gms | German Medical Science

Objective: Determining the resection borders of malignant tumors and its relation neighboring functional areas remains a significant challenge for neurosurgeons. Thermographic imaging, which is based on recording a thermal map of the brain surface, has shown different patterns in tumors and healthy tissue. We studied thermal patterns of brain cortex overlying tumors to establish a basis for the development of an intraoperative imaging tool based on thermography.

Method: The exposed cerebral cortex of 83 patients with glial and metastatic tumors who underwent a craniotomy for tumor resection was recorded using a highly sensitive infrared camera with a spectral range of 7,5–14 µm, thermal resolution of 0,03K at 30°C and a spatial resolution of 150 µm per pixel at minimum distance. The time lapse data were integrated into a single data cube. Preprocessing and multivariate data analysis was performed on thermal image data using the MATLAB package. The thermogram was matched to a 3D model of the patient's brain using the Amira software package. The thermal activity and the temporal thermal signatures in exposed tumors and in brain cortex overlying tumors was compared to that of unaffected cortex.

Results: In accordance with previous results, glial tumors and their overlying cortex appeared mostly hypothermic (25 to 30°C). Metastases were also hypothermic, which contradicts observations by other authors. Borders of cortical tumors were clearly detectable due to a significant difference in temperature, while the location of deep tumors resulted in hazy cortical representations of the tumor. However, thermal variability of tumor-overlying cortex might be affected. Edematous tissue appeared hypothermic as well. Thermography delivered a good image of cortex while thermal resolution in resection cavities was thermally polluted by captured fluids and air.

Conclusions: Our study provides an extensive thermal image database of different brain tumors. Thermal imaging of deeper areas and resection cavities is hampered by artifacts. We hypothesize that thermography can detect tumor borders and identify ischemic or non-functional peritumoral areas which might turn thermography into a useful intraoperative imaging tool in neurosurgery.