PhD Projects

We are currently looking to recruit able and enthusiastic PhD students to work in MRI and MRS. Apart from following a program of research, students are given formal teaching in relevant aspects of physics from the School of Physics & Astronomy (if appropriate) and in more general topics from the graduate school.

Our postgraduate students are funded from a variety of sources including UK research council grants and funds from the School of Physics & Astronomy.

General information is available on the School admissions pages and the university postgraduate application page. If you are interested in applying then please contact the postgraduate admissions secretary Wendy Brennan  It would be useful if you could state the area of interest to you and attach a CV or summary of your experience. We can then advise you on making a formal application and arranging a visit to the centre.

We are actively recruiting in the following areas:

• Multinuclear Spectroscopy at 3 & 7T
• Single Trial fMRI at 7T
• Magnetoencephalography and its relationship to fMRI
• Investigating brain haemodynamics at 7T
• Imaging brain tumours at 7T
• Combined Electroencephalography (EEG) and functional MRI (fMRI)
• Dynamic Nuclear Polarisation and Microscopic NMR imaging.
• Ultra-fast 2D Spectroscopy Applied To Human Brain Physiology
• Direct Detection of Neuronal Activity
• Whole body imaging
• High Resolution Anatomical Imaging at 7 T
• Combined Transcranial Magnetic Stimulation (TMS) and functional Magnetic Resonance Imaging (fMRI)
• Interaction of Changing Magnetic Fields with the Human Body

The highest field strength brain-imaging scanner in the UK has just be installed at the Sir Peter Mansfield Magnetic Resonance Centre. This 7T scanner, supplied by Philips Medical will be used primarily for functional Magnetic Resonance Imaging (fMRI) of the brain, and will be operated as a national facility for high field fMRI. Imaging at such high field poses a number of technical challenges, but also opens up many new opportunities for studying the way the brain works.

Single Trial fMRI

Professor P Morris, Professor P Gowland and Dr S Francis

Normally fMRI considers the average effect of a repeated action. One of the major benefits of the increased signal to noise ratio at 7T is that it will potentially enable us to perform 'single-trial' fMRI. This will open up the exciting possibility of studying learning responses and rare events. This project will focus on understanding and characterising the different sources of variation in the brain's response to stimulation, which will be necessary in order to be able to detect and interpret the single trial response. It will also aim to devise and test new methods of analysing data to detect single trial responses.

Investigating brain haemodynamics at 7T

Dr S.Francis and Professor P. Gowland

The BOLD effect, which is widely used to study brain function in neuroscience, is caused by co-ordinated changes in blood flow, blood volume and blood oxygenation. However, despite its wide use, the exact nature of the interactions between these parameters is not understood. Furthermore, the variations in these parameters in the resting state of the brain have not been fully characterised. Knowledge of these factors is important firstly to understand the correlated changes in BOLD signal that occur across the brain in the resting state, and which are assumed to relate to neuronal activation. Secondly it is important to understand variations in BOLD signal, for instance do drugs change the BOLD signals we observe due to changes in neuronal activation or changes in underlying blood flow?. The new 7 T human MRI scanner that is currently being installed in the SPMMRC will offer increased sensitivity with which to measure the biophysical parameters relevant to the haemodynamics of the BOLD effect. However this high field scanner will also pose new challenges. The aim of this project will be to develop novel methods for measuring the relevant biophysical parameters at 7T. These will then be used to test new models of the BOLD signal changes using different perturbations, including intravascular contrast agents and vasodilators.

Susceptibility Weighted Imaging at 7T

Professors Richard Bowtell and Penny Gowland

At 7 T, the small differences in the magnetic susceptibility of different tissues in the brain gives rise to interesting contrast in both the magnitude and phase of the magnetic resonance signal that is used to form images, which it has not been possible to exploit previously at lower fields. In particular the phase images show excellent discrimination of cortical grey and white matter, strong differences between cortical grey matter and deep grey matter nuclei and tract-related structure in white matter. This project will focus on understanding the physiologiical origin of these effects (including the relationship to iron content and blood volume), the physics underlying their manifestation (including the possibility of calculating a true magnetic susceptibility image from phase data) and the optimisation of imaging techniques so as to allow best exploitation of this contrast.

Direct Detection of Neuronal Activity

fMRI is currently based on detecting changes in the magnitude of the MR signal which are caused by an increase in blood oxygenation resulting from elevated blood flow in active brain tissue. These haemodynamic changes are delayed by several seconds with respect to the increase in electrical activity in the neurons and also occur over a volume of brain tissue which may be significantly larger in extent than the region showing enhanced neuronal activity. It would therefore be very valuable to be able to use MRI to detect directly the signature of electrical activity in the brain. This is potentially possible because the flow of electric current during neuronal activity generates weak magnetic fields that affect the evolution of the MR signal. The aim of this project is to develop and apply methods of detecting these effects most efficiently. This will include the use of simultaneous EEG recording inside the MR scanner, which provides a concurrent measure of electrical activity. In addition modelling studies will be undertaken to evaluate the expected spatio-temporal form of the neuronally-induced magnetic fields.

Imaging brain tumours at 7T

Professor Penny Gowland, Professor Peter Morris, Dr Susan Francis, Professor Richard Bowtell

Important problems in the management of patients with brain tumours include grading the tumour, and determining the degree of its infiltration into neighbouring tissues. Ultrahigh field imaging provides new functional and anatomical information that is potentially of great benefit in solving these problems. High resolution anatomical imaging, and diffusion weighted imaging will provide information about infiltration. Perfusion imaging (using both intrinsic arterial spin labelling contrast and also contrast agents to measure blood flow and blood volume), phase imaging, angiography and venography, and spectroscopic imaging will provide information that may be relevant to tumour grading. This project will require technical developments (particularly because of the considerable differences between tumours and normal tissues), coordinating patient studies, and image and data analysis.

Magnetoencephalography and its relationship to fMRI

Professor P. Morris and Dr S. Francis

We have developed a new approach, the GLM-beamformer method, for processing MEG data that enables changing patterns of activity to be mapped across all frequency ranges. We have used it to map the decrease in alpha band (8-13Hz) activity, the corresponding increase in gamma band (50-70Hz) activity and the sustained evoked field change, and shown that they all co-vary with the fMRI BOLD response in a simple visual paradigm. These neuromagnetic phenomena, which represent the major postsynaptic contributions to neuronal activity, are likely to be responsible for increased cerebral metabolism and the response observed in fMRI. We are now in a strong position to test this, and will do so in a series of studies in which the amplitude and duration of simple visual, somatosensory and auditory stimuli are varied. The MEG data will be compared with BOLD and more quantitative measures of brain activity in parallel fMRI studies at 3 and 7T. Methods will also be developed for mapping correlated activity measured by MEG and fMRI. Comparison between the correlation maps should reveal whether the correlation is directly related to activity or the result of correlations in other physiological parameters.

Combined Electroencephalography (EEG) and functional MRI (fMRI)

Professor Richard Bowtell and Dr Susan Francis

EEG provides valuable information about the timing of electrical activity in the brain, but it is difficult to work out from EEG data where in the brain the activity is occurring. fMRI allows detection of brain activity with excellent spatial resolution, but the temporal resolution is compromised by the slow nature of the changes in blood flow upon which it relies. The combination of EEG and fMRI data therefore allows the accurate spatial information provided by fMRI to be used in conjunction with the detailed information about the timing of electrical activity from EEG. However, the acquisition of EEG data in an MR scanner is technically difficult, because voltages that are many times larger than the brain signals are generated by pulsatile blood flow and the changing magnetic fields produced by the scanner. The periodicity of these unwanted voltages makes it possible largely to remove them from the EEG trace and we now have an EEG system which allows simultaneous EEG/fMRI to be carried out. The aim of this project would be to produce a better understanding of the artefacts that are caused by the periodic scanner and cardiac pulsatility effects, as well as the more complex effects of subject movement, and to then exploit this understanding in combined EEG and fMRI studies of brain function, including measurement of blood flow changes linked to the modulation of electrical brain rhythms.

Dynamic Nuclear Polarisation and Microscopic NMR imaging.

Dr Walter Köckenberger

This project involves participation in a collaboration between the Physics Department at St. Andrews University and the Sir Peter Mansfield Magnetic Resonance Centre. The project provides comprehensive training in NMR and ESR technology and has as a main objective the development of a novel instrument for experiments with hyperpolarized nuclear spin systems. Hyperpolarized spin systems will be generated via dynamic nuclear polarisation based on electron- nuclear spin interaction. The resulting dramatic enhancement of the NMR signal will make it possible to acquire highly resolved NMR images and spectroscopic information with high sensitivity from small biological samples.

Multinuclear Spectroscopy at 3 & 7T

Professor Peter Morris

13 C magnetic resonance spectroscopy (MRS) is being used to study brain metabolism. The incorporation into glutamate and glutamine of 13 C label, supplied as glucose, provides a quantitative measure of cerebral energy demand and the rate of neurotransmitter release, both of which can be related to regional brain activity. This project will involve the development of spectroscopic sequences at 7T to improve the spatial and temporal sensitivity of this exciting new functional MRS technique.

Similar techniques will also be developed at 3 & 7T to study the anomalies in the storage and metabolism of carbohydrate and lipid in diabetic subjects – an area of increasing concern as the incidence of this disease continues to rise in the western world.

In parallel, 31 P and 1 H MRS will be used to determine the levels and turnover of key metabolites in muscle, liver and brain.

Ultra-fast 2D Spectroscopy Applied To Human Brain Physiology

Dr Walter Köckenberger

This project involves the implementation of very fast spectroscopic pulse sequences on a whole body system to study brain metabolism. Such techniques will be useful to study exchange between metabolic pools and temporal variations of metabolic pool sizes. The project will be based on a collaboration with Prof Lucio Frydman's group at the Weizmann Institute in Israel . The main focus of the project will be on in vivo spectroscopy and the student will be provided with comprehensive training in techniques for NMR spectroscopy.

Development of Novel Insert Gradient Coils

Professor R Bowtell and Dr P Glover

Large switched magnetic field gradients and stroong shim fields are key to the generation of high quality images at 7T. Limitations on the achievable gradient strength and slew rate are set by the gradient coil resistance and inductance, as well as the need to avoid peripheral nerve stimulation and excessive acoustic noise. It is well known that a reduction in the size of the gradient coil leads to significant performance gains and recent work has shown that novel insert, head gradient coils potentially offer further improvements over conventional coils. This project will focus on the design, testing and exploitation of these novel coils on the high field system.

Whole body imaging

Professor P Gowland and Dr S Francis, Dr L Marciani and Dr C Hoad

MRI can provide a unique range of information about physiological function. We have used this with great success to study gastrointestinal function and fetal development. However whole body imaging poses particular problems compared to brain imaging, in particular the amount of RF power required to produce an image (particularly at high field- 3T) and also the problems of unpredictable motion in the abdomen. This project will involve developing imaging techniques to overcome these problems and to allow quantitative measurements of different aspects of physiology such as blood flow to the gut wall, dilution and mixing of food in the gastrointestinal tract and perfusion of the placenta or fetal brain.

Interaction of Changing Magnetic Fields with the Human Body

P Glover, R Bowtell

The switched magnetic field gradients that are used in MRI produce time-varying magnetic fields that induce electric fields and consequently current flow in the conducting tissues of the human body. When the gradient switching rate is very high, the induced currents can be large enough to cause peripheral nerve stimulation, felt as a twitch or “pins and needles”. M ovement around MR scanners also generates time varying magnetic fields that produce weak circulating currents in the human body, which have been linked to feelings of dizziness. Although it is straightforward to measure the rate of change of magnetic field experienced, measurement of the electric field, E, or current density, J, induced inside the body is not possible. This is a problem since occupational exposure limits are generally set in terms of E or J, and the lack of measurements has meant that a great deal of emphasis has been placed on numerical simulations. Recently, we have developed a system for measuring the induced electric fields at the surface of the body and this project would involve using this system to make measurements that can be used to feed into the debate on occupational exposure and to validate the results of numerical simulations.

Combined Transcranial Magnetic Stimulation (TMS) and functional Magnetic Resonance Imaging (fMRI)

Richard Bowtell, Tomas Paus (Brain and Body Centre)

In transcranial magnetic stimulation (TMS) focal areas of the cortex are stimulated by briefly passing a large current through a small coil positioned over the scalp. By using TMS to disrupt cortical activity it is possible to identify connectivity between brain areas and to probe the temporal evolution of activity in brain networks. The combination of TMS with fMRI allows the effects of the cortical stimulation to be mapped and additionally opens up new possibilities for understanding the mechanism of action of TMS, via quantitative measurement of the changes in blood flow and the concentration of metabolites that TMS elicits. Combining TMS and fMRI poses a number of technical challenges, relating to difficulties in carrying out MRI at the same time as passing large rapidly switched currents through the TMS coil and in accurate positioning of the TMS coil within the confines of an MR scanner. This project will build on initial studies of the effects of TMS on motor cortex that have been carried out at 3 T.

High Resolution Anatomical Imaging at 7 T

S Francis, P Gowland, R Bowtell

The increased MR signal strength at high field can be used to improve the resolution of images to a level where it is potentially possible to see anatomical detail at the sub-millimetre level. This opens up the exciting possibility of directly mapping functional areas of the brain by identifying changes in the pattern of myelination within the cortical grey matter. This project will focus on developing imaging sequences that allow the best detection of these subtle changes in myeloarchitecture, and on exploiting them in human brain studies at 7 T.