A Special Phase Detector for Magnetic Inductive Measurement of Cerebral Hemorrhage

Abstract

Cerebral hemorrhage is an important clinical problem that is often monitored and studied with expensive techniques, such as computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET). These devices are not readily available in economically underdeveloped regions of the world and in emergency departments and emergency zones. The magnetic inductive method is an emerging technology that may become a new tool to detect cerebral hemorrhage. In this study, a special phase detector (PD) was developed and used for cerebral hemorrhage detection with the magnetic inductive method. The performance indicated that the PD can achieve phase noise as low as 6 m° and a 4-hour phase drift as low as 30 m° at 21.4 MHz. The noise and drift decreased as the frequency decreased. The performance at 10.7 MHz was slightly better than that of other recently developed phase detection systems. To test the practicality of the system, the PD was used to detect the volume change in a self-made physical model of the brain. The measured phase shift was approximately proportional to the volume change of physiological saline inside the model. The change of the phase shift increased as the volume change and frequency increased. The results are in agreement with those from previous reports. To verify the feasibility of in vivo detection, an autologous blood injection model was established in rabbit brain. The results from the injection group showed a similar trend of increasing phase shift change with increasing injection volume. The average phase shift change induced by a 3-ml injection of blood was 0.502°±0.119°, which was much larger than that of the control group. The measurement system can distinguish a minimal cerebral hemorrhage volume of approximately 0.5 ml. All of the results demonstrated that the PD used with this method can detect cerebral hemorrhage.

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

“…Compared with previous detection systems that used single or limited numbers of frequencies [15,16,17,18,19,20,21], the system for cerebral edema established in this study can sweep within the entire frequency range (300 kHz–200 MHz) and can continuously observe the MIPS changes at an optimal sensitive frequency in real time with the monitoring software, improving the detection sensitivity greatly and realizing real-time continuous monitoring. The time for single MIPS collection was 0.628 s; this can fully meet the needs of 24 h real-time continuous monitoring for cerebral edema.…”

“…The time for single MIPS collection was 0.628 s; this can fully meet the needs of 24 h real-time continuous monitoring for cerebral edema. The cerebral edema two-coil sensor is different from the cerebral hemorrhage coil sensor used by Jin [17], but both of them obtain a similar MIPS trend because cerebral hemorrhage is often associated with cerebral edema [29]. This structure of the two-coil sensor may not be able to distinguish between cerebral edema and cerebral hemorrhage.…”

“…Therefore, our previous works were devoted to increasing the measurement sensitivity. In 2014, we established a magnetic induction phase detection system, which could achieve phase noise as low as 6 m° and a 4h phase drift as low as 30 m° at 21.4 MHz [17] and studied the MIPS of cerebral hemorrhage in rabbits with a single coil-coil [18]. Furthermore, we designed a symmetric cancellation-type sensor detection system based on the symmetry between the two brain hemispheres so as to offset the interference of the primary field and the perturbation field generated by other brain tissues [19].…”

Magnetic inductive phase shift: a new method to differentiate hemorrhagic stroke from ischemic stroke on rabbit

“…The operation procedure in this study is similar to those in previous research [19–21]. The rabbits were first anesthetized by injecting their ear vein with urethane (25%, 5 ml/kg).…”

“…The experimental results show that MIPS would gradually reduce as the amount of bleeding increased [19–21]. In this study, a novel coil structure was designed and used to measure the MIPS changes caused by hemorrhage or ischemia on rabbits.…”