Electricity: measuring and testing – Particle precession resonance – Spectrometer components
Reexamination Certificate
1999-04-30
2001-11-06
Williams, Hezron (Department: 2862)
Electricity: measuring and testing
Particle precession resonance
Spectrometer components
Reexamination Certificate
active
06313632
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic field generator for an MRI, a packing member for the magnetic field generator for the MRI, and a method for packing the magnetic field generator for the MRI. More Specifically, the present invention relates to a magnetic field generator for MRI incorporating permanent magnets, a packing member for such a magnetic field generator for MRI, and a method for packing said magnetic field generator for MRI.
2. Description of the Prior Art
A magnetic field generator for MRI using permanent magnets is becoming popular in recent years. The magnets used in such an apparatus have a very strong magnetism. For this reason, the magnetic field generator for MRI must be protected during transportation so that no magnetic objects such as tools are drawn into a magnetic circuit built in the magnetic field generator. Typically, the entire magnetic field generator is concealed into a wooden box during the transportation as shown in FIG.
11
.
However, packing the entire magnetic field generator is a major, time-consuming job.
Another trend in the recent years is that an increasing number of magnetic field generators for MRI have an open type structure in which the number of column yokes are decreased for improved psychological comfort of a patient. In this open type magnetic field generator however, even a very small misalignment (such as 0.05 mm) between an upper plate yoke and a lower plate yoke will result in an ununiform magnetic field, adversely affecting an image obtained by the MRI apparatus.
A problem is that this open type magnetic field generator for MRI is so heavy (typically 15 tons), that an open region of the generator main body can be easily deformed by craning operation or by vibration during transportation. This results in dimensional changes in the magnetic circuit (particularly in a distance between upper and lower pole pieces), deteriorating the uniformity of the magnetic field. Therefore, after arriving at a site of installation, a long time has to be spent for re-adjusting the uniformity of the magnetic field.
SUMMARY OF THE INVENTION
It is therefore a primary object of the present invention to provide a magnetic field generator for MRI, a packing member for the magnetic field generator for MRI, and a method for packing the magnetic field generator for MRI, for simplified packing.
Another object of the present invention is to provide a magnetic field generator for MRI, a packing member for the magnetic field generator for MRI, and a method of packing the magnetic field generator for MRI, for simplified re-adjustment of the uniformity of the magnetic field.
According to an aspect of the present invention, there is provided a magnetic field generator for MRI comprising: a generator main body including a pair of plate yokes opposed to each other with space in between, a magnet disposed in each of the opposed surfaces of the pair of plate yokes, and a column yoke for magnetically connecting the plate yokes; and a packing member provided at an opening formed by the pair of plate yokes and the column yoke.
According to another aspect of the present invention, there is provided a packing member for a magnetic field generator for MRI, the magnetic field generator for MRI comprising a generator main body including a pair of plate yokes opposed to each other with space in between, a magnet disposed in each of the opposed surfaces of the pair of plate yokes, and a column yoke for magnetically connecting the plate yokes; wherein the packing member includes a shielding member provided at an opening formed by the pair of plate yokes and the column yoke.
According to still another aspect of the present invention, there is provided a packing member for a magnetic field generator for MRI, the magnetic field generator for MRI comprising a generator main body including a pair of plate yokes opposed to each other with space in between, a magnet disposed in each of the opposed surfaces of the pair of plate yokes, and a column yoke for magnetically connecting the plate yokes; wherein the packing member includes a fixing member for bridging the pair of plate yokes.
According to another aspect of the present invention, there is provided a method for packing a magnetic field generator for MRI, the magnetic field generator for MRI comprising a generator main body including a pair of plate yokes opposed to each other with space in between, a magnet disposed in each of the opposed surfaces of the pair of plate yokes, and a column yoke for magnetically connecting the plate yokes: wherein the method comprises; the first step of preparing a packing member, and the second step of providing the packing member at an opening formed by the pair of plate yokes and the column yoke.
According to the present invention, a shielding member, as well as a stud pin and a fixing member if necessary, are prepared as packing members for packing the magnetic field generator for MRI.
When packing, the shielding member is attached to the generator main body for shielding an opening formed by the pair of plate yokes and a column yoke so that no magnetic objects are drawn inside the magnetic field generator while the magnetic field generator is being transported. With the above arrangement, only necessary portions of the generator main body may be covered, and therefore it becomes easier to pack the magnetic field generator for MRI.
If the shielding member is to be attached within a strong magnetic field, the shielding member is not directly attached to the generator main body. Instead, an end portion of the gap providing member is attached to the generator main body, making the gap providing member protrude laterally outwardly of the generator main body so that the shielding member is attached to another end of the gap providing member. By providing such a gap between the generator main body and the shielding member, it becomes possible to prevent the problem that magnetic objects such as a tool left outwardly of the shielding member is drawn inside by the strong magnetism.
Further, the fixing member may be attached to bridge the pair of plate yokes at a center portion of the opening for example. By such an arrangement, it becomes possible to hold in place the pair of plate yokes opposed to each other at a high precision. Thus, the magnetic circuit of the magnetic field generator for MRI can be well protected from dimensional change during transportation for example, and as a result, the uniformity of the magnetic field of the magnetic field generator for MRI can be easily re-adjusted. This advantage is particularly significant in the open type magnetic field generator for MRI.
The above described objects and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 5003276 (1991-03-01), Sarwinski et al.
patent: 5490509 (1996-02-01), Carlson et al.
patent: 0 314 262 (1989-05-01), None
patent: 0 760 484 (1997-03-01), None
patent: 3-39139 (1991-02-01), None
patent: 4-246330 (1992-09-01), None
patent: 6-54819 (1994-03-01), None
patent: WO 84/00611 (1984-02-01), None
Stewart C. Bushong, Magnetic Resonance Imaging Physical and Biological Principles second edition, 1996.
Aoki Masaaki
Hashimoto Shigeo
Armstrong Westerman Hattori McLeland & Naughton LLP
Sumitomo Special Metals Co. Ltd.
Vargas Dixomara
Williams Hezron
LandOfFree
Magnetic field generator for MRI, packing member for the... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetic field generator for MRI, packing member for the..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetic field generator for MRI, packing member for the... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2599545