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Publication Date: 2010-Sep-30
Document File: 6 page(s) / 220K

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A technique for manufacturing a hybrid design MR bridge is disclosed. The technique described herein provides a simple and cost effective technique to achieve a hybrid - hand layup and pultrusion-composite for enhanced structural performance of an MR bridge. The technique provides an MR bridge, which has load carrying capacity of up to 550lbs and high stiffness. Pultrusion of composites is selected for reinforcing certain regions of the bridge in order to withstand high stresses. Fiber reinforced composite hand lay-up layers provide enhanced stiffness and load carrying strength in other regions of the MR bridge. The fiber reinforced composite hand lay-up layers can also be replaced by any other fiber reinforced composite processes like Resin Transfer Molding (RTM), Resin Infusion or Vacuum assisted RTM. Such a design is simple, cost effective and provides good functionality and structural performance.

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The invention generally relates to medical imaging systems and more particularly to a technique for manufacturing a magnetic resonance bridge with enhanced stiffness.


A magnetic resonance (MR) bridge is an important part of an MR system. The MR bridge is a patient load-carrying structure. The MR bridge is a fixed member and a patient is usually transferred from an MR table by a cradle mechanism to the MR bridge. The patient lies on the cradle and moves in/out of the magnet bore over the MR bridge for the MR scanning procedure.

MR systems require the MR bridge material to be non-magnetic and non-conductive. Hence it is difficult to achieve an MR bridge with the required stiffness to withstand patient load. Fiber reinforced composite materials are a suitable option for use in the MR bridge. High stiffness fiber such as carbon is available for different structural applications but being conductive it is not suitable for application in an MR bridge.

Performance requirements of the MR bridge are a patient load tolerance of about 550 pounds (lbs) to be transferred to the MR bridge from the cradle. The bridge measures 1.9 meter (m) in length and remains unsupported inside the magnet bore. Deflection of bridge is very critical parameter with 550lbs load acting on it. The vertical deflection at any point of the bridge should be less than 3mm to avoid interference between bridge and Magnet bore. Hence appropriate stiffness of the MR bridge is critical for high quality MR images.

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Conventionally, pultrusion is utilized in the production of MR bridges. In such a technique, the entire cross section of the MR bride is pultruded. Pultrusion is a well- established technique for composites to achieve high stiffness structures. However, complexity in the controlling of the pultrusion process and tools for production of MR bridge makes it a very expensive process. Further, for certain structural member incorporation in the MR bridge, additional secondary processes may be required.

In another conventional technique, the MR bridge is a fiber-reinforced composite hand layup type MR bridge. Such MR bridges comprise two open section fiber reinforced composite layers. The hand layup MR bridge design has two separate hand layup layers / skins with open sections which are glued together. A conventional hand layup MR bridge is cost effective but poses limitation on stiffness and can withstand load only up to 350 lbs. However, the current need on stiffness is to enable a 550 lbs patient load tolerance.

Hence there is a need for a cost effective MR bridge design that provides an MR bridge capable of withstanding a 550lbs patient load with a vertical deflection, which does not exceed 3 mm at any point on the MR bridge.


A technique for manufacturing a hybrid design MR bridge is disclosed. The technique described herein, utilizes hybr...