Ingenuity wins the horse race

A new, small MRI machine has been especially developed for diagnosing problems in horses. Horses are large animals, rather than develop a king-sized machines likely cost millions of pounds each, Hallmarq Veterinary Imaging, working with Precision Engineering Design, based in Woking, has developed a relatively small machine with a horse-shoe shaped magnet that engages with radio frequency coils designed to fit over horse's hooves or legs. The idea started when Dr Nick Bolas, who had 22 years experience in the MRI business, set up the company to improve diagnosis of lameness in horses, a problem he was very familiar with as a horse owner, with colleague Dr David Taylor. There had been instances where veterinary practices had anaesthetised valuable horses, and inserted the legs into a human MRI scanner but this is a difficult method of diagnosing whatever problem a horse may be having with its legs when it stands up, and horses do not always survive being anaesthetised. Paul Kurn, director of PED told us that Dr Bolas originally came to PED with a 'Meccano' model showing how he wanted the machine to work, and a 1/10 scale model of a horse. The magnet was to form a 800kg off centre load that would have to be movable in the three spatial axes and also rotated if required. Standing in front of the original prototype machine, installed at Dr Bolas's local practice, the Bell Equine Veterinary Clinic in Mereworth, Kent, Paul Kurn told us that be believes he secured the design, manufacture and build contract because they showed originality of ideas and were quickly able to model the outline design in SolidWorks and show a realistic 3D model to his client, whereas his competitors were only able to supply 2D sketches. The machine as supplied now has a 1 tonne US made magnet (Chinese products were just not good enough) with a working sphere of about 130mm to 140mm diameter. Field strength is 0.27 Tesla, excited at 11 MHz. Field homogeneity, we were told, has to be better than 20 parts per million, and the system is calibrated to a fixed temperature, usually 20 deg C. The magnet is carried on IKO linear slides, supported on frames from MK Profile Systems reinforced with steel plates. The main rotational bearing is a cross roller radial mounted bearing from IKO. Geared drive motors are made by Rossi Motoriduttori driven by a bank of Eurotherm drives. The castings and 'C' rails were all FEA analysed using COSMOS prior to finalising design and manufacture. The RF coil pickups were designed in SolidWorks and the computer models used to directly create mould tools. Some bespoke machined items were also machined directly from SolidWorks models. Because the coils have to be opened to be placed around the horse's hoof or leg, and then accurately closed to achieve electrical continuity, the opening and closing action was tested on a special rig through 14,000 operations over a week. The system is run by a Pentium IV rack mounted industrial PC which communicates with Hallmarq over the Internet, to allow monitoring of usage, which is billed to the client clinic, as well as providing the opportunity to monitor correct functioning, and download updates. One of the clever aspects of the software is that unlike a human MRI system, it includes algorithms that compensate for patient movement during scanning. The horses are only sedated, not anaesthetised, and some of them apparently remain quite frisky. Scans take from 40s to 6 minutes, and are already proving invaluable in the diagnosis of causes of lameness, whether the horse is an expensive race horse or more often, somebody's daughter's favourite. So far, 27 machines have been built, 18 in the last year, with growing interest and sales in the USA. Precision Engineering Design Pointers * Machine applies the MRI scanner to the appropriate part of the horse instead of trying to put the horse in a scanner * The result is a machine that is much smaller and much less expensive and is able to diagnose 60 per cent of the problems that cause a horse to be brought to a veterinary clinic.