Intraoperative Optical Imaging

Excerpt

Intraoperative optical intrinsic signal imaging (iOIS) provides an unparalleled opportunity to examine the basic physiology of the functioning human brain. At the same time, iOIS poses challenges for acquisition, analysis, and interpretation that are over and above those encountered in any other intact in vivo brain mapping. This may explain why, despite a profusion of optical imaging papers in the basic neuroscience literature, there have been relatively few publications on intraoperative optical imaging since its advent in 1992. Nevertheless, the clinical and research utility of this tool is considerable, and technological advances have made it even more so.

In terms of clinical utility, the most obvious benefits of intraoperative optical imaging are obtained when it is used to map “eloquent” cortex (i.e., language, sensory, motor, or visual areas) that are adjacent to or involved in pathology. This allows maximal surgical resection of pathological tissue while leaving essential areas intact. iOIS may also allow functional characterization of normal versus pathological tissue, providing an additional means to resect lesions while avoiding functioning brain.

The research utility of intraoperative OIS is equally large. Intraoperative OIS offers the only window into the investigation of human brain function with the combined spatial and temporal resolution of optical imaging. It provides the only direct way of confirming the insights made using optical imaging techniques in other mammals. And it serves as a crucial bridge to understanding the mechanisms of noninvasive techniques such as functional MRI (fMRI).

This chapter surveys the methodology of intraoperative OIS. We include comparisons between pre- and intraoperative maps along with methods to equate them in space. We also review how intraoperative OIS has been applied to address questions of basic physiology and cognitive function. Finally, we comment on the potential use of iOIS as a clinical brain mapping tool for neurosurgical guidance, and a research tool to understand basic mechanisms of cortical physiology and pathology.