Modified RTK-GNSS for Challenging Environments.

Real-Time Kinematic Global Navigation Satellite System (RTK-GNSS) is currently the premier technique for achieving centimeter-level accuracy quickly and easily. However, the robustness of RTK-GNSS diminishes in challenging environments due to severe multipath effects and a limited number of available GNSS signals. This is a pressing issue, especially for GNSS users in the navigation industry. This paper proposes and evaluates several methodologies designed to overcome these issues by enhancing the availability and reliability of RTK-GNSS solutions in urban environments. Our novel approach involves the integration of conventional methods with a new technique that leverages surplus satellites-those not initially used for positioning-to more reliably detect incorrect fix solutions. We conducted three tests in densely built-up areas within the Tokyo region. The results demonstrate that our approach not only surpasses the fix rate of the latest commercial receivers and a popular open-source RTK-GNSS program but also improves positional reliability to levels comparable to or exceeding those of the aforementioned commercial technology.

GNSS NLOS Signal Classification Based on Machine Learning and Pseudorange Residual Check.

Global navigation satellite system (GNSS) positioning has recently garnered attention for autonomous driving, machine control, and construction sites. With the development of low-cost multi-GNSS receivers and the advent of new types of GNSS, such as Japan's Quasi-Zenith Satellite System, the potential of GNSS positioning has increased. New types of GNSS directly increase the number of line-of-sight (LOS) signals in dense urban areas and improve positioning accuracy. However, GNSS receivers can observe both LOS and non-line-of-sight (NLOS) signals in dense urban areas, and more NLOS signals are observed under static conditions than under dynamic conditions. The classification of LOS and NLOS signals is important, and various methods have been proposed, such as C/N0, using three-dimensional maps, fish-eye view, and GNSS/inertial navigation system integration. Multipath detection based on machine learning has also been reported in recent years. In this study, we propose a method for detecting NLOS signals using a support vector machine (SVM) classifier modeled with unique features that are calculated by receiver independent exchange format-based information and GNSS pseudorange residual check. We found that using both the SVM classifier and GNSS pseudorange residual check effectively reduced the error due to NLOS signals. Several static tests were conducted near high-rise buildings that are likely to receive some NLOS signals in downtown Tokyo. For all static tests, the percentage of positioning errors within 10 m in the horizontal positioning error was improved by >80% by detecting and eliminating satellites receiving NLOS signals.

Preliminary Clinical Surgical Experience with Temporary Simultaneous Use of an Endoscope during Exoscopic Neurosurgery: An Observational Study.

The use of an endoscope in exoscopic transcranial neurosurgery for skull-base lesions has not yet been investigated. Thus, this study aimed to investigate the advantages, disadvantages, and safety of "simultaneous temporary use of an endoscope during exoscopic surgery" (exo-endoscopic surgery (EES)). Consecutive exo-endoscopic surgeries performed by experienced neurosurgeons and assistants were analyzed. Surgical complications and time were compared with previous consecutive microsurgeries performed by the same surgeon. A questionnaire survey was conducted on 16 neurosurgeons with experience in both "temporary simultaneous use of endoscope during microscopic surgery" (micro-endoscopic surgery (MES)) and EES. EES was performed in 18 of 76 exoscopic surgeries, including tumor removal (n = 10), aneurysm clipping (n = 5), and others (n = 3). There were no significant differences in operative time, anesthesia time, or complications from microsurgery by the same operator. According to the questionnaire survey results, compared with MES, EES had a wider field of view due to its lack of an eyepiece, was easier when loading and unloading instruments into and out of the surgical field, and was more suitable for the simultaneous observation of two fields of view. Overall, 79.2% of surgeons indicated that EES may be better suited than MES to simultaneously observe two fields of view.

Suspected Low-Pressure Hydrocephalus Caused by Spinal Drainage after Subarachnoid Hemorrhage.

Hydrocephalus induced by low cerebrospinal fluid (CSF) pressure is extremely rare and sporadically reported. Subarachnoid hemorrhage, head trauma, and spinal drainage were reported to be causative factors for surgical treatment. A 33-year-old man with subarachnoid hemorrhage caused by right vertebral artery aneurysm rupture developed headache. Trapping surgery was performed, and a spinal drain was inserted from L4/5 for subarachnoid hemorrhage washout. On postoperative day 3, subdural fluid accumulation had increased at the posterior fossa craniotomy site and the cerebellar sulci had narrowed; the ventricles were slightly enlarged. The patient reported headache during head elevation. Low-pressure hydrocephalus (LPH) was suspected. After the spinal drain was removed, headache resolved, and cerebral ventriculomegaly disappeared. The subsequent clinical course was good. The patient was discharged 3 weeks after surgery. LPH is a rare disease caused by various factors and is treated by correcting liquorrhea or overdrainage, when present. Otherwise, drainage at negative CSF pressure is necessary. The symptoms and image findings for LPH are similar to those for intracranial hypertension and normal-pressure hydrocephalus. This report describes a suspected case of LPH caused by spinal drainage after subarachnoid hemorrhage and reviews the literature.

Severe Aneurysmal Subarachnoid Hemorrhage after Warning Headache during Pregnancy: A Case Report.

BACKGROUND: Aneurysmal subarachnoid hemorrhage is a rare but important cause of maternal death during pregnancy. CASE DESCRIPTION: A 34-year-old primigravida (31 weeks of pregnancy) with acute headache but no neurological deficits or neck stiffness was prescribed medication and returned home. Four weeks later she presented with severe headache and consciousness disturbance. She was admitted to our hospital, where she fell into a deep coma. Brain CT and three-dimensional CT angiography showed subarachnoid hemorrhage and a 5-mm right internal carotid-posterior communicating artery aneurysm. Fetal heart rate was 60 beats per minute. Emergent cesarean section and surgical clipping were performed. Intraoperative examination revealed that the aneurysm originated at the right posterior communicating artery. There were no postoperative neurological focal deficits. On postoperative day 13 she developed delayed cerebral ischemia of the right temporo-parieto-occipital lobe. She was discharged home 36 days after surgery with left hemianopsia. The infant was free of complications and was discharged at age 17 days. CONCLUSIONS: A pregnant woman with severe headache should undergo brain CT or magnetic resonance imaging to rule out subarachnoid hemorrhage.

Preliminary Clinical Microneurosurgical Experience With the 4K3-Dimensional Microvideoscope (ORBEYE) System for Microneurological Surgery: Observation Study.

BACKGROUND: The exoscope has been reported as a novel neurosurgical instrumentation in clinical practice. OBJECTIVE: To investigate the possibility that ORBEYE (OE), a novel instrument that excludes eyepiece lenses and allows for microsurgery by observation of the 4K3D monitor, could replace microscopes. METHODS: We report 22 clinical cases by 5 experienced neurosurgeons and the comparative results of training 10 residents. An observation study with questionnaire survey was conducted on usability. Twelve items including image quality, eyestrain, and function of the arm were evaluated. RESULTS: The following 22 clinical procedures were conducted: surgery for intracranial hemorrhage (n = 2) and brain tumor (n = 8), laminectomy (n = 3), aneurysm clipping (n = 3), vascular anastomosis (n = 2), carotid endarterectomy (n = 2), and nerve decompression (n = 1). No complications were observed. The fluorescent study, including indocyanine-green and 5-aminolevunic acid, allowed for clear depiction on the 4K monitor. The surgeon could operate in a comfortable posture. Similar to the microscope, it was possible to change the optical and viewing axes with the OE, but the OE was switched to the microscope or endoscope in hematoma removal and pituitary surgery. Residents judged that eyestrain was strong (P = .0096). Experienced neurosurgeons acting as assistants judged that the scope arm's range of movement was narrow (P = .0204). Sixty percent of residents judged that the OE was superior to the microscope. CONCLUSION: Although based on limited experience, it was not possible to substitute the microscope with the OE in all operations; however, the OE surpasses the microscope in terms of ergonomic features.