EFFECTS OF ENDOTOXIN LUNG INJURY ON NMR T-2 RELAXATION

The effects of endotoxin injury on lung NMR relaxation times (T-1,, CP MG T-2,, and Hahn decay constant (Hahn T-2)) were studied in excised u nperfused rat lungs, Blinded histologic examination showed no clear-cu t separation between endotoxin and control lungs. Morphometric lung ti ssue volume density and gravimetric lung water content did not differ significantly between the two groups. In contrast, the values of the f ast, intermediate, and slow T-2,components, obtained by multiexponenti al analysis of the CPMG decay curve, increased markedly after endotoxi n administration, with minimal overlap between endotoxin and control v alues, The response of Hahn T-2, was, in general, in the same directio n as that of CPMG T-2,; however, Hahn T-2 ,may be more affected by mea surement errors and may be less sensitive to the presence of lung inju ry. T-1, showed minimal changes after injury, The present data suggest that CPMG T-2 ,measurements can consistently detect the presence of l ung injury even when conventional histologic, morphometric, and gravim etric studies provide negative or equivocal results, and that the CMPG T-2 ,method is superior, in this respect, to the Hahn decay method. T -1, does not appear to be sensitive to lung injury in the absence of s ignificant lung water accumulation.