Magnet systems

The magnet group develops cryogen-free superconducting magnet systems for magnetic resonance applications.

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The magnet systems group develops magnetic resonance (MR) systems based around cryogen free superconducting magnet systems, helping to unlock new applications for this versatile measurement technique. Robinson Research Institute’s (RRI) longstanding capabilities in applied superconductivity and our collaborations with industry partners such as HTS-110 and Fabrum Solutions, enables RRI to design, manufacture, and integrate complete magnetic resonance systems.

Our particular focus has been in developing complete magnetic resonance imaging (MRI) systems in-house. As such, we have proven design and manufacture capabilities in cryogen-free superconducting magnets, gradient coils, passive shimming, and radio-frequency coils.

Traditional superconducting magnets used in MR imaging and spectroscopy are typically cooled with liquid cryogens, in particular liquid helium. This is operationally cumbersome for both the manufacturer and user, and in recent years, helium has become increasingly scarce and expensive. By contrast, cryogen free magnets use a cryocooler—a specialised refrigerator to cool the magnets by conduction cooling alone. This totally eliminates all liquid cryogens, and allows superconducting magnets to operate simply from an AC power connection.

Our novel magnetic resonance imaging systems use 3 T compact cryogen-free magnets, featuring room temperature bores and field strengths in the range 160 mm / 3 T to 850 mm / 0.7 T. The magnets have minimal fringe magnetic field, and can incorporate an integrated RF screen meaning our MRI systems don't require a dedicated screened room and can be located in a standard laboratory with other instruments. Because they operate without the large, permanent infrastructure necessary to support standard MRI machines, our systems offer a practical alternative for research or commercial facilities.

Human extremity MRI

In 2013 we completed the construction of a 1.5 T MRI system to image human extremities. It is based on a 240 mm warm bore solenoid constructed from YBCO HTS, which was designed and manufactured in collaboration between Robinson Research Institute and HTS-110. It is believed to be the world’s first fully functional MRI system utilising a YBCO magnet.

This system was used as a test bed to demonstrate the performance of YBCO based MRI magnets. In particular we investigated the effect on magnetic field uniformity and stability, vital to MRI performance, in light of transient screening currents induced in the HTS coils during ramp to field field. We also investigated the potential use of simple unshielded gradient coils to reduce overall system cost and complexity.

We have subsequently repackaged the 1.5 T for use in industrial environments, where it has been used successfully to undertake pilot MRI trials for meat quality assurance work.

3 T preclinical MRI

Robinson Research Institute in collaboration with HTS-110 have developed a 160 mm bore 3 T cryogen-free MRI system, using BSCCO HTS wire, suitable for small animal imaging or other applications requiring a high-field, small bore magnet. The system is virtually self-shielded and can operate from a single phase AC electrical supply. We are working with our partners Fine Instrument Technology in Brazil to bring the system to market.

Brain imaging magnet

As part of a project led by the internationally acclaimed Centre for Magnetic Resonance Research at the University of Minnesota, RRI is developing a smaller and more mobile MRI system that will support neurological research. The brain imaging MRI system will be worn like a motorcycle helmet, with an opening for the subject to look out of. This will have significant benefits for functional MRI studies since it will enable the subject to move more freely, perform a range of activities, and respond to stimuli in a more natural way than is possible in the large constrictive MRI machines currently used in most hospitals. The project will utilise RRI's high-temperature superconductor magnet technology in combination with technology from our collaborators at University of Minnesota, Columbia University, Yale, and University of Sao Paulo.

Portable Low-Field NMR Brain Monitoring Device

Medical professionals who treat brain injuries caused by trauma or oxygen deprivation are often ‘blind’ to the underlying disease processes because existing technologies for detecting brain injury are invasive, inaccurate, or inaccessibly expensive. We have combined outstanding New Zealand-based MR science and biomedical expertise to develop a portable device that enables early detection and targeted treatment of brain injuries.

Like MRI, our technology exploits magnetic resonance principles to infer tissue properties. But instead of using expensive superconducting magnets to generate an image, our invention uses low-cost permanent magnet assemblies to detect injury biomarkers. We have already been able to demonstrate that our device can infer oxygen content in the tissue, and presently we are extending the capabilities of the sensor to also detect perfusion (blood flow) and diffusion (tissue vitality).

Currently, no portable device can dynamically track diffusion, and devices for monitoring perfusion and oxygenation are invasive or lack tissue penetration. A non-invasive device that could track all three biomarkers of ischaemic injury, and probe superficial, as well as deep brain structures, would transform brain injury diagnostics.

Development work

As part of our ongoing research into cryogen-free magnetic resonance systems, we have developed the capability to design and manufacture cryogen-free low temperature superconducting (LTS) magnet systems. In part supported by a funding from Kiwinet, we have used this capability to manufacture a half-scale version of the brain imaging magnet to be manufactured for University of Minnesota to test several aspects of the novel brain imaging magnet architecture. In the future, the capability to manufacture LTS magnets will allow us to manufacture cost-effective magnet solutions either as proof-of-concept magnets, or when new markets, for example as identified via our collaboration with FIT, demand low-cost magnet solutions.