Tumour detection, treatment planning and response assessment using functional magnetic resonance


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Martin O Leach1
1The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, UK, London, UK

Abstract

MRI is widely used for cancer detection, diagnosis and staging, with a growing role in targeted screening. Most of these applications use morphological imaging, but functional imaging techniques play an increasingly important role, adding to information provided by the range of contrasts available from conventional imaging. In these applications, dynamic contrast enhanced imaging (DCE-MRI) can provide increased specificity, aid detection of disease and add information on the vascular support of tumours, reflecting the biological control of angiogenesis. Diffusion weighted MRI (DWI-MRI) is rapidly growing in use, informing on cellularity and the local barriers to water diffusion, with whole body measurements enabling surveys for metastatic spread. In addition to DWI images, the apparent diffusion coefficient (ADC) can be calculated, providing a quantitative assessment, contributing information that can characterise disease and may inform on perfusion.

These techniques are also widely used to assess response, providing information reflecting the biological changes that occur. Response to treatment can be complex, and the measurements will reflect the biology and tumour make up at the time of measurement, so may be affected by normalisation and repopulation. A range of further techniques are available, with newer techniques enabling a wide range of spatially registered metabolic and physiological information to be acquired. Techniques include relaxation time measurements affected by hypoxia, vascularity, protein binding together with a range of contrast agents; arterial spin labelling to evaluate perfusion; magnetic resonance spectroscopy (MRS) reporting on energetic and lipid metabolism and aiding diagnosis; hyperpolarised 13C measurements using pyruvate and a number of labelled metabolites; amino acid and glucose exchange saturation transfer; bound water content; MR elastography. Further developments in contrast agents and hyperpolarised probes are at the preclinical stage. Hybrid devices for MR/PET, MR/HIFU and MR/RT are entering clinical use or trial.