The general objective of this proposal is to develop techniques and pulses which will improve localized magnetic resonance spectroscopy (MRS) and imaging (MRI) studies in vivo, and to apply combined MRS and MRI using these new and previously developed methods to study specific physiologic questions related to intracerebral tumors. A major effort in the proposed study will focus on the development of adiabatic pulses which are insensitive to RF inhomogeneity and which can 1) induce any desired rotation angle, 2) achieve solvent suppression, 3) provide homo-and heteronuclear spectral editing in a single acquisition, despite large variations in RF magnitude. These pulses will enable the use of surface coils as though they generate a highly homogeneous RF field. These methods will be applied in MRS and MRI studies of the metabolism of intracerebral gliomas in rats. A general goal will be to establish whether 1H MRS can detect and define unique metabolic features which distinguish malignant gliomas from normal brain and may ultimately be beneficial in clinical diagnosis. A specific goal will be to gain a better understanding of the regulation of tumor pH. Decreased tumor pH has been shown to sensitize tumors to hyperthermia treatments, as well as to inhibit proliferation of malignant cells. Acute hyperglycemia has been shown to decrease pH in experimental subcutaneous gliomas, but has questionable efficacy in the reduction of intracerebral tumor pH.
A specific aim of this study is to induce intracerebral tumor acidosis through the combined effects of hyperglycemia and vasoactive drugs.
