To our knowledge, this is the first peer-reviewed report and evaluation of HMD-AR with superimposed 3D guidance utilizing CT for spinal pedicle guide placement for the purpose of cannulation without the use of fluoroscopy.
OBJECTIVE The objective of this study is to quantify the navigational accuracy of an advanced augmented reality (AR)–based guidance system for neurological surgery, biopsy, and/or other minimally invasive neurological surgical procedures. METHODS Five burr holes were drilled through a plastic cranium, and 5 optical fiducials (AprilTags) printed with CT-visible ink were placed on the frontal, temporal, and parietal bones of a human skull model. Three 0.5-mm-diameter targets were mounted in the interior of the skull on nylon posts near the level of the tentorium cerebelli and the pituitary fossa. The skull was filled with ballistic gelatin to simulate brain tissue. A CT scan was taken and virtual needle tracts were annotated on the preoperative 3D workstation for the combination of 3 targets and 5 access holes (15 target tracts). The resulting annotated study was uploaded to and launched by VisAR software operating on the HoloLens 2 holographic visor by viewing an encrypted, printed QR code assigned to the study by the preoperative workstation. The DICOM images were converted to 3D holograms and registered to the skull by alignment of the holographic fiducials with the AprilTags attached to the skull. Five volunteers, familiar with the VisAR, used the software/visor combination to navigate an 18-gauge needle/trocar through the series of burr holes to the target, resulting in 70 data points (15 for 4 users and 10 for 1 user). After each attempt the needle was left in the skull, supported by the ballistic gelatin, and a high-resolution CT was taken. Radial error and angle of error were determined using vector coordinates. Summary statistics were calculated individually and collectively. RESULTS The combined angle of error of was 2.30° ± 1.28°. The mean radial error for users was 3.62 ± 1.71 mm. The mean target depth was 85.41 mm. CONCLUSIONS The mean radial error and angle of error with the associated variance measures demonstrates that VisAR navigation may have utility for guiding a small needle to neural lesions, or targets within an accuracy of 3.62 mm. These values are sufficiently accurate for the navigation of many neurological procedures such as ventriculostomy.
We have shown that total body mass correlates remarkably well with both the Schneider method and Beam method of mass quantification. Furthermore, %BF calculated with the Schneider method and Beam method CT algorithms correlates remarkably well with ADP. The application of these CT algorithms have utility in further research to accurately stratify risk factors with periorgan, visceral, and subcutaneous types of adipose tissue, and has the potential for significant clinical application.
INTRODUCTION:The spine surgery market is moving away from open dissection to minimally invasive spine surgery (MISS). Precise operative navigation is imperative for MISS to achieve its potential. Guidance systems have been available for years, but adoption is limited by laborious set-up, costs and intraoperative imaging requirements. Herein is described the use of OpEyes-Augmented Reality (Novarad, American Fork, UT) for navigation and guidance of MISS for highly accurate insertion of pedicle screws.METHODS:A Microsoft HoloLens 2 (Microsoft, Redmond, WA) was used as the hardware platform for OpEyes-AR software. AprilTags, printed with CT visible ink, were either adhered to the skin, anchored to the iliac crests, or a vertebra. Following CT, the radiologist identified virtual pathways for ideal placement of pedicle screws for each vertebra.The annotated studies were wirelessly uploaded to the software/visor combination by viewing an encrypted QR code assigned by the pre-op system. The studies were registered to the AprilTags captured during CT. The virtual pathways were called by voice command for each vertebra and were used to establish skin entry point, trajectory, and depth with target bullseyes. Fluoroscopy was not required for navigation. Excella MIS hardware was used for placement of the screws into the pedicles of a donor torso (Innovasis, Salt Lake City, UT).RESULTS:Pedicle screws were instrumented through levels L5-T9 for a total of 15 screws. There were no breaches. Many of the thoracic pedicles were narrow with little or no tolerance. Guidance and navigation were performed solely with OpEyes-AR.CONCLUSION:OpEyes-AR is a tether-less, holographic visor and software combination offering the potential for precise navigation of MISS percutaneous insertion of pedicle screws with a nominal OR footprint and elimination of OR imaging.
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