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Determination of lactate concentrations in vivo is required in the noninvasive diagnosis, staging, and therapeutic monitoring of diseases such as cancer, heart disease, and stroke. An iterative filtering process based on the continuous wavelet transform (CWT) method in the time domain is proposed to isolate the lactate doublet signal from overlapping lipid resonances and estimate the magnetic resonance spectroscopy (MRS) parameters of the lactate methyl signal (signal amplitude, chemical shift, J-coupling and apparent transverse relaxation time (T* 2 )). This method offers a number of advantages over the multiple quantum (MQ) and difference spectroscopy approaches, including: 1) full recovery of the lactate methyl signal, whereas the MQ methods usually detect 50% of the signal intensity; 2) in contrast to MQ methods, the lipid signal is retained together with J-coupling data on the lactate peak; 3) the CWT method is much less sensitive to motion artifacts than difference spec- Lactate is a sensitive indicator of glycolysis, cellular oxygenation, and energy status in living tissues. Considerable effort has been devoted to the detection and the quantification of lactate methyl resonances by means of proton ( 1 H) magnetic resonance spectroscopy (MRS) (1-26). Its measurement may play a significant role in diagnosis, staging, and monitoring of therapeutic response of various human diseases. Changes in lactate level have been strongly correlated with several pathologies of muscle (1) and brain (2,3), as well as head and neck tumors (4). Response of tumors to chemotherapy (5) and radiation therapy (6) has been associated with a decrease in MRS detectable lactate. However, the direct measurement of the lactate methyl resonance requires elimination of the interfering lipid resonances. The large coresonant lipid signals at 1.30 ppm may completely obscure the lactate methyl doublet. Numerous spectral editing methods have been designed to selectively separate the lactate and lipid signals. These methods are based on a wide range of approaches, such as difference spectroscopy with J-modulation (7-12), selective polarization transfer (13,14), zeroquantum (15-17), and multiple-quantum coherence transfer (18 -25), as well as longitudinal two-spin order filtering (26,27).The two most popular spectral editing methods are multiple-quantum (MQ)-based sequences and J-modulation difference spectroscopy. Although the spectral methods based on MQ filters offer excellent lipid suppression, they usually fail to provide complete recovery of lactate signal intensity (see Discussion) (28). The MQ methods also do not provide J-coupling information. Methods employing difference spectroscopy detect the lactate doublet with full signal intensity recovery, but the requirement for acquisition of separate signals introduces sensitivity to motion artifacts (13,18), and B 1 field scaling errors (28).The wavelet transform technique is a time-scale method, which can be used to decompose an observation (i.e., a signal), into a set of detail signals the...

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Since tissue oxygen tension is a balance between delivery and consumption of oxygen, considerable effort has been directed at increasing the former and/or decreasing the latter. Techniques to decrease the rate of cellular oxygen consumption (increasing the distance oxygen can diffuse into tissues) include increasing glycolysis by administering supraphysiologic levels of glucose. We have examined the effect of hyperglycemia produced by intravenous glucose infusion on the tissue oxygenation and radiation response of subcutaneously implanted murine radiation induced fibrosarcomas (RIF-1). A 0.3 M glucose solution was delivered via tail vein injection according to a protocol that maintained glucose at a plasma concentration of 17±1 mM. The effect of this treatment on radiation response (clonogenic and growth delay studies), tumor oxygenation (needle electrode pO 2 and 2-[2-nitro-1Himidazol-1-yl]-N-(2,2,3,3,3-pentafluoropropyl) acetamide (EF5) binding), and tumor bioenergetics and pH (31 P NMR spectroscopy) was examined. Systemic measurements included hematocrit and blood glucose and lactate concentrations. The results of these studies suggest that these subcutaneously implanted RIF-1 tumors are both radiobiologically and metabolically hypoxic and that intravenous glucose infusion is not an effective method of modifying this metabolic state.