Artifacts in functional magnetic resonance imaging from gaseous oxygen

Area of Science:

• Neuroimaging
• Biophysics
• Medical Physics

Background:

• Functional magnetic resonance imaging (fMRI) relies on detecting subtle signal changes related to neural activity.
• Gaseous oxygen is paramagnetic and can interact with magnetic fields, potentially affecting MRI signal intensity.

Purpose of the Study:

• To investigate whether intermittent administration of pure oxygen causes signal intensity fluctuations in MRI.
• To determine if these fluctuations are related to paramagnetic oxygen concentrations.
• To assess the impact of these fluctuations on fMRI data quality.

Main Methods:

• Acquisition of echo planar gradient echo images of a phantom during intermittent pure oxygen administration.
• Comparison with controls: intermittent room air administration and continuous oxygen administration.
• Analysis of signal intensity changes and their temporal correlation with oxygen delivery.

Main Results:

• Unexpectedly large signal intensity fluctuations (up to 60%) were observed, temporally correlated with oxygen administration.
• These signal changes produced artifacts in functional images, particularly at interfaces within the phantom.
• Control conditions (room air or continuous oxygen) did not produce similar artifacts.

Conclusions:

• Intermittent pure oxygen administration during fMRI data acquisition can induce significant signal intensity changes.
• These oxygen-induced signal changes can lead to artifacts that may be misinterpreted as neural activity or obscure true findings.
• Careful consideration of oxygen delivery protocols is necessary to avoid confounding fMRI results.