JP2763109B2 - Magnetic resonance imaging equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to morphological information such as a tomographic image of a subject (living body) using magnetic resonance (MR) development and spectroscopy. The present invention relates to a magnetic resonance imaging apparatus for obtaining functional information such as scopies, and more particularly to a magnetic resonance imaging apparatus capable of extracting a brain surface structure.

(Prior Art) Magnetic resonance development is a development in which nuclei having a non-zero spin and magnetic moment placed in a static magnetic field resonately absorb and emit only electromagnetic waves of a specific frequency. Ω ₀ (ω ₀ = 2πν ₀ ; ν ₀ =
(Larmor frequency).

ω ₀ = γH ₀ where γ is the gyromagnetic ratio specific to the type of nucleus, and H ₀ is the static magnetic field strength.

An apparatus for performing a living body diagnosis using the above principle processes an electromagnetic wave having the same frequency induced above after the above-described resonance absorption, and performs a nuclear processing, a nuclear relaxation time, a longitudinal relaxation time T ₁ , and a transverse relaxation time T ₁ .
_2. Diagnostic information reflecting information such as flow, chemical shift, etc., such as tomographic images of the subject, is obtained non-invasively.

The collection of diagnostic information by magnetic resonance can excite all parts of a subject placed in a static magnetic field and collect signals. In view of the above requirements, an actual device is configured to excite a specific portion and collect its signal.

Here, a conventional magnetic resonance imaging apparatus will be described with reference to FIG.

The magnetic resonance imaging apparatus shown in FIG. 1 includes a static magnetic field coil 1 of normal or superconducting type and a position of an induction site of a magnetic resonance signal as a magnet assembly capable of accommodating a subject P therein. A gradient magnetic field generating coil 2 for generating a gradient magnetic field for providing information and a surface coil 3 which is a transmission / reception system for transmitting a rotating high frequency magnetic field and detecting an induced magnetic resonance signal (MR signal). Have. 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 mainly includes a supply control system for the refrigerant and controls the energization of a static magnetic field power supply, and an X-, Y-, and Z-axis gradient magnetic field power supply
5, 6, 7, a transmitter 8, a receiver 9, a sequence 10 for executing a pulse sequence described later, and controlling these, and detecting a magnetic resonance signal from moisture in a portion close to the surface coil 3, and A computer system 11, a display 12, and the like for suppressing a magnetic resonance signal from fat and displaying the signal are provided.

The operation of the conventional magnetic resonance imaging apparatus having such a configuration will be described with reference to FIGS. 2, 3 (a) and 3 (b).

First, as shown in FIG. 2, the hole of the surface coil 3 is arranged close to the top of the head PH of the subject P, and in this state, the sequence by the spin echo method (SE method) shown in FIG. Execute That is, as shown in FIG. 3 (a), a slice field determining gradient magnetic field (in this case, the X-axis) is applied together with the 90-degree pulse together with the pulse. In this case, as shown in FIG. 2, the conditions of the gradient magnetic field are set so that about half of the head PH becomes the excitation slice site. Then, a 180-degree pulse and a not-shown encoding and reading gradient magnetic field (in this case, the Y and Z axes) are applied, and the time is made longer than usual, for example, 250 minutes.
An echo signal is collected with an echo time Te set to msec (usually 100 msec or less) as shown in FIG. 3 (b). And longer time than usual, for example 2000msec
The above pulse sequence is repeatedly executed at the echo pulse repetition time Tr set to (usually 1000 msec or less).

By executing the above sequence, almost half of the head PH shown in FIG. 2 is determined as the excitation slice site, and the moisture is reduced by the echo pulse repetition time Tr set to be longer than usual, for example, 2000 msec. , The signal strength obtained is large. Also,
The signal from fat is suppressed by the echo time Te set to be longer than usual, for example, 250 msec.

By the above-described sequence, the cerebral sulcus is extracted on the display 12 without duplication, and diagnostic information with a clear positional relationship between the brain surface and the lesion can be obtained. Such a method is a method for extracting and imaging brain surface structure (Surfac
e Anatomy Scan, SAS), which is effective for obtaining diagnostic information of a three-dimensional target site of a subject.

(Problems to be Solved by the Invention) However, in the images obtained by the above-mentioned brain surface structure extraction and imaging method, cerebrospinal fluid (Cerebrospina) existing in the cerebral sulci
l Fluid; CSF) is displayed in white, and has a contrast different from the state where the brain surface is actually observed from the outside.

Therefore, when performing treatment, it gives the practitioner an impression different from what is displayed on the display 12 and the actual brain, which may require a long treatment time and prevent accurate surgery. Can be

Therefore, an object of the present invention is to provide a magnetic resonance imaging apparatus in which a difference between an actual brain surface state and a brain surface state displayed on a display or the like is small.

[Constitution of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a magnetic resonance induced near the head of a subject placed in a static magnetic field. A magnetic resonance imaging apparatus comprising a detection coil for detecting a signal, and imaging a brain surface of the subject by executing a predetermined pulse sequence. Sequencer for executing a pulse sequence that emphasizes a magnetic resonance signal from the subject and suppresses a magnetic resonance signal from fat in the sensitivity region, and image reconstruction means for reconstructing an image based on the magnetic resonance signal obtained by the sequencer Sign inverting means for inverting the sign of each pixel value output from the image reconstructing means; and A magnetic resonance imaging apparatus characterized by comprising a display means for displaying the Ku magnetic resonance image.

(Operation) The operation of the present invention having the above-described configuration is such that by inverting the sign of each pixel value output from the image reconstructing means, the actual brain surface state and the brain surface state displayed on a display or the like are inverted. Can be obtained.

(Example) Hereinafter, the present invention will be described with reference to the drawings. First
FIG. 1 is a block diagram showing a configuration of a magnetic resonance imaging apparatus as one embodiment. The magnetic resonance imaging apparatus shown in the present embodiment and the magnetic resonance imaging apparatus shown in FIG. 4 have almost the same configuration, and therefore, the same reference numerals are given to the same elements as those described in FIG. The description is omitted here, and the main differences will be described here.

The main difference between the magnetic resonance imaging apparatus shown in FIG. 1 and the magnetic resonance imaging apparatus shown in FIG.
At 13. In this embodiment, the computer system 11
Is connected to a keyboard 14 which can select the sign inversion means.

In the present embodiment, the computer system 11 controls each part of the apparatus, detects a magnetic resonance signal from moisture in a portion close to the surface coil 3, and suppresses a magnetic resonance signal from fat. And a function as image reconstructing means for performing image reconstructing processing based on the detection signal, and a sign inverting means 13 is provided for each pixel value of an image transmitted from the computer system 11 as the image reconstructing means. Is inverted, and the image with the inverted sign is displayed on the display 12 connected to the subsequent stage.

The operation and effect of the magnetic resonance imaging apparatus having the above configuration will be described.

As shown in FIG. 2, the surface coil 3 is arranged such that its hole faces the top of the head PH of the subject P and is close to it. In this state, the spin echo method (SE method) shown in FIG. ). That is, as shown in FIG. 3 (a), a gradient magnetic field (in this case, the X axis) for determining a slice portion is applied together with a 90 ° pulse, not shown. In this case, as shown in FIG. 2, the condition of the gradient magnetic field is set so that about half of the head PH becomes the excitation slice site. Then, a 180 ° pulse and a not-illustrated encoding and reading gradient magnetic field (in this case, the Y and Z axes) are applied, and the echo time is set to be longer than usual and set to, for example, 250 msec (usually 100 msec or less). Echo signals are collected by Te as shown in FIG. 3 (b). Then, the time is longer than usual, for example, 2000 msec (usually 1000 msec or less)
The above-described pulse sequence is repeatedly executed at the echo pulse repetition time Tr set in (1).

By executing the above sequence, about half of the head PH shown in FIG. 2 is determined as the excitation slice site, and the moisture is reduced by the echo pulse repetition time Tr set to be longer than usual, for example, 2000 msec. , The signal strength obtained is large. Also, the signal from fat is suppressed from the echo time Te which is longer than usual and is set to, for example, 250 msec.

According to the above, a signal is obtained from the water in the cerebral sulcus in the same manner as described above. The signal is suppressed, and the echo time Te whose time is set longer than usual also suppresses the signal mainly due to fat from the surface layer structure such as the interplate layer and subcutaneous fat.

Based on such signals, an image is reconstructed in the computer system 11 as the image reconstructing means. Here, the operator selects a positive / negative display of an image to be displayed on the display 12 by operating a switch (not shown) on the keyboard 14.

If you select positive, the computer system
The image output from 11 is displayed on display 12 as it is. Therefore, in this case, the cerebrospinal fluid turns white as in the case of the conventional display image.

On the other hand, when negative is selected, the sign of each pixel value of the reconstructed image to be output is inverted by the above-described sign inverting means 13 connected to the subsequent stage of the computer system 11. As a result, the cerebrospinal fluid is displayed in black on the display 12, has a three-dimensional contrast similar to a state where the brain surface is actually observed from the outside, and an image having a small difference from the actual brain surface state is obtained. Therefore, according to such a surface image, an accurate operation can be performed without requiring a long treatment time.

In this way, the cerebral sulcus is drawn on the display 12 without overlapping, and the positional relationship between the brain surface and the lesion is clear, and clinically extremely useful diagnostic information can be presented.

By the way, although the sequence by the spin echo method (SE method) is shown in the above embodiment, the present invention is not limited to this. For example, the method using the inversion recovery method (IR method), An image obtained by the inverse recovery method and an image obtained by the spin echo method are obtained, and an image obtained by the spin echo method is subtracted from the image obtained by the inversion recovery method.
A device that suppresses a signal from fat can also be applied. Even in the case of such a sequence, the same effect as in the above embodiment can be obtained.

Note that the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the gist.
For example, in the above-described embodiment, the case of displaying on the display has been described, but the same effect can be obtained when printing out with a printer or the like.

[Effects of the Invention] According to the present invention described in detail above, it is possible to provide a magnetic resonance imaging apparatus having a small difference between an actual brain surface state and a brain surface state displayed on a display or the like.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a magnetic resonance imaging apparatus as one embodiment of the present invention, FIG. 2 is an explanatory diagram showing a positional relationship between a surface coil and a subject's head, and FIGS.
4B is a timing chart showing a pulse sequence by the spin echo method, and FIG. 4 is a block diagram showing a configuration of a conventional magnetic resonance imaging apparatus. 3 Surface coil 11 Image reconstruction means and control means 13 Sign reversal means PH Head of subject.

Claims (1)

(57) [Claims] A detection coil disposed near a head of the subject placed in a static magnetic field and detecting a magnetic resonance signal induced from the subject; and executing a predetermined pulse sequence to execute the predetermined pulse sequence. What is claimed is: 1. A magnetic resonance imaging apparatus for imaging a brain surface of a subject, wherein the magnetic resonance signal is a sensitivity region of the detection coil, the magnetic resonance signal from moisture in the sensitivity region being emphasized, and the magnetic resonance signal from fat in the sensitivity region. Sequencer for executing a pulse sequence for suppressing the noise, image reconstructing means for reconstructing an image based on a magnetic resonance signal obtained by the sequencer, and inverting the sign of each pixel value output from the image reconstructing means. Sign inverting means, and display means for displaying a magnetic resonance image based on the pixel value whose sign has been inverted by the sign inverting means. Care resonance imaging apparatus.