Table 1.

Summary of inhalation and breath-hold approaches

	Breath Hold	Free Breathing/Gated
CT
Inspiration/expiration	√	No
Xe CT	√	Gated to controlled or trained breathing
Dual energy Xe CT	Fixed volume inhalation for single breath method	Gated to controlled or trained breathing
Dynamic (4DCT)	No	Tidal breathing
MRI
Hyperpolarized Xe/He	Fixed volume dose from FRC or RV	Inhalation and exhalation dynamic possible
O2-enhanced 1H	No	Tidal breathing
1H-UTE	Fixed volume inhalation from FRC or RV	No
4D (FD) 1H	No	Tidal breathing

CT, computed tomography; UTE, ultrashort echo time; FD, Fourier decomposition.