MRI scanners are a key diagnostic tool but they are big, very heavy and need liquid helium to cool them. Neoscan Solutions invented an MRI scanner much smaller and lighter which could be placed directly in the children's ward of the hospital, to keep journeys short and to scan sick babies in their sleep. The key to the much smaller MRI scanner design is the use of digitizers and arbitrary waveform generators (AWGs) by Spectrum Instrumentation that offer sub nano-second, coherence precision to generate the scanner-signals and capture the results.
Current MRI scanners weigh around eight tons and therefore need to be located on floors that can take this weight, which means either specially reinforced floors or locating them in a basement. They also require ca. 40 m² for the scanner and all the support equipment. Lastly, they need to be supercooled with liquid helium, which needs special handling.
"Having worked with MRI scanners for many years, I recognised the problem," explained Dr. Stefan Roell, founder of Neoscan Solutions in Germany. "Scanning a sick child usually means a long journey out of the ward to the scanner and babies may need support equipment that is not easily transportable. Because of this, sometimes an MRI-scan is not even done. We have designed an MRI scanner specifically for newborns and infants which means that the hole in the middle is only 30 cm in diameter, not 60 cm. As a result, the scanner is much smaller (170 x 150 x 110 cm) and can go through standard doorways. With a weight of only 2000 kg, it can be located on standard floors and, needing only 10 m², it can be installed in a spare room directly on the children's ward. Carrying a sleeping baby only a few meters to the MRI is a big advantage, saving a long journey through the building and the need for sedatives to keep the baby motionless for the scan."
The technology and field strength of the Neoscan machine is identical to current scanners so that no new clinical studies are required to validate it. Achieving this needed several innovations by the company. Firstly, to shrink the size, the team had to develop a dry magnet that would create the standard 1.5 Tesla field inside the hole, but without requiring liquid helium. This is done by an inner, cylindrical magnet generating 2.5 T and then an outer cylindrical magnet that counteracts the inner field to provide strong, active magnet shielding so that there are no stray magnetic field left beyond about 1 m from the device's cover.
The second innovation was in the control electronics. Current MRI scanners typically require three big racks of specially developed electronics, that have been custom designed and built by the MRI manufacturer. Neoscan Solutions chose a different approach. The team uses a PC which runs the software that Neoscan has created plus high-end measurement PC-cards from Spectrum Instrumentation. The signals for the MRI are generated by the M4i.6620-x8 and M2p.6546-x4 AWGs and then analysed using an M2p.5968-x4 digitizer. The system uses Spectrum's SCAPP software drivers that enable a graphics processor with 5,000 cores to perform the parallel processing, instead of using only 8 or 16 cores of a normal CPU.
Sub nano-second precision of Spectrum cards
"As a start-up, we could not afford to create specialized hardware and so we used this route of high-quality, standard cards providing a platform to run our software on," added Dr. Roell. "This meant that we could focus our skills on the software development with very fast development cycles in the knowledge that the hardware was already tried and tested. This was only possible because of the design quality of the Spectrum cards. For MRI, it is vital that there is phase coherence in the 64 MHz signals, otherwise there will be cancellation effects. In practice, that means that the AWG and matching digitizer have to have sub-nanosecond coherence precision, which the Spectrum cards achieve. During the research phase, it was hard to determine this from the specifications of the cards provided by the various suppliers that we contacted, as it is a rather unusual level of detail. However, Spectrum was outstanding in helping us with technical support both in the specification of the best cards to use and then again during the implementation. A rival proposal took weeks longer to arrive and was grossly over-specified and over-priced as they had not made the effort to understand the detail of our project." Neoscan will be shortly installing its first devices in German hospitals where it can be seen in operation by prospective customers as it takes images of babies. The certification process with a CE mark is expected to be completed before the end of 2021.