Rapid measurement of Gd-DTPA extraction fraction in a dialysis system using echo-planar imaging

Gd-DTPA (Magnevist, Berlex, Wayne, NJ) extraction fractions (EF) have been measured for three dialysis filter types using an echo-planar imaging (EPI) Look-Locker T-1 measurement technique under conditions of fast and slow flow. The mean EF measured in Fresenius (Bad Homburg, Germany) F3, F6, and F8 dialysis filters were 0.015+/-0.005, 0.053+/-0.004, and 0.084+/-0.003, respectively, under conditions of fast flow which provided complete refreshment of spins in the intervals between read-out pulse samples of the T-1 relaxation recovery. Data acquisition and post processing techniques were developed to extend the accuracy of the LL technique to systems with slow how which did not provide complete refreshment of spins between samples of the T-1 recovery. A multi-shot EPI LL interleaved acquisition of relaxation recovery space (IRRS) provided T-1 measurement accuracy comparable to the refreshed system, +/- 10, but at the expense of increased scan times (factor of 2 or 3). Discarding the first few non-equilibrium relaxation recovery samples from the T-1 fit allowed accurate T-1 estimation (+/-10) with a single-shot EPI LL method under conditions of slow flow. These EPI LL EF measurement methods may provide useful techniques for evaluating renal function in vivo. (C) 1997 American Association of Physicists in Medicine.