JPH0260634A - Magnetic resonance imaging device - Google Patents

Abstract

PURPOSE:To shorten photographing time by detecting a magnetic resonance signal from mixture in a slice part close to a surface coil, suppressing another magnetic resonance signal from fat, and collecting slice picture information intersecting orthogonally with a slice surface. CONSTITUTION:A first sequence executing means 14 executes a pulse sequence accordant with a spin echo method in which cycling time and echo time for detecting the magnetic resonance signal from the moisture in a slice part 17 close to a surface coil 3 and suppressing the magnetic resonance signal from the fat are set longer than usual. Simultaneously, a second sequence executing means 15 executes another pulse sequence accordant with the spin echo method in which cycling time and echo time for collecting the slice picture information of a slice part 16 intersecting orthogonally with a slice surface 17a of the slice part 17 are set shorter than usual.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to magnetic resonance (1'lR:ma)
The present invention relates to a magnetic resonance imaging apparatus that obtains slice image information of a subject (living body) by utilizing the phenomenon (sonance), and particularly relates to a magnetic resonance imaging apparatus capable of extracting brain surface structure.

(Prior art) Magnetic resonance is a phenomenon in which an atomic nucleus with non-zero spin and magnetic moment placed in a static magnetic field resonantly absorbs and releases only electromagnetic waves of a specific frequency. It resonates at the angular frequency ω0 (ωo=2πν0; si0=Larmor frequency) shown in FIG.

ω0 = γ t10 Here, T is the gyromagnetic ratio specific to the type of atomic nucleus,
Ho is the static magnetic field strength.

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

Collecting slice image information by magnetic resonance can excite all parts of a subject placed in a static magnetic field and collect signals, but there are limitations in the equipment configuration and the difficulty of imaging images. Due to clinical requirements, the actual device excites a specific region and collects its signals.

Here, we will discuss the fourth aspect of conventional magnetic resonance imaging equipment.
This will be explained with reference to the figures.

The magnetic resonance imaging apparatus shown in the figure has a magnet 1 that can accommodate a subject P therein.
~ As an assembly, a static magnetic field coil 1 using a normal conduction or superconducting method, a gradient magnetic field generating coil 2 for generating a gradient magnetic field for imparting position information of the induced site of a magnetic resonance signal, and a rotating high-frequency magnetic field for transmitting and It has a surface coil 3 which is a transmission/reception system for detecting the induced magnetic resonance signal (MR multiplied signal. Here, the surface coil 3
is arranged with its hole facing the side of the head PH of the subject P and close to it.

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

Y-axis and Z-axis gradient magnetic field power supplies 5, 6, 7, transmitter 8, receiver 9, sequence 1 for implementing a pulse sequence described later
0. A computer system 11, a display 12, etc. that controls these, detects magnetic resonance signals from moisture in a region close to the surface coil 3, suppresses magnetic resonance signals from fat, and displays them. It is equipped with

The operation of a conventional magnetic resonance imaging apparatus having such a configuration will be explained with reference to FIGS. 5 and 6.

First, as shown in FIG. 5, the hole of the surface coil 3 is placed close to the side of the head PH of the subject P, and in this state, the spin echo method (SE method) shown in FIG. Run the sequence. That is, as shown in FIG. 6, a 90-degree pulse and a not-illustrated slice region determining gradient magnetic field (in this case, on the X axis) are applied. In this case, as shown in FIG. 6, the gradient magnetic field conditions are set so that about half of the head PH becomes the excitation slice site. Then, a 180-degree pulse and a gradient magnetic field (not shown) for encoding and reading (Y and Z axes in this case) are applied, and the time is longer than usual, for example, 2.
50m5ec (Normally less than 100 seconds)
With the echo time Je set to , echo signals are collected as shown in FIG. Then, the echo pulse repetition time Tr is set longer than usual, for example, 2000 m5ec (usually 100msec or less).
The above pulse sequence is repeatedly executed.

By the above-described sequence, cerebral sulci are extracted without overlap with other cerebral sulci on the display 12, and tomographic image information that clearly shows the positional relationship between the brain surface and the lesion can be obtained. This method is called the brain surface structure extraction method (Surf
ace Anatomy 5can, 5AS), and is effective for obtaining three-dimensional slice image information of a target region of a subject.

(Problems to be Solved by the Invention) However, with the magnetic resonance imaging apparatus described above, although it is possible to obtain slice image information in which the positional relationship between the brain surface and the lesion area is clear, the slice region from which the slice image information was obtained is It is not possible to obtain slice image information in a direction perpendicular to the direction. That is, since the thickness of the sliced portion is several centimeters, it is often unclear how deep inside the brain the lesion is located.

Therefore, conventionally, in order to obtain slice image information at a slice site perpendicular to the slice plane of the slice site from which the slice image information was separately obtained, it was necessary to separately perform tomographic imaging again. This often leads to the problem that the photographing time becomes longer and the operation is complicated.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a magnetic resonance imaging apparatus that reduces imaging time and is easy to operate.

[Structure of the Invention] (Means for Solving the Problems) The structure of the present invention for achieving the above-mentioned object is that, in the above-described magnetic resonance imaging apparatus, magnetic resonance from moisture in the sliced region adjacent to the surface coil is suppressed. a first sequence execution unit that executes a sequence for detecting signals and suppressing magnetic resonance signals from fat; and a second sequence execution unit that executes a sequence for collecting slice image information of a slice site perpendicular to the slice plane. The system is equipped with sequence execution means. In this case, the first sequence execution means detects the magnetic resonance signal from the water in the sliced area close to the surface coil, and suppresses the magnetic resonance signal from the fat content for a longer than usual repetition time and echo time. In addition to executing the set pulse sequence using the spin echo method, the second sequence execution means executes the spin echo method with a repetition time and echo time set shorter than usual to collect slice image information of a slice site perpendicular to the slice plane. Alternatively, a pulse sequence may be executed according to the following.

(Function) The function of the present invention having the above-mentioned configuration is to detect a magnetic resonance signal from moisture in a sliced area close to a surface coil,
In addition, since a sequence for suppressing magnetic resonance signals from fat components and a sequence for collecting slice image information of a slice site perpendicular to the slice plane are executed, slice image information for both slice sites is collected at once. We are trying to make sure that you can get the following.

Therefore, it is possible to shorten the pupil shadow time and provide a magnetic resonance imaging apparatus that is easy to operate.

(Example) The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a magnetic resonance imaging apparatus as an example, and FIGS. 2(a) to 2(d) are timing charts of first and second sequence execution means, which will be described later.
FIG. 3 is an explanatory diagram of the obtained slice image information. Note that the magnetic resonance imaging apparatus shown in this example and the fourth
Since the magnetic resonance imaging apparatus shown in the figure has a similar configuration, the same reference numerals are given to the same parts as those explained in Fig. 4, and the explanation thereof is omitted. Explain the differences.

The main difference between the magnetic resonance imaging apparatus shown in FIG. 1 and the magnetic resonance imaging apparatus shown in FIG. 4 is in the sequencer 13 connected to the computer system 11.

The sequencer 13 shown in FIG. 3 executes a sequence for detecting magnetic resonance signals from moisture in the sliced region 17 near the surface coil 3 shown in FIG. 3 and suppressing magnetic resonance signals from fat. The second sequence execution means 15 functions as an execution means 14 and a second sequence execution means 15 that executes a sequence for collecting slice image information of the slice region 16 perpendicular to the slice plane 17a of the slice region 17.

Specifically, the first sequence execution means 14 detects the magnetic resonance signal from the moisture in the slice region 17 adjacent to the surface coil 3 and suppresses the magnetic resonance signal from the fat component by setting a repetition time and an echo time. At the same time, the second sequence execution means 15 executes a pulse sequence based on the spin echo method in which the pulse sequence is set to be longer than usual, and at the same time, the second sequence execution means 15 executes a pulse sequence using the spin echo method, in which the pulse sequence is set to be longer than usual.
A pulse sequence is executed using a spin echo method in which the repetition time and echo time for collecting slice image information are set shorter than usual.

That is, as shown in FIGS. 2(a) to 2(d), the first sequence execution means 14 sets the repetition time Tr and the echo time Te longer than usual in the same manner as described above; In this embodiment, the sequence execution means 15 has a repetition time Tr' for collecting slice image information of the slice region 16 perpendicular to the slice plane 17a of the slice region 17 within the repetition time Tr of the first sequence execution means 14. A pulse sequence based on the spin echo method, which is set to be shorter than usual and consists of an echo time Te' and an echo time Te', is executed.

Note that the first sequence execution means 14. The second sequence execution means 15 executes a pulse sequence of the spin echo method, but is not limited to this, and may be a field echo method, for example.

The operation of the magnetic resonance imaging apparatus having the above configuration,
Explain the effects.

Incidentally, since the pulse sequence of the first sequence execution means 14 shown in this embodiment is the same as that shown in FIG. 6, the pulse sequence of the second sequence execution means 15 will be mainly explained here.

By executing the same sequence shown in FIGS. 2(a) and 2(b) as described above, approximately half of the head PH shown in FIG. With the echo pulse repetition time Tr set to 2000 m5ec, water is sufficiently recovered during the echo pulse repetition time Tr, so the signal strength obtained by 1q is large. Also, the time may be longer than usual, for example 25 minutes.
With the echo time Te set to 0 m5ec, the signal from the fat component is suppressed.

Here, the second sequence execution means 15 performs a repetition time T within the repetition time lr of the first sequence execution means 14.
A pulse sequence based on the spin echo method with the echo time Te' and the echo time Te' set shorter than usual is repeatedly executed. That is, FIG. 2(C).

A slice region determining gradient magnetic field (in this case, Y-axis) (not shown) is applied together with a 90-degree pulse as shown in (d).

Next, a 180° pulse and a gradient magnetic field for encoding and reading (not shown) (in this case, Z and X axes) are applied, and with an echo time Te′ set shorter than usual,
Echo signals are collected as shown in FIG. 4(d).

Note that the repetition time Tr' and the echo time le' may be appropriately set in consideration of the degree of T1 emphasis, the number of repetitions of the pulse sequence, and the like.

As described above, in this embodiment, it is possible to shorten the imaging time, and also to collect slice image information of the slice region 16 perpendicular to the slice plane 17a of the slice region 17, so that the T1-weighted image is can get. This makes it possible to determine how deep inside the brain the lesion is located.

Roughly speaking, when the pulse sequence is repeatedly executed, multiple slice image information is obtained according to the number of repetitions, so even if the lesion is difficult to find, it can be easily found in a short time. become able to. Furthermore, unlike the conventional method, there is no need to perform another tomographic image copying process, making the operation extremely easy.

It should be noted that the present invention is not limited to the above embodiment,
Various modifications can be made within the scope of the gist.

[Effects of the Invention] According to the present invention described in detail above, it is possible to shorten the imaging time and provide a magnetic resonance imaging apparatus that is easy to operate.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a block diagram showing the configuration of a magnetic resonance imaging apparatus as an embodiment of the present invention, and FIGS. 2(a) to (d)
) is a timing chart of the pulse sequence of the first and second sequence execution means, FIG. 3 is an explanatory diagram showing the arrangement of tomographic planes of the subject's head, and FIG. 4 is a diagram showing the configuration of a conventional magnetic resonance imaging apparatus. FIG. 5 is an explanatory diagram showing the arrangement of tomographic planes of the subject's head in the conventional apparatus, and FIG. 6 is a timing chart showing the pulse sequence by the spin echo method in the conventional apparatus. 3...Surface coil, 14...First sequence execution means, 15...Second sequence execution means, 17a...Slice surface, P...Subject, PH...Subject head Department. Figure Figure

Claims (3)

[Claims] (1) Magnetic resonance that is arranged near the head of a subject placed in a static magnetic field and is equipped with a surface coil capable of detecting magnetic resonance signals induced from the subject, and obtains slice image information of the induced slice site. In the imaging apparatus, a first sequence execution means for executing a sequence for detecting a magnetic resonance signal from moisture in a sliced area close to the surface coil and suppressing a magnetic resonance signal from a fat area, and the sliced surface and second sequence execution means for executing a sequence for collecting slice image information of a slice site perpendicular to the second sequence execution means. (2) Magnetic resonance that is provided with a surface coil that is placed near the head of a subject placed in a static magnetic field and capable of detecting magnetic resonance signals induced from the subject, and obtains slice image information of the induced slice site. In an imaging device, a spin echo method in which a repetition time and an echo time are set longer than usual for detecting magnetic resonance signals from water in a sliced region close to the surface coil and suppressing magnetic resonance signals from fat. a first sequence execution means for executing a pulse sequence according to the present invention; and a pulse sequence according to a spin echo method in which a repetition time and an echo time for collecting slice image information of a slice site perpendicular to the slice plane are set shorter than usual. A magnetic resonance imaging apparatus comprising: second sequence execution means. (3) The second sequence execution means takes a repetition time and an echo time longer than usual to collect slice image information of a slice site orthogonal to the slice plane within the middle of the pulse sequence repetition time of the first sequence execution means. 3. The magnetic resonance imaging apparatus according to claim 2, wherein a pulse sequence based on a spin echo method is executed in which the pulse sequence is set to be short.