Rapid and efficient mapping of regional ventilation in the rat lung using hyperpolarized 3 He with Flip angle variation for offset of RF and relaxation (FAVOR)

A novel imaging method is presented, Flip Angle Variation for Offset of RF and Relaxation (FAVOR), for rapid and efficient measurement of rat lung ventilation using hyperpolarized helium‐3 ( 3 He) gas. The FAVOR technique utilizes variable flip angles to remove the cumulative effect of RF pulses and T 1 relaxation on the hyperpolarized gas signal and thereby eliminates the need for intervening air wash‐out breaths and multiple cycles of 3 He wash‐in breaths before each image. The former allows an improvement in speed (by a factor of ≈30) while the latter reduces the cost of each measurement (by a factor of ≈5). The FAVOR and conventional ventilation methods were performed on six healthy male Brown Norway rats (190–270 g). Lobar measurements of ventilation, r , obtained with the FAVOR method were not significantly different from those obtained with the conventional method for the right middle and caudal and left lobes ( P > 0.05 by a Wilcoxon matched pairs test). A methacholine challenge test was also administered to an animal and reduction and recovery of r was detected by the FAVOR method. The reduced 3 He consumption and the improvement in speed provided by FAVOR suggest that it may allow measurement of ventilation in human subjects not previously possible. Magn Reson Med 59:1304–1310, 2008. © 2008 Wiley‐Liss, Inc.