The intrinsic signal-to-noise ratio in human cardiac imaging at 1.5, 3, and 4 T

Cardiac imaging is inherently demanding on the signal-to-noise performance of the MR scanner and may benefit from high field strengths. However, the complex behavior of the radiofrequency field in the human body at high frequencies makes model-based analyses difficult. This study aims to obtain reliable comparisons of the signal-to-noise profile in the human chest in vivo at 1.5, 3, and 4 T. By using an RF-field-mapping method, it is shown that the intrinsic signal-to-noise increases with the field strength up to 4 T with a less than linear relation. The RF held profile is markedly distorted at 4 T, and the onset of this distortion is dependent on the body size. The high power deposition and the consequences of the RF field distortion are discussed. (C) 1997 Academic Press.