JPH08154913A - Magnetic resonance imaging apparatus - Google Patents

Abstract

PURPOSE: To provide a magnetic resonance imaging apparatus which eliminates the need for very complicated work of altering a pulse sequence to allow obtaining of an MR spectroscopy in a desired interest band efficiently. CONSTITUTION: This apparatus has a signal collection means which enables selection of a precollection to execute a pulse sequence once or a main collection to repeat the pulse sequence for generating an MR spectroscopy (MRS), an A/D conversion means for digitization of FID signals, an arithmetic device 12 to determine the MRS by a frequency analysis of data from the A/D conversion means and a display device 13 to display the MRS. It also includes an input device 14 to specify an interest band on the MRS obtained based on the FID signal gained by the precollection and means 7 and 12 to alter a sampling grade of the A/D conversion means for the main collection according to the ratio of the interest band with respect to the frequency band of the MRS.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a magnetic resonance imaging apparatus for producing MR spectroscopy.

[0002]

2. Description of the Related Art In the magnetic resonance phenomenon, information that reflects a metabolic function of a tissue called a chemical shift can be obtained. The chemical shift refers to a shift in resonance frequency caused by a difference in chemical bond of each atomic nucleus. Therefore, paradoxically, by investigating this chemical shift, we derive the structural formula of the molecule,
The substance present can be specified. It is possible to estimate the metabolic function of the tissue from the change with time of the substances present. Here, the horizontal axis is the frequency (the resonance frequency of the reference substance used as the reference for quantification analysis is 0, and the frequency deviation from this 0 point may be expressed in ppm), and the vertical axis is the signal intensity, The change in the signal strength according to the frequency is obtained as MR spectroscopy. MR spectroscopy is obtained by exciting a magnetized spin with an RF pulse, A / D-converting the FID signal collected without superimposing a gradient magnetic field, and Fourier-transforming this. This pulse sequence for MR spectroscopy generation is repeated, and the S / N is usually improved by averaging (averaging) a plurality of FID signals obtained by this.

By the way, there is a demand for knowing a specific narrow band of interest in detail, that is, with high frequency resolution. In the present device, this request is dealt with by changing the pulse sequence. Therefore, in order to obtain MR spectroscopy in a desired band of interest, it was necessary to repeat a very troublesome work of changing a pulse sequence and long-time signal acquisition until this was obtained.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic resonance imaging apparatus capable of efficiently obtaining MR spectroscopy of a desired band of interest without requiring a very troublesome work of changing a pulse sequence. Is to provide.

[0005]

A magnetic resonance imaging apparatus according to the present invention, after exciting a magnetization spin with an RF pulse,
M collects FID signals without superimposing gradient fields
A signal acquisition means for selecting pre-acquisition for executing a pulse sequence for R spectroscopy generation once, and main acquisition for repeating the pulse sequence for the number of averaging times, and a digital signal for digitizing the FID signal. Based on the conversion means, the frequency analysis means for frequency-analyzing the digital data from the digital conversion means to obtain MR spectroscopy, the display means for displaying the MR spectroscopy, and the FID signal obtained by the pre-collection. The means for specifying the band of interest on the MR spectroscopy obtained and displayed on the display means, and the sampling rate of the digital conversion means according to the ratio of the band of interest to the frequency band of the MR spectroscopy by the pre-collection Hands to change for the book collection Comprising the door.

[0006]

According to the present invention, when the pre-acquisition is performed before the main acquisition, and the desired band of interest is set by looking at the MR spectroscopy obtained by this pre-acquisition, the M by the pre-acquisition is set.
The sampling rate of the digital converting means is changed according to the ratio of the band of interest to the frequency band of the R spectroscopy, and the MR spectroscopy of the band of interest is obtained. Therefore, it is possible to efficiently obtain the desired MR spectroscopy of the band of interest without having to repeat the very troublesome work of changing the pulse sequence and repeating the signal acquisition for a long time.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a magnetic resonance imaging apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of the embodiment apparatus. The static magnetic field generating magnet 1 composed of a normal conducting magnet or a superconducting magnet has a cylindrical internal space so as to accommodate the subject P, receives a current from the static magnetic field power source 2 and is parallel to the Z axis in the internal space. Generates a static magnetic field. The gradient magnetic field coil unit 4 uses a magnetic resonance signal (here, FI
A gradient magnetic field for giving position information to the D signal) is superimposed on the static magnetic field, and FIG. 1 shows only a Y-axis gradient magnetic field coil that generates a Y-axis gradient magnetic field whose magnetic field strength changes along the Y-axis. However, in addition to this, an X-axis gradient magnetic field coil that generates an X-axis gradient magnetic field whose magnetic field strength changes along the X-axis and a Z-axis gradient magnetic field whose magnetic field strength changes along the Z-axis are actually used. And a Z-axis gradient magnetic field coil to be generated. The amplifier 5 is configured to be able to individually supply a drive current to the gradient magnetic field coils of the respective axes of the gradient magnetic field coil unit 4 under the control of the gradient magnetic field controller 6.

RF coil 8 arranged parallel to the XY plane
The a and 8b are connected to the RF transmitter 9 and the RF receiver 10. The RF coils 8a and 8b may be provided separately for transmission and reception, but here they are also used.

The RF transmitter 9 supplies a high frequency current to the RF coils 8a and 8b in order to generate a high frequency magnetic field in the radio range from the RF coils 8a and 8b to excite the magnetized spin. The RF receiver 10 receives a magnetic resonance signal induced by a magnetization spin via the RF coils 8a and 8b, and a preamplifier that amplifies the magnetic resonance signal received via the RF coils 8a and 8b. It is composed of an analog-digital converter that converts the magnetic resonance signal amplified by the preamplifier into digital data. The analog-digital converter is configured so that the sampling rate can be changed under the control of the control device 7.

The output from the RF receiver 10 is stored in the storage device 1.
1 to the arithmetic unit 12 where it is subjected to a suitable frequency analysis such as Fast Fourier Transform (FFT). This changes the signal strength according to the frequency, that is, M
R spectroscopy is created. This MR spectroscopy is displayed on the display device 13.

An input device 14 represented by a keyboard, a mouse and the like is connected to the arithmetic unit 12. By the operator's operation, the band of interest (frequency range of interest) for MR spectroscopy is input via the input device 14,
Also, sampling points are input. Arithmetic unit 12
Calculates the sampling rate of the analog-to-digital converter based on the ratio of the bandwidth of interest to the frequency bandwidth of MR spectroscopy in pre-collection described later, and the controller 7 determines the sampling rate of the analog-to-digital converter of the RF receiver 10. , The sampling rate calculated by the arithmetic unit 12 is changed. The control device 7
The gradient magnetic field control device 6, the RF transmitter 9 and the RF receiver 10 are controlled to execute a pulse sequence for MR spectroscopy generation.

FIG. 2 is a flow chart for explaining the operation of this embodiment. First, in S1, patient information such as a patient ID and a patient name is registered via the input device 14 or other input means, and a scan plan is set in S2. This scan plan includes information on the sampling rate (referred to as the first sampling rate) L1 in the pre-collection.
At S3, the pulse sequence for MR spectroscopy generation is performed only once as a pre-acquisition. The magnetic resonance signal (FID signal) obtained by this pre-acquisition is RF
The signal is amplified by the preamplifier of the receiver 10 and digitized by the analog-digital converter according to the first sampling rate L1. The output from the RF receiver 10 is sent to the arithmetic unit 12 via the storage unit 11 where it is subjected to an appropriate frequency analysis such as fast Fourier transform (FFT). As a result, an MR spectroscopy is created and is displayed on the display device 13 as an MR spectroscopy as shown in FIG. 3A in S4.

The operator obtains the MR obtained by this pre-collection.
Observe the spectroscopy and input device 1 if necessary
Change the sampling rate and sampling points via 4. If this change is not made, the process proceeds from S5 to S6, and the pulse sequence for MR spectroscopy generation is averaged at the same first sampling rate L1 as the pre-acquisition (the average number of times for improving S / N). This collection is repeated for a minute. MR spectroscopy is created from the magnetic resonance signals obtained by this main acquisition through the same processing as described above, and further averaging processing by the arithmetic unit 12 before frequency analysis, and is displayed in S7.

When the sampling rate or sampling point is changed, S8 is executed. In S81, a sampling point is numerically input through the input device 14 as needed. M obtained by pre-collection in S82
The first ROI is displayed on the display screen of the R spectroscopy. This first ROI is input via the input device 14 to FIG.
As shown in (b), the frequency is moved to the frequency f1 desired by the operator. Following this, in S83, the second RO is displayed on the display screen of the MR spectroscopy obtained by the pre-collection.
I is displayed. This second ROI is moved via the input unit 14 to the frequency f2 desired by the operator as shown in FIG. As a result, the band of interest desired by the operator is set.

Next, in S9, the arithmetic unit 12 calculates a changed sampling rate (second sampling rate) L2 from the set bandwidth x2 of the band of interest by the following equation (1). In addition, x1 is MR by pre-collection
L2 = (x2 / x1) .L1 which is the frequency bandwidth of spectroscopy (1) In S10, the controller 6 calculates the sampling rate of the analog-digital converter of the RF receiver 10 by the arithmetic unit 12. Set to 2 sampling rate L2.

After S10, returning to S3, the pulse sequence for MR spectroscopy generation is executed once as pre-acquisition according to the second sampling rate L2, and the magnetic resonance signal obtained in this pre-acquisition is obtained. , R
It is amplified by the preamplifier of the F receiver 10 and digitized by the analog-digital converter according to the second sampling rate L2. The output from the RF receiver 10 is sent to the arithmetic unit 12 via the storage unit 11,
Here, the MR spectroscopy obtained by the frequency analysis is displayed on the display device 13 as the MR spectroscopy in S4.

Here, the operator may observe the MR spectroscopy obtained in the second pre-acquisition and change the sampling rate or sampling points via the input device 14 if necessary. If this change is not made, the process proceeds from S5 to S6, and the main acquisition is performed in which the pulse sequence for MR spectroscopy generation is repeated at the second sampling rate L2 for the average number of times. MR spectroscopy is created from the magnetic resonance signals obtained by this main acquisition through the same processing as described above and further averaging processing by the arithmetic unit 12 before frequency analysis, and the MR spectroscopy is displayed in S7 as shown in FIG. 3 (c). To be done. The loop of S3 to S5 and S8 to S10 is repeated until there is no change in the sampling rate or sampling point.

As described above, according to the present invention, pre-acquisition can be performed before the main acquisition, and the desired band of interest can be set by looking at the MR spectroscopy obtained by this pre-acquisition.
M of the desired band of interest while changing the pulse sequence
It is more efficient than the conventional method of obtaining R spectroscopy. Further, since it is only necessary to specify the ROI on the MR spectroscopy obtained by the pre-acquisition, the operation itself is much simpler than the work of changing the pulse sequence. The present invention can be variously modified and implemented without departing from the gist thereof.

[0019]

The magnetic resonance imaging apparatus according to the present invention excites a magnetized spin with an RF pulse, and then executes once a pulse sequence for MR spectroscopy generation for collecting an FID signal without superimposing a gradient magnetic field. A signal collecting means capable of selecting a pre-acquisition and a main acquisition in which the pulse sequence is repeated for the number of times of averaging, a digital converting means for digitizing the FID signal, and a digital data from the digital converting means are frequency-converted. On the MR spectroscopy displayed on the display means, the frequency analysis means for analyzing and obtaining the MR spectroscopy, the display means for displaying the MR spectroscopy and the FID signal obtained by the pre-collection. Means for designating a band of interest in the Since the sampling rate of the digital converting means according to the ratio of the band of interest with respect to the frequency band of Pekutorosukopi equipped with a means for changing the order of the present collection, performs pre-collection before the collection,
When the desired band of interest is set by looking at the MR spectroscopy obtained by this pre-acquisition, the sampling rate of the digital conversion means is changed according to the ratio of the band of interest to the frequency band of the MR spectroscopy by pre-acquisition, and MR spectroscopy is obtained. Therefore, it is possible to efficiently obtain the desired MR spectroscopy of the band of interest without having to repeat the very troublesome work of changing the pulse sequence and repeating the signal acquisition for a long time.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing the operation of this embodiment.

FIG. 3 shows the displayed MR spectroscopy.

[Explanation of symbols]

1 ... Magnet for generating static magnetic field, 2 ... Power source for static magnetic field, 4
... gradient magnetic field coil unit, 5 ... amplifier, 6-gradient magnetic field control device, 7 ... control device, 8a, 8b ...
RF coil, 9 ... RF transmitter, 10 ... RF receiver, 11 ... Storage device, 12 ... Arithmetic device,
13 ... Display device, 14 ... Input device.

Claims (1)

[Claims] 1. Pre-acquisition for executing once a pulse sequence for MR spectroscopic generation to collect FID signals without superimposing gradient magnetic fields after exciting spins with RF pulses, and averaging the pulse sequences. Signal collection means capable of selecting main collection which is repeatedly executed a number of times, digital conversion means for digitizing the FID signal, frequency analysis of digital data from the digital conversion means to obtain MR spectroscopy Means, display means for displaying the MR spectroscopy, means for designating a band of interest on the MR spectroscopy displayed on the display means, which is obtained based on the FID signal obtained in the pre-acquisition, For the frequency band of MR spectroscopy with pre-collection Serial magnetic resonance imaging apparatus, characterized in that the sampling rate of the digital converting means according to the ratio of the band of interest was and means for changing the order of the present collection.