JPH02116353A - Imaging device for brain surface structure by mri device - Google Patents

Abstract

PURPOSE:To obtain a picture to extract brain surface structure by defining the head of a person to be checked as an imaging subject concerning proton, executing a multi- slice method to use a sequence, for which the signal of fat is suppressed and the signal of water is emphasized, and obtaining the picture for display. CONSTITUTION:A head part PH of a person P to be checked is set in the magnetic field center of a magnet assembly MA and a coil 13 for head part is arranged so as to cover the head part PH. A transmitter 5 is driven and the RF pulse of a rotary magnetic field is applied from the coil 13. Then, power sources 7, 8 and 9 are driven and from an inclining magnetic field generating coil 2, inclining magnetic fields Gx, Gy and Gz are applied as the magnetic fields for slice, for phase encode and for read. After that, a signal from a specified spot is collected by the coil 13 for head part. The picture is produced by a data group which is obtained by repeating this sequence by prescribed times. For a pulse sequence to collect the picture, the head part PH of the person P to be checked is defined as the imaging subject concerning the proton. Then, the sequence is executed by a spin echo method or a field echo method, with which the signal of the fat is suppressed and the signal of the water (cerebrospinal fluid) is emphasized, and this sequence is executed by the multi-slice method.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is directed to magnetic resonance (MR)
MR that obtains morphological information and functional information such as spectroscopy of a subject (living body) using the phenomenon (esonance)
The present invention relates to a method for imaging brain surface structures using an I device (magnetic resonance imaging device).

(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 emits only electromagnetic waves of a specific frequency. The angular frequency ω0 (ωo−2πshi0.shi0
; Larmor frequency).

ωoIwγH0 Here, γ is the gyromagnetic ratio specific to the type of atomic nucleus,
Further, Ho 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. Diagnostic information that reflects information such as flow and chemical shift, such as slice images of a subject, can be obtained non-invasively.

Collecting diagnostic 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 clinical requirements for imaging images. Therefore, in an actual device, a specific part is excited and its signal is collected.

In this case, the specific region to be imaged is generally a sliced region with a certain thickness;
Magnetic resonance signals (MR multiplied signals) of echo signals and FID signals from this slice site are collected by performing a data encoding process many times, and these data groups are subjected to image reconstruction processing using, for example, a two-dimensional Fourier transform method. By doing so, an image of the specific slice region is generated.

On the other hand, we will discuss clinical applications realized by using magnetic resonance imaging equipment. In other words, when performing surgical treatment for intracranial diseases, images depicting the brain surface structure, including sensation, are an important guide for knowing the location of lesions localized in the cortex and subcortex, and are important for determining the location of lesions localized in the cortex and subcortex. Accurate position determination is desired, and several attempts have been made to accomplish this using magnetic resonance imaging. An example will be explained below.

One method is to perform normal proton imaging using a head coil. In this method, the head coil has a brush-like shape that wraps around the head, so it collects signals from the entire head, so the image contains information from deep beneath the brain. As a result, the above-mentioned request for diagnosis cannot be fully met.

・Also, there is a method of performing normal proton imaging using a surface coil. In this method, due to the sensitivity characteristics of the surface coil, that is, the areas close to the coil are highly sensitive, only signals from the surface layer, such as subcutaneous fat, are collected, and as a result, the above-mentioned diagnostic requirements are not met. It's not something you can get rid of.

In other words, neither of the above two methods can present an image that accurately represents the brain surface structure.

(Problem 8 to be solved by the invention) In this way, in the conventional technology, signals from cerebral hydration and fat are collected in the same way without distinction, so it is difficult to determine the location of lesions localized in the cortex or subcortex. There was a problem in that it was not possible to obtain brain surface structure images for diagnosis.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for imaging brain surface structures using an MRI apparatus, which can obtain images depicting brain surface structures for diagnosing lesions existing on the brain surface of the head. .

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems and achieve the objects, the present invention has the following structure. That is, claim 1 of the present invention
The configuration involved is a static magnetic field magnet.

In a method of imaging the brain surface structure using an MRI device that has gradient magnetic field coils and transmitting and receiving coils and collects and images signals associated with the magnetic resonance phenomenon of specific atomic nuclei, a cylindrical shape that can wrap around the head is used. A multi-slice method that uses a coil that can perform at least one of transmission and reception, targets the subject's head for proton imaging, and uses a sequence in which fat signals are suppressed and water signals are emphasized. is characterized in that it executes and obtains an image for display.

The structure according to claim 2 of the present invention is a static magnetic field magnet.

In a method of imaging the brain surface structure using an MRI device that has gradient magnetic field coils and transmitting and receiving coils and collects and images signals associated with the magnetic resonance phenomenon of specific atomic nuclei, a cylindrical shape that can wrap around the head is used. A multi-slice method that uses a coil that can perform at least one of transmission and reception, targets the subject's head for proton imaging, and uses a sequence in which fat signals are suppressed and water signals are emphasized. The present invention is characterized in that, at the same time, a predetermined weight is attached to each multi-slice image obtained by this execution, and each slice image to which this weight has been attached is added to obtain an image for display.

The structure according to claim 3 of the present invention is a static magnetic field magnet.

In a method of imaging the brain surface structure using an MRI device that has gradient magnetic field coils and transmitting and receiving coils and collects and images signals associated with the magnetic resonance phenomenon of specific atomic nuclei, a cylindrical shape that can wrap around the head is used. A multi-slice method that uses a coil that can perform at least one of transmission and reception, targets the subject's head for proton imaging, and uses a sequence in which fat signals are suppressed and water signals are emphasized. The present invention is characterized in that it executes the process, adds a predetermined weight to the matrix component of each slice image obtained by this process, adds each weighted slice image to the matrix component, and obtains an image for display. do.

In the configuration according to claim 4 of the present invention, in the configuration according to claim 2 or 3, when adding each slice image,
The feature is that addition is performed while shifting the position of each slice image.

(Function) According to the configuration according to claim 1, each slice region close to the coil, which has a cylindrical shape that can wrap around the head and can perform at least one of transmitting and receiving, is capable of removing water from the water within that region. Since the magnetic resonance signal is enhanced and the magnetic resonance signal from fat is suppressed and detected, it is possible to depict a sensational image of water in the sensation of the head, and since the magnetic resonance signal from fat is suppressed, The image depicted by fat does not overlap with the sensation depicted image by water, and images corresponding to each slice region suitable for diagnosing a lesion existing on the brain surface can be presented. In addition, since it uses a cylindrical coil that can wrap around the head, the object to be photographed (
It is easy to set up the head (head) and the coil, and it is possible to obtain slice images depicting the brain surface structure viewed from any direction.Furthermore, by referring to each image, the positional relationship in the depth direction can be determined. can be easily known.

According to the configurations according to claims 2 and 3, the effects of the configuration according to claim 1 can be achieved, and the same effect as when using a surface coil, that is, the overlapping of strong signals from deep structures such as the brain substance can be prevented. As a result, the brain surface structure is accurately depicted in the added image, and since the voxels of each slice image during addition are small, the added image has phase disturbances suppressed as much as possible.

According to the configuration according to claim 4, in addition to exhibiting the effect of the configuration according to claim 2 or 3, at least two images with different viewing directions can be obtained by performing addition while shifting the position of each slice image. It is possible to perform stereo viewing using two images.

(Example) An example of a method for imaging a brain surface structure using an MRI apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the overall configuration of a magnetic resonance imaging apparatus to which the method of the present invention is applied.

As shown in FIG. 1, a magnet assembly MA capable of containing a subject P is used as a static magnetic field coil (a configuration using a permanent magnet may be used) using a normal conduction or superconductivity method. .) 1, and X for generating a gradient magnetic field for providing positional information of the magnetic resonance signal induction site.

Y- and z-axis gradient magnetic field generating coils 2, and a transmitting and receiving system for transmitting a rotating high-frequency magnetic field and detecting an induced magnetic resonance signal (MR multiplied signal echo signal or FID signal), such as a transmitting coil and a receiving coil. It has an implantable whole body probe 3 consisting of.

If it is a superconducting system, it includes a refrigerant supply control system and mainly controls the energization of the static magnetic field power source, the transmitter 5, which controls the transmission of RF pulses, and the induced MR multiplied signal reception control. a receiver 6 that performs excitation control for each of the gradient magnetic field generating coils 2 on the
Y-axis and Z-axis gradient magnetic field power supplies 7, 8, and 9, a sequencer 10 capable of implementing a pulse sequence for data collection, a computer system 11 that controls these and performs signal processing of detection signals and display thereof, and a display. Device 1
2.

In addition, in this embodiment, the head PH of the subject P is placed at the center of the magnetic field of the magnet assembly MA, and as shown in FIG. are placed.

This head coil 13 is connected to the implantable whole body probe 3.
Similarly, it is driven by the transmitter 5 or receiver 6 to enable transmission and reception.

Here, the pulse sequence for data collection is
The transmitter 5 is driven, and an RF pulse of a rotating magnetic field is applied from the transmitting coil of the implantable whole body probe 3 or the head coil 13, and the gradient magnetic field power supplies 7, 8.9 are driven, so that the gradient magnetic field generating coil 2 Gradient magnetic fields Gx, Gy, and Gz are applied for two-phase encoding for slices and for reading, and signals from a specific region are collected by the receiving coil of the implantable whole-body probe 3 or the head coil 13. This sequence is repeated a predetermined number of times to obtain a data group, and an image is generated from this data group.

In addition, in the pulse sequence for collecting images described above, the head PH of the subject P is targeted for imaging regarding protons, fat signals are suppressed, and water (cerebrospinal fluid:
This is a sequence based on a spin echo method or a field echo method in which the signal of CSF) is emphasized, and this sequence is executed in a multi-slice manner. Here, in the spin echo method, the echo time TE is set longer than usual, for example, about 250 m5ec (usually 80 m5ec).
That's about it. ), and the pulse repetition interval TR is 200
0 m5ec (normally about 5005sec).

).

In addition, in the field F method, the echo time TE is set to be longer than usual, for example, about 20 to 30 thsec (usually about 14 sec), and the pulse repetition interval TR is set to about 80 to 1000 m5 sec (normally about 14 sec). (Normally it is about 50 wsec.) Also, RF
The pulse flip angle is set to 10 to 20 degrees.

Note that RF is an excitation pulse, Gs is a slicing gradient magnetic field in the Z-axis direction, Gr is a read gradient magnetic field in the X-axis direction, and Ge is an encoding gradient magnetic field. In this case, it is a gradient magnetic field in the Y-axis direction, and MR is an induced magnetic resonance signal, which in this case is an echo signal.

Under such condition settings, an RF pulse was transmitted from the transmitting coil or head coil 131 of the implantable whole body probe 3, and a slicing gradient magnetic field Gs was applied from the gradient magnetic field generating coil 2, and then reversed. A read gradient magnetic field Gr and a phase encoding gradient magnetic field Ge of variable intensity are applied, and echo signals are collected from the multi-slice site by the head coil 13 at an echo time TE. By repeating this a predetermined number of times, a data group is provided to the computer system 11, and a multi-slice image is generated from this data group. Then, this multi-slice image is subjected to addition processing in the computer system 11 using a method described later, and an added image and a current multi-slice image are obtained (see FIG. 2), which are displayed on the display device 12.

Here, the addition processing of multi-slice images will be explained.

The addition processing method 1.2.3 described below is a method to obtain sensitivity characteristics similar to those using surface coils and to obtain a signal suppression effect depending on the position (depth) of the lesion (region of interest). Addition processing method 4 is a method for obtaining images for stereo viewing.

<Addition processing method 1> N multi-slice images (matrix) are
, j). k-1, 2,...IN%1, j-1~
256 (matrix).

The image obtained by weighted addition of these images is assumed to be S(1°j).

S (1, j) - Σak - Mk (1, j) Here, ak is a value corresponding to the sensitivity of the surface coil, for example (
coefficient). FIG. 3 is a characteristic diagram showing the relationship between the depth of the surface coil and the sensitivity. For example, if a lesion exists at a position 5 cm away from the coil (head coil 13), the lesion can be detected using the surface coil. If you want to clearly depict the same characteristics as in the case, if you define ak according to Figure 3,
It will look like this:

at-1,0, a2-0.9, a3-0.75, a4-
0.6, a5-0.5, ... In other words, by selecting the value of the coefficient ak attached to each slice image to an appropriately smaller value as the slice position becomes deeper, deep parts such as the ventricles and basal ganglia can be As a result, signals from deep parts such as the ventricles and basal ganglia are suppressed, and the fat image does not overlap the sensational image.

Therefore, in the image displayed on the display device 12, sensationalism is depicted without overlap with other images, the positional relationship between the brain surface and the lesion is clear, and clinically extremely useful diagnostic information can be presented.

<Additive Processing Method 2> Additive Processing Method 1 was simply to obtain the same characteristics as the surface coil, but Additive Processing Method 2 obtains the same characteristics as the surface coil, and also The weighting is to select the value of the coefficient ak according to the

That is, as shown in FIG. 4(a), when the lesion exists at a shallow position, the deeper the slice is located, the smaller the value of the coefficient ak and the greater the degree of reduction. For example, as shown in FIG. 4(b), a l -1-
Or 82-〇, 9. a3~〇, 6, a4-
Select as follows: 0- 2 +... When selected in this way, during addition, water (CSF) signals from deep slices such as in the ventricle are suppressed, and signal overlap is also suppressed.As a result, the summed image is shallow. This clearly depicts the brain surface structure, including the location of the lesion.

Contrary to the above, as shown in FIG. 5(a), when the lesion exists in a deep position, the degree of decrease in ak is reduced. For example, as shown in FIG. 5(b), al = 1
．． 0. a2-0.95. a3-0.8. a4-0.7.
Select as follows.

<Addition Processing Method 3> In Addition Processing Methods 1 and 2, each slice image is weighted with a coefficient ak, but in Addition Processing Method 3, a matrix i, which is an internal element of each slice image, Weighting is done by adding a coefficient ak depending on j.

S (1, D-Σak (1, j) ・Mk (1
, j) For example, if you are trying to particularly emphasize the brain surface,
By selecting ak as described below, it becomes possible to have hemispherical weights.

ak (1,j) -(k-N)2/N2+Q-128)2/128+(j
-128) 2/128k -1, 2, 3,..., N
, i, j −1, 2, 3,..., 256 <Addition processing method 4> Addition processing method 4 enables stereo viewing by addition processing. In other words, the weighting in addition processing method 1゜2.3 can change the viewing direction by shifting the position of each slice image during addition, and as a result, two images with different viewing directions are scanned. To enable stereo viewing using only one multi-slice image without having to

That is, Δ1. Δj and S' (1, j)−Σak −Mk (1+k (
Δ1) and j+k(Δj)), images S(1, J)' with different line-of-sight directions are created. In this case, when ΔI and Δj are non-integers, interpolation such as linear interpolation is performed as appropriate to create an image.

For example, if the pixel of the image Mk (1, j) is II,
The slice thickness is set to 101.

If Δ1-1 (that is, 1■) and Δj-〇, the line of sight direction is approximately 5.7° (-tan'l/1), as shown in Figure 6.
0), and it becomes possible to perform stereo viewing using images S and S'.

The present applicant has previously filed a patent application for an invention related to this embodiment. In the invention described in the specification and drawings of the earlier application (Japanese Patent Application No. 62-232949 filed on September 17, 1988, title of the invention "Magnetic Resonance Imaging Method"), a surface coil is used to slice 8cm thick
The echo time was set longer than usual (250 m5ec), and the pulse repetition interval TR was
The same effect as in this example is obtained by using the spin echo method in which the is set to be longer than usual (200 On + 5 ec), that is, a brain surface structure image (SA3 image: 5 surface Anato
rAy 5can).

The above embodiment has the following advantages compared to the invention of the earlier application. That is, an SA3 image viewed from a desired direction can be taken without being specified by the installation position of the surface coil, unlike the invention according to the previous application. Furthermore, since a head coil is used, setting is easy. By referring to the added image and the slice image, the positional relationship in the depth direction can be easily determined. When adding up, the weighting coefficient is adjusted appropriately depending on the location of the lesion and the case, so that the S that accurately represents the location of the lesion and the case is
It becomes possible to obtain A3 images. Stereo viewing can be performed without rescanning with a different viewing direction. Since the slice thickness is small, the voxels during imaging are small, so phase disturbance is small and signal degradation is small.

In addition, in the invention according to the previous related application, for example, when the pulse repetition interval TR is 2 seconds and the encoding is performed 256 times, the data collection time is 2 x 256-512 seconds, but in this embodiment, the field echo method is used. If used, the pulse repetition interval TR may be 80 to 1000 Illsec, so 0.08 (1,0) x 256 - 20.48 (2
56) seconds, which is advantageous because data collection can be completed in an extremely short time.

The invention can be modified in various ways without departing from the gist of the invention.

[Effects of the Invention] As described above, the configuration according to claim 1 of the present invention provides an MR system that has a static magnetic field magnet, a gradient magnetic field coil, and a transmitting/receiving coil and collects signals associated with magnetic resonance phenomena of specific atomic nuclei and images them.
In a method of imaging brain surface structures using an I device, a cylindrical coil that can wrap around the head and that can perform at least one of transmission and reception is used to image the head of a subject regarding protons. By performing a multi-slice method using a sequence in which the fat signal is suppressed and the water signal is emphasized to obtain an image for display, a cylinder that can wrap around the head was created. For each slice region close to a coil that is shaped like a coil and can perform at least one of transmission and reception, the magnetic resonance signal from water in that region is enhanced and the magnetic resonance signal from fat is suppressed and detected. , it is possible to visualize the sensual image of the water in the sensual area of the head, and because it suppresses the magnetic resonance signals from fat, the image of the fat does not overlap with the sensual image of the water, and is present on the brain surface. Images corresponding to each slice site suitable for diagnosing a lesion can be presented. In addition, since a cylindrical coil that can wrap around the head is used, it is easy to set the coil to the object to be imaged (head), allowing slice images depicting the back-of-the-brain structure viewed from any direction. Furthermore, by referring to each image, it is possible to easily know the positional relationship in the depth direction.

In the configuration according to claim 2 or 3 of the present invention, an MRI apparatus that has a static magnetic field magnet, a gradient magnetic field coil, and a transmitting/receiving coil and collects and images signals accompanying the magnetic resonance phenomenon of specific atomic nuclei is used to examine the structure of the back of the brain. In the imaging method, a cylindrical coil that can wrap around the head and can perform at least one of transmitting and receiving is used, and the subject's head is targeted for proton imaging, and fat signals are suppressed. A multi-slice method is executed using a sequence in which the water signal is emphasized and a predetermined weight is assigned to each multi-slice image obtained by this execution, and each slice image to which this weight is attached is added. Alternatively, by assigning a predetermined weight to the matrix component of each slice image obtained by the above execution, and adding each slice image to which the weight has been assigned to this matrix component, an image for display is obtained. In addition to achieving the effect of the configuration according to claim 1 above, it also has the same effect as when using a surface coil, that is, it can prevent overlapping of strong signals from deep structures such as the brain substance, so as an added image, it is possible to The structure is accurately depicted, and since the voxels of each slice image during addition are small, an added image with minimal phase disturbance can be obtained.

In the configuration according to claim 4 of the present invention, in the configuration according to claim 2 or 3, when adding each slice image, the addition is performed while shifting the position of each slice image. Alternatively, in addition to achieving the effect of the configuration according to 3, by performing addition while shifting the position of each slice image, at least two images with different viewing directions can be obtained, and stereo viewing can be performed using the two images. There is.

Therefore, according to the present invention according to claims 1 to 4, there is provided a method for imaging the structure of the back of the brain using an MRI apparatus, which can obtain an image depicting the structure of the brain surface for diagnosing a lesion existing on the brain surface of the head. This is something that can be provided.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a magnetic resonance imaging apparatus to which an embodiment of the method according to the present invention is applied, FIG. 2 is a diagram showing an example of a multi-slice in the same embodiment, and FIG. FIGS. 4 and 5 are diagrams showing sensitivity characteristics, FIGS. 4 and 5 are diagrams showing coefficients in addition processing, and FIG. 6 is a diagram showing stereo viewing. MA... Magnet assembly, 1... Static magnetic field coil, 2... Gradient magnetic field generation coil for x, y, and z axes, 3
... Implantable whole body probe, 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... Z-axis gradient magnetic field power supply, 10... Sequencer, 11... Computer system, 12... Display device, 13... Head coil. Applicant's agent Patent attorney Takehiko Suzue Full + λ chair diagram

Claims (4)

[Claims] (1) A method of imaging the brain surface structure using an MRI device that has a static magnetic field magnet, a gradient magnetic field coil, and a transmitter/receiver coil and collects and images signals associated with the magnetic resonance phenomenon of specific atomic nuclei. Using a cylindrical coil that can be wrapped around and capable of at least one of transmitting and receiving,
The present invention is characterized in that the subject's head is the object of proton imaging, and a multi-slice method using a sequence in which fat signals are suppressed and water signals are emphasized is performed to obtain an image for display. A method for imaging brain surface structures using an MRI device. (2) In a method of imaging the brain surface structure using an MRI device that has a static magnetic field magnet, a gradient magnetic field coil, and a transmitting/receiving coil and collects and images signals associated with the magnetic resonance phenomenon of specific atomic nuclei, the head is Using a cylindrical coil that can be wrapped around and capable of at least one of transmitting and receiving,
A multi-slice method using a sequence in which the fat signal is suppressed and the water signal is emphasized is performed using the subject's head as an imaging target for protons, and each multi-slice image obtained by this execution is 1. A method for imaging a brain surface structure using an MRI apparatus, characterized in that a predetermined weight is applied, and each slice image to which this weight is added is added to obtain an image for display. (3) In a method of imaging the brain surface structure using an MRI device that has a static magnetic field magnet, a gradient magnetic field coil, and a transmitting/receiving coil and collects and images signals accompanying the magnetic resonance phenomenon of specific atomic nuclei, Using a cylindrical coil that can be wrapped around and capable of at least one of transmitting and receiving,
A multi-slice method using a sequence in which the fat signal is suppressed and the water signal is enhanced is performed using the subject's head as an imaging target regarding protons, and a matrix of each slice image obtained by this execution is A method for imaging a brain surface structure using an MRI apparatus, characterized in that a predetermined weight is attached to a component, and each slice image with the weight attached to the matrix component is added to obtain an image for display. (4) The method for imaging a brain surface structure using an MRI apparatus according to claim 2 or 3, characterized in that when adding up each slice image, the addition is performed while shifting the position of each slice image.