Magnet systems

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

MRI magnet

The aim of our magnet research programme is to provide compact, cryogen-free magnets with field quality suitable for magnetic resonance (MR) applications, such as medical imaging and spectroscopy.

Traditional superconducting magnets used in MR imaging and spectroscopy require cryogenic cooling using liquid helium, which is operationally cumbersome for both the manufacturer and user, and helium has suffered significant global supply disruption and cost increases in recent years. Liquid helium can be eliminated by appropriate use of modern cryogenic refrigerators and new superconducting wire technology, but the MR system needs to be adapted accordingly.

We have successfully demonstrated MR imaging of human extremities using a high temperature superconducting (HTS) magnet based on YBCO wire, and are currently researching opportunities for both higher field / smaller bore magnets and lower field / larger bore magnets utilising MgB2 and Nb3Sn. These materials are superconducting in a temperature range that can be achieved with conduction cooling. The magnet systems only require water cooling and three-phase power, and can be ramped to field when required by the user without service support.

Our novel magnetic resonance imaging (MRI) system prototypes are compact and potentially portable, featuring room temperature bores and field strengths in the range 160 mm / 3 T to 850 mm / 0.7 T.

System development

Each component of the MRI system has been designed specifically to suit the cryogen-free magnet. We have developed novel gradient coils, shimming and magnet power supply solutions optimised for HTS magnets. This approach allows us to develop cost effective and complete MRI system solutions.

Hardware partners

We are working on a number of MRI hardware development programmes with international collaborators. In New Zealand, we work closely with our industrial partners HTS-110 Ltd and Fabrum Solutions Ltd to deliver prototype instruments for development applications.

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, which was designed and manufactured in house using YBCO conductor. This is believed to be the world’s first fully functional MRI system utilising a YBCO magnet.

The magnet, gradient coils, radio frequency coils and shim hardware were all developed within the group. This system is used as a test bed to develop electronics and hardware that are optimised for HTS magnets.

Our research programme is currently investigating the impact of the transient screening currents induced in the HTS coils during ramping on field stability and homogeneity, and the potential use of simple unshielded gradient coils to reduce overall system cost.

Development projects

3 T preclinical MRI

We are currently developing a 160 mm bore 3 T magnet suitable for small animal imaging using BSCCO wire. This accessible MRI technology will facilitate high-throughput preclinical screening for drug trials and pharmaceutical research.

The compact cryogen-free magnet has minimal fringe magnetic field, which allows it to be located in a standard laboratory with other instruments. No special provisions need to be made to the building’s infrastructure (for example, no screened room or helium quench ducting are required), and only single phase power and water cooling are required. The magnet system can easily be de-energised and moved between locations as required by the user without service support.

Transportable human MRI

A transportable whole-body human MRI system concept has been developed for use outside a traditional hospital setting. The 0.7 T MgB2 magnet is cooled using cryogen-free refrigeration technology to overcome many of the logistical problems that are associated with the use of liquid helium in traditional mobile MRIs. The entire MRI system can be packaged within a 20ft shipping container for ease of transport.

We are currently seeking industrial partners to take this concept forward to prototype trials.