Localized in vivo H-1 NMR spectroscopy of murine tumours: effect of blood flow reduction

Single voxel H-1 localized spectroscopy (PRESS at 300 MHz) was used to moni tor physiological and biochemical changes induced by hydralazine (5 mg/kg, i.p.) in murine C3H mammary tumours. In addition to a significant increase (by 52%, maximal at 30 min) in the intensity of the 1.32 ppm signal (predom inantly from lactate, consistent with a selective reduction in tumour blood supply by hydralazine), downfield shifts in the resonance frequencies of H -1 signals were observed. In particular, the signal initially at 3.24 ppm ( total choline, tCho) shifted by 0.050 ppm (maximal at 13 min), whereas wate r shifted by 0.086 ppm. Lactate intensity and water and tCho resonance freq uencies returned to control values at approximately 100 min after treatment . No significant changes in the resonance frequencies of water or tCho were observed over this time period in the tumours of mice given saline. In vit ro studies showed that, while the resonance frequency of water was temperat ure dependent, the main components of the tCho signal (choline, phosphorylc holine and glycerophosphorylcholine) were more than 30-fold less sensitive to temperature. It was concluded that the shift in the water resonance freq uency was due to the combined effects of tumour temperature reduction and a paramagnetic shift from increased deoxyhaemoglobin levels, whereas the tCh o signal was only affected by the paramagnetic shifts. Copyright (C) 1999 J ohn Wiley & Sons, Ltd.