**2.1.2 Uses**

Until relatively recently few studies had applied microdialysis to patients undergoing surgical biopsy or resection of their brain tumours. To this end, clinical studies using microdialysis in patients with brain tumours offer a number of potential advantages over other methodological approaches. First, in contrast to traditional in-vitro studies, clinical microdialysis studies permit the assessment of brain tumours in-vivo, recognising the complex interactions between tumour- and host-related factors, and the role these interactions play in tumourogenesis. Second, by applying microdialysis to patients with brain tumours, rather than animal models of such tumours, clinical microdialysis eliminates the possibility of erroneous interpretation of interspecies differences or of limitations of the brain tumour model itself. Third, clinical microdialysis provides a direct measure of analytes within the ECF when compared with imaging techniques. Fourth, microdialysis easily allows repeated evaluation over an extended time course. Microdialysis therefore provides a unique method of continuously measuring brain and tumour chemistry allowing investigation of metabolites and macromolecules involved in tumourogenesis, the dynamic changes in the concentration these molecules over time, and their response to chemo- and radiotherapy. Finally, retrograde microdialysis offers the potential for the direct administration of chemotherapeutic agents to brain tumours.
