PROJECT SUMMARY
Functional activation of the cerebral cortex creates a robust increase in local temperature by increasing blood
flow and metabolism because of neurovascular coupling. Changes in surface brain temperature while an
awake patient performs a motor, sensory, or language task can be used to infer spatial patterns of activity to
create functional maps. Awake neurosurgery is used in the management of drug-resistant epilepsy, glioma,
and neurovascular malformation, in order to localize seizure and/or physiologic activity. Protection of key
functional areas is imperative to avoiding postoperative neurologic deficits. Currently, direct electrical
stimulation (DES) is the most commonly used method of intraoperative surgical mapping, which identifies
functionally critical brain regions so they are not resected. However, DES has low spatial resolution (~1 cm),
may provoke seizures, and can only test one area at a time. This project investigates a new method of
intraoperative functional mapping based on infrared thermography, which has high resolution (~100 micron)
and simultaneously monitors the entire exposed brain surface without risk for seizures. The Intraoperative
Mapping System will be developed and tested on glioma patients, as tumors have relatively static impact on
brain temperature compared to epileptogenic foci and vascular malformations. Preliminary data in motor and
language mapping cases shows large (~0.5oC) positive thermal activation of contralateral motor cortex and
language regions that have strong agreement with DES. Aim 1 will develop a mapping system (hardware and
software) required to conduct real-time thermal-based brain mapping during awake craniotomy. We will
optimize and integrate the infrared recording procedure within the surgical workflow, to maximize signal quality
while minimizing treatment interference. The central piece is a mobile cart containing a powerful workstation
and an articulating arm to locate the IR camera over the craniotomy. The computer will deliver stimuli, monitor
and collect behavioral data (audio, video, and a wireless haptic glove), record the IR images, and display the
real-time functional map. Patient tasks currently used during DES will be adapted for thermographic recording.
Aim 2 will explore the temporal and spatial properties of the thermodynamic response to optimize the infrared
mapping procedure. The thermal response function (TRF) is the thermal equivalent of the hemodynamic
response function (HRF) that is used in fMRI. Through modeling and high resolution (spatial and temporal) IR
data, we will estimate the thermal impulse response and use it to develop an efficient multi-task mapping
protocol. The result will be a rapid, efficient, high resolution assessment of brain function to optimize the
resection and improve patient outcomes. Aim 3 will compare the functional mapping methods (DES and
infrared thermal imaging) to determine optimal synergy between them to provide the best information for the
safest resection. If successful, this project will create a new method for intraoperative functional mapping
during awake neurosurgery. Ultimately, we hope to improve the precision of intraoperative brain mapping while
increasing the safety and efficacy of surgery for patients with drug-resistant epilepsy, glioma, and
neurovascular malformations.
