Fig. 1. Schematic diagram of the transmissive terahertz time-domain spectroscopy system

Fig. 2. Results of TTC staining of brain tissues at different ischemia time. (a) 0 h; (b) 2 h; (c) 4 h; (d) 6 h; (e) 24 h

Fig. 3. Preparation of fresh brain ischemic tissue sections

Fig. 4. Terahertz wave properties of the left and right brains of fresh cerebral ischemic tissue at 4 h. (a) Time domain spectrum; (b) frequency domain spectrum; (c) average absorption coefficient; (d) average refractive index

Fig. 5. Relative difference of terahertz wave absorption coefficients between left and right brains in fresh brain tissue at different ischemia time

Fig. 6. Changes in physical properties of brain tissue at different ischemia time. (a) Water content of left and right brains; (b) cell density of left brain

Fig. 7. Preparation of paraffin-embedded cerebral ischemic tissue

Fig. 8. Terahertz wave absorption characteristics of paraffin-embedded cerebral ischemic tissue. (a) Absorption coefficient of left and right brains in paraffin-embedded cerebral ischemic tissue at 4 h; (b) relative difference of terahertz wave absorption coefficients in paraffin-embedded brain tissue between left and right brains at different ischemic time

Fig. 9. Normalized relative difference terahertz wave absorption coefficients between left and right brains and cell density of left brain