JPH01299540A - Magnetic resonance imaging method - Google Patents

Abstract

PURPOSE:To promptly obtain a perspective image showing a detected body for the distribution of its nuclear species by using an excitation magnetic field, containing a magnetic resonance frequency component of the nuclear species contained in an objective location of the detected body, selectively exciting the objective location. CONSTITUTION:A detected body P is arranged in a device, and an excitation magnetic field, overlapping a static magnetic field H from a static magnetic field coil 1, inclined magnetic field Gz in a direction Z by controlling a sequencer 10 and an RF pulse of frequency m corresponding to a magnetic resonance frequency of nuclear species of the detected body P, is applied to a head part pH of the detected body P. Thus selectively exciting any of the sectional regions S1, S2, S3,..., satisfying a relation where omega=gamma, in the head part pH, nuclear species, corresponding to the frequency omegain that sectional area, for instance, the static magnetic field H generates a magnetic resonance phenomenon, inducting an MR signal. Successively executing the action thus obtained while changing the frequency omega, this MR signal is received by a receiver 9 and Fourier transformed in a Fourier transforming part 15, and processing picture creation in a perspective picture creating part further modulating brightness in a brightness modulating part 17, the signal is displayed on a display 12.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention relates to a magnetic resonance imaging method, and more particularly, the present invention relates to a magnetic resonance imaging method that can obtain a fluoroscopic image of a target region of a subject from a desired direction. Resonance imaging method.

(Prior art) Magnetic resonance phenomenon is a phenomenon in which an atomic nucleus with non-zero spin and magnetic moment placed in a static magnetic field resonantly absorbs and emits only electromagnetic waves of a specific frequency. The angular frequency ω0 (ωo=2πshi0.shi0
It resonates at the Niller-More frequency).

ωo = TH where γ is the gyromagnetic ratio specific to the type of atomic nucleus,
Further, H is the static magnetic field strength.

An apparatus that performs biological diagnosis using the above-mentioned principle processes the electromagnetic waves of the same frequency as the above induced after the above-mentioned resonance absorption, and calculates the nuclear density, longitudinal relaxation time TI, transverse relaxation time T2. It is common to non-invasively create a slice image of a subject that reflects information such as flow and chemical shift.

However, when attempting to obtain a fluoroscopic image of a subject using the conventional apparatus described above, image reconstruction processing must be performed based on image information of a large number of slice image groups, and the There is a problem in that a lot of processing time is required to obtain a fluoroscopic image from a desired direction or a fluoroscopic image of each nuclide within a subject, which increases the burden on the operator.

(Problems to be Solved by the Invention) The present invention has been made in view of the above circumstances, and provides a fluoroscopic image of a target region of a subject from a desired direction and a fluoroscopic image showing the distribution of nuclides contained in the target region. The object is to provide a magnetic resonance imaging method that can be obtained rapidly.

[Structure of the Invention] (Means for Solving the Problems) The magnetic resonance imaging method of the present invention includes excitation of a cross-sectional area along a specific direction of a target region of a subject, including magnetic resonance frequency components of nuclides contained in the cross-sectional area. At the same time as applying a readout magnetic field that determines the viewing direction for each selectively excited cross section, magnetic resonance signals from each selectively excited cross section region are obtained, and each of the obtained magnetic resonance signals is By performing signal processing and configuring and displaying a perspective image of each cross-sectional area from the perspective direction,
This is to obtain a perspective image of the target region from a desired direction.

(for production) The operation of the method of the present invention will be explained below.

According to this magnetic resonance imaging method, each cross-sectional region of the target region is selectively magnetically excited by selectively exciting the target region using an excitation magnetic field containing the magnetic resonance frequency components of nuclides contained in the target region of the subject. A resonance phenomenon is caused to induce a magnetic resonance signal.

By reading out each magnetic resonance signal by applying a readout magnetic field that determines the direction of fluoroscopy and subjecting it to further signal processing, fluoroscopic image information reflecting the distribution of the nuclide in each cross-sectional area is obtained. By displaying these, it is possible to obtain a perspective image of the target region from a desired direction and reflecting various distributions.

(Example) An example of the magnetic resonance imaging method according to the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of a magnetic resonance imaging apparatus that can implement the same embodiment.

As shown in Fig. 1, the magnet assembly that can house the subject P inside is a static magnetic field coil (a static magnetic field correction shim coil may be added) using a normal conduction or superconducting method. ) 1, a gradient magnetic field generating coil 2 for generating a gradient magnetic field for imparting positional information of the induced site of the magnetic resonance signal, and a magnetic resonance signal (M
Surface coil 3 which is a transmission/reception system for detecting the R times signal
It has Here, the surface coil 3 is arranged so that its hole faces the side surface of the head PH of the subject P and is close to it.

If the static magnetic field coil 1 is of a superconducting type, the static magnetic field control system 4 includes a refrigerant supply control system and mainly controls the energization of the static magnetic field power supply, and the X axis.

Y-axis and Z-axis gradient magnetic field power supplies 5, 6.7, transmitter 8, receiver 9, and sequencer 10 for implementing the pulse sequence shown in FIG. an image processing unit 13 that receives an output signal based on the magnetic resonance signal from the receiver 9, performs image processing as described below, and outputs the processing result; a display 12 that displays the processing result of the image processing unit 13 as an image; It is equipped with a keyboard 14 having a function of specifying an ROI (specific region) for an image displayed on a display 12, and a control section 11 that controls each of the above-mentioned elements.

The image processing section 13 includes a receiver 9 as shown in FIG.
a Fourier transform unit 15 that performs Fourier transform on the output signal of
It includes a perspective image creation unit 16 that takes in the output signal of the Fourier transform unit 15 and creates perspective image information, and a brightness modulation unit 17 that performs brightness modulation processing on the perspective image information created by the perspective image creation unit 16. are doing.

The sequencer 10 generates an inclination in the Z direction that is superimposed on the static magnetic field H produced by the static magnetic field coil 1 as an excitation magnetic field that selectively excites, for example, the head PH of the subject P along its body axis (Z-axis) direction. The magnetic field Gz and the nuclides in the head PH of the subject P, that is, H and P.

In order to apply an RF pulse having a magnetic resonance frequency ω of Na, Ca, etc. to the head PH of the subject P, the Z-axis gradient magnetic field power supply 7 and the transmitter 8 are controlled respectively.

The sequencer 10 also uses the head PH as a readout magnetic field.
Control for applying a gradient magnetic field Gx in the X-axis direction and a gradient magnetic field GY in the Y-axis direction to the head PH, which determines the perspective direction of
X-axis gradient magnetic field power supply 5. This is performed for each of the Y-axis gradient magnetic field power supplies 6.

Next, FIG. 4 shows the method of this embodiment using this apparatus.

This will be explained with reference to FIG. 5 as well.

First, as shown in FIG. 1, a subject P is placed in this apparatus, and a static magnetic field H from a static magnetic field coil 1 and a sequencer 10
The gradient magnetic field GZ (GZl,...,
QzN), and a frequency ω corresponding to the magnetic resonance frequency of the nuclide in the object P (to excite a cross-sectional area of a constant thickness, ω
An excitation magnetic field superimposed with an RF pulse (including frequency components from −Δω to ω+Δω) is applied to the head PH of the subject P.

As a result, in the head PH, any of the cross-sectional areas 31, 82, S3, ... that satisfy ω = γ (H + GZ) is selectively excited, and the frequency in any of the excited cross-sectional areas is A nuclide corresponding to ω, such as H, causes a magnetic resonance phenomenon and induces a low MR signal.

At this time, at the timing shown in Fig. 3, a gradient magnetic field (3x) with a gradient along the X-axis direction is applied to the head PH. Read out.

After the signal is received by the MR low signal receiver 9 and converted into an electrical signal, it is subjected to Fourier transform in the Fourier transform section 15 to obtain a signal having the profile shown in FIG. Then, based on this signal, the fluoroscopic image creation section 16 performs image creation processing, and the brightness modulation section 17 modulates the brightness and displays it on the display 12. As shown in FIG. A transparent image T1 viewed from the axial direction can be obtained.

By performing such operations one after another while changing the frequency ω, the cross-sectional areas 82 , 33 are formed.

It is possible to obtain perspective images T2, T3, . . . corresponding to .

In addition, in FIG. 5, the distribution of nuclide H is indicated with an O mark.

By applying a gradient magnetic field GY having a gradient along the Y-axis direction to the head PH instead of the gradient magnetic field GX described above,
A perspective image of each cross-sectional area S1, 32, S3, . . . projected from the X-axis direction can be obtained.

Then, a perspective image Tl*T2-T3* from the Y direction
... and the image information of each fluoroscopic image from the It becomes possible to obtain a perspective image projected from the direction.

The present invention is capable of various modifications of the embodiments described above.

For example, in addition to the head PH mentioned above, desired parts of the subject P such as the chest and abdomen can be set as the target parts, and the order of selective excitation of the target parts can also be set by setting the frequency of the RF pulse in the excitation magnetic field. It is possible to create an arbitrary order by changing .

In addition, the above-mentioned fluoroscopic images T1, T2, T3, etc. contain many low-frequency signal components depending on the shape of the object and often make it difficult to see the inside of the object visually, so the low-frequency components are cut. By performing filter processing to display the image on the display, a perspective image with better image quality can be obtained.

[Effects of the Invention] According to the present invention detailed above, a fluoroscopic image of a target region of a subject from a desired direction can be obtained quickly while reflecting the distribution of nuclides, reducing the burden on the operator. It is possible to provide a magnetic resonance imaging method that can reduce the burden.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of an apparatus used to carry out the embodiment method of the present invention, Fig. 2 is a block diagram of the image processing section of the apparatus, and Fig. 3 shows the components of the present measurement method. FIG. 4 is a diagram showing a pulse sequence, FIG. 4 is an explanatory diagram showing cross-sectional regions of the subject to be selectively excited, and FIG. 5 is an explanatory diagram showing perspective images corresponding to each cross-sectional region shown in FIG. 4. 1... Static magnetic field coil, 2... Gradient magnetic field coil, 3...
...Surface coil, 4...Static magnetic field control system, 5...Transmitter, 6...Receiver, 7...X-axis gradient magnetic field power supply, 8...Y-axis gradient magnetic field power supply, 9. ...X-axis gradient magnetic field power supply, 10... sequencer,
11...Control unit, 12...Display, 13.
...Image processing unit, 14...Keyboard. Agent Patent Attorney Norihiro Chika Takeshi Kondo 1 Figure 2

Claims (1)

[Claims] A readout magnetic field that selectively excites a cross-sectional area along a specific direction of the target part of the subject with an excitation magnetic field containing the magnetic resonance frequency component of the nuclide included in the cross-sectional area, and determines the viewing direction for each selectively excited cross-section. is applied to obtain a magnetic resonance signal from each selectively excited cross-sectional area, and each of the obtained magnetic resonance signals is subjected to signal processing to construct and display a fluoroscopic image of each cross-sectional area from the fluoroscopic direction. A magnetic resonance imaging method characterized by obtaining a fluoroscopic image of a target region from a desired direction.