EIT Imaging of Intracranial Hemorrhage in Rabbit Models Is Influenced by the Intactness of Cranium.

Electrical impedance tomography (EIT) has been shown to be a promising, bedside imaging method to monitor the progression of intracranial hemorrhage (ICH). However, the observed impedance changes within brain related to ICH differed among groups, and we hypothesized that the cranium intactness (open or closed) may be the one of potential reasons leading to the difference. Therefore, the aim of this study was to investigate this effect of open or closed cranium on impedance changes within brain in the rabbit ICH model. In this study, we first established the ICH model in 12 rabbits with the open cranium and in 12 rabbits with the closed cranium. Simultaneously, EIT measurements on the rabbits' heads were performed to record the impedance changes caused by injecting the autologous nonheparinized blood into cerebral parenchyma. Finally, the regional impedance changes on EIT images and the whole impedance changes were analyzed. It was surprisingly found that when the cranium was open, the impedance of the area where the blood was injected, as well as the whole brain impedance, decreased with the amount of blood being injected; when the cranium was closed, while the impedance of the area where blood was not injected continued to increase, the impedance of the area where blood was injected decreased within 20s of the blood being injected and then remained almost unchanged, and the whole brain impedance had a small fall and then notably increased. The results have validated that the cranium completeness (open or closed) has influences on impedance changes within brain when using EIT to monitor ICH. In future study on application of EIT to monitor ICH, the cranium completeness should be taken into account for establishing an ICH model and analyzing the corresponding EIT results.

[Case-control study of therapeutic effects between extreme lateral interbody fusion and conventional posterior operation for the treatment of upper lumbar disc herniation].

OBJECTIVE: To evaluate the clinical outcomes between extreme lateral interbody fusion and conventional posterior operation in the treatment of upper lumbar disc herniation. METHODS: Among 60 patients with upper lumbar disc herniation were treated with extreme lateral interbody fusion(XLIF) or conventional posterior operation from June 2010 to December 2014, 30 patients(19 males and 11 females) were treated with XLIF (XLIF group); and the other 30 patients(17 males and 13 females) were treated with conventional posterior operation (conventional group). In XLIF group, the lesions occurred at T12L1 segments in 2 patients, at L1,2 segments in 6 patients, at L2,3 segments in 10 patients, and at L3,4 segment in 12 patients. In conventional group, the lesions occurred at T12L1 segments in 1 patient, at L1,2 segments in 6 patients, at L2,3 segments in 8 patients, and at L3,4 segment in 15 patients. Operative incision lengths, time, blood loss, postoperative draining volume, hospital stays were recorded. Pre-and post-operative visual analogue score(VAS) and Japanese Orthopedic Association(JOA) were compared between two groups. According to the image data, the intervertebral fusion device was observed to be displaced and the rate of interbody fusion was analyzed. RESULTS: All the patients were followed up, and the duration ranged from 12 to 48 months, with an average of 29 months. The complications included 2 femoral nerve damage in XLIF group (postoperative recovery within 3 months) and superficial incision infection in conventional group(cured by anti-infection). There were no patients with cerebrospinal fluid leakage(CSFL), cauda equina injuries or functional deterioration in the nerve root of lower limbs. In the XLIF group: the operative time was (65.6±20.5) minutes, blood loss was (48.8±15.3) ml, postoperative draining volume was 0 ml. In the conventional group: the operative time was (135.2±33.9) minutes, blood loss was (260.3±125.7) ml, postoperative draining volume was (207.1±50.2) ml. The operative time, blood loss, postoperative draining volume in XLIF group were less than those in the conventional group(P<0.05). The JOA and VAS score were significantly improved in both groups during the follow-up period compared with those before operation(P<0.05). But the difference of the JOA and VAS score between the two groups 1, 6, and 24 months after surgery had not significant differences(P>0.05). There were no significant differences in the fusion rate between the two groups 6 and 12 months after operation(P>0.05). CONCLUSIONS: The XLIF fusion for the treatment of upper lumbar disc herniation has several advantages such as minimal invasive, stable vertebral plate, less complications and postoperative fusion rate, which has a better clinical effect.

Use of electrical impedance tomography to monitor regional cerebral edema during clinical dehydration treatment.

OBJECTIVE: Variations of conductive fluid content in brain tissue (e.g. cerebral edema) change tissue impedance and can potentially be measured by Electrical Impedance Tomography (EIT), an emerging medical imaging technique. The objective of this work is to establish the feasibility of using EIT as an imaging tool for monitoring brain fluid content. DESIGN: a prospective study. SETTING: In this study EIT was used, for the first time, to monitor variations in cerebral fluid content in a clinical model with patients undergoing clinical dehydration treatment. The EIT system was developed in house and its imaging sensitivity and spatial resolution were evaluated on a saline-filled tank. PATIENTS: 23 patients with brain edema. INTERVENTIONS: The patients were continuously imaged by EIT for two hours after initiation of dehydration treatment using 0.5 g/kg intravenous infusion of mannitol for 20 minutes. MEASUREMENT AND MAIN RESULTS: Overall impedance across the brain increased significantly before and after mannitol dehydration treatment (p = 0.0027). Of the all 23 patients, 14 showed high-level impedance increase and maintained this around 4 hours after the dehydration treatment whereas the other 9 also showed great impedance gain during the treatment but it gradually decreased after the treatment. Further analysis of the regions of interest in the EIT images revealed that diseased regions, identified on corresponding CT images, showed significantly less impedance changes than normal regions during the monitoring period, indicating variations in different patients' responses to such treatment. CONCLUSIONS: EIT shows potential promise as an imaging tool for real-time and non-invasive monitoring of brain edema patients.

A new head phantom with realistic shape and spatially varying skull resistivity distribution.

Brain electrical impedance tomography (EIT) is an emerging method for monitoring brain injuries. To effectively evaluate brain EIT systems and reconstruction algorithms, we have developed a novel head phantom that features realistic anatomy and spatially varying skull resistivity. The head phantom was created with three layers, representing scalp, skull, and brain tissues. The fabrication process entailed 3-D printing of the anatomical geometry for mold creation followed by casting to ensure high geometrical precision and accuracy of the resistivity distribution. We evaluated the accuracy and stability of the phantom. Results showed that the head phantom achieved high geometric accuracy, accurate skull resistivity values, and good stability over time and in the frequency domain. Experimental impedance reconstructions performed using the head phantom and computer simulations were found to be consistent for the same perturbation object. In conclusion, this new phantom could provide a more accurate test platform for brain EIT research.