The application of depth-pulse localized 31P NMR spectroscopy to monitor tumor metabolism and response to chemotherapy in the rat kidney

31P NMR spectroscopy studies of phospholipid metabolism in human melanoma xenograft lines differing in rate of tumour cell proliferation

The concentration of phospholipid metabolites in tumours has been hypothesized to be related to rate of cell membrane turnover and may reflect rate of cell proliferation. The purpose of the study reported here was to investigate whether 31P NMR resonance ratios involving the phosphomonoester (PME) or phosphodiester (PDE) resonance are correlated to fraction of cells in S-phase or volume-doubling time in experimental tumours. Four human melanoma xenograft lines (BEX-t, HUX-t, SAX-t, WIX-t) were included in the study. The tumours were grown subcutaneously in male BALB/c-nu/nu mice. 31P NMR spectroscopy was performed at a magnetic field strength of 4.7 T. Fraction of cells in S-phase was measured by flow cytometry. Tumour volume-doubling time was determined by Gompertzian analysis of volumetric growth data. BEX-t and SAX-t tumours differed in fraction of cells in S-phase and volume-doubling time, but showed similar 31P NMR resonance ratios. BEX-t and WIX-t tumours showed significantly different 31P NMR resonance ratios but similar fractions of cells in S-phase. The 31P NMR resonance ratios were significantly different for small and large HUX-t tumours even though fraction of cells in S-phase and volume-doubling time did not differ with tumour volume. None of the 31P NMR resonance ratios showed significant increase with increasing fraction of cells in S-phase or significant decrease with increasing tumour volume-doubling time across the four xenograft lines.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo 31P MRS of experimental tumours

More than 50% of cancers fail to respond to any individual treatment and tumour follow-up after treatment plays a major role in routine therapy planning and pharmacological research. Today, MRS is the only technological approach providing non-invasive access to tumour biochemistry. Ten years ago, expectations were raised concerning 31P MRS as an exciting and promising technical approach to the study of tumours. However the expectations have not always come to fruition. How close are we now to seeing routine 31P NMR in clinical oncology? This review of the 127 published papers shows spectroscopy results in more than 150 experimental animal tumour models. These tumour/host/treatment systems provide us with a useful basis to evaluate the current state of the art, summarize the basic knowledge presently available, determine the key points underlying the present disappointment of some clinical oncologists and stimulate new basic research. The information collected concerns the discussion of the reliability of experimental models in oncology, the technical improvement of magnetic resonance technology and the monitoring of bioenergetic status, pH regulation and phospholipid metabolism in treated and untreated tumours. Recent advances (two-thirds of the papers have been published in the last 5 years) seem to provide more optimistic perspectives than those generally accepted a few years ago, in the depressing period following early pioneering work.

Effect of differential saturation on the spatial localization performance of depth pulses

Computer simulations of Depth pulse B (theta; (2 theta [+/- x, +/- y])2; acquire) and other Depth pulses, verified by experimental surface coil NMR studies utilizing phantom samples, reveal that the spatial localization performance of Depth pulses degrades when the repetition time is short relative to T1 because of differential saturation, i.e. T1 discrimination effects. Simulations of Depth pulse A (theta; 2 theta [+/- x, +/- y]; acquire) and Depth pulse B indicate that there is no phase-cycled pulse sequence delivery order which negates the untoward effect of T1 discrimination on spatial localization performance. The results of this study demonstrate the importance of consistent magnetization preparation prior to the delivery of each phase-cycled multiple pulse sequence in a Depth pulse cycle for obtaining optimal spatial localization performance. The untoward effects of inconsistent magnetization preparation, resulting from T1 discrimination, may be ameliorated by the application of many Depth pulse cycles.