Detection of cerebral hemorrhage in rabbits by time-difference magnetic inductive phase shift spectroscopy

[Magnetic induced phase shift detection system based on a novel sensor for cerebral hemorrhage]

The main magnetic field, generated by the excitation coil of the magnetic induction phase shift technology detection system, is mostly dispersed field with small field strength, and the offset effect needs to be further improved, which makes the detection signal weak and the detection system difficult to achieve quantitative detection, thus the technology is rarely used in vivo experiments and clinical trials. In order to improve problems mentioned above, a new Helmholtz birdcage sensor was designed. Stimulation experiment was carried out to analyze the main magnetic field in aspects of intensity and magnetic distribution, then different bleeding volume and bleeding rates experiments were conducted to compared with traditional sensors. The results showed that magnetic field intensity in detection region was 2.5 times than that of traditional sensors, cancellation effect of the main magnetic field was achieved, the mean value of phase difference of 10 mL rabbit blood was (-3.34 ± 0.21)°, and exponential fitting adjusted R 2 between phase difference and bleeding volumes and bleeding rates were both 0.99. The proposed Helmholtz birdcage sensor has a uniform magnetic field with a higher field strength, enable more accurate quantification of hemorrhage and monitored change of bleeding rates, providing significance in magnetic induced technology research for cerebral hemorrhage detection.

A Magnetic Resonance-Relaxometry-Based Technique to Identify Blood Products in Brain Parenchyma: An Experimental Study on a Rabbit Model

Magnetic resonance relaxometry is a quantitative technique that estimates T1/T2 tissue relaxation times. This has been proven to increase MRI diagnostic accuracy of brain disorders in human medicine. However, literature in the veterinary field is scarce. In this work, a T1 and T2-based relaxometry approach has been developed. The aim is to investigate its performance in characterizing subtle brain lesions obtained with autologous blood injections in rabbits. This study was performed with a low-field scanner, typically present in veterinary clinics. The approach consisted of a semi-automatic hierarchical classification of different regions, selected from a T2 map. The classification was driven according to the relaxometry properties extracted from a set of regions selected by the radiologist to compare the suspected lesion with the healthy parenchyma. Histopathological analyses were performed to estimate the performance of the proposed classifier through receiver operating characteristic curve analyses. The classifier resulted in moderate accuracy in terms of lesion characterization.

A noninvasive and comprehensive method for continuous assessment of cerebral blood flow pulsation based on magnetic induction phase shift

Cerebral blood flow (CBF) monitoring is of great significance for treating and preventing strokes. However, there has not been a fully accepted method targeting continuous assessment in clinical practice. In this work, we built a noninvasive continuous assessment system for cerebral blood flow pulsation (CBFP) that is based on magnetic induction phase shift (MIPS) technology and designed a physical model of the middle cerebral artery (MCA). Physical experiments were carried out through different simulations of CBF states. Four healthy volunteers were enrolled to perform the MIPS and ECG synchronously monitoring trials. Then, the components of MIPS related to the blood supply level and CBFP were investigated by signal analysis in time and frequency domain, wavelet decomposition and band-pass filtering. The results show that the time-domain baseline of MIPS increases with blood supply level. A pulse signal was identified in the spectrum (0.2-2 Hz in 200-2,000 ml/h groups, respectively) of MIPS when the simulated blood flow rate was not zero. The pulsation frequency with different simulated blood flow rates is the same as the squeezing frequency of the feeding pump. Similar to pulse waves, the MIPS signals on four healthy volunteers all had periodic change trends with obvious peaks and valleys. Its frequency is close to that of the ECG signal and there is a certain time delay between them. These results indicate that the CBFP component can effectively be extracted from MIPS, through which different blood supply levels can be distinguished. This method has the potential to become a new solution for non-invasive and comprehensive monitoring of CBFP.

Atorvastatin suppresses NLRP3 inflammasome activation in intracerebral hemorrhage via TLR4- and MyD88-dependent pathways

Intracerebral hemorrhage (ICH) is a common neurological condition that causes severe disability and even death. Even though the mechanism is not clear, increasing evidence shows the efficacy of atorvastatin on treating ICH. In this study, we examined the impact of atorvastatin on the NOD-like receptor protein 3 (NLRP3) inflammasome and inflammatory pathways following ICH. Mouse models of ICH were established by collagenase injection in adult C57BL/6 mice. IHC mice received atorvastatin treatment 2 h after hematoma establishment. First, the changes of glial cells and neurons in the brains of ICH patients and mice were detected by immunohistochemistry and western blotting. Second, the molecular mechanisms underlying the microglial activation and neuronal loss were evaluated after the application of atorvastatin. Finally, the behavioral deficits of ICH mice without or with the treatment of atorvastatin were determined by neurological defect scores. The results demonstrated that atorvastatin significantly deactivated glial cells by reducing the expression of glial fibrillary acidic protein (GFAP), Ionized calcium binding adapter molecule 1 (Iba1), tumor necrosis factor (TNF)-α, and interleukin (IL)-6 in ICH model mice. For inflammasomes, atorvastatin also showed its efficacy by decreasing the expression of NLRP3, cleaved caspase-1, and IL-1β in ICH mice. Moreover, atorvastatin markedly inhibited the upregulation of toll-like receptor 4 (TLR4) and myeloid differentiation factor 88 (MyD88), which indicated deactivation of NLRP3 inflammasomes. By inhibiting the activities of inflammasomes in glial cells, neuronal loss was partially prevented by suppressing the apoptosis in the brains of ICH mice, protecting them from neurological defects.

An amplitude-based characteristic parameter extraction algorithm for cerebral edema detection based on electromagnetic induction

Background

Cerebral edema is a common condition secondary to any type of neurological injury. The early diagnosis and monitoring of cerebral edema is of great importance to improve the prognosis. In this article, a flexible conformal electromagnetic two-coil sensor was employed as the electromagnetic induction sensor, associated with a vector network analyzer (VNA) for signal generation and receiving. Measurement of amplitude data over the frequency range of 1–100 MHz is conducted to evaluate the changes in cerebral edema. We proposed an Amplitude-based Characteristic Parameter Extraction (Ab-CPE) algorithm for multi-frequency characteristic analysis over the frequency range of 1–100 MHz and investigated its performance in electromagnetic induction-based cerebral edema detection and distinction of its acute/chronic phase. Fourteen rabbits were enrolled to establish cerebral edema model and the 24 h real-time monitoring experiments were carried out for algorithm verification.

Results

The proposed Ab-CPE algorithm was able to detect cerebral edema with a sensitivity of 94.1% and specificity of 95.4%. Also, in the early stage, it can detect cerebral edema with a sensitivity of 85.0% and specificity of 87.5%. Moreover, the Ab-CPE algorithm was able to distinguish between acute and chronic phase of cerebral edema with a sensitivity of 85.0% and specificity of 91.0%.

Conclusion

The proposed Ab-CPE algorithm is suitable for multi-frequency characteristic analysis. Combined with this algorithm, the electromagnetic induction method has an excellent performance on the detection and monitoring of cerebral edema.

Twenty-four-hour real-time continuous monitoring of acute focal cerebral ischemia in rabbits based on magnetic inductive phase shift

BACKGROUND

As a serious clinical disease, ischemic stroke is usually detected through magnetic resonance imaging and computed tomography. In this study, a noninvasive, non-contact, real-time continuous monitoring system was constructed on the basis of magnetic induction phase shift (MIPS) technology. The "thrombin induction method", which conformed to the clinical pathological development process of ischemic stroke, was used to construct an acute focal cerebral ischemia model of rabbits. In the MIPS measurement, a "symmetric cancellation-type" magnetic induction sensor was used to improve the sensitivity and antijamming capability of phase detection.

METHODS

A 24-h MIPS monitoring experiment was carried out on 15 rabbits (10 in the experimental group and five in the control group). Brain tissues were taken from seven rabbits for the 2% triphenyl tetrazolium chloride staining and verification of the animal model.

RESULTS

The nonparametric independent-sample Wilcoxon rank sum test showed significant differences (p < 0.05) between the experimental group and the control group in MIPS. Results showed that the rabbit MIPS presented a declining trend at first and then an increasing trend in the experimental group, which may reflect the pathological development process of cerebral ischemic stroke. Moreover, TTC staining results showed that the focal cerebral infarction area increased with the development of time CONCLUSIONS: Our experimental study indicated that the MIPS technology has a potential ability of differentiating the development process of cytotoxic edema from that of vasogenic edema, both of which are caused by cerebral ischemia.

Noninvasive real-time detection of cerebral blood perfusion in hemorrhagic shock rabbits based on whole-brain magnetic induction phase shift: an experimental study

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.

A noninvasive flexible conformal sensor for accurate real-time monitoring of local cerebral edema based on electromagnetic induction

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.

A cerebral edema monitoring system based on a new excitation source

BACKGROUND

Real-time clinical monitoring of cerebral edema (CE) is of great importance and requires continuously improved and optimized measurement hardware.

METHODS

A new excitation source with higher frequency stability and wide output power range is presented in this work. The proposed excitation source is small in size and easy to integrate. The output power range of excitation signal used is 1.5 ∼ 33 dBm with a reference signal of 9 ∼ 11 dBm, and the phase shift stability of the excitation signal and reference signal reach 10-7 within 20 min.

RESULTS

When normal saline (0.9%, 10 mL, 20 mL, 30 mL, 40 mL, and 50 mL) is injected into a human head phantom model, the magnetic induction phase shift (MIPS) changes from 252.78 ± 7.61 degrees to 252.40 ± 7.77 degrees. The MIPS signal shows a downward trend with increasing volume, indicating that MIPS can reflect the volume change of the measured object. Moreover, a more dramatic trend is visible when the solution volume increases from 0 to 10 mL and from 40 to 50 mL. This occurs where the volume increment is closer to the upper and lower sides of the over-ear sensor, where the magnetic field is strongest.

CONCLUSION

The phantom simulation experiments illustrate that the proposed MIPS detection system based on a signal source can detect the real-time progress of CE. Advantages of low cost, high precision, and high sensitivity endow this system with excellent application prospects.

An experimental study on the early diagnosis of traumatic brain injury in rabbits based on a noncontact and portable system

Closed cerebral hemorrhage (CCH) is a common symptom in traumatic brain injury (TBI) patients who suffer intracranial hemorrhage with the dura mater remaining intact. The diagnosis of CCH patients prior to hospitalization and in the early stage of the disease can help patients get earlier treatments that improve outcomes. In this study, a noncontact, portable system for early TBI-induced CCH detection was constructed that measures the magnetic induction phase shift (MIPS), which is associated with the mean brain conductivity caused by the ratio between the liquid (blood/CSF and the intracranial tissues) change. To evaluate the performance of this system, a rabbit CCH model with two severity levels was established based on the horizontal biological impactor BIM-II, whose feasibility was verified by computed tomography images of three sections and three serial slices. There were two groups involved in the experiments (group 1 with 10 TBI rabbits were simulated by hammer hit with air pressure of 600 kPa by BIM-II and group 2 with 10 TBI rabbits were simulated with 650 kPa). The MIPS values of the two groups were obtained within 30 min before and after injury. In group 1, the MIPS values showed a constant downward trend with a minimum value of −11.17 ± 2.91° at the 30th min after 600 kPa impact by BIM-II. After the 650 kPa impact, the MIPS values in group 2 showed a constant downward trend until the 25th min, with a minimum value of −16.81 ± 2.10°. Unlike group 1, the MIPS values showed an upward trend after that point. Before the injury, the MIPS values in both group 1 and group 2 did not obviously change within the 30 min measurement. Using a support vector machine at the same time point after injury, the classification accuracy of the two types of severity was shown to be beyond 90%. Combined with CCH pathological mechanisms, this system can not only achieve the detection of early functional changes in CCH but can also distinguish different severities of CCH.

Experimental study on the detection of cerebral hemorrhage in rabbits based on broadband antenna technology

Hematoma enlargement often occurs in patients with spontaneous intracerebral hemorrhage (ICH), so it is necessary to monitor the amount of intracranial hemorrhage in patients after admission. At present, the commonly used intracranial pressure (ICP) method has the disadvantages of trauma and infection, and the Computer Tomography (CT) method cannot achieve continuous monitoring. So it is urgent to develop a non-contact and non-invasive method for continuous monitoring of cerebral hemorrhage. The dielectric properties of blood are different from those of brain tissue, so the hematoma will affect the amplitude and phase of the electromagnetic waves passing through the head. A microstrip antenna was designed to construct the detection system for cerebral hemorrhage. Based on the animal model of acute cerebral hemorrhage, the detecting experiment was carried out on thirteen rabbits. Each rabbit had three bleeding states: 1, 2, and 3 ml, which represented the severity of cerebral hemorrhage. According to the measured data of high dimension and small sample, the support vector machine (SVM) algorithm was used to assess the severity of cerebral hemorrhage. According to simulation results, the antenna's forward radiation was 5 dB larger than the backward radiation, which ensured the antenna being not affected by external signals during the measurement. According to test results, the -10 dB workband of the antenna was 1.55-2.05 GHz and the frequency range of the transmission parameters S₂₁ above -30 dB is 1.2 - 3 GHz. In the animal experiment, the phase difference of Transmission coefficient S₂₁ was gradually increased with the increase of bleeding volume. Through the classification of 39 bleeding states of the 13 rabbits, the total accuracy was about 77%. Through animal experiments, the feasibility of detection method has been proved. But the classification accuracy need to be further improved. The detection system is based on broadband antenna has the potential to realize non-contact, non-invasive and continuous monitoring for cerebral hemorrhage.

An experimental study of pulse wave measurements with magnetic induction phase shift method

BACKGROUND

Pulse wave monitoring is widely used to evaluate the physiological and pathological states of the cardiovascular system.

OBJECTIVE

High-sensitivity ring sensors were designed, and a simultaneous acquisition platform based on National Instruments T-Clock technology (NI-TCLK) was used to achieve simultaneous pulse detection using both the traditional method and the magnetic induction phase shift (MIPS) method.

METHODS

The excitation signal had a frequency of approximately 10.7 MHz and power of about 20 dBm. A total of 30 volunteers (adults, aged 20-30 y) were selected to corroborate the feasibility of our measurement system. The subjects wore the proposed sensor on their right-hand forefingers and for reference, the piezoelectric pulse sensor on the left-hand forefinger. The pulse waves of these 30 subjects were measured over 2 min each.

RESULTS

The phase shift of the magnetic induction detection signal ranged from 0.6-0.8 degrees. Comparison of detection results for the same subject between the two methods showed that the pulse rate measured by magnetic induction exhibited fewer deviations and better stability than the traditional method. In addition, spectral analysis indicated that the pulse frequencies obtained using the 2 methods were concentrated between 1-3 Hz and were regular in the 1.5 Hz frequency region.

CONCLUSIONS

These results prove that the magnetic induction pulse wave can be used to accurately measure pulse wave features.

Investigating the Relationship between Cerebrospinal Fluid and Magnetic Induction Phase Shift in Rabbit Intracerebral hematoma expansion Monitoring by MRI

In a prior study of intracerebral hemorrhage monitoring using magnetic induction phase shift (MIPS), we found that MIPS signal changes occurred prior to those seen with intracranial pressure. However, the characteristic MIPS alert is not yet fully explained. Combining the brain physiology and MIPS theory, we propose that cerebrospinal fluid (CSF) may be the primary factor that leads to hematoma expansion being alerted by MIPS earlier than with intracranial pressure monitoring. This paper investigates the relationship between CSF and MIPS in monitoring of rabbit intracerebral hemorrhage models, which is based on the MIPS measurements data, the quantified data on CSF from medical images and the amount of injected blood in the rabbit intracerebral hemorrhage model. In the investigated results, a R value of 0.792 with a significance of 0.019 is observed between the MIPS and CSF, which is closer than MIPS and injected blood. Before the reversal point of MIPS, CSF is the leading factor in MIPS signal changing in an early hematoma expansion stage. Under CSF compensation, CSF reduction compensates for hematoma expansion in the brain to keep intracranial pressure stable. MIPS decrease results from the reducing CSF volume. This enables MIPS to detect hematoma expansion earlier than intracranial pressure.

Twenty-Four-Hour Real-Time Continuous Monitoring of Cerebral Edema in Rabbits Based on a Noninvasive and Noncontact System of Magnetic Induction

Cerebral edema is a common disease, secondary to craniocerebral injury, and real-time continuous monitoring of cerebral edema is crucial for treating patients after traumatic brain injury. This work established a noninvasive and noncontact system by monitoring the magnetic induction phase shift (MIPS) which is associated with brain tissue conductivity. Sixteen rabbits (experimental group n = 10, control group, n = 6) were used to perform a 24 h MIPS and intracranial pressure (ICP) simultaneously monitored experimental study. For the experimental group, after the establishment of epidural freeze-induced cerebral edema models, the MIPS presented a downward trend within 24 h, with a change magnitude of −13.1121 ± 2.3953°; the ICP presented an upward trend within 24 h, with a change magnitude of 12–41 mmHg. The ICP was negatively correlated with the MIPS. In the control group, the MIPS change amplitude was −0.87795 ± 1.5146 without obvious changes; the ICP fluctuated only slightly at the initial value of 12 mmHg. MIPS had a more sensitive performance than ICP in the early stage of cerebral edema. These results showed that this system is basically capable of monitoring gradual increases in the cerebral edema solution volume. To some extent, the MIPS has the potential to reflect the ICP changes.

Construction of a Cerebral Hemorrhage Test System Operated in Real-time

The real-time monitoring and evaluation of the severity and progression of cerebral hemorrhage is essential to its intensive care and its successful emergency treatment. Based on magnetic induction phase shift technology combined with a PCI data acquisition system and LabVIEW software, this study established a real-time monitoring system for cerebral hemorrhage. To test and evaluate the performance of the system, the authors performed resolution conductivity experiments, salted water simulation experiments and cerebral hemorrhage experiments in rabbits and found that when the conductivity difference was 0.73 S/m, the phase difference was 13.196°. The phase difference change value was positively proportional to the volume of saline water, and the conductivity value was positively related to the phase difference of liquid under the same volume conditions. After injecting 3 mL blood into six rabbits, the average change in the blood phase difference was −2.03783 ± 0.22505°, and it was positively proportional to the volume of blood, which was consistent with the theoretical results. The results show that the system can monitor the progressive development of cerebral hemorrhage in real-time and has the advantages of low cost, small size, high phase accuracy, and good clinical application potentiality.

Design and Experimental Evaluation of a Non-Invasive Microwave Head Imaging System for Intracranial Haemorrhage Detection

An intracranial haemorrhage is a life threatening medical emergency, yet only a fraction of the patients receive treatment in time, primarily due to the transport delay in accessing diagnostic equipment in hospitals such as Magnetic Resonance Imaging or Computed Tomography. A mono-static microwave head imaging system that can be carried in an ambulance for the detection and localization of intracranial haemorrhage is presented. The system employs a single ultra-wideband antenna as sensing element to transmit signals in low microwave frequencies towards the head and capture backscattered signals. The compact and low-profile antenna provides stable directional radiation patterns over the operating bandwidth in both near and far-fields. Numerical analysis of the head imaging system with a realistic head model in various situations is performed to realize the scattering mechanism of haemorrhage. A modified delay-and-summation back-projection algorithm, which includes effects of surface waves and a distance-dependent effective permittivity model, is proposed for signal and image post-processing. The efficacy of the automated head imaging system is evaluated using a 3D-printed human head phantom with frequency dispersive dielectric properties including emulated haemorrhages with different sizes located at different depths. Scattered signals are acquired with a compact transceiver in a mono-static circular scanning profile. The reconstructed images demonstrate that the system is capable of detecting haemorrhages as small as 1 cm³. While quantitative analyses reveal that the quality of images gradually degrades with the increase of the haemorrhage’s depth due to the reduction of signal penetration inside the head; rigorous statistical analysis suggests that substantial improvement in image quality can be obtained by increasing the data samples collected around the head. The proposed head imaging prototype along with the processing algorithm demonstrates its feasibility for potential use in ambulances as an effective and low cost diagnostic tool to assure timely triaging of intracranial hemorrhage patients.