Dynamic 3He imaging for quantification of regional lung ventilation parameters.

Dynamic ventilation imaging using laser-polarized (3)He has a promising potential for elucidating the physiology and physiopathology of the lungs. In this study, a methodological approach is proposed for the assessment and quantification of local ventilation parameters. High-temporal-resolution coronal ventilation image series were obtained with a projection-reconstruction (PR) sequence combined with the sliding-window technique. After image series were processed, parametric pixel-by-pixel maps of the gas arrival time, filling time constant, inflation rate, and gas volume were generated. The acquisition technique and the signal processing procedure, which are referred to collectively as sliding pulmonary imaging for respiratory overview (SPIRO), were tested in vivo in healthy rat lungs using a contrast media injector for controlled (3)He flow and volume injection in the animal lungs. The same protocol was applied to broncho-constriction animal models using intravenous injection of methacholine solution. Inflation rate values measured in the lungs were found to decrease with increasing doses of injected methacholine solution. This study demonstrates that it is possible to obtain quantitative regional gas dynamic information using the SPIRO technique in a single polarized gas inspiration.