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Regional effects of repetition time on NMR quantitation of water in normal and edematous lungs
Author(s) -
Cutillo Antonio G.,
Morris Alan H.,
Ganesan Krishnamurthy,
Ailion David C.,
Case Thomas A.,
Durney Carl H.,
Watanabe Fumi
Publication year - 1989
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910120115
Subject(s) - lung , edema , chemistry , parenchyma , nuclear magnetic resonance , pulmonary edema , spin–lattice relaxation , lung function , nuclear medicine , pathology , medicine , physics , nuclear quadrupole resonance
It is well known that pulmonary edema is, in general, spatially nonuniform. Since the NMR spin‐lattice relaxation time ( T 1 ) is increased by lung edema, the spatial distribution of T 1 will be nonuniform. When the repetition time (TR) is short relative to the T 1 of edematous lung, lung water content will be underestimated and this underestimation will be spatially nonuniform as well. Therefore, technical artifacts which are a complex function of lung edema and its spatial distribution are expected. We compared overall and regional (topographic) lung water density measurements obtained from living rats (with normal or edematous lungs) using repetition times of 2.0 and 6.2 s (at a magnetic field of 1 T), to quantify this uneven T 1 effect for normal and edematous lungs. NMR measurements at TR = 2.0 s underestimated whole lung water density (ρ―H 2 O) (at TR = 6.2 s) by an average of 7.2% in normal rats and 22.5% in rats with pulmonary edema. Regional ρ―H 2 O underestimation (%Δρ―H 2 O) varied from 2.2 to 8.8% (group means) in normal lungs and from 7.3 to 30.8% in edematous lungs. As a result, the interquartile range (of the voxel distribution as a function of p H 2 O) underestimated the spatial nonuniformity of lung water density by 28.0% in edematous lungs, likely because of greater loss of NMR signal from high‐water‐density, long‐T 1 lung regions. Both %ΔpH 2 O and T 1 , were significantly correlated with ρ―H 2 O at TR = 6.2 s. Artifactual distortion of the spatial distribution of NMR signal intensity cannot be predicted from average T 1 values characterizing the whole lung, but rather requires a knowledge of the spatial distribution of T 1 . © 1989 Academic Press, Inc.