Authors: Suresh Guttikonda, Maximilian Neidhardt, Vidas Raudonis, Alexander Schlaefer
Organizations: Institute of Medical Technology and Intelligent Sys., Hamburg University of Technology, Germany · Interdisciplinary Competence Center for Interface Research, Hamburg, Germany · SustAInLivWork Center of Excellence, Kaunas, Lithuania · Faculty of Electrical and Electronics Eng., Kaunas University of Technology, Lithuania
Optical coherence tomography (OCT) is a non-invasive volumetric imaging modality with high spatial and temporal resolution. For imaging larger tissue structures, OCT probes need to be moved to scan the respective area. For handheld scanning, stitching of the acquired OCT volumes requires overlap to register the images. For robotic scanning and stitching, a typical approach is to restrict the motion to translations, as this avoids a full hand-eye calibration, which is complicated by the small field of view of most OCT probes. However, stitching by registration or by translational scanning are limited when curved tissue surfaces need to be scanned. We propose a marker for full six-dimensional hand-eye calibration of a robot mounted OCT probe. We show that the calibration results in highly repeatable estimates of the transformation. Moreover, we evaluate robotic scanning of two phantom surfaces to demonstrate that the proposed calibration allows for consistent scanning of large, curved tissue surfaces. As the proposed approach is not relying on image registration, it does not suffer from a potential accumulation of errors along a scan path. We also illustrate the improvement compared to conventional 3D-translational robotic scanning.
Figures & tables
Figure 1: OCT Surface Scanning: An OCT scan head ( O ) and a RGB-D camera ( C ) are mounted to a robot ( G ). A custom calibration pattern ( CW ) is used to calibrate the camera and OCT scan head to the robot world coordinate frame ( RW ).
Figure 2: Pipeline to compile a calibration dataset.
Figure 3: Calibration Accuracy: The re-projection error vs (a) distinct OCT-EEF pose pairs acquired at ArUco marker ( j=17 ) (b) ArUco markers ( j=17 ) at various distances from center ArUco marker j=17 .
Figure 4: Spherical Phantom: (a) 6D Surface stitching. (b) 6D surface scanning (top) and corresponding 3D-Translation with artifacts (bottom). (c) Extracted surface points from cross sections in plane 6D scanning (blue) and 3D-translation (red).
Position (\text{,}\mathrm{mm})
Orientation (\text{,}\deg)
x
y
z
r
p
y
Hcg
μ
72.33
−62.51
85.3
68.76
70.41
67.71
σ
0.38
0.40
0.12
0.13
0.06
0.04
Hog
μ
140.28
−9.40
92.15
0.27
91.55
−0.42
σ
0.22
0.04
0.19
0.12
0.24
0.19
Table 1: Hand-in-Eye Calibration Results Camera (top row) and OCT scan head (bottom row)
Figure 5: Soft-Tissue Phantom: 6D and 3D-translation scans acquired on chicken tissue of OCT volumes and RGB-D data. The positions of two exemplary OCT volumes are indicated as A and B.
Robotics and Control Laboratory, University of British Columbia, Vancouver, BC, Canada · Department of Biomedical Engineering, National University of Singapore, Singapore · Division of Otolaryngology – Head and Neck Surgery, University of British Columbia, Vancouver, BC, Canada
Stanford Robotics Laboratory, Computer Science Department, Stanford University, Stanford, CA 94305 USA · Department of Radiology, School of Medicine, Stanford University, Stanford, CA 94305 USA