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Ultrahigh-resolution K-edge imaging for guidance of microrobots in minimally invasive interventions: A feasibility
Arnaud R Brian-Choux1, Thomas Wesley Holmes1, Zhye Yin2
1Department of Biomedical Engineering, Georgia Institute of Technology, Department of Radiology and Imaging Sciences, Winship Cancer Institute, Emory University, Atlanta, Georgia, USA.
Background:
Photon-counting detector (PCD) CT offers enhanced spatial resolution, improved image contrast, reduced radiation dose, and material differentiation through K-edge imaging. These features may be of value for guiding microrobots and surgical instruments during minimally invasive brain surgery.
Purpose:
This study evaluates the feasibility of using K-edge imaging with deep silicon (dSi) PCD CT to estimate the pose and location of microrobots within the human head, utilizing materials like neodymium (Nd) and tungsten (W) with distinct K-edge energies.
Methods:
A micro-driller robot with a cubic Nd magnet (K-edge energy = 43.5 keV) and a 3D-printed drill bit was used. W (K-edge energy = 69.5 keV) was added to aid in orientation detection. These materials were positioned at distances of 0-1 mm within a 3D-printed setup and placed in a human skull filled with ballistic gel, alongside other metallic parts. The setup was scanned using a prototype dSi CT scanner with eight energy bins. Scanning parameters included 120 kVp, 300 mAs, 0.5 s rotation time, and 4-cm z-collimation.
Results:
Nd and W components were distinguishable, with Nd showing higher contrast in low-energy virtual monoenergetic images (VMIs) and W being more radiopaque in higher VMIs. The signal-to-noise ratios (SNR) at 70 keV and 1-mm distance were 31.0 for Nd and 132.7 for W. The error in estimating the distance between components (ΔL) ranged from 82 to 263 µm comparable to one image voxel.
Conclusions:
Deep silicon PCD-CT with K-edge imaging successfully differentiated microrobot components in a human head phantom, indicating its potential for precision image-guided robotic surgery. Further studies are needed to optimize radiation doses for clinical use.
