REGIONAL MEASUREMENTS OF PULMONARY-EDEMA BY USING MAGNETIC-RESONANCE-IMAGING

A three-dimensional magnetic resonance imaging (MRI) method to measure pulmonary edema and lung microvascular barrier permeability was devel oped and compared with conventional methods in nine mongrel dogs. MRIs were obtained covering the entire lungs. Injury was induced by inject ion of oleic acid (0.021-0.048 ml/kg) into a jugular catheter. Imaging followed for 0.75-2 h. Extravascular lung water and permeability-rela ted 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). Ext ravascular lung water increased from 2.03 +/- 1.11 to 3.00 +/- 1.45 ml /g (n = 9, P < 0.01). Indicator dilution studies yielded parameters ch aracterizing capillary exchange of urea and butanediol: the product of the square root of equivalent diffusivity of escape from the capillar y and capillary surface area ((DS)-S-1/2) and the capillary permeabili ty-surface area product (PS). The ratio of (DS)-S-1/2 for urea to (DS) -S-1/2 for butanediol increased from 0.583 +/- 0.027 to 0.852 +/- 0.15 4 (n = 9, P < 0.05). Whole lung SNR at baseline, before injury, correl ated with (DS)-S-1/2 and PS ratios (both P < 0.02). By using rate of S NR change, the mismatch of transcapillary filtration flow and lymph cl earance was estimated to be 0.2-1.8 ml/min. The filtration coefficient was estimated from these values. Results indicate that pulmonary edem a formation during oleic acid injury can be imaged regionally and quan tified globally, and the results suggest possible regional quantificat ion by using three-dimensional MRI.