Experimental study on the detection of rabbit intracranial hemorrhage using four coil structures based on magnetic induction phase shift

Research on the measurement of intracranial hemorrhage in rabbits by a parallel-plate capacitor

Intracranial hemorrhage (ICH) carrying extremely high morbidity and mortality can only be detected by CT, MRI and other large equipment, which do not meet the requirements for bedside continuous monitoring and pre-hospital first aid. Since the biological tissues have different dielectric properties except the pure resistances, and the permittivity of blood is far larger than that of other brain tissues, here a new method was used to detect events of change at the blood/tissue volume ratio by measuring of the head permittivity. In this paper, we use a self-made parallel plate capacitor to detect the intracranial hemorrhage in rabbits by contactless capacitance measurement. The sensitivity of the parallel-plate capacitor was also evaluated by the physical solution measurement. The results of physical experiments show that the capacitor can distinguish between three solutions with different permittivity, and the capacitance increased with the increase of one solution between two plates. At the next step in the animal experiment, the capacitance changes caused by 2 ml blood injection into the rabbit brain were measured. The results of animal experiments show that the capacitance was almost unchanged before and after the blood injection, but increased with the increase of the blood injection volume. The increase of capacitance caused by blood injection was much larger than that before and after blood injection (P < 0.01). The experiments show that this method is feasible for the detection of intracranial hemorrhage in a non-invasive and contactless manner.

A non-invasive real-time monitoring system for cytotoxic brain edema in post ischemic stroke based on near-field coupling

BACKGROUND

As a common secondary pathophysiological process in postischemic stroke (IS), cytotoxic brain edema (CBE) is an independent factor leading to poor prognosis of patients. Near-field coupling (NFC) technology has some advantages such as non-invasive, non-contact, and unimpeded penetration of the skull. In theory, it can reflect the difference between normal and edema tissues through the near-field coupling phase shift (NFCPS) in the electromagnetic wave transmission trait.

METHODS

Combining NFC detection principle and computer programming, we established a high-performance real-time monitoring system with functions such as automatic setting of measurement parameters, data acquisition, real-time filtering and dynamic waveform display. To investigate the feasibility of this system to detect CBE, a saline simulation experiment and a 24-hour real-time monitoring experiment after middle cerebral artery occlusion (MCAO) in rats were carried out.

RESULTS

The results of the saline simulation experiment showed that the change of NFCPS was proportional to the increase of the simulated edema solution, and the variation range of NFCPS was more than 9∘ after 5 ml injection. In the 24-hour monitoring after MCAO, the NFCPS of the experimental group showed an overall downward trend over time an average change of -17.7868 ± 1.6325∘ and the change rate gradually decreased. The 24-hour NFCPS in the control group fluctuates slightly around the initial value, which has no obvious upward or downward trend.

CONCLUSION

The intragroup and intergroup difference statistical analysis shows that NFCPS can effectively distinguish different intracranial pathophysiological states after IS. This work provides sufficient evidence and a technical basis for using NFCPS to monitor CBE in the future.

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.