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Abstract #3482

Negative Contrast Enhancement in T2*-Weighted Images of the Human Brain During Hyperoxia

David Thomas Pilkinton1, Santosh Gaddam1, Mark A. Elliott1, Ravinder Reddy1

1Center for Magnetic Resonance and Optical Imaging, University of Pennsylvania, Philadelphia, PA, United States

Hyperoxia is known to provide positive contrast enhancement (CE) on T2*-weighted images based on the BOLD effect. We have shown here that hyperoxic contrast, despite producing positive CE across most of the brain, generates significant negative CE in T2*-weighted images in inferior regions of the brain located near large arteries, even at lower FiO2 levels (<0.6). We believe this effect is due to the shortening of T2* in arterial blood from excess paramagnetic molecular oxygen dissolved in the plasma. Hyperoxic contrast on T2*-weighted images may therefore produce negative or positive CE depending on the characteristics of the local blood volume.