**2.4.1 Functional imaging for eloquent tissue localization**

Considerable advances in functional imaging have been made in both technology and availability, raising the question of whether it may eventually supplant intraoperative ECS mapping. Devices such as fMRI and PET units may aid in the preoperative planning of resection strategy, but these techniques, while reliable for detecting the motor area, remain too imprecise for complex functions such as language mapping where their sensitivity (PET, 75%; fMRI, 81%) and specificity (PET, 81%; fMI, 53%) are suboptimal. (Fitgerald et al., 1997; Herolz et al., 1996, 1997). These modalities highlight language-associated areas of indeterminate significance, and they do not offer real-time information intraoperatively. To this end, MRI neuronavigational techniques can facilitate not only greater resection, but embedding of DTI can also prevent inadvertent resection of adjacent subcortical pathways (Talos et al., 2007; Wu et al., 2007). Although the use of DTI has not been shown to impact directly on patient survival, its utility resides in maximizing tumor resection while minimizing morbidity. Nevertheless, for the identification of functional language pathways and guidance of safe tumor removal, these diagnostic imaging tools remain supplements to, not substitutes for, direct intraoperative stimulation mapping.

#### **2.4.2 Structural imaging for tumor periphery localization**

In glioma surgery, the approach to subcortical diffuse gliomas and the decision to resect the infiltrated brain surrounding the tumor core are the cornerstones of modern, aggressive surgical strategy. This is the rationale for a sound command of knowledge of brain functions at the tumor margin in individual cases. Non-enhancing tumor periphery, pattern (sharp or blurred) and characteristics (edema or infiltrated brain) constitute the challenging part of the operation where most effort is concentrated. MRI, FLAIR and T2 weighted images will visualize structural properties but their priority is controversial. Spectroscopy and DTI have been advocated as promising tools for delineating the extent of tumor infiltration (Price, et al., 2003; Stadbauer, et al., 2004, 2006). In addition, anisotropy measures have attempted to differentiate edema from infiltrated brain (Lu, et al., 2003, 2004). In contrast, perfusion can help to distinguish tumor grading but has not given information about the periphery so far.
