Breast imaging technology: Imaging biochemistry - applications to breast cancer

The purpose of this section is to review the potential applications of magnetic resonance spectroscopy (MRS) to non-invasive probing of the underlying biochemistry of cells comprising a breast tumour. MRS does not generate an image of the tumour directly, but the spectroscopic data can now be obtained from a well localised area. Thus the biochemical information obtained from MRS can be interpreted in relation to a defined anatomical location, and images of metabolite distributions can be generated. In using MRS, the first aim is to identify surrogate biochemical markers of cellular transformation, thus differentiating benign tumours from malignant or potentially identifying the different tumour types. Subsequently, prognostic and diagnostic information is sought from the spectrum of malignant tumours. In prognosis, by yielding biochemical information on the tumour composition (eg the presence of a hypoxic or a drug-resistant fraction), MRS could allow the selection of an appropriate treatment. In diagnosis, early detection of tumour response to treatment, or monitoring of drug uptake and metabolism, could enable rapid optimisation of treatment if the tumour failed to respond. Overall, treatment that is better adapted to the individual patient could result from a better understanding of the biochemical events occurring within the tumour.So far, most patient and model system studies have focused on 31P MRS. Within the 31P spectrum, the three nucleoside triphosphate (NTP) peaks, composed primarily of ATP, together with the inorganic phosphate (Pi) and phosphocreatine peaks, are indicative of energetic status. The Pi peak can also serve as a measure of intracellular pH. The phosphomonoester (PME) signal, which can be resolved into phosphocholine (PC) and phosphoethanolamine (PE) at higher field strengths or by decoupling, together with the phosphodiester (PDE) peak, composed of glycerol phosphocholine (GPC) and glycerol phosphoethanolamine, are indicative of lipid metab