JP2019050940A - Magnetic resonance imaging method - Google Patents

Abstract

To acquire high brightness and, by extension, high image quality in a whole image in which free radical molecules and the peripheral area are integrated in a magnetic resonance imaging method by DNP-NMR.SOLUTION: A magnetic resonance imaging method includes a step for acquiring a first NMR signal by generating ESR/DNP, a step for acquiring a second NMR signal without generating DNP, and a step for comparing the first and second NMR signals, and acquiring an image. Supply of an electromagnetic wave for acquiring the first and second NMR signals is executed when a prescribed time elapses after applications of external magnetic fields for NMR are started respectively. The prescribed time is selected so that the intensity of a first resonance signal is greater than a first prescribed value, and the intensity of a differential signal between the first resonance signal and the second resonance signal is greater than a second prescribed value.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a magnetic resonance imaging method.

  It is known that the redox reaction accompanied by oxidation and reduction of endogenous molecules plays an important role in maintaining homeostasis. In the redox reaction, electrons are transferred, so that free radical molecules (for example, active oxygen) are generated as reaction intermediates or by-products. It has been pointed out that when free radical molecules are produced excessively in the body, the redox balance is disrupted, which may increase the risk of cancer, heart disease and the like. Therefore, there is a need for imaging free radical molecules.

  As a method for imaging free radical molecules, electron spin resonance imaging (ESRI) is known. However, an image obtained by ESRI has a problem that the correspondence between free radical molecules and their surrounding regions (organs, tissues, etc.) cannot be identified.

  In order to solve this problem, a technique is known in which an image of a peripheral region obtained by magnetic resonance imaging (MRI) is superimposed on an image of free radical molecules obtained by ESRI.

  On the other hand, Patent Document 1, Non-Patent Documents 1 and 2 increase the polarization of nuclear spins of hydrogen atoms (protons) in the vicinity of free radical molecules by irradiating electromagnetic waves that cause resonance of free radical molecules. (So-called Dynamic Nuclear Polarization (DNP)) and a method for indirectly acquiring an image of free radical molecules through an amplified nuclear spin resonance signal are disclosed. An image of the peripheral region of the free radical molecule is imaged by performing MRI. This method is sometimes referred to as DNP-MRI, nuclear / electron double resonance imaging (PEDRI), overhauser effect MRI (OMRI), or the like.

  In DNP-MRI, the external magnetic field applied for MRI increases the intensity of the resonance signal to increase the brightness of the image, so that the intensity is sufficiently larger than the external magnetic field applied for ESR. Converted into a magnetic field.

  By the way, the direction of the nuclear spin in which the DNP is generated is polarized with respect to the direction of the external magnetic field applied at the time of ESR excitation, and is further inverted depending on the degree of the generated ESR. Therefore, the direction of the magnetization of the hydrogen atom group in the vicinity of the free radical molecule (the sum of the magnetic moments of the nuclear spins in the unit volume) also approaches the opposite direction to the direction of the external magnetic field applied during ESR excitation. Change gradually.

  When the ESR is stopped, the intensity of the resonance signal starts to decrease due to the dissipation of energy from the nuclear spin polarized (possibly reversed) by DNP to the surrounding lattice, and the brightness of the image of free radical molecules may decrease. Conceivable. Therefore, in the conventional DNP-MRI, immediately after the electromagnetic wave irradiation for ESR is stopped and the intensity of the external magnetic field is increased, an image is acquired by MRI (Non-Patent Documents 1 and 2).

Japanese Patent No. 5574386

David J. Lurie, et al., "Field-cycled PEDRI imaging of free radicals with detection at 450 mT", Magnetic Resonance Imaging, Volume 23, Issue 2, February 2005, Pages 175-181 David J Lurie, et al., "Field-cycled proton-electron double-resonance imaging of free radicals in large aqueous samples", Journal of Magnetic Resonance, Volume 84, Issue 2, September 1989, Pages 431-437

  According to the conventional DNP-MRI described in Non-Patent Documents 1 and 2, there is a possibility that a high-luminance image can be acquired for free radical molecules. However, the brightness of the image of the surrounding area (organ, tissue, etc.) of free radical molecules has not been sufficiently studied. Accordingly, there is room for improvement in the image quality of the entire image in which the free radical molecule and its peripheral region are integrated.

  Note that this problem applies not only to the case where the object of magnetic resonance imaging is a living body, but also to magnetic resonance imaging of any object that contains (or may contain) free radical molecules. DNP-MRI is referred to as DNP-NMR (Nuclear Magnetic Resonance) with a broader concept including the case where the target of nuclear magnetic resonance is not a nuclear spin of a hydrogen atom.

  It is an object of the present invention to obtain high brightness and consequently high image quality for an entire image in which free radical molecules and their peripheral regions are integrated in a magnetic resonance imaging method using DNP-NMR.

  The intensity of the resonance signal obtained by nuclear magnetic resonance is proportional to the magnitude of the magnetization of the target atomic group. However, in DNP-NMR, even if the magnetic field is converted to an external magnetic field having a high strength when performing MRI, the magnetization does not immediately reach thermal equilibrium in the external magnetic field, and gradually increases in length according to the longitudinal relaxation time T1. Relax and grow. The present invention has been made based on such findings.

A magnetic resonance imaging method according to the present invention comprises:
Applying a first external magnetic field to the object;
By supplying a corresponding electromagnetic wave to the object while applying a second external magnetic field whose intensity is greater than that of the first external magnetic field, nuclear magnetic resonance is generated in the object, and the first resonance Obtaining a signal;
Supplying a corresponding electromagnetic wave while applying the first external magnetic field to the object causes electron spin resonance of free radical molecules contained in the object, thereby being in the vicinity of the free radical molecules. Generating dynamic nuclear polarization for atomic group nuclear spins;
Producing a nuclear magnetic resonance in the object by supplying a corresponding electromagnetic wave in a state where the second external magnetic field is applied to the object, and obtaining a second resonance signal;
Processing the first resonance signal and the second resonance signal to obtain an image;
Supplying the electromagnetic waves for obtaining the first resonance signal and the second resonance signal is performed when a predetermined time has elapsed after starting application of the second external magnetic field,
The predetermined time is selected such that the intensity of the first resonance signal is greater than a first predetermined value and the intensity of a difference signal between the first resonance signal and the second resonance signal is greater than a second predetermined value. To do.

In one embodiment of the invention,
The method may further include the step of causing electron spin resonance in the object and estimating the amount of the free radical molecule based on the obtained resonance signal.
The predetermined time may be selected based on the estimated amount of free radical molecules.

In one embodiment of the invention,
The object may be a living body,
In the step of acquiring the first resonance signal and the step of acquiring the second resonance signal, nuclear magnetic resonance of nuclear spins of hydrogen atoms may be generated in the object.

  In the present invention, the first resonance signal acquired without causing dynamic nuclear polarization for the nuclear spin of the atomic group in the vicinity of the free radical molecule and the second resonance signal acquired with dynamic nuclear polarization generated. The resonance signal is a signal generated when a predetermined time has elapsed after the application of the second external magnetic field is started. The intensity of the first resonance signal is greater than the first predetermined value, and the first resonance signal and the first resonance signal The intensity of the difference signal from the two resonance signals is greater than the second predetermined value.

  Here, the intensity of the first resonance signal corresponds to the brightness of the image of the peripheral region of the free radical molecule, and the intensity of the difference signal between the first resonance signal and the second resonance signal corresponds to the brightness of the image of the free radical molecule. Equivalent to.

  Therefore, according to the present invention, it is possible to obtain high brightness and consequently high image quality for the entire image in which free radical molecules and their peripheral regions are integrated.

1 is a plan view showing an exemplary magnetic resonance imaging apparatus used for carrying out a magnetic resonance imaging method according to an embodiment of the present invention. FIG. It is the sectional view on the AA line of FIG. 5 is a flowchart illustrating a magnetic resonance imaging method according to an embodiment of the present invention. 6 is an exemplary graph showing the behavior of magnetization over time when a magnetic resonance imaging method according to an embodiment of the present invention is performed.

  Hereinafter, a magnetic resonance imaging method according to an embodiment of the present invention will be described with reference to the drawings. Although this magnetic resonance imaging method is not limited to this, it can be implemented using the magnetic resonance imaging apparatus shown in FIGS.

[1. Magnetic resonance imaging method]
FIG. 1 is a plan view showing an exemplary magnetic resonance imaging apparatus 1, and FIG. 2 is a cross-sectional view taken along line AA of FIG. The magnetic resonance imaging apparatus 1 is configured to perform magnetic resonance imaging of an object (or measurement object) by a DNP-NMR (or DNP-MRI) method. The magnetic resonance imaging apparatus 1 includes stages 2 and 3, a first magnetic field application unit 4, a second magnetic field application unit 5, a detection unit 6, a motor 7, an NMR console 8, and the like. The stages 2 and 3 have a disk shape and are arranged in parallel at a predetermined distance from each other. The stages 2 and 3 are attached to an output shaft 71 (extending along the central shaft 101) of the motor 7. The motor 7 may be a servo motor 7.

  The first magnetic field application unit 4 includes a pair of magnets 41 and 41 provided on the stages 2 and 3. The second magnetic field application unit 5 includes a pair of magnets 51 and 51 provided on the stages 2 and 3. Each of the magnets 41 and 51 is a permanent magnet, but may be an electromagnet. The electromagnet may be a superconducting magnet or a normal conducting magnet. The magnets 41 and 51 are configured to apply a uniform magnetic field around the object.

  The magnets 41 and 41 apply a magnetic field (first external magnetic field) having a magnitude that generates electron spin resonance (ESR) of free radical molecules contained in the object (for electron spin) to the object. If the object is a living body, the strength of the first external magnetic field is typically about 1 mT or more and about 10 mT or less, but the present invention is not limited to this. The magnets 51 and 51 apply a magnetic field (second external magnetic field) having a magnitude that generates nuclear magnetic resonance (NMR) to the nuclear spins of atoms included in the target object. If the object is a living body and the object for generating NMR is a nuclear spin of a hydrogen atom, the intensity of the second external magnetic field is typically about 0.2 Tesla or more and about 3 Tesla or less. It is not limited to this. The direction of the second external magnetic field felt by the object at the position of the object is the same (or substantially the same) as the direction of the first external magnetic field.

  Although not shown in the figure, the detection unit 6 uses an ESR coil (surface coil resonator or cavity resonator) that supplies electromagnetic waves (for example, microwaves) to free radical molecules in electron spin resonance (ESR), and a magnetic field. It has a shim coil for application, three known gradient magnetic field coils provided in a general MRI apparatus, and a transmission / reception coil for nuclear magnetic resonance (NMR). The three gradient magnetic field coils apply a slice selection gradient magnetic field, a phase encoding gradient magnetic field, and a frequency encoding (reading) gradient magnetic field to the object. The imaging cross section of the object is set according to the application method of these gradient magnetic fields. The detection unit 6 has a cylindrical core (not shown), and the object is disposed in the core.

  When the motor 7 is operated, the first and second magnetic field application units 4 and 5 including the magnets 41 and 51 rotate together with the output shaft 71. Reference numeral 102 is attached to the trajectory through which the central portions of the magnets 41 and 51 pass. The detection unit 6 is provided in a certain area on the track 102. The detection unit 6 is fixed to a predetermined part (not shown).

  The NMR console 8 has a processor and a memory (not shown). The NMR console 8 is connected to one or more power supplies. The NMR console 8 is configured to execute a control operation described below by executing a predetermined program stored in a memory by a processor. The NMR console 8 is connected to the motor 7, the ESR coil of the detection unit 6, the gradient magnetic field coil, and the NMR probe (transmission / reception coil).

  The NMR console 8 transmits a control signal for controlling the operation of the motor 7 to the motor 7 and receives the rotation angle from the motor 7. The NMR console 8 is connected to a controller for a motor (servo motor). The controller may be independent from or integrated with the NMR console 8. The NMR console 8 transmits a signal to the surface coil resonator of the detection unit 6 so that the first magnetic field application unit 4 supplies an electromagnetic wave for ESR to the object. The NMR console 8 transmits a signal to three gradient magnetic field coils provided in the detection unit 6. The NMR console 8 transmits a signal to the NMR probe of the detection unit 6 so that the second magnetic field application unit 5 supplies the electromagnetic wave for NMR to the object, and the nuclear magnetic resonance signal (NMR signal) from the NMR probe is transmitted. Receive.

  The NMR console 8 is configured to process an NMR signal transmitted from the NMR probe of the detection unit 6 to acquire an image.

  In the magnetic resonance imaging apparatus 1, the first and second magnetic field application units 4 and 5 are rotated together with the stages 2 and 3 while the detection unit 6 is fixed and stationary. The detection unit 6 may be rotated while the first and second magnetic field application units 4 and 5 are fixed and stationary.

[2. Magnetic resonance imaging method]
FIG. 3 is a flowchart illustrating a magnetic resonance imaging method according to an embodiment of the present invention. This method includes steps 201-211. Steps 201 to 211 are performed in this order.

  In step 201, an object is prepared. The object may be a living body such as a person, a mouse, or a rat. However, in this embodiment, the object may be an object including (or possibly including) a free radical molecule, and is not limited to a living body. For example, if the object is a living body and the amount of free radical molecules contained in the object is not sufficient, a paramagnetic molecular probe (for example, nitroxyl radicals, triallylmethyl radicals, etc.) is previously applied to the living body. It may be administered.

  In step 202, the magnetic resonance imaging apparatus 1 is operated. Hereinafter, the operation of the magnetic resonance imaging apparatus 1 is controlled based on signals transmitted from the NMR console 8 to the motor 7, the surface coil resonator of the detection unit 6, the gradient magnetic field coil, and the NMR probe. First, rotation of the output shaft 71 of the motor 7 is started, and rotation of the first magnetic field application unit 4 and the second magnetic field application unit 5 is started.

  In step 204, the external magnetic field applied to the object is converted into a second external magnetic field having a higher strength. As described above, the strength of the second external magnetic field is greater than the strength of the first external magnetic field. Thus, the process of converting the external magnetic field applied to the object into one having a different intensity is called field cycling.

  In step 205, in a state in which the second external magnetic field is applied to the object, a corresponding electromagnetic wave (that is, an electromagnetic wave that causes nuclear magnetic resonance with respect to a group of atoms in the object, for example, RF ( radio frequency) waves. The electromagnetic wave is supplied when a predetermined time elapses after the application of the second external magnetic field is started. The NMR signal (first resonance signal) generated in step 205 is received by the NMR console 8.

  The electromagnetic wave for the NMR is a pulse wave, and an NMR signal may be acquired by an echo method (spin echo method, gradient echo method, etc.), or a free induction decay (FID) signal may be acquired as an NMR signal. Good.

  In step 206, in order to obtain one or a plurality of images, while changing the gradient magnetic field supplied to the object (for example, phase encoding), steps 203 to 205 are repeated a plurality of times to obtain a group of first resonance signals (i.e., Data for filling m rows and n columns of k space) is obtained. Then, the group of first resonance signals are processed by the NMR console 8 (specifically, a two-dimensional Fourier transform or a three-dimensional Fourier transform is calculated), thereby obtaining a two-dimensional image of the vicinity and surrounding region of the free radical molecule. Alternatively, a three-dimensional image (one or more first images) is obtained. The peripheral region of the free radical molecule includes a region near the free radical molecule. The peripheral area may be a part or the whole of the object. If the object is a living body, the peripheral region may be an organ or a tissue.

  In step 207, first, the external magnetic field applied to the object is converted into a first external magnetic field having a lower strength. And while applying a 1st external magnetic field to a target object, corresponding electromagnetic waves (namely, electromagnetic waves which produce ESR about the electron spin of the free radical molecule contained in a target object) are supplied. The electromagnetic wave for the ESR may be a continuous wave or a pulse wave, for example, a microwave. However, ESR does not occur unless the object contains free radical molecules.

  When ESR occurs, the polarization of the nuclear spin of the atomic group in the vicinity of the free radical molecule increases from the electron spin of the free radical molecule due to the overhauser effect (dynamic nuclear polarization: DNP).

  Here, an atomic group in the vicinity of a free radical molecule where DNP occurs refers to an atomic group having a nuclear spin at a position that is separated from the electron radical of the free radical molecule by a quantum mechanical interaction. It's okay. Therefore, the nuclear spin of the atomic group in the vicinity of the free radical molecule and the electron spin of the free radical molecule can generate DNP. The direction of the nuclear spin in which DNP is generated is polarized (in some cases reversed) with respect to the direction of the first external magnetic field (and the direction of the second external magnetic field) applied to generate ESR.

  Steps 208 to 210 are performed in the same manner as steps 204 to 206. In step 208, as in step 204, the external magnetic field applied to the object is converted into a second external magnetic field (field cycling). In step 209, as in step 205, the application of the second external magnetic field is started in the state where the second external magnetic field is applied to the object, and the corresponding electromagnetic wave (that is, the target) An electromagnetic wave that causes NMR is supplied to a group of atoms in the object. The resulting NMR signal (second resonance signal) is received by the NMR console 8.

  In step 210, as in step 206, in order to obtain one or more images, the gradient magnetic field supplied to the object is changed (for example, phase encoding), and steps 203 to 205 are repeated a plurality of times. Two resonance signals (that is, data filling m rows and n columns in k space) are obtained. Then, by processing the group of second resonance signals by the NMR console 8, a two-dimensional image or a three-dimensional image (one or more second images) of the peripheral region of the free radical molecule is obtained.

  In step 211, the NMR console 8 compares the first image obtained in step 206 with the second image obtained in step 210. The NMR console 8 obtains an image of free radical molecules, for example, by calculating a difference in image intensity between the first image and the second image or a change rate of the image intensity.

  FIG. 4 is a graph showing exemplary magnetization behavior over time when performing a magnetic resonance imaging method according to an embodiment of the present invention. The horizontal axis of the graph represents time, and the vertical axis represents the magnitude of magnetization. Among the magnetization vectors, components in the same direction as the first and second external magnetic fields are indicated by positive values, and components opposite to the directions of the first and second external magnetic fields are indicated by negative values.

  Here, the first and second resonance signals obtained in steps 205 and 209 include a signal component resulting from the magnetization of the atomic group in the entire peripheral region of the free radical molecule. The first resonance signal is an NMR signal obtained without causing DNP, and the second resonance signal is an NMR signal obtained by causing DNP. In FIG. 4, the magnetization 301 (positive or negative component thereof) corresponding to the first resonance signal is denoted by reference numeral 301, and DNP has occurred in the second resonance signal (of the atomic group in the vicinity of the free radical). Reference numeral 302 denotes magnetization (positive or negative component) caused by nuclear spin.

  At time t1, the first external magnetic field is applied to the object, and the magnitude of the magnetization of the atomic group in the object (in the peripheral region of the free radical molecule) is M0 (step 203, step 207). ). From time t1 to time t2, a first external magnetic field is applied to the object and a corresponding electromagnetic wave for ESR is supplied (step 207). As a result, ESR of free radical molecules occurs, and as a result, DNP occurs for nuclear spins of atomic groups in the vicinity of the free radical molecules. As a result, the direction of the magnetization 301 changes so as to approach a direction opposite to the direction of the first external magnetic field, and the magnitude of the magnetization 301 reaches M1 at time t2. On the other hand, the magnitude of the magnetization 302 remains M0 at time t2.

  Next, at time t2, the external magnetic field applied to the object is converted into a second external magnetic field (steps 204 and 208). The magnetizations 301 and 302 increase the longitudinal relaxation time as a time constant according to the strength of the second external magnetic field from M1 and M0 after time t2, respectively.

Next, at time t _image , an electromagnetic wave corresponding to the atomic group in the object is supplied to generate NMR (steps 205 and 209). At time t _image , the magnitude of the magnetization 301 is M1 ′, and the magnitude of the magnetization 302 is M2.

  Here, as shown in FIG. 1, the first and second magnetic field application units 4 and 5 may be arranged at a predetermined distance from each other on the stages 2 and 3 in order to minimize the influence of the leakage magnetic field. After the ESR is terminated at time t2, the second external magnetic field is applied after a little time has elapsed. However, in FIG. 4, this time difference is omitted in order to simplify the discussion.

  Here, the intensity of the first resonance signal is based on the NMR signal of the nuclear spin that does not generate DNP, and corresponds to the luminance of the image of the peripheral region of the free radical molecule. On the other hand, the intensity of the difference signal between the first resonance signal and the second resonance signal substantially corresponds to the luminance of the image of free radical molecules. Therefore, in order to increase the luminance of the image of free radical molecules, the first resonance signal and the second resonance signal can be acquired immediately after the field cycling (for example, when the strength of the second external magnetic field is stabilized). Possible (see Non-Patent Documents 1 and 2). However, in this case, the intensity of the first resonance signal has not yet increased, and the luminance of the image in the peripheral region of the free radical molecule is small.

Therefore, in this embodiment, after the field cycling, the intensity of the first resonance signal is greater than the first predetermined value for a predetermined time (time from time t2 to time _timage ) until the electromagnetic wave for NMR is supplied. The intensity of the difference signal between the first resonance signal and the second resonance signal is selected to be greater than the second predetermined value. The first predetermined value is a value within a range allowed for the luminance of the image of the peripheral region of the free radical molecule, and the second predetermined value is a value within a range allowed for the luminance of the image of the free radical molecule. . In this way, high brightness and consequently high image quality can be obtained for the entire image in which free radical molecules and their peripheral regions are integrated.

  The first predetermined value and the second predetermined value may be input by the operator via the input unit provided in the magnetic resonance imaging apparatus 1, for example, connected to the NMR console 8.

[3. Other Embodiments]
It should be understood that the scope of the present invention is not limited to the contents of the above-described embodiments. In addition, other embodiments may be configured by adding various improvements, design changes, and deletions to the above-described embodiment.

  For example, in the above-described embodiment, the intensity of the first resonance signal is greater than the first predetermined value and the intensity of the difference signal between the first resonance signal and the second resonance signal is greater than the second predetermined value during the predetermined time. Although it has been selected to be large, if the amount of free radical molecules contained in the object is large, the time until the intensity of the difference signal between the first resonance signal and the second resonance signal becomes equal to or lower than the second predetermined value is long. Become. Therefore, in an embodiment, the amount of free radical molecules contained in the object may be estimated in advance, and the predetermined time may be selected based on the estimated amount of free radical molecules. The amount of free radical molecules can be estimated from the degree of absorption in an absorption spectrum obtained by performing electron spin resonance on the electron spins of the free radical molecules. When carrying out electron spin resonance, it is preferable that the free radical molecule reacts with the spin trap agent to be stabilized. In this embodiment, the NMR console 8 is configured to receive an electron spin resonance signal (ESR signal) transmitted from the detection unit 6.

  In the above-described embodiment, the first and second images in which the free radical molecule and its peripheral region are integrated are obtained in steps 203 to 206 and steps 207 to 210, respectively. That is, according to the NMR pulse sequence (for example, phase encoding), a process of filling in the k-space without distinguishing the coordinates corresponding to the free radical molecule and its peripheral region was performed. In other embodiments, a process may be performed in which all the coordinates corresponding to the free radical molecules are first filled in the k space and then all the coordinates corresponding to the peripheral region are filled (or vice versa). This process can be performed by alternately performing ESR and NMR. Specifically, after performing Steps 203 to 205, the process of performing Steps 207 to 209 is continuously performed until all the k-space coordinates are filled. In this embodiment, since encoding (phase encoding and frequency encoding) is also performed alternately, the first resonance image and the second resonance image are obtained last. According to this embodiment, by performing ESR and NMR alternately, an increase in the temperature of the object due to ESR irradiation can be suppressed. In particular, when the object is a human body, an effect that safety can be secured by suppressing the temperature rise is obtained.

DESCRIPTION OF SYMBOLS 1 Magnetic resonance imaging device 2, 3 Stage 4 1st magnetic field application part 5 2nd magnetic field application part 6 Detection part 7 Motor 8 NMR console

Claims (3)

Applying a first external magnetic field to the object;
By supplying a corresponding electromagnetic wave to the object while applying a second external magnetic field whose intensity is greater than that of the first external magnetic field, nuclear magnetic resonance is generated in the object, and the first resonance Obtaining a signal;
Supplying a corresponding electromagnetic wave while applying the first external magnetic field to the object causes electron spin resonance of free radical molecules contained in the object, thereby being in the vicinity of the free radical molecules. Generating dynamic nuclear polarization for atomic group nuclear spins;
Producing a nuclear magnetic resonance in the object by supplying a corresponding electromagnetic wave in a state where the second external magnetic field is applied to the object, and obtaining a second resonance signal;
Processing the first resonance signal and the second resonance signal to obtain an image;
Supplying the electromagnetic waves for obtaining the first resonance signal and the second resonance signal is performed when a predetermined time has elapsed after starting application of the second external magnetic field,
The predetermined time is selected such that the intensity of the first resonance signal is greater than a first predetermined value and the intensity of a difference signal between the first resonance signal and the second resonance signal is greater than a second predetermined value. To
Magnetic resonance imaging method. Generating electron spin resonance in the object and further estimating the amount of free radical molecules based on the obtained resonance signal;
The predetermined time is selected based on the estimated amount of free radical molecules.
The magnetic resonance imaging method of claim 1. The object is a living body,
In the step of acquiring the first resonance signal and the step of acquiring the second resonance signal, nuclear magnetic resonance of nuclear spins of hydrogen atoms is generated in the object.
The magnetic resonance imaging method according to claim 1 or 2.

Images