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《Brain stimulation》2021,14(3):488-497
BackgroundTranscranial electric stimulation during MR imaging can introduce safety issues due to coupling of the RF field with the stimulation electrodes and leads.ObjectiveTo optimize the stimulation setup for MR current density imaging (MRCDI) and increase maximum stimulation current, a new low-conductivity (σ = 29.4 S/m) lead wire is designed and tested.MethodThe antenna effect was simulated to investigate the effect of lead conductivity. Subsequently, specific absorption rate (SAR) simulations for realistic lead configurations with low-conductivity leads and two electrode types were performed at 128 MHz and 298 MHz being the Larmor frequencies of protons at 3T and 7T. Temperature measurements were performed during MRI using high power deposition sequences to ensure that the electrodes comply with MRI temperature regulations.ResultsThe antenna effect was found for copper leads at ¼ RF wavelength and could be reliably eliminated using low-conductivity leads. Realistic lead configurations increased the head SAR and the local head SAR at the electrodes only minimally. The highest temperatures were measured on the rings of center-surround electrodes, while circular electrodes showed little heating. No temperature increase above the safety limit of 39 °C was observed.ConclusionCoupling to the RF field can be reliably prevented by low-conductivity leads, enabling cable paths optimal for MRCDI. Compared to commercial copper leads with safety resistors, the low-conductivity leads had lower total impedance, enabling the application of higher currents without changing stimulator design. Attention must be paid to electrode pads.  相似文献   
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《Heart rhythm》2020,17(8):1371-1380
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Background and aimRecurrent atherothrombotic events have been reported in certain higher risk subsets of patients even with ticagrelor, a potent first-line antiplatelet agent for the management of patients with acute coronary syndrome (ACS). Hyperhomocysteinemia is a known determinant of platelet function abnormalities. Therefore, the aim of our study was to evaluate the impact of homocysteine (Hcy) levels on platelet reactivity in patients receiving Ticagrelor.Methods and resultsPatients with ACS undergoing percutaneous coronary revascularization and on dual antiplatelet therapy with ASA + Ticagrelor (90mg/twice a day) were scheduled for platelet function assessment 30–90 days post-discharge. Aggregation tests were performed by Multiple Electrode Aggregometry (MEA). Suboptimal platelet inhibition HRPR-high residual platelet reactivity was defined if above the lower limit of normality (417 AU*min).We included 432 patients, divided according to Hcy tertiles. Higher Hcy levels were associated with age, renal failure, creatinine levels and use diuretics (p < 0.001).Patients with higher Hcy levels displayed a higher platelet reactivity at COL test (p = 0.002), and ADP test (p = 0.04), with a linear relationship between Hcy and platelet aggregation after stimulation with collagen (r = 0.202, p < 0.001), thrombin receptor peptide (r = 0.104, p = 0.05) and ADP (r = 0.145, p = 0.006).However, Hcy levels did not significantly affect the rate of HRPR with Ticagrelor (9.9% vs 13.7% vs 10.7%, p = 0.89; adjusted OR [95% CI] = [0.616–1.51], p = 0.99).ConclusionsAmong patients with ACS, despite the elevated platelet reactivity associated to hyperhomocysteinemia, DAPT with ticagrelor could overcome such phenomenon, achieving an adequate platelet inhibition in the majority of the patients.  相似文献   
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While simultaneous acquisition of electrocardiography (ECG) data during MRI is a widely used clinical technique, the effects of the MRI environment on impedance cardiography (ICG) data have not been characterized. We collected echo planar MRI scans while simultaneously recording ECG and thoracic impedance using carbon fiber electrodes and customized amplifiers. Here, we show that the key changes in impedance (dZ/dt) and features of the ECG waveforms are not obstructed during MRI. We present a method for ensemble averaging ICG/ECG signals collected during MRI and show that it performs comparably with signals collected outside the MRI environment. These results indicate that ICG can be used during MRI to measure stroke volume, cardiac output, preejection period, and left ventricular ejection time.  相似文献   
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IntroductionThe conventional evaluation of neural telemetry and impedance requires the use of the computer coupled to an interface, with software that provides visualization of the stimulus and response. Recently, a remote control (CR220®) was launched in the market, that allows the performance of intraoperative tests with minimal instrumentation.ObjectiveTo evaluate the agreement of the impedance values and neural telemetry thresholds, and the time of performance in the conventional procedure and by the remote control.MethodsMulticentric prospective cross-sectional study. Intraoperative evaluations of cochlear implants compatible with the use of CR220® were included. The tests were carried out in the 22 electrodes to compare the time of performance in the two situations. The agreement of the neural telemetry threshold values obtained from five electrodes was analyzed, and the agreement of impedance was evaluated by the number of electrodes with altered values in each procedure.ResultsThere were no significant difference between the impedance values. There was a moderate to strong correlation between the electrically-evoked compound action potential thresholds. The mean time to perform the procedures using the CR220 was significantly lower than that with the conventional procedure.ConclusionThe use of the CR220 provided successful records for impedance telemetry and automatic neural response telemetry.  相似文献   
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Time perception is a fundamental component of everyday life. Although time can be measured using standard units, the relationship between an individual's experience of perceived time and a standard unit is highly sensitive to context. Stressful and threatening stimuli have been previously shown to produce time distortion effects, such that individuals perceive the stimuli as lasting for different amounts of time as compared to a standard unit. As a highly social species, humans are acutely sensitive to social stressors; however, time distortion effects have not been studied in the context of social stress. We collected psychophysiological (electrocardiogram and impedance cardiography) and time perception data before, during, and after a modified version of the Trier Social Stress Test for 42 participants. Based on prior theories and evidence from the time perception literature, we hypothesized that experiencing a stressful event would result in time distortion. This hypothesis was supported by the data, with individuals on average reproducing short and long duration negative and positive stimuli as lasting longer after experiencing social stress, t(41) = −3.55, p = .001, and t(41) = −4.12, p < .001 for negative stimuli, and t(41) = −2.43, p = .02, and t(41) = −3.07, p = .004 for positive stimuli. However, changes in time perception were largely unrelated to psychophysiological reactivity to social stress. These findings are in line with some other studies of time distortion, and provide evidence for the interoceptive salience model of time perception. Implications for mechanisms of time distortion are discussed.  相似文献   
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Objective

To evaluate the hemodynamic effects of using an adhesive glove device (AGD) to perform active compression–decompression CPR (AGD-CPR) in conjunction with an impedance threshold device (ITD) in a pediatric cardiac arrest model.

Design

Controlled, randomized animal study.

Methods

In this study, 18 piglets were anesthetized, ventilated, and continuously monitored. After 3 min of untreated ventricular fibrillation, animals were randomized (6/group) to receive either standard CPR (S-CPR), active compression–decompression CPR via adhesive glove device (AGD-CPR) or AGD-CPR along with an ITD (AGD-CPR + ITD) for 2 min at 100–120 compressions/min. AGD is delivered using a fingerless leather glove with a Velcro patch on the palmer aspect and the counter Velcro patch adhered to the pig's chest. Data (mean ± SD) were analyzed using one-way ANOVA with pair wise multiple comparisons to assess differences between groups. p-Value ≤ 0.05 was considered significant.

Results

Both AGD-CPR and AGD-CPR + ITD groups produced lower intrathoracic pressure (IttP, mmHg) during decompression phase (−13.4 ± 6.7, p = 0.01 and −11.9 ± 6.5, p = 0.01, respectively) in comparison to S-CPR (−0.3 ± 4.2). Carotid blood flow (CBF, % of baseline mL/min) was higher in AGD-CPR and AGD-CPR + ITD (respectively 64.3 ± 47.3%, p = 0.03 and 67.5 ± 33.1%, p = 0.04) as compared with S-CPR (29.1 ± 12.5%). Coronary perfusion pressure (CPP, mmHg) was higher in AGD-CPR and AGD-CPR + ITD (respectively 19.7 ± 4.6, p = 0.04 and 25.6 ± 12.1, p = 0.02) when compared to S-CPR (9.6 ± 9.1). There was no statistically significant difference between AGD-CPR and AGD-CPR + ITD groups with reference to intra-thoracic pressure, carotid blood flow and coronary perfusion pressure.

Conclusion

Active compression decompression delivered by this simple and inexpensive adhesive glove device resulted in improved cerebral blood flow and coronary perfusion pressure. There was no statistically significant added effect of ITD use along with AGD-CPR on the decompression of the chest.  相似文献   
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