Brain magnetic resonance imaging with contrast dependent on blood oxygenation.

TLDR

Paramagnetic deoxyhemoglobin in venous blood serves as a natural MRI contrast agent, and BOLD contrast adds an additional feature that complements PET‑like techniques for measuring regional neural activity. The study demonstrates that gradient‑echo techniques at high field can accentuate deoxyhemoglobin contrast to image brain microvasculature with contrast reflecting blood oxygen level. The method uses gradient‑echo BOLD contrast that follows blood oxygen changes induced by anesthetics, insulin‑induced hypoglycemia, and inhaled gas mixtures altering metabolic demand or blood flow. The results indicate that BOLD contrast can provide in vivo real‑time maps of brain blood oxygenation under normal physiological conditions.

Abstract

Paramagnetic deoxyhemoglobin in venous blood is a naturally occurring contrast agent for magnetic resonance imaging (MRI). By accentuating the effects of this agent through the use of gradient-echo techniques in high fields, we demonstrate in vivo images of brain microvasculature with image contrast reflecting the blood oxygen level. This blood oxygenation level-dependent (BOLD) contrast follows blood oxygen changes induced by anesthetics, by insulin-induced hypoglycemia, and by inhaled gas mixtures that alter metabolic demand or blood flow. The results suggest that BOLD contrast can be used to provide in vivo real-time maps of blood oxygenation in the brain under normal physiological conditions. BOLD contrast adds an additional feature to magnetic resonance imaging and complements other techniques that are attempting to provide positron emission tomography-like measurements related to regional neural activity.