HIGH-SPEED DIFFUSION IMAGING IN THE PRESENCE OF EDDY CURRENTS

This paper describes two schemes for fast diffusion imaging on a 1.5-T MRI unit with unshielded gradients and 10-mT/m gradient system, The p repared longitudinal magnetization is sampled by a turbo fast low-angl e shot (FLASH) sequence. The first scheme involves modifications to a diffusion-weighted driven-equilibrium preparation sequence that yields quantitative diffusion imaging, The second scheme consists of four 90 degrees pulses that form the preparatory period with diffusion gradie nts applied between the first and last two 90 degrees pulses. Sufficie nt time is allowed between the diffusion gradients and the beginning o f the echo readout to allow eddy currents to decay to an acceptable le vel. Phantom studies show agreement between diffusion coefficients in the literature with those determined using the above schemes. The pote ntial application of these sequences in monitoring temperature is demo nstrated in phantoms. Artifact-free quantitative diffusion-weighted im ages of the brain using the second scheme are presented.