Physiological noise in oxygenation‐sensitive magnetic resonance imaging

TLDR

The study used oxygenation‑sensitive dual‑echo spiral MRI at 3.0 T on six healthy volunteers to characterize physiological noise arising from metabolic‑linked fluctuations and brain pulsations, showing it depends on signal strength and echo time unlike system or thermal noise. By varying flip angle and echo time, the authors separated noise components and found physiological noise at 3.0 T dominates other sources, is stronger in cortical gray matter than white matter, and that SNR saturates at higher fields, indicating such noise could probe functional information. Magn Reson Med 46:631–637, 2001; © 2001 Wiley‑Liss, Inc.

Abstract

Abstract The physiological noise in the resting brain, which arises from fluctuations in metabolic‐linked brain physiology and subtle brain pulsations, was investigated in six healthy volunteers using oxygenation‐sensitive dual‐echo spiral MRI at 3.0 T. In contrast to the system and thermal noise, the physiological noise demonstrates a signal strength dependency and, unique to the metabolic‐linked noise, an echo‐time dependency. Variations of the MR signal strength by changing the flip angle and echo time allowed separation of the different noise components and revealed that the physiological noise at 3.0 T (1) exceeds other noise sources and (2) is significantly greater in cortical gray matter than in white matter regions. The SNR in oxygenation‐sensitive MRI is predicted to saturate at higher fields, suggesting that noise measurements of the resting brain at 3.0 T and higher may provide a sensitive probe of functional information. Magn Reson Med 46:631–637, 2001. © 2001 Wiley‐Liss, Inc.