13 research outputs found

    The Science Performance of JWST as Characterized in Commissioning

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    This paper characterizes the actual science performance of the James Webb Space Telescope (JWST), as determined from the six month commissioning period. We summarize the performance of the spacecraft, telescope, science instruments, and ground system, with an emphasis on differences from pre-launch expectations. Commissioning has made clear that JWST is fully capable of achieving the discoveries for which it was built. Moreover, almost across the board, the science performance of JWST is better than expected; in most cases, JWST will go deeper faster than expected. The telescope and instrument suite have demonstrated the sensitivity, stability, image quality, and spectral range that are necessary to transform our understanding of the cosmos through observations spanning from near-earth asteroids to the most distant galaxies.Comment: 5th version as accepted to PASP; 31 pages, 18 figures; https://iopscience.iop.org/article/10.1088/1538-3873/acb29

    Application of a Novel Headrest System for Odontoid Screw Fixation: Technical Note

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    The authors describe a unique headholder device adapted to facilitate the placement of anterior odontoid screws. The patient\u27s head is affixed in the headholder equipped with an articulating arm that can be placed in a paramedian fashion. This configuration rigidly fixates the head and provides an unencumbered open-mouth view of the odontoid using radiographic images, thus making screw placement easier

    Intraoperative ISO-C C-Arm Navigation in Cervical Spinal Surgery: Review of the First 52 Cases

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    STUDY DESIGN: Fifty-two study participants underwent cervical spine surgery using intraoperative Iso-C imaging with or without spinal navigation. OBJECTIVES: To evaluate prospectively the feasibility, advantages, limitations, and applications of Iso-C in cervical spine surgery. SUMMARY OF BACKGROUND DATA: Existing stereotactic spinal navigational systems images must be acquired before surgery and typically require cumbersome point-to-point registration. Intraoperative computed tomography (CT) and magnetic resonance imaging (MRI) provide real-time information but can restrict access to the patient, preclude the use of traditional operating room tables, and are time-consuming. The Iso-C allows quick, CT-quality, real-time data acquisition without restricting access to the patient. The data acquired can be automatically transferred to navigational systems with the immediate ability to navigate for anterior or posterior cervical spine procedures. METHODS: High-resolution isotropic three-dimensional data sets were acquired using the Iso-C intraoperative fluoroscopy in 52 cervical spine cases. In 30 cases, the data were imported automatically to the StealthStation Treon to support neuronavigation. In 22 cases, a postprocedural intraoperative CT was obtained with the Iso-C primarily to assess the extent of osseous decompression and/or the accuracy of implants or instrumentation. In most cases, a postoperative high-resolution CT image was obtained and compared with the Iso-C data. RESULTS: Successful automated registration suitable for navigation was attained for all anterior and posterior cervical spinal cases. The postprocedural intraoperative Iso-C data were 100% concordant with those of postoperative high-resolution CT as determined by a blinded neuroradiologist. CONCLUSIONS: Iso-C intraoperative fluoroscopy is an accurate and rapid way to perform CT-quality image-guided navigation in cervical spinal surgery. In most cases, it obviates the need for postoperative imaging

    Biomechanical Comparison of C1-2 Posterior Fixation Techniques.

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    OBJECT: In a nondestructive, repeated-measures in vitro flexibility experiment, the authors compared the acute stability of C1-2 after placement of C-1 lateral mass and C-2 pars interarticularis (LC1-PC2) instrumentation with that of C1-2 transarticular screw fixation. METHODS: The effect of C-1 laminectomy and C1-2 interspinous cable/graft fixation on LC1-PC2 stability was studied. Screw pullout strengths were also compared. Seven human cadaveric occiput-C3 specimens were loaded nondestructively with pure moments while measuring nonconstrained atlantoaxial motion. Specimens were tested with graft alone, LC1-PC2 alone, LC1-PC2 combined with C-1 laminectomy, and graft-augmented LC1-PC2. Interspinous cable/graft fixation significantly enhanced LC1-PC2 stability during extension. After C-1 laminectomy, the LC1-PC2 construct allowed increased motion during flexion and extension. There was no significant difference in lax zone or range of motion between LC1-PC2 fixation and transarticular screw fixation, but graft-assisted transarticular screws yielded a significantly smaller stiff zone during extension. The difference in pullout resistance between C-1 lateral mass screws and C-2 pars interarticularis screws was insignificant. The LC1-PC2 region restricted motion to within the normal range during all loading modes. Atlantal laminectomy reduced LC1-PC2 stability during flexion and extension. CONCLUSIONS: The instrumentation-augmented LC1-PC2 construct performed biomechanically similarly to the C1-2 transarticular screw fixation. The LC1-PC2 construct resisted flexion, lateral bending, and axial rotation well. The weakness of the LC1-PC2 fixation in resisting extension can be overcome by adding an interspinous graft to the construct
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