As a very common secondary disease after traumatic brain injury (TBI), brain edema can lead to increased intracranial water content and elevated intracranial pressure (ICP), which makes the patient suffer a less favorable prognosis outcome such as hemiplegia, aphasia, dysgnosia, and even death. Its realtime monitoring is of great significance for improving the therapeutic condition of TBI and reducing the mortality and disability rate. Magnetic induction phase shift (MIPS) has the advantages of non-invasive, non-contact, strong penetration, and real-time bedside monitoring. In this work, 34 rabbits divided into the experimental group (n = 26) and control group (n = 8) were used to carry out 24-h MIPS monitoring in brain edema. Meanwhile, ICP and brain water content (BWC) were chosen as references. The MIPS of rabbits in the experimental group decreased continuously in 24 h, while the ICP and BWC increased. Furthermore, MIPS detection sensitivity became lower and lower within the development of brain edema. The weights of ICP and BWC estimated by MIPS in three different stages were calculated to get the index of brain edema severity (BESI), which can evaluate the severity of brain edema. The BESI of rabbits in the experimental group increased over time, ranging from 0 to 1. The 0 represents normal, and the 1 represents severe brain edema. The first stage of BESI changed from 0 to 0.43, the second stage from 0.43 to 0.917, and the third stage from 0.917 to 1. The BESI of rabbits in the control group did not increase obviously within time. There were significant differences among them. Through the comparative experimental study of MIPS, ICP, and BWC on rabbits with brain edema, a more effective and direct parameter was found, which can promote the application value of MIPS in the real-time bedside monitoring of brain edema.INDEX TERMS Cerebral edema, magnetic induction, intracranial pressure, brain water content.
As a common secondary disease, edema after traumatic brain injury (TBI) can increase brain volume, resulting in elevated intracranial pressure (ICP), brain shift, and cerebral hernia, and can eventually lead to death. The real-time continuous monitoring of edema may significantly reduce mortality and disability. In this paper, a dual-parameter synchronous monitoring system of edema based on the reflection and transmission characteristics of the two-port test network was established; 15 rabbits were chosen to perform 24-h reflection phase shift (RPS) and transmission phase shift (TPS) simultaneously monitoring the experiments of brain edema. With the development of brain edema, the variation law of the RPS and TPS was investigated. Combined with the power amplitude spectrum and the principle of the two-port test network, the influence of frequency on the detection sensitivity of RPS and TPS was analyzed in detail, and the optimal detection frequency point was found. After that, the classification of three different degrees of edema is performed by the BP algorithm. In the animal experiment, the RPS showed a continuous increasing trend within time, and it presented the variation of (9.35910 • ± 1.65702 •), (12.60117 • ± 2.30218 •), and (16.33423 • ± 2.11118 •) after 6, 12, and 24 h, respectively. Meanwhile, the TPS showed a continuous downward trend with the variation of (−12.62555 • ± 0.99441 •), (−19.23976 • ± 1.27488 •), and (−27.26285 • ± 2.62291 •) after 6, 12, and 24 h, respectively. The RPS was negatively correlated with the TPS. The RPS and the TPS together as a recognition feature can achieve 100% accurate classification of three different brain edema severities. Based on these results, it can be concluded that the system established in this paper can monitor gradual increases in brain edema severity. Furthermore, neither the RPS nor the TPS can be set as the recognition feature alone to achieve the completely accurate classification, which shows the necessity of presenting two parameters in the monitoring process. INDEX TERMS Brain edema, two-port test network, synchronous monitoring, classification.
Cerebral edema (CE) is a non-specific pathological swelling of the brain secondary to any type of neurological injury. The real-time monitoring of focal CE mostly found in early stage is of great significance to reduce mortality and disability. Magnetic Induction Phase Shift (MIPS) is expected to achieve non-invasive continuous monitoring of CE. However, most existing MIPS sensors are made of hard materials which makes it difficult to accurately retrieve CE information. In this article, we designed a conformal two-coil structure and a single-coil structure, and studied their sensitivity map using finite element method (FEM). After that, the conformal MIPS sensor that is preferable for local CE monitoring was fabricated by flexible printed circuit (FPC). Next, physical experiments were conducted to investigate its performance on different levels of simulated CE solution volume, measurement distance, and bending. Subsequently, 14 rabbits were chosen to establish CE model and another three rabbits were selected as controls. The 24-hour MIPS real-time monitoring experiments was carried out to verify that the feasibility. Results showed a gentler attenuation trend of the conformal two-coil structure, compared with the single-coil structure. In addition, the novel flexible conformal MIPS sensor has a characteristic of being robust to bending according to the physical experiments. The results of animal experiments showed that the sensor can be used for CE monitoring. It can be concluded that this flexible conformal MIPS sensor is desirable for local focusing measurement of CE and subsequent multidimensional information extraction for predicting model. Also, it enables a much more comfortable environment for long-time bedside monitoring.
Background To investigate the feasibility of intracranial pressure (ICP) monitoring after traumatic brain injury (TBI) by electromagnetic coupling phase sensing, we established a portable electromagnetic coupling phase shift (ECPS) test system and conducted a comparison with invasive ICP. Methods TBI rabbits’ model were all synchronously monitored for 24 h by ECPS testing and invasive ICP. We investigated the abilities of the ECPS to detect targeted ICP by feature extraction and traditional classification decision algorithms. Results The ECPS showed an overall downward trend with a variation range of − 13.370 ± 2.245° as ICP rose from 11.450 ± 0.510 mmHg to 38.750 ± 4.064 mmHg, but its change rate gradually declined. It was greater than 1.5°/h during the first 6 h, then decreased to 0.5°/h and finally reached the minimum of 0.14°/h. Nonlinear regression analysis results illustrated that both the ECPS and its change rate decrease with increasing ICP post-TBI. When used as a recognition feature, the ability (area under the receiver operating characteristic curve, AUCs) of the ECPS to detect ICP ≥ 20 mmHg was 0.88 ± 0.01 based on the optimized adaptive boosting model, reaching the advanced level of current noninvasive ICP assessment methods. Conclusions The ECPS has the potential to be used for noninvasive continuous monitoring of elevated ICP post-TBI.
Objective: This study aimed to perform experiments to investigate the change trend in brain magnetic induction phase shift (MIPS) during hemorrhagic shock of different degrees of severity and to find the correlation between brain MIPS value and commonly used physiological indicators for detecting shock so as to explore a noninvasive method suitable for prehospital real-time detection of cerebral blood perfusion in hemorrhagic shock. Approach: The self-developed MIPS detection system was used to monitor the brain MIPS value in the whole process of hemorrhagic shock models of rabbits with different degrees of severity (control, mild, moderate, and severe) of shock in real time. Meanwhile, common physiological parameters, including arterial blood lactate (ABL), mean arterial pressure (MAP), heart rate (HR),core body temperature (CBT), regional cerebral blood flow (rCBF), and electroencephalogram (EEG), were also evaluated. Main results: The findings suggested that the brain MIPS value showed a downward trend in the shock process, and the decline degree of the MIPS value positively correlated with the severity of shock. Moreover, it showed a good detection and resolution ability in time/process and severity (P < 0.05). The MIPS values significantly correlated with ABL (P < 0.01), CBT (P < 0.01), and EEG (P < 0.05) at all four shock levels; with MAP (P < 0.05) and rCBF (P < 0.05) in the control, moderate, and severe groups; and with HR (P < 0.01) only in the severe group. Significance: The results demonstrated that the brain MIPS value has the capability of detecting hemorrhagic shock. The MIPS technique is a noninvasive method suitable for prehospital real-time detection of cerebral blood perfusion in hemorrhagic shock.
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