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MRI Installation – Hutt Hospital 2014
Original scanner undergoing demagnetisation - 2014
MRI first came to Hutt Hospital in 2007. The new Philips Achieva Pulsar 1.5T Scanner was installed on the ground floor of the Heretaunga Block in an area first occupied by the telephone operators in 1981, when the new clinical services block opened. Following various iterations, latterly the Hutt Valley’s first Breast Screening service, the now vacant area was readied for the installation of the new scanner.
The room required a solid concrete foundation to support the 6 tonne weight of the scanner. A hole was cut in the concrete floor, and a plinth poured in the centre area of the room where the scanner would sit. The new room then received the Faraday treatment – the entire room was lined with copper foil to form a faraday cage to prevent outside RF from interfering with the scanner.
The scanner arrived under clear skies, having flown from the Netherlands and travelled by road from Auckland. There is a limit to the time that an MRI scanner can continue to be viable once it is disconnected from the liquid helium cooling system. The helium is used to keep the superconductor cold – very cold at −269 °C. Whilst being transported without a cooling compressor the helium boils off until it reaches the point of no return - the scanner will then need to be taken back to the USA for refilling with the rare gas. MRI scanners can be topped up locally with liquid or gaseous helium, but they cannot be totally refilled in the southern hemisphere.
The New Magnet
Move forward seven years. The decision was made to upgrade the scanner, and a Philips Ingenia 1.5HT scanner was chosen. The machine was supplied under a lease agreement.
At first glance it would seem relatively simple to replace an item of equipment when the infrastructure was already in place. Not so.
The removal/ installation plan was straight forward. Reopen the hole through the front wall, slip the old scanner out and put the new one in. However, things are never that simple.
One month was allowed from last patient scanned on the old machine to first patient scanned on the new machine. This included 2 weeks for Philips to commission and test the new MRI.
Chilled Water System
The old scanner was cooled using the building chilled water system. This had worked, but problems had been identified including reliability of the chilled water supply and backup cooling. The only contingency in the event of cooling water failure was to use town water. This is a normal option, but in our case it was the only option. We decided we needed one more stage of redundancy.
The solution was to install a stand-alone Aquacooler chiller as the main cooling system. The secondary cooling would be supplied from the building chillers, with the last resort being town water.
All this required a redesign of the pipework and the control system. Difficulties were encountered with the change over valves, but generally the process went smoothly.
The requirement was for a constant temperature (21 deg) and humidity (40 to 60% RH) at all times. The existing system was troublesome. It consisted of an air handling unit on the roof with 4.5 kW of electric heating elements, a split system chiller and a 5kg/hr electric humidifier.
The control had been erratic, and suspicion lay with the location of the duct thermostat.
The electric elements were upgraded to 9kW, but the rest of the system remained largely unchanged except for upgrading the controls. Problems were encountered with the solid state relay used to control the elements. The 40 Amp Omron relay started to overheat and fail when working hard. Upgrading it to a 60 Amp unit solved the problem.
Faraday Cage Installation 2007
Opening the wall meant that the shielding provided by the copper faraday cage had to be reinstated. The openings for the different services (cables, cooling etc) also need to be altered. The cage provides protection from external RF interference of the magnet, and is a precise science. The specialist work is carried out by Farady Pty Ltd from Australia, and is time consuming.
The flooring vinyl was replaced under the magnet following work by Faraday.
The building contractor was charged with opening the access route, propping under the floor (to take the 6 tonne weight of the magnets as they were rolled out and in), laying of steel plates for the magnets to roll over as they were moved in and out, and all finishing work.
Removing the Old Magnet 2014
The move of both magnets was the responsibility of Hitech Asia Pacific. These people, specialists in the field of moving expensive technology, took care of the whole process without fuss. They made a difficult job look easy.
Installation and Commissioning
Installing the New Magnet 2014
The installation and commissioning roles were shared between Philips and Gailing, an American based company. Two technicians form Gailing travelled from Nebraska to install the cables and pipes. Philips handled all the finer work and the commissioning.
Of note was the method of demagnetising the old magnet. The process, following power shutdown, was to connect a special resister to bleed the energy from the super conductor. The process took 4 hours, but without the resistor, the magnetic field would remain for about 6 days.
The new magnet is now operating successfully. Teething problems have been largely ironed out but, with hindsight, the HVAC system could have been completely replaced, rather than using the existing equipment. Building fed cooling and heating coils would have been a more expensive but more robust option.
The New Magnet - Exquisite Workmanship
New MRI Magnet in Place
By the way, the old MRI has gone back to Europe for refurbishment and sale for continued use by others. The installation (excluding the actual MRI) cost several hundred thousand dollars.
Max Christensen – HVDHB Building and Property Services
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