A frameless stereotaxic MRI technique for macaque neuroscience studies

Area of Science:

• Neuroscience
• Medical Imaging
• Primate Research

Background:

• Magnetic Resonance Imaging (MRI) is crucial for preplanning non-human primate neuroscience procedures.
• Current methods rely on stereotaxic frames or fiducial markers for orienting MRI studies in stereotaxic space.
• A need exists for simpler, frameless stereotaxic alignment techniques.

Purpose of the Study:

• To present and evaluate a frameless MRI stereotaxic technique for non-human primates.
• To align MRI datasets to the Frankfurt stereotaxic baseline plane using bony landmarks.
• To eliminate the need for stereotaxic frames or external fiducials.

Main Methods:

• Developed a frameless MRI stereotaxic technique using bony landmarks (infraorbital margin, external auditory meatus) and supplementary imaging landmarks.
• Evaluated the technique in 8 rhesus macaques using 3D fast gradient echo MRI (0.7mm isotropic resolution).
• Compared stereotaxic coordinate accuracy against traditional stereotaxic frames and MRI-compatible frames.

Main Results:

• Mean localization difference for fiducial markers was 1.6 +/- 0.6 mm compared to a traditional frame.
• Localization of cerebral anatomy differed by 2.8 +/- 2.2 mm compared to an MRI-compatible frame, reduced to 0.5 +/- 0.6 mm after correcting for rotation.
• Electrode tract coordinates were highly accurate (0.5mm +/- 0.2 mm) relative to the microdrive.

Conclusions:

• The frameless MRI stereotaxic technique offers accurate surgical and neurophysiological planning in individual animals.
• It utilizes readily available software and eliminates the need for specialized MRI localization hardware.
• This method is amenable to functional MRI studies due to reduced anesthesia requirements and is applicable to other species.