1: Magn Reson Med. 2006 Sep;56(3):637-43.

Complex relationship between changes in oxygenation status and changes in R(*)
(2): The case of insulin and NS-398, two inhibitors of oxygen consumption.

Jordan BF, Crokart N, Baudelet C, Cron GO, Ansiaux R, Gallez B.

Laboratory of Biomedical Magnetic Resonance, Universite Catholique de Louvain,
Brussels, Belgium.

Insulin and NS-398 have been reported to inhibit oxygen consumption in
experimental tumor models, thereby increasing oxygenation and
radiosensitization. The aim of this work was to use MRI to study changes in
murine FSaII tumor hemodynamics after administration of those oxygen consumption
inhibitors. A multiple-echo gradient-echo (GRE) MRI sequence (4.7 T) was used to
map changes in three factors: the GRE signal (at TE = 20 ms), the parameter S(0)
(theoretical signal at TE = 0 ms), and the relaxation rate R(*) (2). Perfusion
maps were obtained by dynamic contrast-enhanced (DCE) MRI. Insulin caused a
significant decrease in the tumor blood oxygen level-dependent (BOLD) signal
over time. factor This was likely the result of decreased blood flow, since both
S(0) and the percentage of perfused tumor decreased as well. Tumor R(*) (2) did
not change significantly in response to the treatments, which is surprising
considering that other non-MRI techniques (electron paramagnetic resonance (EPR)
oximetry and fiber-optic probes) have shown that tumor oxygenation increases
after treatment. This suggests that metabolic changes associated with vasoactive
challenges may have an unpredictable influence on blood saturation and R(*) (2).
In conclusion, this study further emphasizes the fact that changes in BOLD
signal and R(*) (2) in tumors do not depend uniquely on changes in oxygenation
status. Magn Reson Med, 2006. (c) 2006 Wiley-Liss, Inc.

PMID: 16897769 [PubMed - in process]

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