NMR temperature measurements using a paramagnetic lanthanide complex.

NMR thermometry has previously suffered from poor thermal resolution owing to the relatively weak dependence of chemical shift on temperature in diamagnetic molecules. In contrast, the shifts of nuclear spins near a paramagnetic center exhibit strong temperature dependencies. The chemical shifts of the thulium 1,4,7, 10-tetraazacyclododecane-1,4,7,10-tetrakis(methylene phosphonate) complex (TmDOTP5-) have been studied as a function of temperature, pH, and Ca2+ concentration over ranges which may be encountered in vivo. The results demonstrate that the 1H and 31P shifts in TmDOTP5- are highly sensitive to temperature and may be used for NMR thermometry with excellent accuracy and resolution. A new technique is also described which permits simultaneous measurements of temperature and pH changes from the shifts of multiple TmDOTP5- spectral lines.

23Na- and 31P-NMR studies of perfused mouse liver during nitrogen hypoxia.

The effects of nitrogen hypoxia on isolated perfused mouse livers from fed mice were studied at 37 degrees C using 23Na and 31P nuclear magnetic resonance (NMR) spectroscopy. The paramagnetic shift reagent, dysprosium-triethylenetetraminehexaacetic acid, was used to distinguish intracellular from extracellular sodium. The area of the intracellular sodium resonance remained relatively constant over the first 30 min of hypoxia and then increased by a factor of approximately 2 relative to controls over the next 30 min. High-energy phosphate metabolites were measured using 31P-NMR. The beta-ATP resonance decreased to zero, and the intracellular pH decreased from 7.3 to 6.9 during 60 min of hypoxia. Liver enzyme activity in the effluent exiting the liver increased in direct proportion to the length of hypoxia up to 56 min. The sodium, ATP, and enzyme changes during hypoxia were correlated with histological and electron-microscopic findings. The morphology of liver specimens exposed to 30 min of hypoxia was close to normal, whereas extensive centrilobular and midlobular necrosis was seen in specimens subjected to 60 and 90 min of hypoxia. The effect of 30 min of reoxygenation after 15, 30, 45, 60, and 90 min of hypoxia was also studied. The level of beta-ATP recovery depended on the duration of hypoxia. For 60 min of hypoxia followed by reoxygenation, beta-ATP recovered to only 20% of control values. The morphology of hypoxic livers after 30 min of reoxygenation was similar to livers subjected to hypoxia alone.

Response to and control of destructive energy by magnetic resonance.

Magnetic resonance imaging techniques can be used to control and monitor the deposition of destructive energy. The authors evaluated the feasibility of phosphorus-31 magnetic resonance spectroscopy for the control, monitoring, and prediction of the three-dimensional extent of tissue destruction during interstitial laser surgery. Characteristic metabolic changes were demonstrated within the lesion and in the adjacent normal tissue during the deposition of thermal energy.