Insights in the rat brain by high resolution BOLD functional MRI

BioSpec 117/16 USR

Courtesy

Jörg U. Seehafer^1,2 and Mathias Hoehn¹,
¹In-vivo-NMR Lab, MPI for Neurological Research,
²medres - medical research GmbH, Cologne, Germany
Data acquired on a 11.7 Tesla BioSpec^® 117/16 USR system.

Functional MRI (fMRI) at a high spatial resolution of 75x75x1000 μm³ can be achieved using high field small animal MR scanners and four-element array coils. Fine, detailed sub-structures within the activation area can be detected at unrivaled in vivo resolution, thus broadening the understanding of the biophysical principles and origin of BOLD to gain further insight into brain organization and structure. Furthermore, functional brain deficit and recovery after brain diseases like stroke can be investigated in great detail.

: BOLD activation at 11.7 Tesla using the quadrature surface coil with a resolution of (left) 300x300x2000 μm³ for high quality and (right) 150x200x2000 μm³ for high sensitivity.

Functional MRI (fMRI) is a unique tool to study brain activation in humans and animals. In addition to standard anatomical MRI, fMRI can provide information about function and intactness of different brain regions as well as neuronal pathways and workflow of information between such regions.

Recent technologies in MRI such as high magnetic field strengths of up to 11.7T, fast RF-readout electronics and multi-element array coils enable high resolution functional MRI to detect and differentiate small activation volumes at the scale of even sub-structures.

These results provide new insights into the understanding of (i) the BOLD effect, (ii) different aspects such as animal models, anesthesia protocols, stimulation and imaging parameters as well as analysis techniques, (iii) the (changing) structure of the brain, (iv) reorganization and recovery of the brain after diseases like stroke and Alzheimer’s disease.

: High resolution BOLD activation at 11.7 Tesla using the four-element array coil with a resolution of 75x75x1000 μm³ for detection of (left) sub-structures within S1, and activation within other regions along the neuronal pathway: S2 and thalamus.

Increasing field strength provides higher S/N which, when invested into higher spatial resolution, provides not only access to finer details of sub-structures but also increases the BOLD amplitude (because of less “dilution” by partial volume effect).