Detecting coil for magnetic resonance diagnostic apparatus

Abstract: In order not to nip the clothes or skin of a subject between the joining portions (13,23; 14,24) of coil members when a detecting coil for a magnetic resonance diagnostic apparatus is fitted around. a region of the subject such as the leg or neck, the detecting coil (100) for a magnetic resonance diagnostic apparatus, which can be separated into an upper coil member (10) and a lower coil member (20) and has an annular shape when these members (10, 20) are integrally joined, is provided at the joining portions of the lower coil member (20) with guards (27, 28) of a silicone rubber having a hardness of Hs80.

Description: The present invention relates to a detecting coil for a magnetic resonance (MR) diagnostic apparatus, and more particularly, to such a coil which is improved so as not to nip the clothes or skin of a subject between the joining portions-of coil members when the coil is fitted around a region of the subject such as the leg or neck. Japanese Patent Application Laid Open No's. 4-354934(1992) and 6-254068(1994) disclose an RF (radio frequency) coil for an MR imaging apparatus which can be separated into an upper structure and a lower structure and is cylindrically shaped when these structures are integrally joined. The split detecting coil as disclosed in the above applications is formed so that the coil is in close contact with the region of the subject to be examined such as the leg or neck, in order to efficiently receive an MR signal. This implies, however, that the coil affords no spatial leeway. The coil members are therefore liable to nip the clothes or skin of the subject between their joining portions when they are integrally joined around the region such as the leg or neck of the subject. It is therefore an object of the present invention to provide a detecting coil for an MR diagnostic apparatus which is improved so as not to nip the clothes or skin of a subject between the joining portions of coil members when the coil is fitted around a region of the subject such as the leg or neck. In accordance with a first aspect, the present invention provides a detecting coil for an MR diagnostic apparatus in accordance with claim 1 hereof. According to the detecting coil for an MR diagnostic apparatus of the first aspect, catching of the clothes and skin of a subject between the joining portions of the coil members is made unlikely by the cushioning effect of the guard portions. The clothes and skin of the subject are thus prevented from being nipped when the coil is fitted around the region such as the leg or neck of the subject. The present invention provides an additional advantage that the coil member is protected from damage when accidentally dropped or bumped against a table etc., because the shock is absorbed by the cushioning effect of the guard portion. Elastomer materials usable in the present invention include: silicone rubbers, nitrile rubbers, fluororubbers, chloroprene rubbers, polyurethane rubbers, butyl rubbers, Thiokol rubbers, polybutadiene rubbers and styrenebutadiene rubbers. In accordance with a second aspect, the present invention provides the detecting coil for an MR diagnostic apparatus of the foregoing structure, wherein the hardness of the elastomer as determined by the Japanese industrial Standard (JIS) spring hardness test K6301 is Hs50 - Hs80. The inventors' studies show that when the hardness of the elastomer as determined by the JIS spring hardness test is less than Hs50, the guard portion is too soft and poor in durability, and when it is more than Hs80, the guard portion is too hard and is difficult to mold. A hardness in the range of from Hs50 to Hs80 inclusive provides moderate cushioning properties and is preferred. Thus, according to the detecting coil for an MR diagnostic apparatus of the present invention, the likelihood of the clothes and skin of a subject being caught between the joining portions of the coil members is greatly reduced by the cushioning effect of the guard portions, thereby preventing the clothes and skin of the subject from being nipped between the joining portions of the coil members. Moreover, the coil member is protected from damage when accidentally dropped or bumped, because the shock is absorbed by the cushioning effect of the guard portion. Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings, in which Figure 1 is an exploded perspective view of a detecting coil for an MR diagnostic apparatus in accordance with a first embodiment of the present invention. Figure 2 is a perspective view of the detecting coil for an MR diagnostic apparatus in accordance with the first embodiment in the assembled state. Figure 3 is a front elevational view of the detecting coil for an MR diagnostic apparatus in accordance with the first embodiment. Figure 4 is a rear elevational view of the detecting coil for an MR diagnostic apparatus in accordance with the first embodiment. Figure 5 is a top plan view of the detecting coil for an MR diagnostic apparatus in accordance with the first embodiment. Figure 6 is a bottom plan view of the detecting coil for an MR diagnostic apparatus in accordance with the first embodiment. Figure 7 is a left side view of the detecting coil for an MR diagnostic apparatus in accordance with the first embodiment. Figure 8 is a right side view of the detecting coil for an MR diagnostic apparatus in accordance with the first embodiment. Figure 9 is a right side view of the detecting coil for an MR diagnostic apparatus in accordance with the first embodiment. Figure 10 is an exploded perspective view of a detecting coil for an MR diagnostic apparatus in accordance with a second embodiment of the present invention. Figure 11 is a perspective view of a detecting coil for an MR diagnostic apparatus in accordance with a third embodiment of the present invention. -- First Embodiment -- Figure 1 is an exploded perspective view of a detecting coil for an MR diagnostic apparatus in accordance with a first embodiment of the present invention. The detecting coil 100 for an MR diagnostic apparatus consists of a semi-annular upper coil member 10 and a semi-annular lower coil member 20. The upper coil member 10 is covered with covers 11, 12 of urethane resin, and has electrical connectors 13, 14 and locking levers 15, 16 at its joining portions. The lower coil member 20 is covered with covers 21, 22 of urethane resin, and has electrical connectors 23, 24 and locking concavities 25, 26 at its joining portions. At the joining portions of the lower coil member 20 are further provided guards 27, 28 of a silicone rubber having a hardness of Hs80. The guards 27, 28 protrude upwardly about 15 mm above the surfaces of the connectors 23, 24. The outer ends of the guards 27, 28 are cut obliquely. Reference symbol 'a' designates a hole for a signal cable, 'b1' designates a registration mark to which an alignment laser beam is adjusted when the coil is used for a subject raised up (e.g., in imaging the neck region), 'b2' and 'b3' each designates a registration mark to which the alignment laser beam is adjusted when the coil is used rotated 45 degrees (e.g., in imaging the knee region), and 'c1' and 'c2' each designates an alignment mark for orienting the upper coil member 10 and the lower coil member 20. Figure 2 is a perspective view showing the upper coil member 10 and the lower coil member 20 integrally joined to form the annular detecting coil 100 for an MR diagnostic apparatus. Figure 3 is a front elevational view, Figure 4 is a rear elevational view, Figure 5 is a top plan view, Figure 6 is a bottom plan view, Figure 7 is a left side view, and Figure 8 is a right side view, of the detecting coil 100 for an MR diagnostic apparatus. Figure 9 illustrates the detecting coil 100 of an MR diagnostic apparatus being fitted around the neck of a subject. The lower coil member 20 is disposed in a space between a bed B and the neck of the subject H lying thereon. The upper coil member 10 is then integrally joined with the lower coil member 20 so that it covers the neck of the subject H. This helps to prevent the clothes and skin of the subject H from resting on the joining portions of the lower coil member 20 because the guards 27, 28 protrude from the joining portions of the lower coil member 20. The clothes and skin of the subject H can be thus prevented from being nipped between the lower coil member 20 and the upper coil member 10. Since the outer ends of the guards 27, 28 are cut obliquely, the guards 27, 28 serve also as guides for the joining. Moreover, the lower coil member 20 is protected from damage to the connectors 23, 24 etc. when it is accidentally dropped or bumped against a table etc., because the shock is absorbed by the cushioning effect of the guards 27, 28. -- Second Embodiment -- Figure 10 is an exploded perspective view of a detecting coil for an MR diagnostic apparatus in accordance with a second embodiment of the present invention. The detecting coil 100A for an MR diagnostic apparatus consists of a semi-annular upper coil member 10A and a pedestal-like lower coil member 20A, and is used for limb imaging. The lower coil member 20A is provided at its joining portions with a connector 23A etc., and guards 27A, 28A of a silicone rubber having a hardness of Hs80. -- Third Embodiment -- Figure 11 is a perspective view of a detecting coil for an MR diagnostic apparatus in accordance with a third embodiment of the present invention. The detecting coil 100B for an MR diagnostic apparatus consists of a semi-annular upper coil member 10B and a pedestal-like lower coil member 20B, and is used for imaging the head region. The upper coil member 10B and the lower coil member 20B are pivotally attached to each other at their respective ends, and the other ends are configured to be opened and closed. At the joining portions on the side of the open-and-close ends are provided a connector 23B etc., and guards 27B, 28B of a silicone rubber having a hardness of Hs80.

Claims: A detecting coil (100) for an MR diagnostic apparatus which consists of two or more coil members (10,20) and has a cylindrical or annular shape when the coil members are integrally joined, characterised in that a part or the entirety of each joining portion of the two or more coil members is provided with an elastomeric guard portion, (27,28), protruding from one of the coil members at each joining portion and extending over the ends of the respective coil members at said joining portion along the inner surface of the cylindrically or annularly shaped detection coil when the coil members are integrally joined, such that the likelihood of catching a portion of an object placed within the detection coil between two joined coil members is reduced. The detecting coil for an MR diagnostic apparatus of claim 1, wherein the hardness of the elastomer as determined by the Japanese Industrial Standard spring hardness test K6301 is Hs50 - Hs80. The detecting coil for an MR diagnostic apparatus of claim 1, wherein each joining portion includes an electrical connector (23,24).

Inventors: HAYASHI YUJIRO, SAKUMA MASAAKI, HAYASHI, YUJIRO, SAKUMA, MASAAKI
Applicants: YOKOGAWA MEDICAL SYST, GE YOKOGAWA MEDICAL SYSTEMS, LTD.
Application year: 1998
Main classification: G01R33
IPC codes: G01R33, A61B5