JPH04332528A - Image pickup system for mri device - Google Patents

Abstract

PURPOSE:To provide the image pickup system for an MRI device which can photograph a spin density image and an IR image by a single pulse sequence. CONSTITUTION:By applying a first 90 degree pulse, a first echo which reflects spin density is collected by a field echo method or a spin echo method, and subsequently, by applying a second 90 degree pulse, a second echo subjected to T1 emphasis is contained by an inversion recovery method. Next, a spin density image is obtained from a first echo, and an IR image is obtained from a second echo. In such a way, the spin density image and the IR image can be photographed by a single pulse sequence, and the photographing time can be shortened remarkably.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

[Field of Industrial Application] The present invention relates to an RF pulse application method in an MRI apparatus (magnetic resonance imaging apparatus), and in particular, spin density image data and T1 (longitudinal relaxation time) weighted data are collected in a series of sequences. related to technology.

0002

[Prior Art] Generally, when performing clinical imaging of a subject using an MRI device, a spin density image is taken for the purpose of observing the shape of the body tissue in detail, and an IR image is taken for the purpose of observing the characteristics of the body tissue. I often take pictures. For this reason, in the past, spin density images have been obtained by, for example, applying a 90° RF pulse and then applying a 180° RF pulse to collect echo signals (hereinafter referred to as spin echo method);
After a 0° RF pulse, the spins are reversed 180° using a gradient magnetic field to collect echoes (hereinafter referred to as field echo method)), and an IR image, which is a T1 weighted image, is obtained using a different sequence. The images were taken using the inversion recovery method.

0003

[Problems to be Solved by the Invention] However, in such a conventional imaging method, imaging must be performed using two sequences in order to obtain a spin density image and an IR image, which increases the imaging time. I end up. For this reason,
This method has the disadvantage that the examination time required for each patient is long and the efficiency of medical treatment is low.

[0004] This invention was made to solve the conventional problems as described above, and its objectives are: 1.
Spin density image and T1 weighted image (I
An object of the present invention is to provide an imaging method for an MRI apparatus that can obtain an R image. [Structure of the invention]

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention applies a first 90 degree RF pulse to a subject, and then inverts the subject by 180 degrees to collect a first echo signal, Then, a second 90 degree RF pulse is applied to collect a second echo signal by an inversion recovery method, a spin density image is obtained from the first echo signal, and a T1 weighted image is obtained from the second echo signal. It is characterized by

[0006]

[Operation] With the above-described structure, a first 90-degree pulse is applied to the subject, and a first echo signal reflecting the spin density is collected by the spin echo method or the field echo method. A second 90 degree pulse is then applied to flip the magnetization in the opposite direction to the static magnetic field, and a second T1 weighted echo signal is collected by an inversion recovery method. Therefore, with a series of pulse sequences, the spin density image and T
1 An enhanced image can be obtained.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a pulse sequence diagram showing an embodiment of an imaging system of an MRI apparatus to which the present invention is applied. As shown in the figure, in this pulse sequence, times t1, t
3, t4, 90 degree pulses P1, P2, P
3, and at time t5 a 180 degree pulse P4 is applied.
Apply.

In the figure, the magnetization of the object is oriented in the direction of the static magnetic field (Z-axis direction) until just before the 90-degree RF pulse P1 is applied at time t1. Then, when the 90 degree RF pulse P1 is applied, the magnetization M of the imaging plane selected by the slice magnetic field Gs is tilted in the y-axis direction as shown in FIG. 2(A). After a while, if a reversal magnetic field GR1 is applied in the direction of the read magnetic field GR, a first echo E1 is obtained at time t2 according to the principle of the field echo method.

At this time, the magnetization M is still oriented in the y-axis direction, so if a 90 degree RF pulse P2 is applied at time t3, the magnetization M is directed to (-Z) as shown in FIG. 2(B).
) direction. Thereafter, at time t4 after the recovery time TI has elapsed, a 90 degree RF pulse P3 is applied (
2(C)), 180 degree RF pulse P at time t5
4 (see FIG. 2(D)), the second echo E2 is obtained at time t6, which is an echo time TE after time t4, according to the principle of the inversion recovery method.

[0010] Then, by repeating this pulse sequence and collecting the first echo E1 and the second echo E2, a spin density image is reconstructed from the first echo E1, and a T1-weighted IR image is reconstructed from the second echo E2. Reconfigured.

In this way, in this embodiment, the 90 degree R
After applying the F pulse P1 and collecting the first echo E1 by the field echo method, a 90 degree RF pulse P2 is further applied to tilt the magnetization M in the (-Z) direction to perform the inversion recovery method. 2 echo E2 is being collected.

Therefore, the first echo E1 reflecting the spin density image and the second echo E2 reflecting the IR image can be obtained in a series of sequences, and the spin density image and the IR image
Images can be photographed in a short time.

FIG. 3 is a pulse sequence diagram showing a second embodiment of the present invention, and in this example, the 90 degree RF pulse P1
After applying , a 180 degree RF pulse P5 is applied to reverse the magnetization. That is, whereas in the first embodiment, the first echo E1 was collected by the field echo method, in this example, the first echo E1 is collected by the spin echo method, and the effect is similar to that of the first embodiment. can get.

FIG. 4 is a pulse sequence diagram showing a third embodiment. In this example, the 180 degree RF pulse P4 is not applied, and the second echo E2 is collected using the field gradient method. That is, the read magnetic field (not shown) is reversed to collect the second echo E2, and this embodiment also provides the same effects as the first embodiment.

FIG. 5 is a pulse sequence diagram showing the fourth embodiment, in which the flip angle of the 90 degree RF pulse P2 is set to 90 degrees.
It is slightly smaller than the degree. This speeds up magnetization recovery and further reduces imaging time.

FIG. 6 is a pulse sequence diagram showing the fifth embodiment, in which the flip angle of the 90 degree RF pulse P2 is set to 90 degrees.
It is slightly larger than the degree. Therefore, in this example as well, the recovery of magnetization is quick, as in the fourth embodiment.
Shooting time can be shortened.

FIG. 7 is a pulse sequence diagram showing a sixth embodiment. In this example, after applying the RF pulse P1, which is slightly smaller than 90 degrees, and collecting the first echo E1, a gradient magnetic field is used to collect the first echo E1. A spoiler pulse is applied to erase the lateral magnetization component. After that, a new 180 degree R
F pulse P6 is applied to direct the magnetization in the (-Z) direction, and 90 degree RF pulse P3 and 180 degree RF pulse P4 are applied.
is applied to collect the second echo E2. This method also allows the first echo E1 and the second echo E2 to be obtained in a series of sequences.

FIG. 8 is a pulse sequence diagram showing the seventh embodiment, in which the flip angle of the 90 degree RF pulse P1 is set to 90 degrees.
By making it slightly smaller than the degree, the magnetization recovery time is accelerated,
Shooting time is shortened.

FIG. 9 is a pulse sequence diagram showing the eighth embodiment, in which the flip angle of the 90 degree RF pulse P1 is set to 90 degrees.
By making it slightly larger than the degree, the magnetization recovery time is accelerated,
An example of shortening the shooting time is shown.

[0020]

As explained above, in the present invention, a first 90 degree RF pulse is applied to collect a first echo signal by a field echo method or a spin echo method, and then a second 90 degree RF pulse is applied. A second echo signal is collected using the inversion recovery method by applying an RF pulse. Then, a spin density image is obtained from the first echo signal, and a T
1 An IR image, which is an enhanced image, is obtained. Therefore, the spin density image and the T1-weighted image can be photographed in a series of sequences, resulting in the effect that the photographing time can be significantly shortened.

[Brief explanation of drawings]

FIG. 1 is a pulse sequence diagram showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the direction of magnetization at each point in a pulse sequence diagram in the first embodiment.

FIG. 3 is a pulse sequence diagram showing a second embodiment of the present invention.

FIG. 4 is a pulse sequence diagram showing a third embodiment of the present invention.

FIG. 5 is a pulse sequence diagram showing a fourth embodiment of the present invention.

FIG. 6 is a pulse sequence diagram showing a fifth embodiment of the present invention.

FIG. 7 is a pulse sequence diagram showing a sixth embodiment of the present invention.

FIG. 8 is a pulse sequence diagram showing a seventh embodiment of the present invention.

FIG. 9 is a pulse sequence diagram showing an eighth embodiment of the present invention.

[Explanation of symbols]

P1, P2, P3 90 degree RF pulse P4,
P5 180 degree RF pulse E1 1st echo E2 2nd echo

Claims (4)

[Claims] Claim 1: After applying a first 90 degree RF pulse to the subject, the spins are reversed 180 degrees to collect a first echo signal, and then a second 90 degree RF pulse is applied to recover the inversion. MR characterized in that a second echo signal is collected by a method, a spin density image is obtained from the first echo signal, and a T1 weighted image is obtained from the second echo signal.
Imaging method of I device. 2. The imaging method for an MRI apparatus according to claim 1, wherein the second 90 degree RF pulse has a flip angle slightly larger or smaller than 90 degrees. 3. The imaging method for an MRI apparatus according to claim 1, wherein the first 90 degree RF pulse has a flip angle slightly larger or smaller than 90 degrees. 4. After collecting the first echo signal, a spoiler pulse is applied to erase the transverse magnetization component, and a new one
2. The imaging system of an MRI apparatus according to claim 1, wherein the second echo signal is collected by applying an 80-degree pulse and using an inversion recovery method.