Positional and Orientational Accuracy of 3-D Ultrasound Navigation System on Vertebral Phantom Study

Abstract

Adolescent idiopathic scoliosis (AIS) is a 3-D spinal deformity that affects 1%–3% of youth. Severe cases require surgical intervention involving the insertion of pedicle screws near the spinal cord, making accurate placement imperative. Currently, surgeons use either CT-navigation methods to guide the placement of screws or free-hand methods. The free-hand method has higher breach rates; however, CT-navigation exposes children to sensitive ionizing radiation. A novel custom 3-D ultrasound (3DUS) system has been developed to provide accuracy benefits similar to traditional CT-navigation systems without exposing patients to ionizing radiation. This study evaluates the accuracy of the custom 3DUS guidance system for localizing 3-D reconstructions of vertebral phantoms and tracking handheld surgical tools in the surgical space. Tool tracking was evaluated with commercial motion tracking cameras using a 3-D-printed pointer device and a high-precision probe device. Experiments were performed on 3-D-printed vertebral phantoms to investigate the positional and orientational accuracy using a high precision reference grid. The 3-D-printed pointer device was shown to be inferior to the high-precision probe, finding positional accuracy of 1.1 ± 1.1 mm versus 0.7 ± 0.4 mm. The rotational accuracy was 0.0° ± 1.7°, which met the surgical objective. The 3DUS localization, which was also evaluated using the vertebral phantoms and reference grid, showed positional accuracy of 0.8 ± 0.6 mm, making it a promising image-guidance tool for scoliosis surgery.