RESUMO
PURPOSE: Augmented reality-based image overlay of virtual bony spine anatomy can be projected onto real spinal anatomy using computer tomography-generated DICOM images acquired intraoperatively. The aim of the study was to develop a technique and assess the accuracy and feasibility of lumbar vertebrae pedicle instrumentation using augmented reality-assisted surgical navigation. SUBJECTS AND METHODS: An augmented reality and artificial intelligence (ARAI)-assisted surgical navigation system was developed. The system consists of a display system which hovers over the surgical field and projects three-dimensional (3D) medical images corresponding with the patient's anatomy. The system was registered to the cadaveric spine using an optical tracker and arrays with reflective markers. The virtual image overlay from the ARAI system was compared to 3D generated images from intraoperative scans and used to percutaneously navigate a probe to the cortex at the corresponding pedicle starting point. Intraoperative scan was used to confirm the probe position. Virtual probe placement was compared to the actual probe position in the bone to determine the accuracy of the navigation system. RESULTS: Four cadaveric thoracolumbar spines were used. The navigated probes were correctly placed in all attempted levels (n = 24 levels), defined as Zdichavsky type 1a, Ravi type I, and Gertzbein type 0. The virtual overlay image corresponded to the 3D generated image in all the tested levels. CONCLUSIONS: The ARAI surgical navigation system correctly and accurately identified the starting points at all the attempted levels. The virtual anatomy image overlay precisely corresponded to the actual anatomy in all the tested scenarios. This technology may lead more uniform outcomes between surgeons and decrease minimally invasive spine surgery learning curves.
RESUMO
Object categorization during ambiguous sensory stimulation generally depends on the activity of extrastriate sensory areas as well as top-down information. Both reflect internal representations of prototypical object knowledge against which incoming sensory information is compared. However, besides these general mechanisms, individuals might differ in their readiness to impose internal representations onto incoming ambiguous information. These individual differences might be based on what was referred to as "Schema Instantiation Threshold" (SIT; Lewicki et al. [1992]: Am Pshycol 47:796-801), defining a continuum from very rapid (low threshold) to a rather controlled application of internal representations (high threshold). We collected fMRI scans while subjects with low SIT ("internal encoders") and subjects with high SIT ("external encoders") made gender categorizations of ambiguous facial images. Internal encoders made faster gender decisions during high sensory ambiguity, showed higher fusiform activity, and had faster BOLD responses in the fusiform (FFA) and occipital face area (OFA) indicating a faster and stronger application of face-gender representations due to a low SIT threshold. External encoders made slower gender decisions and showed increased medial frontal activity, indicating a more controlled strategy during gender categorizations and increased decisional uncertainties. Internal encoders showed higher functional connectivity of the orbito-frontal cortex (OFC) to seed activity in the FFA which might indicate both more readily generated predictive classificatory guesses and the subjective impressions of accurate classifications. Taken together, an "internal encoding style" is characterized by the fast, unsupervised and unverified application of primary object representations, whereas the opposite seems evident for subjects with an "external encoding style".
