title: Analysis of factors causing signal loss in the measurement of lung tissue water by nuclear magnetic resonance.
abstract: The water content of lung, brain, and muscle tissue was measured by nuclear magnetic resonance (NMR) and compared with gravimetric determinations. The NMR signal intensity of water was measured by a single 90 degree pulse and by a spin-echo sequence. The absolute water content was determined by the difference in the sample's weight before and after desiccation. The NMR detectable water in each tissue was expressed as a percentage of the signal intensity for an equal weight of distilled water. Using the single pulse measurement, 67% of the gravimetrically-measured water was detected in collapsed lung samples (consisting of about 47% retained air), in contrast to 96% for brain and 98% for muscle. For degassed lung samples, the NMR detectability of water increased to 87% with the single pulse measurement and to 90% with the spin-echo measurement, but the values remained significantly less than those of brain or muscle. Factors that caused the NMR signal loss of 33% in collapsed lung samples were: air-tissue interfaces (20%), microscopic field inhomogeneity (3%), and a water component with an extremely short magnetization decay time constant (10%).
authors.affiliation: Department of Communication Engineering, Tokai University Junior College, Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Fukuzaki
authors.forename: S
authors.initials: S
authors.lastname: Shioya
authors.forename: M
authors.initials: M
authors.lastname: Haida
mesh_terms: D000818:Animals; D001834:Body Water; D001923:Brain Chemistry; D008168:Lung / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009132:Muscles / Q000737:chemistry; D051381:Rats; D017208:Rats, Wistar