This studentship is part of an EPSRC project working with GE Healthcare on optimising existing lung MRI methods and technology on existing clinical MRI scanners (1.5 T and 3 T) and establishing new methods and technology for low-field (0.5T) MRI scanners.
This studentship will focus on exploring the MR physics of contrast and signal to noise ratio and the design of efficient MRI acquisition strategies for imaging native and CE 1H, 129Xe and 19F at low-mid field strengths.
We will characterise 1H tissue relaxation properties at different fields and simulate CE r1 and r2 relaxivity for contrast doses ≤ those used at high field. Conventional paramagnetic contrast media work on the principle of shortening T1 relaxation times. The vast majority of clinical CE MRI is performed with gadolinium (Gd)-chelated contrast media for which r1 > r2 at clinical field strengths of 1.5T and 3T. However, r1 decreases with increasing field strength and at high field r2 effects become more significant. Conversely, at lower field (0.5T; the field strength of the prototype MR system installed under the EPSRC prosperity partnership) r1 is higher and MR pulse sequences will have to be re-optimised.
There is active research into contrast media containing other metals than Gd, for instance, Fe-based nanoparticles or Mn-based chelates. Such contrast media have very different r1 and r2 characteristics and may have advantages or disadvantages for low-field MRI, which this PhD project is seeking to understand via theory, simulations and non-clinical measurements.
129Xe hyperpolarisation is B0-independent, but transverse relaxation times are B0 dependent; we will characterise these properties at 0.5T.
We will study chemical exchange behaviour between 129Xe gas and dissolved-phase compartments at 0.5T vs. 1.5T/3T, via measurement and simulation.
We will also explore the relaxation properties of 19F in perfluorinated gases at 0.5T.
Pulse sequence design
Based on this understanding of relaxation physics we will design and implement acquisition strategies for low field MRI : using our SSFP and diffusion weighted simulation frameworks. We will assess implications for a range of standard CE MR imaging protocols. However, one area of focus will be to adapt and optimise 1H MR pulse sequences for low-field 1H lung MR.
HP media do not suffer from SNR deficits at low field, and therefore SSFP approaches for 129Xe ventilation imaging should be transferable to 0.5T.
For 129Xe dissolved-phase imaging of gas exchange at 0.5T, we will develop spectroscopic imaging to counteract the low frequency separation of 129Xe NMR peaks.
19F MRI at high-field is constrained by SAR and short relaxation times; We will simulate high flip angle SSFP ventilation imaging and diffusion-weighted imaging of lung microstructure with 19F at 0.5T.
Proposed start date: 1st March 2024
Candidates must have a first or upper second class honours degree in Physics or Electrical Engineering or a related subject or significant research experience.
How to apply:
Please complete a University Postgraduate Research Application form available here: www.shef.ac.uk/postgraduate/research/apply
Please clearly state the prospective main supervisor in the respective box and select School of Medicine and Population Health: Infection, Immunity and Cardiovascular Disease as the department.
Interested candidates should in the first instance contact Prof Jim Wild: [Email Address Removed]