JP3182854B2 - MRI endoscope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nuclear magnetic field for measuring a nuclear magnetic resonance (hereinafter, referred to as NMR) signal from hydrogen, phosphorus or the like in an object to visualize a nuclear density distribution or a relaxation time distribution. The present invention relates to an MRI endoscope which can be inserted or penetrated into a living body among MRI probes used for a resonance apparatus.

[0002]

2. Description of the Related Art Conventionally, in a nuclear magnetic resonance apparatus (hereinafter, referred to as an MR apparatus), the influence of various movements of a head coil, an abdomen coil and a heart surrounding a site of interest of a subject (for example, a person). Inspection of the subject using a surface coil etc.
Imaging has been performed.

[0003] These coils cannot image minute parts in a living body with high sensitivity and high spatial resolution. As a method for achieving this, there is an MRI endoscope for insertion into the body. Generally, an MRI endoscope is a small MRI probe that can be inserted or penetrated into the stomach, esophagus, intestine, blood vessels, etc. of a living body. A rectal MRI endoscope is disclosed, for example, in Japanese Patent Application Laid-Open No. 2-277440. FIG. 2 shows an example of a conventional MRI endoscope.

[0004]

From the MRI principle, MR
The high-frequency magnetic field detected by the I-probe is a component orthogonal to the static magnetic field direction. The MRI probe detects this most efficiently when the direction of the magnetic field detected by the MRI probe is orthogonal to the static magnetic field. However, since the arrangement of the MRI endoscope to be inserted into the living body is determined by the shape of the target part and the direction of the region of interest, the relative direction to the static magnetic field is not always constant. Therefore, since the arrangement of the endoscope is not optimal for the static magnetic field at the time of actual imaging in the endoscope-based MRI, the S / N of the detection signal is reduced, and the image quality of the reconstructed image may be reduced.

[0005] An object of the present invention is to provide an MRI endoscope that can always connect high-quality images.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an MRI endoscope having three orthogonally crossing points.
There are three mutually orthogonal coils for generating or receiving high frequency magnetic fields in different directions. The apparatus further comprises means for selecting any two of the three orthogonal coils, adjusting the phase or amplitude of each signal, and then synthesizing the signals. Preferably, the selection of the two coils is This is achieved by having means for selecting the combined signal to be the largest combination of all the coil combinations.

[0007]

Since there are three coils orthogonal to each other for generating or receiving a high-frequency magnetic field in three directions orthogonal to each other, even if the MRI endoscope is in any direction with respect to the static magnetic field, the optimum coil is used. To obtain the best signal and obtain a high quality MRI image. Furthermore, by selecting two orthogonal coils containing a large amount of orthogonal components with the static magnetic field, adjusting the phase or amplitude, and synthesizing, quadrature detection can be performed in the MRI endoscope, and the image quality of the endoscope image is significantly improved. .

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the embodiment shown in FIG. The coils 1, 2, and 3 are arranged orthogonally so as to detect magnetic fields in the x, y, and z directions, respectively. The coils are shown separated from one another for clarity, but generally the coils are arranged such that the high-frequency magnetic field sensitive regions of the respective coils overlap each other.
Even in this case, each coil has no noise correlation due to its orthogonality. Each coil is, for example, a one-turn resonance type coil or a solenoid type coil including a series capacitor for resonance.

Signals from the respective coils are connected to phase or amplitude adjusters 4, 5, and 6 via cables. These outputs are input to the combiner 10 via the switches 7, 8, and 9, and are combined. The synthesized signal is processed by the signal processing unit 11 and the image processing unit 12 and displayed on the display unit 13. Each of the components 4 to 13 is controlled by the control unit 14. The relative orientation of the static magnetic field 15 with respect to the coil changes depending on the imaging target and the region. Therefore, the static magnetic field 15 is set to H
(X, y, z) and illustrated. This static magnetic field is generally generated by a magnet (not shown) that generates a uniform magnetic field having a strength of about 0.2 to 4.7 T.

Next, a method of imaging will be described. First, before imaging, switch 7 is turned on, switches 8 and 9 are turned off, and coil 1 is turned on.
Is detected. This signal is called an MR signal, and is generated from the subject using a technique known in the field of MRI. Similarly, the outputs of the coils 2 and 3 are sequentially detected. At this time, the amplitude of the amplitude adjuster is the same as that of the coil 1 for both coils. These findings are:
For example, it is recorded in a memory in the image processing unit. The form of the data may be an FID signal before Fourier transform or a profile signal after the transform. Next, the signals are compared and the coil having the largest output is selected. Next, a switch is selected so as to obtain the output of the coil, and imaging is started using a known imaging technique. The obtained signal is subjected to signal processing and image processing and displayed.

When quadrature detection is performed, the output of the unit coil is measured in the same manner as described above, and two coils having a large output are selected by the switch. Thereafter, the phase and amplitude adjusters corresponding to these coils are optimally set to obtain signals. Typically, high image quality can be achieved by setting the phase difference between the two outputs to 90 ° and setting the amplitude ratio to the output ratio of each coil. In this case, two coils having large outputs are selected to produce a composite signal, so that the composite signal is large and the best S / N can be obtained as compared with the combination of the other coils.

The outputs of the three coils may be combined by adjusting the amplitude or phase. In this case, the S / N of the output signal is further improved.

It is desirable that these series of operations are automatically performed by the control unit 14.

In this embodiment, the relationship between the direction of the static magnetic field and the output of the coil is, for example, when the static magnetic field 15 is in the x direction (ie, H
(x, 0, 0)), an output is generated in the coil orthogonal to this, that is, the coil 2 in the y direction and the coil 3 in the z direction, and no output is generated in the coil 1 in the x direction. Similarly, other arbitrary directions can be decomposed into three orthogonal components.

Further, the phase and amplitude adjustment may be performed in an analog manner or in a digital manner.

[0016]

According to the present invention, since the MRI endoscope has three mutually orthogonal coils for generating or receiving a high-frequency magnetic field in three directions orthogonal to each other, the MRI endoscope is insensitive to the static magnetic field. Even in an arbitrary direction, the optimum coil that can obtain the best signal can be selected, and the image quality of the MRI image does not deteriorate. Furthermore, by selecting two or more orthogonal coils that include many orthogonal components with the static magnetic field, adjusting the phase or amplitude, and combining them, quadrature detection can be performed with the MRI endoscope, and the image quality of the endoscope image is remarkable. improves.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is an explanatory view showing a conventional example.

[Explanation of symbols]

 1, 2, 3 ... coil, 10 ... synthesizer.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Yoshikuni Matsunaga, Inventor, Central Research Laboratory, Hitachi, Ltd. 1-280, Higashi-Koikekubo, Kokubunji-shi, Tokyo (72) Inventor Etsuji Yamamoto 1-1280, Higashi-Koikekubo, Kokubunji-shi, Tokyo Hitachi, Ltd. (56) References JP-A-64-49548 (JP, A) JP-A-63-270038 (JP, A) JP-A-3-231638 (JP, A) JP-B-2-61252 (JP) , B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) A61B 5/055 A61B 1/00 300 G01R 33/36 JICST file (JOIS)

Claims (1)

(57) [Claims] 1. A high-frequency magnetic field in three directions orthogonal to each other is generated.
Or three coils that are orthogonal to each other to receive,
Detected by two of the coils selected from the two coils
Means for obtaining a synthesized signal by synthesizing the obtained signal,
The composite signal is the largest of all the coil combinations
An endoscope for MRI , wherein the two coils are selected so that