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Rapid measurement of Gd‐DTPA extraction fraction in a dialysis system using echo‐planar imaging
Author(s) -
Niendorf Eric R.,
Grist Thomas M.,
Frayne Richard,
Brazy Peter C.,
Santyr Giles E.
Publication year - 1997
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.598104
Subject(s) - spins , nuclear magnetic resonance , relaxation (psychology) , nuclear medicine , echo planar imaging , t2 relaxation , filter (signal processing) , pulse sequence , chemistry , analytical chemistry (journal) , biomedical engineering , physics , computer science , magnetic resonance imaging , chromatography , medicine , computer vision , radiology , condensed matter physics
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 1measurement 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 1relaxation recovery. Data acquisition and post‐processing techniques were developed to extend the accuracy of the LL technique to systems with slow flow which did not provide complete refreshment of spins between samples of the T 1recovery. A multi‐shot EPI LL interleaved acquisition of relaxation recovery space (IRRS) provided T 1measurement 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 1fit allowed accurate T 1estimation ( ± 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 .