Functional imaging: where do we go from here?

As highly invasive and infiltrative tumors, gliomas are hard to delineate from healthy brain parenchyma, even with the microscope enhanced eye of an experienced neurosurgeon. However, the surgical goal remains maximum extent of tumor volume resection with a preservation of neurological function. With functional data integrated and visualized in the navigation system, postoperative morbidity can be reduced. With the so far well established techniques diffusion-tensor-imaging (DTI) based fiber tractography and functional MRI (fMRI), white matter tracts or eloquent cortical areas can be displayed. With magnetic resonance spectroscopy (MRS) and also positron emmission computed tomography (PET), methods displaying brain metabolism are also widely used. However, further technical and computational development of these methods has already shown extended insights in brain networks and pathologies and promises further reduction of postoperative morbidity, while used in navigation systems. In addition to these methods, novel techniques have already been implemented and successfully used in the clinical routine. In this way, this review summarizes recent developments in DTI, fMRI, MRSI and PET, also with their use during neurosurgical operations, but also gives introduction in novel methods like navigated transcranial magnetic stimulation (nTMS) or advanced diffusion models as base for fiber tracking.