JPS62201146A - Magnetic resonance imaging diagnostic apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a method for irradiating a subject lying supine on a top plate and providing a reference line that coincides with the body axis direction of the subject. The present invention relates to a magnetic resonance imaging apparatus having a light projector.

(Prior Art) A magnetic resonance imaging diagnostic apparatus (hereinafter referred to as an MRI apparatus) has a floodlight that illuminates a subject lying supine on a top plate from above. For example, a cross-shaped reference line is provided to match the directions.

This projector is set to Fi5 so that it illuminates the center of the top plate, and is in a fixed state like a CT scanner.

When tracing a cross-sectional image of a subject using such an MHI device, a gradient magnetic field is applied in the direction of approach of the top plate to the MRI device (referred to as the Z axis), and selective excitation pulses are applied to scan. I'm trying to get a cross-sectional view of the location. In this case, in order to make an accurate diagnosis,
It is desirable to obtain a transverse image that is symmetrical on the left with respect to the body axis of the subject, and for this purpose it is necessary to align the reference line of the light projector with the body axis of the subject. The left-right symmetry of the cross-sectional image is an important clue, especially in head diagnosis, and if an asymmetrical cross-sectional image is obtained due to a mismatch between the body axis and the reference line, it is difficult to distinguish whether the asymmetric image is due to a lesion or a mismatch. It will not be possible to get it.

Here, in a conventional MRI apparatus, since the projector is installed in a fixed state as described above, it is necessary to adjust the posture of the subject on the top plate so that the body axis coincides with the reference line.

However, this may force the subject into an unreasonable posture, causing pain, and depending on the subject, it may be impossible to assume such a posture due to the body shape of the subject.

Therefore, in these cases, prior to the original scanning operation, a positioning scanning device is used in advance to copy the coronal image, positioning is performed based on this coronal image, and the original scanning operation is performed. A method is used to obtain bilaterally symmetrical cross-sectional images.

(Problems to be Solved by the Invention) Conventional MRI apparatuses require positioning scanning in order to obtain bilaterally symmetrical cross-sectional images, so there is a problem that the number of inspection steps increases and the inspection time becomes longer.

The present invention has been made in response to this problem, and it is an object of the present invention to provide an MRI apparatus that can obtain bilaterally symmetrical cross-sectional images without performing a positioning scan.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides means for rotatably attaching a projector to a top plate and inputting information on the rotation angle of the projector into a computer. and means for controlling the gradient magnetic field power supply by a computer in accordance with this information.

(Function) Since this reference line is aligned with the body axis by rotating the projector, a symmetrical cross-sectional image can be obtained without performing a positioning scan while keeping the subject's posture as desired. Information on the rotation angle of the projector is input to the computer, and the subtraction machine controls the gradient magnetic field power supply accordingly to obtain the desired gradient, so that a true cross-sectional image without errors can be obtained.

(Embodiment) FIG. 1 shows a schematic diagram of an MRI apparatus according to an embodiment of the present invention, in which a subject 2 (patient) lies supine on a top plate 1, and the head 3 of this subject 2 is placed on the top plate 1. It is assumed that the position is tilted by θ° from the center line 4 (Z-axis).

In other words, the body axis 5 of the subject 2 is located on the Z' axis tilted to the left in the figure by θ° from the Z axis. The floodlight 6 is placed at a Z angle with respect to the top plate 1.
Reference numeral a8 is a pedestal that is rotatably installed around an axis and thereby moves the reference line 7 to a position that coincides with the body axis Z- of the subject 2.

By rotating the light projector 6 in this way, the subject 2
The body axis Z- can be made to coincide with the reference line 7 without changing the posture of the head 3 which is tilted from the Z-axis.

The gradient magnetic field for imaging is applied with a gradient in the Z-axis direction, but because the reference line 7, which is originally parallel to the Z-axis, is on the Z-axis tilted by θ° from the Z-axis, the magnetic field gradient is Similarly, the direction of should also be shifted by θ°. Figure 2 shows a gradient magnetic field control system for this purpose, in which the projector 6 rotates m
When the rotation angle θ° is controlled by H9, the rotary encoder 10 detects this rotation angle θ° and encodes it as a digital signal. This signal is read into the computer 12 via the interface 11. As a result, the computer 12 controls the gradient magnetic field power supply 14 via the interface 13 so that the magnetic field gradient has a desired direction according to the rotation angle θ°. That is, the gradient magnetic field power supply 14 is
The magnetic fields Gx and Gz have a ratio of tanθ=Gx/GZ (GZ: magnitude of the magnetic field gradient in the Z-axis direction, Gx: magnitude of the magnetic field gradient in the X-axis direction perpendicular to the Z!1!1 direction). Like that slope T! Determine the current value of the i-field coil.

The magnitude of the magnetic field gradient Gi can be controlled in proportion to the current value Ii of the gradient magnetic field coil [IiαGi (i=X
, V, Z)].

As a result, the gradient G in one direction of the body axis Z of the subject 2 = (
Gx, 0. GZ) can be set, so by performing one scan operation in the direction perpendicular to the body axis Z-, a symmetrical true transverse image as shown in FIG. 3 can be obtained. Therefore, the conventional positioning scan is not required, so the subject can be examined in a comfortable posture, and the number of inspection steps and inspection time are also shortened.

[Effects of the Invention] As described above, according to the present invention, the reference line is made to coincide with the body axis by rotating the projector, so that the left and right positions can be adjusted by performing a single scan without performing a positioning scan. A symmetrical cross-sectional image can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an MRI apparatus according to an embodiment of the present invention, and FIG.
The figure is a block diagram showing a gradient magnetic field control system of the MRI apparatus of the present invention, and FIG. 3 is a schematic diagram showing a bilaterally symmetrical cross-sectional image obtained by the MRI apparatus of the present invention. 1...Top plate, 2...Subject, 3...Head, 4...
- Center line (Z axis), 5... Body axis (Z' axis shifted by θ° from the Z axis), 6... Emitter, 7... Reference line of the emitter, 10... Rotary encoder, 12 ...Mechanical machine, 14...Gradient magnetic field power supply.

Claims (1)

[Claims] In a magnetic resonance imaging diagnostic apparatus having a floodlight that illuminates a subject lying supine on a top plate and is provided with a reference line that coincides with the body axis direction of the subject, the floodlight has a reference line that is aligned with the body axis of the subject. It is rotatable with respect to the top plate so that it can be moved in accordance with the direction, and means for detecting and encoding the rotation angle of the projector and reading it into a computer, and a gradient magnetic field power source for forming a gradient magnetic field are connected to the computer. A magnetic resonance diagnostic apparatus comprising: means for controlling according to a rotation angle.