JP2005160749A - Magnetic resonance imaging apparatus having diagnostic/therapeutic function using high gradient magnetic field - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic resonance imaging apparatus capable of making magnetic particles stay at a specific area within the body of a subject for a sufficient time for obtaining an advantageous effect and also capable of confirming the course of treatment or diagnosis of the patient. <P>SOLUTION: The subject 1 is placed in a photographing space of a magnetic resonance imaging apparatus and an area of the patient affected by cancer is photographed and located to store its information. A magnetic thread is then inserted into the proximity of the affected area of the subject 1 using a guide mechanism 25 and medicine solution for hyperthermia containing the magnetic particles is injected into the affected area using the guide mechanism. The frequency of an RF coil is then changed and the magnetic particles staying around the affected area is heated by high-frequency magnetic field. The affected area is photographed by magnetic resonance imaging after heating treatment. When more than a predetermined number of cancer cells are recognized, the affected area is heated again by high frequency. A bypassing means for collecting medicines is installed in the subject 1 and the magnetic particles bound to cancer cells are collected. Whether specific cells are collected or not is then judged using the magnetic resonance imaging. When the specific cells are judged to be collected, the bypassing means is removed and the treatment is finished. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thermotherapy apparatus, and more particularly to a magnetic resonance imaging apparatus having a thermotherapy function.

  Thermal therapy (hyperthermia) is a treatment method that heats the local area of a tumor or the like to 42 ° C. or more for 30 to 60 minutes, and how to heat the area limited to the local area as much as possible is a problem. It has become.

  For this reason, the technique described in patent document 1 and patent document 2 is developed regarding the said thermotherapy, for example.

  In the technique described in Patent Document 1, magnetically responsive particles are added in advance to a tissue such as a human or animal tumor, and an AC gradient magnetic field region is generated between two magnetic field generating means. The tissue site such as the tumor is placed in the region. And it is the technique which increases the heat | fever or kinetic energy of magnetically responsive particle | grains, and inactivates or destroys tissues, such as a tumor.

  The technique described in Patent Document 2 is a technique for sedating pain and suppressing an inflammatory process in a diseased joint based on heat generated by iron oxide particles in an alternating electromagnetic field.

Japanese translation of PCT publication No. 2003-508173 Special table 2003-507434 gazette

  However, in the above prior art, since the liquid carried on the ferromagnetic particles injected into the tissue for diagnosis or treatment diffuses inside the tissue of the subject, this liquid is used for a long time. It was difficult to retain the water, and no further heat effect could be expected.

  In addition, attempts have been made to concentrate magnetic particles on a specific site using a magnetic gradient, but the magnetic gradient force is small and the range that can be applied is limited to the body surface of the subject.

  Therefore, it has been difficult to retain the magnetic particles in a specific region within the body of the subject for a time sufficient to obtain an effective effect.

  The object of the present invention is to allow magnetic particles to stay in a specific region within the body of a subject for a sufficient time to obtain an effective effect, and to confirm the course of treatment or diagnosis of the affected area. It is to realize an imaging apparatus.

In order to achieve the above object, the present invention is configured as follows.
(1) A magnetic resonance imaging apparatus includes a tomographic image of a subject based on a static magnetic field generation unit, a gradient magnetic field generation unit, a high-frequency transmission coil, a high-frequency reception coil, and a nuclear magnetic resonance signal received by the high-frequency reception coil. Image reconstructing means for reconstructing the image, and a gradient magnetic field generating means, a high frequency transmitting coil, a high frequency receiving coil, and an operation control means for controlling operations of the image reconstructing means.

  This magnetic resonance imaging apparatus includes a magnetic element inserted into the body of a subject and a guide mechanism having a through hole for injecting a therapeutic agent for thermal treatment. Then, after the magnetic element is inserted into the subject and the medicine for thermal treatment is injected, the operation control means transmits the high frequency to the subject by the high-frequency transmission coil, and the magnetic element is inserted. Means for heating the heated part.

  (2) Preferably, in the above (1), the operation control means captures a tomographic image of the site before heating the site where the magnetic element is inserted, and also controls the site of the site after heating the site. A tomographic image is taken, the images before and after the heat treatment are compared, and the heating means is controlled in response to a change in a predetermined portion of the part.

  (3) Preferably, in the above (1), the subject and the drug recovery means for recovering the drug from the subject using the static magnetic field generated by the static magnetic field generation means are alternately arranged in the static Arranged in a magnetic field, means for alternately taking medicine and taking a tomographic image of the subject, and means for judging whether or not the medicine has been collected from the tomographic image.

  (4) Preferably, in the above (1), (2), and (3), the magnetic element is a thin wire made of a ferromagnetic material.

  According to the present invention, a magnetic resonance imaging apparatus capable of retaining magnetic particles in a specific region in the body of a subject for a sufficient time to obtain an effective effect and confirming treatment or diagnosis progress of the affected area. Can be realized.

  Moreover, the paramagnetic substance can be used for a magnetic particle, and disturbance of the tomographic image by an MRI apparatus can be reduced compared with the case where a ferromagnetic substance is used.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is an overall schematic configuration diagram of a magnetic resonance imaging apparatus (MRI apparatus) to which the present invention is applied.

  In FIG. 1, the MRI apparatus includes a static magnetic field generating magnet 2, a gradient magnetic field generating system 3, a transmitting system 5, a receiving system 6, a signal processing system 7, a sequencer 4, a central processing unit (CPU) 8, It has.

  The static magnetic field generating magnet 2 generates a uniform static magnetic field around the subject 1 placed on a couch (not shown) on the bed in the direction of the body axis or in the direction perpendicular to the body axis. A permanent magnet type, normal conducting type or superconducting type magnetic field generating means is arranged in a space having a certain extent around the specimen 1.

  The gradient magnetic field generation system 3 includes a gradient magnetic field coil 9 wound in three axial directions of X, Y, and Z, and a gradient magnetic field power source 10 that drives each gradient magnetic field coil, and follows a command from a sequencer 4 to be described later. By driving the gradient magnetic field power supply 10 of each of the coils X, Y, and Z, gradient magnetic fields Gx, Gy, and Gz in the three-axis directions of X, Y, and Z are applied to the subject 1. The slice plane for the subject 1 can be set by applying the gradient magnetic field.

  The sequencer 4 repeatedly applies a high-frequency magnetic field pulse that causes nuclear magnetic resonance to the atomic nuclei constituting the living tissue of the subject 1 in a predetermined pulse sequence. The sequencer 4 operates under the control of the CPU 8 and sends various commands necessary for collecting tomographic data of the subject 1 to the transmission system 5, the gradient magnetic field generation system 3, and the reception system 6.

  The transmission system 5 irradiates a high-frequency magnetic field that causes nuclear magnetic resonance to the atomic nucleus constituting the living tissue of the subject 1 by the high-frequency pulse sent out from the sequencer 4. The transmission system 5 includes a high-frequency oscillator 11, a modulator 12, a high-frequency amplifier 13, and a high-frequency coil 14a on the transmission side.

  The high-frequency pulse output from the high-frequency oscillator 11 is amplitude-modulated by the modulator 12 in accordance with a command from the sequencer 4, and the high-frequency amplifier 13 amplifies the amplitude-modulated high-frequency pulse. Then, by supplying the amplified high frequency pulse to the high frequency coil 14 a arranged close to the subject 1, the subject 1 is irradiated with electromagnetic waves.

  The receiving system 6 detects an echo signal (NMR signal) emitted by nuclear magnetic resonance of the nucleus of the living tissue of the subject 1. The reception system 6 includes a reception-side high-frequency coil 14 b, an amplifier 15, a quadrature phase detector 16, and an A / D converter 17.

  The response electromagnetic wave (NMR signal) of the subject 1 due to the electromagnetic wave irradiated from the high frequency coil 14a on the transmission side is detected by the high frequency coil 14b arranged close to the subject 1, and the amplifier 15 and the quadrature detector 16 are passed through. To the A / D converter 17 and converted into a digital quantity. Further, the signal supplied to the quadrature phase detector 16 is made into two series of collected data sampled by the quadrature phase detector 16 at a timing according to a command from the sequencer 4, and the signal is sent to the signal processing system 7.

  The signal processing system 7 includes a CPU (operation control calculation means) 8, a recording device such as a magnetic disk 18 and a magnetic tape 19, and a display 20 such as a CRT. The CPU 8 performs Fourier transform, correction coefficient calculation, and image reconstruction. The signal intensity distribution of an arbitrary cross section or a distribution obtained by performing an appropriate calculation on a plurality of signals is imaged and displayed as a tomographic image on the display 20.

Next, the principle of the present invention will be described.
(A) As shown in FIG. 2, the magnetic body element is inserted into the body of the subject 1 which is arranged in the uniform static magnetic field space region 50 and has been previously injected with the magnetic response substance. A sudden magnetic field gradient is generated, and a large magnetic attraction force acts on the magnetic response substance in the body.

  This is because when the ultrafine ferromagnetic wire 21 is arranged in the magnetic field, as shown in FIG. 3, the magnetic lines concentrate on the thin line 21, the surrounding magnetic field lines are extremely distorted, and a large magnetic gradient is generated. .

In general, the magnetic force F _H acting on a unit volume of substance is expressed by the following formula (1).
F _H = p · x _g · H (dH / dy) --- (1)
Here, in the above formula (1), p is the density, x _g is the mass magnetic susceptibility, H is the magnetic field strength, and (dH / dy) is the magnetic field gradient.

  From the above formula (1), it can be seen that in order to increase the magnetic force, the magnetic field strength and the magnetic field gradient should be increased if the magnetic response material to which the magnetic force is applied is constant.

  Furthermore, when a large magnetic force is applied to the human body, increasing the magnetic field strength makes the magnet larger than the space size, so it is effective to increase the magnetic field gradient.

  As described above, when the ultrafine ferromagnetic thin wire 21 is disposed in the magnetic field, the magnetic lines of force concentrate on the thin wire 21, the surrounding magnetic field lines are extremely distorted, and a large magnetic gradient is generated.

The magnetic gradient is given by the ratio between the saturation magnetization M _s of the magnetic material and the radius a of the thin wire 21 as in the following equation (2). That is, it can be seen that a large magnetic force can act on the periphery of a ferromagnetic thin line.
dH / dy = M _s / a (2)
In general, the magnetic field gradient that can be applied by a permanent magnet or the like is 1 × 10 ⁷ A / m ^2. However, when a thin wire 21 having a diameter of 0.1 mm is arranged in the same magnetic field space, the surrounding area is about 1000 times 1 × ^{10 10} A. Since a magnetic field gradient of / m ² is generated, a very large magnetic force can be applied.

  Moreover, since the volume is small when the thin wire 21 is used, the magnetic attraction force when introduced into the uniform space is small, and the introduction mechanism of the thin wire 21 may be relatively small.

  Further, by arranging the longitudinal direction of the magnetic thin wire 21 perpendicular to the magnetic field direction, a steep magnetic field gradient can be generated around the radial direction of the thin wire 21.

  (B) As shown in FIG. 4, when a steep magnetic field gradient is generated in the body of the subject 1, the liquid carried on the magnetic response substance 22 such as a magnetic particle or a magnetic body in the body fluid of the subject 1. A large magnetic force acts to suppress the circulation of this liquid in the body, and it becomes possible to stay or separate.

  (C) The magnetic force acting on the magnetic body 22 increases as the magnetic susceptibility of the attracting substance increases. Therefore, when the strength of the external magnetic field is increased, the paramagnetic body simply increases without being saturated. Not only when the body 22 is a ferromagnetic body, but also when it is a paramagnetic substance such as copper or alumina, it is possible to cause magnetic interference.

  Since paramagnetic substances such as copper and alumina can be used, when taking a tomographic image with an MRI apparatus, it is possible to avoid disturbance of the image.

  (D) When these magnetically responsive substances 22 retained in the body of the subject 1 are heated at a high frequency, the cellular tissue in the region where the magnetic responsive substances 22 are retained can be indirectly heated. For this reason, a specific site | part can be selectively heat-treated.

  (E) A device capable of exhibiting the above functions is a general MRI apparatus, a guide guiding mechanism capable of arranging magnetic elements inside a uniform space, and a coil capable of high-frequency heating the magnetic response material 22 staying in the body of the subject 1 It can be achieved by providing.

  (F) Further, after observing with the MRI function, a nonmagnetic guide is inserted into a specific part of the subject 1 arranged in the uniform static magnetic field space and positioned, and then the magnetic material is applied from outside the uniform magnetic field space. By introducing the element into the body of the subject 1 and generating a steep magnetic field gradient around the magnetic element and causing magnetic interference with the magnetic response substance in the body, a specific region is selectively subjected to thermal treatment. be able to.

  (G) In addition, since there is a region with a large magnetic field gradient at the end of a magnet of a general MRI apparatus, a magnetic field gradient is applied to the body of the subject 1 without the need to provide a special mechanism for introducing a magnetic element. Can be made.

  (H) In addition, a contrast agent containing a ferromagnetic element is injected into the subject 1 and the contrast agent is retained in a specific part. Then, the magnetic element is removed, and imaging is performed in a uniform magnetic field space. Photography techniques can also be performed.

  Note that the magnetic response substance 22 circulating in the body of the subject 1 can be effective regardless of whether it is a pharmaceutical product for diagnosis or treatment or one generated by itself in the body of the subject 1.

Next, specific embodiments of the present invention will be described.
FIG. 5 is a schematic perspective view of an MRI apparatus according to an embodiment of the present invention. This embodiment is an apparatus related to hyperthermia that can heat and kill cancer cells.

  As shown in FIG. 5, the MRI apparatus according to the embodiment of the present invention includes a guide mechanism 25 that inserts a magnetic thin wire into the subject 1 disposed on a table (bed) 24.

  As shown in FIG. 6, the guide mechanism 25 holds a collection 26 of magnetic thin wires, a through-hole 28 into which a medicine containing metal particles for hyperthermia can be injected, and a collection 26 of magnetic thin wires by a doctor or the like. A possible gripping mechanism 27 is provided.

  A sponge-like assembly 26 made of magnetic thin wires is held at the tip of the guide mechanism 25, and after being inserted into the body of the subject 1, the assembly 26 of the metal thin wires can remain in the body.

  A treatment operation according to an embodiment of the present invention will be described with reference to an operation flowchart shown in FIG.

  First, after placing the subject 1 in the imaging space of the MRI apparatus, MR imaging of the cancerous part of the patient is performed to identify the site and record the information (steps 100 and 101).

  Thereafter, the assembly 26 of magnetic thin wires is inserted in the vicinity of the affected area of the subject 1 using the attached guide mechanism 25 (step 102). A set of magnetic thin wires 26 inserted into the body is applied with a static magnetic field of the MRI apparatus, and the magnetic field rapidly changes around the thin wires, resulting in a large magnetic field gradient.

  Subsequently, a drug for hyperthermia containing magnetic fine particles is injected into the affected area using the guide mechanism 25 (step 103). In the prior art, the injected drug diffuses and spreads over time, but in one embodiment of the present invention, the magnetic fine particles retain in the vicinity of the affected area due to the large magnetic force generated around the magnetic thin wire. Maintained.

  Next, the frequency of the RF coil is changed, and the excitation coil is changed (step 104). This is to change the frequency or the like in order to heat the magnetic fine particles at high frequency.

  Then, the affected part is heated by heating the magnetic fine particles staying around the affected part with a high frequency magnetic field from outside the subject 1 (step 105). In the prior art, since the drug containing fine particles heated at high frequency diffuses to other than the affected area, there is a high possibility that the surrounding healthy part is heated and killed. However, in one embodiment of the present invention, the site to be treated Can be intensively treated, and the influence on surrounding healthy sites can be suppressed as much as possible.

  In the prior art, since it was necessary to complete the heat treatment before the drug was extremely diffused, the time restriction was large, but the present invention provides a sufficient time for the heat treatment of a specific site. It is possible.

  After a sufficient time for the heating treatment, the frequency of the RF coil is returned to a frequency at which imaging is possible, and the affected area after the heating treatment is imaged by MRI and displayed (step 106). Then, the imaging data of the affected area before the treatment and the imaging data of the affected area after the treatment are compared, and it is determined whether or not cancer cells in the affected area have been confirmed more than predetermined (step 107). In step 107, when cancer cells can be confirmed more than a predetermined amount, the process returns to step 105, and the affected part is heated again by high frequency.

  In step 107, when cancer cells cannot be confirmed more than a predetermined amount, the process proceeds to step 108, and a drug recovery bypass means is installed in the subject 1. As shown in FIG. 7, the bypass means includes a blood flow closing pin 30, a blood vessel bypass 31, and a magnetic body filter 29 disposed in the middle of the blood vessel bypass 31.

Then, the magnetic filter 29 collects the magnetic fine particles bound to the specific cell, that is, the cancer cell (step 109). Subsequently, the form of the affected part is photographed (step 110), and it is determined whether specific cells have been collected based on the photographed image (step 111). If it is determined in step 111 that the specific cell has not been collected, the process returns to step 110.
The magnetic filter 29 and the subject 1 are placed on the same top plate, for example, and when collecting the magnetic fine particles (step 109), the magnetic filter 29 is moved to the center of the static magnetic field, During imaging (step 110), the affected area of the subject is moved to the center of the static magnetic field. Alternatively, the affected part of the subject is always placed in the center of the static magnetic field, and the magnetic filter 29 is placed in a place where there is a sufficiently strong static magnetic field and does not hinder imaging, and recovery (step 109) and imaging (step 110) are performed. ) May be performed simultaneously or alternately.

  If it is determined in step 111 that the specific cell has been collected, in step 112, the bypass means installed in the subject 1 is removed, and the process ends.

  In steps 105 to 107 of the above-described embodiment, it is also possible to compare the imaging information and affected area function information of the cancer affected part before and after the treatment by hyperthermia, and change the heating condition by high frequency based on the comparison result.

  In addition, while checking the image taken by MR by the computer on the computer screen, select and click the tumor part to be treated, and the robot calculates and inserts the insertion angle and depth of the needle (magnetic thin wire) It is also possible to do.

  The shape and size of the magnetic thin wire assembly 26 to be inserted into the treatment site may be arbitrarily selected according to the size of the target portion. If the diameter of the magnetic thin wire is the same, the magnetic force acting on the drug is The retention effect of the magnetic response material 22 per unit length of the thin wire is the same.

  In addition, by inserting this thin line into a cell texture at a specific site, it is possible to treat a tissue at a small site of tens of thousands to thousands.

  In one embodiment of the present invention, the magnetic thin wire assembly 26 is used. However, in order to increase the magnetic force, it is preferable that the wire diameter is small. For this reason, even if it is not a fine wire but a rod-like pattern with a very small diameter deposited on the substrate, for example, the same effect as that of the fine wire can be exhibited.

  In the high-frequency heating by hyperthermia, it is preferable that the irradiation coil for high-frequency heating of the fine particles is also used as the RF irradiation coil used for MR imaging. It is also possible to install.

  It is also possible to attach a magnetic thin wire to a catheter and insert it into an imaging site such as an affected area, and then inject a contrast medium such as gadolinium to concentrate the contrast medium in the imaging site area.

  As described above, according to one embodiment of the present invention, since the uniform magnetic field of the MRI apparatus is used, a large magnetic gradient is obtained, and the magnetic particles are retained in a specific part for a long time. Treatment can be performed and a tomographic image of the treatment site can be displayed using the MR principle.

  Therefore, a magnetic resonance imaging device that can retain magnetic particles in a specific region within the body of a subject for a sufficient time to obtain an effective effect and can confirm the treatment or diagnosis progress of the affected area is realized. can do.

Next, an example of a treatment method using the MRI apparatus according to the present invention will be described.
The magnetic cell separation technique is a technique in which beads made of magnetic particles are combined with cells to be separated by an immune reaction and then separated by an external magnetic force. This technique has a feature that magnetic particles can be selectively combined with a target separated cell.

  Magnetic beads carrying a lectin that separates leukemia cells on the surface of iron oxide fine particles having a diameter of 1 μm or less are prepared and injected into the body of the subject 1 to allow several hours to elapse. Thereby, the magnetic beads are circulated in the body to treat the leukemia cells and the magnetic beads.

  Thereafter, an operation for providing bypass means to the patient is performed, and blood is bypassed into the filter. The magnetic thin wire is a ferromagnetic stainless steel wire having a diameter of 0.01 to 0.05 mm.

Thereafter, a bypass circuit including the subject 1 and the magnetic filter is placed inside the MRI apparatus. The magnetic field strength in the imaging space of the MRI apparatus is 0.7T. The sponge-like filter is applied with the static magnetic field of the MR1 device, and the magnetic field rapidly changes around the stainless steel wire arranged therein, thereby generating a magnetic field gradient of ¹ × ^{10 10} A / m ² .

  In this state, the blood of the subject 1 is caused to flow through the bypass circuit 31 and pass through the inside of the filter 29 by the blood flow closing pin. As a result, fine particles (magnetic beads) combined with leukemia cells circulating in the body of the subject 1 with blood are concentrated around the magnetic thin wire 21 by magnetic force.

  Therefore, after removing the subject 1 from the MRI apparatus, the blood flow closing pin 30 is removed to bring the blood of the subject 1 into a normal state, and then the filter 29 in which magnetic beads are concentrated is removed together with the bypass circuit 31. To do.

  Thereby, leukemia cells in the subject 1 can be efficiently extracted and removed outside the body. According to experiments, 98% of the initially injected magnetic particles can be recovered from the body of the subject 1 together with leukemia cells.

  It is also possible to separate and extract red blood cells in blood by the same method as described above. In addition, the environmental hormone can be separated from the liquid by immobilizing a linear alkyl group and hydrophobizing it so that the environmental hormone and the like are easily adsorbed on the surface of the magnetic iron oxide fine particles.

  In addition, according to the present invention, it is also possible to directly isolate and extract bacteria and bacteria exhibiting a magnetic response.

  In the above-described example, the magnetic beads carrying lectins for separating leukemia cells are used to inject directly into the subject. However, blood is taken out from the subject 1 in advance, and the magnetic filter is used. It is also possible to perform cell separation using a magnetic gradient by placing it in a static magnetic field space of an MRI apparatus.

  It is also effective to provide a mechanism that can hold the aggregate of magnetic thin wires at the distal end of the catheter instead of the guide mechanism 25 described above, and to access the treatment target site via the patient's blood vessel.

1 is an overall schematic configuration diagram of a magnetic resonance imaging apparatus (MRI apparatus) to which the present invention is applied. It is a principle explanatory view of the present invention. It is a principle explanatory view of the present invention. It is a principle explanatory view of the present invention. 1 is a schematic perspective view of an MRI apparatus according to an embodiment of the present invention. It is a schematic block diagram of a guide mechanism. It is a schematic block diagram of a bypass means. It is an operation | movement flowchart of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Subject 2 Static magnetic field generator 3 Gradient magnetic field generation system 4 Sequencer 5 Transmission system 6 Reception system 7 Signal processing system 8 CPU
DESCRIPTION OF SYMBOLS 9 Gradient magnetic field coil 10 Gradient magnetic field power supply 11 High frequency transmitter 12 Modulator 13, 15 Amplifier 14 High frequency coil 16 Quadrature phase detector 17 A / D converter 21 Magnetic substance wire 22 Magnetic response substance 24 Table (bed)
25 Guide mechanism 26 Aggregation of magnetic thin wires 27 Grasp mechanism 28 Through hole 29 Magnetic filter 30 Blood flow closing pin 31 Blood vessel bypass

Claims (4)

Static magnetic field generation means, gradient magnetic field generation means, high-frequency transmission coil, high-frequency reception coil, and image reconstruction means for reconstructing a tomographic image of a subject based on a nuclear magnetic resonance signal received by the high-frequency reception coil In the magnetic resonance imaging apparatus comprising the gradient magnetic field generation means, the high frequency transmission coil, the high frequency reception coil, and the operation control means for controlling the operation of the image reconstruction means,
A magnetic body element inserted into the body of a subject, and a guide mechanism having a through hole for injecting a drug for thermal treatment,
The operation control means includes a portion where the magnetic element is inserted after the magnetic element is inserted into the subject and a high-temperature therapeutic agent is injected, and then the high-frequency transmission coil transmits a high frequency to the subject. A magnetic resonance imaging apparatus comprising: means for heating   The magnetic resonance imaging apparatus according to claim 1, wherein the operation control unit picks up a tomographic image of the part before heating the part where the magnetic body element is inserted, and also detects the tomographic part of the part after heating the part. A magnetic resonance imaging apparatus characterized in that an image is picked up, images before and after the heat treatment are compared, and the heating means is controlled in response to a change in a predetermined portion of the part.   2. The magnetic resonance imaging apparatus according to claim 1, wherein said subject and a drug recovery means for recovering said drug from said subject using said static magnetic field generated by said static magnetic field generating means are alternately arranged in said static magnetic field. A magnetic resonance imaging apparatus comprising: means for alternately performing drug collection and tomographic imaging of the subject; and means for determining whether the drug has been collected from the tomographic image. The magnetic resonance imaging apparatus according to claim 1, wherein the magnetic element is a thin line made of a ferromagnetic material.

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