ABSTRACT
High-dynamic-range integrated magnetometers demonstrate extensive potential applications in fields involving complex and changing magnetic fields. Among them, Diamond Nitrogen Vacancy Color Core Magnetometer has outstanding performance in wide-range and high-precision magnetic field measurement based on its inherent high spatial resolution, high sensitivity and other characteristics. Therefore, an innovative frequency-tracking scheme is proposed in this study, which continuously monitors the resonant frequency shift of the NV color center induced by a time-varying magnetic field and feeds it back to the microwave source. This scheme successfully expands the dynamic range to 6.4 mT, approximately 34 times the intrinsic dynamic range of the diamond nitrogen-vacancy (NV) center. Additionally, it achieves efficient detection of rapidly changing magnetic field signals at a rate of 0.038 T/s.
ABSTRACT
Nitrogen-vacancy (NV) centers in diamonds are promising solid-state magnetic sensors with potential applications in power systems, geomagnetic navigation, and diamond NV color center current transformers, in which both high bandwidth and high magnetic field resolution are required. The wide bandwidth requirement often necessitates high laser power, but this induces significant laser fluctuation noise that affects the detection magnetic field resolution severely. Therefore, enhancement of the magnetic field resolution of wide-bandwidth NV center magnetic sensors is highly important because of the reciprocal effects of the bandwidth and magnetic field resolution. In this article, we develop a common mode rejection (CMR) model to eliminate the laser noise effectively. The simulation results show that the noise level of the light-detected magnetic resonance signal is significantly reduced by a factor of 6.2 after applying the CMR technique. After optimization of the laser power and modulation frequency parameters, the optimal system bandwidth was found to be 75 Hz. Simultaneously, the system's detection magnetic field resolution was enhanced significantly, increasing from 4.49 nT/Hz1/2 to 790.8 pT/Hz1/2, which represents an improvement of nearly 5.7 times. This wide-bandwidth, high-magnetic field resolution NV color center magnetic sensor will have applications including power systems, geomagnetic navigation, and diamond NV color center current transformers.
ABSTRACT
BACKGROUND: Spondylodiscitis is an unusual infectious disease, which usually originates as a pathogenic infection of intervertebral discs and then spreads to neighboring vertebral bodies. The objective of this study is to evaluate percutaneous debridement and drainage using intraoperative CT-Guide in multilevel spondylodiscitis. METHODS: From January 2002 to May 2017, 23 patients with multilevel spondylodiscitis were treated with minimally invasive debridement and drainage procedures in our department. The clinical manifestations, evolution, and minimally invasive debridement and drainage treatment of this refractory vertebral infection were investigated. RESULTS: Of the enrolled patients, the operation time ranged from 30 minutes to 124 minutes every level with an average of 48 minutes. Intraoperative hemorrhage was minimal. The postoperative follow-up period ranged from 12 months to 6.5 years with an average of 3.7 years. There was no reactivation of infection in the treated vertebral segment during follow-up, but two patients with fungal spinal infection continued to progress by affecting adjacent segments prior to final resolution. According to the classification system of Macnab, one patient had a good outcome at the final follow-up, and the rest were excellent. CONCLUSIONS: Minimally invasive percutaneous debridement and irrigation using intraoperative CT-Guide is an effective minimally invasive method for the treatment of multilevel spondylodiscitis.
Subject(s)
Discitis , Spinal Fusion , Debridement , Discitis/diagnostic imaging , Discitis/surgery , Drainage , Follow-Up Studies , Humans , Lumbar Vertebrae , Minimally Invasive Surgical Procedures , Retrospective Studies , Tomography, X-Ray Computed , Treatment OutcomeABSTRACT
BACKGROUND: The aim of this study was to compare the clinical efficacy of endoscopic cervical spinal surgery with anterior cervical decompression and fusion (ACDF) in the treatment of cervical spondylotic myelopathy (CSM). METHODS: A total of forty-six CSM patients who were admitted to the Medical School of Chinese PLA and treated with endoscopic spine surgery or ACDF from January 2015 to June 2017 were collected. The patients were divided into the spinal endoscopy group and the ACDF group, according to the operation methods. The operation time, intraoperative blood loss and hospitalization stay of the two groups were recorded and compared. Japanese Orthopaedic Association (JOA) score before operation, three months, and one year after operation were recorded for intra-group and inter-group comparison. The improvement rates of JOA were compared between the two groups to evaluate the clinical efficacy. RESULTS: There were twenty-two cases in the spinal endoscopy group and twenty-four cases in the ACDF group. The mean operation lasting time, intraoperative blood loss and hospitalization stay in the spinal endoscopy group were significantly lower than those in the ACDF group (P<0.05). The postoperative JOA score of the two groups were significantly higher than those before the operation (P<0.05). There were no significant differences in the JOA score before operation, three months and one year after operation between the two groups (P>0.05). The improvement rates in the spinal endoscopy group were not significantly different compared to those in the ACDF group (P>0.05). There was no significant difference in the excellent rate (81.8% vs. 83.3%) between the spinal endoscopy group and the ACDF group (P>0.05). CONCLUSIONS: The short-term efficacy of spinal endoscopic surgery and ACDF was equal in the treatment of CSM. The spinal endoscopic surgery was significantly superior to ACDF in reducing the operation time, the intraoperative blood loss and the hospitalization stay.
