JP2686066B2 - Magnetic resonance imaging equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to magnetic resonance (MR).
Using the magnetic resonance phenomenon, the density distribution of specific nuclear spins in a specific cross section of the subject (living body)
So-called computed tomography (CT)
MRI for imaging as a CT image (computed tomogram) by the y) method and performing a biopsy on this image
The present invention relates to an apparatus (magnetic resonance imaging apparatus). 2. Description of the Related Art An example of a conventional magnetic resonance imaging apparatus will be described with reference to FIG. That is, in FIG.
A subject P is placed on a bed top (not shown), and the subject P has the uniform static magnetic field generating coils 1A and 1B and the gradient magnetic field generating coil 2 as main elements as a uniform static magnetic field generating device. It is located in the body. In the main body part, the gradient magnetic field generated by the gradient magnetic field generating coil 2 is superimposed on the uniform static magnetic field generated by the uniform static magnetic field generating coils 1A and 1B to form a superimposed magnetic field, and the subject P is placed in this superimposed magnetic field. doing. The transmission / reception coil 3 is applied to the subject P, and the excitation / rotation magnetic field is applied by the transmission / reception coil 3 to cause the subject P to move.
A tomographic image of the subject P at the position where the transmission / reception coil 3 is applied by causing the MR phenomenon to occur in the subject, detecting the induced MR signal by the transmission / reception coil 3, and performing image reconstruction processing by an image processing device (not shown) or the like. The information such as is obtained and the image is displayed. In this case, since the gradient magnetic field generating coil 2 and the transmitting / receiving coil 3 are maintained in such a positional relationship that they are not coupled to each other, noise generated by electromagnetic force due to energization of the gradient magnetic field generating coil 3 is suppressed. The gradient magnetic field generating coil 2 is different from the uniform static magnetic field generating coils 1A and 1B, which are magnetic field forming spaces, in order to obtain a large subject access cavity formed in the magnetic field generating coil 3.
It has a fixed position and is fixed so as to be in contact with the inner circumference. However, the following problems have been raised in such a configuration. That is, this type of magnetic resonance imaging apparatus is not satisfied with the short-time imaging request required as a medical diagnostic apparatus, and requires a relatively long imaging time. One method for solving this is to generate a strong magnetic field to act on a desired imaging region of the subject, to speed up the rising speed, and the like. In order to realize this, the gradient magnetic field generating coil 2 needs to have a small self-inductance, and there are conditions such as reducing the coil diameter, increasing the current, and reducing the number of coil windings. However, these conditions are required for the gradient magnetic field generating coil 2
Is incompatible with the conventional static magnetic field generating coils 1A and 1B in the following point with respect to the conventional configuration in which the coils are fixed at a fixed position and in contact with the inner circumference. That is,
When it is attempted to obtain a large subject access cavity in order to secure a desired imaging region including the whole body, the gradient magnetic field generating coil 2 has a diameter such that it is in contact with the inner circumferences of the uniform static magnetic field generating coils 1A and 1B. There is a need. In this case, the distance between the gradient magnetic field generating coil 2 and the subject becomes large, so the magnetic field that can act on the desired imaging region becomes weak, and it is necessary to increase the size of the gradient magnetic field generating coil 2 in order to strengthen the magnetic field. Yes,
Eventually, the subject access cavity is made smaller. As described above, in the prior art, the gradient magnetic field generator is fixedly installed with a diameter such that it contacts the static magnetic field generator. The intensity of the gradient magnetic field that can be applied to the desired imaging region is weak, and it is not possible to realize the demand for short-time imaging or the like. There was a problem. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to secure a desired subject access cavity and to increase the strength of the gradient magnetic field that can act on a desired imaging region of the subject. It is an object of the present invention to provide a magnetic resonance imaging apparatus capable of fulfilling requirements such as time imaging. The present invention has the following configuration in order to solve the above problems and achieve the object. That is, the magnetic resonance imaging apparatus according to the present invention arranges the subject in the static magnetic field generated by the static magnetic field generator, superimposes the gradient magnetic field generated by the gradient magnetic field generating coil on the static magnetic field, and superimposes the gradient magnetic field. An MR phenomenon is caused in the subject by applying an excitation rotating magnetic field to the magnetic field by the transmitting / receiving coil, the induced MR signal is detected by the transmitting / receiving coil, and image reconstruction processing is performed to perform the image reconstruction of the subject. A magnetic resonance imaging apparatus for obtaining image information is characterized in that an imaging unit in which the transmission / reception coil is mounted inside the gradient magnetic field generation coil is detachably arranged in the static magnetic field. (Operation) According to this structure, since the transmission / reception coil in the photographing unit is attached to the gradient magnetic field generation coil, the positional relationship is set so that the gradient magnetic field generation coil and the transmission / reception coil are not coupled. Can be held. Further, since the photographing unit is detachable in the static magnetic field, a large-diameter photographing unit having a large-diameter gradient magnetic field generating coil and a transmitting / receiving coil can be arranged in the cavity of the static magnetic field generating coil. It becomes possible to arrange a small-diameter imaging unit having a small-diameter gradient magnetic field generating coil and a transmitting / receiving coil.
A large diameter object can be used for a large object, and a small diameter object can be used for a small object. In other words, the gradient magnetic field generating coil having a large diameter and the gradient magnetic field generating coil having a small diameter are used according to the size of the imaging region, and the distance between the imaging region and the gradient magnetic field generating coil can be made sufficiently small. A strong magnetic field can be applied to the adjacent imaging areas. This is because even if it is smaller than the conventional one, it is possible to apply a strong magnetic field to realize short-time photography, and the generated electromagnetic force is small, so that the fixing mechanism can be simplified and low Noise can be realized. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a magnetic resonance imaging apparatus according to the present invention will be described below with reference to the drawings.
FIG. 1 is a perspective view showing the configuration of the same embodiment. In FIG. 1, uniform static magnetic field generating coils 1A, 1B are arranged in a main body 4, and the inner diameters of the uniform static magnetic field generating coils 1A, 1B are hollow as a uniform static magnetic field forming space. There is. A photographing unit 7 to be inserted into the cavity is detachably attached to an end portion of a top plate 6 which is slidable on the bed 5 toward the main body. The imaging unit 7 includes a gradient magnetic field generating coil 7a, a transmission / reception coil 7b which is inserted inside the gradient magnetic field generating coil 2 and is close to an imaging region of a subject, and the gradient magnetic field generating coil and the transmission / reception coil 7b. The gradient magnetic field generation coil 7a and the transmission / reception coil 7b have an appropriate diameter corresponding to a desired imaging region. The gradient magnetic field generation coil 7a and the transmission / reception coil 7b are not shown. Are fixed in such a positional relationship that coupling does not occur. Of course, the apparatus of the present embodiment has a control system and an image processing system (not shown) to control the excitation of the uniform static magnetic field generating coils 1A and 1B and the gradient magnetic field generating coil 7a, and to transmit / receive the transmitting / receiving coil b. Due to
Signal processing of the detection signal is performed so that image information such as a tomographic image can be obtained. Next, the operation of the present embodiment configured as described above will be described. (1) According to this embodiment, the gradient magnetic field generating coil 7a and the transmitting / receiving coil 7A in the imaging unit 7 are
Since b and are fixed in position, the gradient magnetic field generating coil 7
It is possible to set and hold the positional relationship in which a and the transmission / reception coil 7b are not coupled. (2) According to the present embodiment, since the photographing unit 7 is detachably attached to the top plate 6, it can be attached to the cavities of the uniform static magnetic field generating coils 1A and 1B as shown in FIG. Large-diameter gradient magnetic field generating coil 7Aa, transmitting / receiving coil 7A
b, a large-diameter imaging unit having a mount 7Ac can be arranged, and a small-diameter gradient magnetic field generating coil 7Ba,
It becomes possible to arrange a small-diameter imaging unit having a transmission / reception coil 7Bb and a mounting base 7Bc. And the one with a large diameter can be used for a large subject,
The one with a small diameter can be used for a small object to be photographed. That is, since the gradient magnetic field generating coil 7Aa having a large diameter and the gradient magnetic field generating coil 7Ba having a small diameter are used according to the size of the imaging region, the distance between the imaging region and the gradient magnetic field generating coil 7a can be made sufficiently small. A strong magnetic field can be applied to the imaging area close to the generating coil 7a. This is because even if it is smaller than the conventional one, it is possible to apply a strong magnetic field to realize short-time photography, and the generated electromagnetic force is small, so that the fixing mechanism can be simplified and low It becomes possible to realize noise reduction. (3) According to this embodiment, the small-diameter gradient magnetic field generating coil 7 capable of exerting a strong magnetic field on a desired imaging region.
Since a can be adopted, the number of coil windings can be reduced, which can reduce the self-inductance, and the weight can be reduced. Another embodiment of the present invention is shown in FIG. FIG.
The configuration shown in is the uniform static magnetic field generating coil 1A of the main body 4a,
A spacer 8 in which a groove 8a is formed is provided in the cavity of 1B, and an imaging unit 10 of a gradient magnetic field generating coil 9a with a ridge 9a 'corresponding to the groove 8a and a transmitting / receiving coil 9b is provided in the spacer 8.
Is designed to be inserted. According to this configuration, by changing the combination of the spacer 8 and the photographing unit 9 having different diameters, the gradient magnetic field generating coil 9a and the transmitting / receiving coil 9b having various sizes described above can be applied. The present invention is not limited to the above-described embodiment. For example, in addition to the configuration in which the gradient magnetic field generating coil and the transmission / reception coil are fixed together as an imaging unit, the transmission / reception coil is separated from the imaging unit to be portable. It is also possible to carry out various modifications such as the configuration, and of course, as the uniform static magnetic field generation device, other than the configuration using the two electromagnet coils in FIG. 4, one using four or using a permanent magnet, etc. Can be applied, and various modifications can be implemented without departing from the scope of the present invention. As described above, in the magnetic resonance imaging apparatus according to the present invention, the imaging unit in which the transmission / reception coil is mounted in the gradient magnetic field generating coil is detachably arranged in the static magnetic field. Therefore, the coupling between the gradient magnetic field generating coil and the transmission / reception coil can be prevented, the subject access cavity can be secured, and the strength of the gradient magnetic field that can act on the desired imaging region of the subject can be made strong so that short-time imaging etc. It is possible to provide a magnetic resonance imaging apparatus that can meet the above requirements.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing the configuration of an embodiment of a magnetic resonance imaging apparatus according to the present invention. FIG. 2 is a view showing an operation of the same embodiment. FIG. 3 is a diagram showing the configuration of another embodiment of the present invention. FIG. 4 is a diagram showing a configuration of a conventional example. [Description of Reference Signs] 1A, 1B ... Uniform static magnetic field generating coil, 2 ... Gradient magnetic field generating coil, 7 ... Imaging unit, 7a ... Gradient magnetic field generating coil, 7b ... Transmitting / receiving coil, 7c ... Mounting base.

Claims (1)

(57) [Claims] A subject is placed in a static magnetic field generated by a static magnetic field generator, a gradient magnetic field generated by a gradient magnetic field generating coil is superimposed on the static magnetic field, and an excitation rotating magnetic field is applied to the superimposed magnetic field by a transmission / reception coil. In the magnetic resonance imaging apparatus, which causes an MR phenomenon in the subject by detecting the induced MR signal by the transmission / reception coil and obtains image information of the subject by performing image reconstruction processing, A magnetic resonance imaging apparatus, wherein an imaging unit having a coil attached inside the gradient magnetic field generating coil is detachably arranged in the static magnetic field.