Electrical Phenotyping of Human Brain Tissues: An Automated System for Tumor Delineation

Precise surgical excision of brain tumors depends on the surgeon's ability to accurately differentiate tumors from healthy brain tissues. We have developed an automated system integrated with biochips, an actuation unit, and electronics to measure the electrical resistivity of ex vivo human brain tissues for differentiating normal and tumor. The electrical resistivity of fresh (n = 48), formalin-fixed for one week (n = 48), and long-term (six months) formalin-fixed (n = 27) healthy human brain samples from different anatomical regions and tumor samples (glioma n = 6; fresh, formalin-fixed for one week, and formalin-fixed for six months) were measured using the automated system. The resistivity of glioma (22.4 ± 1.6~\Omega .cm) was significantly lesser than the normal region (98.6 ± 1.4~\Omega .cm) for fresh tissue samples (p = 5e-8). The trend of lower resistivity of glioma compared to normal was preserved after one week and six months of formalin fixation. We also report the effects of heterogeneity of normal brain tissue and formalin-fixation on the electrical properties of tissues. White matter regions were found to have higher resistivity compared to grey matter regions. The heterogeneity associated with grey matter regions was lower than the white matter regions. Formalin-fixation was observed to increase the magnitude of resistivity measured while retaining the observed trend across the different regions of the brain and tumors. The study shows that the electrical resistivity could potentially be used as an additional biomarker for delineating normal from the tumor.