-frequency magnetic field generator 50 includes a high-frequency oscillator 51, a modulator 52, a high-frequency amplifier 53, and a transmission coil 54 that is a high-frequency coil on the transmission side.
- the RF pulse output from the high-frequency oscillator 51 is amplitude-modulated by the modulator 52 at a timing according to a command from the sequencer 40, and the amplitude-modulated RF pulse is amplified by the high-frequency amplifier 53 and then placed close to the subject 11.
- the transmission coil 54 By supplying to the transmission coil 54, the subject 11 is irradiated with electromagnetic waves.
- the signal detector 60 detects an echo signal (hereinafter referred to as an NMR signal) emitted by nuclear magnetic resonance of atomic nuclear spins constituting the biological tissue of the subject 11.
- the signal detection unit 60 includes a reception coil 64 that is a high frequency coil on the reception side, a signal amplifier 63, a quadrature phase detector 62, an A / D converter 61, and a SAR calculation unit 65.
- the NMR signal of the response of the subject 11 induced by the electromagnetic wave irradiated from the transmission coil 54 is detected by the reception coil 64 arranged close to the subject 11, amplified by the signal amplifier 63, and then from the sequencer 40.
- the amount of absorption of the electromagnetic wave irradiated from the transmission coil 54 into the subject 11 is calculated by the SAR calculation unit 65.
- the SAR calculated by the SAR calculation unit 65 is sent to the CPU 71, compared with the SAR restriction, and the comparison result is recorded in the memory 72, for example.
- the processing unit 70 performs various data processing, processing result display and storage, and the like.
- the processing unit 70 includes a processor such as a CPU 71, a storage device such as a memory 72, an external storage device having a storage function such as an optical disk or a magnetic disk 73, and a display 74 having a display function such as a liquid crystal display (LCD). Is included.
- the CPU 71 executes processing such as signal processing and image reconstruction using the memory 72 as a work area, and a tomographic image of the subject 11 as a result is displayed on the display 74. The information is displayed and recorded on the magnetic disk 73 of the external storage device.
- the operation unit 80 inputs various control information of the MRI apparatus 10 and control information of processing performed by the processing unit 70.
- the operation unit 80 includes, for example, a pointing device 81 such as a trackball or a mouse or a pad, and a keyboard 82.
- the operation unit 80 is disposed in the vicinity of the display 74, and an operator can interactively instruct the MRI apparatus 10 to execute various processes through the operation unit 80 while looking at the display 74.
- the pointing device 81 may have a touch panel as one of the input devices, and the touch panel may be provided on the display surface of the display 74. Thus, by providing input means such as a touch panel on the display surface of the display 74, an input operation can be performed corresponding to the display image on the display 74.
- the biological information receiving unit 90 receives the biological information of the subject 11, converts the received signal into a digital quantity, and sends it to the CPU 71.
- the CPU 71 calculates, for example, the phase of the pulse of biological information, sends an instruction to the sequencer 40 to repeatedly apply for each phase, and the biological sequence from the sequencer 40 to the gradient magnetic field power source 32, the modulator 52, and the A / D converter 61
- a control command corresponding to the phase of information is sent, and an RF pulse is applied to the subject 11 corresponding to the phase of the biological information.
- An NMR signal generated based on the application of the RF pulse is detected corresponding to the phase of the biological information.
- the transmission coil 54 and the gradient magnetic field coil 31 are opposed to the subject 11 in the static magnetic field space in which the subject 11 is accommodated if the vertical magnetic field method is used, and in the horizontal magnetic field method. It is installed so as to surround the sample 11. Further, the receiving coil 64 is installed so as to face or surround the subject 11.
- the radionuclide to be imaged by the MRI apparatus 10 is a hydrogen nucleus (proton) that is a main constituent material of the subject 11 as widely used in clinical practice.
- proton a hydrogen nucleus
- the spatial distribution of proton density and the spatial distribution of the relaxation time of the excited state a part of the human head, abdomen, limbs, etc., such as form or function, is imaged two-dimensionally or three-dimensionally.
- FIG. 2 is a flowchart for explaining the processing operation for imaging by the CPU 71.
- the CPU 71 repeatedly detects the biological information 92 via the biological information receiving unit 90, and uses the detected biological information 92.
- the predicted SAR value 270 under the imaging conditions set in the above is calculated.
- the CPU 71 confirms that the calculated predicted SAR value 270 is within the limit range, and the imaging operation is started.
- the CPU 71 performs control for imaging the subject 11.
- the biological information 92 of the subject 11 is different from information such as scanogram information and weight of the subject 11 and has attributes that change greatly in a short period of time, and the CPU 71 repeatedly detects the biological information 92 and detects it.
- the SAR predicted value 270 is repeatedly calculated, and it is monitored whether the calculated SAR predicted value 270 is a limit value.
- the measured SAR value 67 is measured via the SAR calculator 65, and it is monitored whether the measured SAR value 67 exceeds the limit value.
- the MRI image of the subject 11 using the MRI apparatus 10 is taken by the imaging operation starting in step S200.
- the subject 11 is set on the MRI apparatus 10 (step S202). Specifically, the subject 11 is placed and fixed on the top plate of the bed 13 shown in FIG. In addition, other necessary work is performed.
- the CPU 71 performs a process for predicting the SAR in accordance with a control program stored in advance in a storage device such as a server, and a process for capturing an MRI image in accordance with the set imaging conditions and storing the MRI image in a storage device such as the magnetic disk 73. Is started (step S210).
- Step S250 and the like are described as a series of continuous processing flows for convenience of explanation.
- the CPU 71 does not execute a series of continuous programs, but the flow starting from step S210 shown in FIG. 2 is divided into a plurality of application programs for each function. Each is executed separately under execution conditions suitable for the processing function.
- Each application program is activated and executed by a management program such as an operating system under predetermined execution conditions. For example, one application program is repeatedly executed at a short period, another application program is executed in conjunction with the execution of a specific application program having a special relationship, or another application program is operated by an operator. Is executed as an event linked to a specific event. Since it becomes very complicated to describe the execution conditions and activation states of each individual application program, the termination process accompanying the termination of execution, etc., the overall processing result of each application program that operates as described above, This is described as a one-line flowchart showing the processing contents of the CPU 71 started in step S210 shown in FIG.
- the CPU 71 displays an input screen for inputting personal data or biological information 92 as subject information on the display 74 (step S212), and the personal data or biological information 92 as subject information according to the display content displayed by the CPU 71.
- the subject information includes personal data such as age, height, and weight, and biological information such as heart rate, pulse wave, and electrocardiographic waveform.
- the personal data and the biological information 92 are input by different steps.
- the advantage of inputting personal data and biometric information separately as in this embodiment is that the input method is different.
- Personal data has a property that does not change in a short period of time, and the value of personal data does not change during imaging.
- the biological information 92 is information that may change in a short time, and is information that is preferably captured immediately before the information is used for calculation or the like, and the importance of the capture timing is different.
- the biometric information 92 is desirably captured immediately before use as much as possible.
- a detection unit that detects biometric information is provided, such as the biometric information receiving unit 90 shown in FIG.
- the biometric information receiving unit 90 is used.
- the biological information 92 has an attribute that changes in a short time, and it is desirable to capture it as close as possible to use.
- the subject 11 often has a health hazard, and the biological information 92 is more likely to change suddenly than a healthy person. For this reason, it is desirable to measure immediately before biometric information 92 is required.
- the CPU 71 captures and stores the biological information 92 such as heart rate, pulse wave, and electrocardiogram via the biological information receiving unit 90 in step S216 as an example.
- the biological information 92 such as heart rate, pulse wave, and electrocardiogram
- the CPU 71 captures and stores the biological information 92 such as heart rate, pulse wave, and electrocardiogram via the biological information receiving unit 90 in step S216 as an example.
- the biological information 92 such as heart rate, pulse wave, and electrocardiogram via the biological information receiving unit 90 in step S216 as an example.
- a scanogram which is an image for determining the imaging position, is captured and stored in step S220.
- the scanogram is imaged in step S222 and stored in a storage device such as the magnetic disk 73.
- the output of the RF pulse is small compared to the MRI imaging performed below, but since the RF pulse is actually emitted from the transmission coil 54, the SAR value based on the actual irradiation of this RF pulse is calculated. It can be obtained from the SAR calculator 65 as a monitor.
- the obtained SAR value is based on the actually irradiated RF pulse, and can be measured as an actual measurement value when the subject 11 is actually irradiated with the RF pulse.
- SAR depends on the mass of the individual's measurement site, and there are individual differences in the absorption state of the RF pulse. Monitoring the measured values of SAR in advance for MRI image acquisition is a prediction of SAR. Very useful in improving accuracy.
- Step S250 shows the outline of the operation of the MRI apparatus 10 related to the imaging of the MRI image of the subject 11, and particularly shows the outline of the processing related to the SAR using the biological information 92.
- FIG. 4 shows an example of a specific processing procedure of step S270 in step S250.
- step S252 in accordance with the input screen from the CPU 71 and a display suggesting the input of imaging conditions, the imaging conditions for the region to be imaged are input or the imaging conditions that have already been set are changed.
- the imaging conditions are determined based on the body type of the subject 11 and the examination content.
- step S254 based on the input or changed imaging condition, the SAR prediction calculation is performed by the CPU 71, and the calculation result is stored. Further, in step S256, it is determined whether or not the calculated predicted SAR value satisfies the limiting condition, that is, whether or not the calculated predicted SAR value is within the limited range. If the restriction condition is not satisfied, that is, outside the restriction range, the process returns to step S252 again, and the imaging condition is reset, that is, the imaging condition is changed.
- step S254 the prediction calculation processing performed by the SAR CPU 71 using the personal data or biological information as the subject information is performed based on (Expression 4) to (Expression 6).
- W is the SAR absorption rate, and is, for example, a statistical average value of the SAR absorption rate when each part of the subject 11 is irradiated with an RF pulse.
- PowerSeq (W) represents the irradiation power of the RF pulse in the pulse sequence, and is a value calculated by the processing unit 70 on the energy (W) of the RF pulse irradiated by the transmission coil 54 based on the imaging parameter.
- the whole body SAR defined by (Equation 4) is the electromagnetic wave energy (W) absorbed by the whole body of the subject 11 due to the electromagnetic wave energy of the RF pulse, the subject mass (weight of the subject 11) M (kg) The number divided by. (5) by the A body part SAR defined, multiplied by the subject weight M (kg) systemically SAR (W / kg), the body of the partial mass m p of the subject 11 in the radiation range (kg) Divided number.
- the head SAR defined by (Equation 6) is the total body SAR (W / kg) multiplied by the subject mass M (kg) divided by the head mass m h (kg) of the subject 11, and the head is a numerical value obtained by multiplying the SAR absorption rate R h parts.
- step S256 When it is determined in step S256 that the predicted calculation value of SAR satisfies the SAR limit value, and when an operation for starting imaging is performed in step S260, the execution of CPU 71 is performed from step S260 to step S270. Then, step S270 is executed.
- step S270 the biological information 92 from the subject 11 is sent to the CPU 71 via the biological information receiving unit 90, and the CPU 71 sends a control signal for controlling the operation of the sequencer 40 in synchronization with the sent biological information. Send to sequencer 40.
- the sequencer 40 is controlled by a control signal from the CPU 71 so that the operation of the sequencer 40 is started in synchronization with the biological information 92.
- a control signal for executing a pulse sequence according to the coefficient value of the coefficient circuit is transmitted to a predetermined control destination.
- the control signal for executing the pulse sequence is synchronized with the biological information 92 by, for example, starting the coefficient operation of the coefficient circuit based on the control signal supplied from the CPU 71 to the sequencer 40 in synchronization with the biological information 92, for example. Can occur.
- the sequencer 40 performs an operation of applying a control signal synchronized with the biological information 92 to the gradient magnetic field power source 32, the modulator 52, and the A / D converter 61 (step S270).
- the A / D converter 61 takes in synchronization with the biological information 92. As described above, by synchronizing the operation of the sequencer 40 with the biological information, the operation based on the pulse sequence can be performed in synchronization with the biological information, and MRI imaging can be performed in synchronization with the biological information.
- step S270 monitoring of biological information 92 for capturing the latest biological information 92 (step S272), application of a control signal based on a pulse sequence synchronized with biological information 92 (step S274), and SAR based on biological information Prediction calculation (step S276) and actual SAR monitoring (step S278) are performed. It is determined whether or not the calculated predicted SAR value 270 and the actually measured SAR value 67 are within the SAR limits. Furthermore, the biological information 92 temporarily stored in the memory 72, the acquired diagnostic image, the calculated SAR predicted value 270, the actual measured value of the SAR, and the like are stored in the magnetic disk 19, and the collected biological information 92 is statistically processed. Is performed (step S270).
- step S280 after imaging of diagnostic images is completed, it is determined whether imaging of all diagnostic images is completed. For example, when a diagnostic image is captured under different conditions such as a different contrast or a different cross section, execution of the imaging operation of the CPU 71 transitions again to step S252, and setting of imaging conditions for new imaging is performed in step S252. Done in In this way, the above-described steps S252 to S280 are repeatedly executed.
- a series of examination operations is completed from step S290.
- FIG. 3 is a time table showing the operation state of step 270 related to the imaging of the diagnostic image in the flowchart of FIG.
- the calculation based on each of (Equation 4) to (Equation 6) is performed on the predicted SAR value 270 based on the personal data, scanogram measurement results, and biological information 92. Is called.
- the calculated SAR predicted value 270 is smaller than the SAR limit value
- imaging is started in step S260. Assume that the current position is in the current period P 0 . Imaging operation is performed in the current period P 0, found SAR value 67 of the current period P 0 is monitored, measured SAR values 67 of the current period P 0 is taken into the processor 70 from the SAR calculation unit 65 according to step S278 .
- the monitor value of the biological information 92 represents the output of the biological information receiving unit 90.
- the next cycle is the next cycle P 1
- the next cycle is the next cycle.
- a P 2 biometric information 92 and the actual measurement SAR value 67 of the next period P 1 and after another period P 2 is not actually present at this time. These are information to be measured in the future.
- the CPU 71 transmits a synchronization signal for synchronizing the operation of the sequencer 40 to the biological information to the sequencer 40. For example, to send the synchronization signal at a timing T0, it is further transmitted next period P 1 and after another period P 2, further in the next cycle, the synchronous signal timing T 1 and T 2, T 3, from CPU71 to the sequencer 40 The Thereafter, this operation is continued until the imaging is completed.
- the sequencer 40 Based on this synchronization signal, the sequencer 40 performs a sequence operation synchronized with the biological information 92, and transmits a control signal based on the sequence operation to the gradient magnetic field power source 32, the modulator 52, and the A / D converter 61.
- step S270 is a process that is specifically executed in step S270 shown in FIG. 2, a monitoring process of biological information 92 (step S272), an application process (step S274) based on a pulse sequence synchronized with biological information 92, a SAR prediction process ( Step S276) and the actual SAR monitor (step S278) are described as a time table in FIG. 3, and an example of the execution contents of the CPU 71 relating to step S270 is shown in FIG.
- the biometric information 92 of the current period P 0 is taken in step S302 described in FIG. 4, from the biometric information 92 or past the current period P 0 captured to date based of the processing result of the biometric information 92, the period of the biometric information 92 of the next period P 1 is calculated (step S272).
- step S276 the predicted SAR value 270 of the next period P 1 is calculated according to the calculated period of the biological information 92.
- the current cycle P 0 is the prediction calculation, further predicted computed SAR predicted value of the current period P 0 on the basis of the currently period P 0 270 is calculated.
- SAR predicted value 270 for the next period P 1 is the prediction calculation on the basis of the following period P 1 which is the prediction calculation.
- SAR prediction value 270 successive periods P 2 based on the cycle P 2 one after another is the prediction calculation is prediction calculation.
- the biological information 92 is captured in synchronization with the biological information 92, and the calculation of the value of the next biological information 92 and the calculation of the predicted SAR value 270 are performed based on the captured biological information 92.
- Such processing is performed in synchronization with the biological information 92.
- Arithmetic processing of the arithmetic processing and SAR prediction values 270 of the next period P 1 of the SAR predicted values 270 of the current period P 0 described above, further successive SAR prediction value 270 arithmetic processing period P 2 may be identical (several 4) to (Equation 6) are used.
- For each SAR (W / kg) in (Equation 4) to (Equation 6) it is calculated as a 6-minute average SAR value or a 10-second average SAR value. Alternatively, it is calculated with a 6-minute average SAR value and a 10-second average SAR value.
- the predicted SAR value 270 can be calculated in response to the change, and the situation where the measured SAR exceeds the limit range can be prevented with higher accuracy. it can.
- step S302 of FIG. 4 the CPU 71 determines whether the calculated SAR predicted value 270 does not exceed the SAR limit condition.
- step S274 is executed, and the control signal synchronized with the actual biological information 92 is transmitted from the sequencer 40 to the modulator 52. Is transmitted, and an RF pulse is emitted from the transmission coil 54 at a timing synchronized with the biological information 92.
- a control signal synchronized with the biological information 92 is sent from the sequencer 40 to the A / D converter 61, and an NMR signal is captured in synchronization with the biological information 92. In this way, the imaging process is performed in synchronization with the actual biological information 92.
- step S302 determines in step S302 that the predicted SAR value 270 exceeds the SAR limit condition
- the execution of the CPU 71 moves to 304, and a countermeasure is taken in step S304.
- a countermeasure for example, the output of the RF pulse output from the transmission coil 54 may be reduced, or the period of the biological information 92 is lengthened after the disturbance of the period of the biological information 92 is settled. Alternatively, imaging may be performed. There are many other possible countermeasures.
- step S274 when imaging is performed in synchronization with the biological information 92, the measured SAR value 67 is monitored in step S278. Specifically, the measured SAR value 67 that is the calculation result of the SAR calculation unit 65 is captured by the CPU 71 as the measured SAR value 67. In step S312, the CPU 71 monitors whether the measured SAR value 67 does not exceed the SAR limit condition. If the CPU 71 determines that the actually measured SAR value 67 exceeds the SAR limit condition, in step S314, processing for interrupting imaging is performed.
- step S326 the imaging result, the detection result of the biological information 92, the statistical processing result of the biological information 92, the result of the calculated SAR predicted value 270, and the actually measured SAR value 67 measurement results and the like are stored in the magnetic disk 73 and stored.
- step S326 280 shown in FIG. 2 and FIG. 3 is executed to finish imaging, and step S290 of FIG. 2 is further executed.
- FIG. 5 is a time table for explaining one processing method related to the SAR prediction calculation before scanning for imaging.
- FIG. 6 shows a flowchart executed by the CPU 71 to perform processing based on the time table shown in FIG. 5, and is an alternative to steps S252 to S256 shown in FIG. Procedures relating to substantially the same processes as those in the flowchart shown in FIG.
- step S252 set the imaging conditions or change the previous settings.
- step S352 the biological information 92 is measured from the biological information receiving unit 90.
- the biological information 92 is, for example, an electrocardiogram. In the electrocardiogram of the subject 11, for example, a pulse cycle is measured.
- the order of step S252 and step S352 is an example, and the order may be different.
- the biometric information 92 obtained for example, an ECG repetition period is P 0 (bpm).
- a division number N for imaging is set.
- the pulse sequence 402 necessary for imaging is divided into N (N is a natural number) to form a pulse sequence 403 divided into a plurality of S1 to SN.
- the irradiation power of the RF pulse for imaging in one cycle of the biological information 92 is divided into N as shown in (Expression 7).
- the SAR of the divided pulse sequence is 3 (W / kg)
- the scan time is 0.5 (sec)
- the period P 0 is 60 (bpm)
- the number of pulse sequences k 10
- the 10-second average SAR is It is calculated as (Equation 10).
- step S256 the CPU 71 determines whether the calculated average SAR predicted value does not exceed the SAR limit value. If the average SAR predicted value exceeds the SAR limit value, the operator is imaged. In order to prompt the change of the condition or the division number N, the execution of the CPU 71 returns to step S252. On the other hand, if the predicted value of the average SAR is within the range of the SAR limit value and does not exceed the limit value, execution proceeds to step S260 in FIG. 2 to perform imaging.
- step S382 corresponding to step S272 of FIG. 4 are the same, but the processing of step S382 will be described again.
- step S384 in FIG. 8 basically has the same procedure as in FIG. 4, the description is omitted in FIG. 4, and therefore step S384 will also be described.
- the SAR is predicted based on the repeated change of the biological information 92, and then imaging is performed according to the pulse sequence, and the SAR is actually measured by this imaging.
- step S382 of FIG. 8 using the value of the period P n-1 immediately before the biometric information 92 to predict the period P n of the biological information 92.
- the value of the cycle P n ⁇ 1 of the biological information 92 may be set as the cycle P n .
- step S276 the 10-second average SAR and / or the 6-minute average SAR are calculated using the above-described formula. For example, it is calculated as follows based on (Equation 11).
- the SAR of the divided pulse sequence is 2.4 (W / kg)
- the scan time is 0.5 (sec)
- the period P n-1 is 80 (bpm)
- step S302 already described is executed, and imaging is performed by the operation of the pulse sequence in the period Pn of the biological information 92 in step S274. Furthermore, execution proceeds from step S322 to step S384, and the same process is performed for the next cycle of the biological information 92 by updating the order N assigned to the cycle.
- FIG. 9 is a diagram for predicting the SAR of the nth and subsequent pulse sequences after the period (n ⁇ 1) th synchronous measurement is completed.
- the SAR before the cycle (n-1) is the actually measured SAR (601) on the monitor.
- the period P n of the biological information 92 which is the interval 603 between the period (n ⁇ 1) th and the period (n + 1) th, is an undetermined value because it is a period during measurement.
- the period P n uses, for example, (Equation 13) and the average SAR using (Equation 14) from the value of the change in period (P n-1 -P n-2 ) of the previous biological information.
- the amount of change (P n-1 to P n-2 ) of the cycle is a term for calculating the change between the previous cycle P n- 1 and the previous cycle P n-2 as described above. That is, the previous period P n-1 is corrected by a change between the previous period P n- 1 and the previous period P n-2 . In this way, the next cycle to be imaged from now on can be predicted with higher accuracy, and the prediction accuracy of the predicted value of the SAR can be improved.
- the SAR of the divided pulse sequence is 2.1 (W / kg), the scan time is 0.5 (sec), the previous period P n-1 is 90 (bpm), and the previous period P n-2 is 80 (bpm).
- Pn is 100 (bpm)
- step S272 in FIG. 4 or step S382 in FIG. 8 based on the above-described period variation (P n-1 -P n-2 ), the period of the biological information 92 period is determined from the measured value of the period of the past biological information 92. A tendency, for example, a change amount between the previous period and the previous period is obtained, and a period P n for imaging is calculated based on the change amount.
- the other steps can be referred to as they are.
- the fourth embodiment of the present invention relates to SAR prediction during scan execution. This will be described using FIG. 9 in the same manner as in the third embodiment.
- the flowchart to be executed is the flowchart shown in FIG. 4 already described.
- a period P n that is a period from which measurement will be performed is calculated by the following processing.
- step S272 is as follows. From the statistical data regarding the period of the biological information 92, a safety margin is given by the sum of the average value of the period P and twice the standard deviation of P, and the period P n at which imaging is performed is calculated using (Equation 16). .
- FIG. 10 shows that the SAR is predicted using the biological information 92 in one embodiment described above with reference to FIGS. 1 to 4 and the other embodiments 1 to 4 described above, and the predicted SAR is determined to exceed the limit.
- 6 is a time table showing an example of temporarily stopping a pulse sequence for imaging, that is, temporarily stopping a scanning operation of the MRI apparatus 10.
- the imaging stop process or the imaging restart process described below can be similarly applied to any of the above-described embodiment and the other embodiments 1 to 4. However, representatively described in FIGS. 7 and 8 This will be specifically described with reference to the examples.
- the biological information 92 may be in a very unstable state. For example, because of a heart disease, a cross-sectional image of the heart or a blood vessel image representing the state of the blood vessels of the heart may be captured in synchronization with the movement of the heart. Although an electrocardiogram is used as information on the movement of the heart, the electrocardiogram may be disturbed.
- the predicted SAR value may exceed the limit value.
- step S382 of the flowchart illustrated in FIG. 8 the period P 2 in which imaging is performed is predicted from the past period P 1 illustrated in FIG. 10 or period information that is not illustrated but before that, and the predicted period P 2 Based on the above, a calculation process for predicting the SAR is performed in step S276 in FIG.
- step S302 illustrated in FIG. 8 the CPU 71 determines whether or not the predicted value of the SAR exceeds the limit value, and when it is determined that the predicted value of the SAR exceeds the limit value, step S304 is executed.
- An example of the specific processing content of step S304 shown in FIG. 8 is shown in FIG.
- step S404 the reason why the operation of the pulse sequence is stopped, that the predicted value of the SAR exceeds the limit value, and further that, for example, the predicted calculation changes in the cycle shortening direction, the state display area 702 of the display 74 is displayed. Is displayed.
- FIG. 7 An example of the operation image 700 displayed on the display 74 is shown in FIG.
- the operation image 700 may be displayed on the display 74 simultaneously with the MRI image being captured.
- a state display area 702 is provided in the operation image 700, and a scan state such as a scan stop state, a reason for the scan stop, and the like are displayed in the state display area 702.
- the display 74 is provided with a biological information display area 712, and displays a waveform of the measured biological information 92 and a waveform based on the prediction of the biological information 92.
- the current time point of measurement of the biological information 92 is displayed as a mark 722, and a past graph from the mark 722 is displayed based on the measurement result. Further, in the future direction from the mark 722, a graph calculated by prediction from the measured values of the past biological information 92 is displayed. In the graph of the biological information 92 based on the past measurement result, the executed scan timing is displayed by a mark 732. Further, on the graph based on the prediction calculation of the biological information 92, the next scan timing when executed is displayed by a mark 734.
- the mark 734 is useful for the operator to determine whether to resume scanning.
- the operation image 700 also includes a display 740 for performing an operation for resuming the imaging operation, for example, an operation button. By selecting the display 740, an instruction to resume the imaging operation is input to the MRI apparatus 10. can do. Furthermore, a SAR display area 704 for displaying a predicted value of the current SAR value, an actual measurement value of the past or the current SAR value, and a limit value of the SAR is provided in the vicinity of the biological information display area 712 representing the state of the biological information 92. It has been.
- step S406 the CPU 71 waits for a restart instruction from the operator, and when there is a restart instruction, the CPU 71 restarts imaging based on the measured value of the biological information 92 that periodically changes in step S412.
- the length of the period indicated by the mark 734 (in this specification, the period length may be simply referred to as a period) is calculated.
- step S414 based on the calculated cycle value, the CPU 71 calculates a predicted value of the SAR. By the execution of step S416 by the CPU 71, it is determined whether or not the predicted SAR value satisfies the condition within the limit value.
- step S418 the operation image 700 shown in FIG. 12 is displayed in step S418 to display the content for restarting scanning for imaging. Further, after step S418, step S274 is executed, and photographing is resumed. Subsequently, step S278 shown in FIG. 8 is executed, and the flowchart of FIG. 8 is executed thereafter.
- step S416 when the predicted value of SAR does not satisfy the condition that it is within the limit value, the execution of CPU 71 moves again from step S416 to step S404, and the predicted value of SAR returns to the imaging restart.
- the reason why the condition is not satisfied is displayed in the status display area 702 of the operation image 700 displayed on the display 74.
- a graph representing the biological information 92 may be displayed by color-coding the graph based on the actual measurement data and the graph based on the prediction calculation. Further, in the graph of the biometric information 92, the section where the scan for imaging is stopped may be displayed in a different color so as to be highlighted so that it can be understood that the scan has not been executed. Further, the section where the calculated predicted SAR value exceeds the limit value may be highlighted, for example, by changing the color.
- Embodiment 6 of the present invention will be described with reference to FIG. 13 showing a time table, FIG. 14 showing a specific flowchart, and FIG. 15 showing an operation image 700 displayed on the display 74.
- the present embodiment represents an example in which the SAR is predicted using the biological information 92 in each of the above-described embodiments and the other embodiments 1 to 5, and the application is canceled when the predicted SAR exceeds the limit.
- FIG. When it is predicted that the SAR limit will be exceeded 904 due to a change in biological information, application cancellation 905 is performed.
- the CPU 71 continues the SAR prediction 906 using the biological information, and when it is determined that the SAR predicted value falls within the limit, the operation of the pulse sequence is resumed 907.
- the state display area 702 of the operation image 700 illustrated in FIG. 15 when the above-described pause is performed, the contents are displayed.
- the waveform of the biological information 92 is displayed in the biological information display area 712 of the operation image 700, and the section determined by the processing unit 70 when the predicted value of the SAR exceeds the limit value is highlighted, for example, by changing the color.
- This display also functions to indicate that the scan has not been performed.
- a resume condition is displayed in the status display area 702 of the operation image 700.
- step S382 shown in FIG. 8 the period length of the biological information 92 to be processed based on the pulse sequence is predicted and calculated, and the calculation for predicting the SAR is performed in step S276 based on the predicted calculation period. To do.
- step S276 the CPU 71 determines whether or not the predicted SAR value exceeds the limit value in step S302. When it is determined that the predicted SAR value exceeds the limit value, step S402 shown in FIG. 14 is executed, and the pulse sequence operation is stopped. As a result, the irradiation of the RF pulse irradiated to the subject 11 is stopped.
- step S432 as described above, the scanning operation pause and automatic restart conditions are displayed in the state display area 702 of the operation image 700 illustrated in FIG.
- the automatic restart condition it is displayed that the scan operation that is the imaging operation is restarted when the predicted value of the SAR satisfies the restriction condition.
- 120 (bpm) which is the predicted calculation value of the current SAR, is displayed in the SAR display area 704 in comparison with the limit value 100 (bpm).
- step S434 it is further determined whether the SAR prediction calculation timing for the next cycle has been reached. Since a scanning operation based on a pulse sequence operation, which is an imaging operation, is performed in synchronization with a change in the biological information 92, the SAR prediction calculation is performed so as to be substantially synchronized with a change in the biological information 92. Therefore, in step S434, it is determined whether or not the SAR prediction calculation timing of the next cycle has come.
- the length of the next cycle is predicted and calculated in step S436 in the state where the SAR prediction calculation timing of the next cycle is reached.
- This calculation method may be calculated based on (Equation 13) described above, or may be another method described above.
- a predicted SAR value is calculated in step S414.
- the CPU 71 determines whether the predicted SAR value is within the limit value range.
- restart of imaging that is, restart of scanning is displayed in the state display area 702 of the operation image 700 in FIG. 15, and step S274 is executed.
- step S416 If it is determined in step S416 that the predicted SAR value exceeds the limit value, the execution of the CPU 71 proceeds from step S416 to step S432, and the SAR prediction is performed in the status display area 702 of the operation image 700 in the next cycle. The content whose value exceeds the limit value is displayed.
- step S434 the change of the biological information 92 and the adjustment of the timing of the measurement of the biological information 92 and the calculation of the SAR predicted value in steps S436 and S414 are performed, and further, the processing related to the next cycle is repeatedly performed.
- FIG. 16 shows the imaging parameters, that is, the imaging conditions that do not exceed the SAR limit when the predicted SAR exceeds the limit when the SAR is predicted using the biological information in the above-described embodiment and other 1 to 4 It is a figure showing the example which changes and continues a scan. Note that this embodiment is not limited to the example in which the imaging condition is automatically changed, and the operator may perform a confirmation operation on the proposed change of the CPU 71. Further, the CPU 71 may present a plurality of change proposals, and a new imaging condition may be determined by the operator selecting it.
- SAR predicted value becomes super SAR limit 1104 due to changes in biological information.
- CPU71 calculates the predicted value of SAR and further predicts that the calculated predicted value of SAR exceeds the limit value of SAR
- CPU71 calculates the sequence parameter, that is, the imaging condition that the predicted value of SAR is within the SAR limit.
- a parameter change 1105 that is an imaging condition is performed.
- the sequence parameter which is the imaging condition, can be changed automatically by the CPU 71, or the changed contents of the CPU 71 can be displayed on the operation image 700 of the display 74 and changed by checking by the operator. Also good.
- the CPU 71 presents a proposal for change, and the operator may select the sequence parameter to be changed by a method of determining a sequence parameter that is a new imaging condition.
- the changed sequence parameter is displayed as an information dialog window in, for example, the area 706 of the operation image 700 shown in FIG. 19 so that the operator who is the operator can easily understand.
- the sequence parameter changed as an example and the rate of SAR relaxation are displayed.
- the waveform of the biological information 92 is displayed in the biological information display area 712 as in the above-described example, and the section where the sequence parameter is changed, for example, the section indicated by the mark 734 is highlighted, for example, by changing the color. This shows that the scan was executed with the SAR relaxed.
- Fig. 17 shows the operation procedure of the CPU 71 for implementing the operation of the time table shown in Fig. 16.
- the execution of the CPU 71 moves from step S302 to step S304.
- step S402 constituting step S302 the operation of the pulse sequence is stopped, and in step S502, the parameters of the pulse sequence that is the imaging condition are changed.
- the CPU 71 may automatically change the sequence parameter, or the CPU 71 proposes a change proposal and the operator selects such as selecting by the operator. It may be a change based on.
- step S504 and step S416 are not necessary. However, even when the sequence parameter is changed completely automatically, the reliability is improved by performing Step S504 and Step S416. If an operator's instruction is added, reliability is further improved by performing Step S504 and Step S416.
- the SAR predicted value is calculated based on the changed sequence parameter that is the imaging condition changed in step S504.
- step S416 it is determined whether the calculated predicted value of the SAR does not exceed the limit value.
- the execution of the CPU 71 proceeds from step S416 to step S512. .
- step S512 a new sequence parameter is displayed in the area 706 of FIG. 18 as described above, the execution proceeds to step S274, and the imaging operation is restarted with the new sequence parameter. In the following procedure, the imaging operation is promoted according to the control of the CPU 71.
- the imaging operation may be continued with the sequence parameter changed in step S502, but the changed sequence parameter may be restored.
- the process of returning the changed sequence parameter to the original is performed according to the procedure shown in step S520. If the predicted SAR value is within the limit range in step S302, step S520 is executed by the CPU 71, and it is determined in step S522 whether the sequence parameter has been changed. If the sequence parameter has not been changed, the process of returning the sequence parameter to 520 does not have to be performed in 520. Therefore, the execution of the CPU 71 proceeds from step S522 to step S274, and the imaging operation is promoted.
- step S526 If the operator's instruction is an instruction to continue imaging using the changed sequence parameter without undoing the change of the sequence parameter, the execution of the CPU 71 from step S526 moves to step S274, and the changed sequence parameter Continue the imaging operation.
- step S532 the predicted SAR value is calculated according to the imaging condition in which the sequence parameter is restored, and the calculated SAR predicted value is obtained. Determine whether or not exceeds the limit. If it is determined in step S532 that the predicted SAR value based on the imaging condition with the sequence parameter restored is within the limit, the sequence parameter is restored to the original value in step S536. Further, the fact that it has been restored is displayed on the operation image 700 in step S536. On the other hand, when the predicted value of the SAR based on the imaging condition with the sequence parameter returned to the original value exceeds the limit, in step S534, a process for not returning the sequence parameter is performed, and this is displayed on the operation image 700. In this case, step S520 is executed again in a process synchronized with the next cycle, and a process for determining whether or not to return the sequence parameter is performed.
- FIG. 19 shows still another embodiment.
- Step S572 (see FIG. 19), which is the method shown in FIG. 14, and step S574 (see FIG. 19), which is the method shown in FIG. 18, for handling when the predicted value of SAR exceeds the limit value And already explained.
- step S572 and step S574 has unique advantages. By using these methods properly, a greater effect can be achieved.
- An example of these usage determinations is shown in step S570 of FIG.
- step S402 the pulse sequence operation is stopped, and step S570 is executed to determine which of step S572 and step S574 is to be executed.
- step S552 of step S570 the state of the biological information 92 is analyzed. For example, is the period length of the biological information 92 fluctuating or stable? Whether the cycle of biological information 92 is repeated when the predicted value of SAR is just below the limit value of SAR, or is the cycle of biological information 92 repeated when the predicted value of SAR greatly exceeds the limit value of SAR? Is determined by the CPU 71.
- step S572 the CPU 71 selects step S572 described with reference to FIG. .
- step S572 there is a case where the cycle of the electrocardiographic waveform is temporarily disturbed due to, for example, arrhythmia.
- step S574 described in FIG. 18 is selected and the sequence parameter is changed.
- the method is executed.
- the heart pulse gradually increases, and as a result, the predicted value of SAR exceeds the limit value.
- the sequence parameter is changed and imaging is executed. In this case, the process in step S520 may or may not be performed.
- step S572 and step S574 have already been described, and a description thereof will be omitted.
- the selection state of step S572 or step S574 is displayed in the state display area 702 of the operation image 700 in step S432 or step S502, for example, during execution of step S572 or step S574. Accordingly, the operator can accurately and accurately grasp the situation, and a highly reliable operation is performed.
- 10 MRI apparatus 11 subject, 20 static magnetic field space, 30 gradient magnetic field generator, 31 gradient magnetic field coil, 32 gradient magnetic field power supply, 40 sequencer, 50 high frequency magnetic field generator, 51 high frequency oscillator, 52 modulator, 53 high frequency amplifier, 54 Transmit coil, 60 signal detector, 61 A / D converter, 62 quadrature detector, 63 signal amplifier, 64 receiver coil, 65 SAR calculator, 70 processor, 71 CPU, 72 memory, 73 magnetic disk, 74 Display, 80 operation unit, 81 trackball, mouse or pad, 82 keyboard, 90 biological information receiving unit.
Landscapes
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Biophysics (AREA)
- General Physics & Mathematics (AREA)
- Physiology (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Power Engineering (AREA)
- Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
- Radiology & Medical Imaging (AREA)
- Signal Processing (AREA)
- General Health & Medical Sciences (AREA)
- High Energy & Nuclear Physics (AREA)
- Pulmonology (AREA)
- Cardiology (AREA)
- Magnetic Resonance Imaging Apparatus (AREA)
Abstract
Description
撮像においては、NMR信号には、傾斜磁場によって異なる位相エンコードが付与されるとともに周波数エンコードされて、時系列データとして計測される。計測されたNMR信号は、二次元又は三次元フーリエ変換されることにより画像に再構成される。
またシーケンサ40からA/D変換器61へ生体情報92に同期した制御信号が送られ、生体情報92に同期してNMR信号が取り込まれる。このようにして実際の生体情報92に同期して撮像処理が行われる。
図5は、撮像のためのスキャン実施前のSAR予測演算に関する1つの処理方法を説明するタイムテーブルである。また図6は、図5に記載のタイムテーブルに基づく処理を行うためにCPU71が実行するフローチャートを示し、図2に示すステップS252~ステップS256の代案である。図2に記載のフローチャートの手順と略同じ処理に関する手順は同じ符号を付す。
本発明の他の実施例2は、スキャン実行中のSAR予測に関する内容である。図7のテーブルおよび図8のフローチャートを用いて説明する。なお、図8に記載するフローチャートは、処理内容が実質的には図4に記載のフローチャートと同じである。図4のステップS272に対応するステップS382について本質的な処理内容は同じであるが、ステップS382の処理を再度説明する。さらに図8のステップS384は、基本的に図4に同様の手順が存在するが、図4では説明を省略しているので、ステップS384についても説明する。
本発明の実施例3は、スキャン実行中のSAR予測に関する内容である。図9を用いて説明する。図9は、周期(n-1)番目の同期計測が完了し、n番目以降のパルスシーケンスのSARを予測する図である。周期(n-1)番目以前のSARは、モニタでの実測SAR(601)である。周期(n-1)番目と周期(n+1)番目との間の間隔603である生体情報92の周期Pnは計測中の周期であるために未確定の値である。直前の生体情報の周期の変化量(Pn-1-Pn-2)の値から、周期Pnを例えば(数13)を用いて算出し、平均SARを(数14)を用いて算出する。この(数13)で周期の変化量(Pn-1~Pn-2)は上述したとおり、前周期Pn-1と前々周期Pn-2との変化を算出する項である。すなわち前周期Pn-1を前周期Pn-1と前々周期Pn-2との変化で補正する。このようにしてこれから撮像しようとする次の周期をより高い精度で予測することができ、SARの予測値の予測精度を向上することができる。
本発明の実施例4は、スキャン実行中のSAR予測に関する内容である。実施例3と同様に図9を用いて説明する。また実行するフローチャートは、既に説明した図4に示すフローチャートである。図4に記載のフローチャートのステップS272において、次の処理により、これから計測を行う周期である周期Pnを算出する。
本発明の他の実施例5について図10に記載のタイムテーブルと図11に記載のフローチャート、および図12に記載のディスプレイ74に表示される表示画面を用いて説明する。図10は、図1から図4を用いて上述した一実施例および上述した他の実施例1~4において生体情報92を用いてSARを予測し、予測したSARが制限を超過すると判断された場合に撮像のためのパルスシーケンスの一時停止、すなわちMRI装置10のスキャン動作を一時停止する一例を表したタイムテーブルである。
本発明の実施例6についてタイムテーブルを表す図13や、具体的なフローチャートを示す図14や、ディスプレイ74に表示される操作画像700を示す図15を用いて説明する。本実施例は、上述した実施例や他の実施例1から5のそれぞれにおいて、生体情報92を用いてSARを予測し、予測したSARが制限を超過したときに印加をキャンセルする例を表した図である。生体情報の変化によってSAR制限超904となると予測したとき、印加キャンセル905を行う。
(他の実施例7)
本発明の他の実施例7について図16乃至図18を用いて説明する。図16は、上述した実施例および他の1~4において生体情報を用いてSARを予測し、予測したSARが制限を超過したときに、SARの制限を超過しないような撮像パラメータすなわち撮像条件に変更し、スキャンを続行する例を表した図である。なおこの実施例では自動的に撮像条件を変更する例に限るものではなく、CPU71の変更案に対して操作者が確認操作を行うようにしても良い。またCPU71が複数の変更案を提示し、操作者が選択することにより新たな撮像条件を決定するようにしても良い。
図19はさらに他の実施例である。SARの予測値が制限値を超える場合の対応について、図14に記載の方法であるステップS572(図19参照のこと)と、図18に記載の方法であるステップS574(図19参照のこと)とを既に説明した。ステップS572とステップS574との処理にはそれぞれ特有の利点があり、これらの方法を使い分けることで、より大きな効果を奏することができる。これらの使い分けの判断の一例を図19のステップS570に示す。
なお、ステップS572あるいはステップS574の選択の状態は、ステップS572あるいはステップS574の実行の中で、例えばステップS432あるいはステップS502において操作画像700の状態表示領域702に表示される。これにより、操作者は状況を正確にしかも的確に把握でき、信頼性の高い操作が行われる。
Claims (15)
- 被検体を収容する空間に静磁場を発生させる静磁場発生部と、
前記静磁場へ重畳して傾斜磁場を発生させる傾斜磁場発生部と、
前記被検体へ照射するための高周波磁場を発生させる高周波磁場発生部と、
前記傾斜磁場の発生および前記高周波磁場の発生をパルスシーケンスに従って制御するシーケンサと、
核磁気共鳴信号を検出する信号検出部と、
SARの予測値を演算する制御部と、
前記被検体の生体情報を受信する生体情報受信部と、を備え、
前記シーケンサは、前記生体情報に同期して前記傾斜磁場の発生および前記高周波磁場の発生を制御し、
前記制御部は、前記生体情報の周期の長さに基づいて、SARの予測値を演算して前記SARの予測値が制限値を超えないかを判断し、
前記SARの予測値が前記制限値を超えないとの前記制御部の判断に基づいて、前記傾斜磁場の発生および前記高周波磁場の発生が制御されて撮像動作が行われ、前記信号検出部で検出された前記核磁気共鳴信号に基づいてMRI画像が生成される、ことを特徴とする磁気共鳴イメージング装置。 - 請求項1に記載の磁気共鳴イメージング装置において、
前記制御部は、次に撮像動作が行われる周期の長さを演算して求め、
前記制御部は、さらに求めた前記周期の長さに基づいて、前記次に撮像動作を行う周期におけるSARの予測値を演算し、
演算された前記SARの予測値に基づいて、前記SARの予測値が前記制限値を超えないかどうかの前記判断が行われる、ことを特徴とする磁気共鳴イメージング装置。 - 請求項2に記載の磁気共鳴イメージング装置において、
前記制御部は、受信した生体情報に基づき、生体情報の周期に関する変化を演算により求め、受信した生体情報と前記演算した前記周期の変化に基づいて、次に撮像動作が行われる周期の長さを演算する、ことを特徴とする磁気共鳴イメージング装置。 - 請求項2に記載の磁気共鳴イメージング装置において、
前記制御部は、受信した生体情報の統計処理により、次に撮像動作が行われる周期の長さを演算し、演算した前記周期の長さに従って前記SARの予測値を演算して求める、ことを特徴とする磁気共鳴イメージング装置。 - 請求項1に記載の磁気共鳴イメージング装置において、
撮像動作を何回の前記生体情報の周期に分けて行うかの回数Nの設定を受け、前記制御部は、N回に分割された撮像動作の各周期での前記高周波磁場発生部の照射パワーを演算し、
さらに前記制御部は、演算された前記照射パワーに基づいて分割された各周期での前記SARの予測値を演算し、前記演算した前記SARの予測値に従って前記撮像動作を行う、ことを特徴とする磁気共鳴イメージング装置。 - 請求項2に記載の磁気共鳴イメージング装置において、
前記SARの予測値が前記制限値を超えないかどうかの判断が前記制御部によって行われ、前記SARの予測値が前記制限値を超える場合に、前記撮像動作が停止され、
前記制御部は、前記撮像動作の再開の指示に従って、前記撮像動作を再開する、ことを特徴とする磁気共鳴イメージング装置。 - 請求項6に記載の磁気共鳴イメージング装置において、前記制御部は、前記撮像動作の再開予定の周期の長さを予測演算し、求められた周期の長さの予測演算値に基づいて、再開予定の周期に関するSARの予測値を演算し、演算された前記SARの予測値が前記制限値を超えない場合に、前記撮像動作を再開する、ことを特徴とする磁気共鳴イメージング装置。
- 請求項6に記載の磁気共鳴イメージング装置において、
ディスプレイがさらに設けられ、前記ディスプレイには、生体情報表示領域が設けられて前記生体情報表示領域には、生体情報の波形が表示され、
さらに前記ディスプレイには、前記再開の指示を行うための操作用表示が表示され、前記操作用表示が操作されることにより、前記撮像動作の前記再開の指示が入力される、ことを特徴とする磁気共鳴イメージング装置。 - 請求項2に記載の磁気共鳴イメージング装置において、
演算された前記周期の変化に基づいて、次に撮像動作が行われる周期の長さが演算され、
演算された次に撮像動作が行われる前記周期の長さに従って次に撮像動作が行われる周期に関する前記SARの予測値が演算され、
演算された前記SARの予測値が前記制限値を超えるかどうかの判断が行われ、
前記SARの予測値が前記制限値を超えない場合には、前記次に撮像動作が行われる周期の撮像動作が行われ、
演算された前記SARの予測値が前記制限値を超える場合には、前記撮像動作が中断され、
さらにその次の周期の長さが演算され、演算された前記その次の周期の長さに基づいて、前記その次の周期のSARの予測値が演算されて、演算された前記その次の周期のSARの予測値が前記制限値を超えるかどうかの判断が行われ、
このようにして、前記生体情報の周期に対応して順に前記SARの予測値が前記制限値を超えるかどうかの判断が行われ、前記SARの予測値が前記制限値を超えない周期において、撮像動作が再開される、ことを特徴とする磁気共鳴イメージング装置。 - 請求項9に記載の磁気共鳴イメージング装置において、
さらにディスプレイが設けられ、前記ディスプレイに生体情報表示領域とSAR表示領域とが設けられ、前記生体情報表示領域に生体情報が表示され、前記SAR表示領域に演算された前記SARの予測値が表示される、ことを特徴とする磁気共鳴イメージング装置。 - 請求項2に記載の磁気共鳴イメージング装置において、
前記SARの予測値が前記制限値を超えないかどうかの前記判断が前記制御部によって行われ、前記SARの予測値が前記制限値を超える場合に、前記撮像動作が停止され、
前記制御部は、撮像のためのシーケンスパラメータを変更し、変更した前記シーケンスパラメータに基づいて撮像動作が再開される、ことを特徴とする磁気共鳴イメージング装置。 - 請求項11に記載の磁気共鳴イメージング装置において、
さらにディスプレイが設けられ、前記ディスプレイに変更前の前記シーケンスパラメータと変更後の前記シーケンスパラメータとが表示される、ことを特徴とする磁気共鳴イメージング装置。 - 請求項11に記載の磁気共鳴イメージング装置において、前記変更されたシーケンスパラメータによる撮像動作において、前記変更前のシーケンスパラメータによるSARの予測値が前記制限値を超えないかどうかの判断が行われ、前記変更前のシーケンスパラメータによる前記SARの予測値が前記制限値を超えない場合に、前記シーケンスパラメータが前記変更前の前記シーケンスパラメータに戻される、ことを特徴とする磁気共鳴イメージング装置。
- 請求項2に記載の磁気共鳴イメージング装置において、
前記SARの予測値が前記制限値を超えないかどうかの判断が前記制御部によって行われ、前記SARの予測値が前記制限値を超える場合に、前記撮像動作が停止され、
前記制御部は、前記生体情報の状態に基づいて、前記SARの予測値が前記制限値を超えないようにするために、撮像のためのシーケンスパラメータを変更する第1の対策処理を行うか、前記生体情報の周期の長さが変わることにより前記SARの予測値が前記制限値を超えない状態となるのを待つ第2の対策処理を行うかを判断し、
前記制御部が第1の対策処理を選択した場合に、前記制御部が前記撮像のためのシーケンスパラメータを変更して撮像動作を再開し、
前記制御部が第2の対策処理を選択した場合に、前記制御部が前記生体情報の周期の長さを予測して前記SARの予測値を演算し、演算した前記SARの予測値が前記制限値を超えないかの判断処理を繰り返し、前記SARの予測値が前記制限値を超えないとの判断結果に基づいて、撮像動作を再開する、ことを特徴とする磁気共鳴イメージング装置。 - 被検体を収容する空間に静磁場を発生させるステップと、
前記静磁場へ重畳して傾斜磁場を発生させるステップと、
前記被検体へ照射するための高周波磁場を発生させるステップと、
前記被検体が発生する核磁気共鳴信号を検出するステップと、
前記被検体の生体情報を受信するステップと、
受信した前記生体情報に同期して、前記傾斜磁場の発生および前記高周波磁場の発生を制御するステップと、
前記生体情報に同期して、前記生体情報の周期の長さを予測すると共に予測した前記生体情報の周期の長さに基づいて、SARの予測値を演算し、演算した前記SARの予測値が制限値を超えないことを判断して撮像動作を行うステップとを、備えることを特徴とする磁気共鳴イメージング装置の制御方法。
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US15/038,567 US20160299202A1 (en) | 2013-12-18 | 2014-12-04 | Magnetic resonance imaging apparatus and control method thereof |
JP2015553470A JPWO2015093296A1 (ja) | 2013-12-18 | 2014-12-04 | 磁気共鳴イメージング装置およびその制御方法 |
CN201480066286.1A CN105792749A (zh) | 2013-12-18 | 2014-12-04 | 磁共振成像装置及其控制方法 |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2013-260707 | 2013-12-18 | ||
JP2013260707 | 2013-12-18 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2015093296A1 true WO2015093296A1 (ja) | 2015-06-25 |
Family
ID=53402645
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2014/082057 WO2015093296A1 (ja) | 2013-12-18 | 2014-12-04 | 磁気共鳴イメージング装置およびその制御方法 |
Country Status (4)
Country | Link |
---|---|
US (1) | US20160299202A1 (ja) |
JP (1) | JPWO2015093296A1 (ja) |
CN (1) | CN105792749A (ja) |
WO (1) | WO2015093296A1 (ja) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2017184931A (ja) * | 2016-04-04 | 2017-10-12 | 株式会社日立製作所 | 磁気共鳴イメージング装置 |
JP2020039869A (ja) * | 2018-09-06 | 2020-03-19 | キヤノンメディカルシステムズ株式会社 | 磁気共鳴イメージング装置 |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102017208813A1 (de) * | 2017-05-24 | 2018-11-29 | Siemens Healthcare Gmbh | Anpassung eines Parameters eines Parametersatzes für eine Magnetresonanz-Messung |
CN110770663B (zh) * | 2017-06-26 | 2024-01-19 | 株式会社东芝 | 可视化系统 |
JP7123767B2 (ja) * | 2018-11-20 | 2022-08-23 | キヤノンメディカルシステムズ株式会社 | 磁気共鳴撮像装置 |
CN113960513A (zh) * | 2020-07-21 | 2022-01-21 | 通用电气精准医疗有限责任公司 | 磁共振成像系统的监测方法和装置以及磁共振成像系统 |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2005144075A (ja) * | 2003-11-20 | 2005-06-09 | Hitachi Medical Corp | 磁気共鳴イメージング装置 |
JP2006095278A (ja) * | 2004-08-30 | 2006-04-13 | Toshiba Corp | 磁気共鳴診断装置 |
JP2009520553A (ja) * | 2005-12-21 | 2009-05-28 | コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ | 磁気共鳴イメージング及び分光法における動き依存データ取得 |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH01148250A (ja) * | 1987-12-04 | 1989-06-09 | Hitachi Ltd | 磁気共鳴検査装置 |
DE10150138B4 (de) * | 2001-10-11 | 2009-10-08 | Siemens Ag | Verfahren zur Magnetresonanz-Bildgebung |
CN100421619C (zh) * | 2004-08-30 | 2008-10-01 | 株式会社东芝 | 磁共振诊断装置 |
WO2009128013A1 (en) * | 2008-04-16 | 2009-10-22 | Koninklijke Philips Electronics N.V. | Real-time local and global sar estimation for patient safety and improved scanning performance |
JP5236356B2 (ja) * | 2008-05-22 | 2013-07-17 | 株式会社日立メディコ | 核磁気共鳴イメージング装置 |
KR20130021194A (ko) * | 2011-08-22 | 2013-03-05 | 삼성전자주식회사 | 자기공명영상 시스템, 이를 제어하는 방법 |
JP5917077B2 (ja) * | 2011-10-13 | 2016-05-11 | 株式会社東芝 | 磁気共鳴イメージング装置 |
-
2014
- 2014-12-04 CN CN201480066286.1A patent/CN105792749A/zh active Pending
- 2014-12-04 WO PCT/JP2014/082057 patent/WO2015093296A1/ja active Application Filing
- 2014-12-04 US US15/038,567 patent/US20160299202A1/en not_active Abandoned
- 2014-12-04 JP JP2015553470A patent/JPWO2015093296A1/ja active Pending
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2005144075A (ja) * | 2003-11-20 | 2005-06-09 | Hitachi Medical Corp | 磁気共鳴イメージング装置 |
JP2006095278A (ja) * | 2004-08-30 | 2006-04-13 | Toshiba Corp | 磁気共鳴診断装置 |
JP2009520553A (ja) * | 2005-12-21 | 2009-05-28 | コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ | 磁気共鳴イメージング及び分光法における動き依存データ取得 |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2017184931A (ja) * | 2016-04-04 | 2017-10-12 | 株式会社日立製作所 | 磁気共鳴イメージング装置 |
JP2020039869A (ja) * | 2018-09-06 | 2020-03-19 | キヤノンメディカルシステムズ株式会社 | 磁気共鳴イメージング装置 |
JP7337603B2 (ja) | 2018-09-06 | 2023-09-04 | キヤノンメディカルシステムズ株式会社 | 磁気共鳴イメージング装置 |
Also Published As
Publication number | Publication date |
---|---|
US20160299202A1 (en) | 2016-10-13 |
CN105792749A (zh) | 2016-07-20 |
JPWO2015093296A1 (ja) | 2017-03-16 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
WO2015093296A1 (ja) | 磁気共鳴イメージング装置およびその制御方法 | |
JP4889482B2 (ja) | 画像データ収集制御方法、画像データ収集装置、及び画像データ収集装置の制御装置 | |
JP4807825B2 (ja) | 磁気共鳴イメージング装置 | |
JP5377219B2 (ja) | 磁気共鳴画像診断装置および磁気共鳴画像撮像方法 | |
JP5236356B2 (ja) | 核磁気共鳴イメージング装置 | |
JP6073570B2 (ja) | 磁気共鳴イメージングシステム及び方法 | |
US10564233B2 (en) | Magnetic resonance imaging apparatus and control method therefor | |
JP2009261904A (ja) | 医用撮像装置 | |
JP5536665B2 (ja) | 磁気共鳴イメージング装置及び磁気共鳴イメージング方法 | |
WO2014034722A1 (ja) | 磁気共鳴イメージング装置及びその比吸収率の演算方法 | |
JP5465565B2 (ja) | 磁気共鳴イメージング装置 | |
JP6433425B2 (ja) | 磁気共鳴イメージング装置および磁気共鳴イメージング方法 | |
JP5337385B2 (ja) | 磁気共鳴映像装置 | |
JP5667890B2 (ja) | 磁気共鳴イメージング装置および医用画像診断装置 | |
JP6441650B2 (ja) | 磁気共鳴イメージング装置 | |
JP5371620B2 (ja) | 核磁気共鳴イメージング装置 | |
JP4454268B2 (ja) | 磁気共鳴イメージング装置 | |
JP4152138B2 (ja) | 磁気共鳴イメージング装置 | |
JP2008104713A (ja) | 磁気共鳴イメージング装置 | |
JP2014171833A (ja) | 磁気共鳴イメージング装置および非造影mra方法 | |
JP6341658B2 (ja) | 磁気共鳴イメージング装置及びレトロスペクティブシネ撮像条件設定方法 | |
JP2017006246A (ja) | 磁気共鳴イメージング装置、及び方法 | |
JP2016106662A (ja) | 磁気共鳴イメージング装置およびその制御方法 | |
JP5902259B2 (ja) | 磁気共鳴映像装置 | |
JP2013052016A (ja) | 磁気共鳴イメージング装置 |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 14871980 Country of ref document: EP Kind code of ref document: A1 |
|
WWE | Wipo information: entry into national phase |
Ref document number: 15038567 Country of ref document: US |
|
ENP | Entry into the national phase |
Ref document number: 2015553470 Country of ref document: JP Kind code of ref document: A |
|
NENP | Non-entry into the national phase |
Ref country code: DE |
|
122 | Ep: pct application non-entry in european phase |
Ref document number: 14871980 Country of ref document: EP Kind code of ref document: A1 |