Bjrn Lampinen1,
Filip Szczepankiewicz1, Danielle van Westen2, Pia
Sundgren2, Freddy Sthlberg1, 2, Jimmy Ltt3,
Markus Nilsson4
1Department
of Medical Radiation Physics, Lund University, Lund, Sweden; 2Department
of Diagnostic Radiology, Lund University, Lund, Sweden; 3Center
for Medical Imaging and Physiology, Lund University Hospital, Lund, Sweden; 4Lund
University Bioimaging Center, Lund University, Lund, Sweden
Filter-exchange imaging (FEXI) is based on a double pulsed field gradient (d-PFG) sequence, and provides a fast, non-invasive method for mapping water exchange expressed in its parameter apparent exchange rate (AXR). We used an analytical technique based on the Cramer-Rao Lower Bound to optimize the acquisition protocol. A new protocol is presented which reduces the coefficient of variance (CV) by 30% for measured AXR. With this optimized protocol, comparative studies searching for alterations in the AXR of magnitude three times larger than the inter-subject standard deviation can be performed using as few as four individuals per group with scan time below 15 minutes. This will enable future investigations of AXR as a biomarker for disease and treatment effects.