Signal-to-noise ratio for hyperpolarized 3He MR imaging of human lungs: A 1.5 T and 3 T comparison

Abstract

The signal-to-noise ratio in hyperpolarized noble gas MR imaging is expected to be independent of field strength at frequencies typical of clinical systems (e.g., 1.5 T), where body noise dominates over coil noise. Furthermore, at higher fields (e.g., 3 T), the SNR of lung images may decline due to decreases in T2* originating from increases in susceptibility-induced field gradients at the air-tissue interface. In this work, the SNR of hyperpolarized 3He lung imaging at two commonly used clinical field strengths (1.5 T and 3 T) were compared in the same volunteers. Thermally polarized and hyperpolarized 3He phantoms were used to account for differences in MR imaging system and 3He polarizer performance, respectively, at the two field strengths. After correcting for T2* values measured at 1.5 T (16 ± 2 ms) and 3 T (7 ± 1 ms), no significant difference in image SNR between the two field strengths was observed, consistent with theory. Copyright © 2011 Wiley Periodicals, Inc.