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Emerging Imaging

High-performance clinical structural and metabolic MRI using advanced neuroimaging engineering methods

Project ID: 2022_039

1st Supervisor: Özlem Ipek, King’s College London
2nd Supervisor: Enrico de Vita, King’s College London
Clinical Supervisor: Vicky Goh

Aim of the PhD Project:

  • Develop the next generation of MRI hardware which enables high-performance structural, functional, and metabolic advanced neuroimaging techniques in a single clinical examination.
  • Apply sophisticated decoupling techniques to combine proton and non-proton radiofrequency coil arrays effectively to bring the clinical ultra-high field MRI to the next level of neuroimaging.

Project description/background:

Ultra-high field MRI systems (7 tesla and above) provides increased signal-to-noise and contrast-to-noise ratio that allow higher spatial resolution and better detection of anatomical and pathological features. The high spatial resolution at 7 tesla has been a game changer for neuroimaging applications not only in MS but also in epilepsy, brain tumours, dementia and neurodegenerative disorders. While there are a few magnetically detectable nuclei including sodium (23Na), phosphorous (31P), oxygen (17O) and others, proton (1H) has the largest gyromagnetic ratio and being at 100% abundance, has the greatest sensitivity for clinical use. The non-proton MRI provides the opportunity to assess functional tissue information. For example, sodium (23Na) MRI can provide information on cell viability, 31P on the pH value and energy metabolism, and 17O on the oxygen metabolism in tissue. However, due to the low in vivo concentration and low MR sensitivity of these nuclei, non-proton MRI suffers from a very low SNR. This issue can partially be compensated for using higher magnetic field strengths.

Ultra-high field MRI systems (7 tesla and above) offer the potential to provide truly comprehensive anatomical and metabolic imaging in unified examinations. Multi-nuclei spectroscopy offers to probe both anatomy and function using proton signal and metabolism using both proton and another nucleus. Ideally this could be feasible in a single integrated examination with both proton and non-proton channels providing close to optimal performance. In reality the current state of the art results in major loss of performance on both channels, and very dramatically current designs sacrifice almost all the benefits of the proton channel. The current situation is so severe that using a state-of-the-art commercial coil, it is not feasible to perform even standard proton imaging at 7T. Instead, a minimal image acquisition has to be obtained and then the multi-nuclear coil has to be replaced with a proton only coil in other to do a full proton examination and then the has to be aligned in post processing. Thus, currently multi-nuclei examinations actually have to take place in two parts, doubling examination time and making it impossible to fully take advantage of integrated multi-nuclei operation, such a using proton observation or interleaved readouts.

This proposal aims to apply sophisticated decoupling techniques to combine proton and non-proton radiofrequency coil arrays effectively. The main contribution of this work is that proton imaging will be achieved using one coil structure only, i.e.  no swapping of MRI coils would be required. Thus, the techniques proposed will overcome the methodological weaknesses that are currently preventing non-proton imaging being used clinically. The main output would be improved apparent spatial resolution and quantification in the ultra-high field scanners that have recently reached the market. This would result in, for example, earlier diagnosis and more accurate staging of tumors in oncology and advancement in functional and metabolic advanced neuroimaging.

A suitable candidate ideally has a strong physical science background (engineering, physics) with a particular interest in medicine and physiology, and ideally previous experience in biomedical/radiofrequency/microwave engineering.

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