Research tools and methods: MRI protocol to investigate brain health
23 Feb 2016
Professor Klaus Ebmeier at the University of Oxford put together a magnetic resonance imaging (MRI) protocol for the Whitehall II study in 2012 allowing him to collect information about brain shrinkage, white matter integrity, blood flow and brain networks. He has related this information to detailed health outcomes and neuropsychological tests.
Combining long-term information from 800 people collected through the Whitehall II study with the MRI data will enable him and colleagues to examine the connection between risk and protective factors and brain changes. The Whitehall II study is the second part of the Whitehall cohorts, established at University College London (UCL) in 1985 to examine the links between social circumstances and health. By September 2011 the study of more than 10,000 civil servants had accumulated 25 years of social, behavioural and biological data, making it a unique study of ageing. Of the original group, more than 6,000 continued on to Phase II, which has concentrated on life course factors affecting health and personal functioning in later life.
During the 20th Century, the average life expectancy for people in the developed world increased dramatically, from around 50 to more than 75 years of age. This was due to various factors, including improvements in public health, nutrition and medicine. An MRC-funded study published in 2015 predicted the average life expectancy for male babies born in 2030 to be 85.7 years and for females 87.6 years. In comparison, the average life-expectancy for male babies born in 2012 is 79.5 years and females 83.3 years.
However, the risk of developing certain diseases rises exponentially as a person ages, putting increased pressure on medical and social care costs and resources. For example, dementia affects one in 20 people over 65 and one in six people over 80. The proportion of people with dementia doubles for every five-year age group. And according to some estimates, the number of people with neurodegenerative diseases will quadruple in the next 20 years.
A better understanding of the mechanisms of neurodegenerative diseases and the factors associated with protection against age-related dysfunction is essential in developing the means for prevention and treatment.
The MRI examination consists of various advanced MRI techniques that can assess the volume of grey and white matter from different brain structures. Reduced grey matter — structural tissue that processes information — and white matter — containing nerve fibres that transmit signals from one area of the brain to another — have been associated with future disease and age-related cognitive dysfunction. It also includes Diffusion Tensor MRI, which measures the degree to which the random motion of water molecules is restricted in the brain’s white matter in the direction of the nerve fibres. This reflects the quality of white matter fibre connections. It further includes a technique called BOLD fMRI that acquires brain activity images over 10 minutes. This enables the reconstruction of functional brain networks that are active in unison, even ‘at rest’. Finally, various MRI sequences (such as FLAIR and T2*) are able to detect abnormal tissue in the brain and ‘microbleeds’.
The Whitehall imaging protocol and data have been used to refine studies developed within the Oxford Functional MRI of the Brain (FMRIB) Analysis Group, for example, UK Biobank and the Connectome project, a five-year effort to characterise brain connectivity and function and their variability in healthy adults.
Whitehall. Image credit: George Evans, CC BY-SA 2.0 http://creativecommons.org/licenses/by-sa/2.0, via Wikimedia Commons.
Project reference number: MR/J004022/1