The influence of tissue conductivity on the calculation of electric field in the transcranial magnetic stimulation head model / 生物医学工程学杂志

In transcranial magnetic stimulation (TMS), the conductivity of brain tissue is obtained by using diffusion tensor imaging (DTI) data processing. However, the specific impact of different processing methods on the induced electric field in the tissue has not been thoroughly studied. In this paper, we first used magnetic resonance image (MRI) data to create a three-dimensional head model, and then estimated the conductivity of gray matter (GM) and white matter (WM) using four conductivity models, namely scalar (SC), direct mapping (DM), volume normalization (VN) and average conductivity (MC), respectively. Isotropic empirical conductivity values were used for the conductivity of other tissues such as the scalp, skull, and cerebrospinal fluid (CSF), and then the TMS simulations were performed when the coil was parallel and perpendicular to the gyrus of the target. When the coil was perpendicular to the gyrus where the target was located, it was easy to get the maximum electric field in the head model. The maximum electric field in the DM model was 45.66% higher than that in the SC model. The results showed that the conductivity component along the electric field direction of which conductivity model was smaller in TMS, the induced electric field in the corresponding domain corresponding to the conductivity model was larger. This study has guiding significance for TMS precise stimulation.

Study on deep brain magnetic stimulation method based on magnetic replicator / 生物医学工程学杂志

Existing neuroregulatory techniques can achieve precise stimulation of the whole brain or cortex, but high-focus deep brain stimulation has been a technical bottleneck in this field. In this paper, based on the theory of negative permeability emerged in recent years, a simulation model of magnetic replicator is established to study the distribution of the induced electric field in the deep brain and explore the possibility of deep focusing, which is compared with the traditional magnetic stimulation method. Simulation results show that a single magnetic replicator realized remote magnetic source. Under the condition of the same position and compared with the traditional method of stimulating, the former generated smaller induced electric field which sharply reduced with distance. By superposition of the magnetic field replicator, the induced electric field intensity could be increased and the focus could be improved, reducing the number of peripheral wires while guaranteeing good focus. The magnetic replicator model established in this paper provides a new idea for precise deep brain stimulation, which can be combined with neuroregulatory techniques in the future to lay a foundation for clinical application.

Experimental study of electric field stimulation combined with polyethylene glycol in the treatment of spinal cord injury in rats / 生物医学工程学杂志

Electric field stimulation (EFS) can effectively inhibit local Ca 2+ influx and secondary injury after spinal cord injury (SCI). However, after the EFS, the Ca 2+ in the injured spinal cord restarts and subsequent biochemical reactions are stimulated, which affect the long-term effect of EFS. Polyethylene glycol (PEG) is a hydrophilic polymer material that can promote cell membrane fusion and repair damaged cell membranes. This article aims to study the combined effects of EFS and PEG on the treatment of SCI. Sprague-Dawley (SD) rats were subjected to SCI and then divided into control group (no treatment, n = 10), EFS group (EFS for 30 min, n = 10), PEG group (covered with 50% PEG gelatin sponge for 5 min, n = 10) and combination group (combined treatment of EFS and PEG, n = 10). The measurement of motor evoked potential (MEP), the motor behavior score and spinal cord section fast blue staining were performed at different times after SCI. Eight weeks after the operation, the results showed that the latency difference of MEP, the amplitude difference of MEP and the ratio of cavity area of spinal cords in the combination group were significantly lower than those of the control group, EFS group and PEG group. The motor function score and the ratio of residual nerve tissue area in the spinal cords of the combination group were significantly higher than those in the control group, EFS group and PEG group. The results suggest that the combined treatment can reduce the pathological damage and promote the recovery of motor function in rats after SCI, and the therapeutic effects are significantly better than those of EFS and PEG alone.

Simulation study of spinal cord stimulation evoked compound action potential / 生物医学工程学杂志

Spinal cord stimulation (SCS) for pain is usually implanted as an open loop system using unchanged parameters. To avoid the under and over stimulation caused by lead migration, evoked compound action potentials (ECAP) is used as feedback signal to change the stimulating parameters. This study established a simulation model of ECAP recording to investigate the relationship between ECAP component and dorsal column (DC) fiber recruitment. Finite element model of SCS and multi-compartment model of sensory fiber were coupled to calculate the single fiber action potential (SFAP) caused by single fiber in different spinal cord regions. The synthetized ECAP, superimposition of SFAP, could be considered as an index of DC fiber excitation degree, because the position of crests and amplitude of ECAP corresponds to different fiber diameters. When 10% or less DC fibers were excited, the crests corresponded to fibers with large diameters. When 20% or more DC fibers were excited, ECAP showed a slow conduction crest, which corresponded to fibers with small diameters. The amplitude of this slow conduction crest increased as the stimulating intensity increased while the amplitude of the fast conduction crest almost remained unchanged. Therefore, the simulated ECAP signal in this paper could be used to evaluate the degree of excitation of DC fibers. This SCS-ECAP model may provide theoretical basis for future clinical application of close loop SCS base on ECAP.

Progress in hepatocyte status detection and its application in bioartificial liver support system / 生物医学工程学杂志

Bioartificial liver support system (BALSS) provides a new way to treat liver failure and leaves more time for patients who are waiting for liver transplantation. It has detoxification function as well as the human liver, at the same time it can provide nutrition and improve the internal environment inside human body. Bioreactors and hepatocytes with good biological activity are the cores of BALSS which determine the treatment effect. However, in the course of prolonged treatment, the function and activity of hepatocytes might be greatly changed which could influence the efficacy. Therefore, it is very important to detect the status of the hepatocytes in BALSS. This paper presents some common indicators of cell activity, detoxification and synthetic functions, and also introduces the commonly detection methods corresponding to each indicator. Finally, we summarize the application of detection methods of the hepatocyte status in BALSS and discuss its development trend.

Electric field simulation and analysis of modified electroconvulsive therapy and magnetic seizure therapy in a realistic human head model / 生物医学工程学杂志

Modified electroconvulsive therapy (MECT) and magnetic seizure therapy (MST) are effective treatments for severe major depression. MECT has better efficacy in the treatment than MST, but it has cognitive and memorial side effects while MST does not. To study the causes of these different outcomes, this study contrasted the electric filed strength and spatial distribution induced by MECT and MST in a realistic human head model. Electric field strength induced by MECT and MST are simulated by the finite element method, which was based on a realistic human head model obtained by magnetic resonance imaging. The electrode configuration of MECT is standard bifrontal stimulation configuration, and the coil configuration of MST is circular. Maps of the ratio of the electric field strength to neural activation threshold are obtained to evaluate the stimulation strength and stimulation focality in brain regions. The stimulation strength induced by MECT is stronger than MST, and the activated region is wider. MECT stimulation strength in gray matter is 17.817 times of that by MST, and MECT stimulation strength in white matter is 23.312 times of that by MST. As well, MECT stimulation strength in hippocampi is 35.162 times of that by MST. More than 99.999% of the brain volume is stimulated at suprathreshold by MECT. However, MST activated only 0.700% of the brain volume. The stimulation strength induced by MECT is stronger than MST, and the activated region is wider may be the reason that MECT has better effectiveness. Nevertheless, the stronger stimulation strength in hippocampi induced by MECT may be the reason that MECT is more likely to give rise to side effects. Based on the results of this study, it is expected that a more accurate clinical quantitative treatment scheme should be studied in the future.

Experimental study of Tibet miniature pig model of acute renal failure treated by a novel hybrid liver and renal support system / 重庆医学

Objective To evaluate the novel hybrid liver and renal support system the safety and efficacy of the treatment of Tibet mini pig model of renal failure .Methods Five Tibet miniature pig bilateral renal artery ligation approached to construct the models of renal failure ,treatment group was treated with therapy (CRRT mode) of the novel hybrid liver and renal support system after modeling ,while the control group received no treatment .Drawning venous blood endotoxin ,biochemical tests and aerobic anae‐robic culture when in the treatment of 0 ,4 ,8 h;then we observed the changes of biochemical indicators in Tibet mini pigs before and after treatment ;we recorded machine pressure monitoring indicators every 2 hour during treatment .Results The model of renal failure of two experimental animals were successfully constructed .The general condition of treatment group was improved after treated by the novel hybrid liver and renal support system ,while the control groups continued to deteriorate .The experimental ani‐mals did not appear abnormal ECG during the experiment .Two groups of animals showed no statistics significant difference (P>0 .05) in the period of 0 h .In the remaining period ,heart rate and respiratory rate in treatment group was significantly reduced(P0 .05);after modeling both groups biochemi‐cal indicators was significantly increased compared with baseline (P<0 .05);after treatment of the hybrid liver and renal support systems in the treatment group ,the biochemical parameters were significantly decreased compared with baseline ,the difference was statistically significant different(P<0 .05) ,while the control group did not change significantly .Blood endotoxin measured results were less than 0 .5 EU/mL ,arteriovenous end aerobic anaerobic culture showed no bacterial growth .Pathological examination showed significant swelling of the renal tubular epithelium and tubular necrosis .Conclusion The novel hybrid liver and renal sup‐port system for the treatment of Tibet mini‐pig model of renal failure is safe and effective ,and it can be further attempts for clinical trials .

Application of membrane sealing materials in repair of the spinal cord injury / 国际生物医学工程杂志

The integrity of the neuronal membrane is important for its specific physiological function.Spinal cord injury (SCI) can result in immediate disruption of neuronal membranes.Now,a novel treatment method for SCI is sealing the compromised membranes at the early stage of SCI.In this article,recent development of membrane repair agents in treating SCI is discussed,including polyethylene glycol(PEG),poloxamer 188(P188),chitosan and some nanomaterials.At the same time,problems remained in recent researches are reviewed and the prospect is discussed.

Effects of Repetitive Transcranial Magnetic Stimulation on Locomotor Outcome of Spinal Cord Injured Rats / 中国康复理论与实践

@#Objective To explore the effect of repetitive transcranial magnetic stimulation(rTMS)on spinal cord injured rats.Methods Weight-drop spinal cord injury model was made at thoracic 10 segments with NYU impactor device.Stimulated group received daily superthreshold rTMS continued for 4 weeks.BBB locomotor scores were recorded weekly.Growth associated protein 43(GAP43)and 5-hydroxytryptamine(5-HT)were detected with immunofluorescence staining in the area of rostral and caudal to the lesion.Results The BBB scores in stimulation group improved compared with that in the control(P<0.01).GAP43 and 5-HT markers increased in the stimulation group(P<0.01),and they increased in the rostral than in the caudal areas(P<0.01).Conclusion rTMS can improve the locomotor function of incomplete spinal cord injury rats,which may result from the increase of expression of GAP43 and 5-HT.

Effect of Repetitive Transcranial Magnetic Stimulation on Spinal Segmental Excitability of Spinal Cord Injury Rats / 中国康复理论与实践

@#Objective To investigate the effect of repetitive transcranial magnetic stimulation(rTMS)on the spinal segmental excitability after spinal cord injury in adult rats.MethodsT 10 spinal cord injury models were made with weight-drop method.8 weeks later,rTMS were applied to the experimental group at 0.5 Hz suprathreshold stimulation,500 pulses daily for 4 weeks.Spinal cord injury rats without stimulation and normal rats were used as controls.At different time points,electronic evoked F-wave were measured.The ratio of F-wave amplitude to M-wave amplitude(F/M)were compared among these groups.Immunohistochemistry was used to detect the expression of 5-hydroxytryptamine(5-HT)in the rostral and caudal lesion segments.ResultsThe ratio of F/M increased significantly(P<0.01)8 weeks after spinal cord injury compared with baseline ratio and regressed significantly(P<0.01)after 4 weeks of rTMS.Expression of 5-HT in grey matter around lesion was decreased after spinal cord injury and increased significantly(P<0.01)both in the rostral and caudal lesion segments in rTMS treatment group.ConclusionThe increased spinal segmental excitability after spinal cord injury can be regressed by rTMS,which may be resulted in increased expression of 5-HT.