JPH045951A - Data collecting method by magnetic resonance imaging photographing - Google Patents

Abstract

PURPOSE:To remarkably shorten the photographing time by making the sampling interval wider in a high frequency part than in a low frequency part in a Fourier space at the time of collecting a magnetic resonance signal by a double matrix scan. CONSTITUTION:When a control signal for performing a double matrix scan is sent out from a computer system 11 to a sequencer 12, a double matrix scan which becomes a sampling interval by sampling shown by both a full line and a dotted line in a Fourier space is performed. In a low frequency part, the sampling interval becomes 1/2 of a conventional one, and in a high frequency part, the sampling interval becomes the same as convention. Accordingly, in the low frequency part in the Fourier space, data is collected up to a wide frequency band by the double matrix scan, and turn-back of the data from the outside of a photographing area on a reconstitution image can be prevented. Also, since the sampling interval of its high frequency part is widened, the photographing time is shortened remarkably, comparing with two folds of the case of a conventional regular scan.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a method for collecting data by magnetic resonance imaging, and in particular, a method for collecting magnetic resonance signals by performing double matrix scanning. Regarding improvements.

(Prior Art) In general, a magnetic resonance imaging apparatus to which this type of data acquisition method is applied applies a rotating magnetic field for excitation and a gradient magnetic field for slice region determination to a subject placed in a static magnetic field. Magnetic resonance signals are collected by scanning that repeatedly executes a pulse sequence that applies gradient magnetic fields for encoding and reading along with a rotating magnetic field for excitation, and images are reconstructed based on the collected magnetic resonance signals to generate reconstructed images. It is designed to be displayed on a monitor.

However, conventionally, when a reconstructed image is displayed on a monitor, artifacts may occur on the reconstructed image due to aliasing of data from outside the imaging area, as shown in FIG. 3, for example.

Therefore, as shown in Figure 4, in contrast to the conventional sampling interval shown by the solid line in Fourier space, a double matrix scan has been proposed and put into practical use, with the sampling interval shown by both the solid line and the dotted line. It became so.

According to this double matrix scan, the sampling pitch is half that of the conventional one, so data is collected over a wide frequency band, and it is possible to prevent data aliasing from the imaging area. Therefore, when the same reconstructed image as shown in FIG. 3 is displayed on a monitor, it becomes as shown in FIG. 5 due to the effect of double matrix scanning, and artifacts due to data aliasing are removed.

(Problem to be Solved by the Invention) However, when data was collected using the conventional double matrix scan, a problem occurred in that the imaging time was simply doubled compared to the conventional normal scan.

The present invention has been made in view of this situation, and its purpose is to significantly shorten the time required for photographing by multiple matrix scanning.

[Structure of the Invention (Means for Solving the Problems) The method of collecting pigs by magnetic resonance imaging of the present invention has the objective of achieving the above-mentioned objects. After applying a gradient magnetic field for slice region determination along with a magnetic field, a pulse sequence is applied using a rotating magnetic field for excitation as well as gradient magnetic fields for encoding and reading. In this method, the sampling interval is wider in the high frequency part than in the low frequency part.

(Function) With the data collection method using magnetic resonance imaging of the present invention, data is collected over a wide frequency band in the low frequency part in Fourier space by double matrix scanning, and the data can be captured on the reconstructed image. Since data aliasing from outside the area can be prevented and the sampling interval for the high frequency portion is widened, the imaging time is significantly less than twice that of conventional normal scanning.

(Example) FIG. 1 is a block diagram schematically showing a magnetic resonance imaging apparatus to which the data acquisition method of the present invention is applied.

This magnetic resonance imaging apparatus includes a static magnetic field coil 1 forming a space in which a subject P is accommodated, a gradient magnetic field coil 2 generating gradient magnetic fields for slice region determination, encoder use, and read use, and excitation The magnet assembly 4 includes an RF probe 3 for generating a rotating magnetic field and for receiving magnetic resonance signals.

Further, the static magnetic field control system 5 controls the static magnetic field coil 1 to be energized, the gradient magnetic field power supplies 6 to 8 for the X, Y, and Z axes control the energization to the gradient magnetic field coil 2, and the transmitter 9 and the receiver 10 Through the transmission and reception operations, the RF probe 3 generates a rotating magnetic field for excitation and receives a magnetic resonance signal. In addition, each gradient magnetic field power supply 6 for the X-axis, Y-axis, and Z-axis
8, transmitter 9 and receiver 10 are computer system 1
1, the sequential operation is performed by a sequencer 12 under the control of 1.

The computer system 11 has a CPU 11. as a control center for the entire system. a, and this CP, U 1
．． 1a, the input interface 11b1 output interface 11c1 disk device 11d1 memory lie and display memory llf are operated. Then, the MR multiplied signal input interface llb from the receiver 10
After digitizing, the CPU 11a composes the image,
The reconstructed image is transferred to a disk device 1.1. d sequentially and store them.

When using the reconstructed image data stored in this disk device 11d for image display, the disk device 11d
After once transferring the reconstructed image data corresponding to the image display from the memory 1.18 to the memory 1.18, the reconstructed image data on the memory 1, 1e is written to the display memory 11f, and then the reconstructed image data on the memory 1.
The reconstructed image data written in lf is read out, converted into analog data by the output interface 11C, and outputted to the disk press 1.
3, or the reconstructed image data on the memory 11e is directly converted into analog data by the output interface llc and sent to the display 13.

In a configuration including such various parts, the double computer system according to the present invention is connected from the computer system 11 to the sequencer 12.
A control signal to perform a matrix scan is sent.

Then, as shown in Figure 2, the sequencer]-2 performs a double matrix scan in which the sampling interval by sampling is shown by both the solid line and the dotted line, in contrast to the sampling interval by conventional sampling shown by the solid line in the Fourier space. The sequence of actions to be performed is made.

In the case of FIG. 2, double matrix scanning is performed in the low frequency part of the Fourier space, so the sampling interval is 1/2 that of the conventional one, and the sampling interval in the high frequency part is the same as that of the conventional one.

Therefore, in the low frequency part of the Fourier space, double matrix scanning has been used to collect data over a wide frequency band, and it is possible to prevent data aliasing from outside the imaging area on the reconstructed image, as shown in Figure 5. Images can be displayed as shown below.

Moreover, since the sampling interval for the high frequency part is widened, the imaging time is 2 times longer than that of conventional normal scanning.
significantly less than double. Note that the missing data between samplings in the high frequency portion may be interpolated using adjacent sampling data.

For this reason, according to this embodiment, the scanning time can be shortened with the same resolution as the conventional double matrix Kisyan. With this, high image quality M that eliminates data aliasing artifacts that hinder diagnosis
RI images were obtained and patient throughput was improved.

[Effects of the Invention] As explained above, the data collection method of the present invention collects data by double matrix scanning with a wider sampling interval in the high frequency part than in the low frequency part in the Fourier space. MRI images from which artifacts have been removed can be obtained in a shorter imaging time than before.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a magnetic resonance imaging apparatus to which the data acquisition method of the present invention is applied, and FIG. 2 is a schematic diagram of Fourier space when double matrix scanning is performed in an embodiment of the present invention. Figure 3 is a diagram showing a case where data aliasing artifacts occur due to conventional normal scanning; Figure 4 is a diagram showing an outline of Fourier space when conventional double matrix scanning is performed; FIG. 5 is a diagram showing the case where data aliasing artifacts are removed by double matrix scanning. 1... Static magnetic field coil 2... Gradient magnetic field coil 3...
・RF: Iil 4...Magnet assembly 5・
... Static magnetic field control system 6 to 8 ... Gradient magnetic field power supply 9 ... Transmitter 1o ... Receiver

Claims (2)

[Claims] (1) After applying a rotating magnetic field for excitation and a gradient magnetic field for determining the slice region to a subject placed in a static magnetic field, a pulse sequence is applied to the rotating magnetic field for excitation and gradient magnetic fields for encoding and reading. double matrix
A data collection method using magnetic resonance imaging, characterized in that when collecting magnetic resonance signals performed by scanning, a sampling interval is made wider in a high frequency part in Fourier space than in a low frequency part. (2) The data collection method by magnetic resonance imaging according to claim 1, characterized in that missing data between samplings in the high frequency portion is interpolated using adjacent sampling data.