JPH05192312A - Magnetic resonance imaging device - Google Patents

Abstract

PURPOSE:To prevent a reflected artifact and effectively use the collected data to perform a preferable diagnosis by providing a setting means for setting the data number related to the matrix different from that at signal collection at the time of image reconfiguring processing. CONSTITUTION:For the sampling data number at data collection, for example, the frequency encode directional data number is set to 512 by a matrix number setter 14, and the phase encode directional data number to 256. For the sampling data number at reconfiguration, for example, the frequency encode directional data number is set 256, and the phase encode directional data number to 256. After the setting, a sequencer 10 is started, whereby the data of 512X256 matrix is held. As a reconfigured image, thus, an image having no reflected artifact is provided on a monitor scope 12 by using the matrix data group by 256 of the frequency encode directional data number 512 and the phase encode directional data number 256.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to magnetic resonance (MR: magn).
The present invention relates to a magnetic resonance imaging apparatus that can generate an image by utilizing the phenomenon of etic resonance.

[0002]

2. Description of the Related Art The magnetic resonance phenomenon is a phenomenon in which an atomic nucleus having a non-zero spin and magnetic moment placed in a static magnetic field resonates and emits only an electromagnetic wave of a specific frequency. Angular frequency ωo (ωo = 2
Resonates at πνo, νo; Larmor frequency). ωo = γHo where γ is the gyromagnetic ratio peculiar to the type of nucleus,
Ho is the static magnetic field strength.

An apparatus for performing a biomedical diagnosis utilizing the above principle performs signal processing on an electromagnetic wave having the same frequency as the above which is induced after the above resonance absorption, and the nuclear density and the longitudinal relaxation time T1.
, The transverse relaxation time T2, the flow, the diagnostic information in which the magnetic resonance parameters such as the chemical shift are reflected, for example, the slice image of the subject is obtained non-invasively.

The collection of diagnostic information by magnetic resonance is capable of exciting all the parts of a subject placed in a static magnetic field and collecting signals, but there are restrictions on the device structure and imaging. Due to the clinical requirement of the image, the actual apparatus is designed to perform excitation and signal acquisition for a specific site.

In this case, the specific portion to be imaged is generally a sliced portion having a certain thickness, and an echo signal or FI from this sliced portion is generally used.
The magnetic resonance signal (MR signal) of the D signal is collected by executing the data encoding process many times, and these data are collected.
An image reconstruction process is performed on the data group by, for example, a two-dimensional Fourier transform method to generate a tomographic image (slice image) of the specific slice region. In addition to the tomographic image (slice image), it is possible to obtain a fluoroscopic image (scano image) or angio image suitable for use as a positioning image.

[0006]

In the reconstructed image by the above-mentioned two-dimensional Fourier transform method, aliasing artifacts may occur, and the following measures have been conventionally taken to prevent this. ing. That is, although data collection is performed at sampling points of an M × N (M and N are generally 512 to 1024) matrix, in image reconstruction processing, m × n (M ≧ m, N ≧ n ,
m and n are generally 256 or less). In general, data is collected with a matrix that is large in the read direction (frequency encoding direction), but when reconstructing, reconstruction processing is performed with a matrix that is smaller than that at the time of acquisition. Therefore, collecting data with a large matrix is required as a diagnostic image. This is a problem because it does not contribute to the improvement of the resolution.

Therefore, an object of the present invention is to provide a magnetic resonance imaging apparatus capable of preventing aliasing artifacts and effectively using collected data to perform a suitable diagnosis.

[0008]

In order to solve the above-mentioned problems and to achieve the object, the present invention has a structure in which the following means are improved. That is, the present invention obtains an image of the region by causing a magnetic resonance phenomenon in a specific region of the subject, collecting magnetic resonance signals from the region, and performing image reconstruction processing by the Fourier transform method. In the magnetic resonance imaging apparatus configured as described above, it is provided with setting means for setting the number of data relating to a matrix different from that at the time of the signal acquisition at the time of the image reconstruction processing.

[0009]

According to the present invention as described above, when the signal is acquired, the number of data is increased to collect the data, and when the signal is reconstructed, all of the acquired data is used. Resolution images can be obtained, and
By using a part of the collected data, a high-precision image without image distortion and folding artifacts is obtained although it is inferior to the former in terms of resolution, and suitable diagnosis can be performed by using both appropriately. It will be possible.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic resonance imaging apparatus according to the present invention will be described below with reference to the drawings. That is, as shown in FIG. 1, the present apparatus is a magnet assembly MA capable of accommodating a subject P therein.
A static magnetic field coil (a static magnetic field correction shim coil may be added) 1 by normal conduction or superconducting method, and X for generating a gradient magnetic field for giving position information of a magnetic resonance signal inducing site, Y and Z axis gradient magnetic field generating coil 2
And a RF 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), for example, an RF coil 3 including a transmission coil and a reception coil. ing. A magnetic field for causing a magnetic resonance phenomenon is generated by the coils 1, 2 and 3 in the subject introducing space of the gantry 4. A bed 5 is installed near the gantry 4. The couch 5 has a top plate 6 that moves the pedestal P in and out of the gantry 4 while placing the subject P thereon.

On the other hand, this apparatus has a transmitter 7 for controlling transmission of RF pulses and a receiver 8 for controlling reception of induced MR signals.
Are provided, which provide a transmission signal to the RF coil 3 and collect the induced MR signal.

Further, the present apparatus includes a gradient magnetic field power source 9 for controlling the excitation of each of the X, Y and Z axis gradient magnetic field generating coils 2, a pulse sequence for generating a slice image and a pulse sequence for generating a spectroscopy. -Sequencer 10 capable of performing a sequence, a reconstructing device 11 that controls these and performs signal processing of a detection signal, a monitor 12 that displays a reconstructed image, a data file 13, a matrix number setting device 14 have.

Here, the data file 13 is for storing the collected data, and the stored data is reconstructed by the reconstructing device 11 by, for example, a two-dimensional Fourier transform method, and is displayed on the monitor 12. It is supposed to be displayed. Further, the matrix number setting device 14 can set the number of sampling data (the number of matrices) at the time of data collection and the number of data (the number of matrices) at the time of reconstruction as desired. The number of data (the number of matrices) at the time of reconstruction determines the visual field area (FOV).

Next, the operation of this embodiment constructed as described above will be described. That is, first, the matrix number setting device 14 is operated to set the number of sampling data (the number of matrices) at the time of data collection, for example, the number of data in the frequency encode direction is 512 and the number of data in the phase encode direction is 256 (FOV is 512 × 256),
Number of sampling data (number of matrices) at reconstruction
For example, the number of data in the frequency encode direction is set to 256, and the number of data in the phase encode direction is set to 256.

After this setting, by starting the sequencer 10, the diff file 13 holds the 512 × 256 matrix data according to the above-mentioned setting.
As a result, the reconstructed image uses the matrix data group of 256 of the data number 512 in the frequency encoding direction and the data number 256 of the phase encoding direction, and as shown in FIG. 2, folding artifacts on the monitor screen 12A. An image PI1 with no image is obtained.

Further, by operating the matrix number setting device 14, the number of sampling data at the time of reconstruction (the number of matrices)
When the number of data in the frequency encode direction is set to 256 and the number of data in the phase encode direction is set to 256, the matrix data group of the number of data 512 in the frequency encode direction and the number of data 256 in the phase encode direction is used as As shown in FIG. 3, the monitor screen 12A
High resolution image P with aliasing artifacts on top
I2 is obtained.

As described above, according to the present embodiment, image distortion is caused by increasing the number of data at the time of signal acquisition and collecting the data, and using all of the acquired data at the time of reconstruction. However, a high-resolution image can be obtained, and by using a part of the collected data, a high-precision image without image distortion and aliasing artifacts can be obtained, although it is inferior to the former in terms of resolution. By using it, a suitable diagnosis can be performed. The present invention is not limited to the above-mentioned embodiments, but various modifications can be made without departing from the scope of the present invention.

[0018]

As described above, according to the present invention, since the setting means for setting the number of data relating to the matrix which is different from that at the time of signal acquisition at the time of image reconstruction processing is provided, the number of data at the time of signal acquisition is set. It is possible to obtain a high-resolution image although there is image distortion by collecting all data and using all of the acquired data at the time of reconstruction, and by using part of the acquired data In this respect, although it is inferior to the former, a high-precision image having no image distortion and no aliasing artifacts can be obtained, and a proper diagnosis can be performed by appropriately using both.

Therefore, according to the present invention, it is possible to provide a magnetic resonance imaging apparatus capable of preventing aliasing artifacts and making a suitable diagnosis by effectively using the collected data.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a magnetic resonance imaging apparatus according to the present invention.

FIG. 2 is a view showing the operation of the same embodiment.

FIG. 3 is another diagram showing the operation of the embodiment.

[Explanation of symbols]

MA ... Magnet assembly, 1 ... Static magnetic field coil, 2
... gradient magnetic field coil, 3 ... whole body RF coil, 4 ... gantry, 5 ... bed, 6 ... top plate, 7 ... transmitter, 8 ... receiver, 9
... gradient magnetic field power supply, 10 ... sequencer, 11 ... computer system, 12 ... monitor, 13 ... data file, 1
4 ... Matrix number setting device.

Claims (1)

[Claims] 1. An image of a region is obtained by causing a magnetic resonance phenomenon in a specific region of a subject, collecting magnetic resonance signals from the region, and performing image reconstruction processing by a Fourier transform method. 2. The magnetic resonance imaging apparatus according to claim 1, further comprising setting means for setting the number of data relating to a matrix different from that at the time of the signal acquisition at the time of the image reconstruction processing.