MRI Shielding

Wardray Premise are experts in RF and Magnetic Shielding for MRI Rooms. We are the only British manufacturer of RF cages and have completed over 200 installations for all major equipment manufacturers over the last 20 years.

MRI Window
MRI Door
MRI Window
MRI Window

Using a series of purpose-made components produced from the highest quality materials, each cage is designed and manufactured in our modern UK factory to suit the site conditions and satisfy the requirements of each individual contract.

We have also completed a number of modifications to existing MRI Rooms. In addition to conducting RF tests for our own cages, we are pleased to carry out independent tests on other sites and mobile units.

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Room Construction

Our shielding structure is a unique modular system using series of purpose made components produced from the highest quality materials. The self supporting aluminium structure is designed, manufactured and installed under our strict quality control.

Our cage is produced from a series of single and multiple extruded aluminium tube sections locked together with special brackets to form a rigid frame of walls, ceiling and floor. The floor frame is infilled with high density boards to give a flush finish. Additional supporting pads for the magnet can be introduced if necessary. The internal surfaces of the frame are lined with aluminium sheet, locked into the threaded groove in the extrusion with a face fixed moulded aluminium cover strip.

This unique system gives a double overlap of the material at each panel joint for the maximum level of performance. Using a construction formed from one rigid material eliminates any problems of structural stressing and flexing through building movement or varying coefficients of expansion. It also eliminates the inherent weakness of timber framework, thinner shielding materials and the problems associated with some clamping systems.

This construction also allows for the easy removal and re-fitting of panels to allow magnet access in the event of an equipment upgrade. Sound installation can be incorporated into the framework of the walls during assembly. We work in close co-operation with site contractors involved in the installation of air conditioning, power, lighting and internal finishes. Alternatively we can contract to provide a complete installation to final fit out stage (working with our sub contractors).

Aluminium has a proven record on a worldwide basis for high specification RF facilities used by leading telecommunication companies in sensitive military installations. It is often the preferred material for high field 3T scanners and for many of the mobile MRI Units now in regular use and subject to the rigours of transportation from site to site.

Each RF cage is produced to suit local site conditions. The rigid construction is easily adapted to overcome late changes in sizes and specification and allows the easy introduction of additional filters.

The finished product exceeds the attenuation levels required by the major equipment manufacturers. Our designs are regularly revised and updated as new scanners are introduced.

The standard thickness of the walls and ceilings is approximately 50mm, excluding any internal finishes. Floor thickness, excluding the final covering but including the 4mm base insulation membrane, is approximately 27mm.

A five year guarantee is offered for attenuation performance, defective materials and workmanship on the enclosure (excluding moving parts and finger strips).

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Doors

The standard single leaf door size gives a clear opening 1183mm wide x 2100mm high. Doors are faced and edged with aluminium with a white powder coat finish. They contain a continuous membrane throughout the door for excellent sound attenuation.

The power operated self-latching system has a multi-layer stainless-steel link mesh wrapped around a flexible acoustic seal fitted to the jambs and head of frame. An operation light indicates if the door is locked or unlocked. A manual override handle is included in the event of a power failure.

MRI DoorMRI Door Handle
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Observation Windows

Our observation windows are constructed from two pieces of glass, each containing a thin layer of blackened copper mesh with an anti-reflective coating. They are glazed and laminated to form a complete window unit which is integrated into an aluminium frame.

The space between the two window sections gives enhanced RF and sound attenuation and is designed to eliminate moiré fringes.

Our standard window sizes are shown in the table.

Observation Window
Standard Window Sizes
WidthHeight
1200mm900mm
1500mm900mm
1800mm900mm
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Filters and Wave Guides

Air Conditioning Filters

All air conditioning must enter and leave the cage through suitably approved RF filters. These are available in several stock sizes.

Galvanic separation is achieved by the inclusion of a timber frame fitted on the outside of the cage. A separate equalizing vent filter is fitted (usually above the door) to alleviate any vacuum effect within the room.

Electrical Filters

Filters are available with either 10 amp or 32 amp rating.

They are provided for connection to any supplementary electrical equipment used within the room that cannot be routed through the manufacturers' service panel.

Open Wave Guides

These consist of access tubes in varying diameters and lengths, are easily installed and preserve the integrity of the shield.

Medical Gas Filters

These are engineered to meet medical gas standard HTM 02-01. Constructed with anti-static connections, they have been pressure tested for 1.5 hours at a maintained pressure of 150psi.

Service Panel Frames and Quench Pipe Filters

These are produced to suit individual manufacturers’ specifications.

Any specific requirements for floor supports for the magnet and/or ducting within the flooring for services can also be included.

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Magnetic Shielding

The addition of magnetic shielding to MR suites will depend on the type of MRI equipment and the location of the site.

If the proposed location of the scanner allows the 0.5 gauss line of the magnetic field to extend outside the room this can have serious implications; affecting members of the public with implants or pacemakers, Causing disturbance to TV’s, computer monitors, ultrasound scanners, etc.

In addition, interference to the operation of the MR scanner may be caused by traffic, lift shafts or any other moving object with a high level of ferrous magnetic metals.

In both instances, unless the room can be re-located, magnetic shielding is the only option. The need for this will be based on the position of the magnet within the room and the areas outside to be shielded.

The introduction of a ferrous metal with a high permeability will contain the magnetic field (e.g. galvanised, low carbon or silicone steel) by distorting the magnetic field.

This may cause the gauss line to extend outside another part of the room. Therefore it is necessary to undertake a complete survey using a range of multiple finite element calculations to achieve an optimum shielding performance.

This simulation will identify the thickness of the material to be used and the extent of the shielding required in specified wall, ceiling and floor areas.

We would be pleased to provide a full survey, complete specification and quotation for the supply and installation of this work on request.

To undertake this survey it is necessary to provide full details of the proposed room layout from the equipment manufacturer, together with details of the host room and its relative position to the surrounding facilities.

Magnetic shieldingMagnetic shielding
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RF Testing

Wardray Premise have developed their own in-house testing facility in conjunction with leading EMC analysts. Using sophisticated RF test equipment, our construction methods have been refined to obtain attenuation levels at the wide range of frequencies now specified by the leading equipment manufacturers. These levels are far in excess of their current requirements which leave us well equipped to produce rooms for higher powered magnets.

Optional magnetic shielding, including all necessary calculations, can also be supplied and installed on request to suit specific site conditions. In addition to conducting RF tests for our own cages we are always pleased to carry out independent tests on other sites and in mobile units.

MRI cage construction
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Upgrading Existing Facilities

The Wardray Premise cage is particularly suitable for modification when equipment is upgraded.

An RF test is undertaken to confirm acceptable attenuation levels and our work can include providing new filter panel frames, floor supports etc. to meet the requirements of the new equipment. This work can also include the installation of an emergency venting panel within the door.

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Enquiry Guide

To help us provide an accurate quotation, please supply the following information with your enquiry:

  • If available, please provide a drawing or dimensioned sketch.
  • Proposed equipment manufacturer if known and type of equipment, model number etc including site planning guide.
  • Types and quantities of any special filters required.
  • Window size
  • Requirement for magnetic shielding.