Assessment of regional lung ventilation in dog lungs with Gd-DTPA aerosol ventilation MR imaging.
OBJECTIVE
Gd-DTPA aerosol ventilation MR imaging was obtained using a modified aerosol delivery system with an aerosol reservoir to non-invasively assess regional lung ventilation in dogs.


METHODS
Seven anesthetized, spontaneously breathing normal dogs inhaled 200 mmol Gd/l Gd-DTPA aerosol produced by an ultrasonic nebulizer, using an open-circuit aerosol delivery system with or without an aerosol reservoir. Fast gradient-echo MR images were sequentially acquired with an interval time of 1 min for 25 min before and after aerosol inhalation. The aerosol study was also performed using the aerosol delivery system with an aerosol reservoir in the same 7 dogs after airway obstruction with a balloon catheter, and in another 7 dogs after pulmonary arterial embolization with enbucrilate. An i.v. Gd-DTPA-enhanced dynamic MR study after i.v. bolus injection of a 0.1 mmol/kg dose of Gd-DTPA was combined to assess regional lung perfusion. Lung enhancement effect was evaluated by time-signal intensity curves and the subtracted ventilation- and perfusion-weighted images.


RESULTS
With or without the aerosol reservoir, the normal dog lungs were gradually and gravity-dependently enhanced with time after aerosol inhalation. The use of the aerosol reservoir, however, showed significantly greater lung enhancement without a significant increase in breathing rate and with minimal reduction in PaO2 of less than 5 mm Hg in these animals. The enhancement effect of i.v. injection of Gd-DTPA at pulmonary arterial perfusion phase was significantly greater compared to that of Gd-DTPA aerosol throughout the normal lungs, and the subtracted ventilation-weighted and perfusion-weighted images showed homogeneous but gravity-dependent aerosol deposition and perfusion. These images clearly defined the regionally matched perfusion-ventilation deficits in the lung regions distal to bronchial obstruction in all the airway obstruction dogs, and the regionally mismatched perfusion-ventilation in the embolized regions of all the pulmonary arterial embolization animals.


CONCLUSIONS
Gd-based aerosol can non-invasively image regional lung ventilation in spontaneously breathing animals, using an adequate aerosol delivery system. The combined use of Gd-DTPA perfusion MR imaging may be acceptable for defining regionally impaired lung function associated with acute airway obstruction and pulmonary arterial embolization.
Suga
K
K
Department of Radiology, Yamaguchi University School of Medicine, Ube, Japan.
Ogasawara
N
N
Tsukuda
T
T
Matsunaga
N
N
D000336:Aerosols; D000818:Animals; D003287:Contrast Media; D004285:Dogs; D004659:Enbucrilate; D019786:Gadolinium DTPA / Q000008:administration & dosage; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D011655:Pulmonary Embolism / Q000139:chemically induced / Q000175:diagnosis; D012123:Pulmonary Ventilation; D014692:Ventilation-Perfusion Ratio
D000336:Aerosols; D003287:Contrast Media; D004659:Enbucrilate; D019786:Gadolinium DTPA