JP3193474B2 - MRI equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an MRI apparatus,
More specifically, the present invention relates to an MRI apparatus that performs data acquisition based on a sequence of a high-speed FE method to which an inverted preparation pulse is added.

[0002]

2. Description of the Related Art FIG. 3 is a view showing an example of a sequence of a high-speed FE method to which an inversion type preparation pulse is added.
In the sequence A, the excitation pulse β is applied at the timing of the standby time TW after the application of the inversion type preparation pulse α, and the data acquisition DAc by the high-speed FE method is performed.
Is performed. TA is the repetition time. Data acquisition DAc for one image is performed by repeating the view scan VA by the number of phase encoding steps. As a result, a vertical relaxation emphasized image can be obtained within one second.

As another method for obtaining a vertical relaxation emphasized image, an IR method is well known. FIG. 4 illustrates a sequence of the IR method. In the sequence B of the IR method, the excitation pulse δ1 is applied at the timing of the inversion time TI after the application of the inversion pulse γ, and the data acquisition DAc by the SE method is performed. δ2 is an inversion pulse of the SE method, and TB is a repetition time. The data collection DAc for one image is performed by repeating the view scan VB by the number of phase encoding steps. Unlike the view scan VA, the inversion pulse γ is applied to each view scan VB. Therefore, it takes a long time to obtain a vertical relaxation emphasized image.

Here, it is known that by setting the inversion time TI appropriately, a longitudinal relaxation enhanced image in which a desired tissue in a living body is enhanced can be obtained. For example, in the longitudinal relaxation curve of fat as shown in FIG. 5, the time τ from the excitation to the magnetization component in the static magnetic field direction becomes 0,
When the inversion time TI is matched, a longitudinal relaxation enhanced image in which adipose tissue is suppressed can be obtained.

[0005]

In the conventional MRI apparatus, a scan parameter corresponding to the inversion time TI in the IR method is set for the sequence A of the high-speed FE method to which the inverted preparation pulse is added. There is a problem that cannot be done. For example, sequence A
[Time from application of inversion type preparation pulse α to application of first excitation pulse β for data collection] TW, and sequence B Time until the excitation pulse δ1 is applied] Even if the standby time TW is configured to be handled as a scan parameter corresponding to the inversion time TI based on the similarity of the TI, the standby time TW can be set by appropriately setting the standby time TW. It is meaningless because a longitudinal relaxation enhanced image in which a desired tissue in the body is emphasized is not obtained.

Accordingly, an object of the present invention is to provide a scan parameter corresponding to the inversion time in the IR method (by appropriately setting a scan parameter in the living body) for the sequence of the high-speed FE method to which the inverted preparation pulse is added. It is an object of the present invention to provide an MRI apparatus capable of setting a scan parameter for obtaining a longitudinal relaxation enhanced image in which a desired tissue is enhanced.

[0007]

According to the MRI apparatus of the present invention, a high-speed FRI to which an inversion type preparation pulse is added is provided.
Scan parameter specifying means for specifying a scan parameter TJ corresponding to the inversion time TI in the IR method for the sequence of the E method, and an excitation pulse at zero phase encoding after applying an inversion type preparation pulse in the sequence. Scan control means for making the time until the application of the scan parameter coincide with the scan parameter TJ.

[0008]

As a result of diligent research conducted by the inventor of the present invention, the contrast of the longitudinal relaxation enhanced image is governed by the data in the low frequency part of the phase encoding. It has been found that by appropriately setting the time until the application of the excitation pulse, a longitudinal relaxation enhanced image in which a desired tissue in a living body is enhanced can be obtained.

Based on the above results, in the MRI apparatus of the present invention, when the scan parameter TJ is designated by the scan parameter designation means, the scan control means:
The time from the application of the inversion type preparation pulse to the application of the excitation pulse at the time of zero phase encoding is made equal to the scan parameter TJ. As a result, by appropriately setting the scan parameter TJ, a longitudinal relaxation enhanced image in which a desired tissue in a living body is enhanced can be obtained. That is, it is possible to set a scan parameter corresponding to the inversion time TI in the IR method.

When the scan parameter TJ and the inversion time TI are matched, the longitudinal relaxation enhanced image obtained by the high-speed FE sequence to which the inverted preparation pulse is added and the longitudinal relaxation enhanced image obtained by the IR method are as follows. The contrast becomes similar.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the embodiment shown in the drawings. It should be noted that the present invention is not limited by this. FIG. 1 is a block diagram of an MRI apparatus 1 according to one embodiment of the present invention. The computer 2 controls the entire operation based on an instruction from the console 13. The sequence controller 3 operates the gradient magnetic field drive circuit 4 based on the stored sequence to generate a gradient magnetic field with the gradient magnetic field of the magnet assembly 5. Also,
The RF power amplifier 8 controls the gate modulation circuit 7 and modulates the RF pulse generated by the RF oscillation circuit 6 into a predetermined waveform.
From the transmission coil of the magnet assembly 5.

An NMR signal obtained by the receiving coil of the magnet assembly 5 is input to a phase detector 10 via a preamplifier 9 and further input to a computer 2 via an AD converter 11. The computer 2 reconstructs an image based on the NMR signal data obtained from the AD converter 11 and displays the image on the display device 12.

FIG. 2 is a view showing an example of the sequence A stored in the sequence controller 3. In this sequence A, after applying the inversion type preparation pulse α, the excitation pulse β is applied, and the repetition time TA is several milliseconds.
data acquisition DAc by the very short high-speed FE method
Is performed. The inversion type preparation pulse α is added in order to enhance longitudinal relaxation well even with a very short repetition time TA.

The data collection DAc for one image is:
The view scan VA is repeated by the number of steps of the phase encode PE, and one vertical relaxation enhanced image can be obtained within 1 second. The scan parameter TJ is the time from when the inversion type preparation pulse α is applied to when the excitation pulse β when the phase encode PE is zero is applied.

Next, an operation when data collection is performed based on the sequence A will be described. First, the sequence A is executed by a user using the console 13 as a sequence to be executed (hereinafter, referred to as an execution sequence).
Give instructions. The computer 2 receives the instruction of the sequence A and determines the sequence A among the plurality of sequences stored in the sequence controller 3 as the execution sequence. Then, the user is interactively requested to specify the scan parameter TJ for the sequence A.

In response to the request, the user gives an instruction of the scan parameter TJ with the same recognition as the instruction of the inversion time TI in the IR method. The computer 2 receives the instruction of the scan parameter TJ and matches the time from the application of the inversion type preparation pulse α of the sequence A to the application of the zero-phase excitation pulse β of the phase encode PE to the scan parameter TJ. Then, the application timing of each excitation pulse β corresponding to each step of the phase encode PE is calculated. Then, the application timing of each calculated excitation pulse β is set to the sequence A of the sequence controller 3. The timing for applying the inversion type preparation pulse α is set in advance.

Thus, the preparation for performing data collection based on the sequence A is completed. When the user gives a scan instruction using the console 13, data collection is performed based on the sequence A, which is a procedure and an execution sequence, stored in the computer 2 and the sequence controller 3.

Although each step of the phase encoding PE generally changes from the minimum to the maximum (or vice versa), it may be changed arbitrarily. Further, an RF pulse for idling may be added before data collection.

[0019]

According to the MRI apparatus of the present invention, a scan parameter TJ corresponding to the inversion time TI in the IR method can be set for the sequence of the high-speed FE method to which the inverted preparation pulse is added. Become. That is, similarly to the inversion time TI in the IR method, by appropriately setting the scan parameter TJ, a longitudinal relaxation enhanced image in which a desired tissue in a living body is enhanced can be obtained. If the scan parameter TJ and the inversion time TI are the same, an image similar to the longitudinal relaxation enhanced image by the IR method can be obtained even in the above sequence.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of an MRI apparatus of the present invention.

FIG. 2 is a view showing an example of a sequence stored in a sequence controller of the apparatus of FIG. 1;

FIG. 3 is an exemplary diagram of a sequence of a fast FE method.

FIG. 4 is an exemplary diagram of a sequence of an IR method.

FIG. 5 is a view showing an example of a longitudinal relaxation curve of fat.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 MRI apparatus 2 Computer 3 Sequence controller 13 Operator console A Sequence of high-speed FE method B Sequence of IR method α Inversion type preparation pulse β Excitation pulse of high-speed FE method γ Inversion pulse TA, TB Repetition time TI Inversion time TJ Scan parameter TW Wait time

Claims (1)

(57) [Claims] 1. A scan parameter specifying means for specifying a scan parameter TJ corresponding to an inversion time TI in an IR method for a sequence of a high-speed FE method to which an inverted preparation pulse is added, and an inverted preparation in the sequence. An MRI apparatus comprising: a scan control unit that makes a time from application of a pulse to application of an excitation pulse at zero of phase encoding equal to the scan parameter TJ.