Dynamic echo planar MR imaging of lung ventilation with hyperpolarized He-3 in normal subjects and patients with severe emphysema

We applied the rapid imaging capability of echo planar MR pulse sequences a nd hyperpolarized He-3 ventilation imaging to observe the dynamic distribut ion of gas in the lungs during breathing. Findings in five normal volunteer s (age 19-53 years) and four patients with severe smoking-related emphysema (age 56-71 years) were compared. All studies were performed on a 1.5 T who le body scanner using a 30 cm Helmholtz surface coil and 0.51 of 20-40% pol arized He-3 mixed with 1-21 nitrogen. Our echo planar imaging pulse sequenc e allowed acquisition of each image in 0.04 s, with a pixel size of 7 mm(2) (TR = 40.5 ms, TE = 12.1 ms, flip angle = 22 degrees, echo train length = 32, matrix = 32 x 64, held of view = 225 x 450 mm, slice thickness = 10 mm) . Imaging was performed in the transaxial plane repeatedly at 3, 10 or 20 e venly spaced levels, immediately before and during breathing of the gas mix ture. In normal subjects during the first breath, He-3 appeared throughout each slice first in the mid lungs, then in the lower lungs, then in the upp er lungs, with slightly greater signal in the dependent posterior regions. In patients with emphysema, sequential filling of different lung regions wa s seen during the first breath, with delayed filling of other regions obser ved during rebreathing and room air washout. We conclude that subsecond dyn amic 3He MR ventilation imaging can reveal normal and abnormal ventilation phenomena not seen with conventional scintigraphic methods, and offers anot her approach to the study of ventilation physiology and pathophysiology. Co pyright (C) 2000 John Wiley & Sons, Ltd.