Title: Transverse field MRI for magic angle imaging
Funder: Department of Health (England)

Abstract: The main aspects of the project are as follows. 1 – Magnetic design and optimization The magnetic design is challenging due to the unconventional, non-axisymmetric configuration. Each pole of the open magnet comprises two halves, represented by permanent magnets arranged with opposite polarity. The poles are mirror images of each other, resulting in a field parallel to the pole faces, rather than perpendicular. The idea has been previously successfully exploited in a very low field electromagnet, while design studies have shown that the approach is also valid using rare earth permanent magnets. The minimum design targets are field 0.15 T, DSV 150 mm, pole gap 250 mm. We have previously developed advanced software for magnet design and optimization and used it successfully in several challenging designs. It provides magnet configuration control and generates 2D and 3D design instances and interfaces with specialist FE solvers (Comsol, Vector Fields). 2 – Mechanical structure and actuation Mechanical structure supporting the pole pieces and providing actuated rotation about 2 axes will be designed using computational tools in order to ensure adequate stiffness and vibration characteristics. Detailed design involving bearings and transmission will be carried out. We propose the use of standard industrial servomotors equipped with brakes, so that they can be fully switched off during imaging. 3 – Magnet manufacture and shimming The magnet will be manufactured by the industrial partner who specializes in the manufacture of precision assemblies of permanent magnets. They will also build all special tooling necessary for handling magnetized blocks during assembly. They will also manufacture the aluminium support structure carrying the pole pieces. 4 – Gradient coil design and manufacture The required gradient coil geometry is achievable, although one axis involves more complex windings. The detailed design will be carried out using the described electromagnetic simulation tools. Manufacture is envisaged to involve predominantly sheet copper, although we will consider using one of the gradient coils to provide water cooling for improved temperature stability. 5 – RF front end design and manufacture RF coils will be mounted on the poles and the basic design will not pose significant challenges. However, we shall also develop a cryocooled coil set as an option, offering potentially several-fold improvement in SNR. Being pole-mounted, insulation and management of the cold mass will be made more practical. Further refinements of the coil mountings are envisaged, such as adjusting the distance of the coil position from the tissue. 6 – MRI system integration The spectrometer, including gradient amplifiers and RF amplifier, is already available at Imperial College and it is currently used with another MRI magnet of similar field strength. The main hardware modifications will involve inclusion of additional modules for actuator control. Modifications and extension of imaging sequences will be performed in line with imaging requirements and registration of data sets obtained at different field orientations. 7 – Software development, data fusion Images generated in standard DICOM format will be registered and fused into a single 3D dataset. Volume visualization with controllable transparency and arbitrary cross-sections selected by the user will be provided. The final version of the software will be implemented in C++ for speed and robustness, using standard graphics libraries such as VTK. 8 – Evaluation trials System trials will initially involve phantom studies, followed by trials on healthy volunteers. We are also planning trials involving orthopaedic patients such as those suffering from knee and ankle injuries. 9 – Commercialisation & IP Activities will include IP protection, preparation of documentation for future regulatory approval, establishment of links with potential manufacturing and marketing partners, user group establishment and preparation of the business plan.


Research activity codes: 4.1 DISCOVERY AND PRECLINICAL TESTING OF MARKERS AND TECHNOLOGIES
Health categories: MUSCULOSKELETAL