MCODE

Multiphysics Coil Design: Applications in Novel Magnetic Resonance Imaging Systems

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 Obiettivo del progetto (Objective)

'Magnetic resonance imaging (MRI) systems are essential tools for the diagnosis of a wide range of medical conditions. Recent developments in MRI technology have seen a move towards novel systems dedicated to particular medical niches, such as ultra-high field systems, combined MRI-positron emission tomography (PET) scanners and systems for musculoskeletal or brain imaging. These novel systems require radical redesign of the MRI hardware, including one essential sub-system known as the gradient coils. The gradient coils produce images from signals coming from the subject through frequency encoding of the MR signal.

Current design methods for gradient coils optimise electromagnetic properties and then empirical testing is needed to ensure that the designs are practical and safe. This is fine for standard MRI systems but the complexity of novel MRI systems means that this is likely to result in suboptimal gradient coils. In this project, we will incorporate a number of properties other than electromagnetics into the design of gradient coils, including temperature, vibration and practical manufacturing constraints. This will ensure optimal performance of gradient coils in novel MRI systems. Preliminary experiments have seen more than 100% improvement in performance in cases where the size of the wire in the coil limits performance. Improved performance of the gradient sub-system will allow increased image resolution, shorter scan times and importantly, will make more novel systems feasible.

The project requires development of appropriate models of the physics, software development, empirical validation and the production of gradient coils for a 9.4 T MR-PET system. The outcomes will be a greater understanding of the thermodynamic and vibration processes in gradient coils, new knowledge about the possibility for reduced temperature, vibration and acoustic noise and the production of gradient coils with improved performance to enable new methods in metabolic imaging.'

Introduzione (Teaser)

Novel magnetic resonance imaging (MRI) systems tailor-made to specific medical applications require substantial re-engineering of the MRI hardware, particularly the gradient coils. Mathematical optimisation techniques could speed development.

Descrizione progetto (Article)

MRI is a non-invasive imaging technique that does not use ionising radiation. MRI tools have become essential to the diagnosis of many medical conditions and have provided a new window on tissues in health and disease. Currently, redesign of the magnetic coil for specialised applications focuses exclusively on electromagnetic properties followed by extensive empirical testing, resulting in suboptimal gradient coils.

Thanks to the EU-funded project 'Multiphysics coil design: Applications in novel magnetic resonance imaging systems' (MCODE), the groundwork has been laid to exploit the physics of thermodynamics together with electromagnetic considerations. Multiphysics considerations are expected to reduce temperature, vibration and noise. The result will be greater image resolution, shorter scan times and, importantly, enhanced feasibility of even more novel and specialised systems.

Team members first developed code that was designed to be compatible with the inverse boundary element method (IBEM) code for coil design. IBEM simulates the temperature of electromagnetic coils and has been employed to address concerns over the increase in field strength of gradients used in MRI. Predicted temperatures (the forward simulation) were in excellent agreement with those measured experimentally using a thermal imaging camera.

The next step was the inverse problem, using the temperature predictions to guide designs for lower (actually lowest or minimum) maximum temperature to enable the higher duty cycles required of novel MRI methods. Scientists developed software to optimise the minimum maximum temperature in a coil subject to creation of a given magnetic field.

Researchers then used this software on a standard MRI coil, conducting simulations with different thermodynamic parameters. Coils were redesigned using the minimum maximum temperature optimisation and a much lower peak temperature was predicted.

MCODE has created and demonstrated the value of mathematical optimisation software that takes into account thermodynamics in the design of MRI coils for specialised applications. Uptake of the technology by MRI manufacturers should open new markets for high-performance MRI systems that support better diagnosis of important medical conditions in trauma and disease.