JPH0541686Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field]

This idea is based on MRI (nuclear magnetic resonance imaging)
This paper relates to improvements to RF coils used in .

[Conventional technology]

In MRI, RF (radio frequency) is applied to the subject.
An antenna is required to excite the NMR signal by applying a pulse, or to receive the generated NMR signal. The RF coil is used as this antenna. Conventionally, the saddle type (6th coil) was used as the RF coil.
(see figure), a resonator type, or a surf-scoil (see figure 7).

[Problem that the invention attempts to solve]

By the way, as shown in FIG. 6, the saddle-type RF coil 61 (and resonator-type RF coil) is used when it is desired to generate an RF magnetic field 62 as uniform as possible to the subject; Although it is possible to image a wide area with one RF coil, if you limit it to a specific narrow area or slice (shown with diagonal lines), signals from other unnecessary areas will also be received. Since this simply serves as a nozzle for the necessary portion, the S/N ratio will decrease. On the other hand, as shown in FIG.
1, the RF magnetic field 72 is generated in a narrow range.
Since the sensitivity region of the RF coil is localized to a limited area, the slices shown with diagonal lines have a high S/N.
However, when imaging a wide area, it is necessary to move the position of the RF coil. In addition, in the case of this SURF S coil, it is difficult to obtain signals from deep parts of the human body. Therefore, in the past, there was an inconvenience in that various RF coils had to be prepared in advance depending on the imaging region and one had to be selected from among these each time. The purpose of this invention is to provide a convenient RF coil that can be used for various imaging regions with one RF coil.

[Means to solve the problem]

The RF coil according to this invention consists of a segment consisting of a large number of linear conductors arranged to surround the subject, a ring-shaped conductor arranged at both ends of each segment, and a ring-shaped conductor arranged at both ends of each segment. It has a switching element which is arranged at each node and performs arbitrary short-circuiting and opening between each of these segments and the ring-shaped conductor at both ends.

[Effect]

By switching the switching elements arranged at the nodes of each segment and the ring-shaped conductor at both ends, it is possible to short-circuit or open a given segment and the ring-shaped conductor at both ends, As a result, it becomes possible to form a coil of arbitrary shape. Therefore, by controlling the switching element according to the part to be actually inspected, it is possible to obtain the most suitable coil shape for that part. Therefore, although it is a single RF coil, it is possible to avoid receiving data that is unnecessary as data for imaging and that only becomes noise.
It is possible to obtain an image with a high ratio, and it is also possible to avoid the trouble of moving the coil as in the case of the Surf S coil.

【Example】

In one embodiment of the invention, as shown in FIG. 1, a number of (eight in this example) linear conductor segments 1 to 8 are arranged along the side of an imaginary cylinder and parallel to the axis of the cylinder.
The subject is placed inside this imaginary cylinder. In other words, a large number of segments 1 to 8 are arranged to surround the subject. Ring-shaped conductors 11 and 12 are arranged on both ends, and switching elements 21 are placed at the nodes between the segments 1 to 8 and the ring-shaped conductors 11 and 12. The switching element 21 is, for example, a PIN diode, and allows short-circuiting and opening between any conductors as shown in FIG. 2. This switching element 21 allows
Any segment can be short-circuited or opened via the ring-shaped conductors 11 and 12, and any shape of coil can be formed with a single RF coil. For example, when a tomographic image of a slice parallel to the segments 1 to 8 as shown by the diagonal lines in FIG. 3 is to be obtained, the segments 2 and 8 form a saddle-shaped loop via the upper ring-shaped conductors 11 and 12, and the segments 3 and 7 form a saddle-shaped loop.
Each of the switching elements 21 is controlled so that the saddle-shaped loop is formed via the ring-shaped conductors 11 and 12 below the saddle-shaped loop. This forms a pair of modified saddle-shaped RF coils, and an NMR signal with a high S/N ratio can be obtained for the slice shown with diagonal lines. That is, the NMR signal from the slice shown with diagonal lines is best sensed by segments 2, 3, 7, and 8, while the other segments 1, 4, 5, and 6 receive signals other than those shown with diagonal lines well, that is, the slice shown with diagonal lines has a high probability of sensing signals that are nothing but noise. Also, for example, as shown with diagonal lines in FIG. 4,
For the same reason, when imaging slices parallel to segments 1 to 8, segments 4,
The switching element 21 is controlled so that the ring-shaped conductors 11 and 12 below the conductor 6 form a loop, forming an RF coil similar in shape to a SurfS coil. In this way, although it is a single RF coil, it is possible to form an RF coil having a shape most suitable for the slice position.
The RF coil can be easily formed. Although the number of parallel segments is eight in the above embodiment, it can be any number equal to or greater than two. Furthermore, as shown in Fig. 5, the segments 1 to 8 can be divided into several segments (two segments in Fig. 5) in the longitudinal direction, and these segments can be connected by the ring-shaped conductor 13 via the switching element 21. With the configuration shown in Fig. 5, the sensitive area can be localized in the longitudinal direction of the segments 1 to 8 by controlling the switching element 21.

[Effect of the idea]

According to this invented MRI RF coil, one
Even if it is an RF coil, it is necessary to avoid receiving data that is unnecessary as data for imaging and is only used as a nozzle, and to avoid the trouble of moving the coil as in the case of the Surf S coil. is possible.

[Brief explanation of the drawing]

Fig. 1 is a schematic perspective view of an embodiment of this invention, Fig. 2 is a circuit diagram showing a switching element, and Figs. 3 and 4 are cross-sectional views showing the relationship between slice positions and connected segments. , FIG. 5 is a schematic perspective view of another embodiment, and FIGS. 6 and 7 are sectional views of the conventional example. 1 to 8...Segment, 11 to 13...Ring type conductor, 21...Switching element, 61...Saddle type coil, 62, 72...RF magnetic field, 71...
...Surf S Coil.

Claims (1)

[Scope of utility model registration request] A segment consisting of a large number of linear conductors arranged so as to surround the subject, a ring-shaped conductor arranged at both ends of each segment, and arranged at the node of each of the segments and the ring-shaped conductor at both ends, An MRI RF coil that has a switching element that performs arbitrary short-circuiting and opening between each of these segments and a ring-shaped conductor at both ends.