Measuring lactate concentration in vivo using 1H NMR is not straightforward. In this situation, quantifying lactate potentially offers complementary information on (steady-state) lactate concentrations, particularly in organs such as the brain where the high glucose consumption and hence 18FDG uptake of normal tissue obscures their differentiation. In the clinic, 18 F-fluorodeoxyglucose ( 18FDG) positron emission tomography is used to detect tumours and monitor their response to treatment by imaging their increased glucose uptake compared with normal tissue. Additionally, measuring the concentration of lactate in animal models has been used to monitor response to both chemotherapy and radiotherapy ( 9). It is well known that neoplastic cells have an increased capacity for glycolytic metabolism ( 7) under both aerobic or anaerobic conditions as part of the malignant phenotype, thus the lactate signal would be expected to be elevated ( 8). Lactate has been shown to be elevated in rodent glioma models ( 7). Under normal physiological conditions it is produced only in low concentrations, but production is increased in certain pathological states, including cerebral ischemia ( 1), mitochondrial disease ( 2, 3) and cancer ( 4– 6), making it a potential biomarker in these conditions ( 6). © 2015 The Authors NMR in Biomedicine Published by John Wiley & Sons Ltd. SelMQC-CSI is shown to be a useful technique for measuring lactate in tumours whose signals are otherwise contaminated by lipid. Lactate was not seen in secondary metastases in the brain. Lactate was clearly seen in SelMQC spectra of glioma, even in the presence of lipids, with high grade glioma (7.3 ± 1.9 mM, mean ± standard deviation) having higher concentrations than low grade glioma (1.9 ± 1.5 mM, p = 0.048). Here it was proved to be of use in determining lactate concentrations in vivo. To evaluate the method in the brain, the sequence was tested on a group of 23 patients with treated brain tumours, either glioma ( N = 20) or secondary metastases in the brain ( N = 3). Work performed on phantoms showed good lactate detection (49%) and lipid suppression (98%) efficiencies. This study presents the use of a selective homonuclear multiple quantum coherence transfer sequence (SelMQC-CSI), at 1.5 T, to better quantify lactate in the presence of lipids. Methods of lactate quantitation are complicated because of overlap between the lactate methyl doublet CH 3 resonance and a lipid resonance at 1.3 ppm. In tumour tissues, which exhibit enhanced glycolytic metabolism, lactate signals may be elevated, making lactate a potential useful tumour biomarker. Lactate is a product of glucose metabolism.
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