Anatomical and functional MR imaging in the macaque monkey using a vertical large-bore 7 Tesla setup

Area of Science:

• Neuroscience
• Biomedical Imaging
• Systems Neuroscience

Background:

• Functional magnetic resonance imaging (fMRI) in nonhuman primates bridges human brain research and animal systems neuroscience.
• High-field MRI offers increased sensitivity and spatial resolution for detailed brain analysis.

Purpose of the Study:

• To present a novel 7 Tesla (T) vertical MR system optimized for macaque monkey neuroscientific research.
• To evaluate the system's capability for high-resolution anatomical and functional neuroimaging.

Main Methods:

• Utilized a 7 T/60 cm, 300 MHz vertical MR system for macaque monkeys.
• Performed anatomical MRI with voxel sizes down to 75x150x300 µm³.
• Measured T1, T2, and T2* relaxation times at 7 T and 4.7 T.
• Acquired blood-oxygen-level-dependent (BOLD) signals and cerebral blood flow (CBF) images.

Main Results:

• Achieved high-contrast anatomical imaging, visualizing neocortical lamination (e.g., Baillarger lines).
• Recorded distinct T1, T2, and T2* relaxation times at different field strengths.
• Detected robust BOLD signal changes (4.1% activation, -2.4% deactivation).
• Obtained high-resolution CBF images showing up to 38% flow increase in V1 during activation.
• Demonstrated superior spatial specificity of CBF maps compared to BOLD maps.

Conclusions:

• The novel 7 T MR system provides unprecedented sensitivity and resolution for primate neuroimaging.
• High-resolution CBF imaging offers enhanced spatial specificity, localizing functional activity within gray matter.
• This technology promises deeper insights into the physiological underpinnings of hemodynamic signals in the brain.