Signal intensities in FLASH-EPI-Hybrid sequences

Theoretical considerations on the signal-to-noise ratio (SNR) in FLASH-EPI- Hybrid imaging were published previously. The purpose of this work was to i nvestigate in vice the signal intensities in Hybrid images as a function of sequence specific parameters. In detail, the SNR as a function of the numb er of echoes m per RF excitation, the excitation flip angle alpha, and the dependence on the tissue relaxation times T1 and T2* were studied. In eight healthy subjects brain and abdominal Hybrid images were acquired where m a nd alpha were changed independently. Signal intensities in human brain, liv er, and kidney were evaluated for each Hybrid experiment. Additionally, T1 and T2* values of these tissue types were quantified to allow for a compari son with the theory. An excellent agreement between calculated and measured signal behavior was found. The theory was therefore validated in vivo and can thus be used to optimize the signal-to-noise in Hybrid experiments. (C) 1999 Academic Press.