Image Registration for Quantitative Analysis of 3He MRI of the Mouse Lung

INTRODUCTION: He MRI is increasingly useful for regionally evaluating ventilation in mouse models of asthma before and after challenge with Methacholine (MCh) [1,2] Such changes can be effectively quantified by suitably normalizing the preand post-MCh images, and subtracting the two to generate a difference map depicting regional changes in ventilation[3]. However, difference mapping can in some instances be confounded by even sub-millimeter changes in the animal’s position between the two images. This problem can be addressed by registering the two He images to a common coordinate space without obscuring arising ventilation defects. Here we describe our approach to this problem, which now facilitates analyzing MCh-induced ventilation changes even in the presence of positional shifts.