Ultrashort echo-time (UTE) functional lung imaging for fractional ventilation quantification: breath-hold vs. free-breathing

Motivation: Ultrashort echo-time (UTE) technique has recently gained attention in functional lung imaging for deriving quantitative maps including fractional ventilation (FV). Breath-hold UTE method can be easily utilized in clinical practice. However, failures in maintaining breath-hold often occur in clinical settings. Goal(s): To propose a free-breathing UTE method based on respiratory gating and compare its performance with breath-hold UTE method. Approach: Both breath-hold and free-breathing UTE methods were performed in two healthy volunteers to calculate FV maps for comparison. Results: Breath-hold UTE method produced FV maps with low contrast in both subjects, while free-breathing UTE method obtained FV maps with good contrast. Impact: The proposed free-breathing UTE method is straightforward to implement in clinical practice, and can provide satisfactory quantitative FV maps in subjects who fail to maintain breath-hold, improving the success rate of clinical UTE functional lung imaging.