Table 2 Brain disease impedance spectra

Epilepsy

In vivo/rat

Impedance decreased gradually during a seizure and reached a minimum at the end of the seizure. Following seizure activity, the impedance returned to the interictal baseline or increased to a level above the baseline

Stroke

Ex vivo/rabbit

In vivo/rabbit

Impedance spectra of stroke lesions significantly differed to those of normal brain tissue; the ratio of change in impedance of ischemic and hemorrhagic tissue with regard to frequency was distinct; tissue type could be distinguished according to impedance spectra

Brain injuries and cerebral edema

23 patients with brain edema

Overall impedance across the brain increased significantly before and after mannitol dehydration treatment (P = 0.0027)

Ex vivo/male rats

After the first 6 h following the onset of ischemic brain injury, the resistivity of brain tissue increased (P < 0.05); from 6 to 24 h, the resistivity of brain tissue decreased

Patients with cerebral hemorrhage

Dehydration effects induced changes in average reconstructed impedance value and intracranial pressure exhibited a strong negative correlation in all patients (mean correlation: R² = 0.78 ± 0.16, P < 0.001)

Brain abscess

In vivo canine model

Relative conductivity contrast ratios (rCCR, %) of central abscess lesions were higher than those of surrounding areas at 6, 12, and 18 h (P < 0.01). Over 12 h, the relationship between induction time and rCCR exhibited a positive correlation followed by a negative correlation (P < 0.01)

Brain neoplasms

Three-dimensional finite element model

Tumor-like anomalies with 200% conductivity contrast were straightforwardly detected and imaged using an existing 3 T system with total acquisition time under 30 min