Clinical applications of Fast Field-Cycling MRI
Fast Field-Cycling MRI (FFC MRI) is a promising imaging technique that has the ability to combine high contrast and good image resolution, two key components of MRI that are notoriously famous for being incompatible, without the need of a contrast agent. This unique ability, combined with the low risk associated to the low magnetic fields used and the low scanning cost, makes this imaging platform a good candidate for patient screening.
Detection of osteoarthritis using the quadrupolar signal
Osteoarthritis (OA) is the most prevalent joint disorder and cause of disability in the United Kingdom with an estimated 8.5 million persons suffering from joint pain due to OA, and it is a major cause of disability in the world. Multiple risk factors appear to be involved in the onset and progression of OA, including age, genetics, gender, overuse, trauma and obesity, even though none of these have been identified as a clear cause of the disease. There are currently no pharmacological interventions available to patients for modifying the underlying disease but early patient management can help to slow down its progression. it is therefore crutial to detect OA before irreversible damages develop.
The underlying pathophysiology of OA has been extensively studied and recent research identifying the importance of matrix-degrading enzymes, chondrocyte hypertrophy and apoptosis, subchondral bone metabolism, cytokines and inflammation has identified a number of potential targets for disease modifying agents. Interest in developing potential therapeutic agents has highlighted the need for biomarkers of disease progression with imaging biomarkers currently appearing to offer the best prospect.
A previous study of FFC MRI on excised samples of OA cartilage from hip replacement showed promising results: it appeared that this technique can offer degradation-sensitive contrast using a particular signal, the quadrupolar signal. A more extensive study is being undertaken at the moment in collaboration with Mr G.P. Ashcroft and Prof R. Aspden in order to assess this technique.
Characterisation of fibrin clots and applications to thrombosis
Fibrin is one of the main constituents of blood clots. It is derived from fibrinogen, a long, narrow and heavy protein (340 kDa), under the action of thrombin.
Fibrin protein are insoluble and aggregate into long filaments that can cross-link to form a rigid gel structure. The size and diameter of these filaments, together with the amount of cross-linking, can be controled more or less independantly during the clotting process by several paremeters such as the concentration of calcium ions or the content of factor XIII and RS283 proteins.
The rigidity of the clot is an important parameter for the treatment of deep vein thrombosis (DVT), a pathology that may develop in several diseases or conditions such as cast ankle, high saturated fat diet or drug abuse. DVT is treated by thrombolysis when the conditions allow, but response to treatment varies greatly due to the nature of the clot.
FFC NMR studies of fibrin clots have showed that field-cycling can detect fibrin quantitatively, with possible applications to DVT characterisation. A study has been initiated on DVT patients in parternship with the NHS at the Aberdeen Royal Infirmary to assess whether FFC MRI can predict the response to thrombolitic treatment.
An in-vitro study of fibrin systems is also being developed in partnership with Dr N. Mutch and Dr C. Whyte that aims to detect differences in clot structure due to the effect of polyphosphate chains during the clot.
Detection of tumours at low magnetic fields
one of the parameters of interest that is measured by an MRI scan is the transverse relaxation time of spins, also called T1. This parameteris known to vary greatly between tissues at low magnetic field (typically below 0.05T) but much less at high fields. This is part of the reason why contrast agents are needed for tumour detection on conventional MRI clinical scanners.
Unfortunately, low magnetic fields also come with low image resolution and long scan time. This is the reason why MRI scanners are operating at ever increasing fields.
FFC offers a compromise between high contrast and high resolution that cannot be reached by conventional fixed-field MRI scanners. This opens new avenues for contrast-based studies with potential applications in many fields of medicine.
One particular area of interest is breast cancer: breast tumours are commonly detected by analysis of contrast in MRI scans but may be difficult to assess if their extent is restricted to a few millimeters. A study has been initiated by Dr Lionel Broche in collaboration with Prof S. Heys, Dr I. Miller, Dr T. Gagliardi, Mr G.P. Ashcroft, Dr D. Boddie and Dr S. Dundas to assess FFC MRI in the context of breast cancer.
Detection of Alzheimer disease using FFC MRI
Alzheimer Disease (AD) is a neurodegenerative disease that affects over 750,000 patients in the UK. It is the most common form of dementia and has devastating effect on the patient and their relatives. The mechanisms of progression of AD are still poorly understood but this disease is associated with the formation of protein tangles in the brain.
FFC MRI demonstrated good ability in the detection of low-mobility proteins so it is a good candidate to obtain tangle-dependant contrast in images. We are currently planning a series of large studies on this topic.
Theoretical developments for FFC MRI pulse sequence and data processing
In addition to clinical projects, Dr Lionel Broche is developing data processing methods tailored to FFC MRI to decrease the scan time and improve data quality.