JPS6234548A - Magnetic resonance imaging 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] [Technical Field of the Invention] The present invention relates to magnetic resonance (MR) technology.
information based on the density distribution of specific atomic nuclear spins in a specific cross section of the object using so-called computer tomography (CT).
computed tomography)
MR called MRIH equipment that images as a computed tomogram
The present invention relates to an imaging device.

[Technical Background of the Invention] For example, in a diagnostic MRI apparatus, in order to obtain a tomographic image (q) at a specific position of a subject, the subject P as shown in FIG.
A very uniform static magnetic field HO along the illustrated Z-axis direction is applied to the static magnetic field HO, and a linear magnetic field gradient Gz is added to the static magnetic field Ho by a pair of gradient magnetic field coils IA and 1B. For a static magnetic field HO, a specific atomic nucleus has a stacked wavenumber ω expressed by the following equation:
Resonates with O.

ω0=γHa (1) In equation (1), γ is the gyromagnetic ratio, which is specific to the type of atomic nucleus. Therefore, a rotating magnetic field H1 having an angular frequency ωO that makes only specific atomic nuclei resonate is applied to the subject P via a pair of transmitting coils 2A and 2B provided in the probe head.

In this way, due to the magnetic field gradient Gz of the line j~
A specific slice portion S that selectively acts only on the illustrated x-y plane portion selectively set in the 110 directions and clears the tomographic image (although it is a portion on a plane, this exists in reality) 9
The MR current problem occurs only in those who have the same characteristics. .

This MR phenomenon occurs through the pair of receiving coils 3A and 3B provided in the probe head.
II): free 1induction dec
ay) signal (hereinafter referred to as "r F I l) signal"), and by Fourier transforming this signal into 0), K-Svec 1 to R can be obtained for the rotational frequency of a specific nuclear spin. In order to obtain the RAM layer image as a C]-image, projection images of the slice portion S in multiple directions within the xy plane are required. Therefore, the slice part S
After exciting the When the gradient Gxy is applied (by a coil, etc. not shown), the isomagnetic field line E at d3 becomes a straight line on the slice portion S of the subject P, and the rotational frequency of a specific nuclear spin on this isomagnetic field line E is −F. It is expressed by the following formula (1). For convenience of explanation here -
L isomagnetic field lines E are [1 to [n], and each of these isomagnetic field lines [1
Consider that the magnetic field on [n produces signals 01 to [)n, which are a kind of FID signal 8, respectively 1, signal D1
"The amplitude of Dn is proportional to the spin density of a specific atomic nucleus on the isomagnetic field lines E1 to En passing through the slice portion S. However, the FID signal actually observed is the signal D.
A composite "ID signal" is obtained by adding all of 1 to Dn.

Therefore, by Fourier transforming this composite FID signal, projection information (one-dimensional image) P[) of the slice portion S onto the X-axis is obtained. This (by changing the composite ratio of the magnetic field gradients Gx and Gy), projection information in each direction in the x-y plane can be obtained in the same way as in the case of CT images can be synthesized.

[Problems with anterior nasal technology] By the way, in this type of MR imaging device, the MR multiplied signal detected by the probe head is very weak, so this signal is generally amplified through a preamplifier and then subjected to screening processing. There is.

However, as shown in FIG. 3<A>, the probe head 1 and the preamplifier 2 are used as separate systems, and the signal cable 3. When connected via a connector etc., the probe head 1 and preamplifier 2 are connected as shown in the circuit shown in Figure 3(b).
Since a large amount of impedance is present on the intervening circuit, there is a problem in that the performance of the probe head, which acts as a resonant circuit, is severely degraded.

[Object of the Invention] The present invention has been made based on the above circumstances, and its purpose is to detect a weak MR multiplied signal more efficiently and with high sensitivity to obtain a high-resolution MR image. The object of the present invention is to provide a magnetic resonance imaging device that can perform the following tasks.

[Summary of the Invention] The outline of the present invention for achieving the above object is to place a subject in a uniform static magnetic field generated by a static magnetic field generating coil, and apply a gradient vii field to this uniform static magnetic field. A superimposed and excitation rotating magnetic field is applied to produce a magnetic resonance phenomenon in the subject, the induced magnetic resonance signal is detected by a probe head, and image reconstruction processing is performed to obtain image information of the subject. In this magnetic resonance imaging apparatus, a tank circuit of a preamplifier for amplifying a magnetic resonance signal detected by the probe head is directly connected to the probe head.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a circuit diagram of a probe head and a preamplifier in a magnetic resonance imaging apparatus that is an embodiment of the present invention. connected. Furthermore, a tank circuit 4 of a pre-amplifier 2 is provided between the probe head 1 and the signal cable 3 and is directly connected to the probe head 1, and the IVtR signal detected by the probe head 1 is connected to the tank circuit 4. The signal is sent to the signal cable 3 via the signal cable 3.

The device of the present invention configured as J: connects the tank circuit 4 of the preamplifier 2 to the probe head 1 side of the signal cable 3, that is, directly connects the probe head 1 and the tank circuit 4. The resonance is removed,
Since the MR multiplied signal is input to the preamplifier 2 through the resonant MR multiplied signal signal cable 3 and amplified, the MR multiplied signal can be detected efficiently and with high sensitivity.

Although one embodiment of the present invention has been described above, it goes without saying that the present invention is not limited to the above-mentioned embodiment, and can be modified as appropriate within the scope of the gist of the present invention.

For example, as shown in Fig. 1(B), if a variable capacitor is attached to the tank circuit and the capacitance of the variable capacitor is varied by applying DC voltage to the signal cable 3, the circuit of Fig. 1(B) can be used. You can automatically search for joint shooting points. Furthermore, as shown in FIG. 2, it is also possible to connect not only the tank circuit 4 but also the preamplifier 2 directly to the probe head side of the signal cable 3. In this way, it is possible to pass the signal through the signal cable 3 after amplifying the weak MR signal.

[Effects of the Invention] As detailed above, according to the present invention, a magnetic field that can efficiently and highly sensitively output MR (No. 8) detected by a probe head and obtain 1q of high resolution M A resonance imaging device can be provided, which can greatly contribute to improving medical diagnostic capabilities.

[Brief explanation of the drawing]

FIG. 1(A) is a circuit diagram of a probe head and preamplifier showing one embodiment of the present invention, FIG. 1(B) is a circuit diagram showing another embodiment, and FIG. 2 is a circuit diagram showing another embodiment. Figure, Figure 3 (
A) is a circuit diagram of a conventional probe head and preamplifier, Fig. 3 (B) is an equivalent circuit diagram, Fig. 4 is an explanatory diagram showing the principle configuration of MRI, and Fig. 5 is a diagram showing projection information using magnetic resonance phenomena. 1q is a principle diagram. 1...probe head, 2...preamplifier, 3...
・Signal cable, 4...Tank circuit. Agent Patent Attorney Noriyuki Chika Yudo Norio Ogo 5PJ1 Diagram (A)

Claims (1)

[Claims] A subject is placed in a uniform static magnetic field generated by a static magnetic field generating coil, a gradient magnetic field is superimposed on the uniform static magnetic field, and an excitation rotating magnetic field is applied to produce a magnetic resonance phenomenon in the subject. In a magnetic resonance imaging apparatus that obtains image information of the subject by detecting the induced magnetic resonance signal with a probe head and performing image reconstruction processing, the magnetic resonance signal detected by the probe head is amplified. A magnetic resonance imaging apparatus characterized in that a tank circuit of a preamplifier is directly connected to the probe head.