Electricity: measuring and testing – Particle precession resonance – Spectrometer components
Reexamination Certificate
1999-10-27
2001-07-03
Patidar, Jay (Department: 2862)
Electricity: measuring and testing
Particle precession resonance
Spectrometer components
C324S322000, C324S309000
Reexamination Certificate
active
06255823
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a Faraday cage, particularly for Nuclear Magnetic Resonance applications, comprising grounding means or means having a predetermined potential.
2. Description of Related Art
The importance of suppressing electromagnetic noise from the environment is well-known in the field of imaging by Nuclear Magnetic Resonance machines, hereafter indicated as MRI.
This noise, when it is not properly suppressed, can generate artifacts or parasitic images which deteriorate the quality of the acquired image.
Such suppression, always indispensable in MRI diagnostics, is particularly critical when using MRI equipment of the so-called dedicated type, i.e. designed to imaging of limited parts of the body or anatomic districts thereof, because, in order to improve installation simplicity and cost reduction, alternatives to costly and complex traditional solutions are needed.
Also, in dedicated machines, the patient body may act someway as an antenna, because it is almost entirely outside the imaging cavity, and so it captures electromagnetic noise and transmits it inside.
While prior art systems have costs which justify the use thereof in high and medium cost machines, in low and medium cost arrangements partial solutions are used, which avoid Faraday cages, because of the cost influence of these cages on the overall cost of the machine.
Although various solutions have been proposed for suppressing such noise, such as grounding the patient body and/or the medical staff by appropriate arrangements, or using self-shielding equipment, the best solution always consists in a Faraday cage electromagnetic shield enclosing the equipment, the patient and possibly the medical staff. Hence, the need arises to provide more attractive Faraday cages even for machines of a lower cost range.
OBJECTS AND SUMMARY
The invention has the object to provide, by using simple and comparatively inexpensive arrangements, a Faraday cage: which provides an effective electromagnetic shield to ensure suppression of noise signals interfering with MRI; which can be assembled and installed inside existing premises, without requiring building works, and ensuring a highly versatile installation, with the additional advantage that bureaucracy for building works is simplified or avoided; which has such a size as to delimit a sufficient volume to perform imaging operations, and at the same time such as to allow integration in relatively limited spaces; which provides a shielded area of limited dimensions in rooms possibly having a greater extension than the cage, and so usable for simultaneous diagnostic and/or therapeutic activities; which has such functional and dimensional characteristics as to allow a considerable adaptability to different environmental conditions; which can be easily carried and assembled and, when needed, dismantled and transferred from a room to another; which has a wide opening for carrying in/out the equipment and the patient, even on a stretcher; which is provided with opening means that can be opened/closed without increasing the dimensions of the cage and disposed so that they can be located at the entrance of the room housing the cage; said opening/closing means having such characteristics as to attenuate the noise suppression level, when in the closed condition; which has a light weight; which allows a good communication with the outside environment with reference to the elimination of equipment heat, to moisture, lighting, venting conditions, and to the possibility of direct verbal communication, and such as to avoid the need to provide the cage with its own lighting and air-conditioning means, potential sources of additional noise and causes of cost increase; which has a safe use.
The invention achieves the above objects by providing a Faraday cage as described hereinbefore, having the form of a prefabricated room or cabinet, which can be easily assembled inside existing premises, and when needed, as easily dismantled.
The cage may be composed of prefabricated members which may be assembled together without requiring building works and can be installed/dismantled with no masonry works.
The prefabricated members may be made of an electrically conductive material, preferably metal, and be connected to each other by electrically conductive connection means, also preferably made of metal. Advantageously, these means may generate electric contact between the construction parts, upon mechanical connection.
The cage and/or the prefabricated parts may have a modular construction. Particularly, a limited number of different types of substantially identical construction parts, within the same type range may be provided. For instance, the walls may all be made by assembling parts of the same type, and the same may be provided, for instance, for opening/closing means.
Thanks to the above arrangements, a Faraday cage may be provided, particularly for MRI applications which, besides providing an effective electromagnetic shield against all noise interfering with imaging operations, can be assembled and dismantled inside its designated room without requiring building works and by non qualified personnel. This provides a particularly versatile and economical installation of the cage, and allows to simplify or even avoid bureaucracy for building works, e.g. when it is located in buildings of historical and/or artistic interest.
A further advantage consists in that the cage can be installed in very large rooms, allowing the creation of a shielding zone of a limited size, and leaving the largest part of the room free for simultaneously performing other diagnostic and/or therapeutic activities. Further, the cage is easy to carry and to assemble, dismantle and transfer from one room to another, thereby allowing to avoid the possible need of permanently equipping a room for this specific purpose.
Thanks to its modular construction, the cage is very economical in terms of industrial manufacture, due to the reduced number of different required types of construction parts.
In accordance with a preferred embodiment, both lateral and ceiling walls may be provided with a plurality of apertures in the form of a grating or the like, whose size and arrangement on the surface depends on the required attenuation of electromagnetic noise.
The size/s of the apertures and/or the number thereof and/or the total open surface-to-total closed surface ratio, may be such as to ensure a good air circulation, an excellent transparency to outside light, in combination with a predetermined electromagnetic noise suppression level.
The apertures provide an excellent air circulation, e.g. allowing elimination of equipment heat; allow the penetration of outside light, avoiding the need to equip the cage with independent lighting and/or air-conditioning means, which are potential sources of additional noise.
According to a further advantageous improvement, the cage may have at least one door in one or more predetermined areas of one or more side walls.
The frame or the peripheral ledges of the door wings and/or the corresponding contact and/or abutment edges of the side frames may be provided with electric contact generating means along their extensions.
These electric contact generating means may consist, at least partially and/or at least on the wing and/or at least on the side frame, of electric contact generating means which may be elastically stressed against the contact surface and/or wiping contact generating means.
These arrangements provide that the wings have a good electric continuity between each other and between each of them and its respective side frame part, such that, in the closed condition, sufficient electric conductivity characteristics can be maintained. More particularly, the cage part/s provided with entrances have the same shielding characteristics as all the other parts of the cage.
In accordance with a preferred embodiment, the cage may have at least four sides, whereof two parallel sides and one transverse side are rectilinear. The side opposite to
Carrozzi Alessandro
Diaferia Leonardo
Burns Doane Swecker & Mathis L.L.P.
Esaote SpA
Patidar Jay
Shrivastav Brij B.
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