In vivo diffusion tensor imaging of the human optic nerve: pilot study in normal controls

Area of Science:

• Neuroimaging
• Medical Physics
• Radiology

Background:

• Diffusion Tensor Imaging (DTI) is crucial for assessing white matter integrity.
• Optic nerve (ON) imaging presents challenges due to susceptibility artifacts and motion sensitivity.
• Previous DTI methods struggled with artifact reduction and signal clarity in the ON.

Purpose of the Study:

• To evaluate the efficacy of zonally oblique multislice (ZOOM) DTI for optic nerve imaging.
• To establish baseline DTI metrics (FA, MD) in healthy optic nerves.
• To demonstrate the feasibility of reducing motion and susceptibility artifacts in ON DTI.

Main Methods:

• Acquisition of DTI data in 10 healthy controls using ZOOM DTI.
• ZOOM DTI utilizes a small field of view (FOV) and a fast sequence with a shortened EPI echo train.
• Measurements of fractional anisotropy (FA) and mean diffusivity (MD) were performed on coronal sections of the optic nerves.

Main Results:

• Average FA values for the right and left optic nerves were 0.64 ± 0.09 and 0.57 ± 0.10, respectively.
• Average MD values for the right and left optic nerves were (1173 ± 227) x 10⁻⁶ mm²/s and (1266 ± 170) x 10⁻⁶ mm²/s, respectively.
• Eigenvalue measurements confirmed the expected directional structural organization of the optic nerve.

Conclusions:

• ZOOM DTI is a viable technique for imaging the optic nerve with reduced artifacts.
• The study provides normative FA and MD values for healthy optic nerves.
• This method holds promise for future clinical applications in optic nerve disorders.