Thursday April 10 2008
CEA
Precision measurements of brain activity by MRI, at 200 ms and in 3D: it can be done!
J Magn Reson Imaging. 27(4):744-53
CEA
Faster MRI image acquisition
As early on as 1977, Sir Peter Mansfield, Noble Laureate in Medicine for his discoveries concerning MRI, stated that it was feasible to take just 200 to 300 milliseconds to localise the MRI signal source in 3D in a volume of just a few cubic centimetres. However, the practical reality could not be demonstrated with the electronic and computing capabilities around at the time, and it was only 25 years later that this acquisition method baptized echo-volumar imaging (EVI) produced the first snapshot MRI images of the brain.
In 2004, a team from the Frédéric Joliot Hospital Service (SHFJ) applied the idea by combining the principle underpinning EVI with recent innovations in signal emission and reception. After three years of committed research on the SHFJ’s 1.5-T MRI imager system, they were able to obtain vastly improved image quality. The aim now is to compare the two methods and demonstrate the advantages offered for neuroscience research.
Statistical analysis tools at both the SHFJ and NeuroSpin have been adapted to EVI data, making it possible to reconstruct images of in-brain dynamics with ten times greater detail.
The methods have proven highly valuable to neuroscience research, particularly within the protocol framework for studies into language and ‘habituation’ (where brain responses to repeated stimuli – in this case, phrase – are less intense). This kind of study involves placing volunteers in the MRI imager while they wear headphones. A phrase is repeated four times at regularly-spaced intervals, and ‘echo-volumar’ images are acquired every 200 ms. The objective? To identify whether brain responses are stronger when hearing the first phrase than the following phrases.
The team will now focus on identifying the applications where EVI can be advantageously exploited. A clear candidate is functional imaging in infants, since the 200 ms acquisition time in 3D volumes can significantly reduce movement-related problems. Another important task is to develop new statistical analysis tools able to exploit the precision of the EVI signal, and adapt the data acquisition software to NeuroSpin’s 3-T and 7-T MRI systems. Looks like plenty of work on hand!