Room: Osceola Ballroom C
Purpose: Minimally invasive focal ablations of liver tumors provide reduced patient complications and recovery times, but are currently associated with high local cancer recurrence. One source of error when performing therapy applicator guidance with 2D ultrasound (US) is the limited field-of-view, requiring mental reconstruction of the anatomy. Our solution to this limitation has been the development of a novel mechanically assisted 3D US imaging and guidance system capable of providing geometrically variable images.
Methods: A three-motor mechanical mover was designed to provide adjustable linear, tilt, and hybrid geometries for variable 3D US fields-of-views. This mover can manipulate any clinically available 2D US transducer via transducer-specific 3D-printed holders to guide therapy applicator insertions intraoperatively. This mover is held by a portable counterbalanced mechanical system that features foot-released electromagnetic brakes and encoders to track the position of the transducer. Optical tracking was performed with a mounted stylus to evaluate mechanical motions of the scanner. A string phantom with known dimensions was imaged and manually measured to validate image reconstruction geometry and preliminary images were acquired of a volunteer to assess clinical applicability.
Results: Optical tracking of the 3D scanner resulted in mean linear and angular motion errors of 0.21 mm (0.20%) and 0.23Â° (0.52%), respectively. Mean linear image measurement errors were <3% on the string phantom and human volunteer images were clinically applicable as the relevant anatomy could be visualized such as the portal vein bifurcation, gallbladder, and kidney.
Conclusion: The proposed mechanically assisted 3D US system for focal liver ablation performs image acquisition accurately and the three-motor mover assembly allows for control over scan geometries to accommodate clinical anatomical variation. Current work is focused on mapping and correcting for the error in the tracking system encoders to calibrate the tracking system prior to a simulated image-guided phantom procedure.
Funding Support, Disclosures, and Conflict of Interest: The authors would like to acknowledge funding support from the Canadian Institutes of Health Research (CIHR), Natural Sciences and Engineering Research Council (NSERC), and the Ontario Institute for Cancer Research (OICR).