Table 1.
Characteristics of the SDH patients in this study.
Figure 1.
Establishment of brain EIT electrodes.
The left part showed that 16 electrodes were equally spaced around the scalp and in the plane where hematoma existed. The right part showed the scene of operation where an incision was marked before cutting (the patient has given written informed consent, as outlined in the PLOS consent form, to publication of his photography).
Figure 2.
Establishment of a patient-specific FEM.
The FEM was obtained by segmenting the original CT image into three parts (scalp, skull, parenchyma) and then discretizing them into those triangle elements. Each part was set to different resistivity as a prior information for the forward calculation. Considering the tradeoff between accuracy and computational cost, the number of elements was often set to 800–1000.
Table 2.
The average values of the resistivity measured at 50 kHz for D5W and living brain tissues.
Figure 3.
Calibration of the EIT system.
The left showed the realistic human skull model made by plaster within a saline-filled tank; an agar cylinder was utilized to make perturbation. The right was the resulting EIT image with the agar cylinder of 20-fold increased resistivity and of 20 mm diameter.
Figure 4.
Comparison of the ARV for agar cylinders with different increased resistivity and comparison of the sROI for agar cylinders with different diameters.
The left part demonstrated that the magnitude of ARV significantly increased with the resistivity of agar (* P<0.05); the right part also showed the sROI increased with the diameter of agar, but the sROI difference between the agar cylinders of 5 mm diameter and the ones of 10 mm diameter was insignificant.
Figure 5.
The EIT results of those SDH patients with twist drill drainage.
The top texts indicated the intracranial D5W volumes. The first left column of EIT images did not show notable resistivity changes when no D5W injected, and served as the control groups. The most right column showed the original CT images for each patient and the positions of hematoma were indicated by those red boxes.
Figure 6.
Plots of ARV against the volume of D5W.
All the data during several drainage cycles were analyzed for each patient.
Figure 7.
Plots of sROI against the volume of D5W.
All the data during several irrigation and drainage cycles were analyzed for each patient.
Figure 8.
Comparison results in ARV and sROI.
The ARV and sROI at 20 ml D5W within skull were both sigficantly (* P<0.05) larger than the ones at 5ml D5W.
Table 3.
The results of linear correlation analysis of ARV and sROI against the volumes of D5W (* P<0.05).