Regional measurements of pulmonary edema by using magnetic resonance imaging

Athree-dimensional magnetic resonance imaging (MRI) method to measurepulmonary edema and lung microvascular barrier permeability wasdeveloped and compared with conventional methods in nine mongrel dogs.MRIs were obtained covering the entire lungs. Injury was induced byinjection of oleic acid (0.021-0.048 ml/kg) into a jugularcatheter. Imaging followed for 0.75-2 h. Extravascular lung waterand permeability-related parameters were measured from multiple-indicator dilution curves. Edema was measured as magnetic resonance signal-to-noise ratio (SNR). Postinjury wet-to-dry lung weight ratio was 5.30 ± 0.38 (n = 9). Extravascular lung water increased from 2.03 ± 1.11 to 3.00 ± 1.45 ml/g(n = 9, P < 0.01). Indicatordilution studies yielded parameters characterizing capillary exchangeof urea and butanediol: the product of the square root of equivalentdiffusivity of escape from the capillary and capillary surface area(D^1/2S)and the capillary permeability-surface area product(PS). The ratio ofD^1/2Sfor urea toD^1/2Sfor butanediol increased from 0.583 ± 0.027 to 0.852 ± 0.154 (n = 9, P < 0.05). Whole lung SNR atbaseline, before injury, correlated withD^1/2Sand PS ratios (both P < 0.02). By using rate of SNR change, the mismatch of transcapillaryfiltration flow and lymph clearance was estimated to be0.2-1.8 ml/min. The filtration coefficient was estimated fromthese values. Results indicate that pulmonary edema formation duringoleic acid injury can be imaged regionally and quantified globally, andthe results suggest possible regional quantification by usingthree-dimensional MRI.