Pulmonary perfusion: respiratory-triggered three-dimensional MR imaging with arterial spin tagging--preliminary results in healthy volunteers. 
The authors used a spin-tagging method of magnetic resonance perfusion imaging to measure pulmonary perfusion in eight healthy volunteers with use of a respiratory-triggered three-dimensional pulse sequence.  The average signal intensity (SI) decrease upon arterial labeling was 24%.  The perfusion SI increased by 21% after exercise (P = .02).  Focal blood flow abnormalities were observed in a patient with chronic obstructive pulmonary disease.